Extended Channel Sounding Protocol for Wireless Local Area Network Systems

Abstract

A method and apparatus for multi-AP channel sounding for a wireless area network (WLAN) is disclosed. The method performed by the beamformee may process receiving a null data pack (NDP) announcement frame (NDPA) from the beamformer, receiving an NDP frame from the beamformer, receiving an enhanced beamforming request poll (BFRP) trigger frame from the beamformer including an indication of a feedback format, and transmitting a feedback frame including a feedback report to the beamformer based on the NDP and NDPA using a format indicated by the feedback format of the BFRP trigger frame. The trigger frame may be an enhanced beamforming report poll (BFRP) trigger frame. The feedback report may be a beamforming report or a vector index (VI) feedback report. The beamformer may be an access point (AP), while the beamformee may be a station (STA).

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims the interests of U.S. Provisional Patent Application No. 63 / 212,329, filed on 18 June 2021, and U.S. Provisional Patent Application No. 63 / 252,854, filed on 6 October 2021, the contents of which are incorporated herein by reference. [Overview of the Initiative]

[0002] A method and apparatus for multi-access point (MAP or multi-AP) channel sounding for a wireless area network (WLAN) is disclosed. The method performed by the beamformer may process: receiving a null data packed (NDP) announcement (NDPA) frame from the beamformer; receiving an NDP frame from the beamformer; receiving an Extended Beamforming Request Pole (BFRP) trigger frame from the beamformer, including an indication of a feedback format; and sending a feedback frame to the beamformer, including a feedback report based on the NDP and NDPA, using the format indicated by the feedback format of the BFRP trigger frame. The trigger frame may be an Extended Beamforming Request Pole (BFRP) trigger frame. The feedback report may be a beamforming report or a vector index (VI) feedback report. The beamformer may be an access point (AP), and the beamformer may be a station (STA).

[0003] The beamformer may process the following: sending a null data pack (NDP) announcement frame (NDPA); sending an NDP frame; sending a first Extended Beamforming Request Pole (BFRP) trigger frame including a feedback format indication; receiving one or more beamforming reports from a first set of beamformers based on the feedback format indication; sending a second Extended Beamforming Request Pole (BFRP) trigger frame including a feedback format indication; and receiving one or more feedback reports from a second set of beamformers based on the feedback format indication. The feedback reports may be VI feedback reports. The beamformer may be an access point (AP), and the beamformer may be a station (STA). [Brief explanation of the drawing]

[0004] A more detailed understanding can be obtained from the following explanation, which is given as an example in conjunction with the attached drawings, where similar reference numbers in the drawings refer to similar elements. [Figure 1A] This is a system diagram showing an exemplary communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] This is a system diagram showing an exemplary wireless transmit / receive unit (WTRU) that may be used in the communication system shown in Figure 1A, according to one embodiment. [Figure 1C] This is a system diagram showing an exemplary radio access network (RAN) and an exemplary core network (CN) that may be used in the communication system shown in Figure 1A according to one embodiment. [Figure 1D]This is a system diagram showing further exemplary RAN and further exemplary CN that may be used in the communication system shown in Figure 1A according to one embodiment. [Figure 2] This figure shows examples of sequential channel sounding procedures and joint channel sounding procedures performed in a multi-AP system. [Figure 3] This figure shows an example of a High Efficiency (HE) Null Data Packet (NDP) packet announcement frame format. [Figure 4] This figure shows an example of the STA information field format in an EHT NDP announcement frame. [Figure 5] This figure shows an example of a trigger frame format. [Figure 6] This figure shows an example of an Extremely High Throughput (EHT) variant user information field format. [Figure 7] This figure shows an example of the EHT special user information field format. [Figure 8] An example of a VI sounding protocol using only C2 STA is shown. [Figure 9] This figure shows an example of a group-based VI feedback sounding protocol. [Figure 10] This figure shows an example of a VI sounding protocol using mixed classes of STA (C1 STA and C2 STA). [Figure 11] This figure shows an example of a beamformed NDP sounding protocol using only the C2 STA. [Figure 12] This figure shows another example of a beamformed NDP sounding protocol using only the C2 STA. [Figure 13] This figure shows an example of a beamformed NDP sounding protocol using C1 STA and C2 STA. [Figure 14] This figure shows an example of a multi-AP sounding protocol using index feedback. [Figure 15] This figure shows an example of a beamformed single multi-AP sounding procedure. [Figure 16] This figure shows an example of a beamformed single NDP structure for multi-AP sounding. [Figure 17] This figure shows an example of a single beamformed NDP packet structure using interleaved AP transmissions of EHT-LTF. [Figure 18] This figure shows an example of a single beamformed NDP packet structure using interleaved beam transmission of EHT-LTF. [Figure 19] This figure shows an example of a single beamformed NDP packet structure using interleaved APs and beam transmissions of EHT-LTF. [Modes for carrying out the invention]

[0005] Figure 1A illustrates an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, message transmission, and broadcast to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through the sharing of 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-tail unique-word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filter OFDM, and filter bank multicarrier (FBMC).

[0006] As shown in Figure 1A, the communication system 100 may include radio transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the internet 110, and other networks 112, but it will be understood that the disclosed embodiments intend any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, and 102d may be any type of device configured to operate and / or communicate in a radio environment. For example, WTRU102a, 102b, 102c, and 102d, all of which may be referred to as stations (STAs), may be configured to transmit and / or receive radio signals, but may include user equipment (UEs), mobile stations, fixed or mobile subscriber units, subscriber-based units, pagers, mobile phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearables, 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 an industrial and / or automated processing chain context), consumer electronic devices, and devices operating on commercial and / or industrial wireless networks. Any of WTRU102a, 102b, 102c, and 102d may interchangeably be referred to as a UE.

[0007] The communication system 100 may also include base stations 114a and / or base stations 114b. Each of the base stations 114a and 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, and 102d to facilitate access to one or more communication networks such as CN 106, the Internet 110, and / or other networks 112. As an example, base stations 114a and 114b may be next-generation node B such as base transceiver station (BTS), node B, e-node B (eNB), Home node B, Home e-node B, g-node B (gNB), new radio (NR) node B, site controller, access point (AP), wireless router, etc. Although base stations 114a and 114b are each depicted as single elements, it will be understood that base stations 114a and 114b may include any number of interconnected base stations and / or network elements.

