WO2025199296A1 - Inter-access point notification - Google Patents

Abstract

A first access point (AP) transmits to a second AP a request for the second AP to monitor physical layer protocol data units (PPDUs) addressed to the first AP. The first AP transitions to a first mode of a power save mode. The first mode may be a lower capability mode of the power save mode. The first AP receives from the second AP a notification of reception by the second AP of a first PPDU addressed to the first AP, and based on the notification, transitions from the first mode to a second mode of the power save mode. The second mode may be a higher capability mode of the power save mode. The first AP receives the second PPDU addressed to the first AP while in the second mode of the power save mode.

Description

TITLE

INTER-ACCESS POINT NOTIFICATION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63/568,474, filed March 22, 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 an example multi-AP network.

[0011] FIG. 9 illustrates an example network that includes a coordinated AP set.

[0012] FIG. 10 illustrates an example multi-AP operation procedure.

[0013] FIG. 11 illustrates an example multi-AP sounding phase.

[0014] FIG. 12 illustrates an example multi-AP downlink data transmission phase.

[0015] FIG. 13 illustrates an example multi-AP uplink data transmission phase.

[0016] FIG. 14 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.

[0017] FIG. 15 illustrates a High Efficiency (HE) Single User (SU) PPDU, an HE Multi-User (MU) PPDU, and an HE Extended Range (ER) SU PPDU.

[0018] FIG. 16 illustrates an Extremely High Throughput (EHT) Multi-user (MU) PPDU.

[0019] FIG. 17 illustrates an example multi-user request-to-send (MU-RTS) trigger frame.

[0020] FIG. 18 illustrates an example block acknowledgment request (BlockAckReq or BAR) frame.

[0021] FIG. 19 illustrates an example of a power save (PS) mode.

[0022] FIG. 20 illustrates an example of an AP implementation of the PS mode illustrated in FIG. 19.

[0023] FIG.21 illustrates an example that highlights a problem that may arise in association with the PS mode illustrated in FIG. 20.

[0024] FIG. 22 is an example that illustrates an inter AP notification procedure according to an embodiment.

[0025] FIG. 23 is an example that illustrates an inter AP notification procedure according to an embodiment. [0026] FIG. 24 is an example that illustrates an inter AP notification procedure according to an embodiment.

[0027] FIG. 25 is an example that illustrates an inter AP notification procedure according to an embodiment.

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

[0029] FIG. 27 illustrates an example user info field of a trigger frame which may be used according to embodiment.

[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.

[0032] FIG. 30 illustrates an example process according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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 {STA 1 , 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 “employ i n g/u sing” (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.

[0037] 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. [0038] In this disclosure, parameters (or equally called, fields, or Information elements: lEs) 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.

[0039] 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. [0040] 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 (OPLDs). 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 afunctional module.

[0041] FIG. 1 illustrates example wireless communication networks in which embodiments of the present disclosure may be implemented.

[0042] 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) 110 and 120 and a distribution system (DS) 130.

[0043] 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 110-2 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..

[0044] 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).

[0045] 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. [0046] The example wireless communication networks illustrated in FIG. 1 may further include one or more ad-hoc networks or independent BSSs (I BSSs). An ad-hoc network or I BSS 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). [0047] 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.

[0048] 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.

[0049] 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 PLOP 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 802.11 protocol to be used to transmit the payload.

[0050] A frequency band may include one or more sub-bands or frequency channels. For example, PPDUs conforming to the IEEE 802.11 n, 802.11 ac, 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] As shown in FIG. 3, MAC frame 300 includes a MAC header, a variable length frame body, and a frame check sequence (FCS).

[0057] 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).

[0058] 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).

[0059] The protocol version subfield is invariant in size and placement across all revisions of the IEEE 802.11 standard. The value of the protocol version subfield is 0 for MAC frames.

[0060] 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. [0061] 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.

[0062] 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.

[0063] 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.

[0064] The power management subfield is used to indicate the power management mode of a STA.

[0065] 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.

[0066] The protected frame subfield is set to 1 if the frame body field contains information that has been processed by a cryptographic encapsulation algorithm.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] The QoS control field identifies the traffic category (TO) 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] One or more vendor specific elements are optionally present. These elements are absent when the category subfield of the Action field is vendor-specific.

[0079] 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.

[0080] 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. [0081] 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.

[0082] FIG. 5 illustrates an example format of a trigger frame 500. T rigger 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. T rigger frame 500 may also carry other information required by a responding STA to transmit a TB PPDU to the AP.

[0083] 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.

[0084] 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.

[0085] 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).

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 T rigger frame.

[0090] 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 FEO 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 20996-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.

[0091] The Padding field is optionally present in trigger 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.

[0092] 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.

[0093] 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.

[0094] 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).

[0095] 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 (EDOA) access policy to identify user priority for either TO orTS).

[0096] 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.)

[0097] 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.

[0098] 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 64768 octets.

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

[0099] In a frame sent by an HE STA to an HE AP, the following rules may apply to the queue size value.

[0100] 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.

[0101] 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.

[0102] 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;

17408 +2048 x UV, if SF is equal to 2;

148480 + 32768 x UV, if SF is equal to 3 and UV is less than 62;

> 2 147328, 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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 bitof 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.

[0107] The delta Tl D subfield, together with the values of the ACI bitmap subfield, indicate the number of Tl Ds for which the STA is reporting the buffer status.

[0108] 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.

[0109] The scaling factor subfield indicates the unit SF, in octets, of the queue size high and queue size all subfields. [0110] 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.

[0111] 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. [0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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).

[0121] 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. [0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[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 STA) 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 an example multi-AP network 800. Example multi-AP network 800 may be a multi-AP network in accordance with the Wi-Fi Alliance standard specification for multi-AP networks. As shown in FIG. 8, multi-AP network 800 may include a multi-AP controller 802 and a plurality of multi-AP groups (or multi-AP sets) 804, 806, and 808. [0133] Multi-AP controller 802 may be a logical entity that implements logic for controlling the APs in multi-AP network 800. Multi-AP controller 802 may receive capability information and measurements from the APs and may trigger AP control commands and operations on the APs. Multi-AP controller 802 may also provide onboarding functionality to onboard and provision APs onto multi-AP network 800.

[0134] Multi-AP groups 804, 806, and 808 may each include a plurality of APs. APs in a multi-AP group are in communication range of each other and may coordinate their transmissions and/or transmissions from their associated STAs. Coordinated transmissions may involve all or a subset of the APs in a multi-AP group. A multi-AP group may also be referred to as an AP candidate set as APs in a multi-AP group are considered candidates for a coordinated transmission initiated by an AP. The APs in a multi-AP group are not required to have the same primary channel. As used herein, the primary channel for an AP refers to a default channel that the AP monitors for management frames and/or uses to transmit beacon frames. For a STA associated with an AP, the primary channel refers to the primary channel of the AP, which is advertised through the AP’s beacon frames.

[0135] In one approach, a multi-AP group may be established by a coordinator AP in a multi-AP setup phase prior to any multi-AP coordination. APs of the multi-AP group, other than the coordinator AP, may be referred to as the coordinated APs. A coordinator AP may establish one or more multi-AP groups. A coordinated AP may likewise be a member of multiple multi-AP groups. A coordinator AP of a multi-AP group may be a coordinated AP of another multi-AP group, and vice versa. In another approach, a multi-AP group may be established by a network administrator manually by configuring APs as part of the multi-AP group. In yet another approach, a multi-AP group may be established in a distributed manner by APs without a central controller. In this case, an AP may advertise its multi-AP capability in a beacon or other management frame (e.g., public action frame). Other APs that receive the frame with the multi-AP capability information may perform a multi-AP setup with the AP that advertised the multi-AP capability.

[0136] In one approach, one of the APs in a multi-AP group may be designated as a master AP. The designation of the master AP may be done by AP controller 802 or by the APs of the multi-AP group. The master AP of a multi-AP group may be fixed or may change over time between the APs of the multi-AP group. An AP that is not the master AP of the multi-AP group is known as a slave AP.

[0137] In one approach, APs in a multi-AP group may perform coordinated transmissions together. One aspect of coordination may include coordination to perform coordinated transmissions within the multi-AP group. As used herein, a coordinated transmission, also referred to as a multi-AP transmission, is a transmission event in which multiple APs (of a multi-AP group or a multi-AP network) transmit in a coordinated manner over a time period. Coordinated transmissions may involve simultaneous transmissions of a plurality of APs in a multi-AP group. The time period of simultaneous AP transmission may be a continuous period. The multi-AP transmission may use different transmission techniques, such as Coordinated OFDMA (COFDMA), Coordinated Spatial Reuse (CSR), Joint Transmission or Reception (JT/JR), Coordinated Beamforming (CBF), and CTDMA, or a combination of two or more of the aforementioned techniques.

[0138] Multi-AP transmissions may be enabled by the AP controller and/or by the master AP of the multi-AP group. In one approach, the AP controller and/or the master AP may control time and/or frequency sharing in a transmission opportunity (TXOP). For example, when one of the APs (e.g., the master AP) in the multi-AP group obtains a TXOP, the AP controller and/or the master AP may control how time/frequency resources of the TXOP are to be shared with other APs of the multi-AP group. In an implementation, the AP of the multi-AP group that obtains a TXOP becomes the master AP of the multi-AP group. The master AP may then share a portion of its obtained TXOP (which may be the entire TXOP) with one or more other APs of the multi-AP group.

[0139] Different multi-AP transmission schemes may be suitable for different use cases in terms of privacy protection, including whether transmitted data may be shared with other BSSs in the multi-AP group. For example, some multi-AP transmission schemes, such as GSR, CDTMA, coordinated frequency division multiple access (CFDMA), COFDMA, and CBF, enable a master AP to coordinate slave APs by sharing control information among APs, without requiring the sharing of user data among APs. The control information may include BSS information of APs, link quality information of channels between each AP and its associated STAs, and information related to resources to be used to achieve multiplexing in power, time, frequency, or special domains for multi-AP transmission. The control information exchanged among a master AP and slave APs may be used for interference avoidance or nulling to avoid or null co-channel interference introduced to neighboring BSSs in a multi-AP network. Interference avoidance or interference nulling requires that data transmissions between an AP and STAs are only within the same BSS. In other words, each AP transmits or receives data frames to or from its associated STAs, while each STA receives or transmits data frames to or from its associating AP.

[0140] By contrast, other multi-AP transmission schemes may enable a master AP to coordinate slave APs by sharing both control information and user data among APs in a multi-AP group. Control information may include BSS information related to APs and link quality information of channels between each AP and its associated STAs. By having user data exchanged over backhaul, the master AP and slave APs may perform data transmissions jointly to achieve spatial diversity, e.g., using distributed MIMO, for example, joint transmission (JT) for downlink transmissions and joint reception (JR) for uplink transmissions. The data transmissions between APs and STAs may include transmissions within the same BSS and/or across different BSSs. In other words, an AP may transmit or receive data frames to or from its associated STAs as well STAs associated with other APs participating in multi-AP transmission. Similarly, a STA may transmit or receive data frames to or from multiple APs.

[0141] Different multi-AP transmission schemes may be suitable for different use cases in terms of signal reception levels at STAs or APs within a multi-AP group. For example, CBF and JT/JR require that each STA involved in a multi- AP transmission be located within a common area of signal coverage of the APs involved in the multi-AP transmission. Generally, CBF may be suitable when a receiving STA suffers from potential interference from other APs in the multi-AP group. By using channel related information such as channel state information (CSI), channel quality indication (CQI), or compressed beamforming (BF) feedback exchanged among APs, an AP may pre-code a signal to be transmitted to form a beam that increases power toward a target STA while reducing the power that interferes with a STA associated with a neighboring AP. Use cases of JT/JR may require a sufficient received signal power at receiving STAs for JT and a sufficient received signal power at receiving APs for JR. By contrast, CSR may perform multi-AP transmission in an interference coordination manner. The received signal power at a STA associated with an AP transmitting data may be required to be much higher than the received interference power.

[0142] Different multi-AP transmission schemes may require different synchronization levels and may operate with or without a backhaul between a master AP and slave APs in a multi-AP group. For example, GSR may require PPDU-level synchronization, whereas OBF may require symbol-level synchronization. On the other hand, JT/JR may require tight time/frequency/phase-level synchronization as well as a backhaul for data sharing between APs in the multi-AP group.

[0143] Different multi-AP transmission schemes may have different complexity levels with regard to coordination between a master AP and slave APs in a multi-AP group. For example, JT/JR may require very high complexity due to both CSI and user data being shared between APs. OBF may require medium complexity due to the sharing of CSI. CFDMA, COFDMA and CTDMA may require medium or relatively low complexity due to the CSI and time/frequency resources to be shared between APs. GSR may require low complexity as the amount of information related to spatial reuse and traffic that needs to be exchanged between APs may be low.

[0144] A multi-AP group may adopt a static multi-AP operation including a static multi-AP transmission scheme. A multi-AP network may also be dynamic due to various reasons. For example, a STA may join or leave the multi-AP network, a STA may switch to a power save mode, or an AP or a STA may change its location. Such changes may lead to changes in the conditions underlying the selection of the multi-AP transmission scheme and may cause certain requirements (e.g., synchronization, backhaul, coordination, etc.) for the multi-AP transmission scheme to be lost. This results in an inferior quality of transmissions in the multi-AP network.

[0145] FIG. 9 illustrates an example network 900 that includes a coordinated AP set. As shown in FIG. 9, the coordinated AP set may include AP 902-1 and AP 902-2. The coordinated AP set may be a subset of an established multi-AP group. At least one STA may be associated with each of APs 902-1 and 902-2. For example, a STA 904-1 may be associated with AP 902-1, and a STA 904-2 may be associated with AP 902-2.

[0146] APs 902-1 and 902-2 may belong to the same ESS as described above in FIG. 1. In such a case, APs 902-1 and 902-2 may be connected by a DS to support ESS features. In addition, as part of a coordinated AP set, APs 902-1 and 902-2 may be connected by a backhaul. The backhaul is used to share information quickly between APs to support coordinated transmissions. The shared information may be channel state information or data to be sent to associated STAs. The backhaul may be a wired backhaul or a wireless backhaul. A wired backhaul is preferred for high-capacity information transfer without burdening the main radios of the APs. However, a wired backhaul may require a higher deployment cost and may place greater constraints on AP placement. A wireless backhaul is preferred for its lower deployment cost and flexibility regarding AP placement. However, because a wireless backhaul relies on the main radios of the APs to transfer information, the APs cannot transmit or receive any data while the wireless backhaul is being used. [0147] Typically, one of APs 902-1 and 902-2 may act as a Master AP and the other as a Slave AP. The Master AP is the AP that is the owner of the TXOP. The Master AP shares frequency resources during the TXOP with the Slave AP. When there are more than two APs in the coordinated set, a Master AP may share its TXOP with only a subset of the coordinated AP set. The role of the Master AP may change over time. For example, the Master AP role may be assigned to a specific AP for a duration of time. Similarly, the Slave AP role may be chosen by the Master AP dynamically or can be pre-assigned for a duration of time.

[0148] Depending on the capability of APs in a coordinated AP set, the APs may only do certain type of coordinated transmissions. For example, in FIG. 9, if AP 902-1 supports JT and GSR while AP 902-2 supports GSR and OBF, both APs may only perform GSR as a coordinated transmission scheme. An AP may also prefer to perform single AP transmissions for a duration of time if the benefit of coordinated transmission does not outweigh some disadvantages with coordinated transmission such as reduced flexibility and increased computational power required.

[0149] GSR is one type of multi-AP coordination that may be supported by AP 901-1 and AP 902-2 as shown in FIG. 9. Spatial reuse using GSR can be more stable than non-AP coordinated spatial reuse schemes such as overlapping basic service set (OBSS) packet detect (PD)-based SR and PSR-based SR. For example, in an example network 900, APs 902-1 and 902-2 may perform a joint sounding operation in order to measure path loss (PL) on paths of network 900. For example, the joint sounding operation may result in the measurement of PL 908 for the path between APs 902- 1 and 902-2, path loss 910 for the path between AP 902-1 and STA 904-2, and path loss 912 for the path between AP 902-2 and STA 904-1. The measured path loss information may then be shared between APs 902-1 and 902-2 (e.g., using the backhaul) to allow for simultaneous transmissions by APs 902-1 and 902-2 to their associated STAs 904-1 and 904-2 respectively. Specifically, one of APs 902-1 and 902-2 obtains a TXOP to become the Master AP. The Master AP may then send a GSR announcement frame to the other AP(s). In an example, the Master AP may perform a polling operation, before sending the GSR announcement frame, to poll Slave APs regarding packet availability for transmission. If at least one Slave AP responds indicating packet availability, the Master AP may proceed with sending the GSR announcement frame. In the GSR announcement, the Master AP may limit the transmit power of a Slave AP in order to protect its own transmission to its target STA. The Slave AP may similarly protect its own transmission to its target STA by choosing a modulation scheme that enables a high enough Signal to Interference Ratio (SIR) margin to support the interference due to the transmission of the Master AP to its target STA.

