Shared access point (AP) triggering of scheduled transmission opportunity (TXOP) allocation

Abstract

A first access point (AP) receives from a second AP, during a transmission opportunity (TXOP) of the second AP, a first frame polling the first AP regarding receiving a first time allocation and a third AP regarding receiving a second time allocation within the TXOP. The first AP transmits to the second AP a second frame in response to the first frame, indicating that the first AP wishes to receive the first time allocation. The first AP receives from the second AP a third frame allocating the first time allocation to the first AP and transmits to the second AP a clear to send (CTS) frame in response to the third frame. Based on the first AP finishing communicating before an end of the first time allocation, the first AP transmits to the second AP a fourth frame, where the fourth frame comprises a TXOP return frame.

Description

TITLEShared Access Point (AP) Triggering of Scheduled Transmission Opportunity (TXOP) AllocationCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 670,185, filed July 12,2024, 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 multi-AP network.

[0006] FIG. 4 illustrates Enhanced Distributed Channel Access (EDCA) and Coordinated Orthogonal Frequency Division Multiple Access (COFDMA).

[0007] FIG. 5 illustrates an example network that includes a coordinated AP set.

[0008] FIG. 6 illustrates an example multi-AP operation procedure.

[0009] FIG. 7 illustrates an example multi-AP sounding phase.

[0010] FIG. 8 illustrates an example multi-AP downlink data transmission phase.

[0011] FIG. 9 illustrates an example multi-AP uplink data transmission phase.

[0012] FIG. 10 illustrates Enhanced Distributed Channel Access (EDCA) and Coordinated Time Division Multiple Access (CTDMA).

[0013] FIG. 11 illustrates an example of a Multi-User Request-to-Send (MU-RTS) trigger frame which may be used in a triggered Transmit Opportunity (TXOP) sharing (TXS) procedure.

[0014] FIG. 12 illustrates an example of a triggered TXS procedure (Mode =1 ).

[0015] FIG. 13 illustrates an example of a triggered TXS procedure (Mode =2).

[0016] FIG. 14 illustrates an example of an existing CTDMA procedure.

[0017] FIG. 15 illustrates another example of an existing CTDMA procedure.

[0018] FIG. 16 illustrates an example that highlights a problem that may arise in association with an implementation of a CTDMA procedure.

[0019] FIG. 17 illustrates an example of a procedure according to an embodiment.

[0020] FIG. 18 illustrates another example of a procedure according to an embodiment.

[0021] FIG. 19 illustrates an example process according to an embodiment.

[0022] FIG. 20 illustrates another example process according to an embodiment.

[0023] FIG. 21 illustrates another example process according to an embodiment.DETAILED DESCRIPTION

[0024] 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.

[0025] 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.

[0026] 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.

[0027] If A and B are sets and every element of A is an element of B, A is called a subset of B. In this specification, only non-empty sets and subsets are considered. For example, possible subsets of B = {STA1 , STA2] are: {STA1 }, {STA2}, and {STA1 , STA2}. The phrase “based on” (or equally “based at least on”) isindicative that the phrase following the term “based on” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “in response to” (or equally “in response at least to”) is indicative that the phrase following the phrase “in response to” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “depending on” (or equally “depending at least to”) is indicative that the phrase following the phrase “depending on" is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments. The phrase “employing / using” (or equally “employing / using at least”) is indicative that the phrase following the phrase “employing / using” is an example of one of a multitude of suitable possibilities that may, or may not, be employed to one or more of the various embodiments.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 combinationthereof, which may be behaviorally equivalent. For example, modules may be implemented as a software routine written in a computer language configured to be executed by a hardware machine (such as C, C++, Fortran, Java, Basic, Matlab or the like) or a modeling / simulation program such as Simulink, Stateflow, GNU Octave, or LabVIEWMathScript. It may be possible to implement modules using physical hardware that incorporates discrete or programmable analog, digital and / or quantum hardware. Examples of programmable hardware comprise: computers, microcontrollers, microprocessors, application-specific integrated circuits (ASICs); field programmable gate arrays (FPGAs); and complex programmable logic devices (CPLDs). Computers, microcontrollers and microprocessors are programmed using languages such as assembly, C, C++ or the like. FPGAs, ASICs and CPLDs are often programmed using hardware description languages (HDL) such as VHSIC hardware description language (VHDL) or Verilog that configure connections between internal hardware modules with lesser functionality on a programmable device. The mentioned technologies are often used in combination to achieve the result of a functional module.

[0032] FIG. 1 illustrates example wireless communication networks in which embodiments of the present disclosure may be implemented.

[0033] As shown in FIG. 1 , the example wireless communication networks may include an Institute of Electrical and Electronic Engineers (IEEE) 802.11 (WLAN) infra-structure network 102. WLAN infra-structure network 102 may include one or more basic service sets (BSSs) 1 10 and 120 and a distribution system (DS) 130.

[0034] BSS 110-1 and 110-2 each includes a set of an access point (AP or AP STA) and at least one station (STA or non-AP STA). For example, BSS 110-1 includes an AP 104-1 and a STA 106-1 , and BSS 1 10-2 includes an AP 104-2 and STAs 106-2 and 106-3. The AP and the at least one STA in a BSS perform an association procedure to communicate with each other.

[0035] 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).

[0036] 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.

[0037] The example wireless communication networks illustrated in FIG. 1 may further include one or more ad-hoc networks or independent BSSs (IBSSs). An ad-hoc network or IBSS is a network that includes a plurality of STAs that are within communication range of each other. The plurality of STAs are configured so that they may communicate with each other using direct peer-to-peer communication (i.e., not via an AP).

[0038] 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 doesnot 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.

[0039] 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.

[0040] 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 802.1 1 protocol to be used to transmit the payload.

[0041] A frequency band may include one or more sub-bands or frequency channels. For example, PPDUs conforming to the IEEE 802.11 n, 802.11ac, 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.

[0042] 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.

[0043] 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 morecontrollers 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.

[0044] 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.

[0045] 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.

[0046] FIG. 3 illustrates an example multi-AP network 300. Example multi-AP network 300 may be a multi- AP network in accordance with the Wi-Fi Alliance standard specification for multi-AP networks. As shown in FIG. 3, multi-AP network 300 may include a multi-AP controller 302 and a plurality of multi-AP groups (or multi-AP sets) 304, 306, and 308.

[0047] Multi-AP controller 302 may be a logical entity that implements logic for controlling the APs in multi- AP network 300. Multi-AP controller 302 may receive capability information and measurements from the APs and may trigger AP control commands and operations on the APs. Multi-AP controller 302 may also provide onboarding functionality to onboard and provision APs onto multi-AP network 300.

[0048] Multi-AP groups 304, 306, and 308 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.

[0049] 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 referredto 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.

[0050] 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 302 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.

[0051] 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.

[0052] 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.

[0053] 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 CSR, 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 associatedSTAs, 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.

[0054] 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.

[0055] 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.

[0056] 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, CSR may require PPDU-level synchronization, whereas CBF 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.

[0057] 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. CBF 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. CSR 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.

[0058] 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.

[0059] In COFDMA, the master AP may share a portion of its TXOP with multiple APs by assigning each of the multiple APs a respective frequency resource (e.g., channel / subchannel) of available frequency resources. COFDMA is illustrated in FIG. 4 as a multi-AP channel access, compared with Enhanced Distributed Channel Access (EDCA). As shown in FIG. 4, in EDCA, channel access by multiple APs (e.g., AP1 , AP2) may occur in consecutive time periods (e.g., TXOPs). During a given channel access, the channel (e.g., 80 MHz) in its entirety may be used by a single AP. In contrast, in COFDMA, access by multiple APs (multi-AP channel access) may take place in a same time period (e.g., same TXOP or same portion of a TXOP) over orthogonal frequency resources. For example, as shown in FIG. 4, an 80 MHz channel may be divided into four non-overlapping 20 MHz channels, each assigned to a respective AP of the multiple APs. The multiple APs may transmit in a coordinated manner, simultaneously in the same time period, to achieve a multi-AP transmission. In the multi-AP transmission, each of the multiple APs may transmit a PPDU to one or more STAs.

[0060] FIG. 5 illustrates an example network 500 that includes a coordinated AP set. As shown in FIG. 5, the coordinated AP set may include two APs - AP 502-1 and AP 502-2. 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 502-1 and 502-2. For example, a STA 504-1 may be associated with AP 502-1 , and a STA 504-2 may be associated with AP 502-2.

[0061] APs 502-1 and 502-2 may belong to the same ESS as described above in FIG. 1 . In such a case, APs 502-1 and 502-2 may be connected by a DS to support ESS features. In addition, as part of a coordinated AP set, APs 502-1 and 502-2 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 stateinformation 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.

[0062] Typically, one of APs 502-1 and 502-2 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.

[0063] 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. 5, if AP 502-1 supports JT and CSR while AP 502-2 supports CSR and CBF, both APs may only perform CSR 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.

[0064] CSR is one type of multi-AP coordination that may be supported by AP 501 -1 and AP 502-2 as shown in FIG. 5. Spatial reuse using CSR can be more stable than non-AP coordinated spatial reuse schemes such as OBSS PD-based SR and PSR-based SR. For example, in example network 500, APs 502- 1 and 502-2 may perform a joint sounding operation in order to measure path loss (PL) on paths of network 500. For example, the joint sounding operation may result in the measurement of PL 508 for the path between APs 502-1 and 502-2, path loss 510 for the path between AP 502-1 and STA 504-2, and path loss 512 for the path between AP 502-2 and STA 504-1 . The measured path loss information may then be shared between APs 502-1 and 502-2 (e.g., using the backhaul) to allow for simultaneous transmissions by APs 502-1 and 502-2 to their associated STAs 504-1 and 504-2 respectively. Specifically, one of APs 502-1 and 502-2 obtains a TXOP to become the Master AP. The Master AP may then send a CSR announcement frame to the other AP(s). In an embodiment, the Master AP may perform a polling operation, before sending the CSR 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 CSR announcement frame. In the CSR 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 toInterference Ratio (SIR) margin to support the interference due to the transmission of the Master AR to its target STA.

[0065] FIG. 6 illustrates an example 600 of a multi-AP operation procedure. In example 600, the multi-AP operation procedure is illustrated with respect to a multi-AP network that includes APs 602 and 604 and STAs 606 and 608. In an example, APs 602 and 604 may form a multi-AP group. AP 602 may be the master AP and AP 604 may be a slave AP of the multi-AP group. For example, AP 602 may obtain a TXOP making it the master AP of the multi-AP group. Alternatively, AP 602 may be designated as the master AP by a multi- AP controller.

[0066] As shown in FIG. 6, 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 610, a multi-AP data sharing phase 612, a multi- AP sounding phase 614, and a multi-AP data transmission phase 616.

[0067] 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.

[0068] Multi-AP selection phase 610 may include procedures for soliciting, selecting, or designating slave AP(s) for a multi-AP group by a master AP. As seen in FIG. 6, the multi-AP selection phase may include transmissions of frame 618 from AP 602 and frame 620 from AP 604. AP 602 may transmit frame 618 to solicit information regarding the buffer status of AP 604. In response, AP 604 may transmit frame 620 to inform AP 602 of its and its associated STAs buffer status and / or whether it intends to join multi-AP operation. Multi-AP selection phase 610 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 MIMO 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).

[0069] Multi-AP data sharing phase 612 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 612 may be optional for some multi-AP data transmission schemes. For example, phase 612 may be required for JT / JR as data frames may be exchanged between APs before or after multi-AP data transmission phase 616.

[0070] Multi-AP data sharing phase 612 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 612 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. 6, in phase 612, AP 602 may transmit a frame 622, which may be received by AP 604. Frame 622 may include MPDUs that AP 602 wishes to transmit to associated STAs using a multi-AP operation. Similarly, AP 604 may transmit a frame 624, which may be received by AP 602. Frame 624 may include MPDUs that AP 604 wishes to transmit to associated STAs using a multi-AP operation.

[0071] Multi-AP sounding phase 614 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 614 may be optional for some multi-AP transmission schemes, such as COFDMA, CDTMA, and CSR. For example, phase 614 may be performed by the master AP to aid in resource unit allocation when orchestrating a COFDMA transmission.

[0072] Multi-AP data transmission phase 616 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 616 may include optional synchronization between APs ofthe multi-AP group, before exchange of data frames between APs and STAs within the multi-AP group.