[0008] Base station 114a may be part of RAN104, which may also include other base stations such as a base station controller (BSC), a radio network controller (RNC), a relay node, and / or network elements (not shown). Base station 114a and / or base station 114b may be configured to transmit and / or receive radio signals at one or more carrier frequencies that may be referred to as a cell (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage to a specific geographic area that may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver per sector of the cell. In one embodiment, base station 114a may use multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers per sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0009] Base stations 114a, 114b may communicate with one or more of WTRUs 102a, 102b, 102c, 102d via 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.). Air interface 116 may be established using any suitable radio access technology (RAT).

[0010] More specifically, as described above, the communication system 100 can be a multiple access system and can use one or more channel access methods, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a of RAN104 and WTRU102a, 102b, 102c can establish the air interface 116 using wideband CDMA (WCDMA), and can implement radio technologies such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA). WCDMA can include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed Downlink Packet Access (HSDPA) and / or High-Speed Uplink Packet Access (HSUPA).

[0011] In one embodiment, the base station 114a and WTRU102a, 102b, 102c can implement radio technologies such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which can establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0012] In one embodiment, the base station 114a and WTRU102a, 102b, 102c can implement radio technologies such as NR radio access, which can establish the air interface 116 using NR.

[0013] In one embodiment, base station 114a and WTRU 102a, 102b, 102c may implement multiple radio access technologies. For example, base station 114a and WTRU 102a, 102b, 102c may implement LTE radio access and NR radio access together, for example, using the dual connectivity (DC) principle. Thus, the air interface utilized by WTRU 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions to and / or from multiple types of base stations (e.g., eNB and gNB).

[0014] In other embodiments, base stations 114a and WTRUs 102a, 102b, and 102c may implement wireless technologies such as IEEE 802.11 (i.e., Wireless Fidelity, WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access, WiMAX), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Provisional Standard 2000 (IS-2000), Provisional Standard 95 (IS-95), Provisional Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0015] The base station 114b in Figure 1A may be, for example, a wireless router, Home node B, Home e node B, or access point, but any suitable RAT may be used to facilitate wireless connectivity in local areas such as offices, homes, vehicles, campuses, industrial facilities, aerial corridors (for use by drones), roads, etc. In one embodiment, the base station 114b and WTRU 102c, 102d may implement wireless technologies such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and WTRU 102c, 102d may implement wireless technologies such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, base stations 114b and WTRUs 102c, 102d may establish picocells or femtocells using cellular-based RATs (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.). As shown in Figure 1A, base station 114b may have a direct connection to the internet 110. Therefore, base station 114b may not need to access the internet 110 via CN 106.

[0016] RAN104 may communicate with CN106, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of WTRU102a, 102b, 102c, and 102d. The data may have various quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, and mobility requirements. CN106 may provide call control, billing services, mobile location-based services, prepaid calls, internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in Figure 1A, it will be understood that RAN104 and / or CN106 may communicate directly or indirectly with other RANs using the same RAT or a different RAT as RAN104. For example, in addition to being connected to RAN104 which may utilize NR radio technology, CN106 may also communicate with another RAN (not shown) using GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0017] CN106 may also function as a gateway for WTRU102a, 102b, 102c, and 102d to access PSTN108, the Internet 110, and / or other networks 112. PSTN108 may include a circuit-switched telephone network providing Plain Old Telephone Service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices, which use common communication protocols such as the transmission control protocol (TCP), the user datagram protocol (UDP), and / or the Internet protocol (IP) of the TCP / IP Internet Protocol suite. Network 112 may include wired and / or wireless networks owned and / or operated by other service providers. For example, network 112 may include another CN connected to one or more RANs that may use the same RAT as RAN104 or a different RAT.

[0018] Some or all of the WTRUs 102a, 102b, 102c, and 102d in the communication system 100 may include multimode capability (for example, WTRUs 102a, 102b, 102c, and 102d may include multiple transceivers for communicating with different radio networks via different radio links). For example, WTRU 102c shown in Figure 1A may be configured to communicate with base station 114a, which may use cellular-based radio technology, and base station 114b, which may use IEEE 802 radio technology.

[0019] Figure 1B is a system diagram illustrating an exemplary WTRU 102. As shown in Figure 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 supply 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be understood that the WTRU 102 may include any partial combination of the aforementioned elements while maintaining consistency with one embodiment.

[0020] The processor 118 may be a general-purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to a transceiver 120 which can be coupled to a transmit / receive element 122. Figure 1B depicts the processor 118 and transceiver 120 as separate components, but it will be understood that the processor 118 and transceiver 120 can be integrated together in an electronic package or chip.

[0021] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via 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, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF signals and optical signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of radio signals.

[0022] Although the transmit / receive element 122 is depicted as a single element in Figure 1B, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may utilize 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 radio signals via the air interface 116.

[0023] The transceiver 120 may be configured to modulate the signal transmitted by the transmit / receive element 122 and demodulate the signal received by the transmit / receive element 122. As described above, the WTRU 102 may have multimode capability. Therefore, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0024] The processor 118 of the WTRU102 may be coupled to 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) and may receive user input from these. The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from any type of suitable memory, such as non-removable memory 130 and / or removable memory 132, and store data in such memory. 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, and the like. In other embodiments, the processor 118 may access information from memory not physically located on the WTRU 102, such as on a server or home computer (not shown), and store data in such memory.

[0025] The processor 118 may receive power from the power supply 134, but may be configured to distribute and / or control power to other components in the WTRU 102. The power supply 134 may be any suitable device for supplying power to the WTRU 102. For example, the power supply 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0026] 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) about the current location of the WTRU 102. In addition to or instead of the information from the GPS chipset 136, the WTRU 102 may receive location information from base stations (e.g., base stations 114a, 114b) via the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be understood that the WTRU 102 may acquire location information by any preferred location determination method while maintaining consistency with one embodiment.

[0027] The processor 118 may be further coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functions, and / or wired or wireless connectivity. For example, peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth® module, a frequency modulated (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, and the like. Peripherals 138 may include one or more sensors. The sensor may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor, geolocation sensor, altimeter, light sensor, touch sensor, barometer, gesture sensor, biometric sensor, humidity sensor, etc.

