WO2025259834A1

WO2025259834A1 - Power save mode operation for beamformed data transmission

Info

Publication number: WO2025259834A1
Application number: PCT/US2025/033281
Authority: WO
Inventors: Jiayi Zhang; Leonardo Alisasis LANANTE; Esmael Hejazi Dinan; Jeongki Kim; Serhat Erkucuk; Tuncer Baykas
Original assignee: Ofinno LLC
Current assignee: Ofinno LLC
Priority date: 2024-06-13
Filing date: 2025-06-12
Publication date: 2025-12-18
Anticipated expiration: 2026-12-13

Abstract

A first access point (AP) transmits to a first station (STA), while the first STA operates in a power save (PS) mode, a first frame requesting that the first STA operate, during a first time period, in a first power state/mode of the PS mode, where the first time period comprises a sounding sequence by the first AP and a second AP. The first AP transmits to the first STA, during the first time period, a null data physical layer protocol data unit (NDP) for use by the first STA to generate feedback to the first AP, receives, from the first STA and during the first time period, a second frame comprising the feedback; and transmits a physical protocol data unit (PPDU) to the first STA.

Description

TITLE

POWER SAVE MODE OPERATION FOR BEAMFORMED DATA TRANSMISSION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63/659,371 , filed June 13,

2024, which is hereby incorporated by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Examples of several of the various embodiments of the present disclosure are described herein with reference to the drawings.

[0003] FIG. 1 illustrates example wireless communication networks in which embodiments of the present disclosure may be implemented.

[0004] FIG. 2 is a block diagram illustrating example implementations of a station (STA) and an access point (AP).

[0005] FIG. 3 illustrates an example medium access control (MAC) frame format.

[0006] FIG. 4 illustrates an example management frame which may be used as an action frame.

[0007] FIG. 5 illustrates an example control frame which may be used as a trigger frame.

[0008] FIG. 6 illustrates an example data frame which may be used as a Quality of Service (QoS) null frame.

[0009] FIG. 7 illustrates an example format of a physical layer (PHY) protocol data unit (PPDU).

[0010] FIG. 8 illustrates a non-High Throughput (non-HT) Physical Layer Protocol Data Unit (PPDU), a High Throughput (HT) mixed PPDU, and a Very High Throughput (VHT) PPDU.

[0011] FIG. 9 illustrates a High Efficiency (HE) Single User (SU) PPDU, an HE Multi-User (MU) PPDU, and an HE Extended Range (ER) SU PPDU.

[0012] FIG. 10 illustrates an Extremely High Throughput (EHT) Multi-user (MU) PPDU.

[0013] FIG. 11 illustrates an example multi-user request-to-send (MU-RTS) trigger frame.

[0014] FIG. 12 illustrates an example block acknowledgment request (BlockAckReq or BAR) frame.

[0015] FIG. 13 illustrates an example of a power save (PS) mode.

[0016] FIG. 14 illustrates an example of an AP implementation of the PS mode illustrated in FIG. 19.

[0017] FIG. 15 illustrates an EHT sounding null data PPDU (NDP).

[0018] FIG. 16 illustrates an example null data PPDU (NDP) announcement (NDPA) frame format.

[0019] FIG. 17 illustrates an example STA info field.

[0020] FIG. 18 illustrates an example enhanced high throughput (EHT) compressed beamforming/channel quality indication (CQI) frame.

[0021] FIG. 19 illustrates an example of a non-trigger-based (non-TB) sounding sequence.

[0022] FIG. 20 illustrates an example of a trigger based (TB) sounding sequence.

[0023] FIG. 21 illustrates an example that highlights a problem that may arise in association with the PS mode illustrated in FIG. 14. [0024] FIG. 22 is an example that illustrates a PS mode operation for beamformed data transmission according to an embodiment.

[0025] FIG. 23 is an example that illustrates a PS mode operation for beamformed data transmission according to an embodiment.

[0026] FIG. 24 is an example that illustrates a PS mode operation for beamformed data transmission according to an embodiment.

[0027] FIG. 25 is an example that illustrates a PS mode operation for beamformed data transmission according to an embodiment.

[0028] FIG. 26 illustrates an example control frame which may be used according to embodiment.

[0029] FIG. 27 illustrates an example process according to an embodiment of the present disclosure.

[0030] FIG. 28 illustrates an example process according to an embodiment of the present disclosure.

[0031] FIG. 29 illustrates an example process according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0032] In the present disclosure, various embodiments are presented as examples of how the disclosed techniques may be implemented and/or how the disclosed techniques may be practiced in environments and scenarios. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the scope. After reading the description, it will be apparent to one skilled in the relevant art how to implement alternative embodiments. The present embodiments may not be limited by any of the described exemplary embodiments. The embodiments of the present disclosure will be described with reference to the accompanying drawings. Limitations, features, and/or elements from the disclosed example embodiments may be combined to create further embodiments within the scope of the disclosure. Any figures which highlight the functionality and advantages, are presented for example purposes only. The disclosed architecture is sufficiently flexible and configurable, such that it may be utilized in ways other than that shown. For example, the actions listed in any flowchart may be re-ordered or only optionally used in some embodiments.

[0033] Embodiments may be configured to operate as needed. The disclosed mechanism may be performed when certain criteria are met, for example, in a station, an access point, a radio environment, a network, a combination of the above, and/or the like. Example criteria may be based, at least in part, on for example, wireless device or network node configurations, traffic load, initial system set up, packet sizes, traffic characteristics, a combination of the above, and/or the like. When the one or more criteria are met, various example embodiments may be applied. Therefore, it may be possible to implement example embodiments that selectively implement disclosed protocols.

[0034] In this disclosure, “a” and "an” and similar phrases are to be interpreted as “at least one” and “one or more.” Similarly, any term that ends with the suffix “(s)” is to be interpreted as “at least one” and “one or more.” In this disclosure, the term “may” is to be interpreted as “may, for example.” In other words, the term "may’’ is indicative that the phrase following the term “may” is an example of one of a multitude of suitable possibilities that may, or may not, be employed by one or more of the various embodiments. The terms “comprises” and “consists of’, as used herein, enumerate one or more components of the element being described. The term “comprises” is interchangeable with “includes" and does not exclude unenumerated components from being included in the element being described. By contrast, “consists of' provides a complete enumeration of the one or more components of the element being described. The term “based on”, as used herein, may be interpreted as “based at least in part on” rather than, for example, “based solely on”. The term “and/or” as used herein represents any possible combination of enumerated 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.

[0035] If A and B are sets and every element of A is an element of B, A is called a subset of B. In this specification, only non-empty sets and subsets are considered. For example, possible subsets of B = {STA1 , STA2} are: {STA1 }, {STA2}, and {STA1 , STA2}. The phrase “based on” (or equally “based at least on”) is indicative that the phrase following the term “based on” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “in response to” (or equally “in response at least to”) is indicative that the phrase following the phrase “in response to” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “depending on” (or equally “depending at least to”) is indicative that the phrase following the phrase “depending on" is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “employing/using” (or equally “employing/using at least”) is indicative that the phrase following the phrase “employing/using” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments.

[0036] The term configured may relate to the capacity of a device whether the device is in an operational or non-operational state. Configured may refer to specific settings in a device that effect the operational characteristics of the device whether the device is in an operational or non-operational state. In other words, the hardware, software, firmware, registers, memory values, and/or the like may be “configured” within a device, whether the device is in an operational or nonoperational state, to provide the device with specific characteristics. Terms such as “a control message to cause in a device” may mean that a control message has parameters that may be used to configure specific characteristics or may be used to implement certain actions in the device, whether the device is in an operational or non-operational state.

[0037] In this disclosure, parameters (or equally called, fields, or Information elements: IBs) may comprise one or more information objects, and an information object may comprise one or more other objects. For example, if parameter (IE) N comprises parameter (IE) M, and parameter (IE) M comprises parameter (IE) K, and parameter (IE) K comprises parameter (information element) J. Then, for example, N comprises K, and N comprises J. In an example embodiment, when one or more messages/frames comprise a plurality of parameters, it implies that a parameter in the plurality of parameters is in at least one of the one or more messages/frames but does not have to be in each of the one or more messages/frames.

[0038] Many features presented are described as being optional through the use of “may” or the use of parentheses. For the sake of brevity and legibility, the present disclosure does not explicitly recite each and every permutation that may be obtained by choosing from the set of optional features. The present disclosure is to be interpreted as explicitly disclosing all such permutations. For example, a system described as having three optional features may be embodied in seven ways, namely with just one of the three possible features, with any two of the three possible features or with three of the three possible features.

[0039] Many of the elements described in the disclosed embodiments may be implemented as modules. A module is defined here as an element that performs a defined function and has a defined interface to other elements. The modules described in this disclosure may be implemented in hardware, software in combination with hardware, firmware, wetware (e.g., hardware with a biological element) or a combination thereof, which may be behaviorally equivalent. For example, modules may be implemented as a software routine written in a computer language configured to be executed by a hardware machine (such as C, C++, Fortran, Java, Basic, Matlab or the like) or a modeling/simulation program such as Simulink, Stateflow, GNU Octave, or LabVIEWMathScript. It may be possible to implement modules using physical hardware that incorporates discrete or programmable analog, digital and/or quantum hardware. Examples of programmable hardware comprise 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, C++ or the like. FPGAs, ASICs and CPLDs are often programmed using hardware description languages (HDL) such as VHSIC hardware description language (VHDL) or Verilog that configure connections between internal hardware modules with lesser functionality on a programmable device. The mentioned technologies are often used in combination to achieve the result of a functional module.

[0040] FIG. 1 illustrates example wireless communication networks in which embodiments of the present disclosure may be implemented.

[0041] As shown in FIG. 1 , the example wireless communication networks may include an Institute of Electrical and Electronic Engineers (IEEE) 802.11 (WLAN) infra-structure network 102. WLAN infra-structure network 102 may include one or more basic service sets (BSSs) 1 10 and 120 and a distribution system (DS) 130

[0042] BSS 110-1 and 110-2 each includes 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 an AP 104-1 and a STA 106-1 , and BSS 1 10-2 includes an AP 104-2 and STAs 106-2 and 106-3. The AP and the at least one STA in a BSS perform an association procedure to communicate with each other. [0043] DS 130 may be configured to connect BSS 110-1 and BSS 110-2. As such, DS 130 may enable an extended service set (ESS) 150. Within ESS 150, APs 104-1 and 104-2 are connected via DS 130and may have the same service set identification (SSID).

[0044] WLAN infra-structure network 102 may be coupled to one or more external networks. For example, as shown in FIG. 1 , WLAN infra-structure network 102 may be connected to another network 108 (e.g., 802.X) via a portal 140. Portal 140 may function as a bridge connecting DS 130 of WLAN infra-structure network 102 with the other network 108.

[0045] The example wireless communication networks illustrated in FIG. 1 may further include one or more ad-hoc networks or independent BSSs (IBSSs). An ad-hoc network or IBSS is a network that includes a plurality of STAs that are within communication range of each other. The plurality of STAs are configured so that they may communicate with each other using direct peer-to-peer communication (i.e., not via an AP). [0046] 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, STAs within an IBSS are managed in a distributed manner. STAs forming an IBSS may be fixed or mobile.

[0047] A STA as a predetermined functional medium may include a medium access control (MAC) layer that complies with an IEEE 802.11 standard. A physical layer interface for a radio medium may be used among the APs and the non-AP stations (STAs). The STA may also be referred to using various other terms, including mobile terminal, wireless device, wireless transmit/receive unit (WTRU), user equipment (UE), mobile station (MS), mobile subscriber unit, or user. For example, the term “user" may be used to denote a STA participating in uplink Multi-user Multiple Input, Multiple Output (MU MIMO) and/or uplink Orthogonal Frequency Division Multiple Access (OFDMA) transmission.

[0048] A physical layer (PHY) protocol data unit (PPDU) may 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 may 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 may be used by a receiving device to decode the subsequent data in the PSDU. In instances in which PPDUs are transmitted over a bonded channel (channel formed through channel bonding), the preamble fields may be duplicated and transmitted in each of the multiple component channels. The PHY preamble may include both a legacy portion (or “legacy preamble”) and a non-legacy portion (or “non-legacy preamble”). The legacy preamble may be used for packet detection, automatic gain control and channel estimation, among other uses. The legacy preamble also may generally be used to maintain compatibility with legacy devices. The format of, coding of, and information provided in the non-legacy portion of the preamble is based on the particular IEEE 802.1 1 protocol to be used to transmit the payload. [0049] A frequency band may include one or more sub-bands or frequency channels. For example, PPDUs conforming to the IEEE 802.11 n, 802.1 1ac, 802.11 ax and/or 802.11 be standard amendments may be transmitted over the 2.4 GHz, 5 GHz, and/or 6 GHz bands, each of which may be divided into multiple 20 MHz channels. The PPDUs may be transmitted over a physical channel having a minimum bandwidth of 20 MHz. Larger channels may be formed through channel bonding. For example, PPDUs may be transmitted over physical channels having bandwidths of 40 MHz, 80 MHz, 160 MHz, or 520 MHz by bonding together multiple 20 MHz channels.

[0050] FIG. 2 is a block diagram illustrating example implementations of a STA 210 and an 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 operatively connected to memory 230/280 and/or to transceiver 240/290.

[0051] Processor 220/270 may implement functions of the PHY layer, the MAC layer, and/or the logical link control (LLC) layer of the corresponding device (STA 210 or AP 260). Processor 220/270 may include one or more processors and/or one or more controllers. The one or more processors and/or one or more controllers may comprise, for example, a general-purpose processor, a digital signal processor (DSP), a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a logic circuit, or a chipset, for example.

[0052] Memory 230/280 may include a read-only memory (ROM), a random-access memory (RAM), a flash memory, a memory card, a storage medium, and/or other storage unit. Memory 230/280 may comprise one or more non-transitory computer readable mediums. Memory 230/280 may store computer program instructions or code that may be executed by processor 220/270 to carry out one or more of the operations/embodiments discussed in the present application. Memory 230/280 may be implemented (or positioned) within processor 220/270 or external to processor 220/270. Memory 230/280 may be operatively connected to processor 220/270 via various means known in the art.

[0053] Transceiver 240/290 may be configured to transmit/receive radio signals. In an embodiment, transceiver 240/290 may implement a PHY layer of the corresponding device (STA 210 or AP 260). In an embodiment, STA 210 and/or AP 260 may be a multi-link device (MLD), that is a device capable of operating over multiple links as defined by the IEEE 802.11 standard. As such, STA 210 and/or AP 260 may each implement multiple PHY layers. The multiple PHY layers may be implemented using one or more of transceivers 240/290

[0054] FIG. 3 illustrates an example format of a MAC frame 300. In operation, a STA may construct a subset of MAC frames for transmission and may decode a subset of received MAC frames upon validation. The particular subsets of frames that a STA may construct and/or decode may be determined by the functions supported by the STA. A STA may validate a received MAC frame using the frame check sequence (FCS) contained in the frame and may interpret certain fields from the MAC headers of all frames. [0055] As shown in FIG. 3, MAC frame 300 includes a MAC header, a variable length frame body, and a frame check sequence (FCS).

[0056] The MAC header includes a frame control field, an optional duration/ID field (not in PS-Poll frames), address fields, an optional sequence control field, an optional QoS control field (only in QoS Data frames), and an optional high throughput (HT) control field (only in +HTC frames).

[0057] The frame control field includes the following subfields: protocol version, type, subtype, To DS, From DS, more fragments, retry, power management, more data, protected frame, and high throughput control (+HTC).

[0058] The protocol version subfield is invariant in size and placement across all revisions of the IEEE 802.1 1 standard. The value of the protocol version subfield is 0 for MAC frames.

[0059] The type and subtype subfields together identify the function of the MAC frame. There are three frame types: control, data, and management. Each of the frame types has several defined subtypes. Bits within the subtype subfield are used to indicate a specific modification of the basic data frame (subtype 0). For example, in data frames, 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 contains a QoS control field in its MAC header. The second MSB of the subtype field, bit 6 (B6) of the frame control field, when set to 1 in data subtypes, indicates a data frame that contains no frame body field.

[0060] The To DS subfield indicates whether a data frame is destined to the DS. The From DS subfield indicates whether a data frame originates from the DS.

[0061] The more fragments subfield is set to 1 in all data or management frames that have another fragment to follow of the MAC service data unit (MSDU) or MAC management protocol data unit (MMPDU) carried by the MAC frame. It is set to 0 in all other frames in which the more fragments subfield is present.

[0062] The retry subfield is set to 1 in any data or management frame that is a retransmission of an earlier frame. It is set to 0 in all other frames in which the retry subfield is present. A receiving STA uses this indication to aid it in the process of eliminating duplicate frames. These rules do not apply for frames sent by a STA under a block agreement.

[0063] The power management subfield is used to indicate the power management mode of a STA.

[0064] The More Data subfield indicates to a STA in power save (PS) mode that bufferable units (BUs) are buffered for that STA at the AP. The more data subfield is valid in individually addressed data or management frames transmitted by an AP to a STA in PS mode. The more data subfield is set to 1 to indicate that at least one additional buffered BU is present for the STA.

[0065] The protected frame subfield is set to 1 if the frame body field contains information that has been processed by a cryptographic encapsulation algorithm. [0066] The +HTC subfield indicates that MAC frame 300 contains an HT control field. A frame that contains the HT Control field is referred to as a +HTC frame. A Control Wrapper frame is a +HTC frame.

[0067] The duration/ID field of the MAC header indicates various contents depending on frame type and subtype and the QoS capabilities of the sending STA. For example, in control frames of the power save poll (PS-Poll) subtype, the duration/ID field carries an association identifier (AID) of the STA that transmitted the frame in the 14 least significant bits (LSB), and the 2 most significant bits (MSB) are both set to 1 . In other frames sent by STAs, the duration/ID field contains a duration value (in microseconds) which is used by a recipient to update a network allocation vector (NAV). The NAV is a counter that indicates to a STA an amount of time during which it must defer from accessing the shared medium.

[0068] There can be up to four address fields in the format of MAC frame 300. 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). Certain frames might not contain some of the address fields. Certain address field usage may be specified by the relative position of the address field (1-4) within the MAC header, independent of the type of address present in that field. Specifically, the address 1 field always identifies the intended receiver(s) of the frame, and the address 2 field, where present, always identifies the transmitter of the frame.

[0069] The sequence control field includes two subfields, a sequence number subfield and a fragment number subfield. The sequence number subfield in data frames indicates the sequence number of the MSDU (if not in an Aggregated MSDU (A-MSDU)) or A-MSDU. The sequence number subfield in management frames indicates the sequence number of the frame. The fragment number subfield indicates the number of each fragment of an MSDU or MMPDU. The fragment number is set to 0 in the first or only fragment of an MSDU or MMPDU and is incremented by one 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 in an MPDU containing an MSDU or MMPDU that is not fragmented. The fragment number remains constant in all retransmissions of the fragment.

[0070] The QoS control field identifies the traffic category (TC) or traffic stream (TS) to which MAC frame 300 belongs. The QoS control field may also indicate various other QoS related, A-MSDU related, and mesh- related information about the frame. This information can vary by frame type, frame subtype, and type of transmitting STA. The QoS control field is present in all data frames in which the QoS subfield of the subtype subfield is equal to 1.

[0071] The HT control field is present in QoS data, QoS null, and management frames as determined by the +HTC subfield of the frame control field. The control frame subtype for which HT control field is present is the control wrapper frame. A control frame that is described as +HTC (e.g., a request to send (RTS)+HTC, clear to send (CTS)+HTC, block acknowledgment (BlockAck)+HTC or block acknowledgment request (BlockAckReq)+HTC frame) implies the use of the control wrapper frame to carry that control frame. [0072] The frame body field is a variable length field that contains information specific to individual frame types and subtypes. It may include one or more MSDUs or MMPDUs. The minimum length of the frame body is 0 octets

[0073] The FCS field contains a 32-bit Cyclic Redundancy Check (CRC) code. The FCS field value is calculated over all of the fields of the MAC header and the frame body field.

[0074] FIG. 4 illustrates an example management frame 400 which may be used as an action frame. In an example, management frame 400 includes a MAC header, a variable length frame body, and a frame check sequence (FCS). The MAC header includes a frame control field, a duration field, an address 1 field, an address 2 field, an address 3 field, a sequence control field, and an optional HT control field. The presence of the HT control field is determined by the setting of a +HTC subfield of the frame control field.

[0075] As shown in FIG. 4, when used as an action frame, the frame body of management frame includes an action field, vendor specific elements, management message integrity code element (MME), message integrity code (MIC), and an authenticated mesh peering exchange element.

[0076] The action field includes a category field and an action details field. The action field provides a mechanism for specifying extended management actions. The category field indicates a category of the action frame. The action details field contains the details of the action requested by the action frame. For example, the action frame may be a public action frame. As shown in FIG. 4, in the public action frame format, the action details field includes a public action field, in the octet immediately after the category field, followed by a variable length public action details field.

[0077] One or more vendor specific elements are optionally present. These elements are absent when the category subfield of the Action field is vendor-specific.

[0078] The MME is present when management frame protection is negotiated, the frame is a group addressed robust Action frame, and (MBSS only) the category of the action frame does not support group addressed privacy as indicated by category values; otherwise not present.

[0079] The MIC element is present in a self-protected action frame if a shared pairwise master key (PMK) exists between the sender and recipient of this frame; otherwise not present.

[0080] The authenticated mesh peering exchange element is present in a self-protected action frame if a shared PMK exists between the sender and recipient of this frame; otherwise not present.

[0081] FIG. 5 illustrates an example format of a trigger frame 500. Trigger frame 500 may be used by an AP to allocate resources for and solicit one or more TB PPDU transmissions from one or more STAs. Trigger frame 500 may also carry other information required by a responding STA to transmit a TB PPDU to the AP. [0082] As shown in FIG. 5, trigger frame 500 includes a Frame Control field, a Duration field, a receiver address (RA) field, a transmitter address (TA) field, a Common Info field, a User Info List field, a Padding field, and an FCS field. [0083] The Frame Control field includes the following subfields: protocol version, type, subtype, To DS, From DS, more fragments, retry, power management, more data, protected frame, and +HTC.

[0084] The Duration field indicates various contents depending on frame type and subtype and the QoS capabilities of the sending STA. For example, in control frames of the power save poll (PS-Poll) subtype, the Duration field carries an association identifier (AID) of the STA that transmitted the frame in the 14 least significant bits (LSB), and the 2 most significant bits (MSB) are both set to 1 . In other frames sent by STAs, the Duration field contains a duration value (in microseconds) which is used by a recipient to update a network allocation vector (NAV).

[0085] The RA field is the address of the STA that is intended to receive the incoming transmission from the transmitting station. The TA field is the address of the STA transmitting trigger frame 500 if trigger frame 500 is addressed to STAs that belong to a single BSS. The TA field is the transmitted BSSID if trigger frame 500 is addressed to STAs from at least two different BSSs of the multiple BSSID set.

[0086] The Common Info field specifies a trigger frame type of trigger frame 500, a transmit power of trigger frame 500 in dBm, and several key parameters of a TB PPDU that is transmitted by a STA in response to trigger frame 500. The trigger frame type of a trigger frame used by an AP to receive QoS data using UL MU operation is referred to as a basic trigger frame. A non-EHT non-AP HE STA interprets the Common Info field as HE variant. A non-AP EHT STA interprets the Common Info field as HE variant if B54 and B55 in the Common Info field are equal to 1 ; and interprets the Common Info field as EHT variant otherwise. The HE variant Common Info field and the EHT variant Common Info field use the same encoding method for the Trigger Type, UL Length, More TF, CS Required, LDPC Extra Symbol Segment, AP TX Power, Pre-FEC Padding Factor, PE Disambiguity, and Trigger Dependent Common Info subfields.