[0073] The order of phases 610, 612, 614 and 616 may be different than shown in FIG. 6. For example, in COFDMA, phase 616 may occur immediately after phase 610, whereas, in JT / JR, phase 612 may occur after phase 610. Further, as mentioned above, some phases may be optional and may or may not be present. For example, phase 614 may not be required for COFDMA but may be required for JT / JR.

[0074] FIG. 7 illustrates an example multi-AP sounding phase 700. Example multi-AP sounding phase 700 may be an example of multi-AP sounding phase 614. As shown in FIG. 7, example multi-AP sounding phase 700 may include a master AP 702 and a slave AP 704 of a multi-AP group. Example multi-AP sounding phase 700 may further include a STA 706 associated with AP 702 and a STA 708 associated with AP 704.

[0075] As shown in FIG. 7, multi-AP sounding phase 700 may include frame exchanges to allow AP 702 (the master AP) to acquire channel state information (CSI) of channels in the multi-AP group. In an implementation, phase 700 may include a first subphase 710 and a second subphase 712.

[0076] During the first subphase 710, APs may initiate channel sounding and STAs may estimate channel state information (CSI). For example, AP 702 may transmit a frame 714 to AP 704 (the slave AP) to trigger multi-AP sounding. Frame 714 may comprise a multi-AP trigger frame. Subsequently, APs 702 and 704 may transmit respectively announcement frames 716-1 and 716-2 to their respective associated STAs 706 and 708 to announce the transmission of sounding frames. Frames 716-1 and 716-2 may comprise multi-AP null data packet announcement (NDPA) frames. Frames 716-1 and 716-2 may be transmitted simultaneously. Next, APs 702 and 704 may transmit respectively frames 718-1 and 718-2 to STAs 706 and 708 respectively. Frames 718-1 and 718-2 may comprise multi-AP null data packet (NDP) frames. STAs 706 and 708 receive frames 718-1 and 718-2 respectively and perform channel estimation of the channels from AP 702 to STA 706 and from AP 704 to STA 708, respectively.

[0077] During the second subphase 712, APs may initiate a procedure for STAs to feed back channel estimates to the APs. For example, AP 702 may transmit a frame 720 to trigger STAs 706 and 708 to transmit their channel estimates to APs 702 and 704 respectively. Frame 720 may comprise a multi-AP trigger frame. In response, STAs 706 and 708 may transmit respectively frames 722 and 724 including feedback of channel estimates to APs 702 and 704 respectively. Frames 722 and 724 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.

[0078] FIG. 8 illustrates an example multi-AP downlink data transmission phase 800. Example multi-AP downlink data transmission phase 800 may be an example of multi-AP data transmission phase 616. As shown in FIG. 8, example multi-AP downlink data transmission phase 800 may include a master AP 802 and a slave AP 804 of a multi-AP group. Example multi-AP downlink data transmission phase 800 may further include a STA 806 associated with AP 802, and a STA 808 associated with AP 804.

[0079] As shown in FIG. 8, multi-AP downlink data transmission phase 800 may include frame exchanges to enable master AP 802 to coordinate with slave AP 804 to perform specific multi-AP transmission schemes with their associated STAs 806 and 808 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.

[0080] As shown in FIG. 8, master AP 802 may begin phase 800 by transmitting a frame 810 to AP 804. Frame 810 may include information related to AP 804 (e.g., an identifier of AP 804), 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 804 to acknowledge frame 810. Frame 810 may comprise a control frame. For example, frame 810 may comprise a multi-AP trigger frame.

[0081] Slave AP 804 may receive frame 810 and may use the synchronization information to synchronize with master AP 802. Subsequently, APs 802 and 804 may perform data transmission to their associated STAs 806 and 808 respectively. Specifically, AP 802 may transmit a data frame 812 to its associated STA 806, and AP 804 may transmit a data frame 814 to its associated STA 808. Depending on the multi-APtransmission scheme being used, APs 802 and 804 may transmit frames 812 and 814 respectively to STAs in different BSSs. For example, when the multi-AP transmission scheme is JT / JR, AP 802 may also transmit frame 812 to STA 808 associated with slave AP 804, and AP 804 may also transmit frame 814 to STA 808 associated with AP 804. The resources for transmitting and receiving frames 812 and 814 may depend on the specific multi-AP transmission scheme adopted.

[0082] STAs 806 and 808 may acknowledge frames 812 and 814 respectively. For example, STA 806 may transmit a frame 816 to AP 802, and STA 808 may transmit a frame 818 to AP 804. Frames 816 and 818 may comprise block ack (BA) frames. STAs 806 and 808 may also transmit frames 816 and 818 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 806 may also transmit frame 816 to AP 804, and STA 808 may also transmit frame 818 to AP 802. The resources for transmitting and receiving frames 816 and 818 may depend on the specific multi-AP transmission scheme adopted.

[0083] FIG. 9 illustrates an example multi-AP uplink data transmission phase 900. Example multi-AP uplink data transmission phase 900 may be an example of multi-AP data transmission phase 616. As shown in FIG. 9, example multi-AP uplink data transmission phase 900 may include a master AP 902 and a slave AP 904 of a multi-AP group. Example multi-AP uplink data transmission phase 900 may further include STAs 906 and 908 associated with AP 902, and a STA 910 associated with AP 904.

[0084] As shown in FIG. 9, example multi-AP uplink data transmission phase 900 may include frame exchanges to enable master AP 902 to coordinate with slave AP 904 to perform specific multi-AP transmission schemes with STAs 906, 908, and 910910. The multi-AP transmission schemes may include COFDMA, CTDMA, CSR, CBF, JT / JR, or a combination of two or more of the aforementioned schemes.

[0085] As shown in FIG. 9, master AP 902 may begin phase 900 by transmitting a frame 912 to AP 904. Frame 912 may include information related to AP 904 (e.g., an identifier of AP 904), 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 904 to acknowledge frame 912. Frame 912 may comprise a control frame. For example, frame 912 may comprise a multi-AP trigger frame.

[0086] Slave AP 904 may receive frame 912 and may use the synchronization information to synchronize with master AP 902. Subsequently, APs 902 and 904 may solicit uplink data transmissions from their associated STAs 906, 908 and 910 using trigger frames. Specifically, AP 902 may transmit a trigger frame 914 to its associated STAs 906 and 908, and AP 904 may transmit a trigger frame 916 to its associated STA 910. Depending on the multi-AP transmission scheme being used, APs 902 and 904 may also transmit frames 914 and 916 respectively to STAs in different BSSs. For example, when the multi-AP transmission scheme is JT / JR, AP 902 may also transmit frame 914 to STA 910 associated with slave AP 904, and AP 904 may also transmit frame 916 to STAs 906 and 908 associated with AP 902. The resources for transmitting and receiving frames 914 and 916 may depend on the specific multi-AP transmission scheme adopted.

[0087] STAs 906 and 908 may respond to frame 914, STA 910 may respond to frame 916. For example, STAs 906 and 908 may transmit frames 918 and 920 respectively to AP 902, while STA 910 may transmit a frame 922 to AP 904. Frames 918, 920, and / or 922 may be transmitted simultaneously. Frames 918, 920, and 922 may comprise data frames or null data frames. STAs 906, 908, and 910 may also transmit frames 918, 920, and 922 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 906 and 908 may also transmit respective frames 918 and 920 to AP 904, and STA 910 may also transmit frame 922 to AP 902. The resources for transmitting and receiving frames 918, 920, and 922 may depend on the specific multi-AP transmission scheme adopted. AP 902 may acknowledge frames 918 and 920 by transmitting a multi-STA BA frame 924 to STAs 906 and 908. AP 904 may acknowledge frame 922 by transmitting a BA frame 926 to STA 910.

[0088] FIG. 10 illustrates Enhanced Distributed Channel Access (EDCA) and Coordinated Time Division Multiple Access (CTDMA). In CTDMA, an AP (generally referred to as a master AP or a sharing AP) may share a portion of its TXOP with one or more APs (generally referred to as slave APs or shared APs). Specifically, the sharing AP may assign / allocate each of the one or more APs a respective time period within the TXOP of the sharing AP. A shared AP may use its allocated time period to communicate with one or more STA. CTDMA is illustrated in FIG. 10 as a multi-AP channel access scheme, compared with Enhanced Distributed Channel Access (EDCA). As shown in FIG. 10, in EDCA, channel access by multiple APs (e.g., AP1 , AP2) may occur in consecutive time periods (e.g., TXOPs), where each AP has its own TXOP. During a given channel access, the channel in its entirety may be used by a single AP for the duration of the TXOP. In contrast, in CTDMA, access by multiple APs may take place in a same TXOP over consecutive time periods. For example, as shown in FIG. 10, a TXOP may be divided into two non-overlapping time periods, each assigned to a respective AP of the multiple APs. The multiple APs may transmit in a coordinated manner in the same TXOP consecutively. In an example, as shown in FIG. 10, a master / sharing AP (e.g., AP1 ) may use itself a first portion of a first TXOP and may share a second portion of the first TXOP with a slave / shared AP (e.g., AP2). In another example, the master / shared AP (e.g., AP1) may share a first portion of a second TXOP with a slave / shared AP (e.g., AP2) and may use itself a second portion of the second TXOP.

[0089] Triggered TXOP sharing (TXS) is a technique introduced in the IEEE 802.1 1 be standard amendment. TXS allows an AP to allocate a time duration within an obtained TXOP to a STA for transmitting one or more non-trigger-based (non-TB) PPDUs. For the TXS procedure, the AP may transmit a multi-user request-to-send (MU-RTS) trigger frame with a triggered TXOP sharing mode subfield set to a non-zero value. The MU-RTS trigger frame is a trigger frame for triggering clear-to-send (CTS) frame(s) from multiple users. An MU-RTS trigger frame with the triggered TXOP sharing mode subfield set to a non-zero value is called an MU-RTS TXS trigger (MRTT) frame.

[0090] In an example, when the triggered TXOP sharing mode subfield is set to 1 , the STA may transmit the one or more non-TB PPDUs to the AP during the allocated time duration. In an example, when the triggered TXOP sharing mode subfield is set to 2, the STA may transmit the one or more non-TB PPDUs to the AP or a peer STA during the allocated time duration. The peer STA may be a STA with a connection for peer-to-peer (P2P) communication or direct communication with the STA. In an example, the direct wireless link is established according to the tunneled direct link setup (TDLS) protocol.

[0091] FIG. 11 illustrates an example of a Multi-User Request-to-Send (MU-RTS) trigger frame which may be used in a triggered Transmit Opportunity (TXOP) sharing (TXS) procedure. As shown in FIG. 11 , example MU-RTS trigger frame 1 100 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.

[0092] In an example, the common info field may be a high-efficiency (HE) variant common info field or an extremely high throughput (EHT) variant common info field. An EHT variant common info field may comprise, as shown in FIG. 11 , one or more of the following subfields: trigger type, UL length, more TF, CS required, UL BW, Gl and HE / EHT-LTF Type / Triggered TXOP sharing mode, number of HE / EHT-LTF symbols, LDPC extra symbol segment, AP Tx Power, Pre-FEC padding factor, PE disambiguity, UL spatial reuse, HE / EHT P160, special user info field flag, EHT reserved, reserved, or trigger dependent common info.

[0093] The trigger type subfield indicates that frame 1100 is an MU-RTS trigger frame.

[0094] 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 nonzero value (e.g., 1 or 2). When the triggered TXOP sharing mode subfield is set to a non-zero value, an MU- RTS trigger frame is an MRTT frame. 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.

[0095] The user info list field may include one or more user info fields. In an example, an EHT variant user info field may comprise, as shown in FIG. 11 , one or more of the following subfields: AID12, RU allocation, allocation duration, reserved, or PS160.

[0096] The AID12 subfield may indicate an association identifier (AID) of a STA that may use a time indicated by the allocation duration subfield.

[0097] The RU allocation subfield may indicate the location and size of the RU allocated for a STA indicated by the AID12 subfield.

[0098] The allocation duration subfield may indicate a time allocated by an AP transmitting MU-RTS trigger frame 1100 (when triggered TXOP sharing mode subfield is a non-zero value). The allocated time may be a portion of a TXOP obtained by the AP. In an example embodiment, the allocation duration subfield may indicate a first time period.