[0028] WTRU102 may include a full-duplex radio in which the transmission and reception of some or all of a signal (for example, associated with specific subframes of both UL (for example, for transmission) and DL (for example, for reception) may be simultaneous and / or together. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference either through hardware (e.g., chokes) or signal processing via a processor (e.g., via a separate processor (not shown) or processor 118). In one embodiment, WTRU102 may include a half-duplex radio for the transmission and reception of some or all of a signal (for example, associated with specific subframes of either UL (for example, for transmission) or DL ​​(for example, for reception)).

[0029] Figure 1C is a system diagram illustrating RAN104 and CN106 according to one embodiment. As described above, RAN104 can communicate with WTRU102a, 102b, and 102c via the air interface 116 using E-UTRA wireless technology. RAN104 can also communicate with CN106.

[0030] RAN104 may include e-nodes-B160a, 160b, and 160c, but it will be understood that RAN104 may include any number of e-nodes-B while maintaining consistency with one embodiment. Each of e-nodes-B160a, 160b, and 160c may include one or more transceivers for communicating with WTRU102a, 102b, and 102c via the air interface 116. In one embodiment, e-nodes-B160a, 160b, and 160c may implement MIMO technology. Thus, e-node-B160a may, for example, use multiple antennas to transmit radio signals to and / or receive radio signals from WTRU102a.

[0031] Each of the e-nodes-B160a, 160b, and 160c may be associated with a specific cell (not shown) and may be configured to handle wireless resource management decisions, handover decisions, user scheduling, etc., in UL and / or DL. As shown in Figure 1C, the e-nodes-B160a, 160b, and 160c may communicate with each other via the X2 interface.

[0032] The CN106 shown in Figure 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) and a packet data gateway (PGW) 166. Although the aforementioned elements are shown as part of CN106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0033] The MME162 can be connected to each of the e-nodes B162a, 162b, and 162c in RAN104 via the S1 interface, but can also function as a control node. For example, the MME162 may perform roles such as authenticating users of WTRU102a, 102b, and 102c, activating / deactivating bearers, and selecting gateways for specific services during the initial attachment of WTRU102a, 102b, and 102c. The MME162 may provide control plane functionality for switching between RAN104 and other RANs (not shown) employing other radio technologies such as GSM and / or WCDMA.

[0034] The SGW164 can be connected to each of the e-nodes B160a, 160b, and 160c in RAN104 via the S1 interface. The SGW164 can generally route and forward user data packets to and from WTRU102a, 102b, and 102c. The SGW164 can perform other functions, such as anchoring the user plane during e-node B handovers, triggering paging when DL data is available to WTRU102a, 102b, and 102c, and managing and remembering the context of WTRU102a, 102b, and 102c.

[0035] SGW164 may be connected to PGW166, which may provide WTRU102a, 102b, and 102c with access to a packet-switched network such as the Internet 110 to facilitate communication between WTRU102a, 102b, and 102c and IP-enabled devices.

[0036] CN106 can facilitate communication with other networks. For example, CN106 can provide WTRU102a, 102b, and 102c with access to a circuit-switched network such as PSTN108 to facilitate communication between WTRU102a, 102b, and 102c and conventional terrestrial line communication devices. For example, CN106 may include, or communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that acts as an interface between CN106 and PSTN108. In addition, CN106 may provide WTRU102a, 102b, and 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0037] Although the WTRU is described as a wireless terminal in Figures 1A to 1D, in certain representative embodiments, such a terminal is intended to be able to use a wired communication interface (e.g., temporary or permanent) with a communication network.

[0038] In a typical embodiment, the other network 112 may be a WLAN.

[0039] A WLAN in Infrastructure Basic Service Set (BSS) mode may have BSS access points (APs) and one or more stations (STAs) associated with the APs. APs may have access to or interfaces with a Distribution System (DS) or another type of wired / wireless network that carries traffic within and / or outside the BSS. Traffic originating outside the BSS and destined for an STA may reach through an AP, but may also be distributed to an STA. Traffic originating from an STA to a destination outside the BSS may be sent to an AP and then to its respective destination. Traffic between STAs within the BSS may be transmitted, for example, via an AP, where the source STA sends traffic to the AP, and the AP distributes 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 transmitted between a source STA and a destination STA (for example, directly between them) in a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using Independent BSS (IBSS) mode may not have APs, and STAs within or using IBSS (e.g., all STAs) may communicate directly with each other. The IBSS mode of communication may be referred to herein as “ad hoc” communication mode.

[0040] When using the 802.11ac infrastructure operating mode or a similar operating mode, an AP may transmit beacons on a fixed channel, such as the primary channel. The primary channel may be of a fixed width (e.g., a 20 MHz bandwidth) or a dynamically set width. The primary channel may be the operating channel of the BSS, but may be used by an STA to establish a connection with the AP. In certain typical embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. In the case of CSMA / CA, an STA, including the AP (e.g., all STAs), may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, that STA may be backed off. A single STA (e.g., only one station) may transmit at any given time on a given BSS.

[0041] High-throughput (HT) STAs may use a 40 MHz wide channel for communication, which may be formed, for example, through a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels.

[0042] Very High Throughput (VHT) STAs may support channels with widths of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz. The 40 MHz and / or 80 MHz channels mentioned above may be formed by combining multiple consecutive 20 MHz channels. A 160 MHz channel may be formed by combining eight consecutive 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. In the 80+80 configuration, after channel coding, the data may pass through a segment parser that can split the data into two streams. Inverse Fast Fourier Transform (IFFT) and time-domain processing may be performed separately for each stream. The streams may be mapped to two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of a receiving STA, the operation described above for the 80+80 configuration may be reversed, and the combined data may be transmitted to Medium Access Control (MAC).

[0043] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidth and carrier are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports bandwidths of 5 MHz, 10 MHz, and 20 MHz in the TV White Space (TVWS) spectrum, while 802.11ah supports bandwidths of 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz using the non-TVWS spectrum. According to a typical embodiment, 802.11ah may support meter-type control / machine-type communications (MTC), such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, including support for specific and / or limited bandwidths (e.g., support only for that). MTC devices may include batteries with battery life exceeding a threshold (e.g., to maintain very long battery life).

[0044] A WLAN system capable of supporting multiple channels and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah includes a channel that can be 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. The bandwidth of the primary channel may be set and / or limited by an STA from among all STAs operating in a BSS that support the minimum bandwidth operating mode. In the 802.11ah example, the primary channel may be 1 MHz wide for an STA (e.g., an MTC type device) that supports (e.g., only) the 1 MHz mode, even if other STAs in the AP and 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) settings may depend on the state of the primary channel. For example, if the primary channel is busy, an STA (which only supports 1MHz operating mode) sending to the AP may consider the entire available frequency band to be busy, even if most of the available frequency band is idle.