[0087] The User Info List field contains zero or more User Info fields. There are three variants for the User Info field, which are the Special User Info field, the EHT variant User Info field, and the HE variant User Info field.

[0088] The Special User Info field is a User Info field that does not carry the user specific information but carries the extended common information not provided in the Common Info field. If the Special User Info field is included in the Trigger frame, then the Special User Info Field Flag subfield of the EHT variant Common Info field is set to 0, otherwise it is set to 1 . The Special User Info field is identified by an AID12 value of 2007 and is optionally present in a Trigger frame that is generated by an EHT AP. The Special User Info field, if present, is located immediately after the Common Info field of the Trigger frame and carries information for the U-SIG field of a solicited EHT TB PPDU. The PHY Version Identifier subfield indicates the PHY version of the solicited TB PPDU that is not an HE TB PPDU. The PHY Version Identifier subfield is set to 0 for EHT. Other values from 1 to 7 are reserved. The UL Bandwidth (BW) Extension subfield, together with the UL BW subfield in the Common Info field, indicates the bandwidth of the solicited TB PPDU from the addressed EHT STA (i.e., the bandwidth in the U-SIG field of the EHT TB PPDU). The EHT Spatial Reuse n subfield carries the values to be included in the corresponding Spatial Reuse n subfield in the U-SIG field of the EHT TB PPDU. The U-SIG Disregard And Validate subfield carries the values to be included in the Disregard and Validate subfields of the U-SIG field of the solicited EHT TB PPDUs. The presence and length of the Trigger Dependent User Info subfield in the Special User Info field depends on the variant of the Trigger frame. [0089] The EHT variant User Info field contains a User Info field per STA addressed in trigger frame 500. The per STA User Info field includes, among others, an AID12 subfield, an RU Allocation subfield, a UL PEC Coding Type subfield, a UL EHT-MCS subfield, a Reserved subfield, a Spatial Stream (SS) Allocation/RA- RU information subfield, a UL Target Receive Power subfield, and a Power Save (PS) 160 subfield to be used by a STA in a TB PPDU transmitted in response to trigger frame 500, and a Trigger Dependent User Info subfield. The RU Allocation subfield in an EHT variant User Info field in a Trigger frame that is not an MU-RTS Trigger frame, along with the UL BW subfield in the Common Info field, the UL BW Extension subfield in the Special User Info field, and the PS160 subfield in the EHT variant User Info field, identifies the size and the location of the RU or MRU. The values of PS160 subfield and B0 of RU Allocation subfield indicate the 80 MHz frequency subblock in which the RU or MRU is located for 26-tone RU, 52-tone RU, 106- tone RU, 242-tone RU, 484-tone RU, 996-tone RU, 52+26-tone RU, and 106+26-tone RU. The values of PS160 subfield indicates the 160 MHz segment in which the RU or MRU is located for 2 996-tone RU, 996+484-tone MRU, and 996+484+242-tone MRU. The UL FEC Coding Type subfield of the User Info field indicates the code type of the solicited EHT TB PPDU. The UL FEC Coding Type subfield is set to 0 to indicate BCC and set to 1 to indicate LDPC. The UL EHT-MCS subfield of the User Info field indicates the EHT-MCS of the solicited EHT TB PPDU. The SS Allocation subfield of the EHT variant User Info field indicates the spatial streams of the solicited EHT TB PPDU. The UL Target Receive Power subfield indicates the expected receive signal power, measured at the AP's antenna connector and averaged over the antennas, for the EHT portion of the EHT TB PPDU transmitted on the assigned RU. The Trigger Dependent User Info subfield can be used by an AP to specify a preferred access category (AC) per STA. The preferred AC sets the minimum priority AC traffic that can be sent by a participating STA. The AP determines the list of participating STAs, along with the BW, MCS, RU allocation, SS allocation, Tx power, preferred AC, and maximum duration of the TB PPDU per participating STA. The RA-RU Information subfield is reserved in the EHT variant User Info field.

[0090] The Padding field is optionally present in management frame 400 to extend the frame length to give recipient STAs enough time to prepare a response for transmission one SIFS after the frame is received. The Padding field, if present, is at least two octets in length and is set to all 1s.

[0091] The FCS field is used by a STA to validate a received frame and to interpret certain fields from the MAC headers of a frame.

[0092] FIG. 6 illustrates an example data frame 600 which may be used as a QoS null frame. A QoS null frame refers to a QoS data frame with an empty frame body. QoS null frame includes a QoS control field and an optional HT control field which may contain a buffer status report (BSR) control subfield. A QoS null frame indicating buffer status information may be transmitted by a STA to an AP.

[0093] The QoS control field may include a traffic identifier (TID) subfield, an acknowledgment (Ack) policy indicator subfield, and a queue size subfield (or a transmission opportunity (TXOP) duration requested subfield).

[0094] The TID subfield identifies the TC or TS of traffic for which a TXOP is being requested, through the setting of the TXOP duration requested or queue size subfield. The encoding of the TID subfield depends on the access policy (e.g., Allowed value 0 to 7 for enhanced distributed channel access (EDCA) access policy to identify user priority for either TC or TS).

[0095] The ack policy indicator subfield, together with other information, identifies the Ack policy followed upon delivery of the MPDU (e.g., normal Ack, implicit block Ack request, no Ack, block Ack, etc.)

[0096] The queue size subfield is an 8-bit field that indicates the amount of buffered traffic for a given TC or TS at the STA for transmission to the AP identified by the receiver address of the frame containing the subfield. The queue size subfield is present in QoS null frames sent by a STA when bit 4 of the QoS control field is set to 1. The AP may use information contained in the queue size subfield to determine the TXOP duration assigned to the STA or to determine the uplink (UL) resources assigned to the STA.

[0097] In a frame sent 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 approximate total size, rounded up to the nearest multiple of 256 octets and expressed in units of 256 octets, of all MSDUs and A-MSDUs buffered at the STA (excluding the MSDU or A-MSDU contained in the present QoS Data frame) in the delivery queue used for MSDUs and A-MSDUs with TID values equal to the value indicated in the TID subfield of the QoS Control field.

A queue size value of 0 is used solely to indicate the absence of any buffered traffic in the queue used for the specified TID.

A queue size value of 254 is used for all sizes greater than 64 768 octets.

A queue size value of 255 is used to indicate an unspecified or unknown size.

[0098] In a frame sent by an HE STA to an HE AP, the following rules may apply to the queue size value.

[0099] The queue size value, QS, is the approximate total size in octets, of all MSDUs and A-MSDUs buffered at the STA (including the MSDUs or A-MSDUs contained in the same PSDU as the frame containing the queue size subfield) in the delivery queue used for MSDUs and A-MSDUs with TID values equal to the value indicated in the TID subfield of the QoS control field.

[0100] The queue size subfield includes a scaling factor subfield in bits B14-B15 of the QoS control field and an unsealed value, UV, in bits B8-B13 of the QoS control field. The scaling factor subfield provides the scaling factor, SF. [0101] A STA obtains the queue size, QS, from a received QoS control field, which contains a scaling factor, SF, and an unsealed value, UV, as follows:

QS =

16 *UV, if SF is equal to 0;

1024 + 256 x UV, if SF is equal to 1 ;

17 408 + 2048 x W, if SF is equal to 2;

148 480 + 32 768 x UV, if SF is equal to 3 and UV is less than 62;

> 2 147 328, if SF equal to is 3 and UV is equal to 62;

Unspecified or Unknown, if SF is equal to 3 and UV is equal to 63.

[0102] The TXOP duration requested subfield, which may be included instead of the queue size subfield, indicates the duration, in units of 32 microseconds (us), that the sending STA determines it needs for its next TXOP for the specified TID. The TXOP duration requested 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 requested subfield is set to a nonzero value to indicate a requested TXOP duration in the range of 32 us to 8160 us in increments of 32 us.

[0103] The HT control field may include an aggregated control (A-Control) subfield. The A-Control subfield may include a control list subfield including one or more control subfields.

[0104] The control subfield may be a BSR control subfield, which 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 a queue size all subfield of the HT control field.

[0105] The ACI bitmap subfield indicates the access categories for which 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 all subfield, and set to 0 otherwise, except that if the ACI bitmap subfield is 0 and the delta TID subfield is 3, then the buffer status of all 8 TIDs is included.

[0106] The delta TID subfield, together with the values of the ACI bitmap subfield, indicate the number of TIDs for which the STA is reporting the buffer status.

[0107] The ACI high subfield indicates the ACI of the AC for which the BSR is indicated in the queue size high subfield. The ACI to AC mapping is defined as ACI value 0 mapping to AC_BE, ACI value 1 mapping to AC_BK, ACI value 2 mapping to AC_VI, and ACI value 3 mapping to AC_VO.

[0108] The scaling factor subfield indicates the unit SF, in octets, of the queue size high and queue size all subfields. [0109] The queue size high subfield indicates the amount of buffered traffic, in units of SF octets, for the AC identified by the ACI high subfield, that is intended for the STA identified by the receiver address of the frame containing the BSR control subfield.

[0110] The queue size all subfield indicates the amount of buffered traffic, in units of SF octets, for all ACs identified by the ACI Bitmap subfield, that is intended for the STA identified by the receiver address of the frame containing the BSR control subfield.

[0111] The queue size values in the queue size high and queue size all subfields are the total sizes, rounded up to the nearest multiple of SF octets, of all MSDUs and A-MSDUs buffered at the STA (including the MSDUs or A-MSDUs contained in the same PSDU as the frame containing the BSR control subfield) in delivery queues used for MSDUs and A-MSDUs associated with AC(s) that are specified in the ACI high and ACI bitmap subfields, respectively.

[0112] A queue size value of 254 in the queue size high and queue size all subfields indicates that the amount of buffered traffic is greater than 254 x SF octets. A queue size value of 255 in the queue size high and queue size all subfields indicates that the amount of buffered traffic is an unspecified or unknown size. The queue size value of QoS data frames containing fragments may remain constant even if the amount of queued traffic changes as successive fragments are transmitted.

[0113] MAC service provides peer entities with the ability to exchange MSDUs. To support this service, a local MAC uses the underlying PHY-level service to transport the MSDUs to a peer MAC entity. Such asynchronous MSDU transport is performed on a connectionless basis.

[0114] FIG. 7 illustrates an example format of a PPDU. As shown, the PPDU may include a PHY preamble, a PHY header, a PSDU, and tail and padding bits.

[0115] The PSDU may include one or more MPDUs, such as a QoS data frame, an MMPDU, a MAC control frame, or a QoS null frame. In the case of an MPDU carrying a QoS data frame, the frame body of the MPDU may include a MSDU or an A-MSDU.

[0116] By default, MSDU transport is on a best-effort basis. That is, there is no guarantee that a transmitted MSDU will be delivered successfully. However, the QoS facility uses a traffic identifier (TID) to specify differentiated services on a per-MSDU basis.

[0117] A STA may differentiate MSDU delivery according to designated traffic category (TC) or traffic stream (TS) of individual MSDUs. The MAC sublayer entities determine a user priority (UP) for an MSDU based on a TID value provided with the MSDU. The QoS facility supports eight UP values. The UP values range from 0 to 7 and form an ordered sequence of priorities, with 1 being the lowest value, 7 the highest value, and 0 falling between 2 and 3.

[0118] An MSDU with a particular UP is said to belong to a traffic category with that UP. The UP may be provided with each MSDU at the medium access control service access point (MAC SAP) directly in an UP parameter. An A-MPDU may include MPDUs with different TID values. [0119] A STA may deliver buffer status reports (BSRs) to assist an AP in allocating UL MU resources. The STA may either implicitly deliver BSRs in the QoS control field or BSR control subfield of any frame transmitted to the AP (unsolicited BSR) or explicitly deliver BSRs in a frame sent to the AP in response to a BSRP Trigger frame (solicited BSR).

[0120] The buffer status reported in the QoS control field includes a queue size value for a given TID. The buffer status reported in the BSR control field includes an ACI bitmap, delta TID, a high priority AC, and two queue sizes.

[0121] A STA may report buffer status to the AP, in the QoS control field, of transmitted QoS null frames and QoS data frames and, in the BSR control subfield (if present), of transmitted QoS null frames, QoS data frames, and management frames as defined below.

[0122] The STA may report the queue size for a given TID in the queue size subfield of the QoS control field of transmitted QoS data frames or QoS null frames; the STA may set the queue size subfield to 255 to indicate an unknown/unspecified queue size for that TID. The STA may aggregate multiple QoS data frames or QoS null frames in an A-MPDU to report the queue size for different TIDs.

[0123] The STA may report buffer status in the BSR control subfield of transmitted frames if the AP has indicated its support for receiving the BSR control subfield.

[0124] A High-Efficiency (HE) STA may report the queue size for a preferred AC, indicated by the ACI high subfield, in the queue size high subfield of the BSR control subfield. The STA may set the queue size high subfield to 255 to indicate an unknown/unspecified queue size for that AC.

[0125] A HE STA may report the queue size for ACs indicated by the ACI bitmap subfield in the queue size all subfield of the BSR control subfield. The STA may set the queue size all subfield to 255 to indicate an unknown/unspecified BSR for those ACs.

[0126] Enhanced distributed channel access (EDCA) is a listen-before-talk access mechanism that allows exactly one STA to access a channel and to transmit a PPDU in a given time slot. Before transmission using EDCA, a STA listens to the channel for a minimum of an Arbitration Interframe Space (AIFS) duration to determine whether the channel state is IDLE. This listening time for determining whether the channel is IDLE may be followed by one or more backoff slots before the STA attempts to transmit over the channel. The number of backoff slots is chosen randomly by the STA. This reduces the probability of multiple STAs attempting to transmit at the same time, which would result in a packet detect error. If the PPDU transmitted by the STA is received successfully, for example by an AP (not shown in the figure), the AP may respond with an acknowledgment (ACK) frame after a Short Interframe Space (SIPS) duration of receiving the PPDU. [0127] A multi-link device (MLD) is an entity capable of managing communication over multiple links. The MLD may be a logical entity and may have more than one affiliated station (STA). An MLD may be an access point MLD (AP MLD) where a STA affiliated with the MLD is an AP STA (or an AP). An MLD may be a non- access point MLD (non-AP MLD) where a STA affiliated with the MLD is a non-AP STA (or an STA). [0128] Communication across different frequency bands/channels may occur simultaneously, or not, depending on the capabilities of both the communicating AP MLD and non-AP MLD.

[0129] An MLD may have a single MAC service access point (MAC-SAP) to the LLC layer, which includes a MAC data service. The MLD may support multiple MAC sublayers, coordinated by a sublayer management entity (SME). Each AP STA (or non-AP ST A) affiliated with an AP MLD (or non-AP MLD) has a different MAC address within the MLD.

[0130] The SME is responsible for coordinating the MAC sublayer management entities (MLMEs) of the affiliated STAs of the MLD to maintain a single robust security network association (RSNA) key management entity as well as a single IEEE 802.1X Authenticator or Supplicant for multi-link operation (MLO).

[0131] Multi-link operation (MLO) procedures allow a pair of MLDs to discover, synchronize, (de)authenticate, (re)associate, disassociate, and manage resources with each other on any common bands or channels that are supported by both MLDs. The Authenticator and the MAC-SAP of an AP MLD may be identified by the same AP MLD MAC address. The Supplicant and the MAC-SAP of a non-AP MLD may be identified by the same non-AP MLD MAC address.

[0132] FIG. 8 illustrates a non-High Throughput (non-HT) PPDU 810, a HT-Mixed Mode PPDU 820, and Very High Throughput (VHT) PPDU 830.

[0133] Non-HT PPDU 810 may be used by STAs conforming to the IEEE 802.1 1a standard amendment. As shown in FIG. 8, non-HT PPDU 810 includes a non-HT Short Training field (L-STF), a non-HT Long Training field (L-LTF), a non-HT Signal field (L-SIG), and a Data field. The L-STF, L-LTF, and L-SIG form a 20 pis preamble of non-HT PPDU 810.

[0134] The L-STF may be used by a receiver of non-HT PPDU 810 to synchronize with the carrier frequency and frame timing of a transmitter of non-HT PPDU 810 and to adjust the receiver signal gain. The L-LTF may be used by the receiver of non-HT PPDU 810 to estimate channel coefficients in order to equalize the channel response (e.g., amplitude and phase distortion) in both the L-SIG and the Data fields of non-HT PPDU 810. [0135] The L-SIG contains parameters needed to demodulate the Data field, which contains a payload of non-HT PPDU 810. The L-SIG may be equalized using the channel coefficients estimated using the L-LTF and demodulated to obtain the demodulation parameters of the Data field. The Data Field includes one or more symbols each having a duration of 4 pis, where 3.2 pis carry symbol information and 0.8 pis carry a Guard Interval (Gl).

[0136] For non-HT PPDUs, the only supported bandwidth is 20MHz, which is divided into 64 subcarriers. As such, non-HT PPDU 810 may be encoded using a subcarrier spacing of 20MHz/64 or 312.5kHz.

[0137] HT-Mixed Mode PPDU 820 may be used by STAs conforming to the IEEE 802.11n standard amendment. HT-Mixed Mode PPDU 820 can support MIMO to up to 4 spatial streams, which enhances spectral efficiency four folds. HT-Mixed Mode PPDU 820 has a minimum preamble duration of 35.6 pis, which may increase depending on the number of spatial streams carried by the PPDU. [0138] As shown in FIG. 8, HT-Mixed Mode PPDU 820 includes an L-STF, an L-LTF, an L-SIG, an HT Signal field (HT-SIG) field, an HT Short Training field (HT-STF) field, one or more HT Long Training field (HT- LTF), and a Data field. The HT-LTF and Data fields include of one or more symbols each having a duration of 3.6 pis or 4 pis. In both cases, 3.2 ps carry symbol information while the remaining 0.4 ps or 0.8 ps carry a Gl. The 0.4 ps long Gl is called short Gl while the 0.8 ps long Gl is called regular or normal Gl.

[0139] For HT-Mixed Mode PPDUs, two bandwidths, 20 MHz and 80 MHz, may be supported. When the PPDU bandwidth is 20MHz, the band is divided into 64 subcarriers. When the PPDU bandwidth is 80 MHz, the band is divided into 128 subcarriers. In both cases, subcarrier spacing of 312.5 kHz is maintained.

[0140] VHT PPDU 830 may be used by STAs conforming to the IEEE 802.1 1 ac standard amendment. VHT PPDU 830 can support MIMO to up to 8 spatial streams, which enhances spectral efficiency eight folds. VHT PPDU 830 has a minimum preamble duration of 39.6 ps, which may increase depending on the number of spatial streams carried by the VHT PPDU 830.

[0141] As shown in FIG. 8, VHT PPDU 830 includes an L-STF, an L-LTF, an L-SIG, a VHT Signal A field (VHT-S IG-A), a VHT Short Training field (VHT-STF), one or more VHT Long Training field (VHT-LTF), a VHT Signal B field (VHT-SIG-B) and a Data field. The VHT-LTF and data fields of VHT PPDU 830 include of one or more symbols each having a duration of 3.6 ps or 4 ps. In both cases, 3.2 ps carry symbol information while the remaining 0.4 ps or 0.8 ps carry of the Gl. The 0.4ps long Gl is called the short Gl while the 0.8ps long is called regular or normal Gl.

[0142] For VHT PPDUs, four bandwidths, 20 MHz, 80 MHz, 80 MHz, and 160 MHz, may be supported. When the PPDU bandwidth is 20MHz, the band is divided into 64 subcarriers. When the PPDU bandwidth is 40 MHz, the band is divided into 128 subcarriers. When the PPDU bandwidth is 80MHz, the band is divided into 256 subcarriers. When the PPDU bandwidth is 160 MHz, the band is divided into two 256-subcarrier 80MHz bands. In all cases, a subcarrier spacing of 312.5 kHz is maintained.

[0143] In an implementation, VHT PPDU 830 may be used as a VHT SU PPDU that carries one PHY service data unit (PSDU) for one user and is not transmitted using the downlink multi-user multiple input, multiple output (DL MU-MIMO) technique. In another implementation, VHT PPDU 830 may be used as a VHT MU PPDU that is capable of carrying up to four PHY service data units (PSDUs) for up to four users and is transmitted using the downlink multi-user multiple input, multiple output (DL MUMIMO) technique.

[0144] FIG. 9 illustrates a High Efficiency (HE) Single User (SU) PPDU 910, an HE Multi-user (MU) PPDU 920, and an HE Extended Range (ER) SU PPDU 930. HE SU PPDU 910, HE MU PPDU 920, and HE ER SU PPDU 930 may be used by STAs conforming to the IEEE 802.1 1ax standard amendment.

[0145] HE SU PPDU 910 supports higher spectral efficiency compared to VHT PPDU 1430 due to increased subcarrier spacing and higher order modulation support. HE SU PPDU 910 has a minimum preamble duration of 44 pis. [0146] As shown in FIG. 9, HE SU PPDU 910 includes an L-STF, an L-LTF, an L-SIG, a Repeated L-SIG (RL-SIG), a High Efficiency (HE) Signal A field (HE-SIG-A), an HE Short Training field (HE-STF) field, one or more HE Long Training field (HE-LTF), a Data field, and a Packet extension (PE) field.

[0147] Similar to HE SU PPDU 910, HE MU PPDU 920 supports higher spectral efficiency compared to VHT PPDU 430. HE MU PPDU 920 also supports OFDMA. Due to denser subcarrier spacing (as in HE SU PPDU 910), HE MU PPDU 920 allows for payloads of multiple users to be multiplexed in the frequency domain in the data field. HE MU PPDU 920 supports multiplexing the payloads of up to 9 users in a single 20MHz band. HE MU PPDU 920 has a minimum preamble duration of 47.2 pis, which may increase depending on the number of spatial streams carried by the HE MU PPDU 920.

[0148] As shown in FIG. 9, HE MU PPDU 920 includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE- SIG-A, an HE Signal B Field (HE-SIG-B), an HE-STF field, one or more HE-LTF field, a Data field, and a PE field. It is noted that compared to HE SU PPDU 910, HE MU PPDU 920 further includes HE-SIG-B. HE-SIG- B contains indications per STA of RU allocations. A STA may use the indications in HE-SIG-B to locate its payload in HE MU PPDU 920.

[0149] For HE SU PPDU 910 and HE MU PPDU 920, the Gl portion of the HE-LTF and data fields may be one of one of 0.8 pis, 1 .6 pis, and 3.2 pis. An AP or STA may use a suitable Gl duration depending on the channel conditions or capability of the target STA or AP.

[0150] For both HE SU PPDU 910 and HE MU PPDU 920, the information portion of the HE-LTF may be one of 3.2 pis, 6.4 pis, or 12.8 pis. Depending on the information portion duration, a subcarrier spacing of the HE-LTF may be one of: 312.5kHz if the information potion is 3.2 pis, 156.25kHz if the information portion is 6.4 pis, and 78 125kHz if the information portion is 12.8 pis. Unlink the HE-LTF, the information portion of the Data field for both HE SU PPDU 1510 and HE MU PPDU 1520 is always 12.8 pis. Hence, a subcarrier spacing of the data field is always 78.125kHz corresponding to the duration of the information portion being 12.8 pis. When a 3.2 pis or 6.4 pis long HE-LTF is used by a transmitting STA to transmit HE SU PPDU 910 or HE MU PPDU 920, a receiving STA is required to interpolate the channel estimates to a subcarrier spacing resolution of 78.125kHz to match the subcarrier spacing of the Data field.