[0099] FIG. 12 illustrates an example 1200 of a TXS procedure (Mode =1 ). As shown in FIG. 12, the TXS procedure may begin by an AP 1210 transmitting an MRTT frame 1220 to a STA 1211. MRTT frame 1220 may allocate a portion of a TXOP obtained by AP 1210 to STA 121 1 and may indicate a TXS mode equal to1 . STA 121 1 receiving MRTT frame 1220 may use the allocated time to transmit one or more non-TB PPDUs to AP 1210. The one or more non-TB PPDUs may comprise a data frame, a control frame, a management frame, or an action frame

[0100] In an example, MRTT frame 1220 may comprise a triggered TXOP sharing mode subfield that indicates the TXS mode and / or subfield that indicates a first time period corresponding to the allocated time. In an example, the first time period may be set to a value of X microseconds (us).

[0101] STA 121 1 may respond to MRTT frame 1220 by transmitting a CTS frame 1221 to AP 1210. Subsequently, STA 1211 may transmit non-TB PPDUs 1222, 1224 comprising one or more data frame to AP 1210 during the first time period indicated in MRTT frame 1220. In an example, AP 1210 may transmit one or more Block Ack (BA) frames 1223, 1225 in response to the one or more data frames contained in non-TB PPDUs 1222, 1224 received from STA 1211 .

[0102] FIG. 13 illustrates an example 1300 of a TXS procedure (Mode =2). As shown in FIG. 13, the TXS procedure may begin by an AP 1310 transmitting an MRTT frame 1320 to a STA 1311. MRTT frame 1320 may allocate a portion of a TXOP obtained by AP 1310 to STA 131 1 and may indicate a TXS mode equal to2. STA 131 1 receiving MRTT frame 1320 may use the allocated time to transmit one or more non-TB PPDUs to STA 1312. The one or more non-TB PPDUs may comprise a data frame, a control frame, a management frame, or an action frame.

[0103] In an example, MRTT frame 1320 may comprise a triggered TXOP sharing mode subfield that indicates the TXS mode and / or subfield that indicates a first time period corresponding to the allocated time. In an example, the first time period may be set to a value of Y microseconds (us).

[0104] STA 131 1 may respond to MRTT frame 1320 by transmitting a CTS frame 1321 to AP 1310. Subsequently, STA 1311 may transmit non-TB PPDUs 1322, 1324 comprising one or more data frame to STA 1312 during the first time period indicated in MRTT frame 1320. In an example, STA 1312 may transmit one or more BA frames 1323, 1325 in response to the one or more data frames contained in non-TB PPDUs 1322, 1324 received from STA 1311.

[0105] In CTDMA, one approach for TXOP sharing may be achieved via the TXS procedure described above. The TXS procedure may be used to allow a sharing AP, which obtains a TXOP and is the TXOP owner, to allocate a time duration within its obtained TXOP to a shared AP for downlink and / or uplink transmission between the shared AP and its associated STAs.

[0106] FIG. 14 illustrates an example 1400 of an existing CTDMA procedure. As shown in FIG. 14, example 1400 may include APs 1402, 1404, and 1406. Each of APs 1402, 1404, and 1406 may serve one or more associated STAs (not shown in FIG. 14). AP 1402, AP 1404, and AP 1406 may be members of a multi-AP group. AP 1402 may be a sharing / master AP of the multi-AP group. AP 1404 and AP 1406 may be shared / slave APs of the multi-AP group. In example 1400, it is assumed that APs 1402, 1404, and 1406 are within communication range of each other.

[0107] As shown in FIG. 14, the procedure may begin with AP 1402 transmitting a frame 1412 after obtaining a TXOP 1410. In an example, before transmitting frame 1412, AP 1402 may be configured to poll AP 1404 and AP 1406 about buffered traffic of AP 1404 and AP 1406 (including priorities of the buffered traffic of AP 1404 and AP 1406), respectively (not shown in FIG. 14). The buffered traffic of AP 1404 may include buffered traffic at AP 1404 for downlink transmission to associated STA(s) of AP 1404 and / or buffered traffic at associated STA(s) of AP 1404 for uplink transmission to AP 1404. The buffered traffic of AP 1406 may include buffered traffic at AP 1406 for downlink transmission to associated STA(s) of AP 1406 and / or buffered traffic at associated STA(s) of AP 1406 for uplink transmission to AP 1406. In another example, AP 1402 may have information in advance regarding the buffered traffic of AP 1404 and AP 1406. AP 1402 may be configured to, when AP 1402 has advance information regarding the buffered traffic of AP 1404 and AP 1406, not transmit a polling frame to receive updated information regarding the buffered traffic of AP 1404 and AP 1406. Based on AP 1402 being configured not to transmit the polling frame, AP 1402 may not transmit a polling frame before transmitting frame 1412.

[0108] Based on the information about the buffered traffic of AP 1404 and AP 1406, AP 1402 may transmit a frame 1412 comprising information regarding AP 1404 and AP 1406 being scheduled to communicate within TXOP 1410. In an example, frame 1412 may indicate a scheduled transmission time of a frame 1418 (e.g ., a TXOP allocation frame) to be transmitted by AP 1402 to AP 1404, where frame 1418 allocates a first portion of TXOP 1410 (hereinafter "first time allocation”) to AP 1404. In an example, frame 1412 may indicate a first duration (denoted T1 in FIG. 14) of the first time allocation. In an example, frame 1412 may further indicate a scheduled transmission time of a frame 1424 (e.g., a TXOP allocation frame) to be transmitted by AP 1402 to AP 1406, where frame 1424 allocates a second portion of TXOP 1410 (hereinafter "second time allocation") to AP 1406. In an example, frame 1412 may indicate a second duration (denoted T2 in FIG. 14) of the second time allocation. As such, frame 1412 announces the first time allocation and the second time allocation to AP 1404 and AP 1406 respectively.

[0109] In an example, frame 1412 may comprise a schedule announcement frame. In an example, the schedule announcement frame may comprise a trigger frame, such as an MU-RTS trigger frame. In an example, the scheduled transmission time of frame 1418 and the scheduled transmission time of frame 1424 may be indicated in a duration field, a subfield of a common info field, or a subfield of a user info list field of the trigger frame. In an example, the first duration of the first time allocation to AP 1404 may be indicated in one or more subfields of a first user info field of a user info list field of the trigger frame. In an example, the second duration of the second time allocation to AP 1406 may be indicated in one or more subfields of a second user info field of a user info list field of the trigger frame.

[0110] On receiving frame 1412, AP 1404 may determine the scheduled transmission time of frame 1418 and the first duration of the first time allocation to be allocated to AP 1404 in frame 1418. On receiving frame 1412, AP 1406 may determine the scheduled transmission time of frame 1424 and the second duration of the second time allocation to be allocated to AP 1406 in frame 1424. In response to frame 1412, AP 1404 may transmit a frame 1414 to AP 1402. In response to frame 1412, AP 1406 may transmit a frame 1416 to AP 1402. In an example, frame 1414 and frame 1416 may comprise schedule announcement response frames. In another example, frame 1414 and frame 1416 may comprise acknowledgment frames. In another example, frame 1414 and frame 1416 may comprise clear-to-send (CTS) frames.

[0111] In an example, on receiving frame 1414 and / or frame 1416, AP 1402 may transmit frame 1418. In example 1400, frame 1418 may comprise / indicate an allocation for AP 1404. The allocation may correspond to the first time allocation announced in frame 1412. The allocation may indicate the first duration (denoted T1 in FIG. 14) of the first time allocation. In an example, frame 1418 may comprise an MRTT frame. In an example, the first duration may be indicated in an allocation duration subfield of a user info list field of the MRTT frame. In another example (not shown in FIG. 14), on receiving frame 1414 and frame 1416, AP 1402 may communicate with one or more associated STAs before transmitting frame 1418.

[0112] On receiving frame 1418, AP 1404 may transmit a frame 1420 to AP 1402. In an example, frame 1420 may comprise a response frame. In an example, where frame 1418 is an MRTT frame, frame 1420 may be a CTS frame. After transmitting frame 1420, AP 1404 may communicate with its associated STA(s) during a time period 1422 of the first duration of the first time allocation. In an example, during time period 1422, AP 1404 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1404.

[0113] In example 1400, AP 1404 may finish communicating with its associated STA(s) by the end of the first duration (T1) of the first time allocation.

[0114] In an example, being the TXOP holder, AP 1402 may regain control of the TXOP a SIFS after the end of the first duration (T1). In another example, being the TXOP holder, AP 1402 may regain control of the TXOP a point coordination function (PCF) IFS (PIFS) after the end of the first duration (T1 ). As such, AP 1402 may transmit frame 1424 a SIFS or a PIFS after the end of the first duration (T1 ).

[0115] In example 1400, as announced in frame 1412, frame 1424 may comprise / indicate an allocation for AP 1406. The allocation may correspond to the second time allocation announced in frame 1412. The allocation may indicate the second duration (denoted T2 in FIG. 14) of the second time allocation. In an example, frame 1424 may comprise an MRTT frame. In an example, the second duration may be indicated in an allocation duration subfield of a user info list field of the MRTT frame.

[0116] On receiving frame 1424, AP 1406 may transmit a frame 1426 to AP 1402. In an example, frame 1426 may comprise a response frame. In an example, where frame 1424 is an MRTT frame, frame 1426 may be a CTS frame. After transmitting frame 1426, AP 1406 may communicate with its associated STA(s) during a time period 1428 of the second duration of the second time allocation. In an example, during time period 1428, AP 1406 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1406.

[0117] In example 1400, AP 1406 may finish communicating with its associated STA(s) by the end of the second duration (T2) of the second time allocation.

[0118] In an example, being the TXOP holder, AP 1402 may regain control of the TXOP a SIFS after the end of the second duration (T2). In another example, being the TXOP holder, AP 1402 may regain control of the TXOP a point coordination function (PCF) IFS (PIFS) after the end of the second duration (T2). As such, AP 1402 may transmit a frame 1430 a SIFS or a PIFS after the end of the second duration (T2). In an example, frame 1430 may comprise a control frame, a management frame, a data frame or an action frame. After regaining control of the TXOP, in an example, AP 1402 may communicate with one or more associated STAs and / or re-share the TXOP with other shared APs.

[0119] FIG. 15 illustrates an example 1500 of another existing CTDMA procedure. As shown in FIG. 15, example 1500 may include APs 1502, 1504, and 1506. Each of APs 1502, 1504, and 1506 may serve one or more associated STAs (not shown in FIG. 15). AP 1502, AP 1504, and AP 1506 may be members of a multi-AP group. AP 1502 may be a sharing / master AP of the multi-AP group. AP 1504 and AP 1506 may be shared / slave APs of the multi-AP group. In example 1500, it is assumed that APs 1502, 1504, and 1506 are within communication range of each other.

[0120] As shown in FIG. 15, the procedure may begin with AP 1502 transmitting a frame 1512 after obtaining a TXOP 1510. In an example, before transmitting frame 1512, AP 1502 may be configured to poll AP 1504 and AP 1506 about buffered traffic of AP 1504 and AP 1506 (including priorities of the buffered traffic of AP 1504 and AP 1506), respectively (not shown in FIG. 15). The buffered traffic of AP 1504 may include buffered traffic at AP 1504 for downlink transmission to associated STA(s) of AP 1504 and / or buffered traffic at associated STA(s) of AP 1504 for uplink transmission to AP 1504. The buffered traffic of AP 1506 may include buffered traffic at AP 1506 for downlink transmission to associated STA(s) of AP 1506 and / or buffered traffic at associated STA(s) of AP 1506 for uplink transmission to AP 1506. In another example, AP 1502 may have information in advance regarding the buffered traffic of AP 1504 and AP 1506. AP 1502 may be configuredto, when AP 1502 has advance information regarding the buffered traffic of AP 1504 and AP 1506, not transmit a polling frame to receive updated information regarding the buffered traffic of AP 1504 and AP 1506. Based on AP 1502 being configured not to transmit the polling frame, AP 1502 may not transmit a polling frame before transmitting frame 1512.