[0045] In the United States, the available frequency band that can be used by 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0046] Figure 1D is a system diagram illustrating RAN104 and CN106 according to one embodiment. As described above, RAN104 can communicate with WTRU102a, 102b, and 102c via the air interface 116 using NR radio technology. RAN104 can also communicate with CN106.

[0047] RAN104 may include gNB180a, 180b, and 180c, but it will be understood that RAN104 may include any number of gNBs while maintaining consistency with one embodiment. Each of gNB180a, 180b, and 180c may include one or more transceivers for communicating with WTRU102a, 102b, and 102c via the air interface 116. In one embodiment, gNB180a, 180b, and 180c may implement MIMO technology. For example, gNB180a and 180b may use beamforming to transmit and / or receive signals to gNB180a, 180b, and 180c. Thus, gNB180a may, for example, use multiple antennas to transmit radio signals to and / or receive radio signals from WTRU102a. In one embodiment, gNB180a, 180b, and 180c may implement carrier aggregation technology. For example, gNB180a may transmit multiple component carriers to WTRU102a (not shown). A subset of these component carriers may be on the unauthorized spectrum, while the remaining component carriers may be on the authorized spectrum. In one embodiment, gNB180a, 180b, and 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU102a may receive coordinated transmissions from gNB180a and gNB180b (and / or gNB180c).

[0048] WTRU102a, 102b, and 102c may communicate with gNB180a, 180b, and 180c using transmissions associated with an expandable numerology. For example, OFDM symbol intervals and / or OFDM subcarrier intervals may vary for different transmissions, different cells, and / or different portions of the radio transmission spectrum. WTRU102a, 102b, and 102c may communicate with gNB180a, 180b, and 180c using subframes or transmission time intervals (TTIs) of varying or expandable lengths (e.g., varying numbers of OFDM symbols and / or varying durations of absolute time).

[0049] gNB180a, 180b, and 180c can be configured to communicate with WTRU102a, 102b, and 102c in standalone and / or non-standalone configurations. In a standalone configuration, WTRU102a, 102b, and 102c can communicate with gNB180a, 180b, and 180c without accessing other RANs (e.g., e-node-B160a, 160b, and 160c). In a standalone configuration, WTRU102a, 102b, and 102c can utilize one or more of gNB180a, 180b, and 180c as mobility anchor points. In a standalone configuration, WTRU102a, 102b, and 102c can communicate with gNB180a, 180b, and 180c using signals in unlicensed bands. In a non-standalone configuration, WTRU102a, 102b, and 102c can communicate with and connect to gNB180a, 180b, and 180c, while also communicating with and connecting to other RANs such as e-nodes-B160a, 160b, and 160c. For example, WTRU102a, 102b, and 102c can implement DC principles for substantially simultaneous communication with one or more gNB180a, 180b, and 180c and one or more e-nodes-B160a, 160b, and 160c. In a non-standalone configuration, e-nodes B160a, 160b, and 160c can function as mobility anchors for WTRU102a, 102b, and 102c, while gNB180a, 180b, and 180c can provide additional coverage and / or throughput to service WTRU102a, 102b, and 102c.

[0050] Each of the gNB180a, 180b, and 180c may be associated with a specific cell (not shown), but may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, network slice support, interaction between DC, NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a and 184b, and routing of control plane information to Access and Mobility Management Functions (AMFs) 182a and 182b. As shown in Figure 1D, the gNB180a, 180b, and 180c may communicate with each other via the Xn interface.

[0051] The CN106 shown in Figure 1D may include at least one AMF182a, 182b, at least one UPF184a, 184b, at least one Session Management Function (SMF)183a, 183b, and possibly a Data Network (DN)185a, 185b. Although the aforementioned elements are shown as part of CN106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0052] AMF182a and 182b can be connected to one or more gNB180a, 180b, and 180c in RAN104 via the N2 interface and can function as control nodes. For example, AMF182a and 182b may play roles such as user authentication for WTRU102a, 102b, and 102c, support for network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selection of specific SMF183a and 183b, management of registration areas, termination of non-access stratum (NAS) signaling, and mobility management. Network slicing can be used by AMF182a and 182b to customize CN support for WTRU102a, 102b, and 102c based on the type of service utilizing WTRU102a, 102b, and 102c. For example, different network slices may be established for different use cases, such as services that rely on ultra-reliable low latency (URLLC) access, services that rely on enhanced massive mobile broadband (eMBB) access, and services for MTC access. AMF182a, 182b may provide control plane functionality for switching between RAN104 and other RANs (not shown) using other radio technologies such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0053] SMF183a and 183b may be connected to AMF182a and 182b in CN106 via the N11 interface. SMF183a and 183b may also be connected to UPF184a and 184b in CN106 via the N4 interface. SMF183a and 183b may select and control UPF184a and 184b and configure the routing of traffic through UPF184a and 184b. SMF183a and 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing DL data notifications. PDU session types may be IP-based, non-IP-based, Ethernet-based, etc.

[0054] UPF184a and 184b may be connected via the N3 interface to one or more gNB180a, 180b, and 180c within RAN104, thereby providing WTRU102a, 102b, and 102c with access to a packet-switched network such as the Internet 110 to facilitate communication between WTRU102a, 102b, and 102c and IP-enabled devices. UPF184 and 184b may perform other functions such as packet routing and forwarding, enforcement of user plane policies, support for multi-homed PDU sessions, processing of user plane QoS, buffering of DL packets, and providing mobility anchoring.

[0055] CN106 can facilitate communication with other networks. For example, CN106 may include, or communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that functions as an interface between CN106 and PSTN108. In addition, CN106 may provide WTRU102a, 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, WTRU102a, 102b, 102c may be connected to local DN185a, 185b via UPF184a, 184b through an N3 interface to UPF184a, 184b and an N6 interface between UPF184a, 184b and local DN185a, 185b.

[0056] With regard to Figures 1A-1D and the corresponding descriptions in Figures 1A-1D, one or more of the functions described herein with respect to one or more of the WTRU102a-d, base stations 114a-b, enode-B160a-c, MME162, SGW164, PGW166, gNB180a-c, AMF182a-b, UPF184a-b, SMF183a-b, DN185a-b, and / or any other devices described herein, one or more of the functions 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 of the functions described herein. For example, an emulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0057] Emulation devices may be designed to implement testing of one or more other devices in a laboratory and / or 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 network to test other devices in a communications 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 network. Emulation devices may be directly coupled to another device for the purpose of testing and / or performing testing using over-the-air wireless communication.