[0150] FIG. 10 illustrates an example 1000 of a multi-AP operation procedure. In example 1000, the multi-AP operation procedure is illustrated with respect to a multi-AP network that includes APs 1002 and 1004 and STAs 1006 and 1008. In an example, APs 1002 and 1004 may form a multi-AP group. AP 1002 may be the master AP and AP 1004 may be a slave AP of the multi-AP group. For example, AP 1002 may obtain a TXOP making it the master AP of the multi-AP group. Alternatively, AP 1002 may be designated as the master AP by a multi-AP controller.

[0151] As shown in FIG. 10, the multi-AP operation procedure may include a series of phases in time, each of which may contain a plurality of frame exchanges within the multi-AP network. Specifically, the multi-AP operation procedure may include a multi-AP selection phase 1010, a multi-AP data sharing phase 1012, a multi-AP sounding phase 1014, and a multi-AP data transmission phase 1016.

[0152] A multi-AP network may carry out a multi-AP operation based on a specific multi-AP transmission scheme. The multi-AP transmission scheme may be chosen by the master AP based on the capabilities of the slave APs in a multi-AP group. Prior to a multi-AP operation, a slave AP may inform the master AP of capability information related to the slave AP, including the capabilities of supporting one or more multi-AP transmission schemes. The slave AP may also inform the master AP of BSS information of the BSS of the slave AP and of link quality information for STAs associated with the slave AP. The master AP may receive information related to all available slave APs. The information related to slave APs may include capability information, BSS information, and link quality information. Based on the information provided by available slave APs, the master AP may determine during a multi-AP selection phase the slave APs to be designated for a multi-AP transmission and a specific multi-AP transmission scheme to be used during the multi-AP transmission.

[0153] Multi-AP selection phase 1010 may include procedures for soliciting, selecting, or designating slave AP(s) for a multi-AP group by a master AP. As seen in FIG. 10, the multi-AP selection phase may include transmissions of frame 1018 from AP 1002 and frame 1020 from AP 1004. AP 1002 may transmit frame 1018 to solicit information regarding the buffer status of AP 1004. In response, AP 1004 may transmit frame 1020 to inform AP 1002 of its and its associated STAs buffer status and/or whether it intends to join multi-AP operation. Multi-AP selection phase 1010 may also be used to exchange information related to multi-AP operation, including BSS information of APs and link quality information between each AP and its associated STAs, for example. The BSS information of an AP may include a BSS ID of the BSS of the AP, identifiers and/or capabilities of STAs belonging to the BSS, information regarding sounding capabilities of the STAs, information regarding Ml MO capabilities of the AP, etc. Link quality information may include received signal strength indicator (RSSI), signal-to-noise ratio (SNR), signal-to-interference-plus-noise-ratio (SINR), channel state information (CSI), channel quality indicator (CQI).

[0154] Multi-AP data sharing phase 1012 may include procedures for sharing data frames to be transmitted by APs to associated STAs among the master AP and selected slave AP(s) via direct connections between APs. Phase 1012 may be optional for some multi-AP data transmission schemes. For example, phase 1012 may be required for JT/JR as data frames may be exchanged between APs before or after multi-AP data transmission phase 1016.

[0155] Multi-AP data sharing phase 1012 may be performed using a wired backhaul, an in-channel wireless backhaul, or an off-channel wireless backhaul. In some cases, multi-AP data sharing phase 1012 may be performed over an in- channel backhaul, e.g., using the same wireless channel used to transmit/receive data to/from STAs. For example, as shown in FIG. 10, in phase 1012, AP 1002 may transmit a frame 1022, which may be received by AP 1004. Frame 1022 may include MPDUs that AP 1002 wishes to transmit to associated STAs using a multi-AP operation. Similarly, AP 1004 may transmit a frame 1024, which may be received by AP 1002. Frame 1024 may include MPDUs that AP 1004 wishes to transmit to associated STAs using a multi-AP operation.

[0156] Multi-AP sounding phase 1014 may include procedures for multi-AP channel sounding, including channel estimation and feedback of channel estimates among the master AP, candidate slave AP(s), and associated STAs. Phase 1014 may be optional for some multi-AP transmission schemes, such as COFDMA, CDTMA, and GSR. For example, phase 1014 may be performed by the master AP to aid in resource unit allocation when orchestrating a COFDMA transmission.

[0157] Multi-AP data transmission phase 1016 may include exchange of data frames between the master AP, slave AP(s), and their associated STAs based on multi-AP transmission scheme(s) determined by the master AP. Depending on the multi-AP transmission scheme(s) to be used, phase 1016 may include optional synchronization between APs of the multi-AP group, before exchange of data frames between APs and STAs within the multi-AP group.

[0158] The order of phases 1010, 1012, 1014 and 1016 may be different than shown in FIG. 10. For example, in COFDMA, phase 1016 may occur immediately after phase 1010, whereas, in JT/JR, phase 1012 may occur after phase 1010. Further, as mentioned above, some phases may be optional and may or may not be present. For example, phase 1014 may not be required for COFDMA but may be required for JT/JR.

[0159] FIG. 11 illustrates an example 1100 of a multi-AP sounding phase. Multi-AP sounding phase 1100 may be an example of multi-AP sounding phase 1014. As shown in FIG. 11, example 1100 may include a master AP 1102 and a slave AP 1104 of a multi-AP group. Example 1100 may further include a STA 1106 associated with AP 1102 and a STA 1108 associated with AP 1104.

[0160] As shown in FIG. 11 , multi-AP sounding phase 1100 may include frame exchanges to allow AP 1102 (the master AP) to acquire channel state information (CSI) of channels in the multi-AP group. In an implementation, phase 1100 may include a first subphase 1110 and a second subphase 1112.

[0161] During the first subphase 1110, APs may initiate channel sounding and STAs may estimate CSI. For example, AP 1102 may transmit a frame 1114 to AP 1104 (the slave AP) to trigger multi-AP sounding. Frame 1114 may comprise a multi-AP trigger frame. Subsequently, APs 1102 and 1104 may transmit respectively announcement frames 1116-1 and 1116-2 to their respective associated STAs 1106 and 1108 to announce the transmission of sounding frames. Frames 1116-1 and 1116-2 may comprise multi-AP null data PPDU announcement (NDPA) frames. Frames 1116-1 and 1116-2 may be transmitted simultaneously. Next, APs 1102 and 1104 may transmit respectively frames 1118-1 and 1118-2 to STAs 1106 and 1108, respectively. Frames 1118-1 and 1118-2 may comprise multi-AP null data PPDU (NDP) frames. STAs 1106 and 1108 receive frames 1118-1 and 1118-2 respectively and perform channel estimation of the channels from AP 1102 to STA 1106 and from AP 1104 to STA 1108, respectively.

[0162] During the second subphase 1112, APs may initiate a procedure for STAs to feed back channel estimates to the APs. For example, AP 1102 may transmit a frame 1120 to trigger STAs 1106 and 1108 to transmit their channel estimates to APs 1102 and 1104, respectively. Frame 1120 may comprise a multi-AP trigger frame. In response, STAs 1106 and 1108 may transmit respectively frames 1122 and 1124 including feedback of channel estimates to APs 1102 and 1104, respectively. Frames 1122 and 1124 may comprise NDP feedback frames. The feedback of channel estimates may include NDP feedback, CSI-related information, a beamforming report (BFR), or a channel quality indication (CQI) report.

[0163] FIG. 12 illustrates an example 1200 of a multi-AP downlink data transmission phase. Multi-AP downlink data transmission phase 1200 may be an example of multi-AP data transmission phase 1016. As shown in FIG. 12, example 1200 may include a master AP 1202 and a slave AP 1204 of a multi-AP group. Example 1200 may further include a STA 1206 associated with AP 1202, and a STA 1208 associated with AP 1204.

[0164] As shown in FIG. 12, multi-AP downlink data transmission phase 1200 may include frame exchanges to enable master AP 1202 to coordinate with slave AP 1204 to perform specific multi-AP transmission schemes with their associated STAs 1206 and 1208, respectively. The multi-AP transmission schemes may include COFDMA, CTDMA, CSR, CBF, JT/JR, or a combination of two or more of the aforementioned schemes.

[0165] As shown in FIG. 12, master AP 1202 may begin phase 1200 by transmitting a frame 1210 to AP 1204. Frame 1210 may include information related to AP 1204 (e.g., an identifier of AP 1204), synchronization information, information related to a specific multi-AP transmission scheme to be used, and/or information related to a resource unit (RU) for use by AP 1204 to acknowledge frame 1210. Frame 1210 may comprise a control frame. For example, frame 1210 may comprise a multi-AP trigger frame.

[0166] Slave AP 1204 may receive frame 1210 and may use the synchronization information to synchronize with master AP 1202. Subsequently, APs 1202 and 1204 may perform data transmission to their associated STAs 1206 and 1208, respectively. Specifically, AP 1202 may transmit a data frame 1212 to its associated STA 1206, and AP 1204 may transmit a data frame 1214 to its associated STA 1208. Depending on the multi-AP transmission scheme being used, APs 1202 and 1204 may transmit frames 1212 and 1214 respectively to STAs in different BSSs. For example, when the multi-AP transmission scheme is JT/JR, AP 1202 may also transmit frame 1212 to STA 1208 associated with slave AP 1204, and AP 1204 may also transmit frame 1214 to STA 1208 associated with AP 1204. The resources for transmitting and receiving frames 1212 and 1214 may depend on the specific multi-AP transmission scheme adopted.

[0167] STAs 1206 and 1208 may acknowledge frames 1212 and 1214, respectively. For example, STA 1206 may transmit a frame 1216 to AP 1202, and STA 1208 may transmit a frame 1218 to AP 1204. Frames 1216 and 1218 may comprise block ack (BA) frames. STAs 1206 and 1208 may also transmit frames 1216 and 1218 to APs in different BSSs, when required by the used multi-AP transmission scheme. For example, when the multi-AP transmission scheme is JT/JR, STA 1206 may also transmit frame 1216 to AP 1204, and STA 1208 may also transmit frame 1218 to AP 1202. The resources for transmitting and receiving frames 1216 and 1218 may depend on the specific multi-AP transmission scheme adopted.

[0168] FIG. 13 illustrates an example 1300 of a multi-AP uplink data transmission phase. Multi-AP uplink data transmission phase 1300 may be an example of multi-AP data transmission phase 1016. As shown in FIG. 13, example 1300 may include a master AP 1302 and a slave AP 1304 of a multi-AP group. Example 1300 may further include STAs 1306 and 1308 associated with AP 1302, and a STA 1310 associated with AP 1304.

[0169] As shown in FIG. 13, multi-AP uplink data transmission phase 1300 may include frame exchanges to enable master AP 1302 to coordinate with slave AP 1304 to perform specific multi-AP transmission schemes with STAs 1306, 1308, and 1310. The multi-AP transmission schemes may include COFDMA, CTDMA, CSR, CBF, JT/JR, or a combination of two or more of the aforementioned schemes.

[0170] As shown in FIG. 13, master AP 1302 may begin phase 1300 by transmitting a frame 1312 to AP 1304. Frame 1312 may include information related to AP 1304 (e.g., an identifier of AP 1304), synchronization information, information related to a specific multi-AP transmission scheme to be used, and/or information related to an RU for use by AP 1304 to acknowledge frame 1312. Frame 1312 may comprise a control frame. For example, frame 1312 may comprise a multi- AP trigger frame. [0171] Slave AP 1304 may receive frame 1312 and may use the synchronization information to synchronize with master AP 1302. Subsequently, APs 1302 and 1304 may solicit uplink data transmissions from their associated STAs 1306, 1308 and 1310 using trigger frames. Specifically, AP 1302 may transmit a trigger frame 1314 to its associated STAs 1306 and 1308, and AP 1304 may transmit a trigger frame 1316 to its associated STA 1310. Depending on the multi-AP transmission scheme being used, APs 1302 and 1304 may also transmit frames 1314 and 1316 respectively to STAs in different BSSs. For example, when the multi-AP transmission scheme is JT/JR, AP 1302 may also transmit frame 1314 to STA 1310 associated with slave AP 1304, and AP 1304 may also transmit frame 1316 to STAs 1306 and 1308 associated with AP 1302. The resources for transmitting and receiving frames 1314 and 1316 may depend on the specific multi-AP transmission scheme adopted.

[0172] STAs 1306 and 1308 may respond to frame 1314, STA 1310 may respond to frame 1316. For example, STAs 1306 and 1308 may transmit frames 1318 and 1320 respectively to AP 1302, while STA 1310 may transmit a frame 1322 to AP 1304. Frames 1318, 1320, and/or 1322 may be transmitted simultaneously. Frames 1318, 1320, and 1322 may comprise data frames or null data frames. STAs 1306, 1308, and 1310 may also transmit frames 1318, 1320, and 1322 respectively to APs in different BSSs, when required by the used multi-AP transmission scheme. For example, when the multi-AP transmission scheme is JT/JR, STAs 1306 and 1308 may also transmit respective frames 1318 and 1320 toAP 1304, and STA 1310 may also transmit frame 1322 to AP 1302. The resources for transmitting and receiving frames 1318, 1320, and 1322 may depend on the specific multi-AP transmission scheme adopted. AP 1302 may acknowledge frames 1318 and 1320 by transmitting a multi-STA BA frame 1324 to STAs 1306 and 1308. AP 1304 may acknowledge frame 1322 by transmitting a BA frame 1326 to STA 1310.

[0173] EDOA 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 EDOA, 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 (SIFS) duration of receiving the PPDU.

[0174] FIG. 14 illustrates a non-High Throughput (non-HT) PPDU 1410, a HT-Mixed Mode PPDU 1420, and Very High Throughput (VHT) PPDU 1430.

[0175] Non-HT PPDU 1410 may be used by STAs conforming to the IEEE 802.11a standard amendment. As shown in FIG. 14, non-HT PPDU 1410 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 1410.

[0176] The L-STF may be used by a receiver of non-HT PPDU 1410 to synchronize with the carrier frequency and frame timing of a transmitter of non-HT PPDU 1410 and to adjust the receiver signal gain. The L-LTF may be used by the receiver of non-HT PPDU 1410 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 1410.

[0177] The L-SIG contains parameters needed to demodulate the Data field, which contains a payload of non-HT PPDU 1410. 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).

[0178] For non-HT PPDUs, the only supported bandwidth is 20M Hz, which is divided into 64 subcarriers. As such, non- HT PPDU 1410 may be encoded using a subcarrier spacing of 20MHz/64 or 312.5kHz.

[0179] HT-Mixed Mode PPDU 1420 may be used by STAs conforming to the IEEE 802.11n standard amendment. HT- Mixed Mode PPDU 1420 can support MIMO to up to 4 spatial streams, which enhances spectral efficiency four folds. HT- Mixed Mode PPDU 1420 has a minimum preamble duration of 35.6 pis, which may increase depending on the number of spatial streams carried by the PPDU.

[0180] As shown in FIG. 14, HT-Mixed Mode PPDU 1420 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 pis carry symbol information while the remaining 0.4 pis or 0.8 pis carry a Gl. The 0.4 pis long Gl is called short Gl while the 0.8 pis long Gl is called regular or normal Gl.

[0181] For HT-Mixed Mode PPDUs, two bandwidths, 20 MHz and 140 MHz, may be supported. When the PPDU bandwidth is 20 M Hz, the band is divided into 64 subcarriers. When the PPDU bandwidth is 140 MHz, the band is divided into 128 subcarriers. In both cases, subcarrier spacing of 312.5 kHz is maintained.

[0182] VHT PPDU 1430 may be used by STAs conforming to the IEEE 802.11 ac standard amendment. VHT PPDU 1430 can support MIMO to up to 8 spatial streams, which enhances spectral efficiency eight folds. VHT PPDU 1430 has a minimum preamble duration of 39.6 pis, which may increase depending on the number of spatial streams carried by the VHT PPDU 1430.

[0183] As shown in FIG. 14, VHT PPDU 1430 includes an L-STF, an L-LTF, an L-SIG, a VHT Signal A field (VHT-SIG- 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 1430 include of one or more symbols each having a duration of 3.6 pis or 4 pis. In both cases, 3.2 pis carry symbol information while the remaining 0.4 pis or 0.8 pis carry of the Gl. The 0.4pis long Gl is called the short Gl while the 0.8pis long is called regular or normal Gl.

[0184] For VHT PPDUs, four bandwidths, 20 MHz, 140 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. [0185] FIG. 15 illustrates a High Efficiency (HE) Single User (SU) PPDU 1510, an HE Multi-user (MU) PPDU 1520, and an HE Extended Range (ER) SU PPDU 1530. HE SU PPDU 1510, HE MU PPDU 1520, and HE ERSU PPDU 1530 may be used by STAs conforming to the IEEE 802.11 ax standard amendment.

[0186] HE SU PPDU 1510 supports higher spectral efficiency compared to VHT PPDU 1430 due to increased subcarrier spacing and higher order modulation support. HE SU PPDU 1510 has a minimum preamble duration of 44 pis. [0187] As shown in FIG. 15, HE SU PPDU 1510 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.