[0121] Based on the information about the buffered traffic of AP 1504 and AP 1506, AP 1502 may transmit a frame 1512 comprising information regarding AP 1504 and AP 1506 being scheduled to communicate within TXOP 1510. In an example, frame 1512 may indicate a scheduled transmission time of a frame 1518 (e.g., a TXOP allocation frame) to be transmitted by AP 1502 to AP 1504 and AP 1506, where frame 1518 allocates first and second portions of TXOP 1510 (hereinafter "first time allocation" and “second time allocation” respectively) to AP 1504 and AP 1506 respectively. In an example, frame 1512 may indicate a first duration (denoted T1 in FIG. 15) of the first time allocation to AP 1504. In an example, frame 1512 may further indicate a second duration (denoted T2 in FIG. 15) of the second time allocation to AP 1506. As such, frame 1512 announces the first time allocation and the second time allocation to AP 1504 and AP 1506 respectively. As shown in FIG. 15, the second time allocation may be after the first time allocation in time. In an example, the second time allocation may be immediately after the first time allocation in time such that a start time of the second time allocation coincides with an end time of the first time allocation or occurs within a SIFS or PIFS of the end time of the first time allocation. In another example, the second time allocation may be immediately after the first time allocation in time such that no third time allocation to a third AP (not shown in FIG. 15) or channel access by AP 1502 intervenes between the first time allocation and the second time allocation.

[0122] In an example, frame 1512 may comprise a schedule announcement frame. In an example, the schedule announcement frame may comprise a trigger frame, such as an MU-RTS trigger frame. In an example, the scheduled transmission time of frame 1518 may be indicated in a duration field, a subfield of a common info field, or a subfield of a user info list field of the trigger frame. In an example, the first duration of the first time allocation to AP 1504 may be indicated in one or more subfields of a first user info field of a user info list field of the trigger frame. In an example, the second duration of the second time allocation to AP 1506 may be indicated in one or more subfields of a second user info field of a user info list field of the trigger frame.

[0123] On receiving frame 1512, AP 1504 may determine the scheduled transmission time of frame 1518 and the first and second durations of the first and second time allocations to be allocated respectively to AP 1504 and AP 1506 in frame 1518. On receiving frame 1512, AP 1506 may determine the scheduled transmission time of frame 1518 and the first and second durations of the first and second time allocations to be allocated respectively to AP 1504 and AP 1506 in frame 1518. In response to frame 1512, AP 1504 may transmit a frame 1514 to AP 1502. In response to frame 1512, AP 1506 may transmit a frame 1516 to AP 1502. In an example, frame 1514 and frame 1516 may comprise schedule announcement responseframes. In another example, frame 1514 and frame 1516 may comprise acknowledgment frames. In another example, frame 1514 and frame 1516 may comprise clear-to-send (CTS) frames.

[0124] In an example, on receiving frame 1514 and / or frame 1516, AP 1502 may transmit frame 1518 In example 1500, frame 1518 may comprise / indicate first and second allocations for AP 1504 and AP 1506. The first allocation may correspond to the first time allocation announced in frame 1512. The first allocation may indicate the first duration (denoted T1 in FIG. 15) of the first time allocation. The second allocation may correspond to the second time allocation announced in frame 1512. The second allocation may indicate the second duration (denoted T2 in FIG. 15) of the second time allocation. In an example, frame 1518 may comprise an MRTT frame. In an example, the first duration may be indicated in an allocation duration subfield of a first user info field of a user info list field of the MRTT frame. In an example, the second duration may be indicated in an allocation duration subfield of a second user info field of a user info list field of the MRTT frame. In another example (not shown in FIG. 15), on receiving frame 1514 and frame 1516, AP 1502 may communicate with one or more associated STAs before transmitting frame 1518.

[0125] On receiving frame 1518, AP 1504 may determine that AP 1504 is allocated the first time allocation. AP 1504 may start communicating using the first time allocation a SIFS after transmitting a frame 1520 to AP 1502. In an example, frame 1520 may comprise a response frame. In an example, where frame 1518 is an MRTT frame, frame 1520 may be a CTS frame. After transmitting frame 1520, AP 1504 may communicate with its associated STA(s) during a time period 1522 of the first duration of the first time allocation allocated to AP 1504. In an example, during time period 1522, AP 1504 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1504.

[0126] On receiving frame 1518, AP 1506 may determine that AP 1506 is allocated the second time allocation, which is after the first time allocation allocated to AP 1504. In an example, in response to frame 1518, AP 1506 may transmit a frame 1521 to AP 1502. In an example, frame 1521 may comprise a response frame. In an example, where frame 1518 is an MRTT frame, frame 1521 may be a CTS frame. In another example, AP 1506 may not transmit a response frame in response to frame 1518. In an example, based on AP 1506 being allocated the second time allocation, AP 1506 may be configured to start communicating with its associated STA(s) after the end of the first time allocation allocated to AP 1504.

[0127] In example 1500, AP 1504 may finish communicating with its associated STA(s) by the end of the first duration (T1) of the first time allocation allocated to AP 1504. In an example, a SIFS after the end of the first duration, AP 1504 may transmit a frame 1525. In an example, frame 1525 may be a CTS frame. In another example, AP 1504 may not transmit a frame after the end of the first duration.

[0128] In an example, after the end of the first duration, AP 1506 may transmit a frame 1526 before starting to communicate within the second duration (T2) of the second time allocation. In an example, frame 1526 may be a CTS frame. After transmitting frame 1526, AP 1506 may communicate with its associated STA(s)during a time period 1528 of the second duration of the second time allocation allocated to AP 1506. In an example, during time period 1528, AP 1506 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1506.

[0129] In example 1500, AP 1506 may finish communicating with its associated STA(s) by the end of the second duration (T2) of the second time allocation.

[0130] In an example, being the TXOP holder, AP 1502 may regain control of the TXOP a SIFS after the end of the second duration (T2). In another example, being the TXOP holder, AP 1502 may regain control of the TXOP a point coordination function (PCF) IFS (PIFS) after the end of the second duration (T2). As such, AP 1502 may transmit a frame 1530 a SIFS or a PIFS after the end of the second duration (T2). In an example, frame 1530 may comprise a control frame, a management frame, a data frame or an action frame. After regaining control of the TXOP, in an example, AP 1502 may communicate with one or more associated STAs and / or re-share the TXOP with other shared APs.

[0131] FIG. 16 illustrates an example 1600 that highlights a problem that may arise in association with an implementation of a CTDMA procedure. As shown in FIG. 16, example 1600 may include APs 1602, 1604, and 1606. Each of APs 1602, 1604, and 1606 may serve one or more associated STAs (not shown in FIG. 16). AP 1602, AP 1604, and AP 1606 may be members of a multi-AP group. AP 1602 may be a sharing / master AP of the multi-AP group. AP 1604 and AP 1606 may be shared / slave APs of the multi-AP group. In example 1600, it is assumed that APs 1602, 1604, and 1606 are within communication range of each other.

[0132] As shown in FIG. 16, the procedure may begin with AP 1602 transmitting a frame 1612 after obtaining a TXOP 1610. In an example, before transmitting frame 1612, AP 1602 may be configured to poll AP 1604 and AP 1606 about buffered traffic of AP 1604 and AP 1606 (including priorities of the buffered traffic of AP 1604 and AP 1606), respectively (not shown in FIG. 16). The buffered traffic of AP 1604 may include buffered traffic at AP 1604 for downlink transmission to associated STA(s) of AP 1604 and / or buffered traffic at associated STA(s) of AP 1604 for uplink transmission to AP 1604. The buffered traffic of AP 1606 may include buffered traffic at AP 1606 for downlink transmission to associated STA(s) of AP 1606 and / or buffered traffic at associated STA(s) of AP 1606 for uplink transmission to AP 1606. In another example, AP 1602 may have information in advance regarding the buffered traffic of AP 1604 and AP 1606. AP 1602 may be configured to, when AP 1602 has advance information regarding the buffered traffic of AP 1604 and AP 1606, not transmit a polling frame to receive updated information regarding the buffered traffic of AP 1604 and AP 1606. Based on AP 1602 being configured not to transmit the polling frame, AP 1602 may not transmit a polling frame before transmitting frame 1612.

[0133] Based on the information about the buffered traffic of AP 1604 and AP 1606, AP 1602 may transmit a frame 1612 comprising information regarding AP 1604 and AP 1606 being scheduled to communicate within TXOP 1610. In an example, frame 1612 may indicate a scheduled transmission time of a frame 1618(e.g., a TXOP allocation frame) to be transmitted by AP 1602 to AP 1604 and AP 1606, where frame 1618 allocates first and second portions of TXOP 1610 (hereinafter “first time allocation" and “second time allocation” respectively) to AP 1604 and AP 1606 respectively. In an example, frame 1612 may indicate a first duration (denoted T1 in FIG. 16) of the first time allocation to AP 1604. In an example, frame 1612 may further indicate a second duration (denoted T2 in FIG. 16) of the second time allocation to AP 1606. As such, frame 1612 announces the first time allocation and the second time allocation to AP 1604 and AP 1606. As shown in FIG. 16, the second time allocation may be after the first time allocation in time. In an example, the second time allocation may be immediately after the first time allocation in time such that a start time of the second time allocation coincides with an end time of the first time allocation or occurs within a SIFS or PIFS of the end time of the first time allocation. In another example, the second time allocation may be immediately after the first time allocation in time such that no third time allocation to a third AP (not shown in FIG. 16) or channel access by AP 1602 intervenes between the first time allocation and the second time allocation.

[0134] In an example, frame 1612 may comprise a schedule announcement frame. In an example, the schedule announcement frame may comprise a trigger frame, such as an MU-RTS trigger frame. In an example, the scheduled transmission time of frame 1618 may be indicated in a duration field, a subfield of a common info field, or a subfield of a user info list field of the trigger frame. In an example, the first duration of the first time allocation to AP 1604 may be indicated in one or more subfields of a first user info field of a user info list field of the trigger frame. In an example, the second duration of the second time allocation to AP 1606 may be indicated in one or more subfields of a second user info field of a user info list field of the trigger frame.

[0135] On receiving frame 1612, AP 1604 may determine the scheduled transmission time of frame 1618 and the first and second durations of the first and second time allocations to be allocated respectively to AP 1604 and AP 1606 in frame 1618. On receiving frame 1612, AP 1606 may determine the scheduled transmission time of frame 1618 and the first and second durations of the first and second time allocations to be allocated respectively to AP 1604 and AP 1606 in frame 1618. In response to frame 1612, AP 1604 may transmit a frame 1614 to AP 1602. In response to frame 1612, AP 1606 may transmit a frame 1616 to AP 1602. In an example, frame 1614 and frame 1616 may comprise schedule announcement response frames. In another example, frame 1614 and frame 1616 may comprise acknowledgment frames. In another example, frame 1614 and frame 1616 may comprise clear-to-send (CTS) frames.

[0136] In an example, on receiving frame 1614 and frame 1616, AP 1602 may transmit frame 1618. In example 1600, frame 1618 may comprise first and second allocations for AP 1604 and AP 1606. The first allocation may correspond to the first time allocation announced in frame 1612. The first allocation may indicate the first duration (denoted T1 in FIG. 16) of the first time allocation. The second allocation may correspond to the second time allocation announced in frame 1612. The second allocation may indicate the second duration (denoted T2 in FIG. 16) of the second time allocation. In an example, frame 1618 maycomprise an MRTT frame. In an example, the first duration may be indicated in an allocation duration subfield of a first user info field of a user info list field of the MRTT frame. In an example, the second duration may be indicated in an allocation duration subfield of a second user info field of a user info list field of the MRTT frame. In another example (not shown in FIG. 16), on receiving frame 1614 and frame 1616, AP 1602 may communicate with one or more associated STAs before transmitting frame 1618.

[0137] On receiving frame 1618, AP 1604 may determine that AP 1604 is allocated the first time allocation. AP 1604 may start communicating using the first time allocation a SIFS after transmitting a frame 1620 to AP 1602. In an example, frame 1620 may comprise a response frame. In an example, where frame 1618 is an MRTT frame, frame 1620 may be a CTS frame. After transmitting frame 1620, AP 1604 may communicate with its associated STA(s) during a time period 1622 of the first duration of the first time allocation allocated to AP 1604. In an example, during time period 1622, AP 1604 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1604.

[0138] On receiving frame 1618, AP 1606 may determine that AP 1606 is allocated the second time allocation, which is after the first time allocation allocated to AP 1604. In an example, in response to frame 1618, AP 1606 may transmit a frame 1621 to AP 1602. In an example, frame 1621 may comprise a response frame. In an example, where frame 1618 is an MRTT frame, frame 1621 may be a CTS frame. In another example, AP 1606 may not transmit a response frame in response to frame 1618. In an example, based on AP 1606 being allocated the second time allocation, AP 1606 may be configured to start communicating with its associated STA(s) after the end of the first time allocation allocated to AP 1604.