[0058] One or more emulation devices may perform one or more functions, including all of the above, while not implemented / deployed as part of a wired and / or wireless communication network. For example, an emulation device may be used in a test laboratory test scenario, and / or in a wired and / or wireless communication network that is not deployed (e.g., for testing purposes), to implement testing of one or more components. One or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation device to transmit and / or receive data.

[0059] A Wireless Local Area Network (WLAN) in Infrastructure Basic Service Set (BSS) mode may include an Access Point (AP) of the BSS and one or more stations (STAs) associated with the AP. The AP may have access to or interfaces with a Distribution System (DS) or another type of wired / wireless network that carries traffic within and outside the BSS. Traffic originating outside the BSS and reaching an STA via an AP may be delivered to the STA. Traffic originating from an STA to an external destination may be sent to the AP and delivered to its respective destination. Traffic between STAs within the BSS may also be sent via the AP, but the source STA sends the traffic to the AP, and the AP delivers the traffic to the destination STA.

[0060] According to the Electronics and Electrical Engineers (IEEE) 802.11 standard for infrastructure operating modes such as 802.11ac and / or 802.11ax, an AP may transmit beacons on a fixed channel, usually the primary channel. This channel may be 20 MHz wide and may be the operating channel of the BSS. This channel may also be used by STAs to establish a connection with the AP. Basic channel access in an 802.11 system may be Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) with collision avoidance. In this operating mode, some STAs, or all STAs including the AP, may sense the primary channel. If the channel is detected as busy, the STA may "backoff". Thus, one STA may transmit at any given time in the BSS.

[0061] In embodiments operating according to the 802.11n standard, a High Throughput (HT) STA may also use a 40 MHz wide channel for communication. This can be achieved by combining a primary 20 MHz channel with an adjacent 20 MHz channel to form a continuous 40 MHz wide channel.

[0062] In embodiments operating according to the 802.11ac standard, a Very High Throughput (VHT) STA may support channels of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz width. 40 MHz and 80 MHz channels may be formed by combining consecutive 20 MHz channels, similar to the 802.11n configuration described above. A 160 MHz channel may be formed by combining eight consecutive 20 MHz channels, or by combining two non-consecutive 80 MHz channels, which may also be referred to as an 80+80 configuration. In the 80+80 configuration, after channel coding, the data may pass through a segment parser that splits the data into two streams. Inverse Discrete Fourier Transform (IDFT) operation and time-domain processing may be performed separately for each stream. The streams may then be mapped to two channels, but the data may be transmitted. At the receiver, this mechanism may be reversed, but the combined data may be transmitted to the MAC.

[0063] To improve spectral efficiency, systems operating according to the 802.11ac standard may implement, for example, the concept of downlink multi-user MIMO (MU-MIMO) transmission from an AP to multiple STAs within the same symbol time frame during a downlink OFDM symbol. The possibility of using downlink MU-MIMO may also be considered for embodiments operating according to the 802.11ah standard. It is important to note that, as used in 802.11ac, downlink MU-MIMO can use the same symbol timing for transmissions to multiple STAs, so interference between waveform transmissions to multiple STAs may not be a problem. However, all STAs involved in MU-MIMO transmission from the AP may need to use the same channel or bandwidth, which may limit the operating bandwidth to the minimum channel bandwidth supported by the STA included as a destination for MU-MIMO transmission from the AP.

[0064] The IEEE 802.11 Extremely High Throughput (EHT) study group was formed in September 2018. EHT development could provide a foundation for the next major revision of the IEEE 802.11 standard following 802.11ax. The EHT study group explores the possibility of further increasing peak throughput and improving the efficiency of IEEE 802.11 networks. Following the establishment of the EHT study group, the 802.11be task group was also established to provide the 802.11 EHT specification. Use cases and applications addressed include high-throughput and low-latency applications such as video, augmented reality (AR), and virtual reality (VR) over WLAN. To achieve the goals of increasing peak throughput and improving efficiency, the list of features discussed in the EHT SG and 802.11be includes new designs for multi-AP, multi-band / multi-link, 320MHz bandwidth, 16 spatial streams, HARQ, AP coordination, and 6GHz channel access. The IEEE Standards Committee approved the IEEE 802.11be Task Group (TG) based on the Project Authorization Request (PAR) and Criteria for Standards Development (CSD) developed by the EHT research group.

[0065] The EHT STA uses the EHT sounding protocol to determine channel state information. The EHT sounding protocol provides an explicit feedback mechanism, defined as EHT non-trigger-based (non-TB) sounding and EHT trigger-based (TB) sounding, where the EHT beamformer measures the channel using the training signal transmitted by the EHT beamformer (i.e., the EHT sounding NDP) and sends back a transformed estimate of the channel state. The EHT beamformer uses this estimate to derive the steering matrix.

[0066] EHT beamforming returns channel state estimates in EHT compressed beamforming / CQI reports carried in one or more EHT compressed beamforming / CQI frames. Three types of EHT compressed beamforming / CQI reports exist: (1) SU feedback, (2) MU feedback, and (3) CQI feedback.

[0067] In SU feedback, the EHT compression beamforming / CQI report consists of the EHT compression beamforming report field. In MU feedback, the EHT compression beamforming / CQI report consists of the EHT compression beamforming report field and the EHT MU exclusive beamforming report field. In CQI feedback, the EHT compression beamforming / CQI report consists of the EHT CQI report field.

[0068] Coordinated multi-AP (C-MAP) transmission may be supported in 802.11be. The methods described so far include (1) coordinated multi-AP OFDMA, (2) coordinated multi-AP TDMA, (3) coordinated multi-AP space reuse, (4) coordinated beamforming / nulling, and (5) joint transmission.

[0069] In the context of cooperative multi-AP, several terms are defined, including (1) shared AP, (2) shared AP, and (3) AP candidate set. In a shared AP, an EHT AP acquires a TXOP and initiates multi-AP coordination. In a shared AP, an EHT AP is coordinated by the shared AP for multi-AP transmission. In an AP candidate set, a set of APs can initiate or participate in multi-AP coordination.