[0188] Similar to HE SU PPDU 1510, HE MU PPDU 1520 supports higher spectral efficiency compared to VHT PPDU 430. HE MU PPDU 1520 also supports OFDMA. Due to denser subcarrier spacing (as in HE SU PPDU 1510), HE MU PPDU 1520 allows for payloads of multiple users to be multiplexed in the frequency domain in the data field. HE MU PPDU 1520 supports multiplexing the payloads of up to 9 users in a single 20MHz band. HE MU PPDU 1520 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 1520.

[0189] As shown in FIG. 15, HE MU PPDU 1520 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 1510, HE MU PPDU 1520 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 1520.

[0190] For HE SU PPDU 1510 and HE MU PPDU 1520, 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.

[0191] For both HE SU PPDU 1510 and HE MU PPDU 1520, 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 1510 or HE MU PPDU 1520, 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.

[0192] As shown in FIG. 15, HE ER SU PPDU 1530 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 410, HE ER SU PPDU 1530 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. [0193] FIG. 16 illustrates an Extremely High Throughput (EHT) Multi-user (MU) PPDU 1600. EHT MU PPDU 1600 may be used by STAs conforming to the IEEE 802.11 be standard amendment. EHT MU PPDU 1600 supports OFDMA but up to a bandwidth of 320MHz. EHT MU PPDU 1600 further improves spectral efficiency due to a support of an even higher order modulation compared to other PPDUs (e.g., HE SU PPDU 1510 and HE MU PPDU 1520) while supporting the same number of spatial streams. EHT MU PPDU 1600 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 1600.

[0194] As shown in FIG. 15, EHT MU PPDU 1600 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 1600 may be used by a transmitting STA for both SU and MU transmissions.

[0195] The U-SIG is intended to ensure forward compatibility of EHT MU PPDU 1600. 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 802.11 be STAs will be able to understand at least in part a PPDU developed in a future amendment.

[0196] 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 1600.

[0197] The Gl portion of the EHT-LTF and data fields of EHT MU PPDU 1600 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.

[0198] 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 1530 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 1600, 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.

[0199] FIG. 17 illustrates an example multi-user request-to-send (MU-RTS) trigger frame 1700. MU-RTS trigger frame 1700 may be used by an AP to solicit simultaneous GTS frames from multiple STAs to transmit a downlink (DL) MU PPDU to the multiple STAs. As shown in FIG. 17, example MU-RTS trigger frame 1700 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 SIFS periods.

[0200] 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. 17, one or more of the following subfields: trigger type, UL length, more TF, OS 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.

[0201] The trigger type subfield indicates that frame 1700 is an MU-RTS trigger frame.

[0202] 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.

[0203] 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. 17, one or more of the following subfields: AID12, RU allocation, allocation duration, reserved, or PS160.

[0204] The AID12 subfield may indicate an association identifier (AID) of a STA that may use a time indicated by the allocation duration subfield.

[0205] The RU allocation subfield may indicate the location and size of the RU allocated for a STA indicated by the AID12 subfield.

[0206] The allocation duration subfield may indicate a time allocated by an AP transmitting MRTT frame 1700. The allocated time may be a portion a TXOP obtained by the AP.

[0207] FIG. 18 illustrates an example block acknowledgment request (BlockAckReq or BAR) frame 1800. As shown in FIG. 18, example BAR frame 1800 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.

[0208] The frame control and FCS fields may be similar to the corresponding fields of trigger frame 500 described above.

[0209] The Duration/ID field is set to the estimated time required to transmit.

[0210] one Ack or BlockAck frame, as applicable, plus one SIFS

[0211] The RA field indicates the address of a recipient STA of BAR frame 1800.

[0212] The TA field indicates the address of a STA transmitting BAR frame 1800 or a bandwidth signaling TA. [0213] The BAR control field includes a first reserved subfield, a BAR type subfield, a second reserved subfield, and a TIDJNFO subfield.

[0214] The BAR type subfield of the BAR control field indicates a frame variant of BAR frame 1800. 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-GOR) BlockAckReq frame variant. The values 0, 4-5, 7-9, and 11-15 are currently reserved.

[0215] 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 TIDJNFO subfield of the BAR Control field of the Compressed BlockAckReq frame contains the TID for which a BlockAck frame is requested.

[0216] 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.

[0217] FIG. 19 illustrates an example 1900 of a power save (PS) mode. As shown in FIG. 19, example 1900 includes STAs 1902 and 1904. STAs 1902 and 1904 may each be an AP STA or a non-AP STA. It is assumed that STA 1904 implements the PS mode illustrated in FIG. 19, which may be denoted as a dynamic PS mode or a low power listening (LPL) mode.

[0218] In an implementation, a STA (AP STA or non-AP STA) implementing the PS mode illustrated in FIG. 19 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.

[0219] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 310 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, an ultra-high reliability (UHR) PPDU, ora 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.

[0220] 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/mode 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.

[0221] In an implementation, as illustrated in example 1900, 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. 19, STA 1904, 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 1902. Specifically, STA 1902 may transmit an initial control frame (IGF) 1906 to STA 1904 requesting that STA 1904 transition from the first power state/mode to the second power state/mode of the PS mode. STA 1902 may request that STA 1904 transition from the first power state/mode to the second power state/mode in order to transmit to STA 1904 a PPDU 1910 of the second category that STA 1904 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 1906 may be a request to send (RTS) frame, a multiuser RTS (MU-RTS) frame or a BlockAck Request (BAR) frame. IGF 1906 may be carried in a PPDU of the first category. In an implementation, IGF 1906 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, IGF 1906 may include signaling indicating the PPDU bandwidth.

[0222] On receiving IGF 1906, STA 1904 initiates a transition from the first power state/mode to the second power state/mode. For example, on receiving IGF 1906, STA 1904 may enable/poweron receiver capabilities needed to receive the PPDU of the second category that STA 1902 wishes to transmit to STA 1904. The transition from the first power state/mode to the second power state/mode may be associated with a state/mode transition duration. The state/mode transition duration may depend on the processing capabilities of STA 1904. In an implementation, STA 1902 may include padding in IGF 1906 to allow STA 1904 to transition from the first power state/mode to the second power state/mode in a timely manner. Hence, as shown in FIG. 19, STA 1904 may start the state/mode transition before the reception of IGF 1906 is completed (i.e. without decoding the padding information).

[0223] In an implementation, STA 1904 responds to IGF 1906 by transmitting an initial control response (ICR) 1908 to STA 1902. ICR 1908 informs STA 1902 that STA 1904 is transitioning from the first power state/mode to the second power state/mode. In an implementation, as shown in FIG. 19, STA 1904 may transmit ICR 1908 while transitioning from the first power state/mode to the second power state/mode. In an implementation, STA 1904 may transmit ICR 1908 after completing the transition from the first power state/mode to the second power state/mode. Completing the transition before transmitting ICR 1908 may enable STA 1904 to perform clear channel assessment over a bandwidth that is higher than 20 MHz. This may enable STA 1904 to transmit ICR 1908 on idle channels with bandwidths higher than 20 MHz, which improves hidden node protection due to the transmission of ICR 1908. In another implementation, STA 1904 may transmit ICR 1908 before completing the transition to the second power state/mode. In such an implementation, STA 1904 may only be able to transmit ICR 1908 using a bandwidth of 20 MHz. ICR 1908 may be carried in a PPDU of the first category or the second category. In an implementation, STA 1904 transmits ICR 1908 a short interframe space (SIFS) after receiving ICF 1906.

[0224] On receiving ICR 1908, STA 1902 initiates transmission of PPDU 1910. In an implementation, STA 1902 transmits PPDU 1910 a SIFS after receiving ICR 1908. In an implementation, STA 1902 may begin transmitting PPDU 1910 while STA 1904 is still transitioning from the first power state/mode to the second power state/mode. PPDU 1910 may thus include a first PPDU part 1914 of the first category and a second PPDU part 1916 of the second category. In another implementation, STA 1902 may begin transmitting PPDU 1910 after STA 1904 has transitioned to the second power state/mode. PPDU 1910 may thus be entirely of the second category.

[0225] After receiving PPDU 1910, STA 1904 may transmit a BA frame 1912 to STA 1902. In an implementation, STA 1904 may return to the first power state/mode after receiving PPDU 1910. STA 1904 may transmit BA frame 1912 while in the second power state/mode or after returning to the first power state/mode.

[0226] FIG. 20 illustrates an example 2000 of an AP implementation of the PS mode illustrated in FIG. 19. As shown in FIG. 20, example 2000 includes an AP 2002 and a STA 2004. STA 2004 may be associated with AP 2002. It is assumed that AP 2002 implements the PS mode illustrated in FIG. 19. Specifically, as described above, while in the first power state/mode of the PS mode, AP 2002 is capable of receiving PPDUs of a first category; and while in the second power state/mode of the PS mode, AP 2002 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. 19.

[0227] Additionally, AP 2002 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 2002 may be capable of receiving PPDUs of the first category and/or of the second category in any power state/mode.

[0228] In an implementation, AP 2002 may be configured to announce a time period during which AP 2002 will operate in the PS mode. For example, as shown in FIG. 20, during a first time period, AP 2002 may transmit a frame 2006 indicating or announcing a second time period during which AP 2002 will operate in the PS. The second time period may or may not be adjacent to the first time period. In an implementation, AP 2002 may be operating in the other mode during the first time period. In another implementation, AP 2002 may be operating in the PS mode during the first time period. Frame 2006 may indicate a start time T1 and an end time T2 of the second time period. Alternatively, frame 2006 may indicate a start time T1 and a duration of the second time period.

[0229] In an example, as shown in FIG. 20, AP 2002 may be in the other mode before switching to the PS mode at the beginning of the second time period. In an implementation, AP 2002 may be configured, upon switching to the PS mode from the other mode, to operate in a default state/mode of the PS mode. In an implementation, the default state/mode may be the first power state/mode as described above. In another example, not shown in FIG. 20, AP 2002 be in the second power state/mode of the PS mode before the beginning of the second time period. AP 2002 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. [0230] In an implementation, as illustrated in example 2000, AP 2002 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. 20, after switching to the PS mode at the beginning of the second time period, AP 2002 may operate in the first power state/mode. Subsequently, AP 2002 receives an IGF 2008 requesting that AP 2002 transition from the first power state/mode to the second power state/mode to receive from STA 2004 a PPDU 2012 of the second category. On receiving IGF 2008 from STA 2004, AP 2002 may respond with an ICR 2010 and may initiate a transition from the first power state/mode to the second power state/mode.

[0231] In an implementation, AP 2002 may determine, from IGF 2008, a TXOP duration, a bandwidth, and/or a modulation and coding scheme (MOS) of PPDU 2012. AP 2002 may turn on/enable receiver capabilities based on the bandwidth and MOS indicated in IGF 2008. In an implementation, AP 2002 may use the TXOP duration and the bandwidth indicated in IGF 2008 to reserve a suitable channel for PPDU 2012. For example, PPDU 2012 may have a bandwidth of 80 MHz and AP 2002 may reserve a primary 80 MHz channel for PPDU 2012. In an implementation, AP 2002 may perform a clear channel assessment (CCA) procedure over the channel to be used by STA 2004 for the transmission of PPDU 2012. After a successful CCA procedure, AP 2002 may transmit an ICR 2010 to STA 2004. ICR 2010 may be configured to reserve the channel to be used by STA 2004 for the transmission of PPDU 2012. In an implementation, ICR 2010 may be a clear to send (GTS) frame that indicates the channel to be used by STA 2004 for the transmission of PPDU 2012.

[0232] On receiving ICR 2010, STA 2004 initiates transmission of PPDU 2012. In an implementation, STA 2004 transmits PPDU 2012 a SIFS after receiving ICR 2010. After receiving PPDU 2012, AP 2002 may transmit a BA frame 2014 to STA 2004. In an implementation, AP 2002 may return to the first power state/mode after receiving PPDU 2012. AP 2002 may transmit BA frame 2014 while in the second power state/mode or after returning to the first power state/mode. After the second time period, AP 2002 may transition to the other mode of operation or may remain in the first power state/mode of the PS mode.

[0233] FIG. 21 illustrates an example 2100 that highlights a problem that may arise in association with the power save mode illustrated in FIG. 20.

[0234] As shown in FIG. 21, example 2100 may include AP 2102 and STA 2104. STA 2104 may be associated with AP 2102. It is assumed that AP 2102 supports the PS mode illustrated in FIG. 19. Specifically, as described above, while in the first power state/mode of the PS mode, AP 2102 is capable of receiving PPDUs of a first category; and while in the second power state/mode of the PS mode, AP 2102 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. 19.

[0235] Similar to AP 2002 described in FIG. 20, AP 2102 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 2102 may be capable of receiving PPDUs of the first category and/or of the second category in any power state/mode. [0236] It is further assumed that STA 2104 does not support operating with AP 2102 operating in the PS mode described in FIG. 19. For example, STA 2104 may not have the capability to solicit AP 2102 to transition from the first power state/mode to the second power state/mode of the PS mode as described above. In an example, STA 2104 may comprise a legacy STA.

[0237] As shown in FIG. 21, example 2100 may begin with AP 2102 transmitting a frame 2110 using EDOA during a period 2106 ending by a time T1. In an example, during period 2106, AP 2102 may operate in the other mode. In another example, during period 2106, AP 2102 may operate in the second power state/mode of the PS mode.

[0238] In an example, frame 2110 may comprise capability information of AP 2102 indicating support by AP 2102 of the PS mode illustrated in FIG. 19. In an example, frame 2110 may indicate that AP 2102 operates in the PS mode during a period 2108. Period 2108 may start at time T1 and end at a time T2. Frame 2110 may comprise a management frame indicating a broadcast address. In an implementation, frame 2110 may comprise a beacon frame. STA 2104 may receive frame 2110 and may determine period 2108 during which AP 2102 is scheduled to operate in the PS mode.

[0239] During period 2106, STA 2104 may perform EDOA to initiate an association procedure. STA 2104 may transmit to AP 2102 an association request frame 2112 requesting association with AP 2102. AP 2102 may receive association request frame 2112 and may transmit in response an association response frame 2114 to STA 2104. In an example, association response frame 2114 may indicate acceptance of association request frame 2112.

[0240] As mentioned above, STA 2104 does not support operating with AP 2102 operating in the PS mode. As such, in an implementation, upon STA 2104 associating with AP 2102 during period 2106, AP 2102 may determine not to enter into the PS mode at T1 in order to continue to be able to serve STA 2104. In an example, STA 2104 may be the only STA associated with AP 2102 that does not support operating with AP 2102 operating in the PS mode. In an example, AP 2102 may continue to operate in the other mode during period 2108. In another example, AP 2102 may transition from the second state/mode of the PS mode to the other mode. As such, AP 2102 may be precluded from operating in the PS mode during period 2108 and may not leverage its support of the PS mode to reduce its power consumption.

[0241] In example 2100, during period 2108, data may arrive at STA 2104 for transmission to AP 2102. STA 2104 may perform EDOA and transmit to AP 2102 a PPDU 2118 carrying the data. In an implementation, PPDU 2118 may comprise a non-trigger based (non-TB) PPDU. 2102 may transmit an acknowledgment frame 2120 to STA 2104 in response to PPDU 2118. In an example, acknowledgment frame 2120 may comprise a BA frame.

[0242] Embodiments of the present disclosure, as further described below, address the above-described problems of existing power save procedures. In an aspect, a first AP in a power save mode may receive from a second AP a notification of reception by the second AP of a first PPDU transmitted by a STA to the first AP. The power save mode may comprise a dynamic PS mode or a low-power listening (LPL) mode, for example. Before receiving the notification of reception, the first AP may transmit to the second AP a request for the second AP to monitor/receive PPDUs addressed to the first AP. The request may further comprise a first request for the second AP to transmit the notification reception to the first AP. The first AP may receive from the second AP a first response to the request. In an embodiment, the first AP transitions from another mode of operation to a first power state/mode of the power save mode. The other mode may correspond to an active mode or to a power saving mode different than the PS mode. The other mode may have one or more power state/modes. The first AP 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. The first 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 first power state/mode, the first AP may be capable of receiving PPDUs of a first category. Based on the notification, the first AP may transition from the first power state/mode to a second power state/mode. The second 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 second power state/mode, the first AP may be capable of receiving PPDUs of the first category and PPDUs of a second category. The first AP may receive a second PPDU addressed to the first AP.

[0243] FIG. 22 illustrates an example 2200 of an inter-AP notification procedure 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 includes an AP 2202, an AP 2204, and a STA 2206. In an example, STA 2206 may be associated with AP 2202. AP 2202, AP 2204, and/or STA 2206 may each comprise a multi-link device (MLD).