[0139] In example 1600, AP 1604 may finish communicating with its associated STA(s) before the end of the first duration (T1) of the first time allocation allocated to AP 1604. For example, AP 1604 may finish communicating with its associated STA(s) at least a duration 1623 before end of the first duration. In an example, the duration 1623 may be longer than a threshold duration. For example, the threshold duration may be sufficiently long for an AP to communicate with one or more of its associated STA(s).

[0140] In accordance with the existing procedure illustrated in FIG. 16, AP 1606 may be configured to wait until the end of the first duration (T1 ) of the first time allocation before AP 1606 starts communicating at the beginning of the second duration (T2) of the second time allocation. As such, in example 1600, despite AP 1604 finishing communicating with its associated STA(s) at the end of time period 1622, AP 1606 may not start communicating with its associated STA(s) until the end of the first duration (T1) of the first time allocation, resulting in the channel being unused for at least the duration 1623 within the first time allocation. As mentioned above, the duration 1623 may be longer than the threshold duration required for an AP to communicate with one or more associated STAs. The existing procedure may thus result in channel resources being wasted unnecessarily.

[0141] After the end of the first duration (T1 ) of the first time allocation, AP 1606 transmits a frame 1626 before starting to communicate within the second duration (T2) of the second time allocation. After transmitting frame 1626, AP 1606 may communicate with one or more of its associated STAs during a time period 1628 of the second duration of the second time allocation.

[0142] Embodiments of the present disclosure, as further described below, address the above-described problem. In an aspect, a first AP may receive from a second AP, during a TXOP obtained by the second AP, a first frame indicating a first time allocation, within the TXOP, to the first AP, and a second time allocation, within the TXOP, to a third AP. In an embodiment, the first frame may allocate the first time allocation to the first AP and the second time allocation to the third AP. In another embodiment, the first frame may announce the first time allocation and the second time allocation. The first AP may transmit to the third AP a second frame that triggers the third AP to start communicating during the first time allocation. In an embodiment, the transmitting of the second frame is based on the second time allocation being after (consecutive / successive to / immediately after / the next allocation after) the first time allocation. In another embodiment, the transmitting of the second frame is based on the first AP finishing communicating with its associated STA(s) before an end of the first time allocation. As such, when the first AP finishes communicating before the end of the first time allocation, the third AP may start communicating during the first time allocation without having to wait for the start of the second time allocation. Channel resource utilization is thereby improved. Further, by the first AP triggering the third AP directly, the triggering of the third AP is done without the second AP. This reduces signaling overhead that may be caused by the first AP returning the first time allocation to the second AP, before the second AP triggers the third AP to start communicating during the first time allocation.

[0143] In another aspect, a first AP receives from a second AP, during a transmission opportunity (TXOP) obtained by the second AP, a first frame polling: the first AP regarding receiving a first time allocation within the TXOP; and a third AP regarding receiving a second time allocation within the TXOP. The first AP transmits to the second AP a second frame in response to the first frame, indicating that the first AP wishes to receive the first time allocation. The first AP receives from the second AP a third frame allocating the first time allocation to the first AP and transmits to the second AP a clear to send (CTS) frame in response to the third frame. Based on the first AP finishing communicating before an end of the first time allocation, the first AP transmits to the second AP a fourth frame during the first time allocation. In an embodiment, the fourth frame comprises a TXOP return frame.

[0144] In a further aspect, a first AP transmits, during a transmission opportunity (TXOP) obtained by the first AP, a first frame polling: a second AP regarding receiving a first time allocation within the TXOP; and a third AP regarding receiving a second time allocation within the TXOP. The first AP receives from the second AP a second frame in response to the first frame, where the receiving of the second frame indicates that the second AP wishes to receive the first time allocation. The first AP transmits to the second AP a third frame allocating the first time allocation to the second AP, and receives from the second AP a clear to send (CTS)frame in response to the third frame. Based on the second AP finishing communicating before an end of the first time allocation, the first AP receives from the second AP a fourth frame during the first time allocation. In an embodiment, the fourth frame comprises a TXOP return frame.

[0145] FIG. 17 illustrates an example 1700 of a procedure according to an embodiment. As shown in FIG. 17, example 1700 may include APs 1702, 1704, and 1706. Each of APs 1702, 1704, and 1706 may serve one or more associated STAs (not shown in FIG. 17). AP 1702, AP 1704, and AP 1706 may be members of a multi-AP group. AP 1702 may be a sharing / master AP of the multi-AP group. AP 1704 and AP 1706 may be shared / slave APs of the multi-AP group. In example 1700, it is assumed that APs 1702, 1704, and 1706 are within communication range of each other.

[0146] As shown in FIG. 17, the procedure may begin with AP 1702 transmitting a frame 1712 after obtaining a TXOP 1710. In an example, before transmitting frame 1712, AP 1702 may be configured to poll AP 1704 and AP 1706 about buffered traffic of AP 1704 and AP 1706 (including priorities of the buffered traffic of AP 1704 and AP 1706), respectively (not shown in FIG. 17). The buffered traffic of AP 1704 may include buffered traffic at AP 1704 for downlink transmission to associated STA(s) of AP 1704 and / or buffered traffic at associated STA(s) of AP 1704 for uplink transmission to AP 1704. The buffered traffic of AP 1706 may include buffered traffic at AP 1706 for downlink transmission to associated STA(s) of AP 1706 and / or buffered traffic at associated STA(s) of AP 1706 for uplink transmission to AP 1706. In another example, AP 1702 may have information in advance regarding the buffered traffic of AP 1704 and AP 1706. AP 1702 may be configured to, when AP 1702 has advance information regarding the buffered traffic of AP 1704 and AP 1706, not transmit a polling frame to receive updated information regarding the buffered traffic of AP 1704 and AP 1706. Based on AP 1702 being configured not to transmit the polling frame, AP 1702 may not transmit a polling frame before transmitting frame 1712.

[0147] Based on the information about the buffered traffic of AP 1704 and AP 1706, AP 1702 may transmit a frame 1712 comprising information regarding AP 1704 and AP 1706 being scheduled to communicate within TXOP 1710. In an example, frame 1712 may indicate a scheduled transmission time of a frame 1718 (e.g., a TXOP allocation frame) to be transmitted by AP 1702 to AP 1704 and AP 1706, where frame 1718 allocates first and second portions of TXOP 1710 (hereinafter "first time allocation” and “second time allocation” respectively) to AP 1704 and AP 1706 respectively. In an example, frame 1712 may indicate a first duration (denoted T1 in FIG. 17) of the first time allocation to AP 1704. In an example, frame 1712 may further indicate a second duration (denoted T2 in FIG. 17) of the second time allocation to AP 1706. As such, frame 1712 announces the first time allocation and the second time allocation to AP 1704 and AP 1706. As shown in FIG. 17, the second time allocation may be after the first time allocation in time. In an example, the second time allocation may be immediately after the first time allocation in time such that a start time of the second time allocation coincides with an end time of the first time allocation or occurs within a SIFS or PIFS of the end time of the first time allocation. In another example, the second time allocation may be immediatelyafter the first time allocation in time such that no third time allocation to a third AP (not shown in FIG. 17) or channel access by AP 1702 intervenes between the first time allocation and the second time allocation.

[0148] In an example, frame 1712 may comprise a schedule announcement frame. In an example, the schedule announcement frame may comprise a trigger frame, such as an MU-RTS trigger frame. In an example, the scheduled transmission time of frame 1718 may be indicated in a duration field, a subfield of a common info field, or a subfield of a user info list field of the trigger frame. In an example, the first duration of the first time allocation to AP 1704 may be indicated in one or more subfields of a first user info field of a user info list field of the trigger frame. In an example, the second duration of the second time allocation to AP 1706 may be indicated in one or more subfields of a second user info field of a user info list field of the trigger frame.

[0149] On receiving frame 1712, AP 1704 may determine the scheduled transmission time of frame 1718 and the first and second durations of the first and second time allocations to be allocated respectively to AP 1704 and AP 1706 in frame 1718. On receiving frame 1712, AP 1706 may determine the scheduled transmission time of frame 1718 and the first and second durations of the first and second time allocations to be allocated respectively to AP 1704 and AP 1706 in frame 1718. In response to frame 1712, AP 1704 may transmit a frame 1714 to AP 1702. In response to frame 1712, AP 1706 may transmit a frame 1716 to AP 1702. In an example, frame 1714 and frame 1716 may comprise schedule announcement response frames. In another example, frame 1714 and frame 1716 may comprise acknowledgment frames. In another example, frame 1714 and frame 1716 may comprise clear-to-send (CTS) frames.

[0150] In an example, on receiving frame 1714 and frame 1716, AP 1702 may transmit frame 1718. In example 1700, frame 1718 may comprise first and second allocations for AP 1704 and AP 1706. The first allocation may correspond to the first time allocation announced in frame 1712. The first allocation may indicate the first duration (denoted T1 in FIG. 17) of the first time allocation. The second allocation may correspond to the second time allocation announced in frame 1712. The second allocation may indicate the second duration (denoted T2 in FIG. 17) of the second time allocation. In an example, frame 1718 may comprise an MRTT frame. In an example, the first duration may be indicated in an allocation duration subfield of a first user info field of a user info list field of the MRTT frame. In an example, the second duration may be indicated in an allocation duration subfield of a second user info field of a user info list field of the MRTT frame. In another example (not shown in FIG. 17), on receiving frame 1714 and frame 1716, AP 1702 may communicate with one or more associated STAs before transmitting frame 1718.

[0151] On receiving frame 1718, AP 1704 may determine that AP 1704 is allocated the first time allocation. AP 1704 may start communicating using the first time allocation a SIFS after transmitting a frame 1720 to AP 1702. In an example, frame 1720 may comprise a response frame. In an example, where frame 1718 is an MRTT frame, frame 1720 may be a CTS frame. After transmitting frame 1720, AP 1704 may communicate with its associated STA(s) during a time period 1722 of the first duration of the first time allocation allocatedto AP 1704. In an example, during time period 1722, AP 1704 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1704.

[0152] On receiving frame 1718, AP 1706 may determine that AP 1706 is allocated the second time allocation, which is after the first time allocation allocated to AP 1704. In an example, in response to frame 1718, AP 1706 may transmit a frame 1721 to AP 1702. In an example, frame 1721 may comprise a response frame. In an example, where frame 1718 is an MRTT frame, frame 1721 may be a CTS frame. In another example, AP 1706 may not transmit a response frame in response to frame 1718. In an example, based on AP 1706 being allocated the second time allocation, AP 1706 may be configured to start communicating with its associated STA(s) after the end of the first time allocation allocated to AP 1704.

[0153] In example 1700, AP 1704 may finish communicating with its associated STA(s) before the end of the first duration (T1) of the first time allocation allocated to AP 1704. For example, AP 1704 may finish communicating with its associated STA(s) at least a duration 1723 before end of the first duration. In an example, the duration 1723 may be longer than a threshold duration. For example, the threshold duration may be sufficiently long for an AP to communicate with one or more associated STAs.

[0154] In an embodiment, after finishing communicating with its associated STA(s) during time period 1722, AP 1704 may be configured to transmit a frame 1724 that triggers AP 1706 to start communicating during the first duration (T1 ) of the first time allocation allocated to AP 1704. In an embodiment, the transmitting of frame 1724 is based on a start time of the second duration (T2) of the second time allocation allocated to AP 1706 being after (consecutive / successive to / immediately after / the next allocation after) an end time of the first duration (T1 ) of the first time allocation allocated to AP 1704. In other words, the transmitting of frame 1724 is based on the second time allocation being after (consecutive / successive to / immediately after / the next allocation after) the first time allocation. In another embodiment, the transmitting of frame 1724 is further based on AP 1704 finishing communicating before an end of the first time allocation.

[0155] In another embodiment, AP 1702 may instruct AP 1704 to transmit frame 1724 to AP 1706. In an implementation, AP 1704 may receive from AP 1702 an indication that AP 1704 is to transmit frame 1724 to AP 1706. In an embodiment, AP 1704 may receive the indication in frame 1718. In an embodiment, where frame 1718 comprises an MRTT frame, the indication may be provided in the common info field or the user info list field of the MRTT frame. In another embodiment, AP 1704 may receive the indication in frame 1712. In an embodiment, where frame 1712 comprises an MU-RTS trigger frame, the indication may be provided in the common info field or the user info list field of the MU-RTS trigger frame. In a further embodiment, AP 1704 may receive the indication in a separate frame. For example, in an embodiment (as shown in FIG. 17), AP 1702 may transmit to AP 1704 and AP 1706 a frame 1711 before transmitting frame 1718, where frame 171 1 comprises the indication. In an embodiment, frame 1711 may comprise a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame. In an embodiment, AP1702 may transmit frame 1711 before transmitting frame 1712. In an embodiment, AP 1702 may transmit frame 171 1 after obtaining TXOP 1710. In another embodiment, AP 1702 may transmit frame 171 1 before obtaining TXOP 1710 (not shown in FIG. 17).

