Multi-access point coordination per TXOP frame sequence using per-station feedback scheduling

Abstract

Technical solutions relate to multiple access point coordination per TXOP frame sequence using per-station feedback scheduling. A first access point (AP) may transmit a first message to a second AP and a first set of candidate stations to initiate transmission opportunity (TXOP) and CBF requests. The second AP may transmit a second message with a CBF response to a second set of candidate stations of the second AP identified as participating in the TXOP in response to the CBF request. The first AP may transmit a third message with a CBF trigger to the second AP in response to receiving the CBF response, the CBF trigger including information for synchronizing CBF transmissions to be communicated during the TXOP.

Description

[0001] Cross - reference to related patent applications

[0002] This application claims the benefit and priority of U.S. Provisional Application No. 63 / 689,021, filed on Aug. 30, 2024, and Indian Provisional Application No. 202421502187, filed on Jan. 11, 2024, the entire contents of both applications are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure generally relates to systems and methods for wireless communication between an access point and a wireless communication device, including but not limited to communication that reduces interference to an unintended communication device. BACKGROUND OF THE DISCLOSURE

[0004] An access point (AP) (e.g., a Wi-Fi router) can facilitate wireless communication with any number of client wireless communication devices (also referred to as clients, stations, or STAs). These clients, stations, or STAs can include smartphones, tablet computers, and computers that are within the wireless communication range of the AP. Sometimes, a client can experience interference caused by the AP (e.g., within the same or a different wireless communication network) transmitting data to other clients or STAs. Such interference can be exacerbated when network density increases and transmission opportunities decrease. SUMMARY OF THE DISCLOSURE

[0005] The technical solution of the present disclosure relates to systems and methods for establishing coordinated beamforming (CBF) for each transmission opportunity (TXOP) frame sequence, where a CBF transmission schedule can be established before feedback data from participating station devices. When multiple base stations (BSs) or access points (APs) implement CBF while transmitting data to a user device or user equipment, the lack of a trigger frame from participating APs before the initial CBF physical protocol data unit (PPDU) transmission can make it difficult to coordinate or synchronize the start of CBF communication. In addition, the AP's inability to consider changing the parameters or availability of all AP and station device participants makes it more challenging to accurately and efficiently establish CBF communication. In such a case, there is a risk that one of the APs will start the CBF PPDU earlier or later than the other APs, resulting in synchronization problems between the APs, or the performance of some of the participants will be less than expected. These problems can lead to timing mismatches, which ultimately result in phase misalignment and reduced beamforming efficiency. Synchronization problems can further lead to different oscillator frequencies at different APs, resulting in phase and amplitude errors. The technical solution can overcome these challenges by utilizing a CBF-TXOP frame sequence to synchronize the APs and / or stations when using feedback data from participating devices for CBF PPDU transmission.

[0006] At least one aspect of the technical solution relates to a system. The system may include a first access point (AP), which may be configured, for example, via instructions or data stored in a memory for access and execution by one or more processors of the first AP. The first AP may be configured to transmit a first message to a second AP capable of participating in coordinated beamforming (CBF) and a first set of candidate stations of the first AP to initiate a transmission opportunity (TXOP) with an embedded CBF request. The second AP is configured to transmit a second message to the first AP and a second set of candidate stations of the second AP identified as participating in the TXOP with an embedded CBF response in response to the CBF request. The first AP transmits a third message with a CBF trigger to the second AP in response to receiving the CBF response that the second AP will participate in CBF, the CBF trigger including information for synchronizing CBF transmissions to be communicated during the TXOP.

[0007] The first AP may be configured to include in the CBF request a list of identifiers of the first set of candidate stations participating in CBF and information about the proposed number of spatial streams in the CBF transmissions for each station in the first set of candidate stations. The CBF response of the second AP may include a list of identifiers of the second set of candidate stations participating in CBF and the proposed number of spatial streams in the CBF transmissions for each station in the second set of candidate stations for the first AP to determine a schedule for the CBF transmissions.

[0008] The first AP may be configured to receive, in response to the first message, information about the availability of participating in the TXOP from the first set of candidate stations and information about the duration of the availability in the TXOP of the first set of candidate stations. The first AP may be configured to determine at least one of the following based on the information about availability and the information about duration: the ability of the first AP to participate in CBF during the TXOP, a first set of stations from the first set of candidate stations of the first AP participating in CBF during the TXOP, or the maximum duration for the first AP to participate in CBF during the TXOP. The first message may include an indication of at least one of the following in the third message information: the ability of the first AP to participate in CBF during the TXOP, the first set of stations of the first AP participating in CBF during the TXOP, or the maximum duration for the first AP to participate in CBF during the TXOP.

[0009] The first AP may include padding in the first message to provide a time interval for at least one of the second AP or the at least one station to process the information included in the first message before generating one or more responses regarding the availability of at least one of the second AP or the first set of candidate stations to participate in CBF. The second AP is configured to transmit a preliminary CBF response indicating the participation of the second AP to the first access point before receiving information regarding the availability of the second set of candidate stations. The first AP may determine a schedule for transmitting data of one or more stations in the first set of candidate stations during the TXOP before receiving information regarding the availability of the second set of candidate stations. After receiving the CBF response from the second AP, the first AP may adjust the schedule in response to a message transmitted by the second AP, the message including the information regarding the second set of candidate stations.

[0010] At least one aspect of the technical solution relates to a system. The system may include a first access point (AP), which may be configured, for example, via instructions or data stored in a memory and accessible and executable by one or more processors of the first AP. The first AP may be configured to transmit a first message to a second AP capable of participating in coordinated beamforming (CBF) and a first set of candidate stations of the first AP to initiate a transmission opportunity (TXOP) with an embedded CBF request. The first AP may be configured to receive, in response to the first message, one or more indications from the first set of candidate stations, the indications corresponding to the availability of one or more first stations in the first set of candidate stations to participate in the TXOP. The first AP may be configured to transmit an adjusted first message to the second AP in response to the one or more indications to initiate the TXOP according to an embedded adjusted CBF request. The first AP may be configured to receive a second message from the second AP in response to the first AP not terminating the TXOP via the adjusted first message, the second message including an adjusted CBF response to the adjusted first message. The second message may include information regarding a second set of candidate stations of the second AP. The first AP may be configured to transmit a third message with a CBF trigger to the second AP in response to the second AP indicating participation in the TXOP via the second message, the CBF trigger including information for synchronizing CBF transmissions to be conveyed during the TXOP.

[0011] The first AP may be configured to determine, based on the one or more indications, that a first subset of the one or more first stations is not available to participate in the TXOP, and that a second subset of the one or more first stations is available to participate in the TXOP. The first AP may be configured to generate an adjusted CBF request in response to the determination, the adjusted CBF request indicating the second subset of the one or more first stations as participating in the TXOP. The one or more indicators may be received via at least one of a Trigger-based Physical Protocol Data Unit (TB-PPDU) format or a non-High Throughput Duplicate (non-HT DUP) format. The first AP may be configured to receive the one or more indications of the one or more durations of availability of the one or more first stations. The first AP may be configured to determine the availability of the one or more first stations based on the one or more durations.

[0012] One aspect of the technical solution relates to a method. The method may include transmitting, by a first Access Point (AP), a first message to a second AP capable of participating in Coordinated Beamforming (CBF) and a first set of candidate stations of the first AP to initiate a Transmission Opportunity (TXOP) with an embedded CBF request. The method may include transmitting, by the second AP in response to the CBF request, a second message to the first AP and a second set of candidate stations of the second AP identified as participating in the TXOP with an embedded CBF response. The method may include transmitting, by the first AP in response to receiving the CBF response that the second AP will participate in the CBF, a third message to the second AP with a CBF trigger, the CBF trigger including information for synchronizing CBF transmissions to be conveyed during the TXOP.

[0013] The method may include inserting or including, by the first AP in the CBF request, a list of identifiers of the first set of candidate stations for participating in the CBF and information about the proposed number of spatial streams in the CBF transmissions for each station in the first set of candidate stations. The method may include inserting or including, by the second AP within the CBF response from the second AP, a list of identifiers of the second set of candidate stations for participating in the CBF and the proposed number of spatial streams in the CBF transmissions for each station in the second set of candidate stations. The method may include the first AP determining a schedule for the CBF transmissions.

[0014] The method may include the first AP receiving, in response to the first message, information about the availability of participating in the TXOP from one or more stations in the first set of candidate stations or information about the duration of the availability in the TXOP of the one or more stations in the first set of candidate stations. The method may include the first AP determining, based on the information about the availability or the information about the duration, at least one of the following: the ability of the first AP to participate in CBF during the TXOP, a first set of stations from the first set of candidate stations of the first AP that participate in CBF during the TXOP, or the maximum duration for which the first AP participates in CBF during the TXOP. The method may include the first AP including an indication of at least one of the following in the third message: the ability of the first AP to participate in CBF during the TXOP, the first set of stations of the first AP that participate in CBF during the TXOP, or the maximum duration for which the first AP participates in CBF during the TXOP. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Various objects, aspects, features, and advantages of the present disclosure will become more apparent and better understood by reference to the detailed description taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements.

[0016] Figure 1A is a block diagram depicting a network environment including one or more access points communicating with one or more devices or stations according to some embodiments.

[0017] Figure 1B and 1C is a block diagram depicting a computing device that may be used in conjunction with the methods and systems described herein according to some embodiments.

[0018] Figure 2 Illustrates an example system of coordinated partial rank nulling in a multi-AP and multi-STA environment according to some embodiments.

[0019] Figure 3 is an example plot of the signal space of STA transmissions in the context of single-AP partial rank nulling.

[0020] Figure 4 is an example plot of two signal spaces of two STA transmissions in the context of 2-AP coordinated partial rank nulling.

[0021] Figure 5 is an example block diagram of a system for multi-access point coordination for each CBF TXOP frame sequence.

[0022] Figure 6 An example flowchart of a method for multi - access point coordination for each CBF TXOP frame sequence.

[0023] Figure 7 An example flowchart of a second method for multi - access point coordination for each CBF TXOP frame sequence.

[0024] Details of various embodiments of the method and system are set forth in the accompanying drawings and the description below. DETAILED DESCRIPTION

[0025] The following IEEE standards (including any draft versions of these standards) are hereby incorporated by reference in their entirety and made a part of this disclosure for all purposes: Wi - Fi Alliance standards and IEEE 802.11 standards, including (but not limited to) IEEE 802.11a TM , IEEE 802.11b TM , IEEE 802.11g TM , IEEE P802.11n TM ; IEEE P802.11ac TM ; and IEEE P802.11be TM draft version D3.0 standard. Although aspects of these standards may be referenced in this disclosure, the disclosure is in no way limited by these standards.

[0026] For the purpose of reading the following description of various embodiments, the following description of the sections of the specification and their corresponding content may be helpful:

[0027] - Section A describes the network environment and computing environment that can be used to practice the embodiments described herein; and

[0028] - Section B describes multi - access point coordination for each CBF TXOP frame sequence using per - station feedback scheduling.

[0029] A. Computing and network environment

[0030] Before discussing the specific embodiments of the solution, it may be helpful to describe aspects of the operating environment and associated system components (e.g., hardware elements) in the context of the methods and systems described herein.

[0031] Reference Figure 1A, depicting an embodiment of a network environment. Briefly summarized, the network environment includes a wireless communication system, which includes one or more access points (APs) or network devices 205, one or more stations (also referred to as STAs) or wireless communication devices 240, and network hardware components or network hardware 192. The wireless communication device or STA 240 can include, for example, a laptop computer, a tablet computer, a personal computer, and / or a cellular phone device. Reference can be made to Figure 1B and 1C to describe in more detail the details of the embodiments of each station or wireless communication device 240 and AP or network device 205 (such as its internal hardware and software configuration). In one embodiment, the network environment can be an ad hoc network environment, an infrastructure wireless network environment, a subnet environment, etc. The network device 205 or AP can be operatively coupled to the network hardware 192 via a local area network connection. The network device 205 or AP can include, for example, a Wi-Fi device providing a WLAN, or a 5G base station for providing a cellular network. The network hardware 192, which can include routers, gateways, switches, bridges, modems, system controllers, appliances, etc., can provide a local area network connection for the communication system. Each of the network devices 205 or APs can have an associated antenna or antenna array to communicate with wireless communication devices in its area. The wireless communication device 240 can register with a specific network device 205 or AP to receive services from the communication system (e.g., via SU-MIMO or MU-MIMO configurations). For direct connections (e.g., peer-to-peer communication), some wireless communication devices can communicate directly via an allocated channel and communication protocol. Some of the wireless communication devices 240 can be mobile or relatively stationary with respect to the network device 205 or AP.

[0032] In some embodiments, the network device 205 or AP includes a device or module (including a combination of hardware and software) that allows a wireless communication device 240 to connect to a wired network using Wi-Fi or other standards. The network device 205 or AP may sometimes be referred to as a wireless access point (WAP). The network device 205 or AP may be implemented (e.g., configured, designed, and / or built) to operate in a wireless local area network (WLAN). In some embodiments, the network device 205 or AP may be connected to a router as a stand-alone device (e.g., via a wired network). In other embodiments, the network device 205 or AP may be a component of a router. The network device 205 or AP may provide access to the network for multiple devices. The network device 205 or AP may, for example, be connected to a wired Ethernet connection and use a radio frequency link to provide a wireless connection for other devices 240 to utilize the wired connection. The network device 205 or AP may be implemented to support standards for sending and receiving data using one or more radio frequencies. Those standards and the frequencies they use may be defined by the IEEE (e.g., the IEEE 802.11 standards). The network device 205 or AP may be configured and / or used to support a public Internet hotspot and / or to extend the range of a Wi-Fi signal on a network.

[0033] In some embodiments, the access point or network device 205 may be used in a wireless network (e.g., IEEE 802.11, Bluetooth, ZigBee, any other type of radio frequency-based network protocol, and / or variants thereof) (e.g., within a home, vehicle, or building). Each of the wireless communication devices 240 may include a built-in radio and / or be coupled to a radio. Such wireless communication devices 240 and / or the access point or network device 205 may operate in accordance with various aspects of the present disclosure presented herein to enhance performance, reduce cost and / or size, and / or enhance broadband applications. Each wireless communication device 240 may have the ability to act as a client node seeking access to resources (e.g., data and connections to networked nodes such as servers) via one or more access points or network devices 205.

[0034] The network connection may include any type and / or form of network and may include any of the following: a point-to-point network, a broadcast network, a telecommunications network, a data communication network, a computer network. The network topology may be a bus, star, or ring network topology. The network may be any such network topology known to those of ordinary skill in the art that is capable of supporting the operations described herein. In some embodiments, different types of data may be transmitted via different protocols. In other embodiments, the same type of data may be transmitted via different protocols.

[0035] The communication device 240 and the access point or network device 205 may be deployed as any type and form of computing device and / or execute on any type and form of computing device, such as a computer, network device, or appliance capable of communicating on any type and form of network and performing the operations described herein. Figure 1B and 1C FIG. depicts a block diagram of a computing device 100 that may be used to practice embodiments of the wireless communication device 240 or the network device 205. As Figure 1B and 1C shown, each computing device 100 includes a processor 121 (e.g., a central processing unit) and a main memory unit 122. As Figure 1B shown, the computing device 100 may include a storage device 128, an installation device 116, a network interface 118, an I / O controller 123, display devices 124a to 124n, a keyboard 126, and a pointing device 127 (e.g., a mouse). The storage device 128 may include an operating system and / or software. As Figure 1C shown, each computing device 100 may also include additional optional elements that communicate with the central processing unit or processor 121, such as a memory port 103, a bridge 170, one or more input / output devices 130a to 130n, and a cache memory 140.

[0036] The central processing unit or processor 121 is any logic circuitry that responds to and processes instructions fetched from the main memory unit 122. In many embodiments, the central processing unit or processor 121 is provided by a microprocessor unit, such as: a microprocessor unit manufactured by Intel Corporation of Santa Clara, California; a microprocessor unit manufactured by International Business Machines of White Plains, New York; or a microprocessor unit manufactured by Advanced Micro Devices of Sunnyvale, California. The computing device 100 may be based on any of these processors or any other processor capable of operating as described herein.

[0037] The main memory unit 122 may be one or more memory chips capable of storing data and allowing any storage location to be directly accessed by the microprocessor or processor 121, such as any type or variant of static random access memory (SRAM), dynamic random access memory (DRAM), ferroelectric RAM (FRAM), NAND flash memory, NOR flash memory, and solid state drives (SSDs). The main memory unit 122 may be based on any of the above memory chips, or any other available memory chip capable of operating as described herein. In Figure 1B the illustrated embodiment, the processor 121 communicates with the main memory unit 122 via a system bus 150 (described in more detail below). Figure 1C An embodiment of the computing device 100 is depicted where the processor communicates directly with the main memory unit 122 via a memory port 103. For example, in Figure 1C this case, the main memory unit 122 may be DRDRAM.

[0038] Figure 1C An embodiment is depicted where the main processor 121 communicates directly with the cache memory 140 via a secondary bus (sometimes referred to as a backside bus). In other embodiments, the main processor 121 uses the system bus 150 to communicate with the cache memory 140. The cache memory 140 typically has a faster response time than the main memory unit 122 and is provided by, for example, SRAM, BSRAM, or EDRAM. In Figure 1C the illustrated embodiment, the processor 121 communicates with various I / O devices 130 via a local system bus 150. Various buses may be used to connect the central processing unit or processor 121 to any of the I / O devices 130, such as, for example, the VESA VL bus, ISA bus, EISA bus, Micro Channel Architecture (MCA) bus, PCI bus, PCI-X bus, PCI-Express bus, or NuBus. For embodiments where the I / O device is a video display 124, the processor 121 may use the Advanced Graphics Port (AGP) to communicate with the display 124. Figure 1C An embodiment of a computer or computer system 100 is depicted where the main processor 121 may communicate directly with the I / O device 130b, for example, via communication technologies such as HYPERTRANSPORT, RAPIDIO, or INFINIBAND. Figure 1C An embodiment is also depicted where a hybrid of local bus and direct communication is used: the processor 121 uses a local interconnect bus to communicate with the I / O device 130a while communicating directly with the I / O device 130b.

[0039] A variety of I / O devices 130a through 130n may be present in computing device 100. Input devices include keyboards, mice, trackpads, trackballs, microphones, dials, touchpads, touchscreens, and digitizing tablets. Output devices include video displays, speakers, inkjet printers, laser printers, projectors, and thermal dye sublimation printers. As Figure 1B shown, the I / O devices may be controlled by I / O controller 123. The I / O controller may control one or more I / O devices, such as keyboard 126 and pointing device 127, such as a mouse or an optical pen. Additionally, the I / O devices may also provide storage and / or installation media for computing device 100. In yet other embodiments, computing device 100 may provide a USB connection (not shown) to accommodate a handheld USB storage device, such as a USB flash drive series of devices manufactured by Twintech Industry, Inc. of Los Alamitos, California.