[0244] In an implementation, APs 2202 and 2204 may belong to the same ESS as described above in FIG. 1. In such a case, APs 2202 and 2204 may be connected by a DS to support ESS features. In an example, APs 2202 and 2204 belong to different BSSs. In an embodiment, AP 2202 may belong to a first BSS and AP 2204 may belong to a second BSS. In an embodiment, the second BSS may comprise an overlapping basic service set (OBSS) relative to the first BSS. [0245] In an embodiment, AP 2202 and 2204 may form a multi-AP group. AP 2202 may be a sharing/master AP of the multi-AP group. AP 2204 may be a shared/slave AP of the multi-AP group. It is assumed in example 2200, APs 2202 and 2204 may complete a multi-AP setup procedure prior to the beginning of example 2200. In addition, as part of a multi-AP group, APs 2202 and 2204 may be connected by a backhaul. In an example, the backhaul may be a wireless backhaul. [0246] In an embodiment, before the beginning of example 2200, AP 2202 and AP 2204 may complete a multi-AP selection phase (not shown in FIG. 22), such as multi-AP selection phase 1010 described in FIG. 10 above.

[0247] It is assumed in example 2200 that AP 2202 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.

[0248] In an implementation, AP 2202 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, AP 2202 is capable of receiving PPDUs of a first category. While in the second power state/mode, AP 2202 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, AP 2202 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, AP 2202 is capable of receiving PPDUs of only the first category during the first power state/mode. [0249] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 1410 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, an ultra-high reliability (UHR) PPDU, ora 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.

[0250] AP 2202 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 the STA, the first power state/mode may correspond to a default state/mode 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.

[0251] Similar to AP 2002 described in FIG. 20, AP 2202 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. AP 2202 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.

[0252] It is further assumed in example 2200 that STA 2206 does not support operating with AP 2202 operating in the PS mode. For example, STA 2206 may not have the capability to solicit AP 2202 to transition from the first power state/mode to the second power state/mode of the PS mode as described above. In an example, STA 2206 may comprise a legacy STA.

[0253] It is assumed in example 2200 that AP 2202 supports an inter-AP notification capability AP 2202 supporting the inter-AP notification capability may include AP 2202 having the capability to receive from another AP a frame (such as frame 2224 described below) comprising a notification of reception by the other AP of a first PPDU addressed to AP 2202 (such as PPDU 2222 transmitted by STA 2206) while AP 2202 is in the PS mode. In an example, the power save mode may comprise a LPL mode.

[0254] It is also assumed in example 2200 that AP 2204 supports the inter-AP notification capability. AP 2204 supporting the inter-AP notification capability may include AP 2204 having the capability to monitor/receive PPDUs addressed to another AP (such as AP 2202), such as a PPDU (e.g., PPDU 2222) addressed to the other AP from a STA (e.g., STA 2206) associated with the other AP. In an example, AP 2204 supporting the inter-AP notification capability may further include AP 2204 having the capability to transmit to the other AP a frame (such as frame 2224 described below) comprising a notification of reception of the first PPDU.

[0255] In an embodiment, prior to the beginning of example 2200, APs 2202 and 2204 may exchange a first frame and a second frame (not shown in FIG.22) to exchange capability information. In an embodiment, the first frame may comprise the capability information of AP 2202, including a first indication of support by AP 2202 of the inter-AP notification capability In an embodiment, the second frame may comprise the capability information of AP 2204, including a second indication of support by AP 2204 of the inter-AP notification capability. In an embodiment, the first frame and the second frame may be exchanged during a multi-AP setup procedure or a multi-AP selection phase. In an embodiment, the first frame and the second frame may comprise a management frame.

[0256] As shown in FIG. 22, the procedure may begin with AP 2202 transmitting a frame 2220 using EDOA during a period 2210 ending by a time T1. In an example, during period 2210, AP 2202 may operate in the other mode or in the second power state/mode of the PS mode.

[0257] In an example, frame 2220 may comprise capability information of AP 2202 indicating support by AP 2202 of the PS mode illustrated in FIG. 22. In an example, frame 2220 may indicate that AP 2202 operates in the PS mode during a period 2212. Period 2212 may start at time T1 and end at a time T4. Frame 2220 may comprise a management frame indicating a broadcast address. In an implementation, frame 2220 may comprise a beacon frame. In an embodiment, frame 2220 and the first frame used for capability exchange may be the same frame. In another embodiment, frame 2220 and the first frame may be an aggregated frame. STA 2206 may receive frame 2220 and may determine period 2212 during which AP 2202 is scheduled to operate in the PS mode. In an example, AP 2204 may receive frame 2220.

[0258] In an embodiment, based on receiving frame 2220 indicating that AP 2202 operates in the PS mode during period 2212, AP 2204 may be configured to start to receive/monitor PPDUs addressed to AP 2202 during period 2212. In an embodiment, PPDUs addressed to AP 2202 may comprise PPDUs indicating an address of AP 2202 or an identifier ofAP 2202.

[0259] In an example, after AP 2202 begins operating in the PS mode at time T1, STA 2206 may have data arrive for transmission to AP 2202 during a period 2214, e.g., beginning at time T1 and ending at a time T2, of period 2212. In an example, AP 2202 may be operating in the first power state/mode of the PS mode during period 2214.

[0260] In example 2200, STA 2206 may transmit a PPDU 2222 to AP 2202 carrying the data for AP 2202. In an example, PPDU 2222 may be of the second category that AP 2202 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).

[0261] AP 2204 may receive PPDU 2222 addressed to AP 2202. In an embodiment, AP 2204 may be configured to transmit to AP 2202 a notification of reception of PPDU 2222. In example 2200, AP 2204 transmits to AP 2202 a frame 2224 comprising the notification of reception of PPDU 2222. In an embodiment, frame 2224 may be carried by a PPDU of the first category that AP 2202 is capable of receiving during the first power state/mode (e.g., a non-HT PPDU, a PPDU having a data rate that is less than or equal to 24 Mbps, a bandwidth of 20 MHz, and/or a single spatial stream). In an embodiment, frame 2224 may indicate that PPDU 2222 is of the second category and/or that PPDU 2222 is transmitted by STA 2206.

[0262] In an embodiment, frame 2224 may comprise a control frame. In an example, the control frame may comprise a trigger frame. In an example, the trigger frame may comprise a MU-RTS trigger frame. In another example, the control frame may comprise a block ack request (BAR) frame. In another example, the control frame may comprise an initial control frame (IGF). In an embodiment, frame 2224 may comprise a management frame. In an example, the management frame may comprise an action frame. In an embodiment, frame 2224 may comprise a data frame. In an example, the data frame may comprise a QoS null frame.

[0263] In an example, where AP 2202 operates in the first power state/mode during period 2214 and where PPDU 2222 is of the second category, AP 2204 may not be capable of receiving PPDU 2222 from STA 2206. However, AP 2202 may receive and process frame 2224 from AP 2204. In an embodiment, based on receiving frame 2224, AP 2202 may be configured to transition from the first power state/mode to the second power state/mode. In example 2200, AP 2202 may transition from the first power state/mode to the second power state/mode at a time T2. AP 2202 may operate in the second power state/mode during a period 2216 starting from T2 and ending at a time T3. In an embodiment, AP 2202 may optionally transmit an acknowledgment frame 2226 in response to frame 2224. AP 2202 may transmit acknowledgment frame 2226 before or after transitioning to the second power state/mode.

[0264] As shown in FIG. 22, in an example, after AP 2202 transitions to the second power state/mode, STA 2206 may perform EDOA and transmit to AP 2202 a PPDU 2228. PPDU 2208 may be of the second category that AP 2202 is capable of receiving during the second power state/mode. In an embodiment, PPDU 2228 may comprise a retransmission of PPDU 2222. In another example, after AP 2202 transitions to the second power state/mode, a second STA (not shown in FIG. 22) may transmit PPDU 2228 to AP 2202.

[0265] AP 2202 may receive and process PPDU 2228 during period 2216. In an embodiment, AP 2202 may transmit an acknowledgment frame 2230 to STA 2206 in response to PPDU 2228. Frame 2230 may comprise a BA frame. In an embodiment, as shown in FIG. 22, AP 2202 may transition from the second power state/mode to the first power state/mode after transmitting frame 2230 at time T3. AP 2202 may operate in the first power state/mode for at least a period 2218 starting at T3 and ending at a time T4.

[0266] As illustrated by example 2200, by supporting the inter-AP notification capability, AP 2202 is able to operate in the PS mode during period 2212 despite having STA 2206 that does not support PS mode operation being associated with AP 2202. AP 2202 transitions from the first power state/mode to the second power state/mode based on receiving frame 2224 from AP 2204. AP 2202 may operate otherwise in the first power state/mode, which allows AP 2202 to reduce its power consumption while operating in the PS mode.

[0267] FIG. 23 illustrates an example 2300 of an inter AP notification procedure 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 includes an AP 2302, an AP 2304, and a STA 2306. In an example, STA 2306 may be associated with AP 2302. AP 2302, AP 2304, and/or STA 2306 may each comprise a multi-link device (MLD).

[0268] In an implementation, APs 2302 and 2304 may belong to the same ESS as described above in FIG. 1. In such a case, APs 2302 and 2304 may be connected by a DS to support ESS features. In an example, APs 2302 and 2304 belong to different BSSs. In an embodiment, AP 2302 may belong to a first BSS and AP 2304 may belong to a second BSS. In an embodiment, the second BSS may comprise an overlapping basic service set (OBSS) relative to the first BSS. [0269] In an embodiment, AP 2302 and 2304 may form a multi-AP group. AP 2302 may be a sharing/master AP of the multi-AP group. AP 2304 may be a shared/slave AP of the multi-AP group. It is assumed in example 2300, APs 2302 and 2304 may complete a multi-AP setup procedure prior to the beginning of example 2300. In addition, as part of a multi-AP group, APs 2302 and 2304 may be connected by a backhaul. In an example, the backhaul may be a wireless backhaul. [0270] In an embodiment, before the beginning of example 2300, AP 2302 and AP 2304 may complete a multi-AP selection phase (not shown in FIG. 23), such as multi-AP selection phase 1010 described in FIG. 10 above.

[0271] It is assumed in example 2300 that AP 2302 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.

[0272] In an implementation, AP 2302 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, AP 2302 is capable of receiving PPDUs of a first category. While in the second power state/mode, AP 2302 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, AP 2302 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, AP 2302 is capable of receiving PPDUs of only the first category during the first power state/mode.

[0273] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 1410 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, an ultra-high reliability (UHR) PPDU, ora 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.

[0274] AP 2302 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 the STA, the first power state/mode may correspond to a default state/mode 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.

[0275] Similar to AP 2002 described in FIG. 20, AP 2302 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. AP 2302 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. [0276] It is further assumed in example 2300 that STA 2306 does not support operating with AP 2302 operating in the PS mode. For example, STA 2306 may not have the capability to solicit AP 2302 to transition from the first power state/mode to the second power state/mode of the PS mode as described above. In an example, STA 2306 may comprise a legacy STA.

[0277] It is assumed in example 2300 that AP 2302 supports an inter-AP notification capability. AP 2302 supporting the inter-AP notification capability may include AP 2302 having the capability to transmit a frame (such as frame 2320 described below) that requests another AP (such as AP 2304) to monitor/receive PPDUs addressed to AP 2302. AP 2302 supporting the inter-AP notification capability may further include AP 2302 having the capability to transmit the frame (such as frame 2320 described below) to request the other AP to transmit to AP 2302 in a PS mode a notification of reception by the other AP of a first PPDU (such as PPDU 2326 transmitted by STA 2306 to AP 2302). In an example, the PS mode may comprise a LPL mode. AP 2302 supporting the inter-AP notification capability may further include AP 2302 having the capability to receive from the other AP a frame (such as frame 2328 described below) comprising a notification of reception by the other AP while AP 2302 is in the PS mode.

[0278] It is also assumed in example 2300 that AP 2304 supports the inter-AP notification capability. AP 2304 supporting the inter-AP notification capability may include AP 2304 having the capability to receive and process a frame (such as frame 2320) from another AP requesting to monitor/receive PPDUs, such as a PPDU (e.g., PPDU 2326) addressed to the other AP from a STA (e.g., STA 2306) associated with the other AP. AP 2302 supporting the inter-AP notification capability may further include AP 2304 having the capability to transmit to the other AP in a PS mode a notification of reception of a first PPDU (such as PPDU 2326 transmitted by STA 2306 to AP 2302). AP 2304 supporting the inter-AP notification capability may further include AP 2304 having the capability to transmit to the other AP a frame (such as frame 2328 described below) comprising a notification of reception of the first PPDU.

[0279] As illustrated in FIG. 23, example 2300 begin with AP 2302 performing EDOA and transmitting to AP 2304 a request frame 2320 for AP 2304 to monitor/receive PPDUs (e.g. PPDU 2326) addressed to AP 2302. In an embodiment, PPDUs addressed to AP 2302 may comprise PPDUs indicating an address of AP 2302 or an identifier of AP 2302. In an embodiment, request frame 2320 may be for AP 2304 to monitor/receive PPDUs addressed to AP 2302 operating in the first power state/mode.

[0280] In an embodiment, AP 2302 may transmit request frame 2320 during a period 2310 ending by a time T1. In an example, during period 2310, AP 2302 may operate in the other mode. In another example, during period 2310, AP 2302 may operate in the second power state/mode of the PS mode.

[0281] In an embodiment, request frame 2320 may further comprise a first request for AP 2204 to transmit a notification of reception of a first PPDU (e.g. PPDU 2326) addressed to AP 2302. In an embodiment, the first PPDU addressed to AP 2302 may be of the second category that AP 2302 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).

[0282] In an embodiment, request frame 2320 may comprise a management frame. In an example, the management frame may comprise an action frame. [0283] As shown in FIG. 23, AP 2304 may transmit to AP 2302 a response frame 2322 in response to request frame 2320. In an embodiment, response frame 2322 may indicate an acceptance or a rejection. In an embodiment, response frame 2322 may comprise a management frame. In an example, the management frame may comprise an action frame. [0284] As shown in FIG. 23, AP 2302 may transmit a frame 2324 using EDOA during period 2310. In an embodiment, the AP 2302 may transmit frame 2324 before or after transmitting frame 2320. In an example, frame 2324 may comprise capability information of AP 2302 indicating support by AP 2302 of the PS mode illustrated in FIG. 23. In an embodiment, frame 2324 may indicate that AP 2302 operates in the PS mode during a period 2312. Period 2312 may start at time T1 and end at a time T4. Frame 2324 may comprise a management frame indicating a broadcast address . In an implementation, frame 2324 may comprise a beacon frame. In an embodiment, frame 2324 and the first frame used for capability exchange may be the same frame. In an embodiment, frame 2324 and the first frame may be an aggregated frame. In another embodiment, frame 2320 and frame 2324 may be an aggregated frame.

[0285] STA 2306 may receive frame 2324 and may determine period 2312 during which AP 2302 is scheduled to operate in the PS mode. In an example, AP 2304 may receive frame 2324.

[0286] In an embodiment, based on transmitting response frame 2322 indicating an acceptance in response to frame 2320 and receiving frame 2324 indicating that AP 2302 operates in the PS mode during period 2312, AP 2304 may start to receive/monitor PPDUs addressed to AP 2302 during period 2312.

[0287] In an example, after AP 2302 begins operating in the PS mode at time T1, STA 2306 may have data arrive for transmission to AP 2302 during a period 2314, e.g., beginning at time T1 and ending at a time T2, of period 2312. In an example, AP 2302 may be operating in the first power state/mode of the PS mode during period 2314.

[0288] In example 2300, STA 2306 may transmit a PPDU 2326 to AP 2302 carrying the data for AP 2302. In an example, PPDU 2326 may be of the second category that AP 2302 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).

[0289] AP 2304 may receive PPDU 2326 addressed to AP 2302. In an embodiment, based on transmitting response frame 2322 indicating an acceptance of the request in response to frame 2320, AP 2304 may be configured to transmit to AP 2302 a notification of reception of PPDU 2326. In another embodiment, based on transmitting response frame 2322 indicating an acceptance of the first request in response to frame 2320, AP 2304 may transmit to AP 2302 the notification of reception of PPDU 2326. In example, 2300, AP 2304 transmits to AP 2302 a frame 2328 comprising the notification of reception of PPDU 2326. In an embodiment, frame 2328 may be carried by a PPDU of the first category that AP 2302 is capable of receiving during the first power state/mode (e.g., a non-HT PPDU, a PPDU having a data rate that is less than or equal to 24 Mbps, a bandwidth of 20 MHz, and/or a single spatial stream). In an embodiment, frame 2328 may indicate a reception of PPDU 2326 of the second category transmitted by STA 2306.

[0290] In an embodiment, frame 2328 may comprise a control frame. In an example, the control frame may comprise a trigger frame. In an example, the trigger frame may comprise a MU-RTS trigger frame. In another example, the control frame may comprise a block ack request (BAR) frame. In another example, the control frame may comprise an initial control frame (IGF). In an embodiment, frame 2328 may comprise a management frame. In an example, the management frame may comprise an action frame. In an embodiment, frame 2328 may comprise a data frame. In an example, the data frame may comprise a QoS null frame.

[0291] In an embodiment, AP 2304 may determine to transmit frame 2328 based on a comparison of a value of a first field of PPDU 2326 to a first threshold.