[0070] The 802.11be standard may support a mechanism for determining whether an AP is part of a set of candidate APs and can participate as a shared AP in a coordinated multi-AP transmission initiated by a shared AP. The procedure may need to be defined for an AP to share its frequency / time resources for an acquired TXOP with a set of APs. An AP intending to use resources (i.e., frequency or time) shared by another AP may be able to indicate its need for those resources to the AP sharing them. Coordinated OFDMA may be supported in 11be, but in coordinated OFDMA, both DL OFDMA and its corresponding UL OFDMA acknowledgments may be permitted.

[0071] Further details regarding multi-AP channel sounding under the 802.11be standard are described herein. Channel sounding under the 802.11n and 802.11ac standards can be performed using two different methods, generally referred to as explicit channel sounding and implicit channel sounding. In explicit channel sounding, the AP may send an NDP to the STA, along with a preamble that allows the STA to measure its own channel and send CSI feedback to the AP. In implicit channel sounding, the STA may send an NDP, but the AP may measure its channel assuming that the STA's channels are reciprocal.

[0072] 802.11be may support a maximum number of spatial streams for SU-MIMO and MU-MIMO (e.g., 16). The maximum number of spatial streams allocated to each MU-MIMO scheduled non-AP STA may be limited (e.g., to 4). The maximum number of users for whom DL transmissions can be spatially multiplexed may be, for example, 8 per resource block (RU).

[0073] 802.11be may support two or more modes of channel sounding in a multi-AP system. Two of these modes of channel sounding may be sequential sounding and joint sounding. In sequential sounding, each AP can transmit NDP independently without overlapping sounding periods for each AP. In other words, each AP performs sounding in its own time period, and these sounding time periods may be called sequential. In joint sounding, the AP has a total of eight or fewer antennas active on all LTF tones and uses the 802.11ax P matrix across OFDM symbols. In other words, joint sounding in a multi-AP system with eight or fewer APs can activate all antennas on all LTF tones and use the 802.11ax P matrix to transmit / receive sounding signals.

[0074] CSI feedback collection in multi-AP systems is performed using a four-step sounding sequence such as 802.11ax (Null Data Packet Announcement (NDPA) + NDP + Beamforming Report Pole (BFRP) trigger frame + CSI report) to collect feedback from both within the BSS and from overlapping BSS (OBSS) STAs. In other words, this four-step process can be used to obtain sounding feedback from STAs in BSSs operated by APs, and from STAs in overlapping BSSs that are not associated with the same AP. In sequential sounding for multi-AP systems, the STA can process NDPA frames and BFRP trigger frames received from the OBSS AP, and the STA can respond to the OBSS AP with the corresponding CSI when polled with a BFRP TF from the OBSS AP.

[0075] Figure 2 shows a signal flow diagram illustrating examples of both sequential and joint channel sounding procedures performed in a multi-AP system. To initiate either process, in one example, a shared AP (AP1 202a) transmits a multi-AP NDPA (MAP-NDPA) 206, and then each AP in the coordinating group (AP1 202a, AP2 202b, and AP3 202c) can transmit an NDPA (AP1 202a transmits NDPA 208a, AP2 202b transmits NDPA 208b, and AP3 202c transmits NDPA 208c). After the sounding procedure (either joint or sequential), AP1 202a transmits a beamforming report pole (BFRP) trigger frame. NDPAs 208a, 208b, and 208c may have the format shown in Figure 3, which will be described in more detail below. The BFRP trigger frame may have the format shown in Figure 5, which will be explained in more detail below.

[0076] In the sequential sounding scheme, each AP in a coordinating group (AP1 202a, AP2 202b, and AP3 202c) can transmit its corresponding NDP (NDP210a, NDP210b, and NDP210c) to all STAs (204a, 204b, and 204c) in the coordinating group at different non-overlapping time intervals (i.e., they can be time-multiplexed). In this scenario, each NDP / NDP / DP210a, 210b, and 210c can be separated by a short interframe space (SIFS) time interval.

[0077] In the joint sounding scheme, each cooperative AP (AP1 202a, AP2 202b, and AP3 202c) can simultaneously transmit its corresponding NDP (NDP210a, NDP210b, and NDP210c), where different Long Training Field (LTF) tones are spread across the entire bandwidth and spatially multiplexed, or use orthogonal codes. Otherwise, each AP (AP1 202a, AP2 202b, and AP3 202c) may transmit its corresponding LTF tone only on selected tones to avoid tone overlap between APs. The STAs (STA1 204a, STA2 204b, and STA3 204c) that receive the NDP frame then determine whether it is a CSI or CQI and may send that information back to one of the APs in the coordinating group (AP1 202a, AP2 202b, or AP3 202c) in feedback reports 216a, 216b, and 216c.

[0078] MAP-NDPA206 may notify all APs (AP1 202a, AP2 202b, and AP3 202c) to transmit their respective NDPAs (NDPA 1 208a, NDPA 2 208b, and NDPA 3 208c) to their associated STAs (STA 1 204a, STA 2 204b, and STA 3 204c). MAP-NDPA206 may include sounding information required by different APs. For example, sounding information may include feedback type, sounding subchannel or RU (which subchannel or RU needs to be sounded for feedback), and sounding bandwidth.

[0079] APs may send an NDPA to request channel feedback from their associated STAs. An NDPA may indicate the feedback type and grouping information, the subchannel requested for feedback, the codebook size, the requested STA address, etc. Different STAs may be requested for feedback to different subchannels.

[0080] The AP may send the NDP to the requested STA, which will analyze the training field contained within the NDP to calculate the channel response.

[0081] When an STA (such as STA1 204a, STA2 204b, or STA3 204c shown in Figure 2) receives an NDP, it measures the channel and prepares a CSI feedback report. Different methods are proposed for collecting CSI from STAs. In one method, each AP collects all CSI, including feedback from in-BSS and OBSS stations. In another method, each AP may collect CSI only from its associated STA. In yet another method, a shared AP (AP1 202a in Figure 2) can collect CSI from all shared APs within the coordinating group.

[0082] In general, the challenges of channel sounding in multi-AP environments include (1) the inability of STAs involved in sounding to hear the coordinating AP (or master AP), (2) synchronization of APs within a multi-AP coordinating set, (3) the overhead, complexity, and performance of different sounding schemes, (4) variations in NDP transmissions in explicit and implicit sounding, and (5) feedback collection and reduction.