[0040] Referring again to Figure 1B , computing device 100 may support any suitable installation device 116, such as a disk drive, CD-ROM drive, CD-R / RW drive, DVD-ROM drive, flash drive, tape drives in various formats, USB devices, hard disk drives, network interfaces, or any other device suitable for installing software and programs. Computing device 100 may further include storage devices, such as one or more hard disk drives or redundant arrays of independent disks, for storing an operating system and other related software and for storing application software programs (e.g., any program or software 120 for implementing (e.g., configured and / or designed for) the systems and methods described herein). Optionally, any of the installation devices 116 may also be used as a storage device. Additionally, the operating system and software may run from a bootable medium.

[0041] In addition, computing device 100 may include a network interface 118 to interface to a network through various connections, including (but not limited to) standard telephone lines, LAN or WAN links (such as 802.11, T1, T3, 56kb, X.25, SNA, DECNET), broadband connections (such as ISDN, frame relay, ATM, gigabit Ethernet, Ethernet-over-SONET), wireless connections, or some combination of any or all of the above connections. A variety of communication protocols (e.g., TCP / IP, IPX, SPX, NetBIOS, Ethernet, ARCNET, SONET, SDH, Fiber Distributed Data Interface (FDDI), RS232, IEEE 802.11, IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, IEEE 802.11ac, IEEE 802.11ad, CDMA, GSM, WiMax, and direct asynchronous connection) may be used to establish the connection. In one embodiment, computing device 100 communicates with other computing devices 100' via any type and / or form of gateway or tunneling protocol (such as Secure Sockets Layer (SSL) or Transport Layer Security (TLS)). Network interface 118 may include a built-in network adapter, network interface card, PCMCIA network card, card bus network adapter, wireless network adapter, USB network adapter, modem, or any other device suitable for interfacing computing device 100 to any type of network capable of communicating and performing the operations described herein.

[0042] In some embodiments, computing device 100 may include or be coupled to one or more display devices 124a through 124n. Accordingly, any one of I / O devices 130a through 130n and / or I / O controller 123 may include any type and / or form of suitable hardware, software, or a combination of hardware and software to support, enable, or provide the connection and use of (a) display device(s) 124a through 124n by computing device 100. For example, computing device 100 may include any type and / or form of video adapter, video card, driver, and / or library to interface, communicate, connect, or otherwise use (a) display device(s) 124a through 124n. In one embodiment, the video adapter may include multiple connectors to interface to (a) display device(s) 124a through 124n. In other embodiments, computing device 100 may include multiple video adapters, where each video adapter is connected to (a) display device(s) 124a through 124n. In some embodiments, any portion of the operating system of computing device 100 may be configured to use multiple display devices 124a through 124n. In additional embodiments, I / O device 130 may be a bridge between system bus 150 and an external communication bus, such as a USB bus, Apple Desktop bus, RS-232 serial connection, SCSI bus, FireWire bus, FireWire 800 bus, Ethernet bus, AppleTalk bus, Gigabit Ethernet bus, Asynchronous Transfer Mode bus, FibreChannel bus, Fibre bus, Serial Attached Small Computer System Interface bus, USB connection, or HDMI bus).

[0043] Figure 1B and 1CThe computing device 100 of the type depicted may operate under the control of an operating system that controls the scheduling of tasks and access to system resources. The computing device 100 may run any operating system, such as any version of the MICROSOFT WINDOWS operating system, different versions of Unix and Linux operating systems, any version of MAC OS for Macintosh computers, any embedded operating system, any real-time operating system, any open-source operating system, any proprietary operating system, any operating system for mobile computing devices, or any other operating system capable of running on a computing device and performing the operations described herein. Exemplary operating systems include, but are not limited to: ANDROID, produced by Google Inc.; WINDOWS 7, 8, and 10, produced by Microsoft Corporation of Redmond, Washington; MAC OS, produced by Apple Computer of Cupertino, California; WebOS, produced by Research In Motion (RIM); OS / 2, produced by International Business Machines of Armonk, New York; and the freely available operating system Linux, released by Caldera of Salt Lake City, Utah, or any type and / or form of Unix operating system and other operating systems.

[0044] The computer system or computing device 100 may be any workstation, telephone, desktop computer, laptop or notebook computer, server, handheld computer, mobile phone or other portable telecommunications device, media player device, gaming system, mobile computing device, or any other type and / or form of computing, telecommunications, or media device capable of communicating. In some embodiments, the computing device 100 may have different processors, operating systems, and input devices consistent with the device. For example, in one embodiment, the computing device 100 is a smartphone, mobile device, tablet computer, or personal digital assistant. Additionally, the computing device 100 may be any workstation, desktop computer, laptop or notebook computer, server, handheld computer, mobile phone, any other computer, or other form of computing or telecommunications device capable of communicating and having sufficient processor power and memory capacity to perform the operations described herein.

[0045] In the context of the systems and methods disclosed herein, aspects of the operating environments and components described above will become apparent.

[0046] When an AP transmits data to a specific intended recipient STA within its own basic service set (BSS), other STAs within the same or an adjacent BSS (e.g., other WLANs) can be within the range of the transmitting AP and experience interference. Interference can include any undesired interruption or degradation of a signal, communication, or system caused by the presence of an external signal, noise, or other factor that interferes with the intended transmission or reception of information. Interference can include an unwanted signal interruption caused by the transmission from one access point (AP), affecting the communication between another AP and its associated station (STA). The CBF can mitigate such interference by adjusting the transmission mode to minimize signal overlap with unintended STA recipients. For example, when transmissions to different STAs occur simultaneously on the same channel, interference caused by the transmissions can be difficult to resolve because the information from one or more of the transmissions may be unknown and the relationship between the transmissions may be unknown. Such interference can result in latency, delay, or network packet loss, increase processing power and thus increase power consumption, reduce the optimization of beamforming networks, make data transmission within such networks more difficult, and have an adverse impact on the user experience.

[0047] The technical solution of the present disclosure overcomes these challenges by facilitating coordinated beamforming (CBF) of per transmission opportunity (TXOP) frame sequences by multiple APs. CBF can include any technique or method in which multiple APs cooperatively adjust their beamforming patterns to deliver their signals or transmissions to the intended stations while minimizing or eliminating interference from such signals or transmissions at non-intended stations. For example, APs from different BSSs (e.g., WLANs) can use CBF TXOP frame sequences to configure their transmissions to send along a vector at which interference from those APs is minimized at non-intended receiving STA, client, or user devices. The technical solution can include a client device (e.g., STA) receiving a data stream or vector from an AP of its corresponding network. The network (e.g., the WLAN of a particular AP) can include one or more basic service sets (BSSs) having an AP and one or more STAs configured for wireless communication via the same AP (e.g., via a local WLAN configured to the AP). Since an AP can transmit any number of data streams to any number of STAs within its BSS, there may be synchronization of the APs when initiating a data stream, resulting in phase misalignment that reduces beamforming efficiency. The technical solution of the present disclosure can utilize various messages to convey all information (e.g., preamble content) associated with CBF PPDU transmissions to the corresponding STAs of each AP. Thus, the technical solution of this solution allows multiple APs to communicate at the same time and frequency (e.g., transmit simultaneously on the same channel), while avoiding interference, thereby increasing the throughput of the transmission, reducing latency, and minimizing spectrum usage to avoid interference.

[0048] The technical solution of the present disclosure can include a system and method for a multi-AP CBF TXOP frame sequence. The system and method can use nulling to initially reduce interference between the AP and the STA. Nulling can include one of the candidate features considered by the next generation Wi-Fi standard (UHR, 11bn). Nulling can include any technique in which an AP minimizes the interface experienced by the STA by reducing the strength or power of unwanted signals from other sources. Nulling can include a technique in which the system can combine one signal with another signal to create a null value (e.g., cancel the original signal). Nulling can be utilized or included to minimize the AP interference seen by the STA due to transmissions from the AP to other STAs.

[0049] The CBF TXOP can be a time interval or a time window to provide at least one AP access for continuous data transmission. The CBF TXOP duration can be specified by physical layer (PHY) or media access control (MAC) layer parameters. By utilizing the CBF TXOP, the AP can minimize (e.g., reduce to below an acceptable threshold) synchronization and timing issues. For example, the CBF TXOP frame sequence can include techniques to minimize interference by improving the synchronization of CBF PPDU transmission. For example, if an AP attempts to transmit a CBF PPDU, then the AP can transmit a message to other APs, which indicates information (e.g., MCS / Nss, duration, preamble content, etc. for each STA) to align the phase of each AP before the CBF PPDU transmission. This solution can provide a mechanism or process to coordinate each AP to minimize interference at the STA while improving the timing of CBF PPDU transmission at each AP.

[0050] Now refer to Figure 2 , and illustrate an example of a system 200 for implementing coordinated nulling for multi-AP transmission. The system 200 can include one or more access points (APs) 205 (e.g., Wi-Fi routers), which provide transmission to stations or STAs 240 within their BSS 250. The AP 205 can also have a wireless transmission range 255, which can include STAs 240 outside of its BSS (e.g., STAs that are not configured to the corresponding AP's WLAN but are still able to receive transmissions or interference from these APs).

[0051] Figure 2It may include a first AP 205 and a second AP 205. The first AP 205 has a first BSS 250 including a first station 240 and a third station 240, and the second AP 205 has a second BSS 250 including a second station 240 and a fourth station 240. Each of the first and second APs 205 may include one or more coordinators 210, a communication controller 215, a nulling function 220, an antenna 225, and a spatial stream 230. Each STA 240 (e.g., the first, second, third, and fourth stations 240 in system 200) may include one or more antennas 225, a communication controller 215, a spatial stream function 235, and a spatial stream 230. In addition to the STAs 240 within its own BSS 250, each of the APs 205 may also have a wireless signal range 255, which may cover or include the STAs 240 within its own BSS 250 and the STAs 240 outside its BSS 250. For example, in addition to the first and third STAs 240, the first range 255 of the first AP 205 may also include the second STA 240 (e.g., from the BSS of the second AP 205). Similarly, in addition to the second and fourth STAs 240, the second AP 205 may also have a second signal range 255, which may include the first STA 240 (e.g., from the BSS of the first AP 205).

[0052] Figure 2 An environment can be described in which the AP 205 can coordinate its transmissions according to its pre-negotiated and configured partial rank nulling. For example, system 200 can be used to provide single-AP partial rank nulling (e.g., nulling a portion of the interference to non-receiving STAs within the BSS of the transmitting AP) and multi-AP partial rank nulling (e.g., nulling a portion of the interference to non-receiving STAs within the same or different BSSs relative to the transmitting AP).

[0053] The AP 205 can include any combination of hardware and software that allows a wireless communication device (e.g., STA 240) to wirelessly connect to a wired network or the World Wide Web or the Internet. The AP 205 can include any combination of hardware and software for facilitating wireless communication within a WLAN of the AP for any STA 240 included in its BSS 250. The AP 205 can include one or more communication devices (e.g., Wi-Fi router, switch, Bluetooth hub, cellular network base station), and can utilize any wireless communication protocol or standard (e.g., 802.11) for wireless communication.

[0054] The AP 205 and STA240 can be configured for wireless communication in a wireless communication network (such as a LAN, WAN, or cellular network). For example, each AP 205 can include, be associated with, be coupled to, provide, or facilitate a communication network (such as a WLAN of Wi-Fi) for any client or station 240 in its own basic service set (BSS).

[0055] BSS250 is a term used to identify a set of stations (such as devices) associated with the same wireless access point within a WLAN. For example, a BSS can identify a set or collection of one or more stations and / or one or more APs that communicate together within a wireless network. The BSS250 can include one or more APs within a specific coverage area (such as range 255) and client devices (such as STA240) coupled to the APs. The BSS250 can provide infrastructure for the AP 205 to provide network communication to the STA240 within its frequency coverage area. Within the BSS250, the AP 205 can manage the distribution of data to various connected devices (such as STA 240), facilitate the implementation of security protocols or functions, and roam as the STA 240 may move in and out of its coverage area (such as range 255). The range 255 can include the area where a signal from the AP 205 can reach the receiving STA 240. The range 255 can include STA 240s within the BSS250 of a given AP 205 or STA240s that are part of the BSS250 of another AP 205. For example, a first STA240 that is part of the first BSS250 of a first AP 205 but is also within the second range 255 of a second AP 205 that serves the second and fourth STA240s of a second BSS250.

[0056] The coordinator 210 can include any combination of hardware and software for coordinating communication between the AP 205 and / or STA 240. The coordinator 210 can include functions (such as applications, computer code, or programs) that facilitate the coordination of communication (such as transmission) between the AP 205 and STA 240 or among the AP 205s. The coordinator 210 can include functions for implementing a coordination phase to identify STA240s for which interference needs to be fully or partially nulled and for exchanging STA 240 information between the AP 205s. The coordinator 210 can include functions for coordinating timing and frequency (such as exchanging timing and frequency information (such as communication bands or channels) between the AP 205s). The coordinator 210 can generate, facilitate, implement, and apply settings or configurations to the AP 205 and / or STA240 to facilitate coordinated partial rank nulling.

[0057] The coordinator 210 may include a precoder function, such as a precoder algorithm for calculating beamforming vectors for each STA 240 to achieve partial rank nulling. The precoder may include a function for calculating the direction or vector for beamforming transmission to the STA 240. The precoder may include a function for: using information or data related to the direction or vector where interference at the STA 240 is minimized or reduced to a threshold below an acceptable interference level (e.g., achieving partial rank nulling) to determine the direction or vector for beamforming transmission to perform partial rank nulling at such STA 240.

[0058] The coordinator 210 may include a function for performing channel sounding on the STA 240. For example, the coordinator 210 may facilitate, indicate, or request each STA to measure one or more MIMO channels of each sounding AP and provide the measurement returns to the coordinator 210. When measuring the channels of different APs 205, the relative phase offset across the receive antennas 225 for the STA 240 may be maintained at a constant value. The coordinator 210 may exchange estimates of the MIMO channels of the sounding APs with the STA 240 (e.g., via a compressed beamforming report format (CBR) as provided in 802.11, or in Cartesian form). The coordinator 210 may exchange information about interfering APs 205 (e.g., APs 205 from an external BSS 250), such as when the STA 240 provides a linear transformation of the MIMO channel from the particular interfering AP 205. The linear transformation may be determined using a previously measured MIMO channel between the STA and its own AP 205 (e.g., the AP 205 of the STA's BSS 250). For example, the linear transformation of the MIMO channel may represent a projection on one or more eigenmodels of the MIMO channel measured between the STA and the AP 205 of its own BSS. For example, if the STA is receiving a particular number of expected spatial streams from its own AP 205 (e.g., the AP 205 from the STA's own BSS 250), then the coordinator 210 may exchange (e.g., receive) a set of directions where the AP 205 will minimize interference.

[0059] The coordinator 210 may include functionality for facilitating or performing channel sounding of the STAs 240. Channel sounding may include transmitting a signal and, in response, receiving characteristics (such as signal strength, latency, and phase), and then using such received characteristics to determine the quality of the communication channel. The coordinator 210 may transmit one or more null data packets (NDPs) (e.g., individually or jointly with APs 205 of other BSSs 250). The NDPs may be synchronized in time and / or frequency (e.g., among multiple APs 205 performing simultaneous channel sounding). The number of sounding dimensions in the NDP may include the total number of antennas across the APs. NDPs transmitted jointly may precede one or more NDP announcement (NDPA) frames. For example, an AP 205 may transmit an NDPA on behalf of all APs 205 performing channel sounding to all STAs 240 being sounded. For example, each of the APs 205 may sequentially send an NDPA to its own STAs 240. For example, all APs 205 may transmit their NDPAs simultaneously but individually in frequency (e.g., via OFDMA), where each AP 205 addresses the STAs 240 within its own BSS 250. For example, the coordinator 210 may provide or facilitate a trigger frame transmitted by the APs 205, based on which all APs 205 participating in channel sounding may synchronize their carrier frequency offsets (CFOs) and the start time of their coordinated transmissions.

[0060] The communication controller 215 may include any combination of hardware and software for implementing wireless communication between the AP 205 and the STA 240. The communication controller 215 may include functionality for providing and transmitting data (such as spatial streams) to the intended STA 240. The communication controller 215 may transmit a message to the STA 240, such as information, data, or a description asking for the direction or vector in which interference is to be minimized at each STA 240. The communication controller 215 may include functionality for configuring the transmission characteristics of the AP 205 to perform and implement the transmission of the spatial stream 230 according to partial rank nulling. For example, the communication controller 215 may configure the antennas 225 and any other settings to facilitate or implement the transmission of the spatial stream 230 according to a particular direction or vector (e.g., as determined by the coordinator 210) to perform partial rank nulling at a particular STA 240. The communication controller 215 may control, manage, and implement the transmission (e.g., communication) according to timing and frequency (such as the selected channel or band) and the direction or vector in which partial rank nulling is performed.

[0061] AP 205 and / or STA240 may include a communication controller 215 to facilitate wireless communication with each other. The communication controller 215 may include and / or utilize wireless communication interfaces that facilitate communication via standards such as 802.11a / b / g / n / ac / ax, Bluetooth, cellular (e.g., 3G, 4G, 5G), Zigbee, Z-Wave, NFC, and others, such as hardware and software, including transceivers, antennas, RF interfaces, ports, and processing devices. The communication controller 215 may control the reception and transmission of signals, data, or messages to facilitate or implement multi-AP transmission using coordinated partial rank nulling.

[0062] AP 205 may include a nulling function 220 for implementing nulling according to coordinated (e.g., agreed-upon) communication between AP 205s. Partial rank nulling may include any technique or action in array signal processing for suppressing interference from signals in a particular direction while retaining any signals arriving from other directions. For example, partial rank nulling may include manipulating the array response to create nulls or zeros in the radiation pattern of interference from a particular direction. The nulling function 220 may include any combination of hardware and software for reducing or eliminating unwanted signals or interference at a receiver (e.g., STA240), such as by adjusting the phase and amplitude of incoming signals. The nulling function 220 may include any combination of hardware and software for minimizing or reducing unwanted signals or interference (e.g., to below an acceptable threshold level) (e.g., without completely removing the interference).

[0063] The nulling function 220 may include a function for measuring interference from a particular AP 205 from various receive vectors or directions relative to STA 240. Direction may include any path or route along which a transmitted signal travels, is directed, or points (e.g., as a vector), and may be specified by its position relative to a reference point or object (e.g., an AP and / or STA). The nulling function 220 may identify or use signals (e.g., probe signals) measured from multiple angles, directions, or vectors, and identify the angle, direction, or vector from which, along which, or at which the interference is lowest or below an acceptable threshold. The nulling function 220 may include or utilize a precoder (e.g., resident within the coordinator 210) to determine the direction or angle along which the interference is lowest or reduced below the threshold.

[0064] AP 205 and station 240 may include an antenna 225. The antenna 225 may include any transmitting or receiving antenna. The antenna 225 may include or be coupled to a communication link and / or transceiver that implements communication, including a chain of circuitry (e.g., amplifiers, filters, analog / digital and / or digital / analog converters, processors, signal combiners, and other circuitry that facilitates signal transmission or reception).