[0292] In an embodiment, the first field may indicate a transmission characteristic of PPDU 2326 addressed to AP 2302. In an example, the transmission characteristic may comprise a data rate, a modulation and coding scheme (MOS), a length, a bandwidth (BW), or a number of spatial streams (NSS). In an embodiment, the first field may comprise a rate field. In an example, the value of the first field may comprise a value corresponding to a data rate of PPDU 2326. In an example, the value corresponding to the data rate may comprise a value in bits per second. In an embodiment, the first field may comprise an MOS field. In an example, the value of the first field may comprise a value corresponding to an MOS index of PPDU 2326. In an example, the value corresponding to the MOS index may comprise an integral representation of the MOS index. In an embodiment, the first field may comprise a length field. In an example, the value of the first field may comprise a value corresponding to a length of PPDU 2326. In an example, the value may comprise a value in octet. In an embodiment, the first field may comprise a BW field. In an example, the value of the first field may comprise a value corresponding to a BW of PPDU 2326. In an example, the value corresponding to the BW may comprise a value in Hz. In an embodiment, the first field may comprise an NSS field. In an example, the value of the first field may comprise a value corresponding to a NSS of PPDU 2326. In an example, the value may comprise an integral representation of the NSS.

[0293] In an embodiment, the first threshold may be associated with the first field of the PPDU 2326. In an embodiment, the first request comprised in request frame 2320 may indicate/comprise the first threshold. In another embodiment, frame 2324 may indicate/comprise the first threshold. In an embodiment, the first threshold may comprise a dynamic threshold (e.g., the first threshold may be indicated by AP 2302 before each time that AP 2302 intends to enter the PS mode). In an embodiment, the first threshold may comprise a semi-static threshold (e.g., the first threshold may apply to a pre-determined time duration). In another embodiment (not shown in FIG. 23), the first threshold may comprise a static threshold or pre-configured threshold (e.g., the first threshold may be announced once or may be pre-configured within AP 2304).

[0294] In an example, AP 2304 may compare the value of the first field of PPDU 2326 to the first threshold. Based on the comparison, AP 2304 may or may not transmit frame 2328. For example, assuming that the first field of PPDU 2326 comprises an NSS value and the first threshold indicates an NSS threshold (e.g., 4 spatial streams), AP 2304 may transmit frame 2328 when the NSS value indicated in the first field is lower than the NSS threshold and may not transmit frame 2328 when the NSS value indicated in the first field is higher than the NSS threshold. This allows AP 2302 to remain in the first power state/mode during period 2316, further reducing power consumption of AP 2302.

[0295] In an example, AP 2304 may compare the value of the first field of PPDU 2326 to the first threshold. Based on the comparison, AP 2304 may or may not transmit frame 2328. For example, assuming that the first field of PPDU 2326 comprises an NSS value and the first threshold indicates an NSS threshold (e.g., 4 spatial streams), AP 2304 may transmit frame 2328 when the NSS value indicated in the first field is higher than the NSS threshold and may not transmit frame 2328 when the NSS value indicated in the first field is lower than the NSS threshold. This allows AP 2302 to remain in the first power state/mode during period 2316, further reducing power consumption of AP 2302.

[0296] In an embodiment, AP 2304 may determine to transmit frame 2328 based on the first threshold within a timeout duration starting from AP 2304 receiving the timeout duration. In an embodiment, the first request may further indicate/comprise the timeout duration.

[0297] In an example, where AP 2302 operates in the first power state/mode during period 2314 and where PPDU 2326 is of the second category. AP 2304 may not be capable of receiving PPDU 2326 from STA 2306. However, AP 2302 may receive and process frame 2328. In an embodiment, based on receiving frame 2328, AP 2302 may be configured to transition from the first power state/mode to the second power state/mode. In example 2300, AP 2302 may transition from the first power state/mode to the second power state/mode at a time T2. AP 2302 may operate in the second power state/mode during a period 2316 starting from T2 and ending at a time T3. In an embodiment, AP 2302 may optionally transmit an acknowledgment frame 2330 in response to frame 2328. AP 2302 may transmit acknowledgment frame 2330 before or after transitioning to the second power state/mode.

[0298] As shown in FIG. 23, in an example, after AP 2302 transitions to the second power state/mode, STA 2306 may perform EDOA and transmit to AP 2302 a PPDU 2332. PPDU 2332 may be of the second category that AP 2302 is capable of receiving during the second power state/mode. In an embodiment, PPDU 2332 may comprise a retransmission of PPDU 2326. In another example, after AP 2302 transitions to the second power state/mode, a second STA (not shown in FIG. 23) may transmit PPDU 2228 to AP 2302.

[0299] AP 2302 may receive and process PPDU 2332 during period 2316. In an embodiment, AP 2302 may transmit an acknowledgment frame 2334 to STA 2306 in response to PPDU 2332. Frame 2334 may comprise a BA frame. In an embodiment, as shown in FIG. 23, AP 2302 may transition from the second power state/mode to the first power state/mode after transmitting frame 2330 at time T3. AP 2302 may operate in the first power state/mode for at least a period 2318 starting at T3 and ending at a time T4.

[0300] As illustrated by example 2300, by supporting the inter-AP notification capability, AP 2302 is able to operate in the PS mode during period 2312 despite having STA 2306 that does not support the PS mode operation being associated with AP 2302. AP 2302 receives notification of reception in frame 2324 from AP 2304 based on transmitting request frame 2320. AP 2302 transitions from the first power state/mode to the second power state/mode based on receiving frame 2324 from AP 2304. AP 2302 may operate otherwise in the first power state/mode, which allows AP 2202 to reduce its power consumption while operating in the PS mode.

[0301] FIG. 24 illustrates an example 2400 of an inter AP notification procedure 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 includes an AP 2402, an AP 2404, and an STA 2406. In an example, STA 2406 may be associated with AP 2402. AP 2402, AP 2404, and/or STA 2406 may each comprise a multi-link device (MLD). [0302] In an implementation, APs 2402 and 2404 may belong to the same ESS as described above in FIG. 1. In such a case, APs 2402 and 2404 may be connected by a DS to support ESS features. In an example, APs 2402 and 2404 belong to different BSSs. In an embodiment, AP 2402 may belong to a first BSS and AP 2404 may belong to a second BSS. In an embodiment, the second BSS may comprise an overlapping basic service set (OBSS) relative to the first BSS. [0303] In an embodiment, AP 2402 and 2404 may form a multi-AP group. AP 2402 may be a sharing/master AP of the multi-AP group. AP 2404 may be a shared/slave AP of the multi-AP group. It is assumed in example 2400, APs 2402 and 2404 may complete a multi-AP setup procedure prior to the beginning of example 2400. In addition, as part of a multi-AP group, APs 2402 and 2404 may be connected by a backhaul. In an example, the backhaul may be a wireless backhaul. [0304] In an embodiment, before the beginning of example 2400, AP 2402 and AP 2404 may complete a multi-AP selection phase (not shown in FIG. 24), such as multi-AP selection phase 1010 described in FIG. 10 above.

[0305] It is assumed in example 2400 that AP 2402 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.

[0306] In an implementation, AP 2402 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, AP 2402 is capable of receiving PPDUs of a first category. While in the second power state/mode, AP 2402 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, AP 2402 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, AP 2402 is capable of receiving PPDUs of only the first category during the first power state/mode.

[0307] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 1410 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, an ultra-high reliability (UHR) PPDU, ora 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.

[0308] AP 2402 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 the STA, the first power state/mode may correspond to a default state/mode 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. [0309] Similar to AP 2002 described in FIG. 20, AP 2402 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. AP 2402 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.

[0310] It is further assumed in example 2400 that STA 2406 does not support operating with AP 2402 operating in the PS mode. For example, STA 2406 may not have the capability to solicit AP 2402 to transition from the first power state/mode to the second power state/mode of the PS mode as described above. In an example, STA 2406 may comprise a legacy STA.

[0311] It is assumed in example 2400 that AP 2402 supports an inter-AP notification capability. AP 2402 supporting the inter-AP notification capability may include AP 2402 having the capability to transmit a frame (such as frame 2420 described below) that requests another AP (such as AP 2404) to monitor/receive PPDUs addressed to AP 2402. AP 2402 supporting the inter-AP notification capability may further include AP 2402 having the capability to transmit the frame (such as frame 2420 described below) to request AP 2404 to transmit to AP 2402 in a PS mode a notification of reception by the other AP of a first PPDU (such as PPDU 2426 transmitted by STA 2406 to AP 2402). In an example, the PS mode may comprise a LPL mode. AP 2402 supporting the inter-AP notification capability may further include AP 2402 having the capability to receive from the other AP a frame (such as frame 2428 described below) comprising a notification of reception by the other AP while AP 2402 is in the PS mode.

[0312] It is also assumed in example 2400 that AP 2404 supports the inter-AP notification capability. AP 2404 supporting the inter-AP notification capability may include AP 2404 having the capability to receive and process a frame (such as frame 2420) from another AP requesting to monitor/receive PPDUs, such as a PPDU (e.g., PPDU 2426) addressed to the other AP from a STA (e.g., STA 2406) associated with the other AP. AP 2402 supporting the inter-AP notification capability may further include AP 2404 having the capability to transmit to the other AP in a PS mode a notification of reception of a first PPDU (such as PPDU 2426 transmitted by STA 2406 to AP 2402). AP 2404 supporting the inter-AP notification capability may further include AP 2204 having the capability to transmit to the other AP a frame (such as frame 2428 described below) comprising a notification of reception of the first PPDU.

[0313] As illustrated in FIG. 24, example 2400 may begin with AP 2402 performing EDOA and transmitting to AP 2404 a request frame 2420 for AP 2404 to monitor/receive PPDUs (e.g. PPDU 2426) addressed to AP 2402. In an embodiment, PPDUs addressed to AP 2402 may comprise PPDUs indicating an address of AP 2402 or an identifier of AP 2402. In an embodiment, request frame 2420 may be for AP 2404 to monitor/receive PPDUs addressed to AP 2402 operating in the first power state/mode.

[0314] In an embodiment, AP 2402 may transmit request frame 2420 during a period 2410 ending by a time T1. In an example, during period 2410, AP 2402 may operate in the other mode. In another example, during period 2410, AP 2402 may operate in the second power state/mode of the PS mode.

[0315] In an embodiment, request frame 2420 may further comprise a first request for AP 2204 to transmit a notification of reception of a first PPDU (e.g. PPDU 2426) to AP 2402. In an embodiment, the first PPDU addressed to AP 2402 may be of the second category that AP 2402 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).

[0316] In an embodiment, request frame 2420 may comprise a management frame. In an example, the management frame may comprise an action frame.

[0317] As shown in FIG. 24, AP 2404 may transmit to AP 2402 a response frame 2422 in response to request frame 2420. In an embodiment, response frame 2422 may indicate an acceptance or a rejection. In an embodiment, response frame 2422 may comprise a management frame. In an example, the management frame may comprise an action frame. [0318] As shown in FIG. 24, AP 2402 may transmit a frame 2424 using EDOA during period 2410. In an embodiment, the AP 2402 may transmit frame 2424 before or after transmitting frame 2420. In an example, frame 2424 may comprise capability information of AP 2402 indicating support by AP 2402 of the PS mode illustrated in FIG. 24. In an embodiment, frame 2424 may indicate that AP 2402 operates in the PS mode during a period 2412. Period 2412 may start at time T1 and end at a time T4. Frame 2424 may comprise a management frame indicating a broadcast address. In an implementation, frame 2424 may comprise a beacon frame. In an embodiment, frame 2424 and the first frame used for capability exchange may be the same frame. In an embodiment, frame 2424 and the first frame may be an aggregated frame. In another embodiment, frame 2420 and frame 2424 may be an aggregated frame.

[0319] In an example, STA 2406 may receive frame 2424 and may determine period 2412 during which AP 2402 is scheduled to operate in the PS mode. In an example, AP 2404 may receive frame 2424.

[0320] In an embodiment, based on transmitting response frame 2422 indicating an acceptance in response to frame 2420 and receiving frame 2424 indicating that AP 2402 operates in the PS mode during period 2412, AP 2404 may start to receive/monitor PPDUs addressed to AP 2402 during period 2412.

[0321] In an example, after AP 2402 begins operating in the PS mode at time T1, STA 2406 may have data arrive for transmission to AP 2402 during a period 2414, e.g., beginning at time T1 and ending at a time T2, of period 2412. In an example, AP 2402 may be operating in the first power state/mode of the PS mode during period 2414.

[0322] In example 2400, STA 2406 may transmit a PPDU 2426 to AP 2402 carrying the data for AP 2402. In an example, PPDU 2426 may be of the second category that AP 2402 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).

[0323] AP 2404 may receive PPDU 2426 addressed to AP 2402. In an embodiment, based on transmitting response frame 2422 indicating an acceptance of the request in response to frame 2420, AP 2404 may be configured to transmit to AP 2402 a notification of reception of PPDU 2426. In another embodiment, based on transmitting response frame 2422 indicating an acceptance of the first request in response to frame 2420, AP 2404 may transmit to AP 2402 the notification of reception of PPDU 2426. In example, 2400, AP 2404 transmits to AP 2402 a frame 2428 comprising the notification of reception of PPDU 2426. In an embodiment, frame 2428 may be carried by a PPDU of the first category that AP 2402 is capable of receiving during the first power state/mode (e.g., a non-HT PPDU, a PPDU having a data rate that is less than or equal to 24 Mbps, a bandwidth of 20 MHz, and/or a single spatial stream). In an embodiment, frame 2428 may indicate a reception of PPDU 2426 of the second category transmitted by STA 2406.

[0324] In an embodiment, frame 2428 may comprise a control frame. In an example, the control frame may comprise a trigger frame. In an example, the trigger frame may comprise a MU-RTS trigger frame. In another example, the control frame may comprise a block ack request (BAR) frame. In another example, the control frame may comprise an initial control frame (IGF). In an embodiment, frame 2428 may comprise a management frame. In an example, the management frame may comprise an action frame. In an embodiment, frame 2428 may comprise a data frame. In an example, the data frame may comprise a QoS null frame.

[0325] In an embodiment, AP 2404 may determine to transmit frame 2428 based on a comparison of a value of a first field of PPDU 2426 to a first threshold.

[0326] In an embodiment, the first field may indicate an transmission characteristic of PPDU 2426 addressed to AP 2402. In an example, the transmission characteristic may comprise a data rate, a modulation and coding scheme (MOS), a length, a bandwidth (BW), or a number of spatial streams (NSS). In an embodiment, the first field may comprise a rate field. In an example, the value of the first field may comprise a value corresponding to a data rate of PPDU 2426. In an example, the value corresponding to the data rate may comprise a value in bits per second. In an embodiment, the first field may comprise an MOS field. In an example, the value of the first field may comprise a value corresponding to an MOS index of PPDU 2426. In an example, the value corresponding to the MOS index may comprise an integral representation of the MOS index. In an embodiment, the first field may comprise a length field. In an example, the value of the first field may comprise a value corresponding to a length of PPDU 2426. In an example, the value corresponding to the length may comprise a value in octet. In an embodiment, the first field may comprise a BW field. In an example, the value of the first field may comprise a value corresponding to a BW of PPDU 2426. In an example, the value corresponding to the BW may comprise a value in Hz. In an embodiment, the first field may comprise a NSS field. In an example, the value of the first field may comprise a value corresponding to a NSS of PPDU 2426. In an example, the value corresponding to the NSS may comprise an integral representation of the NSS.

[0327] In an embodiment, the first threshold may be associated with the first field of the PPDU 2426. In an embodiment, the first request comprised in request frame 2420 may indicate/comprise the first threshold. In another embodiment, frame 2424 may indicate/comprise the first threshold. In an embodiment, the first threshold may comprise a dynamic threshold (e.g., the first threshold may be indicated by AP 2402 before each time that AP 2402 intends to enter the PS mode). In an embodiment, the first threshold may comprise a semi-static threshold (e.g., the first threshold may apply to a pre-determined time duration). In another embodiment (not shown in FIG. 24), the first threshold may comprise a static threshold or pre-configured threshold (e.g., the first threshold may be announced once or may be pre-configured within AP 2404).

[0328] In an example, AP 2404 may compare the value of the first field of PPDU 2426 to the first threshold. Based on the comparison, AP 2404 may or may not transmit frame 2428. For example, assuming that the first field of PPDU 2426 comprises an NSS value and the first threshold indicates an NSS threshold (e.g., 4 spatial streams), AP 2404 may transmit frame 2428 when the NSS value indicated in the first field is lower than the NSS threshold and may not transmit frame 2428 when the NSS value indicated in the first field is higher than the NSS threshold. This allows AP 2402 to remain in the first power state/mode during period 2416, further reducing power consumption of AP 2402.

[0329] In an example, AP 2204 may compare the value of the first field of PPDU 2426 to the first threshold. Based on the comparison, AP 2404 may or may not transmit frame 2428. For example, assuming that the first field of PPDU 2426 comprises an NSS value and the first threshold indicates an NSS threshold (e.g., 4 spatial streams), AP 2404 may transmit frame 2428 when the NSS value indicated in the first field is higher than the NSS threshold and may not transmit frame 2428 when the NSS value indicated in the first field is lower than the NSS threshold. This allows AP 2402 to remain in the first power state/mode during period 2416, further reducing power consumption of AP 2402.