[0151] As shown in FIG. 9, HE ER SU PPDU 930 includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, an HE-SIG-A, an HE-STF, one or more HE-LTF, a Data field, and a PE field. It is noted that compared to HE SU PPDU 910, HE ER SU PPDU 930 has an HE-SIG-A that is duplicated in the time domain (16 pis long instead of 8 pis long in HE SU PPDU 410). As such, both L-SIG (duplicated using RL-SIG) and HE-SIG-A are sent in duplicates, which allows a receiving STA to combine the two copies to increase the energy of the received signal. This results in an extended range of reception and increases transmission reliability between the transmitting STA and the receiving STA.

[0152] FIG. 10 illustrates an Extremely High Throughput (EHT) Multi-user (MU) PPDU 1000. EHT MU PPDU 1000 may be used by STAs conforming to the IEEE 802.1 1be standard amendment. EHT MU PPDU 1000 supports OFDMA but up to a bandwidth of 320MHz. EHT MU PPDU 1000 further improves spectral efficiency due to a support of an even higher order modulation compared to other PPDUs (e.g., HE SU PPDU 910 and HE MU PPDU 920) while supporting the same number of spatial streams. EHT MU PPDU 1000 has a minimum preamble duration of 47.2 pis, which may increase depending on the number of spatial streams carried by the EHT MU PPDU 1000.

[0153] As shown in FIG. 10, EHT MU PPDU 1000 includes an L-STF, an L-LTF, an L-SIG, an RL-SIG, a Universal Signal field (U-SIG), an EHT Signal Field (EHT-SIG), an EHT Short Training Field (EHT-STF) field, one or more EHT Long Training field (EHT-LTF), a Data field, and a PE field. It is noted that according to the IEEE 802.11 be standard amendment, EHT MU PPDU 1000 may be used by a transmitting STA for both SU and MU transmissions.

[0154] The U-SIG is intended to ensure forward compatibility of EHT MU PPDU 1000. This means that any future PPDUs that are backward compatible to IEEE 802.11 be will contain the same U-SIG field and interpretation. Because of this, IEEE 802.1 1 be STAs will be able to understand at least in part a PPDU developed in a future amendment.

[0155] The EHT-SIG contains indications per STA of resource unit (RU) allocations. A STA may use the indications in the EHT-SIG to locate its payload in EHT MU PPDU 1000.

[0156] The Gl portion of the EHT-LTF and data fields of EHT MU PPDU 1000 may be one of: 0.8 pis, 1.6 pis, or 3.2 pis. An AP or STA may use a suitable Gl duration depending on the channel conditions or capability of the target STA or AP.

[0157] The information portion of the EHT-LTF may be one of 3.2 pis, 6.4 pis, or 12.8 pis. Depending on the information portion duration, a subcarrier spacing of the EHT-LTF may be one of: 312.5kHz if the information potion is 3.2 pis, 156.25kHz if the information portion is 6.4 pis, or 78.125kHz if the information portion is 12.8 pis. The information portion of the Data field of EHT MU PPDU 1000 is always 12.8 pis. Hence, a subcarrier spacing of the data field is always 78.125kHz corresponding to the duration of the information portion being 12.8 pis. When a 3.2 pis long or a 6.4 pis long EHT-LTF is used by a transmitting STA to transmit EHT MU PPDU 1000, a receiving STA is required to interpolate the channel estimates to a subcarrier spacing resolution of 78.125kHz to match the data field subcarrier spacing.

[0158] FIG. 11 illustrates an example multi-user request-to-send (MU-RTS) trigger frame 1100. MU-RTS trigger frame 1100 may be used by an AP to solicit simultaneous CTS frames from multiple STAs to transmit a downlink (DL) MU PPDU to the multiple STAs. As shown in FIG. 11 , example MU-RTS trigger frame 1100 may comprise a frame control field, a duration field, a receiver address (RA) field, a transmitter address (TA) field, a common info field, a user info list field, a padding field, and/or frame check sequence (FCS) field. The frame control, TA, RA, padding, and FCS fields may be similar to the corresponding fields of trigger frame 500 described above. The duration field may be set to the time, in microseconds, required to transmit the DL MU PPDU, plus the time required to transmit one CTS frame, one ACK frame (if required), and three SIPS periods.

[0159] In an example, the common info field may be a high-efficiency (HE) variant common info field or an extremely high throughput (EHT) variant common info field. An EHT variant common info field may comprise, as shown in FIG. 11 , one or more of the following subfields: trigger type, UL length, more TF, CS required, UL BW, Gl and HE/EHT-LTF Type/Triggered TXOP sharing mode, number of HE/EHT-LTF symbols, LDPC extra symbol segment, AP Tx Power, Pre-FEC padding factor, PE disambiguity, UL spatial reuse, HE/EHT P160, special user info field flag, EHT reserved, reserved, or trigger dependent common info.

[0160] The trigger type subfield indicates that frame 1100 is an MU-RTS trigger frame.

[0161] The Gl and HE/EHT-LTF Type/Triggered TXOP sharing mode subfield may include a triggered TXOP sharing mode subfield. In an example, the triggered TXOP sharing mode subfield may be set to a zero value indicating the MU-RTS that does not initiate TXS procedure. In an example, the triggered TXOP sharing mode subfield may be set to a non-zero value (e.g., 1 or 2). In an example, the triggered TXOP sharing mode subfield may be set to 1. As such, the triggered TXOP sharing mode subfield may indicate that a STA indicated by an AID12 subfield of a user info field (of the user info list field) may transmit one or more non- TB PPDUs to the AP during a time indicated in the allocation duration subfield of the user info field. In another example, the triggered TXOP sharing mode subfield may be set to 2. As such, the triggered TXOP sharing mode subfield may indicate that a STA indicated by an AID12 subfield of a user info field (of the user info list field) may transmit one or more non-TB PPDUs to the AP or to a peer STA during the time indicated by the allocation duration subfield of the user info field. In an example, the peer STA may be a STA with a connection for P2P communication or direct communication with the STA.

[0162] The user info list field may include one or more user info fields. In an example, an EHT variant user info field may comprise, as shown in FIG. 11 , one or more of the following subfields: AID12, RU allocation, allocation duration, reserved, or PS160.

[0163] The AID12 subfield may indicate an association identifier (AID) of a STA that may use a time indicated by the allocation duration subfield.

[0164] The RU allocation subfield may indicate the location and size of the RU allocated for a STA indicated by the AID12 subfield.

[0165] The allocation duration subfield may indicate a time allocated by an AP transmitting MRTT frame 1 100. The allocated time may be a portion a TXOP obtained by the AP.

[0166] FIG. 12 illustrates an example block acknowledgment request (BlockAckReq or BAR) frame 1200. As shown in FIG. 12, example BAR frame 1200 may comprise a frame control field, a duration field, a receiver address (RA) field, a transmitter address (TA) field, a BAR control field, a BAR information field, and/or frame check sequence (FCS) field. [0167] The frame control and FCS fields may be similar to the corresponding fields of trigger frame 500 described above.

[0168] The Duration/ID field is set to the estimated time required to transmit.

[0169] one Ack or BlockAck frame, as applicable, plus one SIFS

[0170] The RA field indicates the address of a recipient STA of BAR frame 1200.

[0171] The TA field indicates the address of a STA transmitting BAR frame 1200 or a bandwidth signaling TA.

[0172] The BAR control field includes a first reserved subfield, a BAR type subfield, a second reserved subfield, and a TID_INFO subfield.

[0173] The BAR type subfield of the BAR control field indicates a frame variant of BAR frame 1200. For example, the BAR type subfield set to 1 indicates an extended compressed BlockAckReq frame variant. The BAR type subfield set to 2 indicates a compressed BlockAckReq frame variant. The BAR type subfield set to 3 indicates a multi-TID BlockAckReq frame variant. The BAR type subfield set to 6 indicates a groupcast with retries (GCR) BlockAckReq frame variant. The BAR type subfield set to 10 indicates a general link groupcast with retries (GLK-GCR) BlockAckReq frame variant. The values 0, 4-5, 7-9, and 11-15 are currently reserved. [0174] The meaning of the TID_INFO subfield of the BAR Control field depends on the BlockAckReq frame variant type indicated by the BAR type subfield. For example, the TID_INFO subfield of the BAR Control field of the Compressed BlockAckReq frame contains the TID for which a BlockAck frame is requested.

[0175] The meaning of the BAR Information field of the BlockAckReq frame depends on the BlockAckReq frame variant type. For example, the BAR Information field of the Compressed BlockAckReq frame contains a Block Ack Starting Sequence Control subfield.

[0176] FIG. 13 illustrates an example 1300 of a power save (PS) mode. As shown in FIG. 13, example 1300 includes STAs 1302 and 1304. STAs 1302 and 1304 may each be an AP STA or a non-AP STA. It is assumed that STA 1304 implements the PS mode illustrated in FIG. 13, which may be denoted as a dynamic PS mode or a low power listening (LPL) mode.

[0177] In an implementation, a STA (AP STA or non-AP STA) implementing the PS mode illustrated in FIG. 13 may be in a first power state/mode of the PS mode or in a second power state/mode of the PS mode. The first power state/mode may be referred to as a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode. The second power state/mode may be referred to as a higher capability state/mode, a higher power receive state/mode or an awake state/mode. While in the first power state/mode, the STA is capable of receiving PPDUs of a first category. While in the second power state/mode, the STA is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, the STA is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, the STA is capable of receiving PPDUs of only the first category during the first power state/mode. [0178] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 810 described above. In another implementation, the first category may include, additionally or alternatively, PPDUs having a data rate that is less than or equal to 24 Mbps, a bandwidth of 20 MHz, and/or a single spatial stream. The second category may include PPDUs having a format other than the non- HT PPDU format. For example, the second category may include PPDUs having a high throughput (HT) format, such as HT Mixed Mode PPDU 820, a VHT format such as VHT PPDU 830, an HE PPDU such as HE SU PPDU 910, HE MU PPDU 920, or HE ER SU PPDU 930, an EHT PPDU such as EHT MU PPDU 1000, an ultra-high reliability (UHR) PPDU, or a physical layer version identifier field. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 24 Mbps, a bandwidth greater than 20 MHz, and/or a plurality of spatial streams.

[0179] The STA may transition between the first power state/mode and the second power state/mode of the PS. In an implementation, to reduce the power consumption of the STA, the first power state/mode may correspond to a default state of the PS mode. As such, the STA may operate in the first power state/mode and may transition to the second power state/mode as needed.

[0180] In an implementation, as illustrated in example 1300, the STA may transition from the first power state/mode to the second power state/mode in response to being solicited by another STA. For example, as shown in FIG. 13, STA 1304, which implements the PS mode, may operate in the first power state/mode and may transition to the second power state/mode in response to a solicitation from STA 1302. Specifically, STA 1302 may transmit an initial control frame (IGF) 1306 to STA 1304 requesting that STA 1304 transition from the first power state/mode to the second power state/mode of the PS mode. STA 1302 may request that STA 1304 transition from the first power state/mode to the second power state/mode in order to transmit to STA 1304 a PPDU 1310 of the second category that STA 1304 is not capable of receiving during the first power state/mode (e.g., an EHT PPDU, a PPDU having a bandwidth greater than 20 MHz, and/or a PPDU having multiple spatial streams). In an implementation, IGF 1306 may be a request to send (RTS) frame, a multiuser RTS (MU-RTS) frame or a BlockAck Request (BAR) frame. ICF 1306 may be carried in a PPDU of the first category. In an implementation, ICF 1306 may be carried in a PPDU using a non-HT duplicate format with a bandwidth of 40 MHz, 80 MHz, 160 MHz or 320 MHz. In an implementation, ICF 1306 may include signaling indicating the PPDU bandwidth.

[0181] On receiving ICF 1306, STA 1304 initiates a transition from the first power state/mode to the second power state/mode. For example, on receiving ICF 1306, STA 1304 may enable/power on receiver capabilities needed to receive the PPDU of the second category that STA 1302 wishes to transmit to STA 1304. The transition from the first power state/mode to the second power state/mode may be associated with a state transition duration. The state transition duration may depend on the processing capabilities of STA 1304. In an implementation, STA 1302 may include padding in ICF 1306 to allow STA 1304 to transition from the first power state/mode to the second power state/mode in a timely manner. Hence, as shown in FIG. 13, STA 1304 may start the state transition before the reception of IGF 1306 is completed (i.e. without decoding the padding information).

[0182] In an implementation, STA 1304 responds to ICF 1306 by transmitting an initial control response (ICR) 1308 to STA 1302. ICR 1308 informs STA 1302 that STA 1304 is transitioning from the first power state/mode to the second power state/mode. In an implementation, as shown in FIG. 13, STA 1304 may transmit ICR 1308 while transitioning from the first power state/mode to the second power state/mode. In an implementation, STA 1304 may transmit ICR 1308 after completing the transition from the first power state/mode to the second power state/mode. Completing the transition before transmitting ICR 1308 may enable STA 1304 to perform clear channel assessment over a bandwidth that is higher than 20 MHz. This may enable STA 1304 to transmit ICR 1308 on idle channels with bandwidths higher than 20 MHz, which improves hidden node protection due to the transmission of ICR 1308. In another implementation, STA 1304 may transmit ICR 1308 before completing the transition to the second power state/mode. In such an implementation, STA 1304 may only be able to transmit ICR 1308 using a bandwidth of 20 MHz. ICR 1308 may be carried in a PPDU of the first category or the second category. In an implementation, STA 1304 transmits ICR 1308 a short interframe space (SIFS) after receiving ICF 1306.

[0183] On receiving ICR 1308, STA 1302 initiates transmission of PPDU 1310. In an implementation, STA 1302 transmits PPDU 1310 a SIFS after receiving ICR 1308. In an implementation, STA 1302 may begin transmitting PPDU 1310 while STA 1304 is still transitioning from the first power state/mode to the second power state/mode. PPDU 1310 may thus include a first PPDU part 1314 of the first category and a second PPDU part 1316 of the second category. In another implementation, STA 1302 may begin transmitting PPDU 1310 after STA 1304 has transitioned to the second power state/mode. PPDU 1310 may thus be entirely of the second category.

[0184] After receiving PPDU 1310, STA 1304 may transmit a BA frame 1312 to STA 1302. In an implementation, STA 1304 may return to the first power state/mode after receiving PPDU 1310. STA 1304 may transmit BA frame 1312 while in the second power state/mode or after returning to the first power state/mode.

[0185] FIG. 14 illustrates an example 1400 of an AP implementation of the PS mode illustrated in FIG. 13. As shown in FIG. 14, example 1400 includes an AP 1402 and a STA 1404. STA 1404 may be associated with AP 1402. It is assumed that AP 1402 implements the PS mode illustrated in FIG. 13. Specifically, as described above, while in the first power state/mode of the PS mode, AP 1402 is capable of receiving PPDUs of a first category; and while in the second power state/mode of the PS mode, AP 1402 is capable of receiving PPDUs of the first category and PPDUs of a second category. The first category and the second category may be as described above with reference to FIG. 13.

[0186] In an implementation, while in the first power state/mode, AP 1402 is capable of receiving data frames carried by PPDUs of the first category. In another implementation, AP 1402 is capable of receiving PPDUs of the first category while in the first power state/mode, AP 1402 is not capable of receiving the data frames carried by PPDUs of the first category while in the first power state/mode. In an implementation, while in the second power state/mode, AP 1402 is capable of receiving data frames carried by PPDUs of the first category or the second category.

[0187] Additionally, AP 1402 may support another mode of operation. The other mode may correspond to an active mode or to a power saving mode different than the PS mode illustrated in FIG. 19. The other mode may have one or more power state/modes. AP 1402 may be capable of receiving PPDUs of the first category and/or of the second category in any power state/mode.

[0188] In an implementation, AP 1402 may be configured to announce a time period during which AP 1402 will operate in the PS mode. For example, as shown in FIG. 14, during a first time period, AP 1402 may transmit a frame 1406 indicating or announcing a second time period during which AP 1402 will operate in the PS. The second time period may or may not be adjacent to the first time period. In an implementation, AP 1402 may be operating in the other mode during the first time period. In another implementation, AP 1402 may be operating in the PS mode during the first time period. Frame 1406 may indicate a start time T 1 and an end time T2 of the second time period. Alternatively, frame 1406 may indicate a start time T1 and a duration of the second time period.

[0189] In an example, as shown in FIG. 14, AP 1402 may be in the other mode before switching to the PS mode at the beginning of the second time period. In an implementation, AP 1402 may be configured, upon switching to the PS mode from the other mode, to operate in a default state of the PS mode. In an implementation, the default state may be the first power state/mode as described above. In another example, not shown in FIG. 14, AP 1402 be in the second power state/mode of the PS mode before the beginning of the second time period . AP 1402 may switch from the second power state/mode to the first power state/mode of the PS mode at the beginning of the second time period.

[0190] In an implementation, as illustrated in example 1400, AP 1402 may transition from the first power state/mode to the second power state/mode in response to being solicited by a STA. For example, as shown in FIG. 14, after switching to the PS mode at the beginning of the second time period, AP 1402 may operate in the first power state/mode. Subsequently, AP 1402 receives an ICF 1408 requesting that AP 1402 transition from the first power state/mode to the second power state/mode to receive from STA 1404 a PPDU 1412 of the second category. On receiving ICF 1408 from STA 1404, AP 1402 may respond with an ICR 1410 and may initiate a transition from the first power state/mode to the second power state/mode.

[0191] In an implementation, AP 1402 may determine, from ICF 1408, a TXOP duration, a bandwidth, and/or a modulation and coding scheme (MCS) of PPDU 1412. AP 1402 may turn on/enable receiver capabilities based on the bandwidth and MCS indicated in ICF 1408. In an implementation, AP 1402 may use the TXOP duration and the bandwidth indicated in ICF 1408 to reserve a suitable channel for PPDU 1412. For example, PPDU 1412 may have a bandwidth of 80 MHz and AP 1402 may reserve a primary 80 MHz channel for PPDU 1412. In an implementation, AP 1402 may perform a clear channel assessment (CCA) procedure over the channel to be used by STA 1404 for the transmission of PPDU 1412. After a successful CCA procedure, AP 1402 may transmit an ICR 1410 to STA 1404 ICR 1410 may be configured to reserve the channel to be used by STA 1404 for the transmission of PPDU 1412. In an implementation, ICR 1410 may be a clear to send (CTS) frame that indicates the channel to be used by STA 1404 for the transmission of PPDU 1412. [0192] On receiving ICR 1410, STA 1404 initiates transmission of PPDU 1412. In an implementation, STA 1404 transmits PPDU 1412 a SIFS after receiving ICR 1410. After receiving PPDU 1412, AP 1402 may transmit a BA frame 1414 to STA 1404. In an implementation, AP 1402 may return to the first power state/mode after receiving PPDU 1412. AP 1402 may transmit BA frame 1414 while in the second power state/mode or after returning to the first power state/mode. After the second time period, AP 1402 may transition to the other mode of operation or may remain in the first power state/mode of the PS mode.

[0193] A sounding PPDU is a PPDU transmitted by a transmitting STA to enable a receiving STA to estimate the channel between the transmitting STA and the receiving STA. According to the IEEE 802.11 standard, a sounding PPDU is a PPDU for which the SOUNDING parameter of the corresponding RXVECTOR or TXVECTOR has the value SOUNDING.

[0194] In an example, the sounding PPDU comprises a sounding null data PPDU (NDP). The NDP is a PPDU that carries no data field. For example, the sounding NDP comprises a VHT NDP that uses the VHT PPDU 830 format illustrated in FIG. 8 but without the Data field and is a VHT SU PPDU. For example, the sounding NDP comprises a HE sounding NDP that uses HE SU PPDU 910 format illustrated in FIG. 9 but without the Data field and has a PE field that is 4 ps in duration. For example, the sounding NDP comprises an EHT sounding NDP that is an EHT MU PPDU 1000 format illustrated in FIG. 10 with a single EHT-SIG symbol encoded using EHT-MCS 0 and no Data field. The EHT-SIG field only contains a Common field for EHT sounding NDP and no User Specific field.

[0195] In an example, the sounding PPDU may comprise a PPDU carrying on training symbols of channel sounding. The training symbols may be known at a transmitting STA and a receiving STA. The receiving STA may use the training symbols of channel sounding to estimate the channel state information (CSI). The CSI may comprise channel coefficients.

[0196] Channel sounding may adopt transmit beamforming with explicit feedback mechanisms, such as explicit feedback beamforming, to allow the transmitting STA to transmit the sounding PPDU to the receiving STA.

[0197] Transmit beamforming is a technique in which a transmitting STA utilizes knowledge of a MIMO channel to generate a steering matrix that is applied to the transmitted signal to optimize reception at one or more receiving STAs. The STA transmitting using the steering matrix is called the beamformer (transmitter of the beamformed signal). The STA for which reception is optimized is called a beamformee (receiver of the beamformed signal). Transmit beamforming may be used for sounding a SU MIMO channel or a MU MIMO channel.

[0198] In explicit feedback beamforming, the beamformer may apply an orthonormal spatial mapping matrix as the steering matrix to training symbols in the sounding PPDU. By receiving the sounding PPDU over a MIMO channel, the beamformee measures an effective channel using the training symbols. The effective channel is a product of an equivalent complex baseband MIMO channel coefficient matrix and the steering matrix used on transmit. By using an estimate of the equivalent channel, the beamformee may prepare a channel quality indication (CQI) as CSI feedback or a beamforming feedback matrix as beamforming feedback. The beamformee quantizes the feedback and send it to the beamformer. The beamformer may use this feedback to calculate a new steering matrix for a beamformed data transmission.

[0199] An extremely high throughput (EHT) sounding protocol may use the explicit feedback beamforming. [0200] EHT STAs may use an EHT sounding protocol to determine CSI. The EHT sounding protocol may provide explicit feedback mechanisms, including an EHT non-trigger-based (non-TB) sounding sequence and an EHT trigger-based (TB) sounding sequence. An EHT beamformee may measure the channel using a training signal (e.g., an EHT sounding NDP) transmitted by an EHT beamformer and send back a transformed estimate of the CSI. The transformed estimate of the CSI comprises the quantized CQI feedback or a quantized beamforming feedback matrix based on the estimate of equivalent channel. The EHT beamformer may use this estimate to derive the steering matrix.

[0201] The EHT beamformee may return the estimate of the CSI in an EHT compressed beamforming/CQI report carried in one or more EHT compressed beamforming/CQI frames. There are three types of EHT compressed beamforming/CQI report:

[0202] a) SU feedback: The EHT compressed beamforming/CQI report comprises an EHT Compressed Beamforming Report field.

[0203] b) MU feedback: The EHT compressed beamforming/CQI report comprises an EHT Compressed Beamforming Report field and EHT MU exclusive beamforming report field.

[0204] c) CQI feedback: The EHT compressed beamforming/CQI report comprises an EHT CQI Report field.

[0205] The EHT compressed beamforming/CQI report may be carried in a single EHT compressed beamforming/CQI frame if the resulting frame is less than or equal to 11454 octets in length. Otherwise, the EHT beamforming feedback may be segmented and each segment may be carried in an EHT compressed beamforming/CQI frame.