[0065] AP 205 and station 240 can perform spatial stream 230 communication (e.g., spatial stream M expected for a particular STA 240 by AP 205, or all the number of spatial streams N transmitted by AP 205). The spatial stream 230 can include any data stream transmitted or received through separate antennas in a MIMO wireless communication system. For example, the spatial stream can be transmitted or received on more than one antenna, and multiple spatial streams can share the same set of antennas. For example, when transmitted on multiple antennas, each spatial stream can use a unique beamforming vector, which can be different from the vectors for other spatial streams transmitted on the same set of antennas. The spatial stream 230 can provide or facilitate improved throughput and reliability by using multiple antennas to create distinct data paths. The spatial stream 230 can be suitable for directional control and transmission with partial rank nulling.

[0066] System 200 can include or use any number of spatial streams 230, including any independent data streams simultaneously transmitted on multiple antennas in a MIMO (multiple input multiple output) system. System 200 can include STA 240, which can be configured to communicate with a wireless network (e.g., WLAN of BSS 250) to receive and transmit data. System 200 can allow STA 240 to simultaneously receive multiple spatial streams 230 via one or more receive antennas 225 (e.g., two receive antennas for each STA 240). Each spatial stream 230 can represent an independent data stream transmitted from AP 205, which can minimize interference in several dimensions / directions. The number of dimensions or directions in which partial rank nulling can reduce interference can be less than the number of spatial streams 230 that STA 240 can receive. For example, if the STA has two receive antennas 225 (e.g., can receive signals in two dimensions or directions), then partial rank nulling can minimize interference along one dimension or direction as seen by STA 240.

[0067] The number of spatial streams 230 that STA 240 can support can vary based on the capabilities of the network and the MIMO configuration. For example, if STA 240 has multiple receive antennas 225 and the network is configured for 2x2 MIMO, then STA 240 can simultaneously receive two spatial streams 230. Each spatial stream 230 can carry independent data, thus effectively increasing the data capacity and improving the overall throughput, data rate, increased system capacity, and / or wireless network reliability.

[0068] Now refer to Figure 3, An example of the plot 300 of the signal space 302 of the transmission received by the STA240 is an aspect of the technical solution. As shown in the plot 300, a station 240 (e.g., STA1) having a total of K = 2 receive antennas 225 can receive a total number N = 3 spatial data streams 230 transmitted by the AP 205 (AP1). STA1 can be within the BSS250 of the transmitting AP1 205 and can receive all 3 spatial data streams 230 transmitted by AP1, even though only one of these spatial data streams 230 is intended for STA1.

[0069] For example, AP1 can transmit N = 3 spatial streams 230 to multiple STAs 240 within its BSS250 via downlink (DL) MU-MIMO. Among the total N = 3 spatial data streams 230 transmitted by AP1, M = 1 stream (e.g., a single spatial data stream 230, where M < N) can be intended for STA1. Although the plot 300 shows the STA1 stream (e.g., the stream intended for STA1) being directed at an angle away from the X-axis, the remaining two spatial data streams 230 (e.g., interfering streams from AP1) are directed along the X-axis. The Y-axis (which is orthogonal or perpendicular to the X-axis) can represent the direction or vector along which transmissions on the signal space 302 of STA1 are nulled or partially nulled. Thus, the STA1 stream (at least partially directed along the Y-axis) has interference below a threshold in at least one direction and can thus be received by STA1. For example, the STA1 stream can have no interference in at least one direction.

[0070] In Figure 3 the example, the receiving station 240 (e.g., STA1) can have any number K of receive antennas 225 such that M < K < N, where M corresponds to the total number of data streams intended for the receiving station 240 and N corresponds to the total number of data streams transmitted by the AP 205 to any number of receivers. In the plot 300 example, N = 3, M = 1, and K = 2. In such a scenario, in order for STA1 240 to be able to decode its own M intended spatial streams 230, AP1 205 can beamform the transmitted spatial streams such that the signal strength from the interfering streams (e.g., the N - M = 2 streams aligned with the X-axis) causes the signal at STA1 to be minimized at STA1 240 in a set of M linearly independent directions. As shown by the STA1 stream, the M intended streams 230 can be recovered by STA1 240 by projecting them away from the X-axis.

[0071] AP1 205 may include a properly configured long training field (LTF) in its transmission such that STA1 240 can estimate both: i) the directions of its M intended streams, and (ii) M distinct directions in which interference is minimized. The technical solution may include or provide a framework for scenarios in which any number of APs 205 perform partial rank nulling towards any number of STAs 240. For example, when two APs 205 are utilized, prior to implementing coordinated transmission, the first AP 205 (e.g., AP1) and the second AP 205 (e.g., AP2) may perform coordination (e.g., during a coordination phase), where messages may be exchanged between AP1 and AP2 to identify each receiving STA for which interference is to be nulled completely or partially. For example, AP 205 may identify an STA 240 having more receiving antennas than its intended spatial streams (e.g., antenna K = 2, while the received streams N = 10, where only M = 1 is intended for the STA).

[0072] Such identified STAs may include interference that is sufficiently prominent as seen from the OBSS AP to include nulling (e.g., the STA may have an interference signal strength or power above a specific threshold). For example, the threshold may include the background signal noise level, or 2, 3, 4, 5, 10, or greater multiples of the background noise level. For example, the threshold may be defined with reference to other signals, such as the signal strength, amplitude, or power of the received intended streams (e.g., 1 / 2, 1 / 3, 1 / 4, or 1 / 8 of the signal strength, amplitude, or power of the expected received spatial streams).

[0073] For each STA identified to have its interfering streams partially nulled, AP1 and AP2 may identify a set of linearly independent receiving directions in which interference from the two APs will be minimized. The linearly independent receiving directions may include distinct and uncorrelated paths, directions, or channels through which signals may be received by multiple receiving antennas 225. AP1 and AP2 may dynamically change such a set of directions from one coordinated transmission to the next depending on: i) other receiving STAs, and ii) the number of spatial streams intended for each STA.

[0074] Once the set of directions is identified, AP1 and AP2 can start coordinated transmissions that are synchronized in both time and frequency. For example, out of the total number N1 of spatial streams transmitted from AP1, a subset of M1 spatial streams can be expected to be for STA1 that has a number K1 of receive antennas. The configuration can include the M1 spatial streams expected for STA1, which is less than the number K1 of receive antennas and also less than the total number N1 of spatial streams from AP1 (e.g., M1 < K1 < N1). Similarly, out of the N2 streams transmitted from AP2, M2 streams can be expected to be for STA2 that has K2 receive antennas such that M2 < K2 < N2. In such a configuration, both STA1 and STA2 can be selected, determined, or configured such that partial rank nulling is performed on them by AP1 or AP2. AP1 or AP2 can use beamforming for the directions on which partial rank nulling is to be performed to coordinate the transmission of their data streams in time and frequency to reduce interference and allow simultaneous transmissions.

[0075] Now referring to Figure 4 , example plots 402 and 404 illustrate the received signal space 406 of STA1 and the received signal space 408 of STA2, which are the receivers of transmissions in which AP1 and AP2 perform coordinated partial rank nulling in a multi-AP transmission example. Figure 4 This can correspond to an example in which the present technical solution utilizes two APs 205 (such as Figure 2 those illustrated therein). The APs 205 can apply appropriate beamforming vectors to their respective spatial streams 230 to transmit the streams at least along the specified directions or vectors as received by the expected STAs such that the same streams will be partially or completely nulled along the specified directions at the non-expected receiving STAs. For example, the beamforming vectors applied to the spatial streams can minimize the interference from both AP1 and AP2 at a set of M1 independent receiving directions at STA1, as pre-agreed during the coordination phase. By projecting the streams onto such determined M1 directions, the M1 expected streams for STA1 can be recovered. For example, this can equally apply to STA2, which has a corresponding set of M2 directions. AP1 and AP2 can include appropriately constructed long training fields (LTFs) in the coordinated transmissions such that STA1 and STA2 can estimate both: i) the directions of their respective expected streams, and (ii) the directions in which the interference from AP1 and AP1 is minimized.

[0076] AP1 and AP2 can each transmit a total number N = 2 spatial streams 230, where only M = 1 spatial stream 230 is expected to be received by the STAs 240 of its own BSS 250 of the corresponding transmitting AP 205, and each receiving STA 240 includes K = 2 receiving antennas 225. For example, for STA1, the remaining one spatial stream from AP1 and the two spatial streams from AP2 can generate interference that will be partially nulled. As illustrated, a total of 3 spatial streams are partially nulled (e.g., aligned with the Figure 4 X-axis or X-direction in

[0077] ). As shown in plot 402, the interfering stream 412 from AP1 and the interfering streams 414 and 416 from AP2 are directed along the X-direction of the STA1 received signal space 406 and removed or minimized along the Y-direction, while the desired stream 410 from AP1 is directed along a different direction (e.g., closer to or more closely aligned with the Y-direction) and thus is not removed or minimized along the Y-axis or Y-direction and is received by STA1. For example, the Y-axis (also referred to as the Y-direction) can be orthogonal or perpendicular to the X-axis (also referred to as the X-direction). For example, when the desired spatial stream has a component greater than a threshold in the Y-direction, the STA1 received signal space allows such a stream to be received at STA1. For example, the threshold can be as high as 5% of the total received signal strength of the desired spatial stream. For example, depending on the design, the threshold can be as high as 5%, 10%, 15%, 20%, 30%, or greater than 30%.

[0078] Similarly, as shown in plot 404, the interfering streams 410 and 412 from AP1 and the interfering stream 416 from AP2 are directed along the X-direction of the STA2 received signal space 408, and their signals are also minimized or removed along the Y-direction, while the desired stream 414 from AP2 is directed along a different direction (e.g., closer to or more closely aligned with the Y-axis) and thus is not removed or minimized along the Y-direction and is received by STA2. In some embodiments, AP1 and AP2 can simultaneously transmit the streams 410, 412, 414, and 416 in the presence and range of STAs 1 and 2, and the interference and non-interference of the streams can occur simultaneously. Thus, AP1 and AP2 can simultaneously and in a coordinated manner (e.g., at the same time and frequency) transmit spatial streams to their own corresponding STAs 240, using partial rank nulling to prevent interference to non-intended STAs 240.

[0079] In one example, as part of the coordination phase, the APs 205 (e.g., AP1 and AP2) may exchange information about a precoder algorithm that is used to calculate the beamforming vectors for each STA 240 (e.g., STA1 and STA2) to achieve partial rank nulling. For example, as part of the coordination phase, the APs 205 may exchange information, data, or descriptions of direction vectors in which interference will be minimized at the receiving antennas 225 of each STA. For example, as part of the coordination phase, a single AP 205 may calculate the beamforming vectors for all spatial streams and share these vectors with other participating APs.

[0080] Using the information exchanged during the coordination phase, a receive direction in which interference for each STA 240 is minimized may be determined or generated based on or using a policy (e.g., a policy specified in a standard). The choice of policy may be fixed to a "default" implementation, or may be determined based on the capabilities of the APs 205 and / or the STAs 240. For example, for an STA receiving M expected spatial streams from an AP 205 of its own BSS 250, the policy may include interfering with the AP 205 to minimize interference at the receiver of the STA along M directions that correspond to the M strongest eigenmodes of the channel between the STA 240 and its AP 205 (e.g., the AP 205 of the STA's own BSS 250). For example, for an STA receiving M expected spatial streams from an AP of the STA's own BSS, the policy may include interfering with the AP 205 to minimize interference at the receiver of the STA along M directions that correspond to the M strongest eigenmodes of the channel between the STA 240 and the interfering AP 205.

[0081] For example, as part of the coordination phase, AP1 and AP2 may each perform channel sounding on STA1 and STA2. Each STA 240 may measure the MIMO channel from each sounding AP 205 and may provide a response that includes the measurement. When measuring channels from different APs, the relative phase offsets across the receiving antennas of the STA 240 may be maintained at a constant value.

[0082] During the coordination phase, different independent variants and their combinations can be implemented. For example, the STA 240 can feedback an estimate of the MIMO channel from the probing AP via a compressed beamforming report format (CBR) (e.g., one defined in 802.11). For example, the STA 240 can feedback an estimate of the MIMO channel from the probing AP in Cartesian form. For example, for an AP 205 (e.g., an interfering AP) from another BSS 250 different from the BSS 250 of the STA, the STA 240 can feedback a linear transformation of the MIMO channel from the AP 205. The linear transformation can be determined by the MIMO channel previously measured between the STA and its own BSS AP. For example, the linear transformation can represent a projection on one or more eigenmodels of the MIMO channel measured between the STA 240 and its own BSS AP 205. For example, for the probing AP 205, if the STA 240 is receiving M expected spatial streams from its own BSS AP 205, then the STA 240 can feedback M preferred sets of directions, where the corresponding AP can minimize interference.

[0083] As part of the coordination phase, the APs 205 (e.g., AP1 and AP2) can jointly perform channel sounding of the STA 240. The APs 205 can jointly transmit null data packets (NDPs) that can be synchronized in time / frequency. The total number of sounding dimensions in the NDP can be equal to the total number of antennas 225 across the APs 205. The jointly transmitted NDP can be preceded by one or more NDP announcements (NDPAs) frames. For example, a single AP 205 can transmit an NDPA on behalf of all APs to the STAs to be sounded across the BSS 250. For example, all the APs 205 can transmit their NDPAs in sequence, where the NDPA of each AP addresses the STAs 240 within its own BSS 250. For example, all the APs 205 can transmit their NDPAs simultaneously but frequency-separated (e.g., via OFDMA), where each AP 205 addresses the STAs 240 within its own corresponding BSS 250. The coordinated transmission can be preceded by a trigger frame transmitted by one of the APs 205. Based on the trigger frame, all the participating APs 205 can synchronize their carrier frequency offsets (CFOs) relative to the AP 205 that transmitted the trigger frame and synchronize the start time of their coordinated transmission.

[0084] B. Multi - AP coordination of per - CBF TXOP frame sequences using per - station feedback scheduling

[0085] The technical solution of the present disclosure may include multi-AP coordination for each CBF TXOP frame, where an initial scheduling consensus between APs may be established before ICR feedback from stations, while allowing the APs to adjust the schedule based on updated station information from subsequent ICR station messages. For example, the technical solution may utilize an initial control frame (ICF) sent by a first (e.g., initiating) AP to a second AP and the stations (STAs) of the first AP to initiate CBF synchronization. The STAs of the first AP may respond to this ICF with their initial control response (ICR), and the second (e.g., responding) AP may send a CBF response along with the ICFs of the STAs of the second AP, allowing a preliminary consensus to be reached between the first AP and the second AP regarding the scheduling and determination of CBF communication, including information about the STAs that these APs are expected to participate in, and all of this may be completed before receiving the ICR from the STAs.

[0086] Then, the STAs of the second AP may reply to the ICF of the second AP with their ICRs. The first AP may transmit another ICR to update any information about the STAs of the first AP, such as corrections to any previous assumptions about the participation, availability, or parameters of these STAs. The information from the ICRs of the STAs of the first and second APs may be used by the first AP to generate an updated schedule and determination to coordinate or synchronize CBF transmissions. Then, the first AP may generate a CBF trigger, which may include updated information, including updated information about the participating STAs, their updated parameters, and the scheduled timing for initiating and implementing CBF PPDU transmissions in the device.

[0087] Figure 5 is an example block diagram of a multi-access point coordination system 500 for each CBF TXOP frame sequence. The example system 500 may incorporate, utilize, or include any features or functions of system 200 or example features 300 and 400, and vice versa. The system 500 may include one or more APs 205 that communicate wirelessly with one or more stations (STAs) 240 and one or more APs 205 via one or more links 560. For example, the first AP 205 may communicate wirelessly with one or more stations (e.g., the first STA 240, which may be located in the BSS 250 of the first AP) via the link 560. Additionally, the second AP 205 may communicate wirelessly with one or more stations (e.g., the second STA 240, which may be located in the BSS 250 of the second AP) via the link 560. The first AP 205 and the second AP 205, as well as any additional APs 205 described herein, may communicate wirelessly with each other via one or more links 560 to coordinate CBFs between each other and with respect to any station 240 with which they communicate (which includes the first and second stations 240, or any other station 240 served by either of the APs 205). Although Figure 5Two APs 205 and two STAs 240 are illustrated, but it should be understood that the systems and methods described herein may be applicable to any number of APs 205 and STAs 240. Each AP 205 (e.g., the first AP 205, the second AP 205) may include at least one coordinated beamforming manager 505 (CBFM 505), at least one station selector 510, and at least one communication controller 215.

[0088] The coordinated beamforming manager (also referred to as CBFM 505) may include hardware and software for establishing, managing, and operating CBF operations. CBF operations may include channel state information (CSI) acquisition, CSI exchange, beamforming weight calculation, transmission coordination, and other operations. CBFM 505 operations may include, for example, the communication or exchange of messages for synchronizing CBF communications, such as the exchange (e.g., sending or receiving) of CBF messages 520, including CBF requests 525, CBF responses 530, initial control frames (ICF) 535, initial control responses (ICR) 540, or CBF triggers 545. For example, the CBFM 505 of the first AP 205 may perform CSI acquisition for the first station 240 and the second AP 205. The CBFM 505 may include at least one CBF synchronizer 515. The CBF synchronizer 515 may synchronize, coordinate, or otherwise align each AP 205 when performing CBF PPDU transmissions. A CBF PPDU may correspond to the transmission of a PPDU to employ CBF operations or techniques. The CBF synchronizer 515 may utilize the frames and parameters of multiple CBF messages 520.

[0089] The CBF synchronizer 515 may include any combination of hardware and software for synchronizing or negotiating CBF communications. The CBF synchronizer 515 may include computer code, instructions, or data for communicating with other (e.g., remote) APs 205 or stations 240 of the same or different BSSs 250 to facilitate negotiating or synchronizing the timing or configuration of CBF communications. The CBF synchronizer 515 may include, generate, transmit, or receive one or more CBF messages 520 for communicating with either an AP 205 or a station 240 via a link 560. The CBF message 520 may include information associated with the CBF PPDU transmission of the corresponding AP 205. Each CBF message 520 may correspond to at least one of a CBF request 525, a CBF response 530, an initial control frame 535 (ICF 535), an initial control response (ICR 540), or a CBF trigger 545. Each CBF message 520 transmitted between participating devices (e.g., an AP 205 and an STA 240) may be separated by a SIFS to provide a time duration or delay interval between transmissions. The SIFS (Short Inter-Frame Space) may include a short time interval (e.g., 16 us) used in a wireless communication protocol to allow for timely receipt of an acknowledgment and synchronization between transmissions. For example, prior to the CBF PPDU transmission of a first AP 205, the CBFM 505 may trigger the CBF synchronizer 515 to transmit a CBF message 520 to a second AP 205. There may be a SIFS before the CBF message 520 that temporally separates it from a previous CBF message 520, and there may also be a SIFS after it that separates it from a CBF transmission (e.g., a CBF PPDU) to be transmitted.