[0156] In an embodiment, frame 1724 may comprise / indicate an allocation for AP 1706. The allocation may correspond to a third time portion of TXOP 1710 (hereinafter “third time allocation”). The allocation may indicate a third duration (denoted T3 in FIG. 17) of the third time allocation. In an embodiment, the third time allocation begins with the end of transmission of frame 1724 or a pre-determined duration (e.g., SIFS, PIFS, etc.) after the end of transmission of frame 1724. In an embodiment, where frame 1718 allocates the first time allocation to AP 1704 and the second time allocation to AP 1706, AP 1704 may construct frame 1724 based on frame 1718. For example, AP 1704 may determine the third time allocation based on the second time allocation indicated in frame 1718. For example, where frame 1718 is an MRTT frame and the second time allocation is indicated in a respective user info field of a user info list field of frame 1718, AP 1704 may determine the third time allocation using the contents (e.g., association identifier, RU allocation, allocation duration, etc.) of the respective user info field indicating the second time allocation. In an example, the third duration (T3) of the third time allocation may be identical to or different from the second duration (T2) of the second time allocation. In an embodiment, a start time of the third time allocation is before a start time of the second time allocation. In an embodiment, an end time of the third time allocation may be earlier than an end time of the second time allocation. In another embodiment, an end time of the third time allocation may be the same as an end time of the second time allocation.

[0157] In another embodiment, frame 1724 may not comprise / indicate an allocation for AP 1706. Instead, frame 1724 may only trigger AP 1706 to begin using TXOP 1710 for communication with its associated STA(s). In an embodiment, based on receiving frame 1724, AP 1706 may begin communicating with its associated STA(s) using the same communication parameters (e.g., RU allocation, allocation duration, etc.) as indicated in the second time allocation allocated to AP 1706 in frame 1718. In other words, frame 1724 has the effect of shifting the second time allocation in time to start earlier than initially scheduled, without changing the communication parameters to be used for the second time allocation. According to this embodiment, frame 1724 may comprise a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame, for example.

[0158] On receiving frame 1724, AP 1702 may determine that AP 1704 has finished communicating before the end of the first duration and has triggered AP 1706 to start communicating during the third time allocation (T3). In an example, in response to frame 1724, AP 1702 may transmit a frame 1725 to AP 1704. In an example, frame 1725 may comprise a response frame. In an example, where frame 1724 is an MRTT frame, frame 1725 may be a CTS frame. In another example, AP 1702 may not transmit a frame in response to frame 1724.

[0159] On receiving frame 1724, AP 1706 may determine that AP 1704 has finished communicating before the end of the first duration and that AP 1706 is to start communicating with its associated STA(s) during the third time allocation (T3). In an embodiment, AP 1706 may transmit a frame 1726 to AP 1704 in response to frame 1724. In an example, frame 1726 may comprise a response frame. In an example, where frame 1724 is an MRTT frame, frame 1726 may be a CTS frame. After transmitting frame 1726, AP 1706 may communicate with its associated STA(s) during a time period 1728 of the third time allocation allocated to AP 1706. In an example, during time period 1728, AP 1706 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1706. In example 1700, AP 1706 may finish communicating with its associated STA(s) by the end of the third duration (T3) of the third time allocation allocated to AP 1706.

[0160] In an example, being the TXOP holder, AP 1702 may regain control of the TXOP a SIFS after the end of the third duration (T3). In another example, being the TXOP holder, AP 1702 may regain control of the TXOP a point coordination function (POP) IPS (PIPS) after the end of the third duration (T3). As such, AP 1702 may transmit a frame 1730 a SIFS or a PIFS after the end of the third duration (T3). In an example, frame 1730 may comprise a control frame, a management frame, a data frame or an action frame. After regaining control of the TXOP, in an example, AP 1702 may communicate with one or more associated STAs and / or re-share the TXOP with other shared APs.

[0161] As illustrated in example 1700, based on AP 1704 being configured to (or instructed to) transmit frame 1724 to AP 1706 to trigger AP 1706 to start communicating during the first time allocation allocated to AP 1704, AP 1706 may begin using TXOP 1710 earlier than initially scheduled when AP 1704 finishes communicating before an end of the first time allocation initially allocated to AP 1704 Utilization of channel resources is thereby improved.

[0162] FIG. 18 illustrates another example 1800 of a procedure according to an embodiment. As shown in FIG. 18, example 1800 may include APs 1802, 1804, and 1806. Each of APs 1802, 1804, and 1806 may serve one or more associated STAs (not shown in FIG. 18). AP 1802, AP 1804, and AP 1806 may be members of a multi-AP group. AP 1802 may be a sharing / master AP of the multi-AP group. AP 1804 and AP 1806 may be shared / slave APs of the multi-AP group. In example 1800, it is assumed that APs 1802, 1804, and 1806 are within communication range of each other.

[0163] As shown in FIG. 18, the procedure may begin with AP 1802 transmitting a frame 1812 after obtaining a TXOP 1810. In an example, before transmitting frame 1812, AP 1802 may be configured to poll AP 1804 and AP 1806 about buffered traffic of AP 1804 and AP 1806 (including priorities of the buffered traffic of AP 1804 and AP 1806), respectively (not shown in FIG. 18). The buffered traffic of AP 1804 may include buffered traffic at AP 1804 for downlink transmission to associated STA(s) of AP 1804 and / or buffered traffic at associated STA(s) of AP 1804 for uplink transmission to AP 1804. The buffered traffic of AP 1806 may include buffered traffic at AP 1806 for downlink transmission to associated STA(s) of AP 1806 and / or buffered trafficat associated STA(s) of AP 1806 for uplink transmission to AP 1806. In another example, AP 1802 may have information in advance regarding the buffered traffic of AP 1804 and AP 1806. AP 1802 may be configured to, when AP 1802 has advance information regarding the buffered traffic of AP 1804 and AP 1806, not transmit a polling frame to receive updated information regarding the buffered traffic of AP 1804 and AP 1806. Based on AP 1802 being configured not to transmit the polling frame, AP 1802 may not transmit a polling frame before transmitting frame 1812.

[0164] Based on the information about the buffered traffic of AP 1804 and AP 1806, AP 1802 may transmit a frame 1812 comprising information regarding AP 1804 and AP 1806 being scheduled to communicate within TXOP 1810. In an example, AP 1802 may transmit frame 1812 to AP 1804 and AP 1806 in order to poll AP 1804 regarding a first time allocation within TXOP 1810 and AP 1806 regarding a second time allocation within TXOP 1810. As such, AP 1802 may determine the intent of AP 1804 and AP 1806 of receiving a time allocation from AP 1802 within TXOP 1810. In an example, frame 1812 may indicate a scheduled transmission time of a frame 1818 (e.g., a TXOP allocation frame) to be transmitted by AP 1802 to AP 1804, where frame 1818 allocates a first portion of TXOP 1810 (hereinafter “first time allocation”) to AP 1804. In an example, frame 1812 may indicate a first duration (denoted T1 in FIG. 18) of the first time allocation. In an example, frame 1812 may further indicate a scheduled transmission time of a further frame (e.g., a TXOP allocation frame) (not shown in FIG. 18) to be transmitted by AP 1802 to AP 1806, where the further frame allocates a second portion of TXOP 1810 (hereinafter “second time allocation”) to AP 1806. In an example, frame 1812 may indicate a second duration (denoted T2 in FIG. 18) of the second time allocation. As such, frame 1812 announces the first time allocation and the second time allocation to AP 1804 and AP 1806 respectively.

[0165] In an example, frame 1812 may comprise a schedule announcement frame. In an example, the schedule announcement frame may comprise a trigger frame, such as an MU-RTS trigger frame. In another example, frame 1812 may comprise a polling frame. In an example, polling frame may comprise a trigger frame. In an example, the scheduled transmission time of frame 1818 and the scheduled transmission time of the further frame (not shown in FIG. 18) may be indicated in a duration field, a subfield of a common info field, or a subfield of a user info list field of the trigger frame. In an example, the first duration of the first time allocation to AP 1804 may be indicated in one or more subfields of a first user info field of a user info list field of the trigger frame. In an example, the second duration of the second time allocation to AP 1806 may be indicated in one or more subfields of a second user info field of a user info list field of the trigger frame.

[0166] On receiving frame 1812, AP 1804 may determine the scheduled transmission time of frame 1818 and the first duration (T1 ) of the first time allocation to be allocated to AP 1804 in frame 1818. On receiving frame 1812, AP 1806 may determine the scheduled transmission time of the further frame (not shown in FIG. 18) and the second duration (T2) of the second time allocation to be allocated to AP 1806 in the further frame. In response to frame 1812, AP 1804 may transmit a frame 1814 to AP 1802. In response to frame 1812, AP1806 may transmit a frame 1816 to AP 1802. In an example, the transmitting of frames 1814 and 1816 indicate that AP 1804 and AP 1806 wish to receive the first time allocation and the second time allocation respectively. In an example, frame 1814 and frame 1816 may comprise schedule announcement response frames. In another example, frame 1814 and frame 1816 may comprise polling response frames. In another example, frame 1814 and frame 1816 may comprise acknowledgment frames. In another example, frame 1814 and frame 1816 may comprise clear-to-send (GTS) frames. In another example (not shown in FIG. 18), AP 1804 and / or AP 1806 may not transmit frame 1814 and / or frame 1816 as AP 1804 and / or AP 1806 may not wish to receive a time allocation from AP 1802 during TXOP 1810.

[0167] In an example, on receiving frame 1814 and / or frame 1816, AP 1802 may transmit frame 1818. In example 1800, frame 1818 may comprise / indicate an allocation for AP 1804. The allocation may correspond to the first time allocation announced in frame 1812. The allocation may indicate the first duration (T1) of the first time allocation allocated to AP 1804. In an example, frame 1818 may comprise an MRTT frame. In an example, the first duration may be indicated in an allocation duration subfield of a user info list field of the MRTT frame. In another example (not shown in FIG. 18), on receiving frame 1814 and frame 1816, AP 1802 may communicate with one or more associated STAs before transmitting frame 1818.

[0168] On receiving frame 1818, AP 1804 may transmit a frame 1820 to AP 1802. In an example, frame 1820 may comprise a response frame. In an example, where frame 1818 is an MRTT frame, frame 1820 may be a CTS frame. After transmitting frame 1820, AP 1804 may communicate with its associated STA(s) during a time period 1822 of the first duration (T1 ) of the first time allocation. In an example, during time period 1822, AP 1804 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1804

[0169] On receiving frame 1818, AP 1806 may transmit a frame 1821 to AP 1802. In an example, where frame 1818 is an MRTT frame allocating a first time allocation to AP 1804, frame 1821 may be a CTS frame. In another embodiment, AP 1806 may not transmit frame 1821.

[0170] In example 1800, AP 1804 may finish communicating with its associated STA(s) before the end of the first duration (T1) of the first time allocation allocated to AP 1804. For example, AP 1804 may finish communicating with its associated STA(s) at least a duration 1823 before the end of the first duration (T1 ). In an example, the duration 1823 may be longer than a threshold duration. For example, the threshold duration may be sufficiently long for an AP to communicate with one or more associated STAs.

[0171] In an embodiment, after finishing communicating with its associated STA(s) during time period 1822, AP 1804 may be configured to transmit a frame 1824 that triggers AP 1806 to start communicating during the first duration (T1 ) of the first time allocation allocated to AP 1804. In an embodiment, the transmitting of frame 1824 is based on a start time of the second duration (T2) of the second time allocation allocated to AP 1806 being after (consecutive / successive to / immediately after / the next allocation after) an end time of the first duration (T1 ) of the first time allocation allocated to AP 1804. In other words, the transmitting of frame1824 is based on the second time allocation being after (consecutive / successive to / immediately after / the next allocation after) the first time allocation. In another embodiment, the transmitting of frame 1824 is further based on AP 1804 finishing communicating before an end of the first time allocation.