[0330] In an embodiment, AP 2404 may determine to transmit frame 2428 based on the first threshold within a timeout duration starting from AP 2404 receiving the timeout duration. In an embodiment, the first request may further indicate/comprise the timeout duration.

[0331] In an example, where AP 2402 operates in the first power state/mode during period 2414 and where PPDU 2426 is of the second category. AP 2404 may not be capable of receiving PPDU 2426 from STA 2406. However, AP 2402 may receive and process frame 2428. In an embodiment, based on receiving frame 2428, AP 2402 may be configured to transition from the first power state/mode to the second power state/mode. In example 2400, AP 2402 may transition from the first power state/mode to the second power state/mode at a time T2. AP 2302 may operate in the second power state/mode during a period 2416 starting from T2 and ending at a time T3. In an embodiment, AP 2402 may optionally transmit an acknowledgment frame 2430 in response to frame 2428. AP 2402 may transmit acknowledgment frame 2430 before or after transitioning to the second power state/mode.

[0332] As shown in FIG. 24, in an example, after AP 2402 transitions to the second power state/mode, AP 2402 may transmit a frame 2436 soliciting a PPDU 2432 from STA 2406. In an embodiment, frame 2436 may comprise a trigger frame. In an embodiment, PPDU 2432 may be of the second category that AP 2402 is capable of receiving during the second power state/mode. In an embodiment, PPDU 2432 may comprise a retransmission of PPDU 2426. In an embodiment, PPDU 2432 may comprise a trigger-based (TB) PPDU.

[0333] AP 2402 may receive and process PPDU 2432 during period 2416. In an embodiment, AP 2402 may transmit an acknowledgment frame 2434 to STA 2406 in response to PPDU 2432. In an example, frame 2434 may comprise a BA frame. In an embodiment, as shown in FIG. 24, AP 2402 may transition from the second power state/mode to the first power state/mode after transmitting frame 2430 at time T3. AP 2402 may operate in the first power state/mode for at least a period 2418 starting at T3 and ending at a time T4.

[0334] As illustrated by example 2400, by supporting the inter-AP notification capability, AP 2402 is able to operate in the PS mode during period 2412 despite having STA 2406 that does not support the PS mode operation being associated with AP 2402. AP 2402 receives notification of reception in frame 2424 from AP 2304 based on transmitting request frame 2320. AP 2402 transitions from the first power state/mode to the second power state/mode based on receiving frame 2324 from AP 2304. AP 2302 may operate otherwise in the first power state/mode, which allows AP 2202 to reduce its power consumption while operating in the PS mode.

[0335] FIG. 25 illustrates an example 2500 of an inter AP notification procedure 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 includes an AP 2502, an AP 2504, and an STA 2506. In an example, STA 2506 may be associated with AP 2502. AP 2502, AP 2504, and/or STA 2506 may each comprise a multi-link device (MLD).

[0336] In an implementation, APs 2502 and 2504 may belong to the same ESS as described above in FIG. 1. In such a case, APs 2502 and 2504 may be connected by a DS to support ESS features. In an example, APs 2502 and 2504 belong to different BSSs. In an embodiment, AP 2502 may belong to a first BSS and AP 2504 may belong to a second BSS. In an embodiment, the second BSS may comprise an overlapping basic service set (OBSS) relative to the first BSS. [0337] In an embodiment, AP 2502 and 2504 may form a multi-AP group. AP 2502 may be a sharing/master AP of the multi-AP group. AP 2504 may be a shared/slave AP of the multi-AP group. It is assumed in example 2500, APs 2502 and 2504 may complete a multi-AP setup procedure prior to the beginning of example 2500. In addition, as part of a multi-AP group, APs 2502 and 2504 may be connected by a backhaul. In an example, the backhaul may be a wireless backhaul. [0338] In an embodiment, before the beginning of example 2500, AP 2502 and AP 2504 may complete a multi-AP selection phase such as multi-AP selection phase 1010 described in FIG. 10 above.

[0339] It is assumed in example 2500 that AP 2502 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.

[0340] In an implementation, AP 2502 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, AP 2502 is capable of receiving PPDUs of a first category. While in the second power state/mode, AP 2502 is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, AP 2502 is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, AP 2502 is capable of receiving PPDUs of only the first category during the first power state/mode.

[0341] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 1410 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 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, an ultra-high reliability (UHR) PPDU, ora physical layer version identifier field. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 25 Mbps, a bandwidth greater than 20 MHz, and/or a plurality of spatial streams.

[0342] AP 2502 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 the STA, the first power state/mode may correspond to a default state/mode 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.

[0343] Similar to AP 2002 described in FIG. 20, AP 2502 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. AP 2502 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.

[0344] It is further assumed in example 2500 that STA 2506 does not support operating with AP 2502 operating in the PS mode. For example, STA 2506 may not have the capability to solicit AP 2502 to transition from the first power state/mode to the second power state/mode of the PS mode as described above. In an example, STA 2506 may comprise a legacy STA.

[0345] It is assumed in example 2500 that AP 2502 supports an inter-AP notification capability. AP 2502 supporting the inter-AP notification capability may include AP 2502 having the capability to transmit a frame (such as frame 2520 described below) that requests another AP (such as AP 2504) to monitor/receive PPDUs addressed to AP 2502. AP 2502 supporting the inter-AP notification capability may further include AP 2502 having the capability to transmit the frame (such as frame 2520 described below) to request AP 2504 to transmit to AP 2502 in a PS mode a notification of reception by the other AP of a first PPDU (such as PPDU 2526 transmitted by STA 2506 to AP 2502). In an example, the PS mode may comprise a LPL mode. AP 2502 supporting the inter-AP notification capability may further include AP 2502 having the capability to receive from the other AP a frame (such as frame 2528 described below) comprising a notification of reception by the other AP while AP 2502 is in the PS mode.

[0346] It is also assumed in example 2500 that AP 2504 supports the inter-AP notification capability. AP 2504 supporting the inter-AP notification capability may include AP 2504 having the capability to receive and process a frame (such as frame 2520) from another AP requesting to monitor/receive PPDUs, such as a PPDU (e.g., PPDU 2526) addressed to the other AP from a STA (e.g., STA 2406) associated with the other AP. AP 2402 supporting the inter-AP notification capability may further include AP 2404 having the capability to transmit to the other AP in a PS mode a notification of reception of a first PPDU (such as PPDU 2526 transmitted by STA 2506 to AP 2502). AP 2504 supporting the inter-AP notification capability may further include AP 2504 having the capability to transmit to the other AP a frame (such as frame 2528 described below) comprising a notification of reception of the first PPDU.

[0347] As illustrated in FIG. 25, example 2500 may begin with AP 2502 performing EDOA and transmitting to AP 2504 a request frame 2520 for AP 2504 to monitor/receive PPDUs (e.g. PPDU 2526) addressed to AP 2502. In an embodiment, PPDUs addressed to AP 2502 may comprise PPDUs indicating an address of AP 2502 or an identifier of AP 2502. In an embodiment, request frame 2520 may be for AP 2504 to monitor/receive PPDUs addressed to AP 2502 operating in the first power state/mode.

[0348] In an embodiment, AP 2502 may transmit request frame 2520 during a period 2510 ending by a time T1. In an example, during period 2510, AP 2502 may operate in the other mode. In another example, during period 2510, AP 2502 may operate in the second power state/mode of the PS mode.

[0349] In an embodiment, request frame 2520 may further comprise a first request for AP 2204 to transmit a notification of reception of a first PPDU (e.g. PPDU 2526) to AP 2502. In an embodiment, the first PPDU addressed to AP 2502 may be of the second category that AP 2502 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).

[0350] In an embodiment, request frame 2520 may comprise a management frame. In an example, the management frame may comprise an action frame.

[0351] As shown in FIG. 25, AP 2504 may transmit to AP 2502 a response frame 2522 in response to request frame 2520. In an embodiment, response frame 2522 may indicate an acceptance or a rejection. In an embodiment, response frame 2522 may comprise a management frame. In an example, the management frame may comprise an action frame. [0352] As shown in FIG. 25, AP 2502 may transmit a frame 2524 using EDOA during period 2510. In an embodiment, the AP 2502 may transmit frame 2524 before or after transmitting frame 2520. In an example, frame 2524 may comprise capability information of AP 2502 indicating support by AP 2502 of the PS mode illustrated in FIG. 25. In an embodiment, frame 2524 may indicate that AP 2502 operates in the PS mode during a period 2512. Period 2512 may start at time T1 and end at a time T4. Frame 2524 may comprise a management frame indicating a broadcast address. In an implementation, frame 2524 may comprise a beacon frame. In an embodiment, frame 2524 and the first frame used for capability exchange may be the same frame. In an embodiment, frame 2524 and the first frame may be an aggregated frame. In another embodiment, frame 2520 and frame 2524 may be an aggregated frame.

[0353] In an example, STA 2506 may receive frame 2524 and may determine period 2512 during which AP 2502 is scheduled to operate in the PS mode. In an example, AP 2504 may receive frame 2524.

[0354] In an embodiment, based on transmit frame 2522 indicating an acceptance in response to frame 2520 and receiving frame 2524 indicating that AP 2402 operates in the PS mode during period 2412, AP 2504 may start to receive/monitor PPDUs addressed to AP 2502 during period 2512.

[0355] In an example, after AP 2502 begins operating in the PS mode at time T1, STA 2506 may have data arrive for transmission to AP 2502 during a period 2514, e.g., beginning at time T1 and ending at a time T2, of period 2512. In an example, AP 2502 may be operating in the first power state/mode of the PS mode during period 2514.

[0356] In example 2500, STA 2506 may transmit a PPDU 2526 to AP 2502 carrying the data for AP 2502. In an example, PPDU 2526 may be of the second category that AP 2502 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). [0357] AP 2504 may receive PPDU 2526 addressed to AP 2502. In an embodiment, based on transmitting frame 2522 indicating an acceptance of the request in response to frame 2520, AP 2504 may be configured to transmit to AP 2502 a notification of reception of PPDU 2526. In another embodiment, based on transmitting frame 2522 indicating an acceptance of the first request in response to frame 2520, AP 2504 may transmit to AP 2502 the notification of reception of PPDU 2526. In example, 2500, AP 2504 transmits to AP 2502 a frame 2528 comprising the notification of reception of PPDU 2526. In an embodiment, frame 2528 may be carried by a PPDU of the first category that AP 2502 is capable of receiving during the first power state/mode (e.g., a non-HT PPDU, a PPDU having a data rate that is less than or equal to 25 Mbps, a bandwidth of 20 MHz, and/or a single spatial stream). In an embodiment, frame 2528 may indicate a reception of PPDU 2526 of the second category transmitted by STA 2506.

[0358] In an embodiment, frame 2528 may indicate a value of a second field of the PPDU 2526 addressed to AP 2502. In an embodiment, the second field may indicate an transmission characteristic of PPDU 2526. In an example, the transmission characteristic may comprise a data rate, a modulation and coding scheme (MOS), a length, a bandwidth (BW), or a number of spatial streams (NSS). In an embodiment, the second field may comprise a rate field. In an example, the value of the second field may comprise a value corresponding to a data rate of PPDU 2526. In an example, the value corresponding to the data rate may comprise a value in bits per second. In an embodiment, the second field may comprise a MOS field. In an example, the value of the second field may comprise a value corresponding to a MOS index of PPDU 2526. In an example, the value corresponding to the MOS index may comprise an integral representation of the MOS index. In an embodiment, the second field may comprise a length field. In an example, the value of the second field may comprise a value corresponding to a length of PPDU 2526. In an example, the value corresponding to the length may comprise a value in octet. In an embodiment, the second field may comprise a BW field. In an example, the value of the second field may comprise a value corresponding to a BW of PPDU 2526. In an example, the value corresponding to the BW may comprise a value in Hz. In an embodiment, the second field may comprise a NSS field. In an example, the value of the second field may comprise a value corresponding to a NSS of PPDU 2526. In an example, the value corresponding to the NSS may comprise an integral representation of the NSS.

[0359] In an embodiment, frame 2528 may further comprise a second request for AP 2502 to transition from the first power state/mode to the second power state/mode.

[0360] In an embodiment, frame 2528 may comprise a control frame. In an example, the control frame may comprise a trigger frame. In an example, the trigger frame may comprise a MU-RTS trigger frame. In another example, the control frame may comprise a block ack request (BAR) frame. In another example, the control frame may comprise an initial control frame (IGF). In an embodiment, frame 2528 may comprise a management frame. In an example, the management frame may comprise an action frame. In an embodiment, frame 2528 may comprise a data frame. In an example, the data frame may comprise a QoS null frame.

[0361] In an example, where AP 2502 operates in the first power state/mode during period 2514 and where PPDU 2526 is of the second category. AP 2504 may not be capable of receiving PPDU 2526 from STA 2506. However, AP 2502 may receive and process frame 2528. In an embodiment, based on the second request indicated in frame 2528, AP 2502 may transition from the first power state/mode to the second power state/mode. In example 2500, AP 2502 may transition from the first power state/mode to the second power state/mode at a time T2. In an embodiment, the transitioning may be based on a comparison of the value of the second field to a second threshold. In an embodiment, the second threshold may be associated with the second field of PPDU 2526. AP 2502 may operate in the second power state/mode during a period 2516 beginning from time T2 and ending at a time T3.

[0362] In an example, AP 2504 may compare the value of the second field of PPDU 2526 to the second threshold. Based on the comparison, AP 2504 may or may not transition from the first power state/mode to the second power state/mode. For example, assuming that the second field of PPDU 2526 comprises an NSS value and the second threshold indicates an NSS threshold (e.g., 4 spatial streams), AP 2504 may transition from the first power state/mode to the second power state/mode when the NSS value indicated in the second field is lower than the NSS threshold and may not transition from the first power state/mode to the second power state/mode when the NSS value indicated in the second field is higher than the NSS threshold. This allows AP 2302 to remain in the first power state/mode during period 2316, further reducing power consumption of AP 2302.

[0363] In an example, AP 2504 may compare the value of the second field of PPDU to the second threshold. Based on the comparison, AP 2504 may or may not transition from the first power state/mode to the second power state/mode. For example, the second threshold may be set to 2 corresponding to the fifth value of NSS of the first PPDU. For example, the fifth value of NSS of PPDU 2526 may be set to 3. For example, assuming that the second field of PPDU 2526 comprises an NSS value and the second threshold indicates an NSS threshold (e.g., 4 spatial streams), AP 2504 may transition from the first power state/mode to the second power state/mode when the NSS value indicated in the second field is higher than the NSS threshold and may not transition from the first power state/mode to the second power state/mode when the NSS value indicated in the second field is lower than the NSS threshold. This allows AP 2302 to remain in the first power state/mode during period 2316, further reducing power consumption of AP 2302.

[0364] In an embodiment, after AP 2502 transitions to the second power state/mode, AP 2502 may transmit a second response 2530 in response to the second request during period 2516. In an embodiment, second response 2530 may indicate an acceptance of the second request as shown in FIG. 25. In another embodiment, second response 2530 may indicate a rejection of the second request (not shown in FIG. 25). In an embodiment, second response 2530 may further comprise a solicitation of a following PPDU (e.g. PPDU 2532) from STA 2506. In an embodiment, second response 2530 may aggregate the solicitation. In an embodiment, second response 2530 may comprise a management frame. In an example, the management frame may comprise an action frame. In an embodiment, the solicitation may comprise a control frame. In an example, the control frame may comprise a trigger frame.

[0365] After transmitting second response 2530, AP 2502 may receive a PPDU 2532 from STA 2506. In an embodiment, PPDU 2532 may be of the second category that AP 2502 is capable of receiving during the second power state/mode. In an embodiment, PPDU 2532 may comprise a retransmission of PPDU 2526. In an embodiment, PPDU 2532 may comprise a trigger-based (TB) PPDU. [0366] AP 2502 may receive and process PPDU 2532 during period 2516. In an embodiment, AP 2502 may transmit an acknowledgment frame 2534 to STA 2506 in response to PPDU 2532. In an example, frame 2534 may comprise a BA frame. In an embodiment, as shown in FIG. 25, AP 2502 may transition from the second power state/mode to the first power state/mode after transmitting second response 2530 at time T3. AP 2502 may operate in the first power state/mode for at least a period 2518 starting at T3 and ending at a time T4.

[0367] As illustrated by example 2500, by supporting the inter-AP notification capability, AP 2502 is able to operate in the PS mode during period 2512 despite having STA 2506 that does not support the PS mode operation being associated with AP 2502. AP 2502 receives notification of reception in frame 2524 from AP 2304 based on transmitting request frame 2320. AP 2502 transitions from the first power state/mode to the second power state/mode based on receiving frame 2324 from AP 2304. AP 2302 may operate otherwise in the first power state/mode, which allows AP 2202 to reduce its power consumption while operating in the PS mode.

[0368] In an embodiment, frame 2220 described in FIG. 22, frame 2320 described in FIG. 23, frame 2420 described in FIG. 24, and frame 2520 described in FIG. 25, may comprise a management frame. In an example, the management frame may comprise an action frame.