[0090] The CBF request 525 may be any message or transmission for initiating coordinated beamforming (CBF) communications between an AP 205 and a station 240. The CBF request 525 may include, for example, a message sent by a first (e.g., initiating) AP 205 to a second (e.g., receiving) AP 205 and the STA 240 of the initiating AP 205, signaling the start of a CBF coordinated transmission opportunity (TXOP). The CBF request 525 may include information about the participating STA 240, such as its identifier and expected parameters of the CBF (e.g., station capability data 550, including, for example, the number of spatial streams, transmission power, beamforming weights, timing synchronization, and channel state information). The CBF request 525 may serve as the transmitted initial control frame (ICF) 535 and be configured to request or collect and convey information for CBF coordination to the second AP and its own STA 240. The CBF request 525 may be transmitted by the first AP at the start of the TXOP to initiate a CBF synchronization or coordination process.

[0091] For example, if a station of the first AP (e.g., AP1-STA) is not available for a particular TXOP (e.g., Msg4 in station back feedback scheduling), then a CBF request 525 (also referred to as CBF-req) may signal the termination of the CBF-TXOP. The CBF request 525 may indicate 'N' candidate STA groups (e.g., N = 3), where one group may be selected for a particular upcoming or current TXOP. Each group may identify a particular combination of a station of the first AP (e.g., AP1-STA) and a station of the second AP (e.g., AP2-STA), which may be limited to a total of 4 STAs and will participate in, for example, 2 STAs per AP. Example signaling options may include the AID per STA (e.g., 11 bits), the "short AID" per STA (represented with fewer bits (e.g., 6 bits)), and a pre-negotiated / defined mapping to the AID, or a group ID (e.g., 8 bits) with a pre-negotiated or defined mapping to a particular combination of AP1-STA and AP2-STA (e.g., similar to a VHT GID). Additional information signaled per group may include one or more of the following: Nss per STA (e.g., 1 or 2 bits), MCS information per AP1-STA (e.g., 6 bits), RU indication (e.g., 9 bits), and the maximum payload duration (e.g., the number of payload symbols excluding padding) that can be supported by AP1 (e.g., 9 bits). Common information for all STA groups (e.g., bandwidth (e.g., 3 bits) and puncturing (e.g., 5 bits)) may be signaled in the common information and / or special user information fields of the trigger frame containing the CBF-req. It may additionally include transmission information (e.g., MCS, Nss, RU allocation, etc.) for AP2 to transmit a response in a subsequent PPDU (e.g., a TB-PPDU or a non-HT DUP PPDU).

[0092] For example, if there is no available AP1-STA for the current TXOP (e.g., Msg4 in post-station feedback scheduling), then the CBF request 525 (e.g., CBF-req) can signal the termination of the CBF-TXOP. For example, the CBF request 525 can indicate information of the 'N' AP1-STAs (e.g., N = 2) participating in this C-BF TXOP. The signaling options include the AID of the participating AP1-STA (e.g., 11 bits per STA) or a "short AID" with a pre-negotiated / defined mapping to the AID (represented by fewer bits, e.g., 6 bits per STA). The CBF request 525 can include the number of spatial streams (e.g., spatial stream limit) of each participating AP1-STA, such as Nss (e.g., 1 or 2 bits per STA), RU indication (e.g., 9 bits), BW (e.g., 3 bits), and puncturing (e.g., 5 bits), which can be signaled in the common information and / or special user information fields of the trigger frame containing the CBF-req. The CBF request can specify the maximum number of participating AP2-STAs (e.g., 2 or 3 bits) allowed for the next CBF transmission in this TXOP and the maximum total number of spatial streams (Nss) of the AP2-STAs allowed for the next CBF transmission in this TXOP (e.g., 2 or 3 bits). The CBF request can include transmission information (e.g., MCS, Nss, RU allocation data) for the AP2 to transmit a response in a subsequent PPDU (e.g., TB-PPDU or non-HT DUP PPDU).

[0093] The CBF response 530 can be any message or transmission for responding to the CBF request 525 and providing feedback on CBF coordination. The CBF response 530 can include, for example, a message sent by the second AP 205 to the first AP 205 and its STA (e.g., the STA of the second AP), indicating that the second AP participates in the CBF process. The CBF response 530 can include information about the participating STA240 of the second AP 205, such as its availability, duration, and parameters required for CBF coordination (e.g., number of spatial streams (Nss), modulation and coding scheme (MCS) index, transmission power, beamforming weights, timing synchronization, and channel state information). The CBF response 530 can respond to the CBF request 525 or the ICF 535 sent by the first AP. The CBF response 530 can be configured to provide the requested information to the first (e.g., initiating) AP 205 to establish, determine, generate, modify, or update the scheduling or synchronization for CBF transmission, such as in response to any information that the AP 205 has about the STA 240 of the responding AP 205.

[0094] For example, the CBF response 530 (also referred to as CBF-resp) may signal or indicate whether a transmitting AP (e.g., AP2) will participate in the current CBF TXOP. If AP2 is going to participate, or if the CBF response is sent in response to a previous CBF-req (e.g., from AP1) in the same TXOP, then the CBF-resp may signal the preferred group among those groups signaled in the CBF-req. For example, the CBF response 530 may indicate or signal from a list of choices provided in an ICF (e.g., CBF request) from a first AP (e.g., AP1) the preferred set of stations participating in the CBF. The CBF response 530 may indicate or include the maximum payload duration (e.g., the number of payload symbols excluding padding) (e.g., 9 bits) that can be supported by AP2 for the group and the relevant information (e.g., MCS) of each AP2-STA in the group that needs to be included in the preamble of the CBF PPDU. The CBF response 530 may indicate or include the nominal padding amount (e.g., 0us, 8us, 16us, or 20us) required by the AP2-STA in the group. The CBF response 530 may include transmission information (e.g., MCS, Nss, RU allocation, etc.) for AP1 to transmit a response in a subsequent PPDU (e.g., TB-PPDU or non-HT DUP PPDU).

[0095] For example, the CBF response 530 (e.g., CBF-resp) may indicate or signal whether a transmitting AP (e.g., AP2) will participate in this CBF TXOP, and if so, then it may signal a list of 'M' (e.g., M = 2) AP2-STAs participating in this CBF TXOP. The signaling option may include the AID (e.g., 11 bits) of each participating AP2-STA, or a "short AID" with a pre-negotiated / defined mapping to the AID (represented with fewer bits, e.g., 6 bits per STA). The CBF response 530 may include data on the MCS (e.g., 6 bits) and Nss (e.g., 1 or 2 bits) of each participating AP2-STA, and the maximum payload duration (e.g., the number of payload symbols excluding padding) (e.g., 9 bits) that can be supported by AP2 for the participating AP2-STAs. The CBF response 530 may include transmission information (e.g., MCS, Nss, RU allocation, etc.) for AP1 to transmit a response in a subsequent PPDU (e.g., TB-PPDU or non-HT DUP PPDU).

[0096] The Initial Control Frame (ICF) 535 can be any message or transmission for controlling and coordinating CBF communication between an AP and an STA. The ICF 535 can include a message sent by a first AP to a second AP and its STA to initiate a TXOP for CBF coordination, including a Multi-User Request to Send (MU-RTS) or a Buffer Status Report Poll (BSRP) transmission. The ICF 535 can include information used by the CBF synchronizer 515 to establish a preliminary schedule or determination for CBF communication, such as the participating STAs and their expected parameters (e.g., transmit power, beamforming weights, timing synchronization, and channel state information). The preliminary schedule can include at least one of a Modulation and Coding Scheme (MCS) for one or more STAs, the Nss for one or more STAs, the packet or ordering for each participating STA, the duration of the CBF transmission, and the parameters signaled in the CBF preamble. As described herein, the final schedule before a CBF PPDU transmission can include the same parameters as the preliminary schedule. For example, the preliminary schedule can include one or more MCS settings for each of the STAs 240 participating in the CBF TXOP. To establish one or more MCS settings, the CBF synchronizer 515 can utilize conditions such as the distance between each STA 240, interference and obstacles, the downlink Channel State Information (CSI) of each participating STA 240 in the CBF TXOP, the type of interference nulling (i.e., partial rank or full rank) for each participating STA 240 in the CBF TXOP, or the number of spatial streams (Nss) allocated to each participating STA 240 in the CBF TXOP. By utilizing the conditions, the CBF synchronizer 515 can establish one or more MCS settings to adapt the MCS of each STA 240 dynamically using link adaptation.

[0097] The ICF 535 can respond to the determination that CBF synchronization and coordination are to be initiated (e.g., in response to data to be transmitted). The ICF 535 can operate by signaling the start of the CBF process and collecting the necessary information from the STA and the second AP. The ICF 535 can be transmitted by the first AP at the start of the TXOP to initiate the CBF process (e.g., as the CBF request 525). Examples of the TXOP can include at least one of CBF, Wi-Fi QoS, multi-user transmission, high-throughput Wi-Fi, and other TXOPs. The second AP 205 can transmit the ICF 535 to each second STA 240 and the first AP 205 to notify of the upcoming TXOP. The second AP 205 can transmit a second ICF 535 to each second STA 240 in response to the first ICF 535 transmitted by the first AP to notify of the upcoming CBF TXOP. The notification can indicate the time interval during which the first AP and the second AP can access to transmit data packets or data to one or more stations of the first AP and one or more stations of the second AP without interruption (e.g., via one or more CBF transmissions). The notification can indicate the time interval during which the second STA 240 can access to transmit data packets or data to the second AP without interruption. The ICF 535 can allow the second STA 240 to transmit multiple frames within the allocated time. The notification of the ICF 535 can indicate that the upcoming TXOP is a CBF TXOP by using action frames, duration fields, control frame signaling (e.g., MU-RTS, BSRP, null data packet announcements, CBF reports), QoS TXOP management, frame sequences, etc. For example, the CBFM 505 can include NDPA frames (e.g., indicating the start of CBF feedback), NDP frames (e.g., probes), and CBF feedback frames to provide CSI to indicate that the TXOP is a CBF TXOP.

[0098] An Initial Control Response (ICR) 540 can be any message or transmission for responding to an Initial Control Frame (ICF) 535 and providing feedback regarding CBF coordination, including an indication of the ability to participate, the availability to participate, or the duration of communication in a CBF TXOP. The ICR 540 can be any message sent by STAs of the first and second APs to their respective APs, the message indicating their availability and parameters for CBF coordination. The ICR 540 can include information regarding the availability, duration, and parameters of STA 240 for CBF coordination. The parameters can include information or values such as transmit power, beamforming weights, timing synchronization, and channel state information. The ICR 540 can respond to the ICF 535 sent by the first AP 205 or the second AP 205. The ICR 540 can operate by providing the necessary information to the AP to update its schedule and synchronization for CBF transmission. The ICR 540 can be transmitted by STAs of the first and second APs after the STAs of the first and second APs receive the ICF 535 from their respective APs.

[0099] The CBF trigger 545 can be any message for signaling the start of a CBF transmission and synchronizing the participating APs and STAs. The CBF trigger 545 can be a message sent from a first AP to a second AP to include any updated information and scheduling (e.g., according to ICR feedback from the STA 240, or according to feedback from the second AP) to initiate a CBF PPDU transmission according to the latest parameters and data (e.g., and according to the updated transmission schedule). The first (e.g., initiating) AP 205 can generate an updated transmission schedule with updated transmission timing after a CBF response from a non-initiating AP 205 in response to the ICF of the initiating AP 205, based on the information in the ICR received from the STA 240 or the CBF response from the non-initiating AP. The CBF trigger 545 can include updated information about the participating STAs (e.g., per-STA MCS, per-STA Nss, etc.), parameters of the CBF transmission (e.g., duration or length of transmission, bandwidth, puncturing information, guard interval, symbol duration, number of long training field (LTF) symbols, LTF type, pre-FEC padding factor, LDPC extra symbols, PE disambiguation, transmission power, beamforming weights, timing synchronization, or channel state information), or the scheduled timing of the CBF PPDU transmission. The CBF trigger 545 can be in response to a preliminary scheduling consensus and any updated information from the ICR received from the STA 240 or the CBF response received from the non-initiating AP after an initial schedule. The CBF trigger 545 can operate by signaling the start of the CBF PPDU transmission and ensuring synchronization among the participating APs and STAs. The CBF trigger 545 can be transmitted by the first AP after updating its scheduling and synchronization information based on the ICR received from the STA 240 of the first or second AP 205.

[0100] The CBF trigger 545 can be transmitted before a CBF PPDU (e.g., before SIFS) and can perform one or more of the following functions when preparing for the CBF PPDU transmission: provide the preamble content of the CBF transmission, assist the receiving AP and the transmitting AP in synchronizing the timing / frequency offset, or signal the cancellation of the CBF-TXOP in the case where the transmitting AP is unable to participate or does not intend to participate anymore. The CBF trigger 545 can include the following preamble content of the CBF PPDU: "common" information (i.e., common / shared across STAs), such as one or more of L-SIG length, bandwidth, puncturing information, GI+LTF, number of LTFs, pre-FEC padding factor, LDPC additional symbols, PE disambiguation, etc., similar to the content present in the common information and special user information fields of a trigger frame addressed to an STA. Additionally, the CBF trigger 545 can include an indication of the MCS used to encode a portion of the CBF preamble with variable MCS, the number of symbols in the portion of the CBF preamble with variable MCS, or the number of STAs served by the CBF PPDU. The values of certain parameters can also be pre-negotiated between APs, such as one or more of BSS color, TXOP duration, GI+LTF, pre-FEC padding factor, LDPC additional symbols, or spatial reuse. Such parameters with pre-negotiated values may not be signaled / included in the CBF trigger 545. Furthermore, the CBF trigger 545 can include per-STA information, such as one or more of MCS, Nss, spatial configuration, and coding. The CBF trigger 545 can indicate the order in which the user fields appear in the preamble of the CBF PPDU. The CBF trigger 545 can indicate the order in which the spatial streams of each STA appear in the preamble and payload of the CBF PPDU. The CBF trigger 545 can also include padding (e.g., pre-negotiated between AP1 and AP2) to provide the receiving AP with additional time to process the CBF trigger 545 content frame and prepare for any upcoming transmission.

[0101] The CBF synchronizer 515 may include various CBF request 525 and CBF response 530 functions to initiate or respond to the initiation of CBF synchronization between APs 205. The CBF synchronizer 515 may configure or generate a CBF request 525 or a CBF response 530 to include any information, data, parameters, specifications, signals, indications, and other forms of data for indicating and coordinating the transmission of CBF PPDUs. The CBF request 525 and the CBF response 530 may indicate the initial control frame 535 (ICF 535) of the AP 205 or the STA 240. The ICF 535 may occur at the beginning of the CBF message 520 to indicate, identify, or otherwise establish the parameters, specifications, metrics, or signals for transmitting the CBF PPDU via the link 560. The ICF 535 may trigger or otherwise initiate communication between the first AP 205 and the first STA 240 or between the first AP 205 and the second AP 205. The ICF 535 may include a message, transmission, or data structure containing information for CBF operations, which includes any transmission or message exchanged between APs 205 or between an AP 205 and an STA 240 during CBF setup or coordination. The ICF 535 may contain and carry data, such as station capabilities 550 or AP capability data 555. The ICF 535 may include any one or more of the following: one or more multi-user request to send (MU-RTS) frames, one or more buffer status report poll (BSRP) frames, one or more synchronization signal blocks (SSB) frames, or a paging frame addressed to the STA 240 participating in the CBF TXOP. The MU-RTS / BSRP may perform the functions of the ICF 535 and initiate the synchronization process between devices (e.g., the AP 205 and the STA 240). The ICF 535 may perform functions related to EMLSR, IDC, power saving, and signal to the STA 240 of the AP and other APs 205 the intention or preliminary determination that the initiating AP 205 will use CBF for communication in the current or upcoming transmission opportunity (TXOP).

[0102] The CBF synchronizer 515 may include functions for configuring multi-user request to send (MU-RTS) to facilitate or trigger communication from multiple devices (e.g., multiple STAs 240) based on reserved or coordinated time slots in a transmission cycle. For example, the buffer status report poll (BSRP) may include a transmission for requesting buffer status information (e.g., buffer size, queue status, or priority information) about the amount of data of stations queued for transmission. For example, the asynchronous signal block (SSB) may include a broadcast performed by the AP 205 to provide initial synchronization and access information.

[0103] The CBF synchronizer 515 may include any functionality for generating, establishing, or updating a schedule for synchronized or coordinated CBF communication. The schedule may be any plan, structure, or information for coordinating or synchronizing CBF communication in participating devices, including any participating APs 205 and STAs 240. The schedule may include data identifying each participant and any time intervals in the CBF PPDU transmissions of the participant or its data. The schedule may include a preliminary schedule initially established between two or more APs 205 based on an initial control frame (ICF) and an initial control response (ICR) or a CBF request and a CBF response, e.g., including data on STAs and APs that the AP 205 may determine are expected to participate. The schedule may include an updated schedule that incorporates feedback from participating STAs or APs and adjustments made in response to the absence of communication from a participant, which may be determined to be non-participating in the CBF TXOP in such cases (e.g., when they do not respond for a time longer than a predetermined duration). The schedule may include information such as transmission timing, participating STAs, their parameters (e.g., MCS, Nss, coding (LDPC or BCC), amount of outstanding data, or queued traffic (e.g., data added to a queue for processing), nominal padding requirements, duration of station availability), transmission parameters (e.g., duration or length of transmission, bandwidth, puncturing information, symbol duration, number of long training field (LTF) symbols, GI+LTF type, pre-FEC padding factor, LDPC additional symbols, PE disambiguation, transmission power, beamforming weights, timing synchronization, or channel state information), and any parameters or data for synchronizing communication. The schedule may include data for controlling the timing and coordination of CBF transmissions, including the timing for individual participants to transmit their data, allowing for reduced phase misalignment and optimized beamforming efficiency.

[0104] Station 240 may include functionality for receiving ICF 535 from AP 205 and generating a response (e.g., initial control response (ICR) 540). For example, when CBF message 520 is received by STA 240, STA 240 may utilize communication controller 215 to respond to CBF message 520 by transmitting ICR 540, providing any information requested to the requesting AP 205, such as the current or future availability of the CBF TXOP, the duration of the availability, the available bandwidth for receiving the CBF transmission, or transmission parameters, including MCS, Nss, or allocated RU information. Communication controller 215 may use ICR 540 to indicate, establish, or otherwise confirm the receipt of ICF 535 and provide additional or requested information for CBF PPDU transmission. When confirming ICF 535, ICR 540 may trigger STA 240 to initiate preparation for receiving the CBF PPDU, such as re-enabling receiver functionality that was previously disabled (e.g., due to being in a power-saving state), or blocking any functionality that may interrupt future reception (e.g., channel switching, power saving, or any scheduled transmission on the same or different link). CBF trigger 545 may initiate, trigger, or otherwise cause coordinated beamforming of antennas 225 of AP 205 and STA 240 by optimizing signals to direct radio waves to maximum signal strength while minimizing interference to unintended STA 240. The first AP 205 may transmit CBF trigger 545 to each participating device involved in the CBF PPDU transmission (e.g., the second AP 205, the first STA 240, the second STA 240).

