Systems, methods, and apparatus for multiple access point (multi-AP) coordination in a wireless local area network (WLAN)

Abstract

To provide a method and apparatus for a single station (STA) to discover and associate with multiple access points (APs).SOLUTION: At a multiple AP association 800 during the STA association, the STA receives from the first AP a probe response frame including one or more indicators indicating multiple AP operation capabilities of the first AP and the second AP, and transmits to at least one of the first AP or the second AP a multiple AP association request frame enabling the first AP to be associated with the second AP for multiple AP operation; A first multiple AP association response frame indicating permission or denial of multiple AP operation with the first AP is received from the first AP, and a second multiple AP association response frame indicating permission or denial of multiple AP operation with the second AP is received from the second AP.SELECTED DRAWING: Figure 8A

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 873,396, filed July 12, 2019, U.S. Provisional Patent Application No. 62 / 815,130, filed March 7, 2019, U.S. Provisional Patent Application No. 62 / 790,738, filed January 10, 2019, and U.S. Provisional Patent Application No. 62 / 757,507, filed November 8, 2018, the contents of which are incorporated herein by reference. [Background technology]

[0002] background In existing wireless networks (e.g., WLANs) implemented according to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, a station (STA) can send an association request to an access point (AP) with which it wishes to associate to establish a suitable connection. If elements of the association request match the capabilities of the AP, the AP sends an association response to the STA, indicating that the STA is a member of a basic service set (BSS) associated with the AP. In existing wireless networks, a STA only exchanges request and response frames to associate with a single AP, and no support is provided for multiple AP discovery and association from a single STA. Therefore, there is a need for a method and apparatus that enables a single STA to discover and associate with multiple APs. Summary of the Invention

[0003] overview

[0003] This specification describes systems, methods, and devices for multiple AP (or multi-AP) cooperation in a wireless local area network (WLAN). For example, a station (STA) may receive a probe response frame from a first access point (AP) that includes one or more indicators indicating the multiple AP operation capabilities of the first AP and a second AP. The multiple AP operation capabilities may include multiple AP joint transmission capability, multiple AP hybrid automatic repeat request (HARQ) capability, multiple AP multiple input / output (MIMO) capability, dynamic AP selection capability, multiple AP roaming capability, or multiple AP cooperative beamforming capability. The STA may then transmit a multiple AP association request frame to at least one of the first AP or the second AP that enables the first AP to associate with the second AP for multi-AP operation with the STA. The multi-AP operation may include receiving signals by the STA from the first AP and the second AP, for example, using cooperative orthogonal frequency division multiple access (OFDMA) or cooperative nulling. Upon transmitting the multiple AP association request frame, the STA may receive a first multiple AP association response frame from the first AP indicating permission or denial of multiple AP operation with the first AP. The STA may also receive a second multiple AP association response frame from the second AP indicating permission or denial of multiple AP operation with the second AP. Provided that both the first multiple AP association response frame and the second multiple AP association response frame indicate permission, the STA may perform multiple AP operation with the first AP and the second AP.

[0004] BRIEF DESCRIPTION OF THE DRAWINGS A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, in which like reference numerals refer to similar elements and in which: [Brief explanation of the drawings]

[0005] [Figure 1A] FIG. 5 is a system diagram illustrating an example of a communication system in which one or more disclosed embodiments may be implemented. [Figure 1B]

[0006] 1B is a system diagram illustrating an example of a wireless transmit / receive unit (WTRU) that may be used within the communication system shown in FIG. 1A, according to one embodiment. [Figure 1C]

[0007] 1B is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 1D]

[0008] 1B is a system diagram illustrating a further example of a RAN and a further example of a CN that may be used within the communication system shown in FIG. 1A, according to one embodiment. [Figure 2]

[0009] FIG. 1 illustrates an example of cooperative orthogonal frequency division multiple access (OFDMA). [Figure 3]

[0010] FIG. 1 illustrates an example of resource allocation for cooperative OFDMA. [Figure 4]

[0011] FIG. 1 illustrates an example of cooperative nulling / cooperative beamforming. [Figure 5]

[0012] FIG. 1 illustrates an example of cooperative nulling / cooperative beamforming (CB / CN) using interference alignment. [Figure 6]

[0013] FIG. 1 illustrates an example of single-user joint pre-coded multiple access point (multi-AP) transmission, or cooperative single-user (SU) beamforming. [Figure 7]

[0014] FIG. 1 illustrates an example of multi-user joint pre-coded multiple AP transmission, or cooperative multi-user (MU) beamforming. [Figure 8A]

[0015] FIG. 1 illustrates an example of multiple AP association during station (STA) association. [Figure 8B]

[0016] FIG. 10 illustrates an example of a multiple AP association procedure. [Figure 9]

[0017] FIG. 1 illustrates an example of a STA-initiated multi-AP association. [Figure 10]

[0018] FIG. 1 illustrates an example of a multi-AP service set (SS) element. [Figure 11]

[0019] FIG. 10 illustrates an example of a multiple AP selection element. [Figure 12]

[0020] FIG. 1 illustrates an example of scheduled / random access cooperative OFDMA. [Figure 13]

[0021] FIG. 1 is a signaling diagram illustrating an example of multiple AP association, cell center / cell edge discovery, and data transmission. [Figure 14]

[0022] FIG. 1 illustrates an example of a guard band for fractional coordinated OFDMA. [Figure 15]

[0023] A diagram showing an example of downlink-downlink CB / CN. [Figure 16]

[0024] A diagram showing an example of uplink-uplink CB / CN. [Figure 17]

[0025] A diagram showing an example of an uplink-downlink CB / CN. [Figure 18]

[0026] FIG. 1 illustrates an example of a singling flow for independent Null Data Packet Announcement (NDPA) / Null Data Packet (NDP) and trigger-based feedback. [Figure 19]

[0027] FIG. 1 is a signaling diagram showing an example of master trigger-based NDPA / NDP and master trigger-based feedback. [Figure 20]

[0028] FIG. 10 is a signaling diagram illustrating an example of an NDP feedback request from an AP. [Figure 21]

[0029] FIG. 10 is a signaling diagram illustrating an example of an NDP trigger for implicit multi-AP sounding. [Figure 22]

[0030] FIG. 1 is a signaling diagram illustrating an example of independent NDPA / NDP for uplink-uplink (UL / UL) CB / CN based on reciprocity. [Figure 23]

[0031] FIG. 1 is a signaling diagram illustrating an example of a master trigger-based NDPA / NDP for a UL / UL CB / CN. [Figure 24]

[0032] FIG. 1 is a signaling diagram illustrating an example of STA-initiated channel acquisition. [Figure 25]

[0033] FIG. 1 is a signaling diagram illustrating an example of AP-initiated channel acquisition. [Figure 26]

[0034] FIG. 1 illustrates an example of implicit DL channel acquisition. [Figure 27]

[0035] FIG. 1 illustrates interference in an example scenario where UL and DL traffic occur simultaneously. [Figure 28]

[0036] FIG. 10 is a diagram showing an example of using a mesh data trigger (MDT) frame and a mesh sounding trigger (MST) frame for CB / CN. [Figure 29]

[0037] FIG. 1 illustrates an example of uplink-uplink CB / CN using unidirectional spatial reuse parameter (SRP) based spatial reuse (SR). [Figure 30]

[0038] FIG. 1 illustrates an example of type 1 of sparse code multiple access (SCMA) gain estimation. [Figure 31]

[0039] FIG. 10 is a diagram illustrating an example of Type 2 of SCMA gain estimation. [Figure 32]

[0040] A diagram showing an example of uplink-uplink bidirectional SRP-based SR. [Figure 33]

[0041] FIG. 1 illustrates an example of a unidirectional DL / UL CB / CN with primary UL / DL transmission. [Figure 34]

[0042] FIG. 1 illustrates an example of multi-master triggering. [Figure 35]

[0043] FIG. 1 illustrates an example of sequential triggering. [Figure 36]

[0044] FIG. 1 illustrates an example of presounding-based master triggering. [Figure 37]

[0045] FIG. 1 illustrates an example of a long training field (LTF) structure for AP1 and AP2 for interference alignment (IA). [Figure 38]

[0046] FIG. 1 illustrates an example of a multi-AP implicit sounding procedure with sounding frames. [Figure 39]

[0047] FIG. 1 illustrates an example procedure for self-calibration. DETAILED DESCRIPTION OF THE INVENTION

[0006] Detailed Description

[0048] 1A illustrates an example of a communication system 100 in which one or more disclosed embodiments can be implemented. The communication system 100 may be a multiple-access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content by sharing system resources, including wireless bandwidth. For example, the communication system 100 may use one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailed unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), etc.

[0007]

[0049] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RANs 104 / 113, CNs 106 / 115, public switched telephone networks (PSTNs) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a “station” and / or “STA,” may be configured to transmit and / or receive wireless signals and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, mobile phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspot or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearable items, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated process chains), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as a UE.

[0008]

[0050] The communications system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the CN 106 / 115, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode-B, a Home Node-B, a Home eNode-B, a gNB, an NR Node-B, a site controller, an access point (AP), a wireless router, etc. While the base stations 114a, 114b are each shown as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0009]

[0051] The base station 114a may be part of the RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or base station 114b may be configured to transmit and / or receive radio signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a particular geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, one for each sector of the cell. In one embodiment, the base station 114a may use multiple input / output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming can be used to transmit and / or receive signals in desired spatial directions.

[0010]

[0052] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0011]

[0053] More specifically, as noted above, the communication system 100 may be a multiple-access system and may use one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base stations 114a and WTRUs 102a, 102b, 102c in the RAN 104 / 113 may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115 / 116 / 117 using Wideband CDMA (WCDMA). WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0012]

[0054] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0013]

[0055] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as New Radio (NR) radio access, which may establish the air interface 116 using NR.

[0014]

[0056] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may jointly implement LTE radio access and NR radio access, e.g., using the principle of dual connectivity (DC). Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by transmissions sent to and from multiple types of radio access technologies and / or multiple types of base stations (e.g., eNBs and gNBs).

[0015]

[0057] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology such as IEEE 802.11 (e.g., Wireless Fidelity (WiFi)), IEEE 802.16 (e.g., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), or the like.

[0016]

[0058] 1A may be, for example, a wireless router, a Home Node B, a Home eNode B, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity within a local area, such as a business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or femtocell. 1A, the base station 114b may have a direct connection to the Internet 110. Therefore, the base station 114b may not need to access the Internet 110 via the CN 106 / 115.

[0017]

[0059] The RAN 104 / 113 may communicate with the CN 106 / 115, which may be any type of network configured to provide voice, data, application, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have various Quality of Service (QoS) requirements, such as different throughput, delay, error tolerance, reliability, data throughput, mobility, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in FIG. 1A , it will be understood that the RAN 104 / 113 and / or the CN 106 / 115 may communicate directly or indirectly with other RANs that use the same RAT as the RAN 104 / 113 or a different RAT. In addition to being connected to the RAN 104 / 113, which may utilize, for example, NR radio technology, the CN 106 / 115 may also communicate with another RAN (not shown) that uses GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0018]

[0060] The CNs 106 / 115 may also serve as gateways for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network providing Plain Old Telephone Service (POTS). The Internet 110 may include a worldwide system of interconnected computer networks and devices that use common communication protocols, such as Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and / or Internet Protocol (IP) within the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may use the same RAT as the RANs 104 / 113 or a different RAT.

[0019]

[0061] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a, which may use a cellular-based wireless technology, and with a base station 114b, which may use an IEEE 802 wireless technology.

[0020]

[0062] 1B is a system diagram illustrating an example of a WTRU 102. As shown in FIG. 1B, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be understood that the WTRU 102 may include any subcombination of the above elements while remaining consistent with an embodiment.

[0021]

[0063] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), field programmable gate array (FPGA) circuitry, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, output control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to a transceiver 120, which may be coupled to a transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated within an electronic package or chip.

[0022]

[0064] The transmit / receive element 122 may be configured to transmit or receive signals to or from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0023]

[0065] 1B depicts the transmit / receive element 122 as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may use MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0024]

[0066] The transceiver 120 may be configured to modulate signals transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate over multiple RATs, such as NR and IEEE 802.11.

[0025]

[0067] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. Additionally, the processor 118 may access information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information and store data in memory that is not physically located on the WTRU 102, such as on a server or on a home computer (not shown).

[0026]

[0068] The processor 118 may obtain power from the power source 134 and may be configured to distribute and / or control power to other components within the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0027]

[0069] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or instead of information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / or may determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may obtain location information by any suitable location determination method while remaining consistent with an embodiment.

[0028]

[0070] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television receiver, a hands-free headset, a Bluetooth module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripherals 138 may include one or more sensors, which may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, a direction sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0029]

[0071] The WTRU 102 may include a full-duplex radio where transmission and reception of some or all of the signals associated with a particular subframe (e.g., for both the UL (e.g., for transmission) and downlink (e.g., for reception) may be parallel and / or simultaneous. The full-duplex radio may include an interference management unit 139 to reduce and / or substantially eliminate self-interference by hardware (e.g., chokes) or processor-based signal processing (e.g., by a separate processor (not shown) or processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for transmission and reception of some or all of the signals (e.g., associated with a particular subframe for either the UL (e.g., for transmission) or downlink (e.g., for reception)).

[0030]

[0072] 1C is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As mentioned above, the RAN 104 may use E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also communicate with the CN 106.

[0031]

[0073] The RAN 104 may include eNode-Bs 160a, 160b, and 160c, although it will be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, and 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, and 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit and / or receive wireless signals to and from the WTRU 102a.

[0032]

[0074] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. As shown in Figure 1C, the eNode-Bs 160a, 160b, 160c may communicate with each other over an X2 interface.

[0033]

[0075] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the above elements is shown as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0034]

[0076] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 by an S1 interface and may act as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies such as GSM and / or WCDMA.

[0035]

[0077] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 by an S1 interface. The SGW 164 may generally route and forward user data packets to and from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions such as anchoring the user plane during handovers between eNode Bs, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0036]

[0078] The SGW 164 may be connected to a PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0037]

[0079] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0038]

[0080] Although FIGS. 1A-1D depict the WTRU as a wireless terminal, it is contemplated that in certain representative embodiments such a terminal may use a wired communication interface (eg, temporarily or permanently) with a communication network.

[0039]

[0081] In a representative embodiment, the other network 112 may be a WLAN.

[0040]

[0082] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access to or interface with a distribution system (DS) or another type of wired / wireless network that carries traffic into and out of the BSS. Traffic to a STA originating from outside the BSS may arrive and be delivered to the STA through the AP. Traffic originating from a STA to a destination outside the BSS may be sent to the AP to be delivered to its respective destination. Traffic between STAs within the BSS may be sent through the AP; for example, a source STA may send traffic to the AP, which can deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be sent (e.g., directly) between a source STA and a destination STA using direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs within or using an IBSS (e.g., all of the STAs) can communicate directly with each other. IBSS mode communication may also be referred to herein as an "ad hoc" mode of communication.

[0041]

[0083] When using 802.11ac infrastructure mode of operation or a similar mode of operation, an AP can transmit beacons on a fixed channel, such as a primary channel. The primary channel can be a fixed width (e.g., a 20 MHz wide band) or a dynamically configured width via signaling. The primary channel can be the operating channel of the BSS and can be used by STAs to establish a connection with the AP. In certain representative embodiments, for example, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) can be implemented within an 802.11 system. In CSMA / CA, STAs (e.g., all STAs), including the AP, can sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is in use, the particular STA can back off. Within a given BSS, one STA (e.g., only one station) can transmit at any given time.

[0042]

[0084] For example, by combining a primary 20 MHz channel with adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel, a high throughput (HT) STA can use the 40 MHz wide channel for communication.

[0043]

[0085] A Very High Throughput (VHT) STA may support channels with widths of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz. A 40 MHz and / or 80 MHz channel can be formed by combining contiguous 20 MHz channels. A 160 MHz channel can be formed by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, which may be called an 80+80 configuration. In the 80+80 configuration, the channel-encoded data can be passed through a segment parser, which can split the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time-domain processing can be performed separately for each stream. The streams can be mapped onto two 80 MHz channels, and the data can be transmitted by the transmitting STA. At the receiver of the receiving STA, the above 80+80 configuration operation can be reversed, and the combined data can be sent to the Medium Access Control (MAC).