[0369] FIG. 26 illustrates an example action field 2600 of an action frame (as shown in FIG. 4) which may be used according to example embodiments. For example, the action frame comprising action field 2600 may be an embodiment of frames 2220, 2320, 2420, and 2520. In an example, the action frame may comprise a public action frame.

[0370] In an embodiment, action field 2600 may be used by a first AP to request that a second AP to monitor/receive PPDUs addressed to the first AP. In an embodiment, action field 2600 may be used by the first AP to request that the second AP transmit a notification of reception of a first PPDU addressed to the first AP.

[0371] In an embodiment, the first AP implements the PS mode illustrated in FIGs. 22-25. In an implementation, the first AP 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. While in the first power state/mode, the first AP is capable of receiving PPDUs of a first category. While in the second power state/mode, the first AP is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, the first AP is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, the first AP is capable of receiving PPDUs of only the first category during the first power state/mode.

[0372] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 1410 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 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, an ultra-high reliability (UHR) PPDU, ora physical layer version identifier field. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 25 Mbps, a bandwidth greater than 20 MHz, and/or a plurality of spatial streams.

[0373] In an embodiment, PPDUs addressed to the first AP may be of the first category and/or the second category. In an embodiment, the first PPDU may be of the second category.

[0374] In an embodiment, the action frame using action field 2600 may comprise a request frame. In an example, the action frame using action field 2600 may comprise an inter-AP notification request frame. In an embodiment, the action frame using action field 2600 may be an unsolicited frame, such as frame 2220 described in FIG. 22, frame 2320 described in FIG. 23, frame 2420 described in FIG. 24, and frame 2520 described in FIG. 25.

[0375] For example, the first AP may be an embodiment of AP 2202 described in FIG. 22, AP 2302 described in FIG. 23, AP 2402 described in FIG. 24, and AP 2502 described in FIG. 25. The second AP may be an embodiment of AP 2204 described in FIG. 22, AP 2304 described in FIG. 23, AP 2404 described in FIG. 24, and AP 2504 described in FIG. 25.

[0376] In an embodiment, action field 2600 may comprise information supporting inter-AP notification. In an embodiment, the information supporting inter-AP notification may include a request by the first AP that the second AP to monitor/receive PPDUs addressed to the first AP. In an embodiment, the request may include a first request by the first AP that the second AP to transmit a notification of reception of a first PPDU addressed to the first AP. In an embodiment, action field 2600 may indicate the request from the second AP. In an embodiment, action field 2600 may be an inter-AP notification request action field.

[0377] In an embodiment, action field 2600 may include a category subfield 2602 that indicates that the action frame using action field 2600 is for inter-AP notification.

[0378] In an embodiment, action field 2600 may include an action details field 2604.

[0379] In an embodiment, action details field 2604 may comprise a PPDU category subfield 2606, a STA ID subfield 2608, an optional threshold mode subfield 2610, an optional threshold type subfield 2612, an optional threshold value subfield 2614, and an optional threshold timeout duration subfield 2616.

[0380] In an embodiment, PPDU category subfield 2606 may indicate a category of PPDUs for which inter-AP notification is requested by the first AP. In an embodiment, PPDU category subfield 2606 may indicate a second category including 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, 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.

[0381] In an embodiment, STA ID subfield 2608 may indicate one or more identifiers of STAs. In an embodiment, the identifiers of STAs may comprise association identifiers (AID) of STAs. In an example, the STAs may be associated with the first AP. [0382] In an embodiment, threshold mode subfield 2610 may indicate a comparison mode using a first threshold. In example, the comparison mode may comprise a first mode that allow the first AP to reduce power consumption when receiving a second PPDU (e.g., PPDU 2232, 2234, 2432). In an example, subfield 2610 may be set to 0 for the first mode to allow the second AP to compare values of a first field of the first PPDU equal or lower than the first threshold indicated in subfields 2612 and 2614. In example, the comparison mode may comprise a second mode that allow the first AP to increase throughput when receiving the second PPDU. In an example, subfield 2610 may be set to 1 for the second mode to allow the second AP to compare values of a first field of the first PPDU higher than the first threshold indicated in subfields 2612 and 2614.

[0383] In an embodiment, threshold type subfield 2612 may indicate a type of the first threshold associated with the first field of the first PPDU. In example, threshold type subfield 2612 may comprise a data rate type, a MOS type, a length type, or a BW type, or a NSS type.

[0384] In an embodiment, threshold value subfield 2614 may indicate a value of the threshold corresponding to subfield 2612. In example, the value of the threshold may comprise a data rate, e.g., in bits per second, a MOS index, e.g., in integral representation, a length, e.g., in octets, or a BW, in Hz, or a NSS, in integral representation.

[0385] In an embodiment, threshold timeout duration subfield 2616 may indicate a timeout duration, e.g., in seconds, for applying the threshold by the second AP.

[0386] In an embodiment, frame 2224 described in FIG. 22, frame 2328 described in FIG. 23, frame 2428 described in FIG. 24, and frame 2528 described in FIG. 25, may comprise a control frame. In an example, the control frame may comprise a trigger frame.

[0387] FIG. 27 illustrates an example user info field 2700 of a trigger frame which may be used according to embodiments. For example, trigger frame comprising user info field 2700 may be an embodiment of frames 2224, 2328, 2428, and 2528. In an example, the trigger frame may comprise a MU-RTS frame. In an example, the trigger frame may comprise an inter-AP notification frame.

[0388] In an embodiment, user info field 2700 may be used by a first AP to receive from a second AP a notification of reception of a first PPDU addressed to the first AP. In an embodiment, user info field 2700 may be used by the second AP requesting the first AP to transition from a first power state/mode to a second power state/mode of the PS mode illustrated in FIG. 22-25.

[0389] In an embodiment, the first AP implements the power save (PS) mode illustrated in FIG. 22-25, which may be denoted as a dynamic PS mode or a low power listening (LPL) mode. In an implementation, the first AP 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, the first AP is capable of receiving PPDUs of a first category. While in the second power state/mode, the first AP is capable of receiving PPDUs of the first category and PPDUs of a second category. In an implementation, the first AP is not capable of receiving PPDUs of the second category during the first power state/mode. In an implementation, the first AP is capable of receiving PPDUs of only the first category during the first power state/mode.

[0390] In an implementation, the first category may include PPDUs having a non-HT PPDU format such as non-HT PPDU 1410 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 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, an ultra-high reliability (UHR) PPDU, ora physical layer version identifier field. Additionally, or alternatively, the second category may include PPDUs having a data rate that is greater than 25 Mbps, a bandwidth greater than 20 MHz, and/or a plurality of spatial streams.

[0391] In an embodiment, the first PPDU addressed to the first AP may be of the second category.

[0392] In an embodiment, the trigger frame using user info field 2700 may comprise a notification frame. In an example, the notification frame may comprise an inter-AP notification frame. In an embodiment, the trigger frame using user info field 2700 may comprise a request frame. In an embodiment, the request frame may comprise a power state/mode transition request frame. In an embodiment, the trigger frame using user info field 2700 may be an unsolicited frame, such as frame 2224 described in FIG. 22, frame 2328 described in FIG. 23, frame 2428 described in FIG. 24, and frame 2528 described in FIG. 25.

[0393] For example, the first AP may be an embodiment of AP 2202 described in FIG. 22, AP 2302 described in FIG. 23, AP 2402 described in FIG. 24, and AP 2502 described in FIG. 25. The second AP may be an embodiment of AP 2204 described in FIG. 22, AP 2304 described in FIG. 23, AP 2404 described in FIG. 24, and AP 2504 described in FIG. 25.

[0394] In an embodiment, user info field 2700 may comprise information supporting inter-AP notification. In an embodiment, the information supporting inter-AP notification may include a notification to a first AP that a second AP receiving a first PPDU addressed to the first AP. In an embodiment, the information supporting inter-AP notification may include a request by a second AP for a first AP to transition from a first power state/mode to a second power state/mode. In an embodiment, user info field 2700 may indicate a request from the second AP. In an embodiment, user info field 2700 may be an inter-AP notification field.

[0395] In an embodiment, user info field 2700 may comprise an AP ID subfield 2702, a transition request flag subfield 2704, a PPDU category subfield 2706, a PPDU SIG info subfield 2708, a PPDU SIG value subfield 2710, and an optional STA ID subfield 2712.

[0396] In an embodiment, AP ID subfield 2702 may indicate an identifier of the first AP.

[0397] In an embodiment, transition request flag subfield 2704 may comprise a flag that indicates whether the second AP requests that the first AP transition from the first power state/mode to the second power state/mode. For example, the flag set to 1 may indicate that the second AP requests that the first AP transition from the first power state/mode to the second power. [0398] In an embodiment, PPDU category subfield 2706 may indicate a category of PPDUs for which inter-AP notification is requested by the first AP. In an embodiment, PPDU category subfield 2706 may indicate a second category including 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 1420, a VHT format such as VHT PPDU 1430, an HE PPDU such as HE SU PPDU 1510, HE MU PPDU 1520, or HE ER SU PPDU 1530, an EHT PPDU such as EHT MU PPDU 1600, 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.

[0399] In an embodiment, PPDU SIG info subfield 2708 may indicate a second field of the first PPDU. In an embodiment, the second field may comprise a rate field, a modulation and coding scheme (MOS) field, a length field, a bandwidth (BW) field, and/or a number of spatial streams (NSS) field. In an embodiment, PPDU SIG info subfield 2708 may be associated with signaling or operation information associated with the first PPDU. In an example, the operation information may comprise a data rate, a MOS, a length, a BW, or a NSS.

[0400] In an embodiment, PPDU SIG value subfield 2710 may indicate a value of the second field (as indicated in PPDU SIG info subfield 2708) of the first PPDU. In an example, the value of the second field may comprise a first value corresponding to a data rate of first PPDU. In an example, the first value may comprise the first value in bits per second. In an example, the value of the second field may comprise a second value corresponding to a MOS index of first PPDU. In an example, the second value may comprise an integral representation of the MOS index. In an example, the value of the second field may comprise a third value corresponding to a length of PPDU. In an example, the third value may comprise the third value in octet. In an example, the value of the second field may comprise a fourth value corresponding to a BW of PPDU. In an example, the fourth value may comprise the fourth value in Hz. In an example, the value of the second field may comprise a fifth value corresponding to a NSS of PPDU. In an example, the fifth value may comprise an integral representation of the NSS.

[0401] In an embodiment, STA ID subfield 2712 may indicate one or more identifiers of STAs. In an embodiment, the identifiers of STAs may comprise association identifiers (AID) of STAs. In an example, the STAs may be associated with the first AP.

[0402] 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.

[0403] 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.

[0404] 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 an MLD, comprising at least one affiliated AP or affiliated STA.

[0405] 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 AP such as AP 2202, AP 2302, AP 2402, or AP 2502, for example. Process 2800 may be performed while the first AP is in a power save mode as illustrated in FIGs. 22-25, for example. As shown in FIG. 28, process 2800 may include step 2802, which includes receiving, by the first AP from a second AP, a notification of reception by the second AP of a first PPDU transmitted by a STA to the first AP. For example, the second AP may be an AP such as 2204, AP 2304, AP 2404, or AP 2504.

[0406] In an embodiment, the first AP is capable of transitioning between a first power state/mode and a second power state/mode of the power save mode. In an embodiment, the first power state/mode comprises a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode of the power save mode. In an embodiment, the second power state/mode comprises a higher capability state/mode, a higher power receive state/mode or an awake state/mode of the power save mode. In an embodiment, process 2800 may further comprise transitioning, by the first AP, from the first power state/mode to the second power state/mode based on receiving the notification of reception.

[0407] In an embodiment, process 2800 further comprises before receiving the notification of reception, transmitting, by the first AP to the second AP, a request for the second AP to monitor/receive PPDUs addressed to the first AP.

[0408] In an embodiment, process 2800 further comprises receiving, by the first AP from the second AP, a first response to the request. In an embodiment, the request further comprises a first request for the second AP to transmit the notification of reception to the first AP.

[0409] In an embodiment, process 2800 further comprises transmitting, by the first AP to the second AP, a first frame indicating/comprising a first threshold associated with a first field of the first PPDU. In an embodiment, the first frame and the request are the same frame and the first request indicates/comprise the first threshold. In an implementation, the first threshold comprises a dynamic threshold. In an embodiment, the first frame and the request are separate frames, and the first threshold comprises a semi-static or pre-configured threshold.

[0410] In an embodiment, receiving the notification of reception is based on a comparison of a first value of the first field to the first threshold.

[0411] In an embodiment, the request comprises a management frame. In an embodiment, the management frame comprises an action frame comprising an action field, and wherein the request is provided in the action field.

[0412] In an embodiment, the notification of reception indicates a second value of a second field of the first PPDU addressed to the first AP.

[0413] In an embodiment, process 2800 further comprises comparing, by the first AP, the second value of the second field to a second threshold, and the transitioning is based on the comparing. In an embodiment, the second value of the second field is greater than the second threshold. In another embodiment, the second value of the second field is less than the second threshold.

[0414] In an embodiment, the second field indicates a transmission characteristic. In an embodiment, the second field comprises: a rate field, a modulation and coding scheme (MOS) field, a length field, a bandwidth (BW) field, or a number of spatial streams (NSS) field. In an embodiment, the second field comprises the rate field, and the second value of the second field corresponds to a data rate of the first PPDU. In an embodiment, the second value corresponding to the data rate comprises a value in bits per second. In an embodiment, the second field corresponds to the MOS field, and the second value corresponds to a MOS index of the first PPDU. In an embodiment, the second value corresponding to the MOS index may comprise an integral representation of the MOS index. In an embodiment, the second field corresponds to the length field, and the second value of the second field corresponds to a length of the first PPDU. In an embodiment, the second value corresponding to the length comprises a value in octet. In an embodiment, the second field corresponds to the BW field, and the second value of the second field corresponds to a BW of the first PPDU. In an embodiment, the second value corresponding to the BW comprises a value in Hz. In an embodiment, the second field corresponds to the NSS field, and the second value of the second field corresponds to a NSS of the first PPDU. In an embodiment, the second value corresponding to the NSS may comprise an integral representation of the NSS.

[0415] In an embodiment, the notification of reception comprises a padding field.

[0416] In an embodiment, process 2800 further comprises transmitting, by the first AP to the second AP, an acknowledgment in response to the notification of reception.

[0417] In an embodiment, the notification of reception comprises a second request by the second AP for the first AP to transition from the first power state/mode to the second power state/mode.

[0418] In an embodiment, process 2800 further comprises transmitting, by the first AP to the second AP, a second response to the second request.

[0419] In an embodiment, process 2800 further comprises receiving, by the first AP, a second PPDU addressed to the first AP.

[0420] In an embodiment, the second PPDU comprises an unsolicited frame.

[0421] In an embodiment, the second PPDU is received from the STA. In an embodiment, the second PPDU comprises a retransmission of the first PPDU.

[0422] In an embodiment, process 2800 further comprises transmitting, by the first AP, to the STA, a second frame soliciting the second PPDU from the STA. In an embodiment, the second frame aggregates the second response.

[0423] In another embodiment, the STA comprises a first STA, and wherein the second PPDU is received from a second STA.

[0424] In an embodiment, process 2800 further comprises transitioning, by the first AP, to the first power state/mode. In an embodiment, the transitioning is before receiving the notification of reception. In an embodiment, the transitioning is from the second power state/mode. In another embodiment, the transitioning is from another mode of operation, and the other mode of operation is different from the power save mode.

[0425] In an embodiment, during the first power state/mode, the first AP is capable of receiving PPDUs of a first category. In an embodiment, during the second power state/mode, the first AP is capable of receiving PPDUs of the first category and of a second category. In an embodiment, during the first power state/mode, the first AP is not capable of receiving PPDUs of the second category.

[0426] In an embodiment, the first category comprises a PPDU having a non-high throughput (non-HT) format. In an embodiment, the first category comprises a PPDU having a data rate that is less than or equal to 24 Mbps. In an embodiment, the first category comprises a PPDU having a bandwidth of 20 MHz. In an embodiment, the first category comprises a PPDU having a single spatial stream. In an embodiment, the notice of reception is carried in a PPDU of the first category.

[0427] In an embodiment, the second category comprises a PPDU having: a high throughput (HT) format, a very high throughput (VHT) format, a high efficiency (HE) format, an extremely high throughput (EHT) format, an ultra-high reliability (UHR) format, or a physical layer version identifier field. In an embodiment, the second category comprises a PPDU having a data rate that is greater than 24 Mbps. In an embodiment, the second category comprises a PPDU having a bandwidth greater than 20 MHz. In an embodiment, the second category comprises a PPDU having a plurality of spatial streams. In an embodiment, the first PPDU is carried in a PPDU of the second category. In an embodiment, the second PPDU is carried in a PPDU of the second category.

[0428] In an embodiment, during the other mode of operation, the first AP is capable of receiving a PPDU of the second category in any power state/mode.