[0105] Each AP 205 may include one or more station selectors 510 to select, determine, or otherwise identify the selected STAs 240 for CBF operation. The station selector 510 may include any combination of hardware and software for identifying and selecting suitable stations 230 within the range 255 of the AP 205. The station selector 510 may include the function of selecting the stations 240 participating in CBF within one or more BSSs 250. The station selector 510 may utilize any combination of station capability data 550 or AP capability data 555 to select suitable candidate stations 240 based on various capabilities (such as the number of antennas of the AP or candidate stations, bandwidth support, and nulling capabilities, which can be used to determine the suitability of the station 240 for CBF operation). For example, the station selector 510 may identify the STAs 240 capable of supporting CBF based on the reported capability exchanged during the CBF setup process between the APs 205. For example, the station selector 510 may utilize traffic characteristics, such as information on the downlink data traffic of each STA 240 within its BSS 250 at the AP 205, or the attributes of the downlink data traffic available for each STA 250 at the AP 205. The attributes of the downlink data traffic may include specific QoS requirements, such as the maximum allowable latency or the minimum required data rate or zero packet loss, and the data traffic may be intermittent and continuous. For example, the station selector 510 may utilize channel characteristics, such as the RSSI observed at each STA 240 due to the transmission from each AP 205, the proximity of the STA 240 and a particular AP 205 relative to other APs 205, or the downlink channel state information (DL CSI) of each AP 205 at each STA 240.

[0106] The communication controller 215 may include functions for managing and facilitating the communication exchange between the AP 205 and the STA 240 for CBF establishment and operation. The communication controller 215 may include the use, communication, or implementation of the sequence and exchange of the ICF 535, ICR 540, AP capability data 555, and station capability data 550 between the APs 205 to coordinate and establish CBF between the APs 205. For example, during the CBF setup and data transmission phases, the communication controller 215 facilitates and manages the exchange of the ICF 535 between the AP 205 and the station 240 and between different APs 205.

[0107] The CBF synchronizer 515 may include functionality for generating, constructing, or producing a schedule for CBF communication in response to data or information received from participating STAs 240. For example, the CBF synchronizer 515 may be configured to defer or delay generating a CBF communication schedule until an ICR is received from each STA of the participating APs 205, or until a CBF response is received from a non-initiating (responding) AP. The CBF synchronizer 515 may be configured to generate a schedule for CBF communication in response to receiving at least one or all of the ICRs from the STAs of the participating APs 205 (as identified in the ICF from the initiating AP 205) and a CBF response from the responding AP 205.

[0108] The CBF synchronizer 515 may include functionality for adjusting CBF determination and scheduling based on updated information from the STAs 240 (including any ICR messages from the STAs 240 after the CBF response from the responding AP 205). The CBF synchronizer 515 may include functionality for adjusting CBF determination and scheduling based on updated information from the STAs 240. For example, the CBF synchronizer 515 of the second AP 205 may receive one or more ICRs 540 from the second AP STA 240. These ICRs 540 may include updated information of the STA 240, which may be used to adjust a preliminary or initial schedule. When the CBF response 530 is received, the first AP 205 may utilize the station capabilities 550 and information of the ICR 540 from the first STA 240 (e.g., station capability data 550 and AP 205 capability data 555) to determine whether to generate an abort signal for the CBF TXOP. In some examples, the first AP 205 may transmit a CBF message 520 embedded with the abort signal to the AP 205 and the STA 240. The abort signal generated by the first AP 205 may cancel or abort the CBF TXOP based on multiple factors detected by the first AP 205 to prevent resource waste and performance degradation of the system 500. The factors may include CSI issues (e.g., incorrect CSI, incomplete CSI feedback), AP 205 or STA 240 failures (e.g., misaligned timing, unresponsive AP 205), interference detection (e.g., external interference, self-interference), network resource allocation (e.g., priority traffic, congestion), and other factors affecting the CBF TXOP. For example, the first AP 205 may generate an abort signal in response to a CBF response 530 from the second AP indicating insufficient power resources for the CBF PPDU. In another example, the first AP 205 may generate an abort signal in response to the first AP 205 detecting a failure at the AP 205 and the STA 240.

[0109] The first AP 205 may determine whether to generate an abort signal based on the detection of at least one of the above factors.

[0110] For example, in response to the first AP 205 not detecting one or more parameters or factors from a previous transmission, the first AP 205 may transmit, send, or otherwise provide a CBF adjustment (e.g., CBF request 525) to the second AP 205 to indicate whether the second AP 205 may participate in the CBF TXOP. The CBF request 525 may include station capability data 550 (of the first STA 240 and the first AP 205) and AP capability data 555 of the first AP 205. By transmitting the CBF message 520 to the second AP 205, the AP 205 may convey beamforming information and parameters for synchronization according to the CBF synchronizer 515. In some examples, the CBF message 520 may be embedded with the CBF request 525 when initiating the CBF TXOP. For example, the CBF synchronizer 515 may perform the functions of the ICF 535 of the first STA 240 and the second AP 205 within the candidate set of the STA 240 for the CBF message 520 addressed to the second AP 205 and the first STA 240. The functions may include EMLSR, IDC, power saving, and other functions of the ICF 535. For example, the CBF synchronizer 515 may embed the CBF request 525 within the CBF message 520.

[0111] The CBF synchronizer 515 may transfer messages providing CBF adjustments from other APs 205. For example, the CBF synchronizer may generate, transfer, send, or otherwise provide a third message (e.g., CBF adjustment) to the first AP 205 that indicates a CBF adjustment that may be provided in the form of an updated CBF response 530 to a CBF request from the first AP 205. The CBF response 530 may indicate that the second AP 205 and the second STA 240 participate in the CBF TXOP. By transferring the CBF request and the CBF response, the first AP 205 and the second AP 205 may tune the scheduling consensus. The scheduling consensus may correspond to multiple entities (e.g., STA 240, AP 205, antenna 225) that transmit and receive scheduling parameters for CBF PPDU transmission. The scheduling consensus may provide each AP with knowledge of which STAs of each AP will participate in the CBF TXOP, as well as the number of spatial streams expected for each participating STA in the CBF transmission, thereby facilitating the AP to optimally calculate the beamforming vectors. The scheduling consensus may allow each AP to determine what MCS may be used for its STAs in the CBF transmission. The scheduling consensus may provide each AP with information about what MCS may be used for the STAs of other APs in the CBF transmission. The scheduling consensus may provide each AP with information about the duration of the CBF transmission. The scheduling consensus may provide each AP with a partial or complete indication of the PHY preamble content and related parameters used to construct the CBF PPDU. The scheduling consensus may allow each participating entity in the CBF operation to synchronize and align the timing of the CBF PPDU transmission to reduce the occurrence of phase misalignment based on the CBF adjustments from the first STA 240 and the second STA 240. Additionally, using the ICR 540 from the STA 240 and the parameters of the first AP 205 and the second AP 205, the AP 205 may generate a schedule for the CBF PPDU transmission. The schedule may indicate an updated optimal time for synchronizing the AP 205 for the CBF PPDU transmission while minimizing interference to the AP 205.

[0112] The station capability data 550 (also referred to as station capability 550) may include any data or information regarding the capabilities, settings, and parameters of the STA 240 within the AP 205 related to the STA 240's participation in the CBF operation. The station capability data 550 may include, for example, information such as the number of antennas of the STA 240, the bandwidth support corresponding to the station or channel, the downlink CSI (e.g., channel gain, phase information, delay spread, Doppler spread, signal-to-noise ratio), the received signal strength indicator (e.g., signal quality, power level), or the sounding and nulling capabilities of the STA 240 (including data on whether the station supports specific sounding frames or has the ability to provide or determine CSI). The station capability data 550 may include or correspond to parameters 525 such as the maximum client limit of the STA 240, the antenna configuration, the nulling capabilities, the type and capacity of traffic handled by the station, path loss observations, the role in the network topology (e.g., whether the station is a relay or a primary endpoint), and any data regarding channel conditions, interference levels, data loss, or network congestion.

[0113] The AP capability data 555 (also referred to as AP capability 555) may include any characteristics or attributes that define the performance or functionality of the AP 205. The AP capability data 555 may include characteristics or attributes related to wireless network communication. For example, the AP capability data 555 may include the number of antennas used for transmitting or receiving wireless signals supported by the AP 205, the bandwidth supported by the AP 205, the sounding capabilities supported by the AP 205 (e.g., joint sounding or individual sounding), or the nulling capabilities supported by the AP 205 (e.g., full rank nulling, partial rank nulling, maximum number of nulling dimensions). For example, the AP capability data 555 may include the maximum number of OBSS stations (e.g., stations that may be part of the CBF operation) whose information (e.g., including channel sounding reports) can be stored. The AP capability data 555 may include the precoder type, such as the minimum mean square error (MMSE) or zero forcing (ZF) technique. The AP capability 555 may include the channel and traffic characteristics for selecting the STA 240s participating in the CBF operation. The AP capability data 555 may include information regarding the amount of padding included in frames exchanged between the AP and the STA or between the APs. Padding may provide additional processing time for the receiving device before it responds. The AP capability data 555 may include information indicating the common basic service set (BSS) color or the association identifier (AID) of the participating station 240. The AID may include a unique identifier used in the wireless network to identify and manage devices accessing the network within the same network infrastructure.

[0114] The capabilities that include the AP capabilities 555 or the station capabilities data 550 may include information about the number of antennas, bandwidth, and detection capabilities, the availability of one or more stations 240 to participate in a TXOP (e.g., based on previous power saving indications from the stations 240), or information about the duration of data transmissions of one or more STAs 240 (e.g., based on the queued or pending data traffic at the stations 240, or the average duration measured from previous data transmissions from the stations 240). The capabilities may include the nulling capabilities or the maximum client limit of the AP 205. The AP 205 may be configured to perform handshakes and exchange various information (e.g., via ICF and CBF responses) that includes information about the modulation and coding scheme (MCS) and its associated error vector magnitude (EVM). The MCS may include or identify one or more parameters that indicate the data rate or error correction level in wireless communication, which may be used, for example, to balance the speed of communication with the reliability of transmission. The MCS may define or set a combination of modulation type and error correction coding rate. For example, a value parameter above the threshold of the MCS may use 64 quadrature amplitude modulation (64-QAM) with a lower coding rate for faster data transmission (e.g., a transmission greater than a transmission rate threshold), while a value parameter of the MCS below the threshold may use BPSK with a higher coding rate for more reliable communication under poor signal conditions but at a lower transmission rate (e.g., a transmission less than the transmission rate threshold).

[0115] The capabilities that include the AP capabilities 555 or the station capabilities 550 may include information about parameters such as the AID of each candidate STA, the physical layer capabilities of each candidate station (e.g., the station capabilities data), such as the operating bandwidth, the maximum number of receive spatial streams (e.g., receive Nss), the probe feedback capabilities, and the MAC capabilities and any padding preferences. The capabilities may further include a list of stations for a particular AP, the per-STA spatial stream number (e.g., Nss) for the AP, STA, or STA group, and any resource unit (RU) allocation for the AP, STA, or STA group.

[0116] Still referring to Figure 5, the first AP 205 can use the station selector 510 to select one or more potential stations 240 within its own BSS 250 to participate in the CBF. To make such a selection, the station selector 510 can use, for example, the station capability data 550 of the stations 240 and its own AP capability data 555 (such as channel and traffic characteristics or previous station availability information) to select the STAs 240 to participate in the CBF operation. The station capability data 550 can include or indicate the capabilities, settings, or parameters of the individual stations 240 related to the capabilities and functions of the stations 230 with respect to the CBF. The AP capability 555 can include the characteristics or attributes that define the performance or functions of the AP 205 for implementing wireless communication. The AP capability data 555 can include, for example, information about the amount of padding included in the frames exchanged between the AP and the STA or in the frames exchanged between the APs. Padding can provide additional processing time to the receiving device before it responds. The AP capability data 555 can include, for example, signals or data indicating the amount of padding requested by the receiving device or provided by the transmitting device. The first AP 205 can use the communication controller 215 to exchange with the second AP 205 one or more station capability data 550 indicating the capabilities of the candidate STAs 240. The second AP 205 can similarly collect the AP capability data 555 of the second AP 205 and the station capability data 550 of the stations 240 in the second BSS 250 of the second AP 205, and then share them with the first AP 205. Based on the capabilities of all the candidate stations 240 collected and exchanged, the first AP 205, the second AP 205, or the first and second APs 205 together can determine which stations 240 will participate in the CBF operation. The first AP 205 and the second AP 205 can implement a sequence (such as, the ICF 535) between each other to establish a station group 240 for the CBF 505 operation.

[0117] During the process of the ICF 535 for CBF establishment, the first AP 205 and the second AP 205 may exchange their AP capability data 555, such as the number of their antennas 225 or the supported dimensions, the detection capability and the nulling capability of the AP 205. The first and second APs 205 may utilize parameters, such as a specified common basic service set (BSS) color or an association identifier (AID) indicating the participating station 240. The AID may include a unique identifier used in a wireless network to identify and manage devices accessing the network within the same network infrastructure. The first AP 205 may handshake with the second AP 205 to exchange candidate station capability data 550, such as the number of antennas, bandwidth, detection and nulling capabilities, or AP capability data 555, such as the maximum client limit. The first AP 205 may enter a phase of CBF coordination with the second AP 205, determine the parameters of CBF operation (such as the nulling direction, type, or duration), and utilize the information from the preamble of the frame from the second AP to perform the CBF 505 operation based on the common BSS color or AID.

[0118] AP 205 may include a CBF synchronizer 515 to coordinate or synchronize CBF communications using any combination of CBF messages 520. CBF messages 520 may include any messages for collecting, coordinating, or adjusting information for CBF communications, including CBF requests 525, CBF responses 530, ICFs 535, ICRs 540, or CBF triggers 545. For example, a first AP 205 may include a CBF synchronizer 515 configured to generate, transmit, send, receive, or otherwise provide CBF messages 520 (e.g., a first message, such as an ICF 535) to a second AP 205 or STAs 240 of the first AP 205 to initiate a TXOP for CBF coordination or synchronization between two or more APs 205 and two or more STAs 240 of the first and second APs. CBF messages 520 (e.g., ICF 535) may be transmitted by the CBF synchronizer 515 or CBFM 505 as part of a coordination phase to collect information from STAs 240 within its BSS 255 or to exchange information between APs 205. CBF messages 520 may identify or indicate at least one AP 205 capable of performing CBF operations. In some examples, identification of at least one AP 205 may occur before receiving an ICR 540 from an STA 240 associated with a CBF PPDU transmission. The second AP 205 addressed by a first message (e.g., ICF 535 or CBF request 525) may respond to the first AP 205 by transmitting a CBF response 530. The CBF response 530 may include information about the participating STAs 240 of AP2 205 and any parameters for those STAs for CBF coordination (e.g., MCS, Nss, bandwidth, puncturing information, nominal padding requirements, pending or queued data traffic (e.g., data added to a queue for processing), duration of station availability, transmit power, beamforming weights, timing synchronization, and channel state information). For example, the CBF response 530 may signal the availability and duration of AP2-STAs, allowing the first AP 205 to update its scheduling and synchronization information accordingly.

[0119] By transmitting their initial CBF messages 520 (e.g., ICF 535 or CBF request 525 and CBF response 530), the first AP 205 and the second AP 205 can reach a preliminary or first scheduling consensus. The preliminary or first scheduling consensus may include determinations and settings assumed or established by the first and second APs based on their available information and may correspond to multiple entities (e.g., STA 240, AP 205, antenna 225) that transmit and receive scheduling parameters for CBF PPDU transmission. The first or preliminary scheduling consensus may be updated by a subsequent ICR 540 from a STA 240 of the first or second AP, which may be used to transmit updated information to the AP regarding the availability of the STA or parameters for participating in CBF. The first or preliminary scheduling consensus may be subsequently updated by the first AP based on the CBF response received from the second AP. The first or preliminary scheduling consensus may allow each participating entity in the CBF operation to synchronize and align the timing of CBF PPDU transmission to reduce the occurrence of phase misalignment without any change or correction to the scheduling consensus in a subsequent ICR 540 (e.g., from STA 240).

[0120] The CBF message 520 (e.g., ICF 535 or ICR 540) may contain any information for coordinating CBF communication, including information about the timing, availability, and parameters of any participant, such as the timing of data transmission within the TXOP of each participant at each AP or STA. The CBF message 520 may contain information about the direction in which interference from the second AP 205 will be nulled completely or partially. For example, the CBF message 520 may contain multiple directions for the second AP 205 to partially or completely null the interference. The first AP 205 and the second AP 205 may select a subset of the set of directions while transmitting the CBF PPDU to partially or completely null the interference from the second AP 205. The CBF message 520 may contain a list of identifiers of the first set of candidate stations, information about the proposed start time or duration of the CBF transmission, and the proposed number of spatial streams (e.g., for one or more STAs 240 of the first or second AP). The proposed start time or duration may correspond to the scheduling consensus of the first and second APs.

[0121] The set of directions for partially or completely nulling the interference may correspond to a configuration of beamforming weights or spatial directions that increase the likelihood that the antenna 225, AP 205, or STA 240 does not interfere with the transmitted signal. To achieve this, the set of directions may utilize linear algebra (e.g., vectors, matrices) to find beamforming weights that are orthogonal to the interference channel. By the AP 205 communicating the parameters before CBF PPDU transmission, the AP 205 can effectively improve the synchronization of CBF PPDU transmission.

[0122] The first AP 205 may transmit a CBF message 520 to at least a first STA 240 among a group of one or more candidate STAs 240. The CBF message may include, for example, an ICF 535. The first AP 205 may use a station selector 510 to select, identify, or otherwise indicate the first STA 240 from among the group of candidate STAs 240 based on information that the first AP 205 receives, retrieves, or otherwise obtains regarding the availability of participating in a TXOP or regarding the duration of data transmission of the first group of candidate STAs 240. For example, the first AP 205 may retrieve the availability of the first STA 240 to participate in a TXOP or the average duration of data transmission of the first STA 240. For example, information regarding the availability or average duration of the first STA 240 may be retrieved from AP capability data 555 corresponding to the first AP 205 or station capability data 550 corresponding to the first STA 240. Once retrieved for the first STA 240, the CBFM 505 may compare the availability or average duration with one or more thresholds. The one or more thresholds may indicate a minimum availability or minimum duration for the corresponding STA 240 to participate in a TXOP. In response to the availability or average duration of data transmission of the first STA 240 meeting the one or more thresholds, the first AP 205 may determine, identify, or otherwise indicate that the first STA 240 participates in a CBF TXOP. The first AP may iteratively repeat this process for each first STA 240 within the range of the first AP 205. Upon completion of the iteration, the first AP 205 may determine, identify, or otherwise indicate, based on information regarding the availability and duration of data transmission, that a first group of STAs 240 of the first AP 205 participates in CBF during a TXOP. Each STA 240 in the first group of STAs 240 may include an availability and duration of data transmission that meets the thresholds. Receiving the CBF message 520 by a second AP 205 or the first STA 240 may initiate a CBF TXOP. The CBF TXOP may allow the first AP 205 to use the CBFM 505 to generate and transmit the CBF message 520 without interference or interruption from other APs 205 or STAs 240.