[0083] The 802.11be Task Group (TG) has agreed to maintain a similar NDP Announcement (NDPA) structure to the 802.11ax NDPA, as shown in Figure 3. However, the STA information fields shown in Figure 4 will be modified to accommodate the new features of the EHT in 802.11be.

[0084] As described above, Figure 3 shows an exemplary High Efficiency (HE) NDPA frame format. Those skilled in the art will recognize and understand this 802.11ax NDPA frame format and the purpose / interpretation of the subfields included in the frame. The HE NDPA frame 300 may include a frame control field 302, a duration field 304, a receiver address (RA) field 306, a transmitter address (TA) field 308, a sounding dialogue token field 310, one or more STA information fields 312 (i.e., STA information 1...STA information n), and a frame check sequence (FCS) field 314. The frame control field 302 may be 2 octets. The duration field 304 may be 2 octets. The RA field 306 may be 6 octets. The TA field 308 may be 6 octets. The Sounding Dialogue Token field 310 may be one octet. One or more STA Information fields 312 may each be four octets. The FCS field 314 may be four octets. The Frame Control field 302, Duration field 304, RA field 306, and TA field 308 may constitute the MAC header 320. The purpose and function of the fields shown in Figure 3 are defined in the 802.11ax standard and are known and understood by those skilled in the art.

[0085] Figure 4 shows an exemplary format of the STA information field 312 within the NDPA frame 300 shown in Figure 3. Those skilled in the art will recognize and understand this 802.11ax STA information field format. The STA information field 312 format may include an Associated ID (AID) subfield 402, a Partial BW Information subfield 404, a Reserved subfield 406, an Nc subfield 408, a Feedback Type and Ng subfield 410, a Deambiguation subfield 412, a Codebook Size subfield 414, and a Reserved subfield 416. The AID subfield 402 may be 11 bits. The Partial BW Information subfield 404 may be 9 bits. The Reserved subfield 406 may be 1 bit. The Nc subfield 408 may be 4 bits. The Feedback Type and Ng subfield 410 may be 2 bits. The Deambiguation subfield 412 may be 1 bit. The codebook-size subfield 414 may be 1 bit. The reserved subfield 416 may be 3 bits. The purpose and function of the subfields shown in Figure 4 are defined in the 802.11ax standard and are known and understood by those skilled in the art.

[0086] Trigger frames were first introduced in 802.11ax to allocate resources and trigger single or multi-user access on uplinks. Figure 5 shows an example of the trigger frame format. In 802.11be, a new variation of the user information field was proposed, with a special user information field added after the common information field. Both enhancements, as shown in Figures 6 and 7, enable a unified triggering scheme for both HE and EHT devices.

[0087] Figure 5 shows an example of a trigger frame format. Those skilled in the art will recognize and understand this 802.11ax trigger frame format. The trigger frame 500 may include a frame control field 502, a duration field 504, an RA field 506, a TA field 508, a common information field 510, a user information list field 512, a padding field 514, and an FCS field 516. The frame control field 502, the duration field 504, the RA field 506, and the TA field 508 may process the MAC header 520. The frame control field 502 may be 2 octets. The duration field 504 may be 2 octets. The RA field 506 may be 6 octets. The TA field 508 may be 6 octets. The common information field 510 may be 8 octets or more. The user information list field 512 and the padding field 514 may be variable octets. The FCF field 516 may be 4 octets long. The purpose and function of the field shown in Figure 5 are defined in the 802.11ax standard and are known and understood by those skilled in the art.

[0088] Figure 6 shows an example of the format of the user information field 512 described in Figure 5. Those skilled in the art will recognize and understand this 802.11ax user information field format. The EHT user information field 512 may include the AID subfield 602, the RU allocation subfield 604, the UL FES coding type subfield 606, the UL EHT-MCS subfield 608, the reserved subfield 610, the SS allocation / RA-RU information subfield 612, the UL target received power subfield 614, the PS160 subfield 616, and the trigger-dependent user information subfield 618. The AID12 subfield 602 may be 12 bits. The RU allocation subfield 604 may be 8 bits. The UL FES coding type subfield 606 may be 1 bit. The UL EHT-MCS subfield 608 may be 4 bits. The reserved subfield 610 may be 1 bit. The SS allocation / RA-RU information subfield 612 may be 6 bits. The UL target received power subfield 614 may be 7 bits. The PS160 subfield 616 may be 1 bit. The trigger-dependent user information subfield 618 may be variable bits. The purpose and function of the subfields shown in Figure 6 are defined in the 802.11ax standard and are known and understood by those skilled in the art.

[0089] The content of the trigger-dependent user information subfield 618 depends on the type of trigger frame that carries the EHT user information field. For example, a beamforming feedback report pole (BFRP) trigger frame may have a trigger-dependent user information field that carries certain information, while a general trigger frame may have a trigger-dependent user information field that carries other different information.

[0090] Figure 7 shows an example of the EHT special user information field format. The EHT special user information field 700 may include the AID subfield 702, the PHY version ID subfield 704, the UL bandwidth extension subfield 706, the space reuse 1 subfield 708, the space reuse 1 subfield 710, the U-SIG ignore and verification subfield 712, the reserved subfield 714, and the trigger-dependent user information subfield 716. The AID12 subfield 702 may be 12 bits. The PHY version ID subfield 704 may be 3 bits. The UL bandwidth extension subfield 706 may be 2 bits. The space reuse 1 subfield 708 may be 4 bits. The space reuse 2 subfield 710 may be 4 bits. The U-SIG ignore and verification subfield 712 may be 12 bits. The reserved subfield 714 may be 3 bits. The trigger-dependent user information subfield 716 may be of variable bits. The content of trigger-dependent user information depends on the type of trigger frame that carries the EHT user information field. For example, a beamforming feedback report pole (BFRP) trigger frame may have a trigger-dependent user information field that carries certain information, while a general trigger frame may have a trigger-dependent user information field that carries other different information.

[0091] In 802.11be systems, the first problem arises when enhancing the trigger frame design described above in Figure 5. The EHT sounding protocol may exhibit some differences from the HE sounding protocol. The EHT sounding protocol may require improvements to the trigger frame 500 (e.g., the BFRP trigger frame) described in Figure 5 to accommodate changes in the EHT sounding protocol.

[0092] Extended sounding schemes can significantly reduce CSI feedback size and enable performance improvements. However, such schemes may require more complex calculations and may take longer to execute. To accommodate extended channel sounding schemes, trigger frames may require some modifications. Several procedures and features may be defined to enable extended sounding schemes.