[0044]

[0086] Sub-1 GHz modes of operation are supported by 802.11af and 802.11ah. Compared to those used in 802.11n and 802.11ac, 802.11af and 802.11ah reduce the channel operating bandwidths and carriers. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to exemplary embodiments, 802.11ah can support meter-type control / machine-type communication, such as MTC devices, within macro coverage areas. MTC devices may have limited functionality, including support for (e.g., only) specific and / or limited bandwidths. MTC devices may include batteries with above-threshold battery life (e.g., to maintain very long battery life).

[0045]

[0087] WLAN systems that can support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, can include a channel that can be designated as a primary channel. The primary channel can have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be configured and / or limited by a STA among all STAs operating in the BSS that can support the minimum bandwidth operating mode. In the 802.11ah example, the primary channel can be 1 MHz wide for a STA (e.g., an MTC-type device) that supports (e.g., only supports) 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) setting can depend on the state of the primary channel. For example, if the primary channel is in use by a STA (that only supports 1 MHz operating mode) transmitting to the AP, the entire available frequency band can be considered in use, even though a large portion of the frequency band may remain unused and available.

[0046]

[0088] In the United States, the available frequency bands that can be used by 802.11ah are 902MHz to 928MHz. In South Korea, the available frequency bands are 917.5MHz to 923.5MHz. In Japan, the available frequency bands are 916.5MHz to 927.5MHz. Depending on the country code, the total available bandwidth for 802.11ah is 6MHz to 26MHz.

[0047]

[0089] 1D is a system diagram illustrating the RAN 113 and the CN 115 according to one embodiment. As mentioned above, the RAN 113 can communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using NR radio technology. The RAN 113 can also communicate with the CN 115.

[0048]

[0090] While the RAN 113 may include gNBs 180a, 180b, and 180c, it will be understood that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, and 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, and 180c may implement MIMO technology. For example, the gNBs 180a and 180b may utilize beamforming to transmit and / or receive signals to and from the gNBs 180a, 180b, and 180c. Thus, for example, the gNB 180a may use multiple antennas to transmit and / or receive wireless signals to and from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, and 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers (not shown) to the WTRU 102a. A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In one embodiment, the gNBs 180a, 180b, and 180c may implement coordinated multipoint (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNBs 180a and 180b (and / or 180c).

[0049]

[0091] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using scalable numerology-related transmissions. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., including different numbers of OFDM symbols and / or lasting for varying absolute times).

[0050]

[0092] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c can communicate with the gNBs 180a, 180b, 180c without accessing any other RANs (e.g., eNode-Bs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c can utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c can communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate with / connect to a gNB 180a, 180b, 180c while also communicating with / connecting to another RAN, such as an eNode-B 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0051]

[0093] Each of the gNBs 180a, 180b, 180c can be associated with a particular cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a, 184b, routing of control plane information to Access and Mobility Management Functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D , the gNBs 180a, 180b, 180c can communicate with each other over the Xn interface.

[0052]

[0094] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the above elements is shown as part of the CN 115, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0053]

[0095] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, supporting network slicing (e.g., handling various PDU sessions with different requirements), selecting a particular SMF 183a, 183b, managing registration areas, terminating NAS signaling, mobility management, etc. Network slicing may be used by the AMF 182a, 182b to customize the CN support of the WTRUs 102a, 102b, 102c based on the type of service being utilized. For example, different network slices may be established for different use cases, such as services relying on Ultra-Reliable Low-Latency (URLLC) access, services relying on enhanced Massive Mobile Broadband (eMBB) access, services for Machine Type Communications (MTC) access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that use other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0054]

[0096] The SMFs 183a and 183b may be connected to the AMFs 182a and 182b in the CN 115 via an N11 interface. The SMFs 183a and 183b may also be connected to the UPFs 184a and 184b in the CN 115 via an N4 interface. The SMFs 183a and 183b may select and control the UPFs 184a and 184b and configure the routing of traffic through the UPFs 184a and 184b. The SMFs 183a and 183b may perform other functions such as managing and assigning IP addresses for UEs, managing PDU sessions, enforcing policy and controlling QoS, providing downlink data notification, etc. The type of PDU session may be IP-based, non-IP-based, Ethernet-based, etc.

[0055]

[0097] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 by an N3 interface, and the gNBs may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks such as the Internet 110 to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 184, 184b may perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, and providing mobility anchoring.

[0056]

[0098] The CN 115 may facilitate communication with other networks. For example, the CN 115 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b via UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0057]

[0099] 1A-1D and the corresponding descriptions thereof, one or more or all of the functions described herein with respect to one or more of the WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-ab, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). An emulation device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation device may be used to test other devices and / or to simulate the functionality of a network and / or a WTRU.

[0058]

[0100] The emulation device may be designed to perform one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more emulation devices may perform one or more or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices in the communication network. One or more emulation devices may perform one or more or all functions while temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for testing and / or may perform testing using wireless communications.

[0059]

[0101] The one or more emulation devices may perform one or more functions, inclusive, without being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in test labs and / or test scenarios within non-deployed (e.g., test) wired and / or wireless communication networks to perform testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may include, for example, one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0060]

[0102] IEEE 802.11ac allows very high-throughput (VHT) STAs to support channels of 20 MHz, 40 MHz, 80 MHz, and 160 MHz width. 40 MHz and 80 MHz channels can be formed by combining contiguous 20 MHz channels, as in IEEE 802.11n. A 160 MHz channel can be formed by combining eight contiguous 20 MHz channels or two non-contiguous 80 MHz channels. The latter can be called an 80+80 configuration. In the 80+80 configuration, the channel-encoded data can be passed through a segment parser that splits the data into two streams. Inverse Fast Fourier Transform (IFFT) and time-domain processing can be performed separately for each stream. The streams can be mapped onto two channels, and the data is transmitted. At the receiver, the above mechanism can be reversed, and the combined data can be sent to the MAC.

[0061]

[0103] IEEE 802.11af and 802.11ah support sub-1 GHz modes of operation. These specifications may reduce channel operating bandwidths and carriers compared to those used in IEEE 802.11n and 802.11ac. IEEE 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths within the TV White Space (TVWS) spectrum, while IEEE 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. IEEE 802.11ah can be used to support meter-type control (MTC) devices within macro coverage areas. MTC devices may have limited functionality, including limited bandwidth support, but may also have very long battery life requirements.

[0062]

[0104] WLAN systems that support multiple channels and channel bandwidths, such as IEEE 802.11n, 802.11ac, 802.11af, and 802.11ah, can include a channel designated as the primary channel. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. Therefore, the bandwidth of the primary channel may be limited by the STA, among all STAs operating in the BSS, that supports the smallest bandwidth operating mode. For example, in IEEE 802.11ah, the primary channel may be 1 MHz wide if there is an STA (e.g., an MTC device) that only supports 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, or other channel bandwidth operating modes. All carrier sensing and NAV configuration may depend on the state of the primary channel. For example, if the primary channel is in use, e.g., by STAs that only support 1 MHz mode of operation transmitting to the AP, the entire available frequency band may be considered in use, even though a large portion of the frequency band remains unused and available.

[0063]

[0105] In the United States, the available frequency band that can be used by IEEE 802.11ah can be 902MHz to 928MHz. In South Korea, the available frequency band can be 917.5MHz to 923.5MHz, and in Japan, the available frequency band can be 916.5MHz to 927.5MHz. Depending on the country code, the total bandwidth available for IEEE 802.11ah can be 6MHz to 26MHz.

[0064]

[0106] IEEE 802.11™ Highly Efficient WLAN (HEW) includes embodiments to improve the quality of service experienced by all users across a wide range of wireless users in many scenarios, including high-density scenarios in the 2.4 GHz, 5 GHz, and 6 GHz bands. New use cases are being considered by 802.11 HEW to support high-density deployment of APs, STAs, and associated Radio Resource Management (RRM) technologies.

[0065]

[0107] Potential applications for HEW include emerging usage scenarios such as data distribution for events in stadiums, high user density scenarios such as train stations or corporate / retail environments, and the increasing reliance on video distribution and wireless services for medical applications.

[0066]

[0108] In 802.11ax or HEW, measurement traffic for various applications has a high probability of being short packets, and there are network applications that can also generate short packets. These applications may include virtual offices, transmit power control (TPC) acknowledgements (ACKs), video streaming ACKs, device / controllers (such as mice, keyboards, and game controllers), access (e.g., probe requests / responses), network selection (e.g., probe requests and Access Network Query Protocol (ANQP)), and network management (e.g., control frames). Furthermore, multi-user (MU) features, including uplink (UL) and downlink (DL) OFDMA and UL and DL MU-MIMO, have been introduced, specifying mechanisms for multiplexing UL random access for various purposes.

[0067]

[0109] IEEE 802.11 Extreme High Throughput (EHT) includes embodiments to further increase peak throughput and improve efficiency of IEEE 802.11 networks. EHT use cases and applications may include high-throughput and low-latency applications such as video-over-WLAN, augmented reality (AR), and virtual reality (VR). The list of features within EHT may include multiple APs, multi-band, 320 MHz bandwidth, 16 spatial streams, HARQ, full duplex (in time and frequency domain), AP cooperation, semi-orthogonal multiple access (SOMA), and new designs for 6 GHz channel access.

[0068]

[0110] In a typical IEEE 802.11 network, a STA may be associated with a single AP and transmit to and from that AP with little or no coordination with transmissions in neighboring BSSs. STAs may follow overlapping basic service set (OBSS) transmissions based on a CSMA protocol that is completely independent between BSSs. In IEEE 802.11ax, a degree of coordination between OBSSs is introduced through the spatial reuse (SR) procedure, which may enable OBSS transmissions based on adjusted energy detection thresholds (e.g., using the OBSS PD procedure) or knowledge of the amount of interference that can be tolerated by the receiving OBSS STA (e.g., using the SRP procedure).

[0069]

[0111] The embodiments described herein may provide procedures that enable further coordination between OBSSs by allowing transmissions to or from multiple APs to one or more STAs. Multi-AP coordination between OBSSs may be performed in unlicensed bands and / or inherent in the IEEE 802.11 protocol.

[0070]

[0112] To improve the overall throughput of the considered STAs / WTRUs, multiple APs / eNBs can transmit to the same or multiple STAs / WTRUs within the same or different time and frequency resources using joint processing / transmission. Dynamic cell selection can be treated as a special case of joint processing, in which only one of a set of APs / eNBs actively transmits data at any given time. On the other hand, to reduce the interference experienced by each STA / WTRU, multiple APs / eNBs can transmit to different STAs / WTRUs within the same or different time and frequency resources using coordinated beamforming / scheduling (e.g., each AP / eNB serving its own STA / WTRU). Multi-AP / eNB cooperation can achieve significant improvements in cell-average and / or cell-edge throughput. Multiple transmit antennas can be considered available for each STA / WTRU / AP / base station. Spatial domain signal processing at each base station can handle simultaneous interference suppression for other STAs / WTRUs and optimization of signal quality for the desired STA / WTRU.

[0071]

[0113] In general, it can be assumed that some channel state information is available at the AP or base station, e.g., by explicit feedback. Furthermore, some timing / frequency synchronization can be assumed so that more complex signal processing to deal with inter-carrier or inter-symbol interference can be avoided.

[0072]

[0114] Multi-AP transmission schemes in a WLAN can be classified based on cooperative OFDMA, cooperative nulling / beamforming, and cooperative SU / MU transmission. In cooperative SU transmission, multiple APs can transmit to a STA within one resource unit (RU). Cooperative SU transmission can be one of (in order of complexity): dynamic selection, cooperative SU beamforming, and cooperative MU beamforming. In cooperative point selection, transmission can be dynamically selected from one of a set of APs and may include HARQ. In cooperative SU beamforming, transmissions can occur simultaneously from multiple APs, and the transmissions may be beamformed. In cooperative MU beamforming, multiple APs can transmit or receive data to or from multiple STAs within one RU.

[0073]

[0115] FIG. 2 illustrates an example 200 of cooperative orthogonal frequency division multiple access (OFDMA), which may be used in any combination with other embodiments described herein. In cooperative OFDMA, each group of RUs may be used by one AP (e.g., 214a, 214b, 214c, or 214d) to transmit or receive data. For example, as shown in FIG. 2, the STAs 202a-202l may be divided into two groups: cell-center STAs 202a, 202d, 202g, and 202j, and cell-edge STAs 202b, 202c, 202e, 202f, 202h, 202i, 202k, and 202j. The APs 214a, 214b, 214c, and 214d may allow their uninterfered STAs 202a, 202d, 202g, and 202j (i.e., cell-center STAs) to use the full bandwidth. However, the APs 214a, 214b, 214c, and 214d may restrict their own STAs 202b, 202c, 202e, 202f, 202h, 202i, 202k, and 202l (i.e., cell-edge STAs) that may be affected by interference to use only a portion of the frequency bandwidth. For example, the STA 202a may be permitted to use the entire bandwidth (e.g., full spectrum / channel), while the STAs 202b and 202c may be limited to using only a certain portion of the bandwidth. Data or information communicated between the APs 214a, 214b, 214c, and 214d and the STAs 202a through 202l may be beamformed or may have MU-MIMO on each RU 205, 210, 220, 225, 230, 235, 240, and 245. Complexity may be relatively low to moderate. In one embodiment, APs can divide OFDMA resource units (RUs) among APs in a cooperative manner, with each AP restricted to a specific RU. In another embodiment, an AP can allow STAs that are not affected by interference or that do not impact others to use the full bandwidth while limiting access for STAs that may be affected. This is called fractional frequency reuse (FFR).

[0074]

[0116] 3 illustrates an example of a resource allocation 300 for cooperative OFDMA, which may be used in any combination with the other embodiments described herein. As shown in FIG. 3, STAs (e.g., cell-center STAs) associated with Group 1 resources 305, 315 (e.g., center group RUs) may be allowed to use the entire band (e.g., subband 1 and subband 2), while STAs (e.g., cell-edge STAs) associated with Group 2 resources 310 or Group 3 resources 320 may be restricted to using only their assigned resources (e.g., subband 1 or subband 2).

[0075]

[0117] 4 illustrates an example 400 of cooperative beamforming / cooperative nulling (CB / CN), which may be used in any combination of other embodiments described herein. In cooperative beamforming / cooperative nulling, each AP (e.g., AP1 414a and AP2 414b) applies precoding to transmit information between itself and its desired STA (e.g., STA1 402a and STA2 402b), thereby suppressing interference between the desired STAs. In the example illustrated in FIG. 4, data regarding each STA (e.g., STA1 402a or STA2 402b) may only be needed at its associated AP (e.g., AP1 414a or AP2 414b), while channel information from the other STA (e.g., STA2 402b or STA1 402a) may be needed at both APs (e.g., AP1 414a and AP2 414b).

[0076]

[0118] 5 illustrates an example 500 of cooperative nulling / cooperative beamforming (CB / CN) using interference alignment (IA), which may be used in any combination with other embodiments described herein. Interference alignment allows an AP to precode information for a STA so that after the AP's signal passes through the channel, unwanted information (e.g., STA1's information is unwanted for STA2) falls into the interference subspace at the STA. In the example shown in FIG. 5, where two APs, AP1 514a and AP2 514b, and two STAs, STA A 502a and STA B 502b, are in the wireless medium, AP1 514a and AP2 514b may be in the same BSS, and information for STA A 502a, e.g.,

number

number

number

number

[0077]

[0119] The operations at AP1 514a and AP2 514b for a group of subcarriers or a single subcarrier are

number

number

number

[0078]

[0120] Due to precoding at AP1 514a and AP2 514b, cross-channel interference components may fall into the same subspace, e.g., V1 of STA A 502a and V2 of STA B 502b. This scheme may correspond to a specific case of an interference alignment (IA) scheme. A key advantage of this particular scheme may be that AP1 514a or AP2 514b may not need to use channel state information related to AP2 514b or AP1 514a. This scheme may therefore reduce traffic by eliminating the need to exchange information between APs 514a and 514b. Additionally, this scheme can be implemented by using APs 514a, 514b and STAs 502a, 502b equipped with M antennas.

number

[0079]

[0121] In cooperative single-user (SU) or multi-user (MU) transmission, multiple APs can cooperate to simultaneously transmit information to or from a single STA or multiple STAs. In this case, both channel information and data for the STAs may be required at both APs. Cooperative SU or MU transmission can be, for example, one of cooperative SU transmission or cooperative MU beamforming.