[0172] In another embodiment, AP 1802 may instruct by AP 1804 to transmit frame 1824 to AP 1806. In an implementation, AP 1804 may receive from AP 1802 an indication that AP 1804 is to transmit frame 1824 to AP 1806. In an embodiment, AP 1804 may receive the indication in frame 1812. In an embodiment, where frame 1812 comprises an MU-RTS trigger frame, the indication may be provided in the common info field or the user info list field of the MU-RTS trigger frame. In another embodiment, AP 1804 may receive the indication in frame 1818. In an embodiment, where frame 1818 comprises an MRTT frame, the indication may be provided in the common info field or the user info list field of the MRTT frame. In a further embodiment, AP 1804 may receive the indication in a separate frame. For example, in an embodiment (as shown in FIG. 18), AP 1802 may transmit to AP 1804 and AP 1806 a frame 1811 before transmitting frame 1812, where frame 1811 comprises the indication. In an embodiment, frame 1811 may comprise a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame. In an embodiment, AP 1802 may transmit frame 1811 after obtaining TXOP 1810. In another embodiment, AP 1802 may transmit frame 1811 before obtaining TXOP 1810 (not shown in FIG. 18). In another embodiment (not shown in FIG. 18), instead of instructing AP 1804 to transmit frame 1824 to AP 1806, AP 1804 may solicit a TXOP return from AP 1804 by setting the TXOP return solicited field to one in frame 1812, where AP 1804 is to return a remainder of the first time allocation. In an embodiment, the remainder of the first time allocation comprises AP 1804 finishing communicating before an end of the first time allocation. As such, instead of transmitting frame 1824 to AP 1806, AP 1804 may transmit a TXOP return frame to AP 1802 during the first time allocation. In response to the TXOP return frame, AP 1802 may transmit an Ack frame when AP 1802 receives the TXOP return frame.

[0173] In an embodiment, frame 1824 may comprise / indicate an allocation for AP 1806. The allocation may correspond to a third time portion of TXOP 1810 (hereinafter “third time allocation’’). The allocation may indicate a third duration (denoted T3 in FIG. 18) of the third time allocation. In an embodiment, the third time allocation begins with the end of transmission of frame 1824 or a pre-determined duration (e.g., SIFS, PIFS, etc.) after the end of transmission of frame 1824. In an embodiment, where frame 1812 announces the first time allocation to AP 1804 and the second time allocation to AP 1806, AP 1804 may construct frame 1824 based on frame 1812. For example, AP 1804 may determine the third time allocation based on the second time allocation indicated in frame 1812. For example, where frame 1812 is an MU-RTS trigger frame and the second time allocation is indicated in a respective user info field of a user info list field of frame 1812, AP 1804 may determine the third time allocation using the contents (e.g., association identifier, RU allocation, allocation duration, etc.) of the respective user info field indicating the second time allocation.

[0174] In another embodiment, AP 1804 may construct frame 1824 based on frame 1812 and frame 1818. For example, AP 1804 may determine the third duration of the third time allocation based on the second duration of the second time allocation announced in frame 1812. In an example, frame 1812 may not comprise the RU allocation for the second time allocation to AP 1806. As such, AP 1804 may determine the RU allocation for the third time allocation using the contents (e.g., association identifier, RU allocation, allocation duration, etc.) of the respective user info field indicating the first time allocation to AP 1804 in frame 1818.

[0175] In an example, the third duration (T3) of the third time allocation may be identical to or different from the second duration (T2) of the second time allocation. In an embodiment, a start time of the third time allocation is before a start time of the second time allocation. In an embodiment, an end time of the third time allocation may be earlier than an end time of the second time allocation. In another embodiment, an end time of the third time allocation may be the same as an end time of the second time allocation.

[0176] In another embodiment, frame 1824 may not comprise / indicate an allocation for AP 1806. Instead, frame 1824 may only trigger AP 1806 to begin using TXOP 1810 for communication with its associated STA(s). In an embodiment, based on receiving frame 1824, AP 1806 may begin communicating with its associated STA(s) using the same communication parameters (e.g., RU allocation, allocation duration, etc.) as indicated in the second time allocation announced to AP 1806 in frame 1812. In other words, frame 1824 has the effect of shifting the second time allocation in time to start earlier than initially scheduled, without changing the communication parameters to be used for the second time allocation. According to this embodiment, frame 1824 may comprise a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame, for example.

[0177] On receiving frame 1824, AP 1802 may determine that AP 1804 has finished communicating before the end of the first duration and has triggered AP 1806 to start communicating during the third time allocation (T3). In an example, in response to frame 1824, AP 1802 may transmit a frame 1825 to AP 1804. In an example, frame 1825 may comprise a response frame. In an example, where frame 1824 is an MRTT frame, frame 1825 may be a CTS frame. In another example, AP 1802 may not transmit a frame in response to frame 1824.

[0178] On receiving frame 1824, AP 1806 may determine that AP 1804 has finished communicating before the end of the first duration and that AP 1806 is to start communicating with its associated STA(s) during the third time allocation (T3). In an embodiment, AP 1806 may transmit a frame 1826 to AP 1804 in response to frame 1824. In an example, frame 1826 may comprise a response frame. In an example, where frame 1824 is an MRTT frame, frame 1826 may be a CTS frame. After transmitting frame 1826, AP 1806 may communicate with its associated STA(s) during a time period 1828 of the third time allocation allocated to AP 1806. In an example, during time period 1828, AP 1806 may transmit downlink frames to one or more of its associated STAs and / or may trigger one or more of its associated STAs to transmit uplink frames to AP 1806.In example 1800, AP 1806 may finish communicating with its associated STA(s) by the end of the third duration (T3) of the third time allocation allocated to AP 1806.

[0179] In an example, being the TXOP holder, AP 1802 may regain control of the TXOP a SIPS after the end of the third duration (T3). In another example, being the TXOP holder, AP 1802 may regain control of the TXOP a point coordination function (POP) IFS (PIFS) after the end of the third duration (T3). As such, AP 1802 may transmit a frame 1830 a SIPS or a PIFS after the end of the third duration (T3). In an example, frame 1830 may comprise a control frame, a management frame, a data frame or an action frame. After regaining control of the TXOP, in an example, AP 1802 may communicate with one or more associated STAs and / or re-share the TXOP with other shared APs.

[0180] As illustrated in example 1800, based on AP 1804 being configured to (or instructed to) transmit frame 1824 to AP 1806 to trigger AP 1806 to start communicating during the first time allocation allocated to AP 1804, AP 1806 may begin using TXOP 1810 earlier than initially scheduled when AP 1804 finishes communicating before an end of the first time allocation initially allocated to AP 1804. Utilization of channel resources is thereby improved.

[0181] FIG. 19 illustrates an example process 1900 according to an embodiment. Example process 1900 is provided for the purpose of illustration only and is not limiting. Example process 1900 may be performed by a first AP, such as AP 1704 or AP 1804, for example.

[0182] As shown in FIG. 19, process 1900 includes, in step 1910, receiving, by the first AP from a second AP, during a TXOP obtained by the second AP, a first frame indicating: a first time allocation, within the TXOP, to the first AP, and a second time allocation, within the TXOP, to a third AP. Process 1900 further includes, in step 1920, transmitting, by the first AP to the third AP, a second frame that triggers the third AP to start communicating during the first time allocation.

[0183] In an embodiment, the first frame allocates the first time allocation to the first AP and the second time allocation to the third AP. In an embodiment, the first frame comprises a TXOP allocation frame. In an embodiment, the first frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

[0184] In an embodiment, process 1900 further comprises receiving, by the first AP from the second AP, a third frame announcing the first time allocation and the second time allocation. In an embodiment, the receiving of the third frame is before the receiving of the first frame. In an embodiment, the third frame comprises a schedule announcement frame. In an embodiment, the third frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

[0185] In another embodiment, the first frame announces the first time allocation and the second time allocation. In an embodiment, the first frame comprises a schedule announcement frame. In an embodiment, the first frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

[0186] In an embodiment, process 1900 further comprises receiving, by the first AP from the second AP, a third frame comprising / indicating the first time allocation. In an embodiment, the third frame comprises a TXOP allocation frame. In an embodiment, the third frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

[0187] In an embodiment, the second frame indicates a third time allocation, within the TXOP, to the third AP. In an embodiment, where the first frame allocates the first time allocation to the first AP and the second time allocation to the third AP, the second frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame. In another embodiment, where the first frame allocates the first time allocation to the first AP and the second time allocation to the third AP, the second frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame. In an embodiment, a start time of the third time allocation is before a start time of the second time allocation.

[0188] In another embodiment, where the first frame announces the first time allocation and the second time allocation, the second frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame. In an embodiment, the MRTT frame comprises the third time allocation. In an embodiment, a start time of the third time allocation is before a start time of the second time allocation.

[0189] In an embodiment, the transmitting of the second frame in step 1920 is based on the second time allocation being after (consecutive / successive to / immediately after / the next allocation after) the first time allocation. In an embodiment, the transmitting of the second frame in step 1920 is based on the first AP finishing communicating before an end of the first time allocation.

[0190] In an embodiment, process 1900 further comprises receiving, by the first AP from the second AP, an indication that the first AP is to transmit the second frame to the third AP. In an embodiment, the indication is provided in the first frame. In another embodiment, the indication is provided in a fourth frame. In an embodiment, the fourth frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame. In an embodiment, where the indication is provided in the fourth frame, process 1900 further comprises receiving of the fourth frame before receiving the first frame.

[0191] FIG. 20 illustrates another example process 2000 according to an embodiment. Example process 2000 is provided for the purpose of illustration only and is not limiting. Example process 2000 may be performed by a first AP, such as AP 1706 or AP 1806, for example.

[0192] As shown in FIG. 20, process 2000 includes, in step 2010, receiving, by the first AP from a second AP, during a TXOP obtained by the second AP, a first frame indicating: a first time allocation, within the TXOP, to a third AP, and a second time allocation, within the TXOP, to the first AP. Process 2000 further includes, in step 2020, receiving, by the first AP from the third AP, a second frame that triggers the first AP to start communicating during the first time allocation.

[0193] In an embodiment, the first frame allocates the first time allocation to the third AP and the second time allocation to the first AP. In an embodiment, the first frame comprises a TXOP allocation frame. In an embodiment, the first frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

[0194] In an embodiment, process 2000 further comprises receiving, by the first AP from the second AP, a third frame announcing the first time allocation and the second time allocation. In an embodiment, the receiving of the third frame is before the receiving of the first frame. In an embodiment, the third frame comprises a schedule announcement frame. In an embodiment, the third frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

[0195] In another embodiment, the first frame announces the first time allocation and the second time allocation. In an embodiment, the first frame comprises a schedule announcement frame. In an embodiment, the first frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

[0196] In an embodiment, the second frame indicates a third time allocation, within the TXOP, to the first AP. In an embodiment, where the first frame allocates the first time allocation to the third AP and the second time allocation to the first AP, the second frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame. In another embodiment, where the first frame allocates the first time allocation to the third AP and the second time allocation to the first AP, the second frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame. In an embodiment, a start time of the third time allocation is before a start time of the second time allocation.

[0197] In another embodiment, where the first frame announces the first time allocation and the second time allocation, the second frame comprising a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame. In an embodiment, the MRTT frame comprises the third time allocation. In an embodiment, a start time of the third time allocation is before a start time of the second time allocation.

[0198] In an embodiment, the receiving of the second frame in step 2020 is based on the second time allocation being after (consecutive / successive to / immediately after / the next allocation after) the first time allocation. In an embodiment, the receiving of the second frame in step 2020 is based on the third AP finishing communicating before an end of the first time allocation.

[0199] In an embodiment, process 2000 further comprises receiving, by the first AP from the second AP, an indication that the third AP is to transmit the second frame to the first AP. In an embodiment, the indication is provided in the first frame. In another embodiment, the indication is provided in a fourth frame. In an embodiment, the fourth frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame. In an embodiment, where the indication is provided in the fourth frame, process 2000 further comprising receiving of the fourth frame before the receiving the first frame.

[0200] FIG. 21 illustrates another example process 2100 according to an embodiment. Example process 2100 is provided for the purpose of illustration only and is not limiting. Example process 2100 may be performed by a first AP, such as AP 1702 or AP 1802, for example.