[0206] An EHT beamformer shall support a maximum MPDU length for the EHT compressed beamforming/CQI report that is the minimum of 11454 octets and the maximum length of the EHT compressed beamforming/CQI report that the EHT beamformer intends to solicit from its EHT beamformee(s). [0207] FIG. 15 illustrates an EHT sounding null data PPDU (NDP) 1500. EHT sounding NDP 1500 may be used for sounding to one or more users. EHT sounding NDP 1500 may be a variant of EHT MU PPDU 1000. An EHT sounding NDP may be indicated by setting a “PPDU Type and Compression Mode” field of a U-SIG field of an EHT PPDU to 1 , an EHT-SIG MCS field of an EHT-SIG field of the EHT PPDU to 0, and a “Number of EHT-SIG Symbols” field to 0 in the U-SIG field of the EHT PPDU.

[0208] As shown in FIG. 15, EHT sounding NDP 1500 comprises a non-high throughput (non-HT) short training field (L-STF), a non-HT long training field (L-LTF), a non-HT signal field (L-SIG), a repeated non-HT signal field (RL-SIG), a universal signal field (U-SIG), an EHT signal field (EHT-SIG), an EHT short training field (EHT-STF), an EHT long training field (EHT-LTF), and a packet extension (PE) field.

[0209] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields may be referred to as pre-EHT modulated fields, while the EHT-STF, EHT-LTF, and PE fields may be referred to as EHT modulated fields. [0210] The EHT-LTF field may comprise one or more EHT-LTF symbols. The number of EHT-LTF symbols may be indicated in a “number of EHT-LTF symbols” field of the EHT-SIG field.

[0211] The EHT-LTF field provides a means for a receiver of EHT sounding NDP 1500 to estimate the MIMO channel between the set of constellation mapper outputs and the receive chains. A spatial stream may refer to one or more symbols that may be transmitted over multiple spatial dimensions that are created by the use of multiple antennas at both ends of a communications link. In an EHT MU PPDU, the transmitter provides training for NSS ,r, total spatial streams used for the transmission of PSDU(s) in an r-th resource unit (RU). In an EHT TB PPDU, the transmitter of user u in the r-th RU provides training for NSS,r,u spatial streams used for the transmission of the PSDU. For each subcarrier in the r-th RU, the MIMO channel that can be estimated is an NRX x NSS, r, total matrix.

[0212] An EHT transmission has a preamble that contains EHT-LTF symbols, where the data tones of each EHT-LTF symbol are multiplied by entries belonging to a matrix PEHT-LTF, to enable channel estimation at the receiver. When single stream pilots are used in 2 x or 4 x EHT-LTF, the pilot subcarriers of each EHT- LTF symbol are multiplied by the entries of a matrix REHT-LTF to allow receivers to track phase and/or frequency offset during MIMO channel estimation using the EHT-LTF. Single stream pilots are used for all spatial multiplexing modes (both UL and DL) defined in EHT except when 1 x EHT-LTF is used. PEHT-LTF is defined such that each modulated spatial stream in an RU is active on all subcarriers in that RU for which the EHT-LTF sequence takes a nonzero value.

[0213] In an EHT MU PPDU, the number of EHT-LTF symbols NEHT-LTF is indicated in the EHT-SIG field. In a non-OFDMA EHT MU PPDU or an EHT sounding NDP, the initial number of EHT-LTF symbols, initial NEHT-LTF, is a function of the total number of spatial streams NSS.

[0214] In order to improve the MIMO channel estimation for the reception of a non-OFDMA EHT MU PPDU or an EHT sounding NDP, the number of EHT-LTFs may be larger than the initial number of EHT-LTFs determined by the total number of spatial streams. If additional EHT-LTFs are used, then the total number of EHT-LTFs (which is signaled separately from NSS) can be no more than twice the initial number of EHT- LTFs determined by the number of spatial streams and chosen from the set {2 4 8}. Supporting additional EHT-LTFs is optional for the receiver, which is indicated by the maximum number of supported EHT-LTFs subfield of the EHT PHY capabilities information field.

[0215] FIG. 16 illustrates an example null data PPDU (NDP) announcement (NDPA) frame 1600. As shown in FIG. 16, example NDPA frame 1600 includes a Frame Control field, a Duration field, a receiver address (RA) field, a transmitter address (TA) field, a Sounding Dialog Token field, a STA Info List field, and a frame check sequence (FCS).

[0216] The Frame Control field indicates a type (NDPA) of NDPA frame 1600. The Duration field indicates a duration of NDPA frame 1600. The RA field indicates an address of one or more receiver of NDPA frame 1600. The TA field indicates an address of a transmitter of NDPA frame 1600. The TA field is set to the address of a STA transmitting NDPA frame 1600 or a bandwidth signaling TA of the STA transmitting NDPA frame 1600.

[0217] The Sounding Dialog Token field includes an NDP Announcement Variant subfield and a Sounding Dialog Token Number subfield. Based on its value, the NDP Announcement Variant subfield indicates a variant of NDPA frame 1600 from among four variants: a VHT NDP Announcement frame, an HE NDP Announcement frame, a Ranging NDP Announcement frame, and an EHT NDP Announcement frame. The NDP Announcement Variant subfield is set to 2 to identify NDPA frame 1600 as an HE NDP Announcement frame. The NDP Announcement Variant subfield is set to 3 to identify NDPA frame 1600 as an EHT NDP Announcement frame. In the HE NDP Announcement and the EHT NDP Announcement frame, the Duration, RA, and TA fields are set as in the VHT NDP Announcement frame. The Sounding Dialog Token Number subfield contains a value selected by the transmitter of NDPA frame 1600 to identify NDPA frame 1600.

[0218] The STA Info List field contains one or more STA Info fields. The STA Info List field includes at most one STA Info field per STA to which NDPA frame 1600 is addressed in the RA field. If the STA Info List field includes only one STA Info field with a value less than 2008 in an AID11 subfield, then in the case that NDPA frame 1600 is a VHT, HE, or EHT NDP Announcement frame the RA field is set to the address of the STA indicated in the only STA Info field of NDPA frame 1600. If STA Info List field includes more than one STA Info field with a value less than 2008 in the AID11 subfield, then the RA field is set to a broadcast address.

[0219] As shown in FIG. 7, a STA Info field may include an AID 1 1 subfield, a Partial Bandwidth (BW) Info subfield, an Nc Index subfield, a Feedback Type and Ng subfield, a Disambiguation subfield, and a Codebook Size subfield.

[0220] The AID11 subfield contains an identifier of a STA expected to process an EHT sounding NDP that follows NDPA frame 1600 and to prepare sounding feedback based on the EHT sounding NDP.

[0221] The Partial BW Info subfield includes a Resolution subfield and a Feedback Bitmap subfield. The Resolution subfield indicates a resolution bandwidth for each bit in the Feedback Bitmap subfield. The Feedback Bitmap subfield indicates whether feedback is requested for each resolution bandwidth and is ordered from a lowest frequency to a highest frequency, followed by zeros. A bit in the Feedback Bitmap subfield set to 1 indicates that feedback is requested for the corresponding frequency with the resolution bandwidth. For example, a first position bit (B1) of the Feedback Bitmap subfield set to 1 indicates a request for feedback for the lowest frequency at the indicated resolution bandwidth.

[0222] When NDPA frame 1600 is an EHT NDP Announcement frame and the bandwidth of a PPDU carrying NDPA frame 1600 is less than 320 MHz, bit B0 of the Resolution subfield is set to 0 to indicate a resolution bandwidth of 20 MHz.

[0223] When NDPA frame 1600 is an EHT NDP Announcement frame and the bandwidth of the PPDU carrying NDPA frame 1600 is equal to 20 MHz, the first position bit (B1 ) of the Feedback Bitmap subfield is set to 1 to indicate a request for feedback on a 242-tone RU. Bits B2-B8 of the Feedback Bitmap subfield are set to 0.

[0224] When NDPA frame 1600 is an EHT NDP Announcement frame and the bandwidth of the PPDU carrying NDPA frame 1600 is equal to 40 MHz, the first position bit (B1 ) and the second position bit (B2) of the Feedback Bitmap subfield respectively indicate a request for feedback on a respective 242-tone RU (of two 242-tone RUs) from lower frequency to higher frequency. Bits B3-B8 of the Feedback Bitmap subfield are set to 0.

[0225] When NDPA frame 1600 is an EHT NDP Announcement frame and the bandwidth of the PPDU carrying NDPA frame 1600 is equal to 80 MHz, bits B1-B4 of the Feedback Bitmap subfield set to 1 indicate a request for feedback on a 996-tone RU; otherwise, bits B1-B4 respectively indicate a request for feedback on a respective 242-tone RU (of four 242-tone RUs) from lower frequency to higher frequency. Bits B5-B8 of the Feedback Bitmap subfield are set to 0.

[0226] When NDPA frame 1600 is an EHT NDP Announcement frame and the bandwidth of the PPDU carrying NDPA frame 1600 is equal to 160 MHz, bits B1-B4 of the Feedback Bitmap subfield set to 1 indicate a request for feedback on a lower 996-tone RU (among a lower 996-tone RU and an upper 996-tone RU); otherwise, bits B1-B4 respectively indicate a request for feedback on a respective 242-tone RU (of four 242- tone RUs) from lower frequency to higher frequency in the lower 80 MHz of the 160 MHz PPDU bandwidth. Similarly, bits B5-B8 set to 1 indicate a request for feedback on the upper 996-tone RU (among the lower 996-tone RU and the upper 996-tone RU); otherwise, bits B5-B8 respectively indicate a request for feedback on a respective 242-tone RU (of the four 242-tone RUs) from lower frequency to higher frequency in the upper 80 MHz of the 160 MHz.

[0227] When NDPA frame 1600 is an EHT Announcement frame and the bandwidth of the PPDU carrying NDPA frame 1600 is equal to 320 MHz, bit B0 of the Resolution subfield set to 1 indicates a resolution bandwidth of 40 MHz. When bits B1 and B2 of the Feedback Bitmap subfield are both set to 1 , they indicate a request for feedback request on a lowest 996-tone RU (among a lowest 996-tone RU, a second lowest 996-tone RU, a third lowest 996-tone RU, and a highest 996-tone RU); otherwise, bits B1 and B2 respectively indicate a request for feedback on a respective 484-tone (of two 484-tone RUs) from lower frequency to higher frequency in a lowest 80 MHz of the 320 MHz PPDU bandwidth. When bits B3 and B4 of the Feedback Bitmap subfield are both set to 1 , they indicate a request for feedback on the second lowest 996-tone RU; otherwise, bits B3 and B4 indicate respectively a request for feedback on a respective 484-tone RU (of two 484-tone RUs) from lower frequency to higher frequency in a second lowest 80 MHz of the 320 MHz PPDU bandwidth. When bits B5 and B6 of the Feedback Bitmap subfield are both set to 1 , they indicate a request for feedback on the third lowest 996-tone RU; otherwise, B5 and B6 respectively indicate a request for feedback on respective 484-tone RU (of two 484-tone RUs) from lower frequency to higher frequency in a third lowest 80 MHz of the 320 MHz PPDU bandwidth. When bits B7 and B8 of the Feedback Bitmap subfield are both set to 1 , they indicate a request for feedback on the highest 996-tone RU; otherwise, bits B7 and B8 indicate respectively a request for feedback on respective 484-tone RU (of two 484-tone RUs) from lower frequency to higher frequency in a highest 80 MHz of the 320 MHz PPDU bandwidth. The feedback tone set for each 484-tone RU is composed of the feedback tone sets of the two 242-tone RUs overlapping with the 484-tone RU.

[0228] Returning to FIG. 16, the Nc Index subfield indicates the number of columns of a beamforming feedback matrix (reported in a compressed beamforming report in response to NDPA frame 1600) minus 1 , if the feedback is SU feedback or MU feedback; and indicates the number of spatial streams of a CQI report (reported in a CQI report in response to NDPA frame 1600) minus 1 , if the feedback is CQI feedback.

[0229] The “Feedback Type and Ng” subfield indicates a feedback type and a subcarrier grouping, Ng, to be used by the STA generating the sounding feedback based on the EHT sounding NDP that follows NDPA frame 1600. The feedback type may be SU feedback, MU feedback, or CQI feedback. The subcarrier grouping, Ng, indicates the number (e.g., 4, 16) of adjacent subcarriers that are to be grouped in a beamforming report. When grouping is used, a single beamforming feedback matrix is reported for each group of Ng adjacent subcarriers. The “Feedback Type and Ng” subfield and the Codebook Size subfield for EHT trigger-based (TB) sounding are the same as for HE TB sounding. The “Feedback Type and Ng” and the Codebook Size subfields for EHT non-TB sounding are the same as for HE non-TB sounding.

[0230] If NDPA frame 1600 is an EHT NDP Announcement frame with more than one STA Info field that contains a value less than 2008 in the AID11 subfield, the RA field indicates a broadcast address, and the Nc Index subfield may be set as follows:

— If the “Feedback Type and Ng” subfield and the Codebook Size subfield indicate single user (SU) or multi-user (MU), the Nc Index subfield indicates the number of columns in the compressed beamforming feedback matrix minus 1 , Nc-1 . Nc Index subfield values above 7 are reserved. — If the “Feedback Type and Ng’’ subfield and the Codebook Size subfield indicate channel quality information (CQI), the Nc Index subfield indicates the number of spatial streams in the CQI report minus 1 , Nc-1 . Nc Index subfield values above 7 are reserved.

[0231] If NDPA frame 1600 is an EHT NDP Announcement frame with a single STA Info field that contains a value less than 2008 in the AID1 1 subfield, the RA field indicates an individual address, and the Nc index subfield is reserved.

[0232] FIG. 17 illustrates an example STA Info field 1700. STA Info field 1700 may replace the STA Info field of NDPA frame 700 described above. For example, when the AID11 subfield of the STA info field is set to a particular value (e.g., 2047), the STA info field may have the format of STA Info field 1700 described herein. As shown in FIG. 8, STA Info field 1700 includes an AID11 subfield, a Disallowed Subchannel Bitmap subfield, and a Disambiguation subfield.

[0233] The AID11 subfield may be set to a particular value (e.g., 2047) When the AID11 subfield corresponds to a particular value (e.g., 2047), the Disallowed Subchannel Bitmap indicates the 20 MHz subchannels and the 242-tone RUs that are present in an HE sounding NDP announced by the NDPA frame, and the 242-tone RUs that are to be included in requested sounding feedback.

[0234] Each bit of the Disallowed Subchannel Bitmap corresponds to a respective 20 MHz subchannel of the BSS bandwidth. For example, the lowest numbered bit of the Disallowed Subchannel Bitmap corresponds to the 20 MHz subchannel of the BSS bandwidth with the lowest frequency of the set of 20 MHz subchannels within the BSS bandwidth. Each successive bit in the Disallowed Subchannel Bitmap corresponds to the next higher frequency 20 MHz subchannel of the 20 MHz subchannels within the BSS bandwidth.

[0235] FIG. 18 illustrates an example EHT compressed beamforming/CQI frame 1800. EHT Compressed Beamforming/CQI frame 1800 may be an Action No Ack frame of category EHT. The Action field of an EHT Compressed Beamforming/CQI frame contains the information including a Category field, an EHT Action field, an EHT MIMO Control field, an EHT Compressed Beamforming Report field, an EHT MU Exclusive Beamforming Report field, an EHT CQI Report.

[0236] The Category field is set to a value of 36 for EHT category.

[0237] The EHT Action field, in the octet immediately after the Category field, differentiates the EHT Action frame formats. The EHT Action field values associated with each frame format within the EHT category. The EHT Action field is set to a value of 0 for EHT Compressed Beamforming/CQI.

[0238] The EHT MIMO Control field comprises a Nc Index subfield, a Nr Index subfield, a BW subfield, a Grouping subfield, a Codebook Information subfield, a Feedback Type subfield, a Remaining Feedback Segments subfield, a First Feedback Segment subfield, a Partial BW Info subfield, a Sounding Dialog Token Number subfield.

[0239] In an EHT Compressed Beamforming/CQI frame not carrying all or part of an EHT compressed beamforming/CQI report, the Nc Index, Nr Index, BW, Grouping, Codebook Information, Feedback Type, and Sounding Dialog Token Number subfields are reserved, the First Feedback Segment subfield is set to 0, and the Remaining Feedback Segments subfield is set to 7.

[0240] The EHT Compressed Beamforming Report field carries the average SNR of each spatial stream and compressed beamforming feedback matrices for use by a transmit beamformer to determine steering matrices for explicit feedback beamforming.

[0241] The EHT MU Exclusive Beamforming Report field carries explicit feedback in the form of delta SNRs. The information in the EHT Compressed Beamforming Report field and the EHT MU Exclusive Beamforming Report field can be used by the transmit MU beamformer to determine the steering matrices for DL MU- MIMO.

[0242] The EHT CQI Report field carries the per-RU average SNRs of each spatial stream, where each per- RU average SNR is the arithmetic mean of the SNR in decibels over the subcarriers of a 26-tone RU for which feedback is being requested.

[0243] The EHT CQI Report field contains EHT CQI report information. EHT CQI Report information is included in the EHT compressed beamforming/CQI report if the Feedback Type subfield in the EHT MIMO Control field indicates CQI feedback.

[0244] The presence and contents of the EHT Compressed Beamforming Report field, EHT MU Exclusive Beamforming Report field, and EHT CQI Report field are dependent on the values of the Feedback Type subfield of the EHT MIMO Control field.

[0245] A Vendor Specific element is not present in the EHT Compressed Beamforming/CQI frame.

[0246] A beamforming report poll (BFRP) trigger frame may be a variation of the trigger frame 500 illustrated in FIG. 5. In an example, the Trigger Dependent Common Info subfield is not present in the BFRP Trigger frame. The Trigger Dependent User Info subfield of the BFRP Trigger frame may include a Feedback Segment Retransmission Bitmap subfield. The Feedback Segment Retransmission Bitmap subfield may indicate the requested feedback segments of an HE or EHT compressed beamforming/CQI report. If the bit in position n (n=0 for LSB and n=7 for MSB) is 1 , then the feedback segment with the Remaining Feedback Segments subfield in the HE MIMO Control field equal to n is requested. If the bit in position n is 0, then the feedback segment with the Remaining Feedback Segments subfield in the HE MIMO Control field equal to n is not requested.

[0247] If a BFRP Trigger frame solicits an EHT compressed beamforming/CQI report, all of the bits in the Feedback Segment Retransmission Bitmap subfield are set to 1.

[0248] FIG. 19 illustrates an example 1900 of a non-trigger based (non-TB) sounding sequence. As shown in FIG. 19, example 1900 includes an AP 1902 and a STA 1904. Example 1900 may begin with AP 1902 initiating the non-TB sounding sequence by transmitting an NDPA frame 1910 to STA 1904. NDPA frame 1910 may be an embodiment of NDPA frame 1600 described above. In an example, AP 1902 may be an EHT beamformer. In an example, NDPA frame 1910 may include a single STA Info field. The AIDH subfield of the STA Info field and the RA field of NDPA frame 1910 may be set to the AID of STA 1904.

[0249] NDPA frame 1910 may solicit SU feedback or CQI feedback from STA 1904. In an example, SU feedback may comprise a compressed beamforming report. In an example, the compressed beamforming report may comprise an average SNR of each spatial stream of an NDP that follows NDPA frame 1910 and compressed beamforming feedback matrices for use by AP 1902 to determine steering matrices for explicit feedback beamforming to STA 1904. In an example, CQI feedback may comprise a CQI report. In an example, the CQI report may comprise per-RU average SNRs of each spatial stream of the NDP. In an implementation, a per-RU average SNR may comprise an arithmetic mean of the SNR in decibels over the subcarriers of a 26-tone RU for which feedback is being requested.

[0250] A SIPS after transmitting NDPA frame 1910, AP 1902 transmits an NDP 1912. NDP 1912 may be an EHT sounding NDP. A SIPS after receiving NDP 1912, STA 1904 transmits a feedback frame 1914. Feedback frame 1914 may comprise an EHT compressed beamforming/CQI frame. For example, feedback frame 1914 may the comprise an EHT compressed beamforming/CQI report. A TXVECTOR parameter CH_BANDWIDTH for a PPDU containing feedback frame 1914 may be set to indicate a bandwidth not wider than that indicated by an RXVECTOR parameter CHJ3ANDWIDTH of the EHT sounding NDP.

[0251] In an implementation, example 1900 may represent an EHT non-TB sounding sequence. As such, AP 1902 may represent an EHT beamformer, STA 1904 may represent an EHT beamformee, and NDPA frame 1910 may be an EHT NDPA. In an implementation, where the STA Info field in NDPA frame 1910 solicits SU feedback, the subcarrier grouping, Ng, codebook size, and the number of columns, Nc, used by STA 1904 for the generation of the SU feedback are determined by STA 1904. In an implementation, where the STA Info field in NDPA frame 1910 solicits CQI feedback, the Nc used by STA 1904 for the generation of the CQI feedback is determined by STA 1904. In an implementation, when SU feedback is solicited, bit B26 of the "Feedback Type And Ng” subfield, the Codebook Size subfield, and the Nc Index subfield of the STA Info field of NDPA frame 1910 are reserved.

[0252] Continuing with the EHT non-TBsounding sequence implementation, on receiving NDPAframe 1910 soliciting SU feedback, STA 1904 generates an EHT compressed beamforming report for SU feedback with Nc in the range 1 to 8, Ng = 4 or Ng=16, and codebook size (4>,i ) = {4,2} or (4>,i ) = {6,4}. On receiving NDPA frame 1910 soliciting CQI feedback, STA 1904 generates an EHT CQI report for CQI feedback with Nc determined by STA 1904.

[0253] FIG. 20 illustrates an example 2000 of a trigger based (TB) sounding sequence. As shown in FIG. 20, example 2000 includes an AP 2002 and STAs 2004 and 2006. Example 2000 may begin with AP 2002 initiating the TB sounding sequence by transmitting an NDPA frame 2010 to STAs 2004 and 2006. NDPA frame 2010 may be an embodiment of NDPA frame 700 described above. In an example, AP 2002 may be an EHT beamformer. NDPA frame 2010 may include two STA Info fields with AID11 subfields set respectively to the AIDs of STAs 2004 and 2006. An RA field of NDPA frame 2010 may be set to a broadcast address. [0254] NDPA frame 2010 may solicit SU feedback, MU feedback, or CQI feedback from STAs 2004 and 2006. In an example, SU feedback may comprise a compressed beamforming report. In an example, the compressed beamforming report may comprise an average SNR of each spatial stream and compressed beamforming feedback matrices for use by AP 2002 to determine steering matrices for explicit feedback beamforming to STAs 2004 and 2006. In an example, MU feedback may comprise a compressed beamforming report and an MU exclusive beamforming report. In an example, the MU exclusive beamforming report may comprise explicit feedback in the form of delta SNRs. In an example, CQI feedback may comprise a CQI report. In an example, the CQI report may comprise per-RU average SNRs of each spatial stream. In an implementation, a per-RU average SNR may comprise an arithmetic mean of the SNR in decibels over the subcarriers of a 26-tone RU for which feedback is being requested. In an example, AP 1902 may be an EHT beamformer. NDPA frame 1910 may include a single STA Info field. The AID1 1 subfield of the STA Info field may be set to the AID of STA 1904.