[0123] By transmitting a CBF message 520 (e.g., ICF 535) to the second AP 205, the AP 205 can convey the beamforming information and parameters of the first AP 205 and its STA 240 to synchronize information with the second AP 205 according to or using the CBF synchronizer 515. For example, the CBF synchronizer 515 can perform the functions of the ICF 535 for the first STA 240 and the second AP 205 within a group of candidate STAs 240. The functions of the ICF 535 can be for the CBF message 520 addressed to the second AP 205 and the first STA 240. The functions of the ICF 535 can include EMLSR, IDC, power saving, and other functions of the ICF 535. The functions of the ICF 535 can cause the second AP 205 to respond with beamforming information, parameters, or station capability data of the second AP 205 to the first AP 205. At the same time, the CBF synchronizer 515 can embed the CBF request 525 within the CBF message 520.

[0124] The second AP 205 can receive, retrieve, or otherwise obtain the CBF message 520 (e.g., ICF 535 from the first AP) via the communication controller 215. The CBF message 520 (e.g., ICF 535) can contain an indication that causes the second AP 205 to request information about a second group of candidate stations. The indication can cause, trigger, or enable the second AP 205 to retrieve information about the availability and duration of data transmission for the second STA 240. The requested information can allow the CBFM 505 of the second AP 205 to select a second group of stations from the second group of candidate stations 240 to participate in CBF during the TXOP. The second group of STAs 240 can be different from the first group of STAs 240. The second AP can use the information (e.g., availability and duration) to select each STA 240 in a group of STAs 240. The CBF message 520 (e.g., ICF 535) can contain information, parameters, data, or signals for initiating a CBF TXOP, such as power requirements, station capability data 550, AP capability data 555, available resources, and other parameters for initiating a CBF TXOP.

[0125] The second AP 205 can extract parameters from the CBF message 520 (e.g., ICF 535) and generate a CBF response 530 to provide the parameters of the second AP 205, such as the station capability data 550 of the STA 240 of the second AP, the AP capability data 555 of the second AP 205 (including any information about the available resources), and other information within the ICR 540 received by the second AP from the STA 240 of the second AP 205. Using the parameters of the first AP 205 and the parameters of the second AP 205, the AP 205 (e.g., the first AP) can generate a schedule for CBF PPDU transmission (e.g., via its CBF synchronizer 515). This schedule can be a preliminary schedule generated before any data update from the STA 240 or based on stale data or data available to the AP 205 before the CBF response 530 from the second AP 205. This schedule can be a final schedule determined based on the feedback of the data from the ICR 540 of the STA, updating the information about the AP 205. This schedule can be finally determined or adjusted based on the feedback of the data from the CBF response 530 of the second AP 205. For example, the second AP 205 can embed one or more of the following in the CBF response: confirmation of the proposed start time or duration of the CBF transmission, a list of identifiers of the second group of stations participating in the CBF, or the number of spatial streams (Nss) expected for one or more stations in the second group of stations for the CBF transmission, for the first AP to determine the schedule for the CBF transmission. The schedule can indicate the desired, selected, or optimal time (e.g., the proposed start time) of the CBF PPDU transmission to synchronize the AP 205 while minimizing the interference of the AP 205.

[0126] The AP 205 can generate a schedule based on multiple factors including the ICR 540 and the CBF response 530. The factors can further include the selected STA 240 for the selected CBF transmission, the MCS assigned to each STA, the Nss assigned to each STA, the duration of the CBF PPDU transmission, the duration of the availability of each STA, the queued or pending downlink data traffic of each STA, the parameters of the CBF PPDU, the content of the PHY preamble, etc. The CBFM 505 of each AP 205 can apply, rank, or otherwise utilize each of the factors during the generation or adjustment of the schedule (e.g., preliminary or final determination). The endpoints can include the shortest data transmission, the specific MCS and Nss assigned to each STA 240, the STA 240 within a specific range of each AP 205, etc.

[0127] For example, the AP 205 may generate a schedule for the shortest data transmission implementing CBF PPDU transmission. To generate a schedule for the shortest data transmission, the CBFM 505 of the AP 205 may be configured to select a group of STAs 240 based on information of the duration of the data transmission as a priority. The AP 205 may utilize other factors (e.g., the MCS assigned to each STA 240, the Nss assigned to each STA 240, the availability of participating in the TXOP, the duration of the availability, etc.) to adjust the schedule for the generation of the CBF PPDU. In another example, the AP 205 may prioritize the MCS assigned to each STA to generate a schedule while utilizing other factors to adjust the preliminary schedule. By utilizing various factors, the systems and methods described herein may overcome the challenges of synchronization and timing by following the generated schedule as described above.

[0128] The first AP 205 may establish, set, modify, or configure one or more settings of the first AP 205. The one or more settings may be settings for establishing or coordinating with the second AP 205 the time and frequency for transmitting to the first station 240. The transmission may be a message, a request, a response to a request, or a network data packet, such as a packet of the spatial data stream 230. The time may be the time when the first AP 205 transmits the transmission to the first station 240. The time may be synchronized to the same time as the transmission from the second AP 205 to the second station 240. The time may be synchronized to a different time than when the second AP 205 transmits a second transmission to the second station 240. The one or more settings may cause the first AP 205 to send or transmit a transmission to the second station 240 in a second direction to partially or completely nullify interference at the second station 240. The one or more settings may configure the first AP 205 and the second AP 205 according to a schedule for CBF PPDU transmission.

[0129] The first STA 240 may receive, retrieve, or otherwise obtain the CBF message 520 (e.g., ICF 535) from the first AP 205 via the communication controller 215. The first STA 240 may receive the CBF message 520 (e.g., ICF 535) from the first AP 205 over the link 560. In response to the first CBF message 520 from the first AP 205, the first STA 240 may provide the station capability data 550 of the STA 240 to the first AP 205 via the ICR 540 in response to the receipt of the CBF message 520. The station capability data 550 of the first STA 240 may include an indication of the availability of the station and the duration of the availability of the station. The first STA 240 may formulate the station capability data 550 and the ICR 540 together and transmit the ICR 540 to the first AP 205 as a response to the CBF message including the ICF 535. The first AP 205 may receive one or more indications from the first STA 240 in response to the first message. The one or more indications may correspond to one or more durations of data transmission for each of one or more first STAs 240. The one or more indications may correspond to the availability of the first STA 240 among a group of candidate STAs 240 to participate in a TXOP. The one or more indications may be a flag, an indication, a field in a preamble of a data packet, and other indications. The one or more indications may be received via at least one of a trigger-based physical protocol data unit (TB-PPDU) format or a non-high throughput duplicate transmission (non-HT DUP) format. For example, a first subset of the first STAs 240 may indicate the non-availability of participating in a TXOP, while a second subset of the first STAs 240 may indicate the availability of participating in a TXOP. In another example, a subset of the first STAs 240 may provide the duration of data transmission to the first AP 205. Using the duration of data transmission for each of the subsets of the first STAs 240, the first AP 205 may determine the availability of each of the subsets of the first STAs 240.

[0130] Upon receiving one or more indications, the first AP 205 may adjust, modify, or otherwise generate a first message to indicate the availability of a subset of the first STAs 240 to participate in a TXOP. The first message may be adjusted using the adjustment information within the ICR 540 of each first STA 240. The adjustment information may include a change to the content signaled in the CBF-req, aborting the CBF of the TXOP, reducing the payload duration, or dropping the first STA 240 from the CBF-req. In some embodiments, the first AP 205 may transmit, send, or otherwise provide the adjusted first message (e.g., CBF-adj) to the second AP 205 according to the adjusted CBF request. The adjusted CBF request may indicate the corresponding adjustment information included within the adjusted first message. For example, the adjusted CBF request may signal that the adjusted first message contains "no change to the content signaled in the CBF-req". In another example, the adjusted CBF request may signal that the adjusted first message contains "abort / terminate the CBF of this TXOP". Based on the adjustment information, the first AP may determine whether to initiate a TXOP or abort / terminate a TXOP. Once transmitted to the second AP, the adjusted first message may initiate a TXOP according to the adjusted CBF request.

[0131] Continuing, the second AP 205 may receive CBF-adj from the first AP. The CBF-adj may indicate whether the first AP 205 is terminating or initiating a TXOP. If the first AP 205 is terminating the TXOP, then the second AP 205 may terminate generating an adjusted CBF response or terminate preparing for the TXOP to save computing resources. For example, when terminating preparation for the TXOP, the second AP 205 does not need to identify or select a beamforming vector for the second STA 240 to partially or fully nullify interference at the first STA 240. The first AP 205 may terminate the TXOP based on the lack of availability of the first STA240 to participate in the TXOP, an incorrect MCS assigned to the first STA240, a reduced MCS or data rate of the first STA 240 due to partially or fully nullifying interference (e.g., in the CBF response) identified by the second AP for the TXOP at the second STA 240, an incorrect PPDU format, and other factors for terminating the TXOP. For example, in response to the first AP not terminating the TXOP (as indicated within the CBF adj), the second AP 205 may generate, create, or otherwise determine an adjusted second message (e.g., an adjusted CBF response) to the adjusted first message (e.g., CBF adj or adjusted CBF-req). The adjusted second message may include an adjustment to information regarding the second group of STAs 240 previously indicated by the second AP205 (e.g., within the second message, such as the CBF response or CBF-resp). For example, the adjustment to information regarding the second group of STAs240 may be in response to an ICR 540 transmitted by one or more STAs within the second group of STAs240 in response to the ICF 535 from the second AP (e.g., indicating its availability or duration of availability for the TXOP). For example, the adjusted CBF response may signal that "there is no change to what was signaled in the CBF-resp". In another example, the adjusted CBF response may represent the second AP signaling "abort / terminate CBF for this TXOP".

[0132] The second AP 205 may use a station selector 510 to select, identify, or otherwise indicate a second STA 240 (e.g., to participate in a CBF TXOP) from a pool of a second group of candidate STAs 240. The second group of candidate STAs 240 selected for the CBF TXOP may include any number of STAs 240 of the second AP 205, and may have the same or different number of STAs as the first group of candidate STAs 240 selected by the first AP 205. The station selector 510 may use the presence of data traffic (e.g., outstanding or queued downlink (DL) data traffic of the STA), the applicability of CBF, and other factors to identify the STAs 240 participating in the CBF TXOP. The second STA 240 may be connected to the second AP 205 via a link 560. The second STA 240 may be located together with the second BSS 250 and within a second range 255B of the second AP 205. Once the second STA 240 is connected, the second AP 205 may generate an ICF 535 for the second STA 240 and generate a CBF response 530 for the first AP 205. For example, the second AP 205 may select the second STA 240 based on a reduced amount of data traffic within the channel. The reduced data traffic may indicate a lower amount of interference for the CBF PPDU.

[0133] The first station 240 may be configured to receive a wireless transmission from a first AP via a wireless local area network (WLAN) of the first AP. The second station 240 may be configured to receive a wireless transmission from a second AP via a WLAN of the second AP. The first station 240 and the second station 240 may each be located within a first range 255 of a wireless transmission from the first AP 205 and within a second range 255 of a wireless transmission from the second AP 205.

[0134] The second AP 205 may transmit an ICF 535 to the second STA 240. The ICF 535 of the second AP 205 may be transmitted in response to the ICF 535 of the first AP 205 being transmitted to the second AP 205. The ICF 535 may be one or more (e.g., a series of) frames that are ordered or organized for exchange between the second AP 205 and the second STA 240. Using one or more frames of the ICF 535, the second STA 240 may be configured to set, establish, or otherwise manage communication parameters to allow synchronization, allocate resources, and reduce interference between the first AP 205 and the second AP 205. The ICF 535 may include various frame sequences, such as RTS / CTS, trigger frames, beacon and probe frames, CSI feedback, zeroing frames, coordination frames, CBF PPDUs, and other frames. Upon receiving the ICF 535, the second STA 240 may generate an ICR 540 to transmit to the second AP 205 to confirm receipt of the ICF 535.

[0135] The second AP 205 may transmit a CBF message 520 (e.g., a CBF response) to the first AP 205 during the coordination phase of the first and second APs 205. The message 520 may identify the second station 240 of the second AP 205 for which interference from the first AP 205 will be partially nulled or fully nulled. The message 520 may include or identify a second direction in which interference from the first AP is partially nulled or fully nulled at the second station 510. The direction or set of directions may be linearly independent vectors or directions along which transmissions from the first AP 205 may be reduced below a predetermined threshold (e.g., corresponding to the power or gain level of the signal or a threshold defined based on the noise signal level). The message 520 may include location information (e.g., the location of the STA relative to the AP 205, the coordinates of the STA 240 relative to the AP 205, information about the spatial orientation of the STA, or any other information corresponding to the spatial orientation of the STA). The message 520 may be embedded with or encrypted with the CBF response 530 for transmission to the first AP 205. The second AP 205 may transmit the CBF response 530 to the first AP 205 to confirm receipt of the CBF request 525 and indicate that the second STA 240 is participating in the CBF TXOP.

[0136] In some examples, the first AP 205 may be configured to determine, identify, or otherwise calculate the spatial orientation of one or more antennas 225 of the first AP 205 based at least on a second set of one or more directions. The spatial orientation of one or more antennas 225 of the first AP 205 may be the physical spatial orientation of the antennas or a vector (e.g., a beamforming vector) with different beamforming weights (e.g., amplitude and phase) that varies with any change in frequency. The beamforming vector or spatial orientation of one or more antennas 225 of the first AP 205 may be determined based at least on one or more of the following: the downlink channel state information (CSI) at the first STA 240 as measured from the first AP 205 or the second AP 205, the downlink channel state information (CSI) at the second STA 240 as measured from the first AP 205 or the second AP 205, the location of the first station 240, the second station 240, and / or the first AP 205 (e.g., coordinates or GPS location). The first AP 205 may be configured to beamform transmissions regarding the first station 240 based at least on the spatial orientation of one or more antennas 225 of the first AP 205.

[0137] In some examples, the first AP 205 may be configured to receive, retrieve, or otherwise obtain a packet that includes information about the first STA 240. The packet may include a network packet, message, or transmission that may include information about the channel characteristics of the first station 240 and / or the second station 240. The first AP 205 may be configured to identify, from the received packet, information that indicates the spatial orientation of the first client relative to the second AP. For example, the first AP 205 may determine a linearly independent vector at the STA 240 where the interference at the STA 240 is partially or fully nulled. The first AP 205 may be configured to use the spatial orientation to determine a first set of one or more directions of one or more antennas of the first AP 205.

[0138] The packet information of the first STA 240 may trigger, cause, or otherwise initiate the first AP 205 to embed the timing, frequency, and control information of the first AP 205 (e.g., the direction of the antennas, the MCS assigned to each STA, the Nss assigned to each STA 240, the content of the preamble, etc.) into one or more fields of a third message (e.g., the CBF trigger 545). The third message or CBF trigger may be the final frame in a frame sequence immediately preceding the CBF PPDU. For example, the first AP 205 may embed the timing and control information of the first AP 205 into a third message (e.g., the CBF trigger 545) transmitted to the second AP 205, which may indicate to the second AP 205 the start of the CBF PPDU at a specified time interval from the end of the third message. Based on the timing and control information embedded in the third message, the second AP 205 may start a counter at the end of the third message, which increments to the specified time interval of the start of the CBF PPDU. As the counter increments, the second AP 205 may adjust one or more antennas to align with the first AP 205 to allow synchronization. When the counter reaches the specified time interval, the second AP 205 may start its transmission of the CBF PPDU, thereby synchronizing or aligning its start time with the transmission of the CBF PPDU from the first AP 205. In another example, the first AP 205 may embed the MCS assigned to each first STA 240 of the first AP 205 into the third message before transmitting it to the second AP 205. Based on the embedded MCS of the first STA 240 in the third message, the first and second APs 205 may synchronize and broadcast the same value of the MCS of each first STA 240 in the CBF preamble, which may allow the first STA 240 to correctly decode its MCS and process the CBF PPDU. The packet may include CSI information to align the beamforming weights of the STA 240 and the AP 205 and feedback packets from the AP 205 and the STA 240 to adjust the timing and synchronize the transmitters to improve signal reception.

[0139] The first AP 205 may be configured to transmit, send, or otherwise provide a third message (e.g., CBF trigger 545) to the second AP 205. Before transmitting the third message, the first AP 205 may utilize information from the first STA 240, the second STA 240, and the second AP 205 (as specified within the ICR 540 and the CBF response 530) to update the scheduling and timing of transmissions for each of the participants (e.g., APs and STAs) within the TXOP. The ICR 540 may indicate the availability of the STA 240 or the second AP 205 for the CBF TXOP. The ICR 540 may further indicate how long the STA 240 is available to participate in the CBF TXOP. The CBF response 530 may indicate whether the second AP 205 can participate in the CBF TXOP, a group of second STAs 240 available to participate in the CBF TXOP, the number of spatial streams for each STA within the second group of STAs 240, or the downlink traffic available for the second group of STAs 240 at the second AP 205. For example, the first AP 205 may receive the ICR 540 and the CBF response 530 from the STA 240 and the AP 205. Upon receipt, the first AP 205 may generate a third message (e.g., CBF trigger) for the second AP 205 based on the CBF response 530 and the ICR 540. The first AP 205 may use or derive timing adjustments, confirmation of frequency synchronization, phase alignment (e.g., signal-to-noise ratio, pilot measurement), resource allocation, and timing / frequency instructions from the ICR 540. Additionally, the first AP 205 may use or derive timing alignment information (e.g., to avoid inter-symbol interference), CSI, pilot signals, CSI feedback (e.g., phase information), beamforming weights, beamforming strategies, the MCS of the first STA 240, and spatial alignment from the CBF response 530. Based on the information from the CBF response 530 and the ICR 540, the first AP 205 may embed the information within the third message (e.g., CBF trigger 545). More specifically, the first AP 205 may determine, perform, or otherwise execute a plurality of actions and embed them within the CBF trigger 545. The plurality of actions may include aborting the CBF TXOP, performing the CBF TXOP with a different or reduced group of STAs 240, adjusting the duration of the CBF TXOP, and updating the MCS of the STA 240 based on the ICR 540 and the CBF response 530. For example, the first AP 205 may abort the CBF TXOP based on timing alignment information from the second AP 205 due to an insufficient time length indicated within the ICR 540.In another example, the first AP 205 may use or derive timing alignment information, phase alignment information, a second set of participating STAs 240 and their Nss, or beamforming weights from the ICR 540 and CBF response 530 to determine the MCS for one or more participating first STAs 240 for embedding in the CBF trigger. In another example, the first AP 205 may use or derive timing alignment information, phase alignment information, a second set of participating second STAs 240 and their Nss, the downlink traffic available for the second STA 240, the duration of the availability of the STA 240, or beamforming weights from the ICR 540 and CBF response 530 to adjust the duration of the CBF TXOP relative to the duration of the CBF TXOP initially specified in the CBF request 525.