[0080]

[0122] In cooperative SU transmission, multiple APs can transmit to a STA within one RU and can be one of (in order of complexity) dynamic point selection, cooperative SU beamforming, or joint precoding. In dynamic point selection, transmission can be dynamically selected from one of a set of APs and can incorporate HARQ.

[0081]

[0123] 6 shows an example 600 of single-user (SU) joint precoded multi-AP transmission, or cooperative SU beamforming, which can be used in any combination with other embodiments described herein. In cooperative joint precoding, transmissions can be simultaneous from multiple APs (e.g., AP1 614a and AP2 614b) and can be beamformed or precoded to a desired STA (e.g., STA1 602a) on one or more RUs. For example, as shown in FIG. 6, in cooperative SU transmission, AP1 614a and AP2 614b can transmit signals within one UR to STA1 602a.

[0082]

[0124] 7 illustrates an example 700 of multi-user (MU) pre-coded multiple AP transmission, or cooperative MU beamforming, which may be used in any combination with other embodiments described herein. In cooperative MU beamforming, multiple APs (e.g., AP1 714a and AP2 714b) can transmit or receive data to or from multiple STAs (e.g., STA1 702a and STA2 702b) on one or more RUs. For example, as shown in FIG. 7, AP1 714a and AP2 714b cooperate (e.g., via backhaul) to simultaneously transmit / receive data to and from STA1 702a and STA2 702b in one or more RUs. The multi-AP schemes described herein may include scenarios related to cooperative beamforming and joint processing.

[0083]

[0125] In an IEEE 802.11 system, a STA may send an association request to an AP and, if successful, may receive an association response from the AP indicating that the STA is a member of the BSS. In a multi-AP system, an AP may be affected by multiple APs and may require some degree of association with each AP. The multi-AP association described herein may allow a single STA to discover and associate with multiple APs.

[0084]

[0126] Furthermore, to enable cooperative OFDMA in trigger-based IEEE 802.11 systems, such as IEEE 802.11ax and later, the embodiments described herein may enable a STA to identify whether it is a cell-center or cell-edge STA in a trigger-based OFDMA system and feed that information back to the AP. The embodiments described herein may also enable a STA and / or an AP to perform trigger-based scheduled cooperative OFDMA schemes and / or trigger-based random access cooperative OFDMA schemes. OFDMA transmissions from different BSSs may be synchronized to ensure orthogonality in the presence of various timing offsets.

[0085]

[0127] Furthermore, cooperative beamforming and cooperative nulling allow a transmitter (or transmitting STA) to estimate the effective channel to both a desired receiver (or desired receiving STA) and an interfered receiver (e.g., a receiver or STA experiencing interference from the transmitter). Channel feedback can be used to provide feedback from a desired receiver in a BSS. Feedback can also be requested from a receiver in another BSS or a BSS associated with the current BSS using multi-AP association. Furthermore, embodiments described herein may enable feedback to be requested in a manner that is efficient for both the desired receiver and the interfered receiver. The direction of the desired transmission (e.g., uplink or downlink) and the direction of the interfered receiver (e.g., uplink or downlink) can be considered. Both triggered and non-triggered based procedures can be provided.

[0086]

[0128] Furthermore, the embodiments described herein can provide design-specific transmission procedures for various system architectures with respect to obtaining effective channels and designing effective precoders. The architectures can be based on whether (1) both transmitters are in the DL (DL-DL) from the AP, (2) both transmitters are in the uplink (UL-UL) from the STA, or (3) whether one transmitter is the AP and the other is the STA or vice versa (DL-U or UL-DL). In one example, a UL-UL architecture can use or modify the spatial reuse parameter (SRP)-based spatial reuse (SR) in IEEE 802.11ax. With SRP-based spatial reuse (SR), a STA can receive an SRP PPDU with an indication of the maximum amount of interference the AP can tolerate from another STA in a neighboring BSS that wants to transmit simultaneously (e.g., in an SR manner) while the AP is receiving a frame from a particular STA.

[0087]

[0129] Furthermore, to enable multi-AP transmission in DL with beamforming or beam-nulling techniques, the AP may need to know DL channel state information (CSI) for all STAs. Assuming that the DL and UL channels are reciprocal, the AP can obtain DL CSI by receiving UL reference signals, pilot signals, or training signals transmitted from the STAs. From this, the AP can obtain information such as path loss from various STAs to various APs, which may assist the AP in achieving multi-AP DL beamforming or nulling. However, if the UL transmissions from the STAs are power-controlled, the signals received from all STAs may have the same or similar power levels. Therefore, in such a scenario, the AP may not be able to determine the path loss, and thus obtain path loss information between the AP and the STAs. If the STAs are power-limited, the AP's estimation of the reciprocal channel derived from the STAs transmitting the NDP may be inadequate because it may potentially be noise-limited. In such a scenario, channel estimation may be performed and improved to enable DL SU-MIMO or MU-MIMO.

[0088]

[0130] The AP association procedure may occur as part of a typical STA association procedure. Figure 8A illustrates an example of multiple AP association during STA association 800, which may be used in combination with any of the other embodiments described herein.

[0089]

[0131] In the example shown in FIG. 8A , the STA 802 may transmit probe request frames 805a, 805b (and / or authentication request frames 815a, 815b) to identify candidate APs, such as AP1 814a and AP2 814b. In an embodiment, each of the probe request frames 805a, 805b may include, but is not limited to, a request for multiple AP association, transmission, and / or reception capabilities. APs (e.g., AP1 814a and AP2 814b) that receive the probe request frames 805a, 805b (and / or authentication request frames 815a, 815b) transmit probe response frames 810a, 810b (and / or authentication response frames 820a, 820b) to the STA 802. Each of the probe response frames 810a, 810b may include, but is not limited to, multiple AP association, transmission, and / or reception capabilities. The probe response frames 810a, 810b may also include candidate cooperating APs (eg, AP1 814a and AP2 814b) and their multiple AP capabilities (eg, fractional frequency reuse (FFR), cooperative, or joint transmission).

[0090]

[0132] The STA 802 may connect to a primary AP (e.g., AP1 814a). In an embodiment, the primary AP may be defined as the AP to which the STA connects in a single-AP scenario. The primary AP may be the AP to which the STA connects, for example, for IEEE 802.11 transmissions (e.g., pre-IEEE 802.11ax). The secondary AP (e.g., AP2 814b) may be an additional AP used for multi-AP transmissions. In an embodiment, the primary AP must be part of the transmission. In other embodiments, the best AP in the multi-AP service set may be used for the transmission. There may be multiple secondary APs in a multi-AP service set, and the APs may be ordered, for example, as primary AP, secondary 1 AP, secondary 2 AP, tertiary AP, etc. A multi-AP service set or multi-AP service set may include multiple APs that can support multiple-AP associations, transmissions, and / or reception between the STA and multiple APs.

[0091]

[0133] 8A, the STA 802 may transmit one or more multiple AP association request frames 825 to the APs 814a, 814b along with an indication of the preference for associating with the APs 814a, 814b (e.g., primary AP, secondary AP, tertiary AP, or AP1, AP2). The AP preference may be explicitly signaled in the multiple AP association request frame 825 or may be implicitly signaled by the order in which the AP identifiers appear in the multiple AP association request frame 825.

[0092]

[0134] The STA can identify the priority from the strength with which the beacon or probe response frames 810a, 810b are received from each of the APs. The beacon or probe response frames 810a, 810b can include AP capability information for multi-AP transmission / reception, such as the multi-AP service set element shown in FIG. 10 as an example. The APs 814a, 814b can inform the STA 802 of possible multi-AP combinations (e.g., multi-AP service sets) and associated multi-AP capabilities, and the STA can select a subset to use for the multi-AP association request frame 825.

[0093]

[0135] The multi-AP association request frame 825 may indicate the type of cooperation requested. In one example, the STA 802 may request a specific type of cooperation. In some embodiments, the STA 802 may request all types of cooperation it can support. Examples of types of cooperation may include, but are not limited to, coordinated beamforming, coordinated OFDMA, joint transmission, and multi-AP HARQ. Upon receiving the multi-AP association request frame 825, the APs 814a, 814b may perform some AP cooperation procedure 830 to ensure that they can cooperate in the requested manner. This may involve backhaul or higher layer signaling by the AP coordinator. Alternatively or additionally, the primary AP (e.g., AP1 814a) may send an over-the-air (OTA) signal to the secondary AP (e.g., AP2 814b) with details of the cooperation request and the type of data required. A multi-AP association request 825 may be sent by the STA 802 to add, remove, or change the APs 814a, 814b with which the STA 802 associates, such as to block an AP in a previously requested multi-AP service set. As an example, the multi-AP association request frame 825 may include a multi-AP selection element, as shown in Figure 11. The multi-AP association request frame 825 may be broadcast to all APs 814a, 814b in the multi-AP service set, or may be transmitted separately to each individual AP 814a, 814b.

[0094]

[0136] The APs 814a, 814b may then transmit multi-AP association response frames 835a, 835b to the STA 802. In an embodiment, each AP 814a, 814b may transmit an independent multi-AP association response frame 835a, 835b to the STA 802. The multi-AP association response frames 835a, 835b may be transmitted in a manner that ensures divisibility in the code, time, frequency, and / or spatial domains. Alternatively or additionally, the multi-AP association response frames 835a, 835b may be transmitted as a test of the system using a requested DL multi-AP scheme, such as joint transmission. The multi-AP association response frames 835a, 835b may permit the multi-AP scheme requested by the STA 802 (e.g., by the multi-AP association request frame 825). The multi-AP response frames 835a, 835b may reject a multi-AP scheme requested by the STA 802 (e.g., by the multi-AP association request frame 825). The multi-AP association response frames 835a, 835b may propose an alternative or additional scheme to the scheme requested by the STA.

[0095]

[0137] The STA 802 can then respond to both APs 814a, 814b with multi-AP association acknowledgement (ACK) frames 840a, 840b to ensure that both APs 814a, 814b know that the STA 802 is now ready for multi-AP transmit / receive setup. Provided that one of the APs 814a, 814b cannot grant the multi-AP association requested by the STA 802 and does not send a multi-AP association response frame 835a, 835b, the multi-AP ACK frames 840a, 840b can ensure that the other AP (e.g., AP1 814a or AP2 814b) knows that it is the primary AP and should not set up a multi-AP transmit / receive procedure. For example, if AP2 814b does not grant the multi-AP association request frame 825 requested by STA 802 and does not send a multi-AP association response frame 835b, STA 802 can transmit a multi-AP association ACK frame 840a to AP1 814a to ensure that AP1 814a is the primary AP that does not set up the multi-AP transmission / reception procedure. Once STA 802 receives the multi-AP association ACK frames 840a, 840b from APs 814a, 814b, STA 802 can initiate a multi-AP transmission / reception scheme with APs 814a, 814b and perform data transmission 845 with APs 814a, 814b.

[0096]

[0138] Assuming AP1 814a and AP2 814b are in the same multi-AP service set, packets may be transmitted from APs 814a and 814b in the multi-AP service set without overlapping at the STA 802. For example, AP1 814a and AP2 814b may transmit probe response frames 810a and 810b without overlapping and such that AP1's probe response frame 810a has time to be decoded before AP2's probe response frame 810b arrives. This may also be applicable to multi-AP association responses. For example, AP1 814a and AP2 814b may transmit multi-AP association response frames 835a and 835b without overlapping and such that AP1's multi-AP association response frame 835a has time to be decoded before AP2's multi-AP association response frame 835b arrives. In other words, the APs 814a, 814b can transmit packets (e.g., probe response frames 810a, 810b or multi-AP association response frames 835a, 835b) to the STA 802 based on a predetermined order or a random order so that the packets do not overlap with each other at the STA 802. The order can be determined by the APs 814a, 814b, the STA 802, the network operator, or a network controller.

[0097]

[0139] FIG. 8B shows an example of a multiple-AP association procedure 850 that can be used in any combination with other embodiments described herein. In step 855, a STA may transmit one or more probe request frames to multiple APs in its vicinity to indicate that the STA can support multiple-AP operation, such as transmitting and / or receiving with multiple APs. Before transmitting the probe request frame, the STA may select multiple APs based on active scanning. For example, if the STA does not have information about APs around it, the STA may broadcast a probe request frame to all nearby APs. If the STA has information about the network operators or carriers supported by the APs, the STA may select a specific AP having a service set identifier (SSID) corresponding to the network operator or carrier. The STA may then transmit a probe request frame to the specific AP to elicit a probe response frame from the selected AP. If the STA has information about the addresses (e.g., BSSIDs) of specific APs, the STA may select those APs to send probe request frames to and receive probe response frames from. The probe request frame may include one or more indicators indicating that the STA can support multiple-AP operation with multiple APs. The probe request frame may also include one or more indicators requesting the APs that are part of a multi-AP service set that provides multi-AP operation to the STA if the AP received the probe request frame.

[0098]

[0140] In step 860, the STA may receive probe response frames from multiple APs in response to the probe request frame. Each probe response frame may include one or more indicators indicating the multi-AP operation capabilities of the AP that transmitted the probe response frame to the STA. For example, each probe response frame may include a multi-AP service set element as shown in FIG. 10 for each AP that transmitted the probe response frame. Based on the multi-AP service set element, the STA can identify multi-AP parameters (e.g., group and multi-AP service set) for multi-AP operation with multiple APs. The multi-AP service set element may include, but is not limited to, a multi-AP joint transmission capability, a multi-AP hybrid automatic repeat request (HARQ) capability, a multi-AP multiple-input multiple-output (MIMO) capability, a dynamic AP selection capability, a multi-AP roaming capability, and a multi-AP cooperative beamforming capability.

[0099]

[0141] In one embodiment, when AP1, AP2, and AP3 belong to the same multi-AP service set that provides multi-AP operation to a STA, each probe response frame provides capability information for each of AP1, AP2, and AP3. For example, a probe response frame transmitted by AP1 includes the capability information of AP2 and AP3 in addition to the capability information of the transmitting AP1. Similarly, a probe response frame transmitted by AP2 includes the capability information of AP1 and AP3 in addition to the capability information of the transmitting AP2.

[0100]

[0142] In another embodiment, if AP1 and AP2 belong to the same multi-AP service set but AP3 does not belong to the multi-AP service set to which AP1 and AP2 belong, each of the probe response frames transmitted from AP1 and AP2 includes the capability information of AP1 and AP2, respectively. However, the probe response frame transmitted from AP3 may not include the capability information of AP1 and AP2, but may include the capability information of other APs in a different multi-AP service set to which AP3 belongs. For example, the probe response frame transmitted by AP1 includes the capability information of AP2 in addition to the capability information of AP1. However, the probe response frame transmitted by AP3 may include the capability information of AP3, AP4, and AP5, such that AP3, AP4, and AP5 form a multi-AP service set different from the multi-AP service set to which AP1 and AP2 belong.

[0101]

[0143] In step 865, the STA may transmit an authentication request frame to multiple APs and receive authentication response frames from multiple APs in step 870. In one example, the STA may transmit an authentication request frame 815a to AP1 814a and receive an authentication response frame 820a from AP1 814a, as shown in FIG. 8A. The STA may then transmit another authentication request frame 815b to AP2 814b and receive another authentication response frame 820b from AP2 814b. In another example, if the STA associates with AP1 914a before initiating a multi-AP association procedure with AP2 914b, the STA may transmit an authentication request frame 915 only to AP1 914a and receive an authentication response frame 920 from AP1 914a, as shown in FIG.

[0102]

[0144] In step 875, the STA may transmit one or more multi-AP association request frames to multiple APs for multi-AP association. Among other things, the multi-AP association request frame may enable multiple APs to cooperate with one another to form a multi-AP association that provides the STA with multi-AP operation. For example, when an AP receives the multi-AP association request frame, the AP may communicate with each of the other APs via backhaul links between the APs until all APs in the multi-AP service set recognize the STA's association with the APs in the multi-AP service set. In one example, for multi-AP operation, the primary AP may send an OTA signal to the secondary APs (and tertiary APs) to inform them that the STA will associate with the multi-AP service set that includes the APs (e.g., the primary AP, secondary AP, and tertiary AP). The multi-AP association request frame may be broadcast to all APs in the multi-AP service set or may be transmitted individually to each of the multiple APs in the multi-AP service set.