[0255] A SIPS after transmitting NDPA frame 2010, AP 2002 transmits an NDP 2012. NDP 2012 may be an EHT sounding NDP. A SIFS after transmitting NDP 2012, AP 2002 transmits a trigger frame 2014. Trigger frame 2014 may be a beamforming report poll frame (BFRP) frame. Trigger frame 2014 may address STAs 2004 and 2006 as beamformees. A SIFS after receiving trigger frame 2014, STAs 2004 and 2006 may transmit respective feedback frames 2016 and 2018. Feedback frames 2016 and 2018 may each comprise an EHT compressed beamforming/CQI frame and may be carried in a TB PPDU. The EHT compressed beamforming/CQI frame may comprise one or more beamforming reports. For example, the beamforming report may comprise the compressed beamforming report, the MU exclusive beamforming report, or the CQI report.

[0256] In an implementation, AP 2002 may transmit additional trigger frames in the same TXOP to solicit feedback frames from EHT beamformees not addressed in trigger frame 2014. In an implementation, AP 2002 may not transmit a trigger frame that solicits a STA identified in NDPA frame 2010 unless the trigger frame is in the same TXOP as NDPA frame 2010.

[0257] In an implementation, example 2000 may represent an EHT TB sounding sequence. As such, AP 2002 may represent an EHT beamformer, STAs 2004 and 2005 may represent EHT beamformees, and NDPA frame 2010 may be an EHT NDPA.

[0258] In an implementation, as an EHT beamformer, AP 2002 may not transmit a BFRP Trigger frame that solicits a STA (e.g., STA 2004 or STA 2006) identified in NDPA frame 2010 unless the BFRP Trigger frame is in the same TXOP as the EHT TB sounding sequence. In an implementation, the STAs identified in NDPA frame 2010 are the same as the STAs identified in trigger frame(s) in the same TXOP. [0259] In an implementation, as an EHT beamformer, AP 2002 may set all the bits of a “Feedback Segment Retransmission Bitmap” field of (e.g., BFRP) trigger frame 2014 to 1 s. (BFRP) trigger frame 2014 contains one or more User Info fields, each of which identifies an EHT beamformee (e.g , STA 2004 or STA 2006). [0260] In an implementation, when NDPA frame 2010 solicits SU or MU feedback, a STA Info field in NDPA frame 2010 indicates the subcarrier grouping, Ng, codebook size, and the number of columns, Nc, to be used by the EHT beamformee identified by the STA Info field for the generation of the SU or MU feedback. In an implementation, when NDPA frame 2010 solicits CQI feedback, a STA Info field in NDPA frame 700 indicates the Nc to be used by the EHT beamformee identified by the STA Info field for the generation of the CQI feedback.

[0261] In an implementation, as an EHT beamformee, when STA 2004 (or STA 2006) receives NDPA frame 2010 soliciting CQI feedback, STA 2004/2006 generates an EHT CQI report for CQI feedback with Nc determined by AP 2002.

[0262] In an implementation, as an EHT beamformee, when STA 2004 (or STA 2006) receives NDPA frame 2010 with a STA Info field identifying STA 2004 (or STA 2006) soliciting SU or MU feedback, STA 2004 (or STA 2006) generates an EHT compressed beamforming report using the feedback type, Ng, codebook size, and Nc indicated in the STA Info field.

[0263] In an implementation, as an EHT beamformee, when STA 2004 (or STA 2006) receives (BFRP) trigger frame 2014 with a matching User Info field, STA 2004 (or STA 2006) transmits an EHT TB PPDU containing the EHT compressed beamforming/CQI report. In an implementation, AP 2002 transmits NDPA frame 2010 with a TA field set to a transmitted BSSID, and STA 2004 (or STA 2006) is a non-AP STA associated with an AP corresponding to a non-transmitted BSSID that supports receiving control frames with TA fields set to the transmitted BSSID, then the EHT compressed beamforming/CQI report sent by STA 2004 (or STA 2006) in response may include an RA field set to a MAC address of AP 2002.

[0264] In an implementation, if an EHT compressed beamforming/CQI report solicited by AP 2002 would result in a feedback frame (e.g., 2016 or 2018) that exceeds 11454 octets in length, then the EHT compressed beamforming/CQI report is split into up to eight feedback segments. Each feedback segment is included in a separate feedback frame and contains successive portions of the EHT compressed beamforming/CQI report. Feedback segments may be of equal length except the last feedback segment, which may be shorter. Each feedback frame that includes a feedback segment that is not the last feedback segment has a length of 11454 octets. Each feedback segment is identified by the value of the “Remaining Feedback Segments” subfield and the “First Feedback Segment” subfield in an EHT MIMO Control field of the feedback frame that includes the feedback segment. The other non-reserved subfields of the EHT MIMO Control field may be the same for all feedback segments. Feedback frames may be sent in an A-MPDU contained in a single PPDU and may be included in the A-MPDU in descending order based on values of the “Remaining Feedback Segments” subfield. [0265] In an implementation, as an EHT beamformer, when AP 2002 transmits (BFRP) trigger frame 2024 to retrieve an EHT compressed beamforming/CQI report from an EHT beamformee (e.g., STA 2004 or STA 2006), AP 2002 solicits all possible feedback segments by setting to 1 all of the bits of the "Feedback Segment Retransmission Bitmap” subfield of the User Info field (of trigger frame 2024) identifying the EHT beamformee.

[0266] In implementation, as an EHT beamformer, if AP 2002 fails to receive some or all of the feedback segments of the EHT compressed beamforming/CQI report from an EHT beamformee (e.g., STA 2004 or STA 2006), AP 2002 may not transmit a further BFRP T rigger frame to request retransmission of the feedback segments. Instead, AP 2002 may repeat the entire EHT sounding sequence.

[0267] FIG. 21 illustrates an example 2100 that highlights a problem that may arise in association with a sounding procedure in the power save (PS) mode illustrated in FIG. 13. As shown in FIG. 21 , example 2100 may include a STA 2102 and a STA 2104. STA 2102 may comprise an AP STA. STA 2104 may comprise a non-AP STA. STA 2104 may be associated with STA 2102.

[0268] In an example, STA 2102 may support non-TB sounding as an EHT beamformer as described in FIG. 19. In an example, STA 2104 may support non-TB sounding as an EHT beamformee as described in FIG. 19.

[0269] It is assumed that STA 2104 supports the PS mode illustrated in FIG. 13. In an implementation, STA 2104 implementing the PS mode may be in a first power state/mode of the PS mode or in a second power state/mode of the PS mode. The first power state/mode may be referred to as a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode. The second power state/mode may be referred to as a higher capability state/mode, a higher power receive state/mode or an awake state/mode. Specifically, as described above, in an example, while in the first power state/mode of the PS mode, STA 2104 is capable of receiving PPDUs of a first category. While in the second power state/mode of the PS mode, STA 2104 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, STA 2104 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, STA 2104 is capable of receiving PPDUs of only the first category during the first power state/mode.

[0270] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 810 described above. In another implementation, the first category may include, additionally or alternatively, PPDUs having a data rate that is less than or equal to 24 Mbps, a bandwidth of 20 MHz, and/or a single spatial stream. The second category may include PPDUs having a format other than the non- HT PPDU format. For example, the second category may include PPDUs having a high throughput (HT) format, such as HT Mixed Mode PPDU 820, a VHT format such as VHT PPDU 830, an HE PPDU such as HE SU PPDU 910, HE MU PPDU 920, or HE ER SU PPDU 930, an EHT PPDU such as EHT MU PPDU 1000, an ultra-high reliability (UHR) PPDU, or a physical layer version identifier field. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 24 Mbps, a bandwidth greater than 20 MHz, and/or a plurality of spatial streams. In an implementation, PPDUs of second category may further include sounding NDPs described above, for example, a VHT NDP, an HE sounding NDP, and EHT sounding NDP 1500.

[0271] In an implementation, while in the first power state/mode, STA 2104 is capable of receiving data frames carried by PPDUs of the first category. In another implementation, while STA 2104 is capable of receiving PPDUs of the first category while in the first power state/mode, STA 2102 is not capable of receiving data frames carried by PPDUs of the first category while in the first power state/mode. In an implementation, while in the second power state/mode, STA 2104 is capable of receiving data frames carried by PPDUs of the first category or the second category.

[0272] As shown in FIG. 21 , example 2100 may begin with STA 2104 operating in the first power state/mode. In an implementation, to reduce the power consumption of STA 2104, the first power state/mode may correspond to a default state of the PS mode as described in FIG. 13.

[0273] In an example, STA 2102 may have data buffered for transmission to STA 2104. STA 2102 may wish to transmit the buffered data to STA 2104 using beamforming. In an implementation, STA 2102 may perform the sounding procedure before transmitting a PPDU (e.g., PPDU 2120) carrying the buffered data of STA 2104. The PPDU carrying the buffered data of STA 2104 may be of the second category.

[0274] In an implementation, as illustrated in example 2100, STA 2104 may transition from the first power state/mode to the second power state/mode in response to being requested by STA 2102. Specifically, STA 2104 receives an initial control frame (IGF) 2106 from STA 2102 requesting that STA 2104 transition from the first power state/mode to the second power state/mode.

[0275] On receiving ICF 2106 from STA 2102, STA 2104 may initiate a transition from the first power state/mode to the second power state/mode at a time T1 and may respond with an ICR 2108. In an implementation, STA 2104 operates in the second power state/mode between time T1 and a time T2.

[0276] On receiving ICR 2108, STA 2102 may perform the sounding procedure with STA 2104 operating in the second power state/mode. The sounding procedure may begin with STA 2102 initiating an EHT non-TB sounding sequence by transmitting a null data PPDU announcement (NDPA) frame 21 10 that is carried by a PPDU of the first category. NDPA frame 2110 may comprise an EHT NDPA frame. NDPA frame 21 10 may announce an NDP 2112, that is a PPDU of the second category, to be transmitted by STA 2102 for estimating the channel by STA 2104. In an example, NDP 21 12 may comprise an EHT sounding NDP. In an example, NDPA frame 21 10 may solicit SU feedback or CQI feedback from STA 2104. A SIFS after transmitting NDPA frame 21 10, STA 2102 transmits NDP 2112 to STA 2104. A SIFS after receiving NDP 21 12, STA 2104 transmits to STA 2102 a feedback frame 2114 based on NDP 2112. In an example, feedback frame 2114 may comprise an EHT compressed beamforming/CQI frame including SU feedback or CQI feedback of the channel. In an example, feedback frame 21 14 may comprise an action no ack frame. [0277] In an implementation (as shown in FIG. 21), STA 2104 may return to the first power state/mode after transmitting feedback frame 21 14. As such, to transmit PPDU 2120 (which is of the second category) to STA 2104, STA 2102 may transmit an ICF 2116 requesting that STA 2104 transition from the first power state/mode to the second power state/mode to receive PPDU 2120. In an implementation, STA 2102 may perform EDCA to transmit ICF 2116. On receiving ICF 2116 from STA 2102, STA 2104 may respond with an ICR 2118 and may initiate a transition from the first power state/mode to the second power state/mode. This operation, however, may result in excessive overhead due to the need of STAs 2102 and 2104 to exchange ICF 2116 and ICR 2118 in order for STA 2102 to transmit PPDU 2120.

[0278] On receiving ICR 2118, STA 2102 initiates transmission of PPDU 2120. In an implementation, STA 2102 transmits PPDU 2120 a SIFS after receiving ICR 2118. After receiving PPDU 2120, STA 2104 may transmit a BA frame 2122 to STA 2102. In an implementation, STA 2104 may return to the first power state/mode after receiving PPDU 2120. STA 2104 may transmit BA frame 2122 while in the second power state/mode or after returning to the first power state/mode. After transmitting BA frame 2122, STA 2104 may transition to the other mode of operation or may remain in the first power state/mode of the PS mode.

[0279] In another example (not shown in FIG. 21 ), after transmitting feedback frame 2114, STA 2104 may remain in the second power state/mode, which may be a higher power receive state/mode, until STA 2102 transmits PPDU 2120 to STA 2104. This operation, however, may be energy inefficient as STA 2102 may not transmit PPDU 2120 immediately after receiving feedback frame 21 14 from STA 2104. As a result, despite implementing the PS mode described above, STA 2104 may operate in a manner that results in unnecessary overhead and/or high power consumption.

[0280] Embodiments of the present disclosure, as further described below, address the above-described problems of existing technologies. In an aspect, a first STA may transmit to a second STA, while the second STA operates in a power save (PS) mode, a first frame requesting/indicating that the second STA operate, during a first time period, in a first power state/mode of the PS mode. The first time period may occur after the second STA transmits a second frame comprising feedback to the first STA. The first frame may further announce a null data physical layer protocol data (NDP) to be transmitted by the first STA. The PS mode may comprise a dynamic PS mode or a low-power listening (LPL) mode, for example. The first power state/mode may be a higher capability state/mode, a higher power receive state/mode or an awake state/mode, for example. While in the first power state/mode, the second STA may be capable of receiving PPDUs of a first category and PPDUs of a second category. The first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 810 described above. In another implementation, the first category may include, additionally or alternatively, PPDUs having a data rate that is less than or equal to 24 Mbps, a bandwidth of 22 MHz, and/or a single spatial stream. The second category may include PPDUs having a format other than the non-HT PPDU format. The second power state/mode may be a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode, for example. While in the second power state/mode, the second STA may be capable of receiving PPDUs of a first category. The first STA may transmit to the second STA while the second STA operates in the first power state/mode, the NDP for use by the second STA to generate the feedback. The feedback may comprise a beamforming report or a channel quality indication (CQI) report. The first STA may transmit to the second STA and during the first time period, a PPDU. As the second STA operates in the first power state/mode during the first time period, a frame exchange to cause the second STA to transition to the first power state/mode is not needed. Additionally, to receive the PPDU, the second STA may only need to operate in the first power state/mode during the first time period. Signaling overhead and/or power consumption of the second STA during the sounding procedure may thus be reduced. In another aspect, a first AP may transmit to a first STA, while the first STA operates in a PS mode, a first frame requesting that the first STA operate, during a first time period, in a first power state/mode of the PS mode, where the first time period comprises a sounding sequence by the first AP and a second AP. The first AP may transmit to the first STA and during the first time period, an NDP for use by the first STA to generate feedback for the first AP. The first AP may receive from the first STA, and during the first time period, a second frame comprising the feedback. After receiving the feedback, the first AP may transmit a PPDU to the first STA. The first AP may transmit the PPDU using the feedback. [0281] FIG. 22 illustrates an example 2200 of a PS mode operation for beamformed data transmission according to an embodiment. Example 2200 is provided for the purpose of illustration only and is not limiting. As shown in FIG. 22, example 2200 may include a STA 2202 and a STA 2204. STA 2202 may comprise an AP STA. STA 2204 may comprise a non-AP STA associated with STA 2202. STA 2202 and STA 2204 may each comprise a multi-link device (MLD).

[0282] It is assumed in example 2200 that STA 2204 implements the power save (PS) mode illustrated in FIG. 22, which may be denoted as a dynamic PS mode or a low power listening (LPL) mode.

[0283] In an implementation, STA 2204 implementing the PS mode illustrated in FIG. 22 may be in a first power state/mode of the PS mode or in a second power state/mode of the PS mode. The first power state/mode may be referred to as a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode. The second power state/mode may be referred to as a higher capability state/mode, a higher power receive state/mode or an awake state/mode. While in the first power state/mode, STA 2204 is capable of receiving PPDUs of a first category. While in the second power state/mode, STA 2204 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, STA 2204 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, STA 2204 is capable of receiving PPDUs of only the first category during the first power state/mode.

[0284] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 810 described above. In another implementation, the first category may include, additionally or alternatively, PPDUs having a data rate that is less than or equal to 24 Mbps, a bandwidth of 22 MHz, and/or a single spatial stream. The second category may include PPDUs having a format other than the non- HT PPDU format. For example, the second category may include PPDUs having a high throughput (HT) format such as HT mixed mode PPDU 820, a VHT format such as VHT PPDU 830, an HE PPDU such as HE SU PPDU 910, HE MU PPDU 920, or HE ER SU PPDU 930, an EHT PPDU such as EHT MU PPDU 1000, an ultra-high reliability (UHR) PPDU, or a physical layer version identifier field. In an implementation, PPDUs of second category may further include sounding NDPs described above, for example, a VHT NDP, an HE sounding NDP, and EHT sounding NDP 1500. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 24 Mbps, a bandwidth greater than 22 MHz, and/or a plurality of spatial streams.

[0285] STA 2204 may transition between the first power state/mode and the second power state/mode of the PS mode. In an implementation, to reduce the power consumption of STA 2204, the first power state/mode may correspond to a default state of the PS mode As such, STA 2204 may operate in the first power state/mode and may transition to the second power state/mode as needed.

[0286] Additionally, STA 2204 may support another mode of operation. The other mode may correspond to an active mode or to a power saving mode different than the PS mode illustrated in FIG. 22. The other mode may have one or more power state/modes. STA 2204 may be capable of receiving PPDUs of the first category and/or of the second category in any power state/mode of the other mode.

[0287] In an implementation, while in the first power state/mode, STA 2204 is capable of receiving data frames carried by PPDUs of the first category. In another implementation, while STA 2204 is capable of receiving PPDUs of the first category while in the first power state/mode, STA 2204 is not capable of receiving data frames carried by PPDUs of the first category while in the first power state/mode. In an implementation, while in the second power state/mode, STA 2204 is capable of receiving data frames carried by PPDUs of the first category or the second category.

[0288] It is assumed in example 2200 that STA 2202 supports an operation for transmitting beamformed data for use in association with a PS mode (hereinafter “PS mode operation for beamformed data transmission”). It is also assumed in example 2200 that STA 2204 supports an operation for receiving beamformed data for use in association with a PS mode (hereinafter “PS mode operation for beamformed data reception”). In an embodiment, STA 2202 may support non-TB sounding as described in FIG. 19. For example, STA 2202 may operate as a beamformer as described in FIG. 19. In an embodiment, STA 2204 may support non-TB sounding as described in FIG. 19. For example, STA 2204 may operate as a beamformee as described in FIG. 19.

[0289] As shown in FIG. 22, the procedure illustrated in example 2200 may begin with STA 2204 operating in the first power state/mode. In an implementation, the first power state/mode may be a default state of STA 2204. In an embodiment, as illustrated in example 2200, STA 2204 may transition from the first power state/mode to the second power state/mode in response to being requested by STA 2202. [0290] In example 2200, STA 2202 may have data buffered for transmission to STA 2204. STA 2202 may wish to transmit the buffered data to STA 2204 using beamforming. In an embodiment, based on information that STA 2204 is operating in the first power state/mode of the PS mode, STA 2202 may be configured to perform the PS mode operation for beamformed data transmission as described herein. In an implementation, STA 2202 may perform the PS mode operation for beamformed data transmission in association with the non-TB sounding before transmitting a PPDU (e.g., PPDU 2216) carrying the buffered data of STA 2104.

[0291] Specifically, in an embodiment, STA 2202 may transmit a frame 2206 to STA 2204 operating in the first power state/mode. In an example, frame 2206 may comprise an initial control frame (IGF) as described in FIG. 13. STA 2202 may perform EDCA to transmit frame 2206. In an embodiment, frame 2206 may request that STA 2204 transition from the first power state/mode to the second power state/mode. In an embodiment, frame 2206 may request that STA 2204 transition from the first power state/mode to the second power state/mode for/before/during a first time period. The first time period may comprise/correspond to a sounding sequence and/or coordinated transmission. The sounding sequence and/or the coordinated transmission may be performed by STA 2202 and another STA (e.g., AP STA) (not shown in FIG. 22). The sounding sequence may comprise a sequential sounding sequence or a joint sounding sequence. The coordinated transmission may comprise a multi-AP coordinated transmission, such as a multi-AP coordinated beamforming transmission.

[0292] In an embodiment, STA 2204 may transition, in response to frame 2206, from the first power state/mode to the second power state/mode. As shown in FIG. 22, on receiving frame 2206 from STA 2202, STA 2204 may initiate a transition from the first power state/mode to the second power state/mode at a time T 1 and respond with a frame 2208. In example, frame 2208 may comprise an initial response frame (ICR) as described in FIG. 13. In an implementation, AP operates in the second power state/mode between time T1 and a time T2.

[0293] In an embodiment, STA 2204 may determine, from frame 2206, a TXOP duration, a bandwidth, and/or a modulation and coding scheme (MCS) of a null data PPDU (NDP) 2212 (which is a PPDU of the second category) to be transmitted by STA 2202 after frame 2206. STA 2204 may turn on/enable receiver capabilities based on the bandwidth and MCS indicated in frame 2206. In an implementation, STA 2204 may use the TXOP duration and the bandwidth indicated in frame 2206 to reserve a suitable channel for NDP 2212. In an implementation, STA 2204 may perform a clear channel assessment (CCA) procedure over the channel to be used by STA 2202 for the transmission of NDP 2212. After a successful CCA procedure, STA 2204 may transmit frame 2208 to STA 2202. frame 2208 may be configured to reserve the channel to be used by STA 2202 for the transmission of NDP 2212. In an implementation, frame 2208 may be a clear-to- send (CTS) frame that indicates the channel to be used by STA 2202 for the transmission of NDP 2212. [0294] In an embodiment, on receiving frame 2208, STA 2202 may perform a PS mode operation for beamformed data transmission with STA 2204. In an example, STA 2202 may perform the PS mode operation for beamformed data transmission while STA 2204 operates in the second power state/mode In an embodiment, STA 2202 may transmit to STA 2204, while STA 2204 operates in the PS mode, a frame 2210 requesting/indicating that STA 2204 operate, during a first time period, in the first power state/mode of the PS mode. In an embodiment, frame 2210 may indicate the first time period. In an embodiment, the first time period may occur after STA 2204 transmits a feedback frame 2214 comprising feedback to STA 2202 (in response to NDP 2212). In an embodiment, the first time period may begin a short interframe space (SIPS) after STA 2202 receives feedback frame 2214. In an embodiment, the first time period may be used by STA 2202 to transmit PPDU 2216, while STA 2204 operates in the first power state/mode. As shown in FIG. 22, for example, the first time period may begin at time T2 and end at a time T3.

[0295] In an embodiment, frame 2210 may further announce NDP 2212 to be transmitted by STA 2202, for use by STA 2204 to generate the feedback. In an embodiment, frame 2210 may indicate that NDP 2212 is to be transmitted a SIPS after STA 2202 transmits frame 2210 to STA 2204. In an embodiment, frame 2210 may solicit the feedback from STA 2204. In an embodiment, the feedback may comprise a beamforming report or a channel quality indication (CQI) report. In an embodiment, the feedback may comprise feedback based on NDP 2212. In an embodiment, the feedback may comprise single user (SU) feedback, or channel quality indication (CQI) feedback.

[0296] In an embodiment, frame 2210 may solicit the beamforming report or the CQI report from STA 2204. In an example, frame 2210 may indicate a feedback type for use by STA 2204 to generate the beamforming report In an example, the feedback type may indicate SU feedback or CQI feedback.

[0297] In an embodiment, the SU feedback may comprise a compressed beamforming report. In an example, the compressed beamforming report may comprise average SNR of each spatial stream and compressed beamforming feedback matrices for use by STA 2202 to determine steering matrices for explicit feedback beamforming. In an embodiment, the CQI feedback may comprise a CQI report. In an example, the CQI report may comprise per-RU average SNRs of each spatial stream. In an implementation, each per- RU average SNR may comprise an arithmetic mean of the SNR in decibels over the subcarriers of a 26-tone RU for which feedback is being requested.

[0298] In an embodiment, frame 2210 may further indicate a subcarrier grouping, Ng, for use by STA 2204 to generate the beamforming report. In an example, the subcarrier grouping may be as described in FIG. 19 above.