[0429] In an embodiment, the notification of reception comprises a control frame. In an embodiment, the control frame comprises a trigger frame. In an embodiment, the trigger frame comprises a multi-user request to send (MU-RTS) frame. In an embodiment, the trigger frame comprises a common info field or a user info field, and wherein the notification of reception is provided in the common info field or the user info field. In an embodiment, the control frame comprises a block ack request (BAR) frame. In an embodiment, the control frame comprise a BAR information field, and wherein the notification of reception is provided in the BAR information field.

[0430] In an embodiment, the notification of reception comprises a management frame. In an embodiment, the management frame comprises an action frame comprising an action field, and wherein the notification of reception is provided in the action field.

[0431] In an embodiment, the power save mode comprises a low-power listening mode or a dynamic power save mode. [0432] In an embodiment, process 2800 further comprises transmitting, by the first AP to the second AP, a first indication of support by the first AP of the inter-AP notification capability; and receiving, by the first AP from the second AP, a second indication of support by the second AP of an inter-AP notification capability.

[0433] In an embodiment, the first AP and the second AP form a multi-AP group. In an embodiment, the first AP belongs to a basic service set (BSS) and the second AP belongs to an overlapping basic service set (OBSS) relative to the BSS. [0434] FIG. 29 illustrates an example process 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 second AP such as AP 2204, AP 2304, AP 2404, or AP 2504, for example. As shown in FIG. 29, process 2900 may include step 2902, which includes, based on receiving a first physical layer protocol data unit (PPDU) transmitted by a station (STA) to a first access point (AP), transmitting, by the second AP to the first AP, a notification of reception of the first PPDU. For example, the first AP may be an AP such as 2202, AP 2302, AP 2402, or AP 2502. In an embodiment, the first AP may be operating in a power save mode when the second AP transmits the notification of reception. The power save mode may be a power save mode as illustrated in FIGs. 22-25 herein. [0435] In an embodiment, process 2900 further comprises receiving, by the second AP, a first PPDU addressed to the first AP.

[0436] In an embodiment, process 2900 further comprises before receiving the first PPDU, receiving, by the second AP from the first AP, a request for the second AP to monitor/receive PPDUs addressed to the first AP.

[0437] In an embodiment, process 2900 further comprises transmitting, by the second AP to the first AP, a first response to the request.

[0438] In an embodiment, the request further comprises a first request for the second AP to transmit the notification of reception to the first AP.

[0439] In an embodiment, process 2900 further comprises receiving, by the second AP to the first AP, a first frame indicating/comprising a first threshold associated with a first field of the first PPDU. In an embodiment, first frame and the request are the same frame, the first request indicates/comprise the first threshold, and the first threshold comprises a dynamic threshold. In another embodiment, the first frame and the request are separate frames, and the first threshold comprises a semi-static or pre-configured threshold.

[0440] In an embodiment, process 2900 further comprises comparing, by the second AP, a first value of the first field to the first threshold, the transmitting the notification of reception is based on the comparing. In an embodiment, the first value of the first field is greater than the first threshold. In another embodiment, the first value of the first field is less than the first threshold.

[0441] In an embodiment, the first field indicates a transmission characteristic. In an embodiment, the first field comprises: a rate field, a modulation and coding scheme (MOS) field, a length field, a bandwidth (BW) field, or a number of spatial streams (NSS) field. In an embodiment, the first field comprises the rate field, and the first value of the first field corresponds to a data rate of the first PPDU. In an embodiment, the first value corresponding to the data rate comprises a value in bits per first. In an embodiment, the first field corresponds to the MOS field, and the first value corresponds to a MOS index of the first PPDU. In an embodiment, first value corresponding to the MOS index may comprise an integral representation of the MOS index. In an embodiment, the first field corresponds to the length field, and the first value of the first field corresponds to a length of the first PPDU. In an embodiment, the first value corresponding to the length comprises a value in octet. In an embodiment, the first field corresponds to the BW field, and the first value of the first field corresponds to a BW of the first PPDU. In an embodiment, the first value corresponding to the BW comprises a value in Hz. In an embodiment, the first field corresponds to the NSS field, and the first value of the first field corresponds to a NSS of the first PPDU. In an embodiment, the first value corresponding to the NSS may comprise an integral representation of the NSS.

[0442] In an embodiment, the request comprises a management frame. In an embodiment, the management frame comprises an action frame comprising an action field, and the request is provided in the action field.

[0443] In an embodiment, the notification of reception indicates a second value of a second field of the first PPDU addressed to the first AP.

[0444] In an embodiment, the notification of reception comprises a padding field. [0445] In an embodiment, process 2900 further comprises receiving, by the second AP from the first AP, an acknowledgment in response to the notification of reception.

[0446] In an embodiment, the notification of reception comprises a second request by the second AP for the first AP to transition from a first power state/mode to a second power state/mode of the power save mode.

[0447] In an embodiment, process 2900 further comprises receiving, by the second AP from the first AP, a second response to the second request.

[0448] In an embodiment, the first power state/mode comprises a lower capability state/mode, a lower power receive state/mode or a listen/listening state/mode of the power save mode. In an embodiment, the second power state/mode comprises a higher capability state/mode, a higher power receive state/mode or an awake state/mode of the power save mode. In an embodiment, during the first power state/mode, the first AP is capable of receiving PPDUs of a first category. In an embodiment, during the second power state/mode, the first AP is capable of receiving PPDUs of the first category and of a second category. In an embodiment, during the first power state/mode, the first AP is not capable of receiving PPDUs of the second category.

[0449] In an embodiment, the first category comprises a PPDU having a non-high throughput (non-HT) format. In an embodiment, the first category comprises a PPDU having a data rate that is less than or equal to 24 Mbps. In an embodiment, the first category comprises a PPDU having a bandwidth of 20 MHz. In an embodiment, the first category comprises a PPDU having a single spatial stream. In an embodiment, the notice of reception is carried in a PPDU of the first category.

[0450] In an embodiment, the second category comprises a PPDU having: a high throughput (HT) format, a very high throughput (VHT) format, a high efficiency (HE) format, an extremely high throughput (EHT) format, an ultra-high reliability (UHR) format, or a physical layer version identifier field. In an embodiment, the second category comprises a PPDU having a data rate that is greater than 24 Mbps. In an embodiment, the second category comprises a PPDU having a bandwidth greater than 20 MHz. In an embodiment, the second category comprises a PPDU having a plurality of spatial streams. In an embodiment, the first PPDU is carried in a PPDU of the second category.

[0451] In an embodiment, during the other mode of operation, the first AP is capable of receiving a PPDU of the second category in any power state/mode.

[0452] In an embodiment, the notification of reception comprises a control frame. In an embodiment, the control frame comprises a trigger frame. In an embodiment, the trigger frame comprises a multi-user request to send (MU-RTS) frame. In an embodiment, the trigger frame comprises a common info field or a user info field, and the notification of reception is provided in the common info field or the user info field. In an embodiment, the control frame comprises a block ack request (BAR) frame. In an embodiment, the control frame comprise a BAR information field, and the notification of reception is provided in the BAR information field. In an embodiment, the notification of reception comprises a management frame. In an embodiment, the management frame comprises an action frame comprising an action field, and the notification of reception is provided in the action field.

[0453] In an embodiment, the power save mode comprises a low-power listening mode or a dynamic power save mode. [0454] In an embodiment, process 2900 further comprises receiving, by the second AP from the first AP, a first indication of support by the first AP of an inter-AP notification capability; and transmitting, by the second AP to the first AP, a second indication of support by the second AP of the inter-AP notification capability.

[0455] In an embodiment, the first AP and the second AP form a multi-AP group. In an embodiment, the first AP belongs to a basic service set (BSS) and the second AP belongs to an overlapping basic service set (OBSS) relative to the BSS. [0456] As would be understood by a person of skill in the art based on the teachings herein, embodiments of the present disclosure are not limited to AP-to-AP communication. Instead, embodiments may be extended to AP STA to non-AP STA, non-AP STA to AP STA, and non-AP STA to non-AP STA communication.

[0457] FIG. 30 illustrates an example process according to an embodiment of the present disclosure. Example process 3000 is provided for the purpose of illustration only and is not limiting of embodiments. Example process 3000 may be performed by a first STA station, which may comprise an AP STA or a non-AP STA. As shown in FIG. 30, process 3000 may include step 3002, which includes receiving, by the first STA, from a second STA, a notification of reception by the second STA of a first PPDU transmitted by a third STA to the first STA. The first STA may be operating in a power save mode at the time of receiving the notification of reception. The power save mode may be a power save mode as illustrated in FIGs. 22-25 above. In an embodiment, the second STA may comprise an AP STA or a non-AP STA. In an embodiment, third STA comprises an AP STA or a non-AP STA.

[0458] In an embodiment, process 3000 further comprises transitioning, by the first STA, from a first power state/mode to a second power state/mode of the power save mode. In an embodiment, the transitioning to the second power state/mode is based on the notification of reception.

[0459] In an embodiment, process 3000 further comprises, before receiving the notification of reception, transmitting, by the first AP to the second AP, a request for the second STA to monitor/receive PPDUs addressed to the first STA.

[0460] In an embodiment, the request further comprises a first request for the second STA to transmit the notification of reception to the first STA.

[0461] In an embodiment, the notification of reception indicates a value of a field of the first PPDU addressed to the first STA.

[0462] In an embodiment, process 2800 further comprises comparing, by the first AP, the value of the field to a threshold, and the transitioning is based on the comparing. In an embodiment, the value of the field is greater than the threshold. In another embodiment, the value of the field is less than the threshold.

[0463] In an embodiment, the field indicates a transmission characteristic. In an embodiment, the second field comprises: a rate field, a modulation and coding scheme (MOS) field, a length field, a bandwidth (BW) field, or a number of spatial streams (NSS) field. In an embodiment, the field comprises the rate field, and the value of the field corresponds to a data rate of the first PPDU. In an embodiment, the value corresponding to the data rate comprises a value in bits per second. In an embodiment, the field corresponds to the MOS field, and the value corresponds to a MOS index of the first PPDU. In an embodiment, the value corresponding to the MOS index may comprise an integral representation of the MOS index. In an embodiment, the field corresponds to the length field, and the value of the field corresponds to a length of the first PPDU. In an embodiment, the value corresponding to the length comprises a value in octet. In an embodiment, the field corresponds to the BW field, and the value of the second field corresponds to a BW of the first PPDU. In an embodiment, the value corresponding to the BW comprises a value in Hz. In an embodiment, the field corresponds to the NSS field, and the value of the field corresponds to a NSS of the first PPDU. In an embodiment, the value corresponding to the NSS may an integral representation of the NSS.

[0464] In an embodiment, the notification of reception comprises a second request by the second STA for the first STA to transition from the first power state/mode to the second power state/mode.

[0465] In an embodiment, process 3000 further comprises receiving, by the first STA, a second PPDU addressed to the first STA.

Claims

CLAIMS What is claimed is:

1. A method comprising: transmitting, by a first access point (AP) to a second AP, a request for the second AP to monitor physical layer protocol data units (PPDUs) addressed to the first AP; transitioning, by the first AP, to a first mode of a power save mode; receiving, by the first AP from the second AP, a notification of reception by the second AP of a first PPDU addressed to the first AP; based on the notification, transitioning by the first AP from the first mode to a second mode of the power save mode; and receiving, by the first AP, a second PPDU addressed to the first AP.

2. A method comprising: receiving, by a first access point (AP) from a second AP, a notification of reception by the second AP of a first physical layer protocol data unit (PPDU) transmitted by a station (STA) to the first AP.

3. The method of claim 2, wherein the first AP is capable of transitioning between a first mode and a second mode of a power save mode.

4. The method of claim 3, wherein the first mode comprises a lower capability mode of the power save mode.

5. The method of any of claims 3-4, wherein the second mode comprises a higher capability mode of the power save mode.

6. The method of claims 3-5, further comprising: transitioning, by the first AP, from the first mode to the second mode of the power save mode.

7. The method of any of claim 6, wherein the transitioning to the second mode is based on receiving the notification of reception.

8. The method of any of claims 2-7, further comprising: before receiving the notification of reception, transmitting, by the first AP to the second AP, a request for the second AP to monitor PPDUs addressed to the first AP.

9. The method of any of claim 8, wherein the request further comprises a first request for the second AP to transmit the notification of reception to the first AP.

10. The method of claim 9, further comprising: transmitting, by the first AP to the second AP, a first frame indicating a first threshold associated with a first field of the first PPDU.

11. The method of claim 10, wherein receiving the notification of reception is based on a comparison of a first value of the first field to the first threshold.

12. The method of claim 6, wherein the notification of reception indicates a second value of a second field of the first PPDU addressed to the first AP.

13. The method of claim 12, further comprising: comparing, by the first AP, the second value of the second field to a second threshold, and wherein the transitioning is based on the comparing.

14. The method of any of claims 12-13, wherein the second field indicates a transmission characteristic.

15. The method of any of claims 12-14, wherein the second field comprises: a rate field, a modulation and coding scheme (MOS) field, a length field, a bandwidth (BW) field, or a number of spatial streams (NSS) field.

16. The method of any of claims 3-15, wherein the notification of reception comprises a second request by the second AP for the first AP to transition from the first mode to the second mode.

17. The method of any of claims 3-16, further comprising: transitioning, by the first AP, to the first mode.

18. The method of claim 17, wherein the transitioning is before receiving the notification of reception.

19. The method of any of claims 17-18, wherein the transitioning is from the second mode.

20. The method of any of claims 17-18, wherein the transitioning is from another mode of operation, wherein the other mode of operation is different from the power save mode.

21. The method of any of claims 3-20, wherein, during the first mode, the first AP is capable of receiving PPDUs of a first category.

22. The method of claim 21, wherein, during the second mode, the first AP is capable of receiving PPDUs of the first category and of a second category.

23. The method of claim 22, wherein, during the first mode, the first AP is not capable of receiving PPDUs of the second category.

24. The method of any of claims 22-23, wherein the first PPDU is carried in a PPDU of the second category.

25. The method of any of claims 22-24, wherein the second PPDU is carried in a PPDU of the second category.

26. The method of any of claims 2-25, wherein the notification of reception comprises a control frame.

27. The method of claim 26, wherein the control frame comprises a trigger frame, a multi-user request to send (MU-

RTS) frame, or a block ack request (BAR) frame.

28. The method of claim 2-27, wherein the notification of reception comprises a padding field.

29. The method of any of claims 2-28, wherein the first AP belongs to a basic service set (BSS) and the second AP belongs to an overlapping basic service set (OBSS) relative to the BSS.

30. A method comprising: receiving, by a first access point (AP) from a second AP, a request for the first AP to monitor physical layer protocol data units (PPDUs) addressed to the second AP; receiving, by the first AP, a first PPDU addressed to the second AP; and based on the first PPDU, transmitting, by the first AP to the second AP, a notification of reception by the first AP of the first PPDU.

31. A method comprising: based on receiving a first physical layer protocol data unit (PPDU) transmitted by a station (STA) to a first access point (AP), transmitting, by a second AP to the first AP, a notification of reception of the first PPDU.

32. The method of claim 31 , further comprising: receiving, by the second AP, a first PPDU addressed to the first AP.

33. The method of any of claims 31-32, further comprising: before receiving the first PPDU, receiving, by the second AP from the first AP, a request for the second AP to monitor PPDUs addressed to the first AP.

34. The method of claim 33, wherein the request further comprises a first request for the second AP to transmit the notification of reception to the first AP.

35. The method of claim 34, further comprising: receiving, by the second AP to the first AP, a first frame indicating a first threshold associated with a first field of the first PPDU.

36. The method of claim 35, further comprising: comparing, by the second AP, a first value of the first field to the first threshold, wherein the transmitting the notification of reception is based on the comparing.

37. The method of any of claims 31-36, wherein the first AP operates in a power save mode when the second AP transmits the notification of reception.

38. The method of any of claims 31-37, wherein the notification of reception indicates a second value of a second field of the first PPDU addressed to the first AP.

39. The method of claims 37, wherein the notification of reception comprises a second request by the second AP for the first AP to transition from a first mode to a second mode of the power save mode.

40. The method of claim 39, wherein the first mode comprises a lower capability mode of the power save mode.

41. The method of any of claims 39-40, wherein the second mode comprises a higher capability mode of the power save mode.

42. The method of any of claims 39-41 , wherein, during the first mode, the first AP is capable of receiving PPDUs of a first category.

43. The method of claim 42, wherein, during the second mode, the first AP is capable of receiving PPDUs of the first category and of a second category.

44. The method of claim 43, wherein, during the first mode, the first AP is not capable of receiving PPDUs of the second category.

45. The method of any of claims 43-44, wherein the first PPDU is carried in a PPDU of the second category.

46. The method of any of claims 31-45, wherein the notification of reception comprises a control frame.

47. The method of claim 46, wherein the control frame comprises a trigger frame, a multi-user request to send (MU- RTS) frame, or a block ack request (BAR) frame.

48. The method of claim 31-47, wherein the notification of reception comprises a padding field.

49. The method of any of claims 31-48, wherein the first AP belongs to a basic service set (BSS) and the second AP belongs to an overlapping basic service set (OBSS) relative to the BSS.

50. 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 1-49.

51. 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 1-49.