[0103]

[0145] In step 880, the STA may receive multiple AP association response frames from multiple APs, each including one or more indicators indicating permission or denial of multi-AP operation with the multiple APs. For example, the STA may receive a first multiple AP association response frame from AP1, including an indicator indicating permission or denial of multi-AP operation with AP1. The STA may then receive a second multiple AP association response frame from AP2, including an indicator indicating permission or denial of multi-AP operation with AP2. The multiple AP association response frames may be received at the STA in a predetermined order or in a random order until all multiple AP association response frames are correctly received. For example, the multiple AP association response frames may be received in the order of the APs listed in the multi-AP service set. The multiple AP association response frames received at the STA may not overlap with each other so that the STA has time to decode the multiple AP association response frame from AP1 before receiving the next multiple AP association response frame from AP2.

[0104]

[0146] In step 885, if the multiple AP association response frame is received correctly (regardless of whether the multiple AP association response frame includes a grant or a denial for multiple AP operation), the STA may transmit multiple AP association acknowledgement (ACK) frames to the APs that transmitted the multiple AP association response frame. If the multiple AP association frame is not received correctly (regardless of whether the multiple AP association response frame includes a grant or a denial for multiple AP operation), the STA may also transmit multiple AP association negative acknowledgement (NACK) frames to the APs that transmitted the multiple AP association response frame. For example, if a first multiple AP association response frame from AP1 is decoded correctly at the STA, the STA may transmit a first multiple AP association ACK frame to AP1. If the first multiple AP association response frame from AP1 is not decoded correctly at the STA, the STA may transmit a first multiple AP association NACK frame to AP1. Similarly, if the second multi-AP association response frame from AP2 is decoded correctly at the STA, the STA may transmit a second multi-AP association ACK frame to AP2. If the second multi-AP association response frame from AP2 is not decoded correctly at the STA, the STA may transmit a second multi-AP association NACK frame to AP2.

[0105]

[0147] In step 890, if the STA receives a multiple-AP association response frame from an AP in the multiple-AP service set, and the multiple-AP association response frame indicates that multiple-AP operation with the AP is permitted, the STA can initiate multiple-AP operation with the AP by transmitting and / or receiving data to and from the AP. In particular, if a first multiple-AP association response frame received from AP1 indicates that multiple-AP operation with AP1 is permitted and a second multiple-AP association response frame received from AP2 indicates that multiple-AP operation with AP2 is permitted, the STA can transmit and / or receive data to and from AP1 and AP2 using, for example, cooperative orthogonal frequency division multiple access (OFDMA) or cooperative nulling. The STA can also perform joint transmission / reception, HARQ feedback, MIMO, dynamic AP selection, and multiple-AP roaming to multiple APs (e.g., AP1 and AP2).

[0106]

[0148] FIG. 9 illustrates an example of a STA-initiated multi-AP association 900, which may be used in any combination with other embodiments described herein. As shown in FIG. 9, a STA 902 may use an existing IEEE 802.11 probe request / probe response mechanism to identify candidate APs (e.g., AP1 914a and AP2 914b) and associate with a single AP (e.g., AP1 914a). For example, the STA 902 may identify candidate APs (e.g., AP1 914a, AP2 914b) near itself based on active scanning, as described above. The candidate APs (e.g., AP1 914a and AP2 914b) may be included in a multi-AP service set, or a multi-AP service set that provides support for multi-AP association, transmission, and / or reception between the STA and the candidate APs. In one example, AP1 914a may be identified as a primary AP, and AP2 914b may be identified as a secondary AP within the same multi-AP service set. Once candidate APs 914a, 914b are identified, the STA 902 may transmit probe request frames 905a, 905b to the APs 914a, 914b and receive probe response frames 910a, 910b from the APs 914a, 914b. The STA 902 may then perform authentication and association procedures with the AP (e.g., AP1 914a). For example, the STA may transmit an authentication request frame 915 to AP1 914a and receive an authentication response frame 920 from AP1 914a. Once the STA 902 is authenticated by AP1 914a, the STA 902 may send an association request frame 925 to AP1 914a and receive an authentication response frame 930 from AP1 914a. The STA 902 may then initiate a multi-AP association using information about one or more suitable candidate APs in the multi-AP service set, for example. During the probe request / probe response phase, candidate APs (eg, AP1 914a and AP2 914b) can be identified from probe response frames 910a, 910b from other APs.

[0107]

[0149] 9, when the STA 902 initially associates with a primary AP (e.g., AP1 914a), the STA 902 may send a multi-AP association request frame 935a (or an announcement frame) to its primary AP (e.g., AP1 914a) with information about candidate APs (e.g., AP1 914a and AP2 914b) or multiple APs in the multi-AP service set. Alternatively or additionally, the STA 902 may send a multi-AP association request frame 935b (or an announcement frame) to the candidate AP (e.g., AP2 914b) with information about the other AP (e.g., AP1 914a) or multiple APs in the multi-AP service set. The STA 902 may sequentially add one new AP to its own multi-AP service set. APs 914a, 914b can track one or more STAs (e.g., STA 902) that are connected or associated with each of the multi-AP service sets and use that information to schedule a multi-AP scheme or multi-AP operation with the STAs.

[0108]

[0150] In one embodiment, the STA 902 can transmit an indication of the preference for associating multiple APs (e.g., AP1 914a and AP2 914b) in a multi-AP service set, including the ability to change a primary AP (e.g., AP1 914a) to a secondary AP (e.g., AP2 914b), a tertiary AP, etc., as well as the ability to indicate a new primary AP. The preference may be explicitly signaled in the multi-AP association request frame 935a, 935b, or the preference of the APs may be implicitly signaled by the order in which the AP identifiers appear in the multi-AP association request frame 935a, 935b. Upon receiving the multi-AP association request frame 935a, 935b, the APs 914a, 914b may perform some AP coordination procedures 940, such as forwarding security information from the primary AP (e.g., AP1 914a) to the secondary AP (e.g., AP2 914b) and / or ensuring that the AP (e.g., AP1 914a) can only connect to the secondary AP (e.g., AP2 914b) to ensure that the AP (e.g., AP1 914a) can coordinate in the required manner. This may involve backhaul or higher layer signaling by an AP coordinator. Alternatively or additionally, the primary AP (e.g., AP1 914a) may send an OTA signal to the secondary AP (e.g., AP2 914b) with details of the coordination request and the type of data required.

[0109]

[0151] The APs 914a, 914b may then transmit multi-AP association response frames 945a, 945b to the STA 902, as shown in FIG. 9. In one embodiment, each AP 914a, 914b may transmit an independent multi-AP association response frame 945a, 945b to the STA 902. The multi-AP association response frames 945a, 945b may be transmitted in a manner that ensures divisibility in code, time, frequency, and / or space. Alternatively or additionally, the multi-AP association response frames 945a, 945b may be transmitted using a downlink multi-AP scheme as requested (e.g., as a joint transmission or system test). The multiple AP association response frames 945a, 945b can allow the multiple AP scheme requested by the STA 902 in the multiple AP association request frames 935a, 935b, or can deny the multiple AP scheme requested by the STA 902 in the multiple AP association request frames 935a, 935b. Alternatively, or in addition, the multiple AP association response frames 945a, 945b can suggest an alternative scheme to the scheme requested by the STA 902.

[0110]

[0152] The STA 902 can then respond to both APs 914a, 914b with multiple AP association ACK frames 950a, 950b to ensure that both APs 914a, 914b know that the multiple AP transmit / receive setup is now ready at the STA 902. Although not shown in FIG. 9 , provided that one of the APs 914a, 914b cannot grant the multiple AP association request (e.g., 935a or 935b) and does not send a multiple AP association response (e.g., 945a or 945b), the multiple AP association ACK frame (e.g., 950a or 950b) can ensure that the other AP (e.g., 914a or 914b) knows that it is the primary AP and should not set up the multiple AP transmit / receive procedure 955. For example, assuming AP2 914b cannot grant the multi-AP association request 935b and does not send a multi-AP association response 945b (not shown in FIG. 9), the multi-AP association ACK frame 950a may ensure that AP2 914b knows that AP1 914a is the primary AP and that AP2 914b should not set up a multi-AP transmit / receive procedure 955. This may allow for fallback to a single-AP association if the multi-AP association procedure fails.

[0111]

[0153] In one embodiment, an AP can transmit a multi-AP service set element to indicate that it is part of a multi-AP service set (SS). Being part of a multi-AP SS may mean that the AP is capable of multi-AP transmission / reception. Such capability may be indicated explicitly.

[0112]

[0154] FIG. 10 illustrates an example of a multi-AP service set (SS) element 1000 that can be used in combination with any of the other embodiments described herein. As shown in FIG. 10 , the multi-AP SS element 1000 may include an element ID 1005 and element ID extension field 1015, a length field 1010, a multi-AP SS AP count field 1020, and multi-AP SS AP1-N fields 1025 and 1030. The combination of the element ID 1005 and element ID extension field 1015 may indicate that the current element is a multi-AP SS element 1000. The length field 1010 may be used to indicate the length of the multi-AP SS element 1000. The multi-AP SS AP count field 1020 may indicate how many information fields are included in the multi-AP SS element 1000. In one embodiment, if only one field, such as an information field about the transmitting STA, is included, the multi-AP SS AP count field 1020 may be omitted. In other embodiments, this multi-AP SS AP count field 120 can be used to indicate the size of the multi-AP service set, such as by indicating how many APs are included in the multi-STA service set.

[0113]

[0155] The N Multi-AP SS AP fields 1020, 1030 may contain information about each of the APs that are part of the multi-AP service set. In one embodiment, the number of fields may be indicated in the Multi-AP SS AP Count field 1020. In other embodiments, only one AP may be included in the information. The information included in one or more subfields of the N Multi-AP SS AP fields 1020, 1030 may include, for each of the APs, an AP ID 1050 (such as a MAC address or other identifier of the AP), a Master AP Indicator 1055 (e.g., an indication of whether the AP included in this field is a Master or Primary AP or a Slave AP), an indication of various multi-AP capabilities. Examples of various multi-AP capabilities may include, but are not limited to, the ability to support multiple AP joint transmission 1060, multiple AP HARQ 1065, multiple AP MIMO 1070, multiple AP MU-MIMO 1075, dynamic AP selection 1080, multiple AP roaming 1085, and multiple AP cooperative beamforming 1090, as well as an order (e.g., a subfield that may indicate the order of each member AP identified in a multi-AP service set). In an embodiment, the order subfield associated with a member AP may indicate the order of the AP in the multi-AP service set.

[0114]

[0156] The above designs, fields, and subfields are examples and may be implemented using existing or new fields, subfields, elements, MAC / PLCP headers, or any part of the transmission frame.

[0115]

[0157] An AP can include a multi-AP SS element, for example, in its beacon, short beacon, probe response, association response, or fast initial link setup (FILS) discovery frame to indicate that it is part of a multi-AP service set. An AP can also indicate its multi-AP capabilities, including support for multi-AP joint transmission, multi-AP HARQ, multi-AP MIMO, multi-AP MU-MIMO, dynamic AP selection, multi-AP roaming, and multi-AP cooperative beamforming. An AP can also indicate whether it is the master (coordinator) AP or the slave AP in a multi-AP service set. An AP can also indicate whether the field pertains to the transmitting AP or the receiving AP. Additionally, the multi-AP SS element can contain information about one or more member APs in the same multi-AP service set. The multi-AP SS element can provide information about the multi-AP capabilities of other member APs, such as whether they support multi-AP joint transmission, multi-AP HARQ, multi-AP MIMO, multi-AP MU-MIMO, dynamic AP selection, multi-AP roaming, and multi-AP cooperative beamforming. The multi-AP SS element may also indicate whether the other member APs are master or slave APs. In some embodiments, an AP may provide information about one or more or all other member APs in the same multi-AP SS in another element, such as an indication using one of the reserved bits in a reduced neighbor report element or neighbor report element that includes an ID (BSSID, SSID), capability, or indication of whether they are a master or slave AP. Additionally, member APs in a multi-AP service set may be ordered such that the order of member APs included in the multi-AP SS element is a multi-AP SS (MASS) that may be identified by SSID or MASSID and / or provided in the multi-AP SS element.

[0116]

[0158] A non-AP STA can monitor the medium for, for example, beacons, short beacons, or FILS discovery frames to discover a suitable AP or MASS. A non-AP STA can transmit a probe request targeted at an AP and / or MASS to discover one or more APs within its range that are members of a particular MASS. A non-AP STA can include a multiple AP capability element in a probe request frame, which may mean that it can support multiple AP transmission and / or reception. A non-AP STA may include STA capabilities that support multiple AP transmission, such as supporting multiple AP joint transmission, multiple AP HARQ, multiple AP MIMO, multiple AP MU-MIMO, dynamic AP selection, multiple AP roaming, and multiple AP cooperative beamforming. Such capabilities may also be included in a capability element, such as an Extremely High Throughput (EHT) capability element.

[0117]

[0159] A non-AP STA receiving a multi-AP SS element from an AP, which may be included in a beacon, short beacon, probe response, association response frame, FILS discovery frame, or any other type of frame, can understand that the AP is part of a multi-AP service set and that certain multi-AP transmission capabilities may be supported by APs in the multi-AP service set. Additionally, a non-AP STA can discover the identity and / or capabilities of one or more member APs in the same multi-AP SS (MASS).

[0118]

[0160] After discovering information about one or more member APs of the same MASS, the STA can transmit another frame, such as a probe request frame, a multi-AP probe request, or a MASS probe request, which may include one or more IDs, such as the SSID, MASS ID, and / or MAC address, of the member APs targeted by the STA. In other embodiments, the STA can transmit a probe request frame targeted to a MASS ID, and the probe request frame can include a bitmap with one or more bits set to 1, which can indicate the member APs, which can be associated with the order of the member APs in the MASS for which a probe response is requested. The probe request frame can also include an indication that it is a probe request for the MASS. A member AP of the MASS can respond with a probe response after receiving a probe request targeted to a MASS ID that includes its own MAC address or is identified by a bit 1 in the bitmap. In other embodiments, a member AP of the MASS can respond with a probe response after receiving a probe request targeted to a MASS ID.

[0119]

[0161] Alternatively or additionally, a probe request sent by a non-AP STA may also include a transmit power and a receive power threshold used to transmit the probe request. A target member AP from a target MASS, etc., that receives a probe request frame below the receive power threshold may ignore the probe request frame. Otherwise, the AP may respond with a probe response.

[0120]

[0162] A non-AP STA may have a list of parameters, such as MCS, RSSI, or other channel quality parameters, of member APs in a MASS that it discovers after monitoring the medium and receiving a targeted probe response, beacon, short beacon, FILS discovery frame, or other type of frame from a member AP. A non-AP STA may select one or more member APs in a MASS as its designated AP. One of the designated APs may act as a primary AP, while one or more APs may act as one or more secondary APs for the STA.

[0121]

[0163] If an AP and / or MASS meets the requirements of a non-AP STA, such AP and / or MASS can send an association request or a multi-AP association request that includes a multi-AP selection element to the selected AP. Figure 11 shows an example of a multi-AP selection element 1100 that can be used in any combination with the other embodiments described herein.

[0122]

[0164] The multiple AP selection element 1100 may include an element ID 1105 and element ID extension field 1115, a length field 1110, a multiple AP capability field 1120, a multiple AP requested services field 1125, an AP information count field 1130, and N AP information fields 1135, 1140. The combination of the element ID 1105 and the element ID extension field 1115 may indicate that the current element is the multiple AP selection element 1100. The length field 1110 may be used to indicate the length of the multiple AP selection element 1100. The multiple AP capability field 1120 may be used to indicate the STA's capabilities for multiple AP transmission / reception, including, for example, multiple AP joint transmission, multiple AP HARQ, multiple AP MIMO, multiple AP MU-MIMO, dynamic AP selection, multiple AP roaming, and multiple AP cooperative beamforming. The multi-AP requested service field 1125 may indicate the multi-AP services requested by the transmitting AP, including multi-AP joint transmission, multi-AP HARQ, multi-AP MIMO, multi-AP MU-MIMO, dynamic AP selection, multi-AP roaming, and multi-AP cooperative beamforming. The AP information count field 1130 may indicate the number of AP information fields included. The N AP information fields 1135, 1140 may contain information about the member APs for which multi-AP service is requested. Examples of the N AP information fields 1135, 1140 may include, but are not limited to, an AP ID 1150, a primary / secondary indicator 1155, a received power / channel quality indication 1160, and a mandatory indicator 1165. The AP ID 1150 may be the MAC address or order of the member AP within the MASS. The primary / secondary indicator 1155 may indicate a request for the AP to be admitted as a primary AP or, if applicable, as a secondary AP. The received power / channel quality indication field 1160 may indicate the channel quality between the AP and the transmitting STA, such as RSSI, RSRP, or RCPI. The mandatory indicator 1165 may indicate whether the transmitting STA is requesting that the target AP be mandatory or be allowed optionally.Alternatively or additionally, if the STA does not have sufficient information about member APs of the target MASS, the STA may indicate in the multi-AP selection element 1100 that it is requesting information about other member APs that support the multi-AP service. The AP may respond with a frame such as a probe response or beacon, short beacon, or FILS discovery frame that may include a multi-AP element to provide the requested information.