[0299] In an embodiment, frame 2210 may further indicate a codebook size for use by STA 2204 to generate the beamforming report, when the feedback type indicates the CQI feedback. In an example, the codebook size may be as described in FIG. 19 above. [0300] In an embodiment, frame 2210 may further indicate a first identifier of STA 2204. In an embodiment, the first identifier of STA 2204 may comprise an association identifier (AID) of STA 2204.

[0301] In an embodiment, frame 2210 may be carried in a PPDU of the first category. In an implementation, frame 2210 may be carried in a PPDU using a non-HT duplicate format with a bandwidth of 40 MHz, 80 MHz, 160 MHz or 320 MHz. In an implementation, frame 2210 may include signaling indicating the PPDU bandwidth.

[0302] In an embodiment, frame 2210 may comprise a control frame. In an embodiment, frame 2210 may comprise an announcement frame. In an embodiment, frame 2210 may comprise a null data PPDU announcement (NDPA) frame. For example, the NDPA frame may comprise an UHR NDPA frame.

[0303] After transmitting frame 2210, STA 2202 may initiate transmission of NDP 2212. In an embodiment, STA 2202 may transmit NDP 2212 a SIPS after transmitting frame 2210. In an embodiment, NDP 2212 may be for estimation, by STA 2204, of the channel (used by STA 2202 transmitting NDP 2212) from STA 2202 to STA 2204. As shown in FIG. 22, STA 2202 may transmit NDP 2212 while STA 2204 operates in the second power state/mode. In an embodiment, NDP 2212 may comprise a PPDU of the second category.

[0304] After receiving NDP 2212, STA 2204 may generate the feedback based on NDP 2212. In an embodiment, STA 2204 may generate an estimate of the channel based on NDP 2212 and may generate the feedback based on the estimate. In an example, the feedback may comprise the SU feedback or the CQI feedback based on the feedback type as indicated in frame 2210. STA 2204 may generate a beamforming report or CQI report based on the feedback. In an example, the beamforming report may comprise the compressed beamforming report. In an embodiment, STA 2204 may transmit to STA 2202 feedback frame 2214 comprising the feedback. In an embodiment, STA 2204 may transmit to STA 2202 feedback frame 2214 in response to frame 2210. As shown in FIG. 22, STA 2204 may transmit feedback frame 2214 while STA 2204 operates in the second power state/mode. In an embodiment, feedback frame 2214 may comprise a management frame. In an example, the management frame may comprise an action frame. In an example, the action frame may comprise an action no ack frame. In an example, the action frame may comprise an EHT compressed beamforming/CQI frame as described in FIG. 18.

[0305] After receiving feedback frame 2214, STA 2202 may initiate transmission of PPDU 2216 to STA 2204. In an embodiment, STA 2202 may transmit PPDU 2216 to STA 2204 during the first time period and while STA 2204 operates in the second power state/mode. In an embodiment, STA 2202 may transmit PPDU 2216 to STA 2204 during the first time period a SIFS after receiving feedback frame 2214 from STA 2204 In an embodiment, PPDU 2216 may comprise a PPDU of the second category. In an embodiment, PPDU 2216 may carry a data frame. In an embodiment, PPDU 2216 may carry the buffered data for transmission to STA 2204 beamformed based on the feedback comprised in feedback frame 2214. In an embodiment, STA 2204 may transmit a block ack (BA) frame 2218 acknowledging the reception of PPDU 2216 while in the second power state/mode. In another embodiment, STA 2204 may transmit BA frame 2218 after returning to the first power state/mode. After transmitting BA frame 2218, STA 2204 may transition to the other mode of operation or may remain in the first power state/mode of the PS mode.

[0306] As shown in FIG. 22, based on STA 2204 being in the second power state/mode during the first time period, STA 2202 does not transmit an ICF before transmitting PPDU 2216 to STA 2204. Similarly, as STA 2204 operates in the second power state/mode during the first time period, STA 2204 does not transmit an ICR frame before receiving PPDU 2216. Communication overhead of the sounding procedure is thereby reduced. Additionally, after transmitting feedback frame 2214, STA 2204 may only need to operate in the second power state/mode during the first time period indicated in frame 2210. The benefits of supporting the PS mode may thus be better leveraged by STA 2204 during the sounding procedure.

[0307] FIG. 23 illustrates an example 2300 of a PS mode operation for beamformed data transmission according to an embodiment. Example 2300 is provided for the purpose of illustration only and is not limiting. As shown in FIG. 23, example 2300 may include a STA 2302 and a STA 2304. STA 2302 may comprise an AP STA. STA 2304 may comprise a non-AP STA associated with STA 2302. STA 2302 and STA 2304 may each comprise a multi-link device (MLD).

[0308] It is assumed in example 2300 that STA 2304 implements the power save (PS) mode illustrated in FIG. 23, which may be denoted as a dynamic PS mode or a low power listening (LPL) mode.

[0309] In an implementation, STA 2304 implementing the PS mode illustrated in FIG. 23 may be in a first power state/mode of the PS mode or in a second power state/mode of the PS mode. The first power state/mode may be referred to as a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode. The second power state/mode may be referred to as a higher capability state/mode, a higher power receive state/mode or an awake state/mode. While in the first power state/mode, STA 2304 is capable of receiving PPDUs of a first category. While in the second power state/mode, STA 2304 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, STA 2304 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, STA 2304 is capable of receiving PPDUs of only the first category during the first power state/mode.

[0310] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 810 described above. In another implementation, the first category may include, additionally or alternatively, PPDUs having a data rate that is less than or equal to 24 Mbps, a bandwidth of 23 MHz, and/or a single spatial stream. The second category may include PPDUs having a format other than the non- HT PPDU format. For example, the second category may include PPDUs having a high throughput (HT) format such as HT mixed mode PPDU 820, a VHT format such as VHT PPDU 830, an HE PPDU such as HE SU PPDU 910, HE MU PPDU 920, or HE ER SU PPDU 930, an EHT PPDU such as EHT MU PPDU 1000, an ultra-high reliability (UHR) PPDU, or a physical layer version identifier field. In an implementation, PPDUs of second category may further include sounding NDPs described above, for example, a VHT NDP, an HE sounding NDP, and EHT sounding NDP 1500. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 24 Mbps, a bandwidth greater than 23 MHz, and/or a plurality of spatial streams.

[0311] STA 2304 may transition between the first power state/mode and the second power state/mode of the PS mode. In an implementation, to reduce the power consumption of STA 2304, the first power state/mode may correspond to a default state of the PS mode. As such, STA 2304 may operate in the first power state/mode and may transition to the second power state/mode as needed.

[0312] Additionally, STA 2304 may support another mode of operation. The other mode may correspond to an active mode or to a power saving mode different than the PS mode illustrated in FIG. 23. The other mode may have one or more power state/modes. STA 2304 may be capable of receiving PPDUs of the first category and/or of the second category in any power state/mode of the other mode.

[0313] In an implementation, while in the first power state/mode, STA 2304 is capable of receiving data frames carried by PPDUs of the first category. In another implementation, while STA 2304 is capable of receiving PPDUs of the first category while in the first power state/mode, STA 2304 is not capable of receiving data frames carried by PPDUs of the first category while in the first power state/mode. In an implementation, while in the second power state/mode, STA 2304 is capable of receiving data frames carried by PPDUs of the first category or the second category.

[0314] It is assumed in example 2300 that STA 2302 supports an operation for transmitting beamformed data for use in association with a PS mode (hereinafter “PS mode operation for beamformed data transmission”). It is also assumed in example 2300 that STA 2304 supports an operation for receiving beamformed data for use in association with a PS mode (hereinafter “PS mode operation for beamformed data reception”). In an embodiment, STA 2302 may support non-TB sounding as described in FIG. 19. For example, STA 2302 may operate as a beamformer as described in FIG. 19. In an embodiment, STA 2304 may support non-TB sounding as described in FIG. 19. For example, STA 2304 may operate as a beamformee as described in FIG. 19.

[0315] As shown in FIG. 23, the procedure illustrated in example 2300 may begin with STA 2304 operating in the first power state/mode. In an implementation, the first power state/mode may be a default state of STA 2304. In an embodiment, as illustrated in example 2300, STA 2304 may transition from the first power state/mode to the second power state/mode in response to being requested by STA 2302

[0316] In example 2300, STA 2302 may have data buffered for transmission to STA 2304. STA 2302 may wish to transmit the buffered data to STA 2304 using beamforming. In an embodiment, based on information that STA 2304 is operating in the first power state/mode of the PS mode, STA 2302 may be configured to perform the PS mode operation for beamformed data transmission as described herein. In an implementation, STA 2302 may perform the PS mode operation for beamformed data transmission in association with the non-TB sounding before transmitting a PPDU (e.g., PPDU 2316) carrying the buffered data of STA 2104.

[0317] Specifically, in an embodiment, STA 2302 may transmit a frame 2306 to STA 2304 operating in the first power state/mode. In an example, frame 2306 may comprise an initial control frame (ICF) as described in FIG. 13. STA 2302 may perform EDCA to transmit frame 2306. In an embodiment, frame 2306 may request that STA 2304 transition from the first power state/mode to the second power state/mode. In an embodiment, frame 2306 may request that STA 2304 transition from the first power state/mode to the second power state/mode for/before/during a first time period. The first time period may comprise/correspond to a sounding sequence and/or coordinated transmission. The sounding sequence and/or the coordinated transmission may be performed by STA 2302 and another STA (e.g., AP STA) (not shown in FIG. 23). The sounding sequence may comprise a sequential sounding sequence or a joint sounding sequence. The coordinated transmission may comprise a multi-AP coordinated transmission, such as a multi-AP coordinated beamforming transmission.

[0318] In an embodiment, STA 2304 may transition, in response to frame 2306, from the first power state/mode to the second power state/mode. As shown in FIG. 23, on receiving frame 2306 from STA 2302, STA 2304 may initiate a transition from the first power state/mode to the second power state/mode at a time T 1 and respond with a frame 2308. In example, frame 2308 may comprise an initial response frame (ICR) as described in FIG. 13. In an implementation, AP operates in the second power state/mode between time T1 and a time T2.

[0319] In an embodiment, STA 2304 may determine, from frame 2306, a TXOP duration, a bandwidth, and/or a modulation and coding scheme (MCS) of a frame 2312 (which is a PPDU of the second category) to be transmitted by STA 2302 after frame 2306. Frame 2312 may comprise a null data PPDU (NDP). STA 2304 may turn on/enable receiver capabilities based on the bandwidth and MCS indicated in frame 2306. In an implementation, STA 2304 may use the TXOP duration and the bandwidth indicated in frame 2306 to reserve a suitable channel for frame 2312. In an implementation, STA 2304 may perform a clear channel assessment (CCA) procedure over the channel to be used by STA 2302 for the transmission of frame 2312. After a successful CCA procedure, STA 2304 may transmit frame 2308 to STA 2302. frame 2308 may be configured to reserve the channel to be used by STA 2302 for the transmission of frame 2312. In an implementation, frame 2308 may be a clear-to-send (CTS) frame that indicates the channel to be used by STA 2302 for the transmission of frame 2312.

[0320] In an embodiment, on receiving frame 2308, STA 2302 may perform a PS mode operation for beamformed data transmission with STA 2304. In an example, STA 2302 may perform the PS mode operation for beamformed data transmission while STA 2304 operates in the second power state/mode.

[0321] In an embodiment, STA 2302 may transmit to STA 2304 a frame 2310 announcing frame 2312 to be transmitted by STA 2302, for use by STA 2304 to generate feedback. In an embodiment, frame 2310 may indicate that frame 2312 is to be transmitted a SIFS after STA 2302 transmits frame 2310 to STA 2304. In an embodiment, frame 2310 may solicit the feedback from STA 2304. In an embodiment, the feedback may comprise a beamforming report or a channel quality indication (CQI) report. In an embodiment, the feedback may comprise feedback based on frame 2312. In an embodiment, the feedback may comprise single user (SU) feedback, or channel quality indication (CQI) feedback.

[0322] In an embodiment, frame 2310 may solicit the beamforming report or the CQI report from STA 2304. In an example, frame 2310 may indicate a feedback type for use by STA 2304 to generate the beamforming report. In an example, the feedback type may indicate SU feedback or CQI feedback.

[0323] In an embodiment, the SU feedback may comprise a compressed beamforming report. In an example, the compressed beamforming report may comprise average SNR of each spatial stream and compressed beamforming feedback matrices for use by STA 2302 to determine steering matrices for explicit feedback beamforming In an embodiment, the CQI feedback may comprise a CQI report. In an example, the CQI report may comprise per-RU average SNRs of each spatial stream. In an implementation, each per- RU average SNR may comprise an arithmetic mean of the SNR in decibels over the subcarriers of a 26-tone RU for which feedback is being requested.

[0324] In an embodiment, frame 2310 may further indicate a subcarrier grouping, Ng, for use by STA 2304 to generate the beamforming report. In an example, the subcarrier grouping may be as described in FIG. 19 above.

[0325] In an embodiment, frame 2310 may further indicate a codebook size for use by STA 2304 to generate the beamforming report, when the feedback type indicates the CQI feedback. In an example, the codebook size may be as described in FIG. 19 above.

[0326] In an embodiment, frame 2310 may further indicate a first identifier of STA 2304. In an embodiment, the first identifier of STA 2304 may comprise an association identifier (AID) of STA 2304.

[0327] In an embodiment, frame 2310 may be carried in a PPDU of the first category. In an implementation, frame 2310 may be carried in a PPDU using a non-HT duplicate format with a bandwidth of 40 MHz, 80 MHz, 160 MHz or 320 MHz. In an implementation, frame 2310 may include signaling indicating the PPDU bandwidth.

[0328] In an embodiment, frame 2310 may comprise a control frame. In an embodiment, frame 2310 may comprise an announcement frame. In an embodiment, frame 2310 may comprise an NDPA frame. For example, the NDPA frame may comprise an UHR NDPA frame.

[0329] After transmitting frame 2310, STA 2302 may initiate transmission of frame 2312.

[0330] In an embodiment, STA 2302 may transmit to STA 2304, while STA 2304 operates in the PS mode, frame 2312 requesting/indicating that STA 2304 operate, during a first time period, in the first power state/mode of the PS mode. In an embodiment, frame 2312 may indicate the first time period. In an embodiment, the first time period may occur after STA 2304 transmits feedback frame 2314 comprising the feedback to STA 2302 (in response to frame 2312). In an embodiment, the first time period may begin a short interframe space (SIFS) after STA 2302 receives feedback frame 2314. In an embodiment, the first time period may be used by STA 2302 to transmit PPDU 2316, while STA 2304 operates in the first power state/mode. As shown in FIG. 23, for example, the first time period may begin at time T2 and end at a time T3.

[0331] In an embodiment, a PHY header of frame 2310 may indicate the first time period. In an embodiment, the PHY header of frame 2310 may comprise a signal field indicating the first time period. In an embodiment, the signal field may comprise a U-SIG field as described in FIG. 15 or an UHR-SIG field.

[0332] In an embodiment, STA 2302 may transmit frame 2312 a SIFS after transmitting frame 2310. In an embodiment, frame 2312 may be for estimation, by STA 2304, of the channel (used by STA 2302 transmitting frame 2312) from STA 2302 to STA 2304. As shown in FIG. 23, STA 2302 may transmit frame 2312 while STA 2304 operates in the second power state/mode. In an embodiment, frame 2312 may comprise a NDP. In an embodiment, the NDP may comprise a PPDU of the second category.

[0333] After receiving frame 2312, STA 2304 may generate the feedback based on frame 2312. In an embodiment, STA 2304 may generate an estimate of the channel based on frame 2312 and may generate the feedback based on the estimate. In an example, the feedback may comprise the SU feedback or the CQI feedback based on the feedback type as indicated in frame 2310. STA 2304 may generate a beamforming report or CQI report based on the feedback. In an example, the beamforming report may comprise the compressed beamforming report. In an embodiment, STA 2304 may transmit to STA 2302 feedback frame 2314 comprising the feedback. In an embodiment, STA 2304 may transmit to STA 2302 feedback frame 2314 in response to frame 2310. As shown in FIG. 23, STA 2304 may transmit feedback frame 2314 while STA 2304 operates in the second power state/mode. In an embodiment, feedback frame 2314 may comprise a management frame. In an example, the management frame may comprise an action frame. In an example, the action frame may comprise an action no ack frame. In an example, the action frame may comprise an EHT compressed beamforming/CQI frame as described in FIG. 18.

[0334] After receiving feedback frame 2314, STA 2302 may initiate transmission of PPDU 2316 to STA 2304. In an embodiment, STA 2302 may transmit PPDU 2316 to STA 2304 during the first time period and while STA 2304 operates in the second power state/mode. In an embodiment, STA 2302 may transmit PPDU 2316 to STA 2304 during the first time period a SIFS after receiving feedback frame 2314 from STA 2304. In an embodiment, PPDU 2316 may comprise a PPDU of the second category. In an embodiment, PPDU 2316 may carry a data frame. In an embodiment, PPDU 2316 may carry the buffered data for transmission to STA 2304 beamformed based on the feedback comprised in feedback frame 2314. In an embodiment, STA 2304 may transmit a block ack (BA) frame 2318 acknowledging the reception of PPDU 2316 while in the second power state/mode. In another embodiment, STA 2304 may transmit BA frame 2318 after returning to the first power state/mode. After transmitting BA frame 2318, STA 2304 may transition to the other mode of operation or may remain in the first power state/mode of the PS mode.

[0335] As shown in FIG. 23, based on STA 2304 being in the second power state/mode during the first time period, STA 2302 does not transmit an ICF before transmitting PPDU 2316 to STA 2304. Similarly, as STA 2304 operates in the second power state/mode during the first time period, STA 2304 does not transmit an ICR frame before receiving PPDU 2316. Communication overhead of the sounding procedure is thereby reduced. Additionally, after transmitting feedback frame 2314, STA 2304 may only need to operate in the second power state/mode during the first time period indicated in frame 2312. The benefits of supporting the PS mode may thus be better leveraged by STA 2304 during the sounding procedure.

[0336] FIG. 24 illustrates an example 2400 of a PS mode operation for beamformed data transmission according to an embodiment. Example 2400 is provided for the purpose of illustration only and is not limiting. As shown in FIG 24, example 2400 may include a STA 2402 and a STA 2404. STA 2402 may comprise an AP STA. STA 2404 may comprise a non-AP STA associated with STA 2402. STA 2402 and STA 2404 may each comprise a multi-link device (MLD).

[0337] It is assumed in example 2400 that STA 2404 implements the power save (PS) mode illustrated in FIG. 24, which may be denoted as a dynamic PS mode or a low power listening (LPL) mode.

[0338] In an implementation, STA 2404 implementing the PS mode illustrated in FIG. 24 may be in a first power state/mode of the PS mode or in a second power state/mode of the PS mode. The first power state/mode may be referred to as a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode. The second power state/mode may be referred to as a higher capability state/mode, a higher power receive state/mode or an awake state/mode. While in the first power state/mode, STA 2404 is capable of receiving PPDUs of a first category. While in the second power state/mode, STA 2404 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, STA 2404 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, STA 2404 is capable of receiving PPDUs of only the first category during the first power state/mode.

[0339] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 810 described above. In another implementation, the first category may include, additionally or alternatively, PPDUs having a data rate that is less than or equal to 24 Mbps, a bandwidth of 24 MHz, and/or a single spatial stream. The second category may include PPDUs having a format other than the non- HT PPDU format. For example, the second category may include PPDUs having a high throughput (HT) format such as HT mixed mode PPDU 820, a VHT format such as VHT PPDU 830, an HE PPDU such as HE SU PPDU 910, HE MU PPDU 920, or HE ER SU PPDU 930, an EHT PPDU such as EHT MU PPDU 1000, an ultra-high reliability (UHR) PPDU, or a physical layer version identifier field. In an implementation, PPDUs of second category may further include sounding NDPs described above, for example, a VHT NDP, an HE sounding NDP, and EHT sounding NDP 1500. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 24 Mbps, a bandwidth greater than 24 MHz, and/or a plurality of spatial streams.

[0340] STA 2404 may transition between the first power state/mode and the second power state/mode of the PS mode. In an implementation, to reduce the power consumption of STA 2404, the first power state/mode may correspond to a default state of the PS mode. As such, STA 2404 may operate in the first power state/mode and may transition to the second power state/mode as needed.

[0341] Additionally, STA 2404 may support another mode of operation. The other mode may correspond to an active mode or to a power saving mode different than the PS mode illustrated in FIG. 24. The other mode may have one or more power state/modes. STA 2404 may be capable of receiving PPDUs of the first category and/or of the second category in any power state/mode of the other mode.

[0342] In an implementation, while in the first power state/mode, STA 2404 is capable of receiving data frames carried by PPDUs of the first category. In another implementation, while STA 2404 is capable of receiving PPDUs of the first category while in the first power state/mode, STA 2404 is not capable of receiving data frames carried by PPDUs of the first category while in the first power state/mode. In an implementation, while in the second power state/mode, STA 2404 is capable of receiving data frames carried by PPDUs of the first category or the second category.

[0343] It is assumed in example 2400 that STA 2402 supports an operation for transmitting beamformed data for use in association with a PS mode (hereinafter “PS mode operation for beamformed data transmission”). It is also assumed in example 2400 that STA 2404 supports an operation for receiving beamformed data for use in association with a PS mode (hereinafter “PS mode operation for beamformed data reception"). In an embodiment, STA 2402 may support non-TB sounding as described in FIG. 19. For example, STA 2402 may operate as a beamformer as described in FIG. 19. In an embodiment, STA 2404 may support non-TB sounding as described in FIG. 19. For example, STA 2404 may operate as a beamformee as described in FIG. 19.

[0344] As shown in FIG. 24, the procedure illustrated in example 2400 may begin with STA 2404 operating in the first power state/mode. In an implementation, the first power state/mode may be a default state of STA 2404. In an embodiment, as illustrated in example 2400, STA 2404 may transition from the first power state/mode to the second power state/mode in response to being requested by STA 2402.

[0345] In example 2400, STA 2402 may have data buffered for transmission to STA 2404. STA 2402 may wish to transmit the buffered data to STA 2404 using beamforming. In an embodiment, based on information that STA 2404 is operating in the first power state/mode of the PS mode, STA 2402 may be configured to perform the PS mode operation for beamformed data transmission as described herein. In an implementation, STA 2402 may perform the PS mode operation for beamformed data transmission in association with the non-TB sounding before transmitting a PPDU (e.g., PPDU 2416) carrying the buffered data of STA 2104.

[0346] Specifically, in an embodiment, STA 2402 may transmit a frame 2406 to STA 2404 operating in the first power state/mode. In an example, frame 2406 may comprise an initial control frame (ICF) as described in FIG. 13. STA 2402 may perform EDCA to transmit frame 2406. In an embodiment, frame 2406 may request that STA 2404 transition from the first power state/mode to the second power state/mode. In an embodiment, frame 2406 may request that STA 2404 transition from the first power state/mode to the second power state/mode for/before/during a first time period. The first time period may comprise/correspond to a sounding sequence and/or coordinated transmission. The sounding sequence and/or the coordinated transmission may be performed by STA 2402 and another STA (e.g., AP STA) (not shown in FIG. 24). The sounding sequence may comprise a sequential sounding sequence or a joint sounding sequence. The coordinated transmission may comprise a multi-AP coordinated transmission, such as a multi-AP coordinated beamforming transmission.