[0140] In some examples, the CBF trigger 545 within the third message may be broadcast to the AP 205. The CBF trigger 545 may be for initiating, managing, or otherwise establishing a CBF transmission (e.g., CBF PPDU) before the CBF transmission to configure the signal or broadcast of the AP 205. The CBF trigger 545 may include instructions for the AP 205 to participate in the CBF TXOP. The CBF trigger 545 may indicate multiple resources (e.g., time slots, frequency subcarriers, spatial streams), timing information, feedback instructions, beamforming instructions, etc. of each AP 205 involved in the CBF TXOP. In some examples, the CBF trigger 545 may include a CSI request to establish the beamforming weights for the CBF PPDU. In some examples, the CBF trigger 545 may include timing and control signals to align the transmission timing or beamforming direction of each antenna of the AP 205 for the CBF PPDU. In some examples, the CBF trigger 545 may include an abort signal generated by the first AP 205 to cancel or abort the CBF TXOP. Based on multiple factors detected by the first AP 205, the abort signal may prevent waste of resources and degradation of the performance of the system 500. The factors may include CSI issues (e.g., incorrect CSI, incomplete CSI feedback), AP 205 or STA240 failures (e.g., misaligned timing, unresponsive AP 205 or STA 240), interference detection (e.g., external interference, self-interference), network resource allocation (e.g., priority traffic, congestion), unavailability of the STA 240 of the first AP 205 (e.g., as indicated by the ICR from the STA240 of the first AP), limited-duration availability of the second AP 205 or the STA240 of the second AP 205 (e.g., as indicated by the CBF response), selection of the participating STA240 of the second AP 205 and its associated Nss, which requires the first AP to use a beamforming vector that results in a poor or low MCS or data rate for the STA 240 of the first AP (i.e., where the first AP 205 has to sacrifice too much of its own STA data rate to accommodate the STA 240 of the second AP), and other factors affecting the CBF TXOP. For example, the first AP 205 may generate an abort signal in response to the CBF response 530 from the second AP indicating insufficient power resources for the CBF PPDU. In another example, the first AP 205 may generate an abort signal in response to the first AP 205 detecting a failure at the AP 205 and STA240.

[0141] The second AP 205 can be configured to receive, retrieve, or otherwise obtain a third message from the first AP 205. Upon receiving the third message, the second AP 205 can extract the CBF trigger 545 from the third message to obtain information and parameters associated with the first AP 205. Using the information, the second AP 205 can adjust timing, frequency, and control signals to synchronize with the first AP 205. For example, the second AP 205 can adjust the timing of the CDF PPDU based on scheduling consensus and the resources available to the STA 240 (e.g., station capability data 550). In another example, the second AP 205 can adjust the frequency of the CBF PPDU based on the AP capability data 555 and the station capability data 550. The CBF trigger 545 can further contain information about the preamble of the CBF PPDU. The second AP can include the information from the CBF trigger 545 in the preamble of the CBF PPDU to ensure that both APs transmit the same preamble for the CBF PPDU, enabling the STAs of both APs to correctly decode the preamble without errors.

[0142] The coordinated beamforming manager 525 or the CBF synchronizer 515 of the AP 205 can be configured to implement and manage CBF communications, including transmitting or receiving various CBF transmissions. For example, after the coordination or synchronization of the CBF TXOP, the AP 205 and the STA 240 can participate in CBF TXOP communications. These CBF transmissions can be implemented to include acknowledgments (e.g., ACK). For example, after transmitting a CBF PPDU, one or more acknowledgments (e.g., ACK) can be collected or requested from the AP1-STA and AP2-STA addressed by the transmitted CBF PPDU via one of the following methods. In one example, after the CBF PPDU, the ACK can be included in a single TB-PPDU transmitted simultaneously by both the AP1-STA and the AP2-STA. The TB PPDU can be requested by individual trigger frames or fields for each STA included in the CBF PPDU / transmission (e.g., within an A-MPDU addressed to the STA). The trigger content for the AP1-STA can be transmitted by AP1, and the trigger content for the AP2-STA can be transmitted by AP2. Each STA can occupy a different RU or spatial stream in the TB-PPDU, as specified by the trigger content it receives. The APs can signal or pre-negotiate with each other the RU or spatial stream allocated to each of the STAs from which they request an ACK.

[0143] For example, after a CBF PPDU, one or more ACKs can be sequentially requested in two TB PPDUs, one for AP1-STA and the other for AP2-STA. In one instance, the ACK from AP1-STA can be requested in TB-PPDU-1 immediately following the CBF transmission, where the individual trigger frame or field for requesting the ACK is included within the A-MPDU addressed to each AP1-STA in the CBF PPDU. The ACK from AP2-STA can be requested by a separate multi-user block acknowledgment request (MU-BAR) frame transmitted by AP2 after TB-PPDU-1, and the AP2-STA addressed by the MU-BAR responds by transmitting TB-PPDU-2 containing its ACK. In another variant, after the CBF PPDU, AP1 transmits a first MU-BAR requesting the ACK from AP1-STA, and AP1-STA responds by transmitting TB-PPDU-1. After TB-PPDU-1, AP2 transmits a second MU-BAR requesting the ACK from AP2-STA, and AP2-STA responds by transmitting TB-PPDU-2. Successive, adjacent, or neighboring frames in the above sequence can be separated by SIFS.

[0144] In various embodiments, the CBF request 525 or the CBF response 530 can be encapsulated as part of the ICF from AP1 or AP2, where the content of the CBF-req or CBF-resp is signaled within the user information field addressed with a specific pre-negotiated or predefined AID value. These user information fields can be processed by the AP and ignored by AP1-STA and AP2-STA. These fields can be signaled at the beginning of the ICF frame (e.g., after the common information and special user information fields). The CBF adjustment message (e.g., CBF-adj) can be included or encapsulated as part of the ICR message or a standalone frame. The format of the ICR message or the standalone frame can be a multi-STA block ACK (M-STA-BA). For any CBF-TXOP frame sequence, the participating AP1-STA and AP2-STA notified by the ICF can be requested to stay in the receive mode, where they are capable of receiving the CBF PPDU. If such a device does not receive the CBF PPDU or an indication of an upcoming PPDU (within the same TXOP) expected for the device during this time, then such a device can be allowed to exit the receive mode and transition to the listen mode (i.e., with a limited ability that may not allow receiving the CBF PPDU) after a predetermined or pre-negotiated duration from the reception of the ICF. The CBF-TXOP frame sequence disclosed herein can also be applied to other forms of multi-AP coordination that utilize concurrent transmissions across two or more BSSs, such as coordinated spatial reuse (CSR) and coordinated orthogonal frequency division multiple access (C-OFDMA).

[0145] Now refer to Figure 6 , and illustrate an example method 600 for multi-AP coordination that provides CBF. The method 600 can be implemented, for example, using one or more processors of a computing system configured via instructions and data stored in a memory to implement the configuration or synchronization of CBF operations in participating devices (e.g., access points (APs) and stations (STA240)). The method 600 can be implemented using, for example, system 200, system 500, or any of the features discussed in conjunction with Figures 1A to 5 . The method 600 can include actions 605 to 615. At 605, the method can include transmitting, by a first access point (AP), a first message to a second AP capable of participating in coordinated beamforming (CBF) and a first set of candidate stations of the first AP to initiate a transmission opportunity (TXOP) with an embedded CBF request. At 610, the method can include transmitting, by the second AP in response to the CBF request, a second message to the first AP and a second set of candidate stations of the second AP identified as participating in the TXOP with an embedded CBF response. At step 615, the method can include transmitting, by the first AP in response to receiving the CBF response that the second AP will participate in CBF, a third message with a CBF trigger to the second AP, the CBF trigger including information for synchronizing CBF transmissions to be communicated during the TXOP.

[0146] At 605, the method can include transmitting, by a first access point (AP), a first message to a second AP capable of participating in coordinated beamforming (CBF) and a first set of candidate stations of the first AP to initiate a transmission opportunity (TXOP) with an embedded CBF request. The first message (also referred to as Msg1) can include an initial control frame (ICF) generated by the first AP. The first AP can use the Msg1 (e.g., the first message) addressed to the first STA in the first AP STA and to the second AP to initiate the process of synchronizing the CBF TXOP via the CBF TXOP. During the initiation, the first AP can perform the functions of the ICF (e.g., MU-RTS / BSRP) for the first STA, such as for EMLSR, in-device coexistence (IDC), power saving, and other functions. The first AP can transmit additional signals to the first STA and the second AP that can participate in CBF transmissions during this TXOP.

[0147] The first AP may include or embed a "CBF-req" (e.g., CBF request) to signal the second AP about the information of the participating first STA and to request information about the second STA participating in the second AP. In some examples, padding may be included (e.g., as pre-negotiated by the first STA and / or the second AP with the first AP) to provide the first STA and the second AP with additional time to process the received frame and prepare for any response. The first STA and the second AP may transmit Msg2 (e.g., ICR) in response to Msg1. The ICR may be in TB-PPDU format (e.g., if the first AP needs to individually identify each device transmitting the ICR), or in non-HT DUP format.

[0148] The first STA addressed by Msg1 may transmit an ICR (e.g., CTS / BSR) in response to the ICF from the first AP, which indicates its availability or the duration of availability for the CBF TXOP (e.g., for IDC). The transmission of the response by the second AP may depend on: i) whether the second AP supports such capabilities (as pre-negotiated between the APs), or ii) whether the first AP requests a response from the second AP (e.g., in Msg1). If the second AP is capable and a response is requested, then the second AP may respond to the first AP with an ICR (e.g., as an acknowledgement of Msg1, or to reserve the medium, etc.). The transmission parameters of the second AP's response (e.g., MCS, Nss, RU allocation) may be pre-specified (e.g., as part of the ICF or Msg1, or via pre-negotiation between the first AP and the second AP).

[0149] If the second AP is able to respond with Msg2 (e.g., the second AP's initial control response or ICR), and the first AP requests such a response, but the second AP does not respond, then the second AP may implicitly notify the first AP that the second AP does not participate in the CBF of this TXOP (e.g., when doing so). For example, in response to the first AP not receiving an ICR of the ICF in response to the first message from the second AP within a predetermined time interval from sending the first message, the first AP may determine that the second AP does not participate in the CBF TXOP. Padding may be included in Msg2, which may: (i) provide the first AP with additional time to process the received frame (e.g., the first AP may specify a longer duration or length for Msg2 or ICR within Msg1 or ICF), or (ii) provide the second AP with additional time to prepare Msg3 (e.g., the second AP's CBF response to the first AP's Msg1). For example, the second AP may request a longer duration or length for Msg2 to be specified in Msg1 via pre-negotiation with the first AP.

[0150] At 610, the method may include the second AP transmitting a second message or Msg3. The second message may include an ICF (e.g., the ICF of the second AP for second AP STAs) for a second set of candidate stations addressed to the second AP that the second AP may request or invite to participate in the CBF TXOP. The second message may include an embedded CBF response addressed to the first AP in response to a CBF request (e.g., from the first AP). The second AP may transmit Msg3 (e.g., the ICF) to any candidate second STA in a set of candidate STAs identified by the second AP as participating in this TXOP (e.g., based on the presence of traffic, the applicability of CBF, etc.) and to the first AP. If the second STA is addressed by the second AP, then Msg3 performs the function of the ICF for those STAs. In some instances, the second AP may not have a second set of candidate stations identified as participating in this TXOP (e.g., (i) if the second AP does not have any pending downlink traffic for its stations, or (ii) if the downlink CSI of the STAs corresponding to either AP is not available at the second AP). In such a case, the second AP may include only the CBF response addressed to the first AP in the second message and not include any ICF addressed to second AP STAs.

[0151] Msg3 (e.g., the CBF response) may embed information of the first AP regarding the participating second STAs. In some examples, Msg3 (e.g., the CBF response) may signal that the second AP does not participate in the CBF (e.g., if there are no identified participating second STAs). Padding may be included (e.g., as pre-negotiated by the second STA and / or the first AP and the second AP) to provide additional time for any addressed second STAs and the first AP to process the received frame and prepare for any response.

[0152] The first AP may transmit Msg4 (e.g., an initial control response (ICR)) to the second AP. Msg4 may be generated and transmitted in TB-PPDU format (e.g., if the second AP is going to individually identify each device transmitting the ICR), or in non-HT DUP format. If any second AP STA is addressed by Msg3, then the second AP STA may respond to Msg4 with the ICR, which may indicate its availability or the duration of availability for the CBF TXOP (e.g., for IDC). The transmission of the response by the first AP may depend on one or more factors, such as whether the first AP supports such a capability (as pre-negotiated between the APs), or whether the second AP requests such a response from the first AP (e.g., in Msg3). If the first AP is capable and the response is requested by the second AP, then the first AP may respond to the second AP with the ICR (e.g., as an acknowledgement of Msg3, or to reserve the medium, etc.).

[0153] The transmission parameters required for the response of the first AP in Msg4 may include, for example, MCS, Nss, RU allocation, and other data. These parameters may be pre-specified (e.g., as part of Msg3), or specified via prior negotiation between the first AP and the second AP. Padding may be included within the message transmission (i.e., Msg4), and the padding may provide the second AP with additional time to process the received frame (e.g., the second AP may specify a longer duration or length for Msg4 in Msg3), or provide the first AP with additional time to prepare Msg5 (e.g., the first AP may request, via prior negotiation with the second AP, a longer duration or length for Msg4 in Msg3).

[0154] At step 615, the method may include transmitting a third message or Msg5 from the first AP to the second AP. The third message may have a CBF trigger, which includes information for synchronizing the CBF transmission to be communicated during the TXOP. In response to receiving a CBF response from the second AP indicating that the second AP will participate in the CBF, the third message may be transmitted to the second AP. The third message may indicate termination / abort of the CBF transmission.

[0155] If the second AP indicates participation in the CBF in the CBF-resp, then the first AP may transmit Msg5, which may include a CBF trigger message. The CBF trigger message may be sent to the second AP or all participating devices (e.g., STAs and APs). The CBF trigger may signal the preamble content of the CBF transmission and may allow the second AP to synchronize the CBF transmission with the first AP. For example, the CBF trigger may provide information about the timing of the CBF transmission, such as aligning the start time of the CBF PPDU, estimating and compensating for the frequency offset of the second AP relative to the first AP, the time slots of each of the participating STAs, and other information for completing the CBF transmission. In some examples, the first AP may signal termination / abort of the CBF transmission or the CBF TXOP (e.g., based on ICR feedback from the first STA indicating that one or more first STAs are not available for part or all of this TXOP due to IDC requirements). This may be an implicit notification, where the first AP does not transmit the CBF trigger (e.g., the first AP may transmit other frames instead of the CBF trigger, or transmit nothing). Padding may be included (e.g., as pre-negotiated between the first AP and the second AP) to provide the second AP with additional time to process the received frame.

[0156] If the first AP transmits a Msg5 indicating that the CBF transmission has not been terminated / aborted, then the CBF PPDU transmission can be initiated after Msg5. The first AP and the second AP can transmit the CBF PPDU. The first AP and the second AP can signal the same preamble content in the CBF PPDU to ensure correct decoding at the STA of any AP. If any second STA is not available for the entire duration of the CBF TXOP (e.g., as indicated by Msg4), then the second AP can: (i) replace any expected payload of the STA with a frame end (EOF) padding, or (ii) choose not to transmit any payload to the STA, or (iii) choose not to transmit the CBF PPDU at all. The preamble of the CBF-PPDU can signal the content expected for the STA (e.g., as transmitted by the first AP). If any second STA is not available outside the initial duration of the CBF PPDU (e.g., as indicated by Msg4), then the second AP can shorten the expected payload of the STA to occupy the initial duration and fill the remaining duration of the CBF PPDU of the STA with EOF. The successive transmissions in method 600 can be separated by the duration of a short inter-frame space (i.e., SIFS).

[0157] In some aspects, the technical solution of the present disclosure can include per-CBF TXOP frame multi-access coordination using a scheduling consensus that is initially established and then adjusted based on CBF-adj messages from the AP and ICR messages from the STA. For example, the technical solution can utilize an initial control frame (ICF) sent by the first (e.g., initiating) AP to the second AP and to the stations (STAs) of the first AP to initiate CBF synchronization. The STA of the first AP can respond to this ICF with its initial control response (ICR), while the second (e.g., responding) AP can send the CBF response together with the ICF of the STA of the second AP, thus allowing a preliminary consensus to be reached between the first AP and the second AP regarding the scheduling and determination of CBF communication, including information about the STAs that these APs are expected to participate in, and all of this can be done before receiving the ICR from the STA.

[0158] Then, the STAs of the second AP can reply to the ICF of the second AP with their ICRs. The first AP and the second AP can each receive and process the information of the ICRs from their respective STAs, and determine their own adjustments based on this information, including canceling participation in the CBF or making any other adjustments before sending the CBF trigger. The information of the ICRs from the first and second AP STAs can be used by the first AP to generate an updated schedule and determine to coordinate or synchronize the CBF transmission. Then, the first AP can generate a CBF trigger, which can include updated information, including updated information about the participating STAs, its updated parameters, and the scheduled time for initiating and implementing the CBF PPDU transmission in the device.

[0159] Now refer to Figure 7 , an example method 700 for multi-AP coordination providing CBF is described. Method 700 can be implemented, for example, to implement a configuration for CBF operations or CBF settings. Method 700 can be implemented using, for example, system 200, system 500, or any of the features discussed in conjunction with Figures 1A to 5 Method 700 can include actions 705 to 720. At step 705, the method can include transmitting a first message to a first group of candidate stations of a second AP and a first AP capable of participating in coordinated beamforming (CBF) to initiate a transmission opportunity (TXOP) with an embedded CBF request. At step 710, the method can include receiving, in response to the first message, one or more indications corresponding to the availability of one or more first stations in the first group of candidate stations to participate in the TXOP. At step 715, the method can include transmitting an adjusted first message to the second AP in response to the one or more indications to initiate the TXOP according to the embedded adjusted CBF request. At step 720, the method can include receiving, in response to the first AP not terminating the TXOP via the adjusted first message, a second message from the second AP, the second message including an adjusted CBF response to the adjusted first message, the second message including information about a second group of candidate stations of the second AP. At step 725, the method can include transmitting a third message with a CBF trigger to the second AP in response to the second AP indicating participation in the TXOP via the second message, the CBF trigger including information for synchronizing the CBF transmissions to be conveyed during the TXOP.

[0160] At step 705, the method may include transmitting a first message or Msg1 to a second AP and a first set of candidate stations of the first AP to initiate a transmission opportunity (TXOP) with an embedded coordinated beamforming (CBF) request (CBF-req). The second AP may be an AP capable of participating in coordinated beamforming (CBF). The first set of candidate stations of the first AP (i.e., the first STAs) may be STAs of the first AP, and the first AP may select the STAs as potential participants in the CBF TXOP based on previous information or data (e.g., availability of downlink CSI, channel characteristics, presence of downlink queued traffic, or traffic characteristics).

[0161] The first AP may initiate the CBF TXOP using Msg1 (e.g., the first message or ICF of the first AP), and the Msg1 may be addressed to the first STAs and to the second AP. During the initiation, the first message of the first AP may include or perform the function of the ICF (e.g., MU-RTS / BSRP) of the first STAs. For example, the first message may correspond to or include information about EMLSR, IDC, power saving, and other functions. The first AP may transmit additional signals to the first STAs and the second AP that may participate in the CBF transmission during this TXOP.