[0123]

[0165] In an embodiment, a non-AP STA can transmit one or more association request frames or multi-AP association request frames to all desired member APs, including the multi-AP selection element. After receiving the association request frame or multi-AP association request frame, the AP can determine whether to grant association as a primary / secondary AP as requested. Alternatively or additionally, the primary AP identified in the probe request frame can forward the association request to any secondary APs identified in the association / authentication request or multi-AP association / authentication request. If the primary AP is a slave AP, the primary AP can forward the association / authentication request for one or more secondary APs to the master AP, which can associate with the secondary APs on behalf of the STA. Such forwarding and response can occur over a wireless medium, use a wired backbone, use a different band, or use a frequency channel. When the secondary APs respond, the primary AP can transmit a multi-AP association / authentication response frame to the requesting STA. The multi-AP association / authentication response frame may include status regarding whether association / authentication with the primary and secondary APs was successful.

[0124]

[0166] In one embodiment, a non-AP STA may request association with a first AP, such as a selected primary AP. Once the STA is associated with the primary AP, the STA may receive a list of other member APs in the same MASS in the AP's beacon, short beacon, probe response, association response, or other type of frame. The STA may transmit one or more probe request frames targeted to one or more IDs, such as the SSID of the MASS and / or the MAC address of the member AP targeted by the STA. In another embodiment, the STA may transmit a probe request frame targeted to a MASS ID, and the probe request frame may include a bitmap with each bit set to 1, which may indicate the member APs associated with the order of member APs in the MASS for which a probe response is requested. The probe request frame may also include an indication that it is a probe request for the MASS. After receiving a probe request frame targeted to the MASS ID and / or its own MAC address, or at least one of them identified by a 1 in the bitmap, the member APs in the MASS may respond with a probe response frame.

[0125]

[0167] Alternatively or additionally, a probe request frame transmitted by a non-AP STA may also include a transmit power and a receive power threshold used to transmit the probe request, and any targeted member AP receiving the probe request frame below the receive power threshold may ignore the probe request frame.

[0126]

[0168] A non-AP STA may have a list of parameters such as MCS, RSSI, or other channel quality parameters of the member APs of the MASS that it discovers after monitoring the medium and receiving a targeted probe response frame. The STA can select one or more member APs in the MASS as its secondary APs.

[0127]

[0169] The non-AP STA may then transmit a frame, such as a multi-AP association request frame or a multi-AP service negotiation frame, to its primary AP. The multi-AP association request frame or multi-AP service negotiation frame may include a multi-AP selection element that may indicate a request for a particular multi-AP service and / or the number of secondary APs. The primary AP may then determine whether to provide multi-AP service to the STA. Alternatively, or in addition, such a determination may be made at the master AP of the MASS. The primary AP may forward the multi-AP request to any secondary APs identified in the multi-AP association request frame or multi-AP negotiation frame. If the primary AP is a slave AP, the primary AP may forward the multi-AP association request frame or multi-AP service negotiation request for one or more secondary APs to the master AP, which may conduct multi-AP service negotiations with the secondary APs on behalf of the STA. Such forwarding and response may occur over a wireless medium (e.g., over-the-air), use a wired backbone, use a different band, or use a different frequency channel. When the secondary AP responds, the primary AP can send a multiple AP association response frame or a multiple AP service negotiation response frame to the requesting STA, which frame includes status indicating (1) whether multiple AP services are provided, (2) which multiple AP services are provided, (3) which member APs are successfully added as secondary APs for the STA, and (4) which multiple AP services are provided.

[0128]

[0170] For cooperative OFDMA, in embodiments, a STA may autonomously estimate whether it is located at the edge of a BSS (i.e., a BSS-edge STA) or at the center of a BSS (i.e., a BSS-center STA) relative to its primary or serving BSS. For example, path loss, geography, or BSS location may be used for the estimation. However, in dense networks such as apartment buildings with many overlapping basic service sets (OBSSs), interactions between BSSs may determine whether a STA should be placed in a BSS-edge group. This determination may require a procedure involving the BSSs and the STA. Throughout this disclosure, the terms BSS-center STA and cell-center STA may be used interchangeably. Throughout this disclosure, the terms BSS-edge STA and cell-edge STA may be used interchangeably.

[0129]

[0171] In one embodiment, multiple APs, such as AP1 and AP2, may need to cooperate to decide to implement cooperative OFDMA. In one example, AP1 may review its multi-AP associated STAs (i.e., STAs that associate with multiple APs) and identify AP2 as the AP with which to cooperate. The AP may automatically designate any STAs identified as multi-AP associated STAs as BSS edge STAs. Alternatively or additionally, the APs may cooperatively transmit information to assist STAs in estimating whether they are BSS edge STAs or BSS center STAs.

[0130]

[0172] In one embodiment, the following steps may be performed for cooperative edge / center discovery: In step 1, AP1 may send a cooperation request frame to AP2 (e.g., over the air or via a backhaul link). In step 2, if AP2 is willing and able to collaborate with AP1, AP1 may receive a cooperation acknowledgement frame from AP2. In step 3, AP1 may send a Null Data Packet Announcement (NDPA) frame to AP2 and STAs in its BSS (i.e., both non-multiple AP associated STAs and multi-AP associated STAs). In one example, AP2 may send an NDPA frame as an ACK to AP1 and to announce the upcoming NDP to STAs in its BSS (i.e., both non-multiple AP associated STAs and multi-AP associated STAs). This procedure may be used for general cooperation or joint transmission. Alternatively or additionally, the steps described in this embodiment may be replaced by the multi-AP association procedure described above.

[0131]

[0173] In step 4, AP1 and AP2 may transmit NDPs to STAs within their own BSSs. In one embodiment, AP1 and AP2 may transmit NDPs simultaneously. In such an embodiment, the difference in received RSSI between the NDP and NDP may indicate whether the STA is a BSS-edge STA or a BSS-center STA. If the difference in RSSI between the NDP and NDP is less than a threshold, this may indicate that a signal from AP2 is not being received, and the STA may be considered a BSS-center STA. If the difference in RSSI between the NDP and NDP is greater than a threshold, the STA may be considered a BSS-edge STA.

[0132]

[0174] In another embodiment, the NDP frames from the APs may be orthogonal. In one example, the NDP frames may be orthogonal in time with the NDP from AP2, which sent a SIFS after the NDP from AP1. In another example, the NDP frames may be orthogonal in frequency (e.g., interlaced in frequency). The location of the NDP frames may depend on the NDP subcarrier spacing (e.g., Ng). As an example, if Ng is equal to four (NG=4) with an interlace value equal to two (interlace=2), AP1 may transmit its NDP on subcarriers 0, 4, 8, ..., while AP2 may transmit its NDP on subcarriers 2, 6, 10, .... In another example, the NDP frames may be transmitted as an orthogonal or semi-orthogonal sequence.

[0133]

[0175] Each STA can measure the RSSI of the NDP signal from each AP and estimate the RSSI difference / ratio between the signals from its primary AP (e.g., AP1) and secondary AP (e.g., AP2). If the RSSI difference / ratio is less than a threshold, the STA can be considered a BSS edge STA. If the RSSI difference / ratio is greater than a threshold, the STA can be considered a BSS center STA.

[0134]

[0176] In step 5, once the STA identifies whether it is a BSS-edge STA or a BSS-center STA, it can feed back that information to the AP. In one example, the AP can poll each STA for feedback information. In another example, the STA can provide feedback information using an NDP feedback report. In this example, the AP can transmit an NDP Feedback Report Poll (NFRP) trigger frame with a parameter indicating a request for information on whether the STA is a BSS-center STA or a BSS-edge STA. In another example, the NFRP trigger frame can carry one or more additional parameters indicating cutoff values ​​for cell-center / cell-edge classification (e.g., edge Tx power, signal-to-interference ratio (SIR) cutoff value, or RSSI difference). For the duration of the SIF after receiving the NFRP trigger frame, the STA can transmit the required information in the NDP feedback report. In one example, only certain types of STAs can transmit information, meaning that STAs that do not transmit NDP feedback reports are of other types. The AP may recognize STAs that have transmitted an NDP feedback report as BSS-center STAs / BSS-edge STAs, and STAs that have not transmitted an NDP feedback report as BSS-edge STAs / BSS-center STAs. In another example, all STAs may send feedback with information specifying the type of STA (e.g., BSS-edge STA or BSS-center STA). In another example, STAs may use HE-CQI reports to feed back RSSI or RSSI differences, which may be averaged over the entire bandwidth for a single space-time subband (STS).

[0135]

[0177] From the STA's perspective, a STA associated with multiple APs and identifying its primary and secondary APs can first identify the multi-AP discovery NDPA from AP1. The STA can then identify the multi-AP discovery NDPA from AP2. The STA can then estimate the required measurements from the NDP. For example, the STA can identify the SIR NDP and estimated SIR (RSSI1-RSSI2, per tone or average). The STA can identify the SIR cutoff for determining center / edge from the NFRP. The STA can send a signal including a center / edge indicator to the AP. Alternatively or additionally, the STA can send the SIR in an HE-CQI frame to enable the AP to determine whether the STA is a BSS-center or BSS-edge STA.

[0136]

[0178] 12 illustrates an example of scheduled / random-access cooperative OFDMA 1200, which can be used in any combination with other embodiments described herein. Data transmission can be scheduled or random-access cooperative OFDMA. For scheduled data transmission in the downlink and uplink, APs 1214a and 1214b can schedule appropriate STAs within corresponding resources using transmit power control or cooperative beamforming / nulling (CB / N). Assuming that AP1 1214a is assigned RU1 1205 and AP2 1214b is assigned RU2 1220, cell-edge STAs can be assigned within RU1 1205 by AP1 1214a and within RU2 1220 by AP2 1214b, while cell-center STAs can be assigned in both RU1 1205 and RU2 1210 by AP1 1214a and in both RU1 1215 and RU2 1220 by AP2 1214b. Cell center STAs may transmit similarly to power control to limit the amount of interference with cell center / edge STAs of other BSSs. Cell center STAs may transmit using a CB / N scheme to limit the amount of interference with cell center / edge STAs of other BSSs, as described in more detail below.

[0137]

[0179] For random access (RA) data transmission in the uplink, AP1214a and 1214b can use cooperative uplink OFDM random access. As shown in FIG. 12 , AP1 1214a may allow both edge STAs and central STAs to configure RU1 1205 as a qualified RA-RU (e.g., an RA-RU for which an HE STA can generate an HE TB PPDU). AP1 1214a may configure RU2 1210 as a qualified RA-RU only for the central STA. Similarly, AP2 1214b may allow both edge STAs and central STAs to configure RU2 1220 as a qualified RA-RU (e.g., an RA-RU for which an HE STA can generate an HE TB PPDU). AP2 1214b may configure RU1 1215 as a qualified RA-RU only for the central STA.

[0138]

[0180] To simplify signaling, in some embodiments, the center STAs and edge STAs can be manually assigned to group IDs, which can be assigned to specific RA-RUs. Alternatively or additionally, the cell edge STAs and cell center STAs can be assigned to specific AIDs / AID groups, and the RA-RUs can be assigned to those specific AIDs / AID groups.

[0139]

[0181] 13 is a system diagram illustrating an example 1300 of multiple AP association, cell center / cell edge discovery, and data transmission, which may be used in any combination with other embodiments described herein. In this example, assume that STA1 1302a is the BSS center STA for AP1 1314a, STA2 1302b is the BSS edge STA for AP1 1314a, STA3 1302c is the BSS center STA for AP2 1314b, and STA4 1302d is the BSS edge STA for AP2 1314b. Also assume that STA2 1302b and STA4 1302d are located at the cell edges from AP1 1314a and AP2 1314b. 13, during the multi-AP association phase 1301, STA1 1302a receives beacon frame 1305a from AP1 1314a and can perform an association procedure with AP1 1314a. STA2 1302b, located at the cell edge from AP1 1314a and AP2 1314b, receives beacon frames 1305a, 1305b from both AP1 1314a and AP2 1314b and can perform a multi-AP association procedure with AP1 1314a and AP2 1314b as described above. Similarly, STA3 1302c receives beacon frame 1305b from AP2 1314b and can perform an association procedure with AP2 1314b. STA4 1302d, located at the cell edge from AP1 1314a and AP2 1314b, receives both beacon frames 1305a, 1305b from AP1 1314a and AP2 1314b and can perform multi-AP association procedures with AP1 1314a and AP2 1314b as described above.

[0140]

[0182] During or after the multi-AP association phase 1301, AP1 1314a and AP2 1314b can perform an AP coordination procedure 1302 to ensure that APs 1314a, 1314b can provide multi-AP operation to STA2 1302b and STA4 1302d. The AP coordination procedure 1302 can be performed in a centralized or distributed manner. In one example, as shown in step 1320, AP1 1314a and AP2 1314b can negotiate fractional frequency reuse (FFR) through a centralized controller that communicates with AP1 1314a and AP2 1314b via a backhaul link or OTA signaling. In another example, as shown in step 1325, AP1 1314a and AP2 1314b can negotiate fractional frequency reuse (FFR) directly via a backhaul link or OTA signaling. In particular, AP1 1314a may send a control message to AP2 1314b and receive an ACK for FFR negotiation from AP2 1314b.

[0141]

[0183] During the center / edge discovery phase 1303, AP1 1314a can transmit an NDPA frame 1330a to AP2 1314b and the STAs 1302a, 1302b in its BSS. Similarly, AP2 1314b can transmit an NDPA frame 1330b to AP1 1314a and the STAs 1302c, 1302d in its BSS. AP1 1314a can then transmit a signal-to-noise-and-interference ratio (SIR) NDP frame 1335a to the STAs 1302a, 1302b in its BSS, thereby allowing the STAs 1302a, 1302b to estimate the SIR, e.g., the difference in RSSI between the received NDPA frame 1330a and the received SIR NDP frame 1335a. Similarly, AP2 1314b can transmit an SIR NDP frame 1335b to STAs 1302c, 1302d in its BSS, allowing the STAs 1302c, 1302d to estimate the SIR, e.g., the difference in RSSI between the received NDP frame 1330b and the received SIR NDP frame 1335b. At this point, the STAs 1302a, 1302b, 1302c, 1302d can identify whether they are cell-edge or cell-center STAs, e.g., based on the estimated SIR. AP1 1314a can transmit an NDP Feedback Report Poll (NFRP) frame 1340a to STA1 1302a and STA2 1302b to request information about whether STAs 1302a, 1302b are cell-center or cell-edge STAs. Upon receiving the NFRP frame 1340a, STA1 1302a can respond with an NDP feedback frame 1345a indicating that it is a cell-center STA, and STA2 1302b can respond with an NDP feedback frame 1345b indicating that it is a cell-edge STA. Similarly, AP2 1314b can also send an NFRP frame 1340b to STA3 1302c and STA4 1302d to request information about whether STAs 1302c and 1302d are cell-center or cell-edge STAs.Upon receiving NFRP frame 1340b, STA3 1302c can respond with NDP feedback frame 1350a indicating that it is a cell-center STA, and STA4 1302d can respond with NDP feedback frame 1350b indicating that it is a cell-edge STA.