[0347] In an embodiment, STA 2404 may transition, in response to frame 2406, from the first power state/mode to the second power state/mode. As shown in FIG. 24, on receiving frame 2406 from STA 2402, STA 2404 may initiate a transition from the first power state/mode to the second power state/mode at a time T 1 and respond with a frame 2408. In example, frame 2408 may comprise an initial response frame (ICR) as described in FIG. 13. In an implementation, AP operates in the second power state/mode between time T1 and a time T2.

[0348] In an embodiment, STA 2404 may determine, from frame 2406, a TXOP duration, a bandwidth, and/or a modulation and coding scheme (MCS) of a null data PPDU (NDP) 2412 (which is a PPDU of the second category) to be transmitted by STA 2402 after frame 2406. STA 2404 may turn on/enable receiver capabilities based on the bandwidth and MCS indicated in frame 2406. In an implementation, STA 2404 may use the TXOP duration and the bandwidth indicated in frame 2406 to reserve a suitable channel for NDP 2412. In an implementation, STA 2404 may perform a clear channel assessment (CCA) procedure over the channel to be used by STA 2402 for the transmission of NDP 2412. After a successful CCA procedure, STA 2404 may transmit frame 2408 to STA 2402. frame 2408 may be configured to reserve the channel to be used by STA 2402 for the transmission of NDP 2412. In an implementation, frame 2408 may be a clear-to- send (CTS) frame that indicates the channel to be used by STA 2402 for the transmission of NDP 2412.

[0349] In an embodiment, on receiving frame 2408, STA 2402 may perform a PS mode operation for beamformed data transmission with STA 2404. In an example, STA 2402 may perform the PS mode operation for beamformed data transmission while STA 2404 operates in the second power state/mode. In an embodiment, STA 2402 may transmit to STA 2404, while STA 2404 operates in the PS mode, a frame 2410 requesting/indicating that STA 2404 operate, during a first time period, in the first power state/mode of the PS mode. In an embodiment, frame 2410 may indicate the first time period. In an embodiment, the first time period may occur after STA 2404 transmits a feedback frame 2414 comprising feedback to STA 2402 (in response to NDP 2412). In an embodiment, the first time period may begin a short interframe space (SIFS) after STA 2402 receives feedback frame 2414. In an embodiment, the first time period may be used by STA 2402 to transmit PPDU 2416, while STA 2404 operates in the first power state/mode. As shown in FIG. 24, for example, the first time period may begin at a time T3 and end at a time T4.

[0350] In an embodiment, frame 2410 may further indicate a second time period. In an embodiment, frame 2410 may further recommend that the STA 2404 operate in the first power state/mode of the PS mode during the second time period. In an embodiment, the second time period may begin after STA 2402 transmits NDP 2412 and end before the first time period (not shown in FIG. 24). For example, the second time period may extend between transmitting NDP 2412 and transmitting PPDU 2416. In an embodiment, the second time period may begin after STA 2404 transmits feedback frame 2414. For example, the second time period may begin after STA 2402 receives feedback frame 2414 and end before STA 2402 transmits PPDU 2416. As shown in FIG. 24, for example, the second time period may begin at a time T2 and end at a time T3. In another embodiment, the second time period may end before STA 2404 transmits feedback frame 2414 (not shown in FIG. 24). For example, the second time period may begin after STA 2402 transmits NDP 2412 and end before STA 2402 receives feedback frame 2414. In another embodiment, the second time period may comprise a first portion and a second portion (not shown in FIG. 24). In an example, the first portion of the second time period may begin after STA 2402 transmits NDP 2412 and ends before STA 2404 transmits feedback frame 2414. The second portion of the second time period may begin after STA 2404 transmits feedback frame 2414 and ends before the first time period. For example, the first portion and the second portion of the second time period may be two non-contiguous portions around STA 2404 transmitting feedback frame 2414.

[0351] In an embodiment, frame 2410 may further announce NDP 2412 to be transmitted by STA 2402, for use by STA 2404 to generate the feedback. In an embodiment, frame 2410 may indicate that NDP 2412 is to be transmitted a SIFS after STA 2402 transmits frame 2410 to STA 2404. In an embodiment, frame 2410 may solicit the feedback from STA 2404. In an embodiment, the feedback may comprise a beamforming report or a channel quality indication (CQI) report. In an embodiment, the feedback may comprise feedback based on NDP 2412. In an embodiment, the feedback may comprise single user (SU) feedback, or channel quality indication (CQI) feedback.

[0352] In an embodiment, frame 2410 may solicit the beamforming report or the CQI report from STA 2404. In an example, frame 2410 may indicate a feedback type for use by STA 2404 to generate the beamforming report. In an example, the feedback type may indicate SU feedback or CQI feedback.

[0353] In an embodiment, the SU feedback may comprise a compressed beamforming report. In an example, the compressed beamforming report may comprise average SNR of each spatial stream and compressed beamforming feedback matrices for use by STA 2402 to determine steering matrices for explicit feedback beamforming. In an embodiment, the CQI feedback may comprise a CQI report. In an example, the CQI report may comprise per-RU average SNRs of each spatial stream. In an implementation, each per- RU average SNR may comprise an arithmetic mean of the SNR in decibels over the subcarriers of a 26-tone RU for which feedback is being requested.

[0354] In an embodiment, frame 2410 may further indicate a subcarrier grouping, Ng, for use by STA 2404 to generate the beamforming report. In an example, the subcarrier grouping may be as described in FIG. 19 above.

[0355] In an embodiment, frame 2410 may further indicate a codebook size for use by STA 2404 to generate the beamforming report, when the feedback type indicates the CQI feedback. In an example, the codebook size may be as described in FIG. 19 above.

[0356] In an embodiment, frame 2410 may further indicate a first identifier of STA 2404. In an embodiment, the first identifier of STA 2404 may comprise an association identifier (AID) of STA 2404.

[0357] In an embodiment, frame 2410 may be carried in a PPDU of the first category. In an implementation, frame 2410 may be carried in a PPDU using a non-HT duplicate format with a bandwidth of 40 MHz, 80 MHz, 160 MHz or 320 MHz. In an implementation, frame 2410 may include signaling indicating the PPDU bandwidth.

[0358] In an embodiment, frame 2410 may comprise a control frame. In an embodiment, frame 2410 may comprise an announcement frame. In an embodiment, frame 2410 may comprise an null data PPDU announcement (NDPA) frame. For example, the NDPA frame may comprise an UHR NDPA frame.

[0359] After transmitting frame 2410, STA 2402 may initiate transmission of NDP 2412. In an embodiment, STA 2402 may transmit NDP 2412 a SIFS after transmitting frame 2410. In an embodiment, NDP 2412 may be for estimation, by STA 2404, of the channel (used by STA 2402 transmitting NDP 2412) from STA 2402 to STA 2404. As shown in FIG. 24, STA 2402 may transmit NDP 2412 while STA 2404 operates in the second power state/mode. In an embodiment, NDP 2412 may comprise a PPDU of the second category.

[0360] After receiving NDP 2412, STA 2404 may generate the feedback based on NDP 2412. In an embodiment, STA 2404 may generate an estimate of the channel based on NDP 2412 and may generate the feedback based on the estimate. In an example, the feedback may comprise the SU feedback or the CQI feedback based on the feedback type as indicated in frame 2410. STA 2404 may generate a beamforming report or CQI report based on the feedback. In an example, the beamforming report may comprise the compressed beamforming report. In an embodiment, STA 2404 may transmit to STA 2402 feedback frame 2414 comprising the feedback. In an embodiment, STA 2404 may transmit to STA 2402 feedback frame 2414 in response to frame 2410. As shown in FIG. 24, STA 2404 may transmit feedback frame 2414 while STA 2404 operates in the second power state/mode. In an embodiment, feedback frame 2414 may comprise a management frame. In an example, the management frame may comprise an action frame. In an example, the action frame may comprise an action no ack frame. In an example, the action frame may comprise an EHT compressed beamforming/CQI frame as described in FIG. 18.

[0361] As shown in FIG. 24, STA 2404 may transition/return from the second power state/mode to the first power state/mode at the beginning of the second time period that begins after STA 2404 transmits feedback frame 2414. In an embodiment, STA 2404 may operate in the first power state/mode during the second time period. The second period may end ends at time T3, before STA 2402 transmits PPDU 2416. In an embodiment, STA 2404 may transition from the first power state/mode to the second power state/mode at the end of the second time period, e.g., time T3.

[0362] As shown in FIG. 24, STA 2402 may initiate transmission of PPDU 2416 to STA 2404 at the beginning of the first time period, e.g., time T3. In an embodiment, STA 2402 may transmit PPDU 2416 to STA 2404 during the first time period and while STA 2404 operates in the second power state/mode. In an embodiment, STA 2402 may transmit PPDU 2416 to STA 2404 during the first time period a SIFS after receiving feedback frame 2414 from STA 2404. In an embodiment, PPDU 2416 may comprise a PPDU of the second category. In an embodiment, PPDU 2416 may carry a data frame. In an embodiment, PPDU 2416 may carry the buffered data for transmission to STA 2404 beamformed based on the feedback comprised in feedback frame 2414. In an embodiment, STA 2404 may transmit a block ack (BA) frame 2418 acknowledging the reception of PPDU 2416 while in the second power state/mode. In another embodiment, STA 2404 may transmit BA frame 2418 after returning to the first power state/mode. After transmitting BA frame 2418, STA 2404 may transition to the other mode of operation or may remain in the first power state/mode of the PS mode.

[0363] In an embodiment (not shown in FIG. 24), STA 2404 may transition/return from the second power state/mode to the first power state/mode at the beginning of the second time period indicated in frame 2410. In an embodiment, the second time period may begin after STA 2404 receives NDP 2412 and ends before STA 2404 transmits feedback frame 2414. In an example, STA 2404 may operate in the first power state/mode during the second time period.

[0364] In another embodiment (not shown in FIG. 24), STA 2404 may transition/return from the second power state/mode to the first power state/mode at the beginning of the first portion of the second time period indicated in frame 2410. In an example, the first portion of the second time period may begin after STA 2404 receives NDP 2412 and ends before STA 2404 transmits feedback frame 2414. STA 2404 may operate in the first power state/mode during the first portion of the second time period In an embodiment, at the end of the first portion of the second time period, STA 2404 may transition to the second power state/mode and transmit feedback frame 2414. In an embodiment, STA 2404 may transition/return from the second power state/mode to the first power state/mode at the beginning of the second portion of the second time period indicated in frame 2410. In an example, the second portion of the second time period may begin after STA 2404 transmits feedback frame 2414 and ends before STA 2404 receives PPDU 2416. In an embodiment, STA 2404 may operate in the first power state/mode during the second portion of the second time period. In an embodiment, at the end of the second portion of the second time period, STA 2404 may transition to the second power state/mode and receive PPDU 2416.

[0365] As shown in FIG. 24, based on STA 2404 being in the second power state/mode during the first time period, STA 2402 does not transmit an IGF before transmitting PPDU 2416 to STA 2404. Similarly, as STA 2404 operates in the second power state/mode during the first time period, STA 2404 does not transmit an ICR frame before receiving PPDU 2416. Communication overhead of the sounding procedure is thereby reduced. Additionally, after transmitting feedback frame 2414, STA 2404 may only need to operate in the second power state/mode during the first time period indicated in frame 2410. Specifically, as shown in FIG. 24, STA 2404 may operate in the first power state/mode during the second time period. Power consumption of STA 2404 may thus be further reduced. The benefits of supporting the PS mode may thus be better leveraged by STA 2404 during the sounding procedure.

[0366] FIG. 25 illustrates an example 2500 of a PS mode operation for beamformed data transmission according to an embodiment. Example 2500 is provided for the purpose of illustration only and is not limiting. As shown in FIG. 25, example 2500 may include a STA 2502 and a STA 2504. STA 2502 may comprise an AP STA. STA 2504 may comprise a non-AP STA associated with STA 2502. STA 2502 and STA 2504 may each comprise a multi-link device (MLD).

[0367] It is assumed in example 2500 that STA 2504 implements the power save (PS) mode illustrated in FIG. 25, which may be denoted as a dynamic PS mode or a low power listening (LPL) mode.

[0368] In an implementation, STA 2504 implementing the PS mode illustrated in FIG. 25 may be in a first power state/mode of the PS mode or in a second power state/mode of the PS mode. The first power state/mode may be referred to as a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode. The second power state/mode may be referred to as a higher capability state/mode, a higher power receive state/mode or an awake state/mode. While in the first power state/mode, STA 2504 is capable of receiving PPDUs of a first category. While in the second power state/mode, STA 2504 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, STA 2504 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, STA 2504 is capable of receiving PPDUs of only the first category during the first power state/mode.

[0369] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 810 described above. In another implementation, the first category may include, additionally or alternatively, PPDUs having a data rate that is less than or equal to 25 Mbps, a bandwidth of 25 MHz, and/or a single spatial stream. The second category may include PPDUs having a format other than the non- HT PPDU format. For example, the second category may include PPDUs having a high throughput (HT) format such as HT mixed mode PPDU 820, a VHT format such as VHT PPDU 830, an HE PPDU such as HE SU PPDU 910, HE MU PPDU 920, or HE ER SU PPDU 930, an EHT PPDU such as EHT MU PPDU 1000, an ultra-high reliability (UHR) PPDU, or a physical layer version identifier field. In an implementation, PPDUs of second category may further include sounding NDPs described above, for example, a VHT NDP, an HE sounding NDP, and EHT sounding NDP 1500. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 25 Mbps, a bandwidth greater than 25 MHz, and/or a plurality of spatial streams.

[0370] STA 2504 may transition between the first power state/mode and the second power state/mode of the PS mode. In an implementation, to reduce the power consumption of STA 2504, the first power state/mode may correspond to a default state of the PS mode. As such, STA 2504 may operate in the first power state/mode and may transition to the second power state/mode as needed.

[0371] Additionally, STA 2504 may support another mode of operation. The other mode may correspond to an active mode or to a power saving mode different than the PS mode illustrated in FIG. 25. The other mode may have one or more power state/modes. STA 2504 may be capable of receiving PPDUs of the first category and/or of the second category in any power state/mode of the other mode.

[0372] In an implementation, while in the first power state/mode, STA 2504 is capable of receiving data frames carried by PPDUs of the first category. In another implementation, while STA 2504 is capable of receiving PPDUs of the first category while in the first power state/mode, STA 2504 is not capable of receiving data frames carried by PPDUs of the first category while in the first power state/mode. In an implementation, while in the second power state/mode, STA 2504 is capable of receiving data frames carried by PPDUs of the first category or the second category.

[0373] It is assumed in example 2500 that STA 2502 supports an operation for transmitting beamformed data for use in association with a PS mode (hereinafter "PS mode operation for beamformed data transmission"). It is also assumed in example 2500 that STA 2504 supports an operation for receiving beamformed data for use in association with a PS mode (hereinafter “PS mode operation for beamformed data reception”). In an embodiment, STA 2502 may support non-TB sounding as described in FIG. 19. For example, STA 2502 may operate as a beamformer as described in FIG. 19. In an embodiment, STA 2504 may support non-TB sounding as described in FIG. 19. For example, STA 2504 may operate as a beamformee as described in FIG. 19.

[0374] As shown in FIG. 25, the procedure illustrated in example 2500 may begin with STA 2504 operating in the first power state/mode. In an implementation, the first power state/mode may be a default state of STA 2504. In an embodiment, as illustrated in example 2500, STA 2504 may transition from the first power state/mode to the second power state/mode in response to being requested by STA 2502.

[0375] In example 2500, STA 2502 may have data buffered for transmission to STA 2504. STA 2502 may wish to transmit the buffered data to STA 2504 using beamforming. In an embodiment, based on information that STA 2504 is operating in the first power state/mode of the PS mode, STA 2502 may be configured to perform the PS mode operation for beamformed data transmission as described herein. In an implementation, STA 2502 may perform the PS mode operation for beamformed data transmission in association with the non-TB sounding before transmitting a PPDU (e.g., PPDU 2518) carrying the buffered data of STA 2104.

[0376] Specifically, in an embodiment, STA 2502 may transmit a frame 2506 to STA 2504 operating in the first power state/mode. In an example, frame 2506 may comprise an initial control frame (IGF) as described in FIG. 13. STA 2502 may perform EDCA to transmit frame 2506. In an embodiment, frame 2506 may request that STA 2504 transition from the first power state/mode to the second power state/mode. In an embodiment, frame 2506 may request that STA 2504 transition from the first power state/mode to the second power state/mode for/before/during a first time period. The first time period may comprise/correspond to a sounding sequence and/or coordinated transmission. The sounding sequence and/or the coordinated transmission may be performed by STA 2502 and another STA (e.g., AP STA) (not shown in FIG 25). The sounding sequence may comprise a sequential sounding sequence or a joint sounding sequence. The coordinated transmission may comprise a multi-AP coordinated transmission, such as a multi-AP coordinated beamforming transmission.

[0377] In an embodiment, STA 2504 may transition, in response to frame 2506, from the first power state/mode to the second power state/mode. As shown in FIG. 25, on receiving frame 2506 from STA 2502, STA 2504 may initiate a transition from the first power state/mode to the second power state/mode at a time T 1 and respond with a frame 2508. In example, frame 2508 may comprise an initial response frame (ICR) as described in FIG. 13. In an implementation, AP operates in the second power state/mode between time T1 and a time T2.

[0378] In an embodiment, STA 2504 may determine, from frame 2506, a TXOP duration, a bandwidth, and/or a modulation and coding scheme (MCS) of a null data PPDU (NDP) 2512 (which is a PPDU of the second category) to be transmitted by STA 2502 after frame 2506. STA 2504 may turn on/enable receiver capabilities based on the bandwidth and MCS indicated in frame 2506. In an implementation, STA 2504 may use the TXOP duration and the bandwidth indicated in frame 2506 to reserve a suitable channel for NDP 2512. In an implementation, STA 2504 may perform a clear channel assessment (CCA) procedure over the channel to be used by STA 2502 for the transmission of NDP 2512. After a successful CCA procedure, STA 2504 may transmit frame 2508 to STA 2502. frame 2508 may be configured to reserve the channel to be used by STA 2502 for the transmission of NDP 2512. In an implementation, frame 2508 may be a clear-to- send (CTS) frame that indicates the channel to be used by STA 2502 for the transmission of NDP 2512.

[0379] In an embodiment, on receiving frame 2508, STA 2502 may perform a PS mode operation for beamformed data transmission with STA 2504. In an example, STA 2502 may perform the PS mode operation for beamformed data transmission while STA 2504 operates in the second power state/mode. [0380] In an embodiment, frame 2510 may announce NDP 2512 to be transmitted by STA 2502, for use by STA 2504 to generate feedback. In an embodiment, frame 2510 may indicate that NDP 2512 is to be transmitted a SIPS after STA 2502 transmits frame 2510 to STA 2504. In an embodiment, frame 2510 may solicit the feedback from STA 2504. In an embodiment, the feedback may comprise a beamforming report or a channel quality indication (CQI) report. In an embodiment, the feedback may comprise feedback based on NDP 2512. In an embodiment, the feedback may comprise single user (SU) feedback, or channel quality indication (CQI) feedback.

[0381] In an embodiment, frame 2510 may solicit the beamforming report or the CQI report from STA 2504. In an example, frame 2510 may indicate a feedback type for use by STA 2504 to generate the beamforming report. In an example, the feedback type may indicate SU feedback or CQI feedback.

[0382] In an embodiment, the SU feedback may comprise a compressed beamforming report. In an example, the compressed beamforming report may comprise average SNR of each spatial stream and compressed beamforming feedback matrices for use by STA 2502 to determine steering matrices for explicit feedback beamforming. In an embodiment, the CQI feedback may comprise a CQI report. In an example, the CQI report may comprise per-RU average SNRs of each spatial stream. In an implementation, each per- RU average SNR may comprise an arithmetic mean of the SNR in decibels over the subcarriers of a 26-tone RU for which feedback is being requested.

[0383] In an embodiment, frame 2510 may further indicate a subcarrier grouping, Ng, for use by STA 2504 to generate the beamforming report. In an example, the subcarrier grouping may be as described in FIG. 19 above.

[0384] In an embodiment, frame 2510 may further indicate a codebook size for use by STA 2504 to generate the beamforming report, when the feedback type indicates the CQI feedback. In an example, the codebook size may be as described in FIG. 19 above.

[0385] In an embodiment, frame 2510 may further indicate a first identifier of STA 2504. In an embodiment, the first identifier of STA 2504 may comprise an association identifier (AID) of STA 2504.

[0386] In an embodiment, frame 2510 may be carried in a PPDU of the first category. In an implementation, frame 2510 may be carried in a PPDU using a non-HT duplicate format with a bandwidth of 40 MHz, 80 MHz, 160 MHz or 320 MHz. In an implementation, frame 2510 may include signaling indicating the PPDU bandwidth.

[0387] In an embodiment, frame 2510 may comprise a control frame In an embodiment, frame 2510 may comprise an announcement frame. In an embodiment, frame 2510 may comprise an null data PPDU announcement (NDPA) frame. For example, the NDPA frame may comprise an UHR NDPA frame.

[0388] After transmitting frame 2510, STA 2502 may initiate transmission of NDP 2512. In an embodiment, STA 2502 may transmit NDP 2512 a SIFS after transmitting frame 2510. In an embodiment, NDP 2512 may be for estimation, by STA 2504, of the channel (used by STA 2502 transmitting NDP 2512) from STA 2502 to STA 2504. As shown in FIG. 25, STA 2502 may transmit NDP 2512 while STA 2504 operates in the second power state/mode. In an embodiment, NDP 2512 may comprise a PPDU of the second category.

[0389] After receiving NDP 2512, STA 2504 may generate the feedback based on NDP 2512. In an embodiment, STA 2504 may generate an estimate of the channel based on NDP 2512 and may generate the feedback based on the estimate. In an example, the feedback may comprise the SU feedback or the CQI feedback based on the feedback type as indicated in frame 2510. STA 2504 may generate a beamforming report or CQI report based on the feedback. In an example, the beamforming report may comprise the compressed beamforming report.

[0390] In an embodiment, STA 2504 may transmit to STA 2502 feedback frame 2514 comprising the feedback. In an embodiment, STA 2504 may transmit to STA 2502 feedback frame 2514 in response to frame 2510. As shown in FIG. 25, STA 2504 may transmit feedback frame 2514 while STA 2504 operates in the second power state/mode.

[0391] In an embodiment, feedback frame 2514 may request whether STA 2504 is to operate in the second power state/mode after STA 2504 transmits feedback frame 2514. In another embodiment, feedback frame 2514 may indicate that STA 2504 will operate in the first power state/mode after STA 2504 transmits feedback frame 2514.

[0392] In an embodiment, feedback frame 2514 may comprise a management frame. In an example, the management frame may comprise an action frame. In an example, the action frame may comprise an action no ack frame. In an example, the action frame may comprise an EHT compressed beamforming/CQI frame as described in FIG. 18.

[0393] In an embodiment, STA 2502 may transmit to STA 2504, while STA 2504 operates in the PS mode, a frame 2516 requesting/indicating that STA 2504 operate, during a first time period, in the first power state/mode of the PS mode. In an embodiment, feedback frame 2514 may indicate the first time period. In an embodiment, the first time period may occur after STA 2504 transmits feedback frame 2514 comprising feedback to STA 2502 (in response to NDP 2512). In an embodiment, the first time period may begin a short interframe space (SIFS) after STA 2502 receives feedback frame 2514. In another embodiment, the first time period may begin a short interframe space (SIFS) after STA 2502 transmits frame 2516. In an embodiment, the first time period may be used by STA 2502 to transmit PPDU 2518, while STA 2504 operates in the first power state/mode. As shown in FIG. 25, for example, the first time period may begin at a time T3 and end at a time T4. In an embodiment, STA 2502 may transmit frame 2516 in response to feedback frame 2514 In an embodiment, frame 2516 may comprise a response frame.