[0162] The first AP may embed a "CBF-req" (e.g., CBF request) in Msg1 for the second AP to signal information to the participating first STAs and may request information about the participating second STAs. In some examples, padding (e.g., pre-negotiated by the first STAs and / or the second AP with the first AP) may be included to provide the first STAs and the second AP with additional time to process the received frame and prepare for any response. The first STAs and the second AP may transmit Msg2 (e.g., ICR) in response to Msg1 (e.g., ICF). The ICR may be generated or transmitted in a TB-PPDU format (e.g., the first AP may individually identify each device transmitting the ICR) or in a non-HT DUP format.

[0163] At step 710, the method may include receiving, in response to the first message, one or more indications from a first set of candidate stations, the indications corresponding to the availability of one or more first stations in the first set of candidate stations to participate in a TXOP. The first STA and the second AP addressed by Msg1 may transmit Msg2 including an ICR (e.g., CTS / BSR) in response to the ICF from the first AP, which indicates the availability or the duration of the availability for the CBF TXOP (e.g., for the IDC). In some examples, the non - transmission of an ICR by one or more first STAs in response to the ICF from the first AP may indicate the unavailability of the one or more first STAs for the CBF TXOP. The transmission of the response by the second AP may depend on one or more factors, such as whether the second AP supports such capabilities (e.g., as pre - negotiated between the APs), or whether the first AP requests a response from the second AP (e.g., in Msg1). If the second AP is capable and a response is requested, then the second AP may respond to the first AP with an ICR (e.g., as an acknowledgement of Msg1, or to reserve the medium, etc.). The transmission parameters required for the response of the second AP may include data, such as the values of MCS, Nss, RU allocation, and other parameters, which may be pre - specified (e.g., as part of Msg1, or via prior negotiation between the first AP and the second AP).

[0164] If the second AP is capable of responding with Msg2 and such a response is requested by the first AP, but the second AP does not respond, then the second AP may implicitly inform the first AP that the second AP does not participate in the CBF of this TXOP (e.g., by not responding within a predetermined time interval). Padding may be included in Msg2, which provides the first AP with additional time to process the received frame (e.g., the first AP may specify a longer duration or length for Msg2 in Msg1), or provides the second AP with additional time to prepare Msg3 (e.g., the second AP may request, via prior negotiation with the first AP, a longer duration or length for Msg2 in Msg1).

[0165] The second AP may transmit Msg3 addressed to the first AP (e.g., CBF response) and any second STA in a set of candidate STAs identified by the second AP as participating in this TXOP (e.g., based on the presence of traffic, the availability of downlink CSI, the applicability of CBF). If the second STA is addressed by the second AP, then Msg3 performs the function of an ICF for those STAs.

[0166] Msg3 can be embedded in the CBF response (CBF-resp) for the first AP to signal information about the participating second AP STAs. In some examples, the second AP can signal in the CBF response that the second AP does not participate in the CBF (e.g., if no participating second STA is identified in the message). Padding can be included (e.g., as pre-negotiated by the second STA and / or the first AP with the second AP) to provide additional time for any addressed second STAs and the first AP to process the received frame and prepare for any response.

[0167] At step 715, the method can include the first AP transmitting an adjusted first message to the second AP in response to one or more indications of a first set of candidate STAs or a CBF response from the second AP to initiate a TXOP according to the embedded adjusted CBF request. The first AP can transmit Msg4 (e.g., CBF adjustment or CBF-adj) to the second AP. Msg4 can be in TB-PPDU format (e.g., if the second AP needs to individually identify each transmitting device), or in a non-HT DUP format. If any second STA is addressed by Msg3, then the second STA can respond with an ICR using Msg4, which indicates the availability or duration of availability of the CBF TXOP (e.g., for IDC). The transmission of the response by the first AP can depend on whether the first AP supports such capabilities (as pre-negotiated between the APs), or whether the second AP requests such a response from the first AP (e.g., in Msg3). If the second AP is capable and requests a response, then the first AP can respond to the second AP with an ICR (e.g., as an acknowledgement of Msg3, or reservation of the medium, etc.).

[0168] The transmission parameters of the response of the first AP can be pre-specified (e.g., MCS, Nss, RU allocation, etc.) (e.g., as part of Msg3, or via prior negotiation between the first AP and the second AP). Padding can be included, which can provide additional time for the second AP to process the received frame (e.g., the second AP can specify a longer duration or length for Msg4 in Msg3).

[0169] The second AP can transmit Msg3 addressed to any candidate second STA in a set of candidate STAs identified as participating in this TXOP (e.g., based on the presence of traffic, availability of downlink CSI, applicability of CBF, etc.) and to the first AP. If a second STA is addressed by the second AP, then Msg3 performs the function of ICF for those STAs.

[0170] Msg3 can be embedded or contain the CBF response of the first AP (e.g., CBF-resp), which can signal information about the participating second AP STA. In some examples, the CBF response can signal that the second AP did not participate in the CBF (e.g., if no participating second STA is identified). Padding (e.g., as pre-negotiated by the second STA and / or the first AP with the second AP) can be included to provide additional time for any addressed second STA and the first AP to process the received frame and prepare for any response.

[0171] The first AP can transmit Msg4 (e.g., CBF adjustment) to the second AP. Msg4 can be in TB-PPDU format (e.g., if the second AP needs to individually identify each transmitting STA), or in non-HT DUP format. If any second STA is addressed by Msg3, then the second STA can respond with Msg4 using ICR, which indicates the availability or duration of availability for the CBF TXOP (e.g., for IDC). The transmission of a response by the first AP may depend on whether the first AP supports such an ability (as pre-negotiated between the APs), or whether the second AP requests such a response from the second AP (e.g., in Msg3). If the second AP is capable and requests a response, then the first AP can respond to the second AP with ICR (e.g., as an acknowledgement of Msg3, or reservation of the medium, etc.).

[0172] The transmission parameters (e.g., MCS, Nss, RU allocation) of the response of the first AP in Msg4 can be pre-specified (e.g., as part of Msg3, or via prior negotiation between the first AP and the second AP). Padding can be included, which can provide additional time for the second AP to process the received frame (e.g., the second AP can specify a longer duration or length for Msg4 in Msg3).

[0173] The second STA and the first AP can transmit Msg4. If the transmissions from different STAs or APs can contain different information (e.g., when the first AP transmits Msg4 with CBF-adj), or when the second AP needs to identify each transmitting STA, then Msg4 can be transmitted in TB-PPDU format. However, Msg4 can be transmitted in non-HT DUP format. The format of Msg4 can be specified in Msg3.

[0174] If the second STA is addressed via Msg3 (e.g., ICF or CBF response of an AP2 STA), then the second STA may respond with Msg4 containing an ICR that indicates the availability or the duration of the availability for the CBF TXOP (e.g., for an IDC). The decision of whether the first AP transmits Msg4 may be communicated dynamically via prior signaling within the TXOP (e.g., in Msg1), or via prior negotiation between the first AP and the second AP. The content of Msg4 transmitted by the first AP to the second AP may include a CBF-adj to signal any adjustment to the information contained in the CBF-req based on the ICR received from the first STA or the CBF-resp in Msg2 received from the second AP. The type of adjustment may include at least one of the following: no change to the content signaled in the CBF-req, abort / terminate the CBF for this TXOP, reduce the maximum payload duration or the maximum duration of the CBF TXOP (e.g., due to the IDC of the first STA or the CBF-resp of the second AP), or discard some of the first STAs from the content signaled in the CBF-req (e.g., due to the indicated unavailability from an IDC requirement, missing ICR in Msg2, etc.).

[0175] The type of adjustment allowed in the CBF-adj in Msg4 may be pre-negotiated between the first AP and the second AP. For example, the CBF-adj in Msg4 may be limited to signaling only "no change to the content signaled in the CBF-req" or "abort / terminate the CBF for this TXOP". Msg4 may further indicate whether Msg5 is requested from the second AP. Padding may be included (e.g., the second AP may request a longer duration or length for Msg4 in Msg3), and the padding may provide the second AP with additional time to process the received frame.

[0176] At step 720, the method may include receiving, from a second AP, a second message (e.g., Msg5) in response to the first AP not terminating the TXOP via the adjusted first message, the second message including an adjusted CBF response (e.g., CBF-adjust or CBF-adj) to the adjusted first message, the second message including information about a second set of candidate stations of the second AP. If the first AP does not indicate in Msg4 that the CBF TXOP is aborted or terminated, the second AP may transmit Msg5 to the first AP based on, for example, a previous request from the first AP (e.g., in Msg4 or Msg1), the presence of Msg4 from the first AP, or a previous negotiation between the first AP and the second AP. Msg5 may include CBF-adj to signal any adjustments to the information in the CBF-resp included in Msg3 based on the ICR received from the second STA in Msg4. Possible adjustments may include at least one of the following: not changing the content signaled in the CBF-resp, aborting / terminating the CBF of this TXOP, reducing the maximum payload duration or the maximum CBF-TXOP duration (e.g., due to the IDC of the second STA), or discarding some of the second STAs from the content signaled in the CBF-resp (e.g., due to the indicated unavailability from the IDC requirement, missing ICR in Msg4, etc.).

[0177] The types of adjustments allowed by the CBF-adj in Msg5 may be pre-negotiated between the first AP and the second AP. For example, the CBF-adj in Msg5 may be limited to signaling only "not changing the content signaled in the CBF-resp" or "aborting / terminating the CBF of this TXOP". Padding (e.g., as pre-negotiated between the first AP and the second AP) may be included to provide the first AP with additional time to process the received frame and prepare for Msg6.

[0178] At step 725, the method may include the first AP transmitting a third message (e.g., Msg6) with a CBF trigger to the second AP in response to the second AP indicating participation in the TXOP, the CBF trigger including information for synchronizing CBF transmissions to be conveyed during the TXOP. If the CBF TXOP has not been aborted / terminated by the first AP or the second AP in a previous message (e.g., in Msg3, Msg4, or Msg5), then the first AP may transmit Msg6 containing the CBF trigger to the second AP. Msg6 may signal the preamble content for the CBF transmission and enable the second AP to synchronize with the first AP (e.g., align the start time of the CBF PPDU, estimate and compensate for the frequency offset of the second AP relative to the first AP, etc.). Padding (e.g., as pre-negotiated between the first AP and the second AP) may be included to provide the second AP with additional time to process the received frame and prepare for the upcoming transmission. The first AP and the second AP may initiate CBF PPDU transmissions with the same preamble content after Msg6 to ensure correct decoding at the participants (e.g., APs and STAs) of the CBF TXOP. Successive transmissions in method 700 may be separated by the duration of a short inter-frame space (i.e., SIFS).

[0179] References to "or" may be construed as inclusive, such that any term described using "or" may indicate any of a single, more than one, and all of the described terms. References to at least one of a list of terms may be construed as inclusive or to indicate any of a single, more than one, and all of the described terms. For example, a reference to "at least one of 'A' and 'B'" may include only 'A', only 'B', and both 'A' and 'B'. Such references used in conjunction with "comprising" or other open terms may include additional items.

[0180] Note that, for purposes of identifying or distinguishing one from another or others, certain paragraphs of the present disclosure may refer to terms such as "first" and "second" with respect to subsets of transmitted spatial streams, sounding frames, responses, and devices. These terms are not intended to associate entities (e.g., a first device and a second device) solely in terms of time or in accordance with a sequence, but in some cases, the entities may include such a relationship. These terms also do not limit the number of possible entities (e.g., STAs, APs, beamformers, and / or beamformeess) that may operate in a system or environment. It should be understood that the above system may provide multiple ones of any or each of those components, and these components may be provided on a single machine or, in some embodiments, on multiple machines in a distributed system. Additionally, bit field positions may vary, and multi-bit words may be used. Further, the above system and method may be provided as one or more computer-readable programs or executable instructions embodied on or in one or more articles of manufacture (e.g., floppy disk, hard disk, CD-ROM, flash memory card, PROM, RAM, ROM, or magnetic tape). The program may be implemented in any programming language (e.g., LISP, PERL, C, C++, C#) or in any byte code language (e.g., JAVA). The software program or executable instructions may be stored as object code on or in one or more articles of manufacture.

[0181] Although the written description of the methods and systems above enables one of ordinary skill in the art to make and use embodiments thereof, one of ordinary skill in the art will understand and appreciate that there are variations, combinations, and equivalents to the specific embodiments, methods, and examples herein. Accordingly, the methods and systems of the present disclosure should not be limited by the above embodiments, methods, and examples, but rather should be limited by all embodiments and methods within the scope and spirit of the present disclosure.

Claims

1. A system, comprising: A first access point AP configured to: Transmit a first message to a second AP capable of participating in coordinated beamforming CBF and a first group of candidate stations of the first AP to initiate a transmission opportunity TXOP with an embedded CBF request; Wherein the second AP is configured to: In response to the CBF request, transmit a second message to the first AP and a second group of candidate stations of the second AP identified as participating in the TXOP with an embedded CBF response; Wherein the first AP, in response to receiving the CBF response that the second AP will participate in CBF, transmits a third message with a CBF trigger to the second AP, the CBF trigger including information for synchronizing CBF transmissions to be conveyed during the TXOP.

2. The system according to claim 1, wherein the first AP is configured to include in the CBF request a list of identifiers of the first group of candidate stations participating in CBF and information about the proposed number of spatial streams in the CBF transmissions for each station in the first group of candidate stations.

3. The system according to claim 2, wherein the CBF response of the second AP includes a list of identifiers of the second group of candidate stations participating in CBF and the proposed number of spatial streams in the CBF transmissions for each station in the second group of candidate stations for the first AP to determine the schedule for the CBF transmissions.

4. The system according to claim 1, wherein the first AP is configured to, in response to the first message, receive from one or more stations in the first group of candidate stations information about the availability of participating in the TXOP and information about the duration of the availability in the TXOP of the one or more stations in the first group of candidate stations, and wherein the first AP is configured to determine at least one of the following based on the information about availability and the information about duration: the ability of the first AP to participate in CBF during the TXOP, or a first group of stations from the first group of candidate stations of the first AP participating in CBF during the TXOP, or the maximum duration of the first AP participating in CBF during the TXOP.

5. The system according to claim 4, wherein the first AP is configured to include in the third message an indication of at least one of the following: the ability of the first AP to participate in CBF during the TXOP, the first group of stations of the first AP participating in CBF during the TXOP, or the maximum duration of the first AP participating in CBF during the TXOP.

6. The system according to claim 1, wherein the first AP is configured to include in the CBF trigger information one or more of the timing of transmission of the preamble of the physical protocol data unit PPDU for synchronizing the CBF transmissions to be conveyed during the TXOP or the content of the preamble.

7. The system according to claim 1, wherein the first AP is configured to include padding in the first message to provide a time interval for at least one of the second AP or the at least one station to process the information contained in the first message before generating one or more responses regarding the availability of at least one of the second AP or the first group of candidate stations to participate in CBF.

8. The system according to claim 1, wherein the second AP is configured to transmit a preliminary CBF response indicating the participation of the second AP to the first access point before receiving information regarding the availability of the second group of candidate stations.

9. The system according to claim 1, wherein the first AP determines a schedule for transmitting data of one or more stations in the first group of candidate stations during the TXOP before receiving information regarding the availability of the second group of candidate stations.

10. The system according to claim 9, wherein after receiving the CBF response from the second AP, the first AP adjusts the schedule in response to a message transmitted by the second AP, the message including the information regarding the second group of candidate stations.

11. A system, comprising: A first access point AP, configured to: Transmit a first message to a second AP capable of participating in coordinated beamforming CBF and a first group of candidate stations of the first AP to initiate a transmission opportunity TXOP with an embedded CBF request; Receive one or more indications from the first group of candidate stations in response to the first message, the indications corresponding to the availability of one or more first stations in the first group of candidate stations to participate in the TXOP; Transmit an adjusted first message to the second AP in response to the one or more indications to initiate the TXOP according to an embedded adjusted CBF request; Receive a second message from the second AP in response to the first AP not terminating the TXOP via the adjusted first message, the second message including an adjusted CBF response to the adjusted first message, the second message including information regarding a second group of candidate stations of the second AP; And Transmit a third message with a CBF trigger to the second AP in response to the second AP indicating participation in the TXOP via the second message, the CBF trigger including information for synchronizing CBF transmissions to be communicated during the TXOP.

12. The system according to claim 11, wherein the first AP is configured to: Determine that a first subset of the one or more first stations is not available to participate in the TXOP and a second subset of the one or more first stations is available to participate in the TXOP based on the one or more indications; and Generate an adjusted CBF request in response to the determination, the adjusted CBF request indicating the second subset of the one or more first stations as participating in the TXOP.

13. The system according to claim 12, wherein the one or more indicators are received via at least one of a trigger-based physical protocol data unit (TB-PPDU) format or a non-high throughput duplicate transmission (non-HT DUP) format.

14. The system according to claim 11, wherein the first AP is configured to: receive the one or more indications corresponding to the availability of the one or more first stations for one or more durations; and determine the availability of the one or more first stations based on the one or more durations.

15. The system according to claim 11, wherein the first AP is configured to include padding in the first message to provide additional time for the first group of candidate stations to generate information about the availability to participate in CBF during the TXOP.

16. A method, comprising: transmitting, by a first access point (AP), a first message to a second AP capable of participating in coordinated beamforming (CBF) and a first group of candidate stations of the first AP to initiate a transmission opportunity (TXOP) with an embedded CBF request; transmitting, by the second AP, a second message to the first AP and a second group of candidate stations of the second AP identified as participating in the TXOP in response to the CBF request with an embedded CBF response; transmitting, by the first AP, a third message with a CBF trigger to the second AP in response to receiving the CBF response that the second AP will participate in CBF, the CBF trigger including information for synchronizing CBF transmissions to be communicated during the TXOP.

17. The method according to claim 16, comprising: including, by the first AP, a list of identifiers of the first group of candidate stations for participating in the CBF and information about the proposed number of spatial streams in the CBF transmission for each station in the first group of candidate stations in the CBF request.

18. The method according to claim 17, comprising: including, by the second AP, a list of identifiers of the second group of candidate stations for participating in the CBF and the proposed number of spatial streams in the CBF transmission for each station in the second group of candidate stations in the CBF response from the second AP; and and determining, by the first AP, a schedule for the CBF transmission.

19. The method according to claim 16, comprising: receiving, by the first AP, from one or more stations in the first group of candidate stations information about the availability to participate in the TXOP or information about the duration of the availability in the TXOP for the one or more stations in the first group of candidate stations in response to the first message; and and determining, by the first AP, at least one of the following based on the information about availability or the information about duration: the ability of the first AP to participate in CBF during the TXOP, or a first group of stations from the first group of candidate stations of the first AP that participate in CBF during the TXOP, or the maximum duration for the first AP to participate in CBF during the TXOP.

20. The method according to claim 19, comprising: including, by the first AP, an indication of at least one of the following in the third message: the ability of the first AP to participate in CBF during the TXOP, the first set of stations of the first AP participating in CBF during the TXOP, or the maximum duration for which the first AP participates in CBF during the TXOP.

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