[0142]

[0184] During the data transmission phase 1304, AP1 1314a and AP2 1314b may transmit random access trigger frames to STAs 1302a, 1302b, 1302c, and 1302d to allocate resource units (RUs) for random access. For example, AP1 1314a may send a UL-OFDMA random access (UORA) trigger frame 1355a to STA1 1302a and STA2 1302b to indicate that STA1 1302a (i.e., a cell-center STA) is allocated to use RU1 and RU2, and that STA2 1302b (i.e., a cell-edge STA) is allocated to use RU1. Upon receiving the UORA trigger frame 1355a, STA1 1302a can transmit data using RU1 and RU2 1360a, and STA2 1302b can transmit data to one or more APs 1314a, 1314b using RU1 1365. Similarly, AP2 1314b can send a UORA trigger frame 1355b to STA3 1302c and STA4 1302d to indicate that STA3 1302c (i.e., a cell-center STA) is assigned to use RU1 and RU2, and that STA4 1302d (i.e., a cell-edge STA) is assigned to use RU1. Upon receiving the UORA trigger frame 1355b, STA3 1302c can transmit data using RU1 and RU2 1370, and STA4 1302d can transmit data to one or more APs 1314a, 1314b using RU1 1375.

[0143]

[0185] In one embodiment, in cooperative OFDMA, a set of protection resources or protection RUs may be negotiated among resources allocated for cooperative OFDMA, which may allow for some inter-carrier interference without requiring tight synchronization.

[0144]

[0186] 14 shows an example of a guard band 1400 for fractional coordinated OFDMA that can be used in any combination with the other embodiments described herein. As shown in FIG. 14 , in AP1, RU1 1405 is allocated to cell-edge STAs and cell-center STAs, and RU2 1415 is allocated to cell-center STAs. In this example, the resources allocated to the cell-edge STAs (i.e., RU1 1405) may have a set of protected resources or protected RUs 1410. Similarly, in AP2, RU2 1430 is allocated to the cell-edge STAs and cell-center STAs, and RU1 1415 is allocated to the cell-center STAs. The resources allocated to the cell-edge STAs (i.e., RU2 1430) may have a set of protected resources or protected RUs 1430.

[0145]

[0187] In one embodiment, cyclic prefix (CP) length modification may be used to ensure that the CP length is greater than the sum of (1) the maximum timing offset of STAs associated with BSS 1, (2) the maximum timing offset of STAs associated with BSS 2, and (3) the maximum channel impulse response (CIR) lengths of BSS 1 and BSS 2. Although not shown in the example above, this scheme can be applied to more than two BSSs by summing the parameters of all BSSs in the cooperating BSS set.

[0146]

[0188] In IEEE 802.11ax, a STA transmitting an HE TB PPDU in response to a triggering PPDU from an AP, such as a trigger frame or a frame with a trigger response scheduling (TRS) control subfield, can ensure that the arrival time of the HE TB PPDU at the AP is within ±0.4 μs of TXTIME + aSIFSTime + RTD from the start of transmission of the triggering PPDU, where TXTIME can be that of the triggering PPDU and RTD can be the round-trip delay between the AP and the STA. In one embodiment, the existing CP length can be modified in cooperative OFDMA to ensure it is sufficient (e.g., the allowed time can be halved for a 2-BSS cooperative set). Additionally or alternatively, the allowed time can remain constant for a 2-BSS cooperative set, but the maximum CP length can be doubled. In a simple example, six possible CP lengths can be used instead of the three possible CP lengths in IEEE 802.11ax.

[0147]

[0189] In another embodiment, to reduce timing differences between STAs, each AP can calibrate the timing of the responses of STAs in its own BSS and send timing advance / retard requests to each STA. The maximum timing difference can then be sent to each AP to enable each AP to estimate the CP to use. The information can be sent to the centralized AP via the backhaul link, and the centralized AP can estimate a common CP and send the information to each AP. Alternatively or additionally, the information can be sent to the centralized AP via the backhaul link, and the centralized AP can estimate a BSS- and / or STA-specific CP that can be sent to each AP. Alternatively or additionally, the information can be sent to each AP in the cooperating set, and the APs can then independently set their own CPs. The information can be sent via the backhaul link or over the air (OTA) signal. For OTA, in one example, the information can be transmitted by the edge STAs in a dedicated frame or an extremely high throughput (EHT) preamble to allow neighboring APs in the set to overhear the information.

[0148]

[0190] In one embodiment, the cooperative OFDMA synchronization trigger frame may be transmitted from a master AP. The master AP may be a separate AP that coordinates all APs in a cooperating set, such as a set of BSSs, that are involved in cooperative OFDMA transmission. Alternatively or additionally, the master AP may be one of the APs in the cooperating set. This AP may be predetermined, selected randomly, or elected by the APs in the cooperating set.

[0149]

[0191] In another embodiment, a cooperative OFDMA synchronization trigger and / or sequence can be used. Upon receiving a master trigger frame, all APs in a group can transmit triggers to their respective STAs with a predetermined timing tolerance to ensure orthogonality. In some embodiments, the master trigger frame can be transmitted before any individual AP transmits its individual trigger frame. Additionally or alternatively, the master trigger frame can be transmitted at a configurable interval. Individual trigger frames can be transmitted at specific times after receiving the master trigger frame. This interval can be statically or dynamically configured. If dynamically configured, an individual AP can request a master trigger transmission provided its inter-carrier interference (ICI) exceeds a predetermined threshold.

[0150]

[0192] In another embodiment, the master AP may transmit a specific synchronization signal or sequence rather than a separate master trigger frame to initiate the initiation of the trigger for each AP. In some embodiments, the master AP may transmit a trigger frame to all end STAs, requesting a calibration transmission. Other cooperative APs may then calibrate the start of their own trigger frames based on the timing difference between receiving the end of the master trigger frame and the beginning of their end STA's response. Thus, upon receiving a master trigger frame from the master AP, cooperative APs may be able to transmit their own trigger frames in a manner that ensures that the transmission frames in their BSSs are synchronized with the master AP's trigger.

[0151]

[0193] In another embodiment, the master trigger frame may include information regarding the maximum length of the expected trigger frame. If each AP's trigger frame is less than the required length, the AP may add padding to the trigger frame to ensure that transmissions begin in a manner that ensures orthogonality. In some embodiments, the padding may be AP-specific to provide timing advance / retardation and allow synchronization of transmissions within multiple BSSs.

[0152]

[0194] Cooperative beamforming / cooperative nulling (CB / CN) embodiments are described herein. In cooperative beamforming, the transmitting device (or STA), the desired device (or STA), and the undesired device (or STA) can decide the procedure to be used and the type of feedback required. Various architectures and embodiments that can be used are described herein.

[0153]

[0195] 15 illustrates an example of a downlink-downlink CB / CN architecture 1500 that can be used in any combination with the other embodiments described herein. As shown in FIG. 15, in this downlink-downlink CB / CN, the transmitting device can be both AP1 1514 and AP2 1514b, and the desired and undesired devices can be both STA1 1502a and STA2 1502b.

[0154]

[0196] 16 illustrates an example of an uplink-uplink CB / CN architecture 1600 that can be used in any combination with the other embodiments described herein. As shown in FIG. 16, the transmitting device can be both STA1 1602a and STA2 1602b, and the desired and undesired devices can be both AP1 1614a and AP2 1614b.

[0155]

[0197] 17 illustrates an example of an uplink-downlink CB / CN architecture 1700 that can be used in any combination with the other embodiments described herein. As shown in FIG. 17, in this uplink-downlink CB / CN, the transmitting device can be STA1 1702a, the desired device can be AP1 1714a, and the undesired device can be STA2 1702b. In contrast, in a downlink-uplink CB / CN, the transmitting device can be AP2 1714b, the desired device can be STA2 1702b, and the undesired device can be AP1 1714a.

[0156]

[0198] Embodiments of channel information acquisition for downlink-downlink CB / CN and downlink-uplink CB / CN are described herein. In cooperative beamforming or nulling, the transmitting device may need channel feedback for channels to both desired and undesired receivers. In downlink-downlink CB / CN, this channel feedback information may be received from desired and undesired STAs. In one example, the AP may send an NDPA / NDP to each STA and individually request or poll for feedback from each STA. However, for downlink transmissions, a trigger frame-based NDPA / NDP procedure may be used to obtain feedback from each STA in a more efficient manner.

[0157]

[0199] 18 shows an example of a singling flow 1800 for independent NDPA / NDP and trigger-based feedback, which may be used in combination with any of the other embodiments described herein. As shown in FIG. 18, each AP (e.g., AP1 1814a and AP2 1814b) can independently transmit NDPA / NDP frame combinations (e.g., NDP1 1805 and NDP1 1810, and NDPA2 1815 and NDP2 1820) to STAs (e.g., STA1 1802a and STA2 1802b) along with independent trigger frames (e.g., trigger frame 1825 and trigger frame 1840) to each STA to obtain feedback (e.g., FB1 1830, FB2 1835, FB1 1845, and FB2 1850). Because each STA (e.g., STA1 1802a and STA2 1802b) is associated with both APs (e.g., AP1 1814a and AP2 1814b), each AP may be able to trigger the STAs (e.g., in an OFDMA manner) for feedback.

[0158]

[0200] NDPA frames (e.g., NDPAl 1805 and NDPA2 1815) may indicate a request for the type of feedback to acquire the channel from the AP and the STAs that should measure NDP frames (e.g., NDP1 1810 and NDP2 1820). NDPA frames (e.g., NDPAl 1805 and NDPA2 1815) may indicate measurement of the channel from the AP to the desired device and full channel feedback. NDPA frames (e.g., NDPAl 1805 and NDPA2 1815) may indicate measurement of the channel from the AP to the undesired device and full channel feedback. NDPA frames (e.g., NDPAl 1805 and NDPA2 1815) may indicate measurement of the channel from the AP to the undesired device and partial channel feedback. Partial information may be defined as any information that is not the full IEEE 802.11 channel information feedback requested for the desired channel. Partial channel feedback may be used to determine a null space to which the designed precoder should be orthogonal and therefore may not require detailed information to improve performance. Examples of partial channel feedback may include, but are not limited to, reduced quantization channel feedback, increased subcarrier sampling (Ng) channel feedback, channel correlation based channel feedback, and sector or codebook based channel feedback.

[0159]

[0201] A trigger frame (e.g., trigger frame 1825 or trigger frame 1840) from each AP may indicate how feedback from each receiving device (e.g., FB1 1830, FB2 1835, FB1 1845, and FB2 1850) will be transmitted to the announcer. The feedback (e.g., FB1 1830, FB2 1835, FB1 1845, and FB2 1850) may be separated by frequency (e.g., OFDMA), separated by time (e.g., time staggered), or separated by space (e.g., uplink MU-MIMO). In this case, each AP can request information from each STA independently.

[0160]

[0202] 19 shows an example 1900 of master trigger-based NDPA / NDP and master trigger-based feedback, which can be used in any combination with other embodiments described herein. As shown in FIG. 19, a master AP (e.g., AP1 1914a) can transmit an NDPA trigger frame 1905 to a secondary / slave AP (e.g., AP2 1914b) and both STAs 1902a, 1902b to indicate the start of an NDP measurement campaign. Both APs 1914a, 1914b can transmit NDP frames (e.g., NDP1 1910 and NDP2 1915) to the STAs 1902a, 1902b. The NDPs (e.g., NDP1 1910 and NDP2 1915) can be separable at the STAs 1902a, 1902b. The NDPs (e.g., NDP1 1910 and NDP2 1915) can be transmitted at different times. For example, AP1 1914a transmits NDP1 1910, then AP2 1914b transmits NDP2 1915. The NDPs (e.g., NDP1 1910 and NDP2 1915) may be transmitted simultaneously but using different subcarriers. In one example, both AP1 1914a and AP2 1914b set Ng=x (e.g., determined by the NDPA trigger frame 1905) but may be offset so as to not overlap. For example, with Ng=4, AP1 1914a may use subcarrier indices 0, 4, ..., while AP2 1914b may use subcarrier indices 2, 6, .... This configuration may require tight synchronization between AP1 1914a and AP2 1914b (similar to joint precoding) to ensure there are no frequency, time, or synchronization offsets at the receiving STAs 1902a, 1902b. A master AP (e.g., AP1 1914a) can transmit a trigger frame 1920 to both STAs 1902a, 1902b and a slave AP (e.g., AP2 1914b) to feed back desired and undesired information to both APs 1914a, 1914b. For example, STA1 1902a can transmit FB1 1925 to AP1 1914a, and STA2 1902b can transmit FB2 1930 to AP2 1914b.

[0161]

[0203] In scenarios where there may be an AP-STA group, such as three APs and three STAs, this operation may be implemented in a pairwise fashion where only two APs / STAs may be allowed to transmit simultaneously. Additionally or alternatively, unidirectional and two undesired feedback packets may be transmitted using precoders designed to operate within the null spaces of the two undesired channels.

[0162]

[0204] 20 shows an example 2000 of an NDP feedback request from an AP that can be used in any combination with the other embodiments described herein. As shown in FIG. 20, AP1 2014a can send NDPAl 2005 and NDP1 2010 to AP2 2014b and both STAs 2002a, 2002b to indicate the start of an NDP measurement campaign. Similarly, AP2 2014b can send NDPAl 2015 and NDP2 2020 to AP1 2014a and both STAs 2002a, 2002b to indicate the start of an NDP measurement campaign. AP1 2014a can then send a trigger frame 2025 to AP2 2014b and both STAs 2002a, 2002b to feedback desired and undesired information to AP1 2014a. For example, upon receiving trigger frame 2025, AP2 2014b can send FB3 2030 to AP1 2014a, STA1 2002a can send FB1 2035 to AP1 2014a, and STA2 2002b can send FB2 2040 to AP1 2014a. AP2 2014b can then send trigger frame 2045 to AP1 2014a and both STAs 2002a, 2002b to feedback desired and undesired information to AP2 2014b. For example, upon receiving trigger frame 2045, AP1 2014a may send FB3 2050 to AP2 2014b, STA1 2002a may send FB1 2055 to AP2 2014b, and STA2 2002b may send FB2 2060 to AP2 2014b. The example shown in Figure 20, where an AP requests feedback from another AP, may be used for downlink-uplink CB / CN.

[0163]

[0205] 21 shows an example NDP trigger 2100 for implicit multi-AP sounding, which may be used in any combination with other embodiments described herein. As shown in FIG. 21, a master AP (e.g., AP1 2114a) may transmit an NDP trigger frame 2105 to a secondary or slave AP (e.g., AP2 2114b) and both STAs 2102a, 2102b to indicate the start of implicit NDP measurements. The STAs 2102a, 2102b may transmit NDP frames (e.g., NDP1 2110 and NDP2 2115) or sounding frames to the APs 2114a, 2114b so that the APs 2114a, 2114b can estimate the uplink channel and derive the downlink channel from the uplink channel. Upon receiving an NDP frame (e.g., NDP1 2110 and NDP2 2115) or a sounding frame, the APs 2114a, 2114b can respond to the STAs 2102a, 2102b with ACK frames 2120, 2125. In a scenario where there may be an AP-STA group (e.g., three APs and three STAs), the trigger frame can indicate the beginning of each uplink STA transmission, or can indicate that the STAs are transmitting simultaneously to the AP.

[0164]

[0206] Embodiments of channel information for uplink-uplink CB / CN and uplink-downlink CB / CN are described herein. In uplink-uplink CB / CN, each STA may need to have knowledge of the channels to its desired and undesired APs. When trigger frames are used in the downlink (i.e., triggers are sent from the AP to the STA), the NDPA / NDP / feedback procedures described in the downlink-downlink CB / CN scenario may need to be modified. In one example, reciprocity can be used (e.g., the channel obtained during DL / DL CB / CN at the STA may be suitable for the uplink, and the above NDPA / NDP procedures can be used without any feedback required). NDPA can be used to indicate that the following NDP can be used for uplink cooperative beamforming measurements.

[0165]

[0207] FIG. 22 shows an example 2200 of independent NDPA / NDP for UL / UL CB / CN based on reciprocity, which can be used in any combination with other embodiments described herein. Each of STAs 2202a and 2202b can obtain knowledge of the channels, e.g., downlink CB / CN, to its desired and undesired APs among APs 2214a and 2214b. As shown in FIG. 22, AP1 2214a can transmit NDPA1 2205 along with channel information to STAs 2202a and 2202b to indicate that the next NDP1 2210 will be used for uplink cooperative beamforming measurements. Similarly, AP2 2214b can transmit NDPA2 2215 to STAs 2202a and 2202b to indicate that the next NDP2 2220 will be used for uplink cooperative beamforming measurements.