[0201] As shown in FIG. 21 , process 2100 includes, in step 2110, transmitting, by the first AP, a first frame comprising an indication that a second AP is to transmit a second frame to a third AP based on the second AP finishing communicating before an end of a first time allocation to the second AP. In an embodiment, the second frame triggers the third AP to start communicating during the first time allocation.

[0202] In an embodiment, where the first time allocation is within a TXOP obtained by the first AP, the first frame allocates the first time allocation to the second AP and a second time allocation, within the TXOP, to the third AP. In an embodiment, the first frame comprises a TXOP allocation frame. In an embodiment, the first frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

[0203] In an embodiment, process 2100 further comprises transmitting, by the first AP, a third frame announcing the first time allocation and the second time allocation. In an embodiment, the transmitting of the third frame is before the transmitting of the first frame. In an embodiment, the third frame comprises a schedule announcement frame. In an embodiment, the third frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

[0204] In another embodiment, where the first time allocation is within a TXOP obtained by the first AP, the first frame announces the first time allocation and a second time allocation, within the TXOP, to the third AP. In an embodiment, the first frame comprises a schedule announcement frame. In an embodiment, the first frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

[0205] In an embodiment, process 2100 further comprises transmitting, by the first AP to the second AP, a third frame comprising / indicating the first time allocation. In an embodiment, the third frame comprises a TXOP allocation frame. In an embodiment, the third frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

[0206] In an embodiment, the first frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame. In an embodiment, process 2100 further comprises transmitting, by the first AP, a third frame announcing the first time allocation and a second time allocation, within the TXOP, to the third AP. In an embodiment, the third frame comprises a schedule announcement frame. In an embodiment, the third frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

[0207] In an embodiment, process 2100 further comprises transmitting, by the first AP, a fourth frame allocating the first time allocation to the second AP and the second time allocation to the third AP. In an embodiment, process 2100 further comprises transmitting, by the first AP to the second AP, a fourth frame allocating the first time allocation. In an embodiment, the fourth frame comprises a TXOP allocation frame.In an embodiment, the first frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

Claims

CLAIMSWhat is claimed is:

1. A method, comprising: receiving, by a first access point (AP) from a second AP, during a transmission opportunity (TXOP) obtained by the second AP, a first frame polling: the first AP regarding receiving a first time allocation within the TXOP; and a third AP regarding receiving a second time allocation within the TXOP; transmitting, by the first AP to the second AP, a second frame in response to the first frame, wherein the transmitting of the second frame indicates that the first AP wishes to receive the first time allocation; receiving, by the first AP from the second AP, a third frame allocating the first time allocation to the first AP; transmitting, by the first AP to the second AP, a clear to send (CTS) frame in response to the third frame; and transmitting, by the first AP to the second AP, a fourth frame during the first time allocation, based on the first AP finishing communicating before an end of the first time allocation, wherein the fourth frame comprises a TXOP return frame.

2. A method, comprising: receiving, by a first access point (AP) from a second AP, during a transmission opportunity (TXOP) obtained by the second AP, a first frame indicating: a first time allocation, within the TXOP, to the first AP; and a second time allocation, within the TXOP, to a third AP; and transmitting, by the first AP to the third AP, a second frame that triggers the third AP to start communicating during the first time allocation.

3. The method of claim 2, wherein the first frame allocates the first time allocation to the first AP and the second time allocation to the third AP.

4. The method of any of claims 2-3, wherein the first frame comprises a TXOP allocation frame.

5. The method of claim 4, wherein the first frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

6. The method of any of claims 2-5, further comprising receiving, by the first AP from the second AP, a third frame announcing the first time allocation and the second time allocation.

7. The method of claim 6, wherein the receiving of the third frame is before the receiving of the first frame.

8. The method of any of claims 6-7, wherein the third frame comprises a schedule announcement frame.

9. The method of claim 8, wherein the third frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

10. The method of claim 2, wherein the first frame announces the first time allocation and the second time allocation.

11. The method of any of claims 2 or 10, wherein the first frame comprises a schedule announcement frame.

12. The method of claim 11 , wherein the first frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

13. The method of any of claims 2 or 10-12, further comprising receiving, by the first AP from the second AP, a third frame comprising / indicating the first time allocation.

14. The method of claim 13, wherein the third frame comprises a TXOP allocation frame.

15. The method of claim 14, wherein the third frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

16. The method of any of claims 2-15, wherein the second frame indicates a third time allocation, within the TXOP, to the third AP.

17. The method of claim 16, wherein the first frame allocates the first time allocation to the first AP and the second time allocation to the third AP.

18. The method of claim 17, wherein the second frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

19. The method of claim 17, wherein the second frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame.

20. The method of any of claims 16-19, wherein a start time of the third time allocation is before a start time of the second time allocation21. The method of claim 16, wherein the first frame announces the first time allocation and the second time allocation, the second frame comprising a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

22. The method of claim 21 , wherein the MRTT frame comprises the third time allocation.

23. The method of any of claims 16 or 21 -22, wherein a start time of the third time allocation is before a start time of the second time allocation.

24. The method of any of claims 2-23, wherein the transmitting of the second frame is based on the second time allocation being after (consecutive / successive to / immediately after / the next allocation after) the first time allocation.

25. The method of any of claims 2-24, wherein the transmitting of the second frame is based on the first AP finishing communicating before an end of the first time allocation.

26. The method of any of claims 2-25, further comprising receiving, by the first AP from the second AP, an indication that the first AP is to transmit the second frame to the third AP.

27. The method of claim 26, wherein the indication is provided in the first frame.

28. The method of claim 26, wherein the indication is provided in a fourth frame.

29. The method of claim 28, wherein the fourth frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame.

30. The method of any of claims 28-29, wherein the indication is provided in the fourth frame, the method further comprising receiving of the fourth frame before receiving the first frame.

31. A method, comprising: receiving, by a first access point (AP) from a second AP, during a transmission opportunity (TXOP) obtained by the second AP, a first frame (a schedule announcement frame) announcing: a first time allocation, within the TXOP, to a third AP; and a second time allocation, within the TXOP, to the first AP; receiving, by the first AP from the second AP, a second frame (a first MU-RTS TXS trigger frame) allocating the first time allocation to the third AP and the second time allocation to the first AP; and receiving, by the first AP from the third AP, a third frame (a second MU-RTS TXS trigger frame) that triggers the first AP to start communicating during the first time allocation, based on: the second time allocation being after (consecutive / successive to / immediately after / the next allocation after) the first time allocation; and the third AP finishing communicating before an end of the first time allocation.

32. A method, comprising: receiving, by a first access point (AP) from a second AP, during a transmission opportunity (TXOP) obtained by the second AP, a first frame indicating: a first time allocation, within the TXOP, to a third AP; and a second time allocation, within the TXOP, to the first AP; and receiving, by the first AP from the third AP, a second frame that triggers the first AP to start communicating during the first time allocation.

33. The method of claim 32, wherein the first frame allocates the first time allocation to the third AP and the second time allocation to the first AP.

34. The method of any of claims 32-33, wherein the first frame comprises a TXOP allocation frame.

35. The method of claim 34, wherein the first frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

36. The method of any of claims 32-35, further comprising receiving, by the first AP from the second AP, a third frame announcing the first time allocation and the second time allocation.

37. The method of claim 36, wherein the receiving of the third frame is before the receiving of the first frame.

38. The method of any of claims 36-37, wherein the third frame comprises a schedule announcement frame.

39. The method of claim 38, wherein the third frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

40. The method of claim 32, wherein the first frame announces the first time allocation and the second time allocation.41 . The method of any of claims 32 or 40, wherein the first frame comprises a schedule announcement frame.

42. The method of claim 41 , wherein the first frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

43. The method of any of claims 32-42, wherein the second frame indicates a third time allocation, within the TXOP, to the first AR44. The method of claim 33, wherein the first frame allocates the first time allocation to the third AP and the second time allocation to the first AP.

45. The method of claim 34, wherein the second frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

46. The method of claim 34, wherein the second frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame.

47. The method of any of claims 33-46, wherein a start time of the third time allocation is before a start time of the second time allocation.

48. The method of claim 33, wherein the first frame announces the first time allocation and the second time allocation, the second frame comprising a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

49. The method of claim 48, wherein the MRTT frame comprises the third time allocation.

50. The method of any of claims 48-49, wherein a start time of the third time allocation is before a start time of the second time allocation.51 . The method of any of claims 32-50, wherein the receiving of the second frame is based on the second time allocation being after (consecutive / successive to / immediately after / the next allocation after) the first time allocation.

52. The method of any of claims 32-51 , wherein the receiving of the second frame is based on the third AP finishing communicating before an end of the first time allocation.

53. The method of any of claims 32-52, further comprising receiving, by the first AP from the second AP, an indication that the third AP is to transmit the second frame to the first AP.

54. The method of claim 53, wherein the indication is provided in the first frame.

55. The method of claim 53, wherein the indication is provided in a fourth frame.

56. The method of claim 55, wherein the fourth frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame.

57. The method of any of claims 55-56, wherein the indication is provided in the fourth frame, the method further comprising receiving of the fourth frame before the receiving the first frame.

58. A method, comprising: transmitting, by a first access point (AP), during a transmission opportunity (TXOP) obtained by the first AP, a first frame polling: a second AP regarding receiving a first time allocation within the TXOP; and a third AP regarding receiving a second time allocation within the TXOP; receiving, by the first AP from the second AP, a second frame in response to the first frame, wherein the receiving of the second frame indicates that the second AP wishes to receive the first time allocation; transmitting, by the first AP to the second AP, a third frame allocating the first time allocation to the second AP; receiving, by the first AP from the second AP, a clear to send (CTS) frame in response to the third frame; and receiving, by the first AP from the second AP, a fourth frame during the first time allocation, based on the second AP finishing communicating before an end of the first time allocation, wherein the fourth frame comprises a TXOP return frame.

59. A method, comprising: transmitting, by a first access point (AP), a first frame comprising an indication that a second AP is to transmit a second frame to a third AP based on the second AP finishing communicating before an end of a first time allocation to the second AP, wherein the second frame triggers the third AP to start communicating during the first time allocation.

60. The method of claim 59, wherein the first time allocation is within a transmission opportunity (TXOP) obtained by the first AP, and wherein the first frame allocates the first time allocation to the second AP and a second time allocation, within the TXOP, to the third AP.61 . The method of any of claims 59-60, wherein the first frame comprises a TXOP allocation frame.

62. The method of claim 61 , wherein the first frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

63. The method of any of claims 60-62, further comprising transmitting, by the first AP, a third frame announcing the first time allocation and the second time allocation.

64. The method of claim 63, wherein the transmitting of the third frame is before the transmitting of the first frame.

65. The method of any of claims 63-64, wherein the third frame comprises a schedule announcement frame.

66. The method of claim 65, wherein the third frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

67. The method of claim 59, wherein the first time allocation is within a transmission opportunity (TXOP) obtained by the first AP, and wherein the first frame announces the first time allocation and a second time allocation, within the TXOP, to the third AP.

68. The method of any of claims 59 or 67, wherein the first frame comprises a schedule announcement frame.

69. The method of claim 68, wherein the first frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

70. The method of any of claims 67-69, further comprising transmitting, by the first AP to the second AP, a third frame comprising / indicating the first time allocation.

71. The method of claim 70, wherein the third frame comprises a TXOP allocation frame.

72. The method of claim 71 , wherein the third frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

73. The method of claim 59, wherein the first frame comprises a quality of service (QoS) data frame, a QoS null frame, an action frame, a control frame, or a management frame.

74. The method of any of claims 59 or 73, further comprising transmitting, by the first AP, a third frame announcing the first time allocation and a second time allocation, within the TXOP, to the third AP.

75. The method of claim 74, wherein the third frame comprises a schedule announcement frame.

76. The method of claim 75, wherein the third frame comprises a multi-user request-to-send (MU-RTS) trigger frame.

77. The method of any of claims 74-76, further comprising transmitting, by the first AP, a fourth frame allocating the first time allocation to the second AP and the second time allocation to the third AP.

78. The method of any of claims 74-76, further comprising transmitting, by the first AP to the second AP, a fourth frame allocating the first time allocation.

79. The method of any of claims 77-78, wherein the fourth frame comprises a TXOP allocation frame.

80. The method of claim 79, wherein the first frame comprises a multi-user request-to-send triggered TXOP sharing (MU-RTS TXS) trigger (MRTT) frame.

81. 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 -80.

82. 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- 80.

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