[0394] In an embodiment, frame 2516 may further indicate a second time period. In an embodiment, frame 2510 may further recommend that the STA 2504 operate in the first power state/mode of the PS mode during the second time period. In an embodiment, the second time period may begin after STA 2504 receives frame 2516. For example, the second time period may begin after STA 2502 transmits frame 2516 and end before STA 2502 transmits PPDU 2518. As shown in FIG. 25, for example, the second time period may begin at time T2 and end at time T3.

[0395] Additionally, in an embodiment, frame 2516 may accept or reject operation of STA 2504 in the first power state/mode after STA 2504 transmits feedback frame 2514 as indicated in feedback frame 2514.

[0396] As shown in FIG. 25, STA 2504 may transition/return from the second power state/mode to the first power state/mode at the beginning of the second time period that begins after STA 2504 transmits feedback frame 2514, e.g., time T2. In an embodiment, STA 2504 may operate in the first power state/mode during the second time period. The second time period may end at time T3, before STA 2502 transmits PPDU 2518. In an embodiment, STA 2504 may transition from the first power state/mode to the second power state/mode at the end of the second time period, e.g., time T3.

[0397] As shown in FIG. 25, STA 2502 may initiate transmission of PPDU 2518 to STA 2504 at the beginning of the first time period, e.g., time T3. In an embodiment, STA 2502 may transmit PPDU 2518 to STA 2504 during the first time period and while STA 2504 operates in the second power state/mode. In an embodiment, STA 2502 may transmit PPDU 2518 to STA 2504 during the first time period a SIFS after receiving feedback frame 2514 from STA 2504. In an embodiment, PPDU 2518 may comprise a PPDU of the second category. In an embodiment, PPDU 2518 may carry a data frame. In an embodiment, PPDU 2518 may carry the buffered data for transmission to STA 2504 beamformed based on the feedback comprised in feedback frame 2514. In an embodiment, STA 2504 may transmit a block ack (BA) frame 2520 acknowledging the reception of PPDU 2518 while in the second power state/mode. In another embodiment, STA 2504 may transmit BA frame 2520 after returning to the first power state/mode. After transmitting BA frame 2520, STA 2504 may transition to the other mode of operation or may remain in the first power state/mode of the PS mode.

[0398] In an embodiment (not shown in FIG. 25), feedback frame 2514 may comprise the feedback and indicate STA 2504 operates in the first power state/mode of the PS mode after transmitting feedback frame 2514. In an example, STA 2502 may not transmit frame 2516. after receiving feedback frame 2514. In an example, STA 2502 may not initiate the transmission of PPDU 2518 after receiving feedback frame 2514.

[0399] As shown in FIG. 25, based on STA 2504 being in the second power state/mode during the first time period, STA 2502 does not transmit an IGF before transmitting PPDU 2518 to STA 2504. Similarly, as STA 2504 operates in the second power state/mode during the first time period, STA 2504 does not transmit an ICR frame before receiving PPDU 2518. Communication overhead of the sounding procedure is thereby reduced. Additionally, after transmitting feedback frame 2514, STA 2504 may only need to operate in the second power state/mode during the first time period indicated in frame 2510. Specifically, as shown in FIG. 25, STA 2504 may operate in the first power state/mode during the second time period. Power consumption of STA 2504 may thus be reduced. The benefits of supporting the PS mode may thus be better leveraged by STA 2504 during the sounding procedure. [0400] In an embodiment, frame 2210 described in FIG. 22 and frame 2410 described in FIG. 24 may be control frames.

[0401] FIG. 26 illustrates an example control frame 2600 according to embodiments. Control frame 2600 may be an initial control frame or an announcement frame, for example. For example, control frame 2600 may be an embodiment of frames 2210, and 2410.

[0402] In an embodiment, control frame 2600 may be used by a first STA to indicate or announce an NDP to be transmitted by the first STA, for use by a second STA to generate a beamforming report, and to request/indicate that the second STA operate, during a first time period, in a first power state/mode of the PS mode. The PS mode may comprise a low-power listening mode or a dynamic power save mode. The first power state/mode may comprise a higher capability state/mode, a higher power receive state/mode or an awake state/mode of the PS mode. In an example, the first time period may occur after the second STA transmits a second frame comprising feedback (e.g., the beamforming report). In an embodiment, control frame 2600 may be further used by the first STA to recommend that the second STA operate in a second power state/mode of the PS mode during a second time period. The second power state/mode may comprise a lower capability state/mode, a lower power receive state/mode or a listen state/mode of the PS mode. In an example, the second time period begins after the first STA transmits the NDP and ends before the first time period. For example, the first STA may comprise an embodiment of STA 2022 described in FIG. 22, or STA 2402 described in FIG. 24. For example, the second STA may comprise an embodiment of STA 2204 described in FIG. 22, or STA 2404 described in FIG. 24.

[0403] As shown in FIG. 26, control frame 2600 may include a frame control field, a duration field, a receiver address (RA) field, a transmitter address (TA) field, a sounding dialog token field, a STA info list field, and an FCS field.

[0404] In an embodiment, the sounding dialog token field may include an NDP announcement variant subfield 2602 and a sounding dialog token number subfield. Based on its value, the NDP announcement variant subfield may indicate a variant of control frame 2600. In an example, control frame 2600 may comprise a UHR NDPA frame variant of PS mode operation for beamformed data transmission. In an implementation, the NDP announcement variant subfield 2602 may be set to a value of 4 to identify control frame 2600 as a UHR NDPA frame variant of PS mode operation for beamformed data transmission.

[0405] In an embodiment, the sounding dialog token number subfield may contain a value selected by the transmitter of control frame 2600 to identify control frame 2600.

[0406] As shown in FIG. 26, the STA info list field may include one or more STA info field, including a STA info field 2604. STA info field 2604 may include a STA ID subfield 2606, a partial BW info subfield, a power save mode subfield 2608, an Nc index subfield, a feedback type and Ng subfield, a disambiguation subfield, a codebook size subfield, a first time period subfield 2610, and an optional second time period subfield 2612. [0407] In an embodiment, STA ID subfield 2606 may indicate an identifier of the second STA. In an example, the identifier of the second STA may comprise an AID of the second STA.

[0408] In an embodiment, power save mode subfield 2608 may be used to request that the second STA as indicated in STA ID subfield 2606 operate, during the first time period, in the first power state/mode of the PS mode. In an embodiment, power save mode subfield 2608 may be further used to recommend that the second STA as indicated in STA ID subfield 2606 operate in the second power state/mode of the PS mode during the second time period.

[0409] In an embodiment, first time period subfield 2610 may indicate the first time period during which the second STA as indicated in STA ID subfield 2606 is requested in power save mode subfield 2608 to operate in the first power state/mode of the PS mode.

[0410] In an embodiment, optional second time period subfield 2612 may indicate the second time period during which the second STA as indicated in STA ID subfield 2606 is recommended in power save mode subfield 2608 to operate in the second power state/mode of the PS mode.

[0411] In an embodiment, control frame 2600 may comprise a UHR NDPA frame. In an example, the UHR NDPA frame may comprise a UHR NDPA frame for the PS mode operation for beamformed data transmission. In an example, UHR NDPA frame for the PS mode operation for beamformed data transmission may comprise a UHR PS NDPA frame or UHR enhanced NDPA frame.

[0412] As would be understood by a person of skill in the art based on the teachings herein, the embodiments as described by the above examples may be readily extended to cases including more than two STAs.

[0413] As would be understood by a person of skill in the art based on the teachings herein, the embodiments as described by the above examples may be readily extended to cases including more than two APs.

[0414] As would be understood by a person of skill in the art based on the teachings herein, the embodiments as described by the above examples may be readily extended to scenarios in which any of the APs or any of the STAs may comprise a MLD, comprising at least one affiliated AP or affiliated STA.

[0415] FIG. 27 illustrates an example process 2700 according to an embodiment of the present disclosure. Example process 2700 is provided for the purpose of illustration only and is not limiting of embodiments. Example process 2700 may be performed by a first STA such as STA 2202, STA 2302, STA 2402, or STA 2502, for example.

[0416] As shown in FIG. 27, process 2700 includes, in step 2702, transmitting, by a first STA to a second STA, while the second STA operates in a power save (PS) mode, a first frame requesting/indicating that the second STA operate, during a first time period, in a first power state/mode of the PS mode, where the first time period occurs after the second STA transmits a second frame comprising feedback to the first STA. [0417] In an embodiment, process 2700 further comprises transmitting, by the first STA to the second STA while the second STA operates in the first power state/mode, a null data physical layer protocol data unit (NDP) for use by the second STA to generate the feedback.

[0418] In an embodiment, the feedback comprises a beamforming report or a channel quality indication (CQI) report. In an embodiment, the feedback comprises feedback based on the NDP. In an embodiment, the feedback comprises single user (SU) feedback, multi-user (MU) feedback, or channel quality indication (CQI) feedback.

[0419] In an embodiment, the first frame further indicates the first time period. In an embodiment, the first time period begins a short interframe space (SIPS) after the first STA receives the second frame.

[0420] In an embodiment, the first frame further indicates a second time period. In an embodiment, the first frame further recommends that the second STA operate in a second power state/mode of the PS mode during the second time period In an embodiment, the second time period begins after the first STA transmits the NDP and ends before the first time period. In an embodiment, the second time period begins after the second STA transmits the second frame. In an embodiment, the second time period ends before the second STA transmits the second frame. In an embodiment, the second time period comprising a first portion beginning after the first STA transmits the NDP and ending before the second STA transmits the second frame and a second portion beginning after the second STA transmits the second frame and ending before the first time period.

[0421] In an embodiment, the first frame further announces the NDP to be transmitted by the first STA. In an embodiment, the first frame comprises an announcement frame.

[0422] In an embodiment, process 2700 further comprises receiving, by the first STA from the second STA, the second frame in response to the first frame.

[0423] In an embodiment, process 2700 further comprises transmitting, by the first STA to the second STA and during the first time period, a physical layer protocol data unit (PPDU).

[0424] In an embodiment, the first STA does not transmit an initial control frame (ICF) before transmitting the PPDU, based on the second STA being in the first power state/mode during the first time period.

[0425] In an embodiment, the PS mode comprises a low-power listening mode or a dynamic power save mode. In an embodiment, the first power state/mode comprises a higher capability state/mode, a higher power receive state/mode or an awake state/mode of the PS mode. In an embodiment, the second power state/mode comprises a lower capability state/mode, a lower power receive state/mode or a listen state/mode of the PS mode.

[0426] In an embodiment, the first frame comprises a null data physical layer protocol data unit (NDP). In an embodiment, process 2700 further comprises transmitting, by the first STA to the second STA, a third frame announcing the first frame. In an embodiment, transmitting the first frame comprises transmitting the first frame in response to the second frame. In an embodiment, the first frame comprises a response frame. In an embodiment, the first time period begins a short interframe space (SI FS) after the first STA transmits the first frame. In an embodiment, the second frame requests whether the second STA is to operate in the first power state/mode after the second STA transmits the second frame. In another embodiment, the second frame indicates that the second STA will operate in a second power state/mode after the second STA transmits the second frame. In an embodiment, the first frame accepts or rejects operation of the second STA in the second power state/mode during the first time period.

[0427] FIG. 28 illustrates an example process 2800 according to an embodiment of the present disclosure. Example process 2800 is provided for the purpose of illustration only and is not limiting of embodiments. Example process 2800 may be performed by a first STA such as STA 2204, STA 2304, or STA 2404, for example. Process 2800 may be performed while the first STA is in a PS mode as illustrated in FIGs. 22-25, for example. The PS mode may comprise a low-power listening mode or a dynamic power save mode. The PS mode may comprise a first power state/mode and a second power state/mode as described above. The first power state/mode may comprise a higher capability state/mode, a higher power receive state/mode or an awake state/mode of the PS mode. The second power state/mode may comprise a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode of the PS mode.

[0428] As shown in FIG. 28, process 2800 includes in step 2802, receiving, by the first STA from a second STA, while the first STA operates in the PS mode, a first frame requesting/indicating that the first STA operate, during a first time period, in a first power state/mode of the PS mode. In an embodiment, the first time period occurs after the first STA transmits a second frame comprising feedback to the second STA.

[0429] In an embodiment, process 2800 further comprises receiving, by the first STA while the first STA operates in the first power state/mode from the second STA, a null data physical layer protocol data unit (NDP) for use by the first STA to generate the feedback.

[0430] In an embodiment, the feedback comprises a beamforming report or a channel quality indication (CQI) report. In an embodiment, the feedback comprises feedback based on the NDP. In an embodiment, the feedback comprises single user (SU) feedback, multi-user (MU) feedback, or channel quality indication (CQI) feedback.

[0431] In an embodiment, the first frame further indicates the first time period. In an embodiment, the first time period begins a short interframe space (SIFS) after the first STA receives the second frame.

[0432] In an embodiment, the first frame further indicates a second time period. In an embodiment, the first frame further recommends that the first STA operate in a second power state/mode of the PS mode during the second time period. In an embodiment, the second time period begins after the second STA transmits the NDP and ends before the first time period. In an embodiment, the second time period begins after the first STA transmits the second frame. In an embodiment, the second time period ends before the first STA transmits the second frame. In an embodiment, the second time period comprising a first portion beginning after the second STA transmits the NDP and ending before the first STA transmits the second frame and a second portion beginning after the first STA transmits the second frame and ending before the first time period.

[0433] In an embodiment, process 2700 further comprises further comprising: transitioning, by the first STA to the second power state/mode at the beginning of the second time period; and transitioning, by the first STA from the second power state/mode to the first power state/mode at the end of the second time period. [0434] In an embodiment, the first frame further announces the NDP to be transmitted by the second STA. In an embodiment, the first frame comprises an announcement frame.

[0435] In an embodiment, process 2700 further comprises transmitting, by the first STA to the second STA, the second frame in response to the first frame.

[0436] In an embodiment, transmitting the second frame comprises transmitting the second frame while the first STA operates in the first power state/mode.

[0437] In an embodiment, process 2700 further comprises receiving, by the first STA while the first STA operates in the first power state/mode from the second STA and during the first time period, a physical layer protocol data unit (PPDU).

[0438] In an embodiment, the first STA operates in the first power state/mode and does not transmit an initial response frame before receiving the PPDU, based on the first STA being in the first power state/mode during the first time period.

[0439] In an embodiment, the first frame comprises a null data physical layer protocol data unit (NDP). In an embodiment, process 2700 further comprises receiving, by the first STA from the second STA, a third frame announcing the first frame.

[0440] In an embodiment, receiving the first frame comprises receiving the first frame in response to the second frame. In an embodiment, the first frame comprises a response frame. In an embodiment, the first time period begins a short interframe space (SIFS) after the first STA receives the first frame. In an embodiment, the second frame requests whether the first STA is to operate in the first power state/mode after the first STA transmits the second frame. In an embodiment, the second frame indicates that the first STA will operate in a second power state/mode after the first STA transmits the second frame. In an embodiment, the first frame accepts or rejects operation of the first STA in the second power state/mode during the first time period.

[0441] FIG. 29 illustrates an example process 2900 according to an embodiment of the present disclosure. Example process 2900 is provided for the purpose of illustration only and is not limiting of embodiments. Example process 2900 may be performed by a first STA such as STA 2204, STA 2304, or STA 2404, for example. Process 2900 may be performed while the first STA is in a PS mode as illustrated in FIGs. 22-25, for example. The PS mode may comprise a low-power listening mode or a dynamic power save mode. The power save mode may comprise a first power state/mode and a second power state/mode as described above. The first power state/mode may comprise a higher capability state/mode, a higher power receive state/mode or an awake state/mode of the PS mode. The second power state/mode may comprise a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode of the power save mode. As shown in FIG. 29, process 2900 may include steps 2902, 2904, and 2906.

[0442] Step 2902 includes receiving, by a first station (STA) from a second STA, an announcement frame indicating a null data physical layer protocol data unit (NDP) to be transmitted.

[0443] Step 2904 includes receiving, by the first STA from the second STA, while the first STA operates in a first power state/mode of a power save (PS) mode, the NDP for use by the first STA to generate feedback. [0444] Step 2096 includes transmitting, by the first STA to the second STA, a first frame comprising the feedback and indicating the first STA operates in the second power state/mode of the PS mode after transmitting the first frame.

Claims

CLAIMS What is claimed is:

1. A method comprising: transmitting, by a first access point (AP) to a first station (STA), while the first STA operates in a power save (PS) mode, a first frame requesting that the first STA operate, during a first time period, in a first power mode of the PS mode, wherein the first time period comprises a sounding sequence by the first AP and a second AP; transmitting, by the first AP to the first STA and during the first time period, a null data physical layer protocol data unit (NDP) for use by the first STA to generate feedback for the first AP; receiving, by the first AP from the first STA and during the first time period, a second frame comprising the feedback; and after receiving the feedback, transmitting, by the first AP to the first STA and using the feedback, a physical protocol data unit (PPDU).

2. A method comprising: transmitting, by a first station (STA) to a second STA, while the second STA operates in a power save (PS) mode, a first frame: announcing a null data physical layer protocol data unit (NDP) to be transmitted by the first

STA, for use by the second STA to generate a beamforming report (BFR); and requesting that the second STA operate, during a first time period, in a first power mode of the PS mode, wherein the first time period occurs after the second STA transmits a second frame comprising the beamforming report to the first STA; transmitting, by the first STA to the second STA, the NDP; receiving, by the first STA from the second STA, the second frame in response to the first frame; and transmitting, by the first STA and during the first time period, a physical protocol data unit (PPDU) to the second STA.

3. A method comprising: transmitting, by a first station (STA) to a second STA, while the second STA operates in a power save (PS) mode, a first frame requesting that the second STA operate, during a first time period, in a first power mode of the PS mode, wherein the first time period occurs after the second STA transmits a second frame comprising feedback to the first STA.

4. The method of claim 3, wherein the first frame comprises a null data physical layer protocol data unit (NDP).

5. The method of any of claims 3-4, further comprising transmitting, by the first STA to the second STA, a third frame announcing the first frame.

6. The method of claim 3, wherein transmitting the first frame comprises transmitting the first frame in response to the second frame.

7. The method of any of claims 3 or 6, wherein the first frame comprises a response frame.

8. The method of any of claims 3, 6, or 7, wherein the first time period begins a short interframe space (SIFS) after the first STA transmits the first frame.

9. The method of any of claims 3 or 6-8, wherein the second frame requests whether the second STA is to operate in the first power mode after the second STA transmits the second frame.

10. The method of any of claims 3, or 6-8, wherein the second frame indicates that the second STA will operate in a second power mode after the second STA transmits the second frame.

11 . The method of claim 10, wherein the first frame accepts or rejects operation of the second STA in the second power mode during the first time period.

12. A method comprising: receiving, by a first station (STA) from a first access point (AP), while the first STA operates in a power save (PS) mode, a first frame requesting that the first STA operate, during a first time period, in a first power mode of the PS mode, wherein the first time period comprises a sounding sequence by the first AP and a second AP; transitioning, by the first STA, from a second power mode of the PS mode to the first power mode; receiving, by the first STA from the first AP and during the first time period, a null data physical layer protocol data unit (NDP) for use by the first STA to generate feedback for the first AP; transmitting, by the first STA to the first AP, a second frame comprising the feedback for the first AP; and receiving, by the first STA from the first AP and using the feedback, a physical protocol data unit (PPDU).

13. A method comprising: receiving, by a first station (STA) to a second STA, while the first STA operates in a power save (PS) mode, a first frame: announcing a null data physical layer protocol data unit (NDP) to be transmitted by the second

STA, for use by the first STA to generate a beamforming report; and requesting that the first STA operate, during a first time period, in a first power mode of the PS mode, wherein the first time period occurs after the first STA transmits a second frame comprising the beamforming report to the second STA; receiving, by the first STA from the second STA, the NDP, while the first STA operates in the first power mode; transmitting, by the first STA to the second STA, the second frame in response to the first frame, while the first STA operates in the first power mode; and receiving, by the first STA and during the first time period, a physical protocol data unit (PPDU) from the second STA.

14. A method comprising: receiving, by a first station (STA) from a second STA, while the first STA operates in a power save (PS) mode, a first frame requesting that the first STA operate, during a first time period, in a first power mode of the PS mode, wherein the first time period occurs after the first STA transmits a second frame comprising feedback to the second STA.

15. The method of claim 14, further comprising receiving, by the first STA from the second STA, and while the first STA operates in the first power mode, a null data physical layer protocol data unit (NDP) for use by the first STA to generate the feedback.

16. The method of claim 15, wherein the feedback comprises a beamforming report or a channel quality indication (CQI) report, and wherein the feedback comprises feedback based on the NDP.

17. The method of any of claims 14-16, wherein the first frame further indicates the first time period.

18. The method of any of claims 14-17, wherein the first time period begins a short interframe space (SIPS) after the first STA transmits the second frame.

19. The method of any of claims 15-18, wherein the first frame further indicates a second time period.

20. The method of claim 19, wherein the first frame further recommends that the first STA operate in a second power mode of the PS mode during the second time period.

21 . The method of any of claims 19-20, wherein the second time period begins after the second STA transmits the NDP and ends before the first time period.

22. The method of claim 21 , wherein the second time period begins after the first STA transmits the second frame.

23. The method of claim 21 , wherein the second time period ends before the first STA transmits the second frame.

24. The method of any of claims 19-20, wherein the second time period comprises a first portion beginning after the second STA transmits the NDP and ending before the first STA transmits the second frame and a second portion beginning after the first STA transmits the second frame and ending before the first time period.

25. The method of any of claims 20-24, further comprising: transitioning, by the first STA to the second power mode at the beginning of the second time period; and transitioning, by the first STA from the second power mode to the first power mode at the end of the second time period.

26. The method of any of claims 15-25, wherein the first frame further announces the NDP to be transmitted by the second STA.

27. The method of claim 26, wherein the first frame comprises an announcement frame.

28. The method of any of claims 14-27, further comprising transmitting, by the first STA to the second STA, the second frame in response to the first frame.

29. The method of claim 28, wherein transmitting the second frame comprises transmitting the second frame while the first STA operates in the first power mode.

30. The method of any of claims 14-29, further comprising receiving, by the first STA while the first STA operates in the first power mode from the second STA and during the first time period, a physical layer protocol data unit (PPDU).

31 . The method of claim 30, wherein the first STA operates in the first power mode and does not transmit an initial response frame before receiving the PPDU, based on the first STA being in the first power mode during the first time period.

32. A method comprising: receiving, by a first station (STA) from a second STA, an announcement frame indicating a null data physical layer protocol data unit (NDP) to be transmitted; receiving, by the first STA from the second STA, while the first STA operates in a first power mode of a power save (PS) mode, the NDP for use by the first STA to generate feedback; and transmitting, by the first STA to the second STA, a first frame comprising the feedback and indicating the first STA operates in a second power mode of the PS mode after transmitting the first frame.

33. A device comprising: one or more processors; and memory storing instructions that, when executed by the one or more processors, cause the device to perform a method according to any of claims 1-32.

34. A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors, cause the one or more processors to perform a method according to any of claims 1-32.