[0166]

[0208] Figure 23 shows an example 2300 of master trigger-based NDPA / NDP for UL / UL CB / CN, which can be used in any combination with other embodiments described herein. As shown in Figure 23, a master AP (e.g., AP1 2314a) can transmit an NDPA trigger frame 2305 to a secondary / slave AP (e.g., AP2 2314b) and both STAs 2302a, 2302b to indicate that the next NDP frames 2310, 2315 will be used for uplink cooperative beamforming measurements. Both APs 2314a, 2314b can transmit NDP frames (e.g., NDP1 2310 and NDP2 2315) to the STAs 2302a, 2302b. The NDPs 2310, 2315 can be separable at the STAs 2302a, 2302b. The NDPs 2310, 2315 can be transmitted at different times or simultaneously but using different subcarriers.

[0167]

[0209] Figure 24 shows an example 2400 of STA-initiated channel acquisition, which may be used in any combination with the other embodiments described herein. When reciprocity does not apply as shown in Figure 24, the STAs 2402a, 2402b can initiate channel acquisition for the UL / UL CB / CN case by sending NDPs (e.g., NDP1 2410 and NDP2 2420) to the APs 2414a, 2414b and requesting feedback from the APs 2414a, 2414b. In one example, each STA 2402a, 2402b can send an NDPA 2405, 2415 to the APs 2414a, 2414b and request feedback 2430, 2435 from the APs 2414a, 2414b. In particular, STA1 2402a may transmit NDPAl 2405 to AP 2414a, 2424b to obtain channel information and may transmit NDP1 2410 to AP 2414a, 2424b to request feedback. Similarly, STA2 2402b may transmit NDPAl 2415 to obtain channel information and may transmit NDP2 2420 to AP 2414a, 2424b to request feedback. Alternatively or additionally, as shown in FIG. 24, each AP 2414a, 2424b may transmit a feedback trigger frame 2425, 2435 or an announcement frame to STA 2402a, 2402b to provide feedback 2430, 2440 with channel information for desired and undesired STAs.

[0168]

[0210] 25 shows an example of AP-initiated channel acquisition 2500, which may be used in any combination with the other embodiments described herein. In a scenario where there may be many STAs and the STA-initiated method may incur a lot of overhead, the master AP (e.g., AP1 2514a) can trigger the secondary AP (e.g., AP2 2514b) and all STAs in the joint BSS (e.g., STA1 2502a, STA2 2502b, STA3 2502c, and STA4 2502d) to send a series of NDPs (e.g., NDP1 2515, NDP2 2520, NDP3 2525, and NDP4 2530) to both APs 2514a, 2514b. As shown in FIG. 25, APs 2414a, 2424b can transmit feedback trigger frames 2535, 2545 or announcement frames to STAs 2502a, 2502b, 2502c, 2502d, and provide feedback 2540, 2550 having desired and undesired channels to STAs 2502a, 2502b, 2502c, 2502d.

[0169]

[0211] In the UL-DL CB / CN, the NDPA can address the unwanted STA and request feedback from the STA at a later point in time.

[0170]

[0212] As mentioned above, the AP may need to know DL channel state information (CSI) for all STAs. In an embodiment, knowing DL channel state information (CSI) for all STAs may be done using implicit DL channel acquisition, for example, where the AP can acquire the DL channel from the UL channel.

[0171]

[0213] 26 illustrates an example 2600 of implicit DL channel acquisition, which may be used in combination with any of the other embodiments described herein. As shown in FIG. 26, AP1 2614a acquires a UL (e.g., normalized) channel.

number

number

number

number

number

number

[0172]

[0214] To obtain α1 and α2 or α1 / α2, the STAs 2602a, 2602b can use a deterministic power (e.g., maximum power) or power spectral density (e.g., power per Hz or power per 26-tone RU) in the UL to respond to a channel acquisition frame (e.g., an NDP, NDPA, or trigger frame) transmitted from AP1 2614a. The deterministic power or power spectral density value can be signaled in the channel acquisition frame if it is not maximum power. In this case, all STAs 2602a, 2602b can transmit signals using the same power, so the path loss can be measured at the APs (including AP1 2614a).

[0173]

[0215] The STAs 2602a, 2602b can report their maximum power output in a MAC frame, such as an association frame or a setup frame. If the STAs 2602a, 2602b are power controlled (e.g., can use different transmit powers), the STAs 2602a, 2602b can indicate their transmit power or transmit power spectral density while transmitting a UL PPDU in a MAC frame or through PHY signaling, such as in one of the PHY headers, such as a SIG field. The STAs 2602a, 2602b can indicate their power headroom while transmitting a UL PPDU in a MAC frame or through PHY signaling, such as in one of the PHY headers, such as a SIG field. If the channel acquisition signal from the AP (including AP1 2614a) includes the transmit power used at the AP (including AP1 2614a), the STAs 2602a, 2602b can generate DL path losses from various APs and feed them back to the AP (including AP1 2614a) using the UL channel or SIG field.

[0174]

[0216] Embodiments of mesh sounding procedures are described herein. By enabling simultaneous use of UL and DL by multiple APs distributed within an area, network latency can be reduced. FIG. 27 illustrates interference in an example scenario 2700 with simultaneous UL and DL traffic, which can be used in any combination with other embodiments described herein. As shown in FIG. 27, traffic between AP1 2714a and STA1 2702a is UL. Traffic between AP2 2714b and STA2 2702b is DL. AP2 2714b may interfere with AP1 2714a, and STA1 2702a may interfere with STA2 2702b. CB / CN can be used to mitigate interference, but it may be necessary to identify the AP1-AP2 channel at AP2 2714b and the STA1-STA2 channel at STA1 2702a.

[0175]

[0217] To address this, an AP / STA (also called an initiator) wishing to transmit information can transmit a mesh sounding trigger (MST) frame. The MST frame can include the participants in the mesh (e.g., association IDs or MAC addresses). The MST frame can also include the role of each STA in an upcoming simultaneous transmission. For example, in FIG. 27, STA1 2702a and AP2 2714b can be the transmitting STAs, and AP1 2714a and STA2 2702b can be the receiving STAs. The transmitting STAs may need to null to mitigate interference with undesired receiving STAs. The MST frame can include a transmission order field that can explicitly indicate the transmission order of the sounding frames. In some embodiments, such order can be implicitly indicated by the STA roles.

[0176]

[0218] Participating STAs / APs can access the medium via the CSMA protocol and transmit NDP frames. NDP frames can be transmitted consecutively in time by various STAs / APs. In some embodiments, STAs can access simultaneously via orthogonal channel estimation fields. Non-transmitting STAs / APs can use the received NDP to estimate the channel between themselves and the transmitting STA. Furthermore, non-transmitting STAs / APs can configure their MIMO precoding vectors to minimize interference while ensuring beamforming to the desired AP / STA.

[0177]

[0219] The initiator AP / STA can then transmit a mesh data trigger (MDT) frame. The MDT frame may include the participant STAs (e.g., their association IDs) that may participate in data transmission in the next frame and the duration of the data transmission. The MDT frame may include each STA's role in the next simultaneous transmission. For example, in FIG. 27, STA1 2702a and AP2 2714b may be the transmitting STAs, and AP1 2714a and STA2 2702b may be the receiving STAs. The transmitting STAs may need to null to reduce interference to undesired receiving STAs. Participant STAs can receive the MDT. If their AID is indicated, the participant STA may be allowed to transmit data in the PPDU. The initiator AP / STA and the STAs indicated in the MDT can transmit data simultaneously. To minimize interference, the OFDM symbols in the PPDU may be aligned in time.

[0178]

[0220] Figure 28 shows an example 2800 of using MDT and MST frames for CB / CN, which can be used in any combination with the other embodiments described herein. In the example shown in Figure 28, AP2 2814b is the initiator and can transmit an MST frame 2805. AP1 2814a, STA1 2802a, and STA2 2802b receive the MST frame 2805 and can sequentially transmit sounding signals 2810, 2815, 2820, 2825 (e.g., NDP or PPDU) with information about TX signal power. AP2 2814b can also transmit a sounding signal 2815. During the sounding signals 2810, 2815, 2820, 2825, all receiving STAs (e.g., STA1 2802a and STA2 2802b) and APs (e.g., AP1 2814a) can estimate the channel and adjust their beamforming vectors. AP2 2814b can transmit an MDT trigger frame 2830, which can enable STA1 2802a to transmit. STA1 2802a and AP2 2814b can transmit their data via synchronous PPDUs. Having adjusted their beamforming vectors (CB / CN), STA1 2802a and AP2 2814b can mitigate interference to AP1 2814a and STA2 2802b, respectively.

[0179]

[0221] 29 illustrates an example 2900 of uplink-uplink CB / CN using unidirectional spatial reuse parameter (SRP)-based spatial reuse (SR), which can be used in any combination with other embodiments described herein. SR STAs receiving SRP information can incorporate precoders into their SR transmissions to lower overall interference and transmit in unidirectional SR. For example, as shown in FIG. 29, unidirectional SR can mean that STA1 2902a transmits normally while STA2 2902b performs CB / CN to limit interference to AP1 2914a during transmission.

[0180]

[0222] The STA can incorporate the beamformer gain / null in the SRP interference estimate. The maximum interference estimate in IEEE 802.11ax assumes an omnidirectional antenna with 0 db gain. The STA can then compensate for the precoder nulling effect in its estimate of the interference reaching an unwanted AP, such as AP1. The SRP input can then be SRP_INPUT = TXPWRAP - SCMA_gain + Acceptable Receiver Interference LevelAP - (AP2), where SCMA_gain can be estimated by the WTRU using SCA gain estimation types 1 and 2.

[0181]

[0223] FIG. 30 illustrates an example 3000 of Type 1 sparse code multiple access (SCMA) gain estimation, which can be used in any combination with other embodiments described herein. AP1 3014a transmits an announcement 3005 that it has a CB / CN gain estimation and can indicate the STAs 3002a, 3002b to be tested and the APs 3014a, 3014b to be tested with. As shown in FIG. 30, each STA 3002a, 3002b can transmit an SCMA packet using an omnidirectional antenna 3010, 3020 and a precoder antenna 3015, 3025 obtained by estimating a CB / CN precoder. The STAs 3002a, 3002b can then receive a trigger frame 3030 indicating that gain feedback 3035 will be transmitted. The gain feedback 3035 can be the RSSI difference between the received power of frames transmitted using the two antennas. The gain feedback 3035 can be the RSSI received for each antenna. In this case, the STAs 3002a and 3002b can estimate the gain of SCMA. The STAs 3002a and 3002b can receive (or estimate) the gain of SCMA from feedback.

[0182]

[0224] FIG. 31 shows an example 3100 of SCMA gain estimation type 2, which can be used in any combination with other embodiments described herein. As shown in FIG. 31, AP1 3114a may transmit an announcement 3105 that it has a CB / CN gain estimation and indicate the STAs 3102a, 3102b to be tested and the APs 3114a, 3114b to be tested with. As shown in FIG. 31, the STAs 3102a, 3102b may all transmit using omnidirectional antennas 3110, 3115 and switch to directional precoders 3120, 3125 to limit the need for rapid antenna beam switching. The STAs 3102a, 3102b may then receive a trigger frame 3130 indicating that gain feedback 3135 will be transmitted. The gain feedback 3135 may be the RSSI difference between the received power of frames transmitted using the two antennas. The gain feedback 3135 may be the RSSI received per antenna. In this case, the STAs 3102a and 3102b can estimate the gain of SCMA. The STAs 3102a and 3102b can receive (or estimate) the gain of SCMA from feedback.

[0183]

[0225] Figure 32 shows an example 3200 of uplink-uplink bidirectional SRP-based SR, which can be used in any combination with other embodiments described herein. In the example shown in Figure 32, because the undesired receiver (e.g., AP2 3214b) is known, the SRP trigger from AP1 3214a may include information about the candidate cooperating AP (e.g., AP2 3214b) in the trigger frame to STA1 3202a, allowing STA1 3202a to design a precoder to limit its own interference to the candidate cooperating AP's transmissions. This may enable bidirectional UL / UL CB / CN.

[0184]

[0226] Figure 33 illustrates an example 3300 of unidirectional DL / UL CB / CN with primary UL / DL transmission, which can be used in any combination with other embodiments described herein. In the example illustrated in Figure 33, if the UL transmission from STA1 3302a to AP1 3314a is the primary transmission, the secondary AP (i.e., AP2 3314b) can choose to transmit to its own STA (i.e., STA2 3302b) while limiting interference to AP1 3314a. In this case, it may be necessary for the secondary AP (i.e., AP2 3314b) to request information feedback from the primary AP (i.e., AP1 3314a), as described above. The secondary STA (i.e., STA2 3302b) can also send an ACK to AP2 3302b to confirm that it can receive the information even with interference from STA1 3302a. The ACK can be transmitted to AP2 3314b using a precoder that limits interference to AP1 3314a.

[0185]

[0227] Embodiments are described herein for cooperative beamforming for DL / DL or DL / UL architectures. In DL / DL CB / CN, if the interference inflicted on the victim is known, one of several different methods can be used.

[0186]

[0228] In one embodiment, the AP may send a CB / CN trigger to indicate that the STA should send its interference level. The target STA may respond with its acceptable interference level. The target STA may send its acceptable interference level on a 20 MHz channel. Alternatively or additionally, the target STA may send its interference level using per-RU granularity. The AP may then send a downlink transmission. Including the interference level may be optional. Including the interference level may allow listening STAs to estimate their relative interference level to the AP. Neighboring APs can use information about the identified STAs to set their precoders and transmit powers based on the acceptable interference level. This may be unidirectional, as AP1 may not adjust its transmit precoder to accommodate AP2's receiving STAs. In a bidirectional example, the AP may send information to STA1 using a precoder that limits interference to BSS2 (e.g., using a wide-angle null space). Alternatively or additionally, APs may exchange information about desired STAs before initiating transmission.

[0187]

[0229] In another embodiment, instead of requesting the instantaneous interference level of one STA at a time, the AP can send a request for the interference levels of a set of STAs in the BSS. The AP can send a CB / CN trigger frame to indicate that a set of STAs (e.g., all STAs) must send their desired interference levels. The AP can coordinate with neighboring APs to have a quiet period during this session. The target STA can respond with its acceptable interference level. The target STA can send its acceptable interference level on a 20 MHz channel. Alternatively or additionally, the target STA can send its interference level using per-RU granularity. The AP can then send a downlink transmission. Including the interference level may be optional. Including the interference level may allow listening STAs to estimate the interference level relative to the AP. Neighboring APs can use information about the identified STAs to configure their precoders and transmit powers based on the acceptable interference level.

[0188]

[0230] In another embodiment, if UL / DL is secondary but DL / UL is primary, AP1 can transmit to STAs in its BSS (e.g., STA1) while limiting interference to AP2. All STAs in BSS1 can send their interference levels. STAs in BSS2 can contend and transmit information to AP1. As mentioned above, the transmitter may need to acquire a channel to each STA.

[0189]

[0231] Embodiments relating to an interferometric alignment (IA) procedure are described herein.

[0190]

[0232] FIG. 34 illustrates an example 3400 of multi-master triggering, which may be used in combination with any of the other embodiments described herein. As shown in FIG. 34, AP1 3414a may transmit an IA trigger frame (IATF) for AP2 3414b to transmit using an IA scheme in its next transmission. AP2 3414b may receive the IATF 3405 and understand that it will be part of the IA transmission in its next transmission. AP2 3414b may use V2 of STA2 3402b when triggering. In one example, the IATF 3405 may indicate the interference base to be used at the STAs (e.g., STA1 3402a and STA2 3402b). AP2 3414b may calibrate its carrier frequency to compensate for potential frequency mismatches between them.

[0191]

[0233] Upon receiving the IATF 3405, AP2 3414b can transmit an ACK (i.e., IA Ready ACK frame 3410) acknowledging the IA transmission to AP1 3414a. AP2 3414b can enter a state where it waits for an ACK from STAs 3402a, 3402b for transmission. AP1 3414a can then transmit IATF 3415 for STA1 3402a and STA2 3402b. STA1 3402a and STA2 3402b can receive the IATF 3415, determine that they are the recipients, and understand that an IA transmission is occurring. STA1 3402a and STA2 3402b can determine their interference bases as V1 and V2, respectively. The information can be in the IATF 3415. STA1 3402a and STA2 3402b can then calibrate their carrier frequencies to compensate for potential frequency mismatches. AP1 3414a can enter a state where it waits for an ACK from STAs 3402a, 3402b for its next transmission.

[0192]

[0234] STA1 3402a and STA2 3402b can simultaneously transmit ACKs (i.e., IA Ready ACKs 3420, 3425) that may indicate that they are ready for IA and trigger an IA transmission. AP1 3414a and AP2 3414b may have M≧3 antennas. Therefore, these APs can decode ACKs 3420, 3425 from up to three different transmitters. AP1 3414a and AP2 3414b can use channel estimation to build an IA precoder. AP1 3414a and AP2 3414b can be triggered for IA transmission within the next PPDU.

[0193]

[0235] AP1 3414a and AP2 3414b may precode and transmit information based on an IA scheme (i.e., IA transmissions 3430, 3435). STA1 3402a and STA2 3402b may transmit ACKs (i.e., IA received ACKs 3440, 3445) to indicate receipt of the packets (i.e., IA transmissions 3430, 3435). STA1 3402a may discard interference on the subspace spanned by columns of V1 and decode the remaining portion of the subspace. STA2 3402b may discard interference on the subspace spanned by columns of V2 and decode the remaining portion of the subspace. Considering an OFDM-based system, the ACKs may be transmitted on RUs different from those used for IA transmissions.

[0194]

[0236] FIG. 35 illustrates an example 3500 of sequential triggering, which can be used in any combination with other embodiments described herein. As shown in FIG. 35, AP1 3514a transmits an IA trigger frame (IATF) 3505 for AP2 3514b to transmit using an IA scheme in its next transmission. AP2 3514b receives the IATF 3505 and understands that it will be part of the IA transmission in its next transmission. AP2 3514b can use V2 of STA2 3502b when triggering. In another embodiment, the IATF 3505 can indicate the interference base to be used at STAs 3502a and 3502b. AP2 3514b can calibrate its carrier frequency to compensate for potential frequency mismatches between them.

[0195]

[0237] AP2 3514b can transmit an IA ACK & Trigger frame (IATF-AT) 3510 indicating an ACK to AP1 3514a and a trigger to STA1 3502a and STA2 3502b. AP1 3514a can enter a state waiting for an ACK from STA3502a, 3502b for transmission. STA1 3502a and STA2 3502b can receive the IATF-AT 3510, determine that they are the recipients, and understand that an IA transmission is occurring. STA1 3502a and STA2 3502b can determine their interference bases as V1 and V2, respectively. The information can be in the IATF-AT frame 3510. STA1 3502a and STA2 3502b can calibrate their carrier frequencies to compensate for potential frequency mismatches between them. AP2 3514b can enter a state of waiting for an ACK from STAs 3502a and 3502b for transmission after transmission.

[0196]

[0238] STA1 3502a and STA2 3502b can simultaneously transmit ACKs (i.e., IA Ready ACKs 3515, 3520) that may indicate that they are ready for IA and trigger an IA transmission. AP1 3514a and AP2 3514b can have M≧3 antennas. Therefore, these APs can decode ACKs 3515, 3520 from up to three different transmitters. AP1 3514a and AP2 3514b can use channel estimates to build an IA precoder. AP1 3514a and AP2 3514b can be triggered for IA transmission within the next PPDU.

[0197]

[0239] AP1 3514a and AP2 3514b may precode and transmit information based on an IA scheme (i.e., IA transmissions 3525, 3530). STA1 3502a and STA2 3502b may transmit ACKs (i.e., IA received ACKs 3535, 3540) to indicate receipt of the packets (i.e., IA transmissions 3525, 3530). STA1 3502a may discard interference on the subspace spanned by columns of V1 and decode the remaining portion of the subspace. STA2 3502b may discard interference on the subspace spanned by columns of V2 and decode the remaining portion of the subspace. Considering an OFDM-based system, the ACKs may be transmitted on RUs different from those used for IA transmissions.

[0198]

[0240] FIG. 36 illustrates an example 3600 of presounding-based master triggering, which can be used in any combination with other embodiments described herein. As shown in FIG. 36, AP1 3614a transmits an IA trigger frame (IATF) 3605 for AP2 3614b to transmit using the IA scheme in its next transmission, and for STA1 3602a and STA2 3602b to receive using the IA scheme. AP2 3614b, STA1 3602a, and STA2 3602b receive the IATF 3605 and can understand that an IA transmission will occur. AP2 3614b can determine that it will be part of the IA transmission in its next transmission. AP2 3614b can use STA2 3602b's V2 when triggering. In one example, the IATF 3605 can indicate the interference base to be used in STA3 3602a and STA3 3602b. STA1 3602a and STA2 3602b can determine that they are the receivers. STA1 3602a and STA2 3602b can determine their interference bases as V1 and V2, respectively. AP2 3614b, STA1 3602a, and STA2 3602b can calibrate their carrier frequencies to compensate for potential frequency mismatches between them.

[0199]

[0241] AP2 3614b, STA1 3602a, and STA2 3602b can simultaneously transmit ACK frames (i.e., IA Ready ACKs 3610, 3615, 3620) that may indicate that IA is ready and trigger an IA transmission. AP1 3614a may have M≧3 antennas. Thus, AP1 3614a can decode ACKs (i.e., IA Ready ACKs 3610, 3615, 3620) from three different transmitters, such as AP2 3614b, STA1 3602a, and STA2 3602b. AP1 3614a and AP2 3614b can precode and transmit information based on an IA scheme (i.e., IA transmissions 3625, 3630). STA1 3602a and STA2 3602b can transmit ACKs (i.e., IA Received ACKs 3635, 3640) to indicate receipt of the packets (i.e., IA transmissions 3625, 3630). STA1 3602a can discard interference on the subspace spanned by columns of V1 and decode the remaining part of the subspace. STA2 3602b can discard interference on the subspace spanned by columns of V2 and decode the remaining part of the subspace. Considering an OFDM-based system, the ACKs can be transmitted on RUs different from those used for IA transmissions.

[0200]

[0242] An embodiment for precoding a channel estimation field for interference alignment (IA) is described herein. In the embodiment, the transmitted signals from AP1 and AP2 and the received signals at STA1 and STA2 are expressed in matrix form as

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[0201]

[0243] At the end of the third transmission, the information transmitted in AP1, AP2, STA1, and STA2, where each column relates to a different transmission instant (a1(i) is the i-th transmission instant), is:

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[0202]

[0244]

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[0203]

[0245] At the end of the fourth transmission, the expanded matrices at AP1, AP2, STA1, and STA2, where each column is associated with a transmission index, are:

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[0204]

[0246] The first transmission, the second transmission, and the fourth transmission may result in STA1's estimation of an orthogonal matrix, thereby improving the channel estimation quality at STA1.

[0205]

[0247] Figure 37 shows an example of an LTF structure 3700 for AP1 and AP2 for IA, which can be used in combination with any of the other embodiments described herein. In the example shown in Figure 37, s i is an element of the long training field (LTF) sequence (e.g., IEEE 802.11 legacy LTF),

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[0206]

[0248] In another example, AP1 and AP2 may share rows of the generalized orthogonal expanded matrix. For example, if the matrix of the generalized expanded matrix P is

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[0207]

[0249]

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[0208]

[0250] An embodiment of implicit sounding with enhanced power is described herein. The AP may be capable of transmitting at a higher power than the STA. In explicit sounding, the AP may transmit sounding packets at a relatively higher power compared to the STA. The STA may perform channel estimation, then quantize the channel information, and send it back to the AP. In implicit sounding, the STA may be capable of transmitting sounding packets at a relatively lower power compared to the AP, and the AP may perform channel estimation. Due to the difference in transmit power, channel estimation based on DL sounding frames may be more accurate than channel estimation based on UL sounding frames. Embodiments that can compensate for the difference in transmit power between the AP and the STA are described below.

[0209]

[0251] To summarize, when a device (AP or STA) transmitting an NDP in implicit channel acquisition is power-limited, the device can autonomously modify its NDP transmission to improve channel estimation, or can receive signaling from the receiver to modify its NDP transmission to improve channel estimation. The device can improve its channel estimation by one or more of the following methods: limiting the bandwidth of the NDP (e.g., RU), boosting the power it transmits within the limited bandwidth, and changing the duration of sounding (e.g., transmitting multiple repetitions of the NDP signal to increase the number of pilots / reference signals from which the channel is estimated).

[0210]

[0252] For UL sounding, in some embodiments, one or more STAs may transmit the UL sounding sequence within a narrower band (e.g., on a subset of subcarriers), which may increase the power density on each subcarrier while keeping the total transmit power the same. This may be subject to total power or power spectral density constraints. In some embodiments, one or more STAs may transmit the UL sounding sequence at a standard transmit power and power density. However, the UL sounding sequence may be repeated several times in the time domain, allowing one or more APs to receive the sounding sequence with a better SNR. Repetition of the sounding sequence may also be combined with varying the power spectral density of the transmitted signal.

[0211]

[0253] Figure 38 shows an example of a multi-AP implicit sounding procedure 3800 involving a sounding frame, which may be used in any combination with the other embodiments described herein. As shown in Figure 38, AP1 3814a may transmit a sounding trigger frame 3805 to STAs 3802a and 3802b. Upon receiving the sounding trigger frame 3805, the STAs 3802a and 3802b may transmit sounding frames 3810 and 3815 to APs 3814a and 3814b. In the example shown in Figure 38, the sounding frames 3810 and 3815 may carry wideband legacy preamble portions 3810a and 3815a and RU-based LTF portions 3810b and 3815b. The wideband preamble portion 3810a, 3815a may carry the L-STF, L-LTF, and L-SIG fields, as well as additional SIG fields transmitted using legacy numerology. This wideband preamble portion 3810a, 3815a may be transmitted normally using controlled power or maximum power. In the RU-based LTF portion 3810b, 3815b, an RU can be considered the basic transmission unit. A STA can transmit one or more RUs for an LTF transmission. Upon receiving the sounding frame 3810, 3815, the AP 3814a, 3814b can transmit an ACK frame 3820, 3825 to the STA 3802a, 3802b.

[0212]

[0254] In some embodiments, a STA can transmit one or more RUs in one OFDM symbol. The RUs can be clustered (e.g., adjacent to each other) or distributed. In some embodiments, the STA can reserve as much power as possible for the RUs. The STA can transmit more OFDM symbols for channel sounding. In some embodiments, the STA can transmit on the same set of RUs for all OFDM symbols.

[0213]

[0255] In one example, as shown in FIG. 38, STAs 3802a and 3802b may transmit on different sets of RUs for every OFDM symbol (e.g., as shown in FIG. 38, STAs 3802a and 3802b may transmit on the same number of RUs but with staggered RU locations). The allocation of RUs for each STA to transmit its sounding sequence may be indicated in the sounding trigger frame. The number of OFDM symbols for carrying the sounding sequence may be indicated in the sounding trigger frame. In some embodiments, a STA transmitting an NDP may transmit multiple NDP frames, with each frame on a different frequency resource or RU, using the power and duration necessary to ensure adequate channel estimation quality on each resource. In some embodiments, an AP may signal specific RUs and the order in which they should be transmitted. In one example, the AP may signal a starting and ending RU, and the STA transmitting the NDP may transmit the RUs in a predetermined order (e.g., consecutively) until the entire bandwidth is covered.

[0214]

[0256] When multiple STAs may transmit simultaneous UL sounding frames, the STAs may be distinguished by a P matrix or in the frequency domain. In some embodiments, the AP may signal multiple STAs to transmit their NDPs that span their desired sounding BW and are rotated so that all STAs transmit on orthogonal resources.

[0215]

[0257] The AP may need to be calibrated to perform implicit channel sounding. In some embodiments, the AP may self-calibrate, so that the AP does not require non-AP STAs to estimate the channel and send back CSI.

[0216]

[0258] FIG. 39 illustrates an example of a procedure 3900 for self-calibration that can be used in any combination with other embodiments described herein. Self-calibration can allow a non-AP STA (e.g., STA 3902) to know the duration of the self-calibration procedure so that the STA can set its NAV accordingly. In the example shown in FIG. 39, AP1 3914 can transmit a CTS-2-Self frame 3905 or other type of control / management frame with a duration field set to cover the time used for self-calibration. Alternatively or additionally, AP1 3914 can transmit self-calibration frames 3910, 3915 to multiple users (e.g., STA 3902) as part of an aggregate frame, with the self-calibration subframe addressed to itself. For example, AP1 3914 can transmit self-calibration frames 3910, 3915 to STA 3902 while STA 3902 is within its NAV 3920.

[0217]

[0259] An AP may transmit one or more self-calibration frames. In some embodiments, the self-calibration frames may be vendor-defined and may not need to be understood by other STAs in the system. In some embodiments, the self-calibration frames may use a Wi-Fi PPDU format so other STAs know they are Wi-Fi frames. At the end of calibration, the AP may transmit a TXOP done frame to signal the completion of self-calibration. As shown in FIG. 39, a non-AP STA (e.g., STA 3902) may see the CTS-2-self frame 3905 and set its NAV 3920 accordingly. If the AP is the serving AP for the STA, the STA may also enter a power save mode.

[0218]

[0260] Although the features and elements herein have been described with respect to protocols specific to IEEE 802.11, it can be appreciated that the solutions described herein are not limited to this scenario and are applicable to other wireless systems as well.

[0219]

[0261] Furthermore, while features and elements have been described above in particular combinations, those skilled in the art will understand that each feature and element can be used alone or in any combination with the other features and elements. Additionally, the methods described herein can be implemented by a computer program, software, or firmware embodied in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random-access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor in conjunction with software can be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method for a first access point (AP1), Sending a coordination request frame to a second AP (AP2) to coordinate the beamforming sounding of one or more stations (STAs), To receive a cooperative acknowledgment frame from AP2 that permits the cooperative request frame, Send a null data packet notification (NDPA) including the AP ID of AP2 to AP2. Sending a first sounding null data packet (NDP) to one or more STAs, and Receiving channel feedback from one or more STAs based on measurements of the first sounding NDP transmitted by AP1 and the second sounding NDP transmitted by AP2. Methods that include...

2. The method according to claim 1, wherein transmitting the first sounding NDP is orthogonal in time, frequency, or sequence to transmitting the second sounding NDP to the AP2.

3. The method according to claim 2, wherein the first sounding NDP and the second sounding NDP have a short interframe space (SIFS) between the first sounding NDP and the second sounding NDP and are transmitted orthogonally in time.

4. The method according to claim 2, wherein the first sounding NDP and the second sounding NDP are transmitted simultaneously.

5. The method according to claim 1, wherein the NDPA is also transmitted to the one or more STAs associated with the AP1, as indicated by the association identifier (AID) within the NDPA.

6. The method according to claim 1, wherein the channel feedback is received by the AP1 which polls each of the one or more STAs.

7. The first access point (AP1), Processor and A transceiver that communicates with the aforementioned processor and The processor and the transceiver include, A coordination request frame is sent to a second AP (AP2) to coordinate the beamforming sounding of one or more stations (STAs). The AP2 receives a cooperative acknowledgment frame that authorizes the cooperative request frame. A null data packet notification (NDPA) including the AP ID of AP2 is sent to AP2. A first sounding null data packet (NDP) is transmitted to one or more STAs. Channel feedback based on measurements of the first sounding NDP transmitted by AP1 and the second sounding NDP transmitted by AP2 is received from one or more STAs. AP1 is configured as follows.

8. The AP1 according to claim 7, wherein the transmission of the first sounding NDP is orthogonal in time, frequency, or sequence to the transmission of the second sounding NDP by the AP2.

9. AP1 according to claim 8, wherein the first sounding NDP and the second sounding NDP have a short interframe space (SIFS) between the first sounding NDP and the second sounding NDP and are transmitted orthogonally in time.

10. The AP1 according to claim 8, wherein the first sounding NDP and the second sounding NDP are transmitted simultaneously.

11. The AP1 according to claim 7, wherein the NDPA is also transmitted to the one or more STAs associated with the AP1, as indicated by the association identifier (AID) within the NDPA.

12. The AP1 according to claim 7, wherein the channel feedback is received by the AP1 which polls each of the one or more STAs.

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