[0093] The second problem is that the overall duration of the current sounding protocol is dominated by the feedback reporting time. This is mainly due to the large number of bits required by the compressed beamforming report. Therefore, it is desirable to have a new sounding protocol that reduces the overall duration of the sounding protocol while minimizing channel accuracy loss.

[0094] The third problem is that the overall duration of the sounding protocol is proportional to the number of APs. In a MAP environment, the STA needs to report the channel status to both its associated APs and OBSS APs. This can make the MAP sounding protocol longer and more complex. Therefore, it is desirable to have a new sounding protocol in MAP that shortens the overall duration of the sounding procedure and makes channel status reporting more efficient.

[0095] The aforementioned problems are addressed by the embodiments described below.

[0096] One method is to use one bit in the reserved subfield 714 of the special user information field 700 of the BFRP trigger frame to indicate whether the requested sounding feedback is an EHT compression / CQI report or a non-EHT (including HE or legacy) compression beamforming / CQI report. For example, bit=1 indicates that an EHT compression beamforming / CQI report is requested. Bit=0 indicates that a non-EHT beamforming / CQI report is requested.

[0097] If non-EHT compressed beamforming / CQI reporting is requested, a non-AP STA can decode the bits in the trigger-dependent user information subfield 618 in Figure 6, i.e., the feedback segment retransmission bitmap, to determine which feedback segment is requested. If EHT compressed beamforming / CQI reporting is requested, a non-AP non-EHT STA can ignore it. In the latter case where EHT compressed beamforming / CQI reporting is requested, the trigger-dependent user information subfield 618 may be used for other purposes. For example, the trigger-dependent user information subfield 618 may be used to indicate the NDP format and feedback format, or to indicate which beamformed NDP (or precoded EHT-LTF set which may contain Ns EHT-LTFs, where Ns is a function of the transmitting antenna in the beamformer) is being transmitted. An exemplary definition of the trigger-dependent user information subfield 618 in the BFRP trigger frame used for feedback format indication (as described in Figure 5 above) is given in Table 1 below.

[0098] [Table 1]

[0099] In one method, when a beamformed NDP (either an individual beamformed NDP, a multi-beamformed NDP, or a variation of a multi-beamformed NDP) is transmitted, the trigger-dependent user information subfield 618 may be used to indicate which beamformed NDP (or precoded EHT-LTF set) is being transmitted. If the bit at position n (n=0 for LSB, n=7 for MSB) is 1, the nth beamformed NDP (or the nth EHT-LTF set) is being transmitted. For example, if the bit at position 1 is 1, either only the first precoded NDP is transmitted in the individual beamformed NDP scheme, or the first precoded EHT-LTF set (containing Ns EHT_LTFs, where Ns is a function of the number of transmitting antennas in the beamformer) is transmitted in a multi-beamformed NDP, or the first EHT-LTF set in the first beamformed NDP is transmitted in a variation of a multi-beamformed NDP. If the bits at all positions are equal to 1, all beamformed NDPs are transmitted in each individual beamformed NDP. Alternatively, all precoded EHT-LTF sets are transmitted in a multi-beamformed NDP or a variation thereof. Note that the bit at position n may refer to one beamformed NDP or one precoded EHT-LTF set. The bit may also refer to one group of beamformed NDPs or one group of precoded EHT-LTF sets. Exemplary definitions of the trigger-dependent user information subfield 618 format in a BFRP trigger frame (as illustrated in Figure 5 above) used for beamformed NDP (or EHT-LTF set) retransmission bitmaps are given in Table 2 below.

[0100] [Table 2]

[0101] In one embodiment, to prevent high data-rate transmission of TB PPDUs in the TB sounding sequence, the value given in the UL EHT-MCS subfield 608 of the user information field 512 in Figure 6, which indicates the EHT TB PPDU requested for transmission, may not result in a data rate of TB PPDUs greater than a certain value (e.g., 1.5 Gbps). Alternatively, more padding bits may be added to the BFRP trigger frame to give the receiving STA more time to process the CSI feedback. A corresponding solution is to use a reserved value in the trigger frame 500MAC padding duration subfield of the HE MAC capability information field, i.e., to set it to 3 to indicate any value greater than 16 microseconds. This indication may also be specified only for the BFRP trigger frame.

[0102] Alternatively, one reserved bit in the EHT MAC capability information field may be used to indicate the TB sounding feedback rate limit. For example, the reserved bit may be set to 0 to indicate that the maximum supported data rate for EHT compressed beamforming / CQI reporting in the EHT TB sounding sequence is the same as the maximum supported rate for TB PPDU data transmission calculated from the EHT capability element's supported EHT MCS and NSS set fields. The reserved bit may be set to 1 to indicate that the maximum supported data rate for EHT compressed beamforming / CQI reporting in the EHT TB sounding sequence is the minimum of a fixed data rate (e.g., the fixed data rate is 1.5 Gbps) and is the maximum supported rate for TB PPDU data transmission calculated from the EHT capability element's supported EHT MCS and NSS set fields.

[0103] Alternatively, one reserved bit within an EHT PHY capability element (e.g., B63 or B0) may be used to indicate the maximum supported data rate for EHT compressed beamforming / CQI reporting in the EHT TB sounding sequence. For example, the reserved bit may be set to 0 to indicate that the maximum supported data rate for EHT compressed beamforming / CQI reporting in the EHT TB sounding sequence is the same as the maximum supported rate in TB PPDU data transmission calculated from the supported EHT MCS and NSS set fields of the EHT capability element. The reserved bit may be set to 1 to indicate that the maximum supported data rate for EHT compressed beamforming / CQI reporting in the EHT TB sounding sequence is the minimum value of the fixed data rate (e.g., the fixed data rate is 1.5 Gbps) and is the maximum supported rate in TB PPDU data transmission calculated from the supported EHT MCS and NSS set fields of the EHT capability element.

[0104] Enabling the extended sounding method may require modifications to trigger frame 500. The processing required to identify the best (or worst for beam disabling) vector index or beam index may take longer than the processing required in legacy CSI feedback. Therefore, it is desirable to allow for more processing time (especially in the case of low-end devices).

[0105] In one embodiment, the AP may enable more processing time by using a padding subfield 514 in the trigger frame 500, as shown in Figure 5. The AP may increase the padding length to enable sufficient time for the worst-case scenario, taking into account the weakest device that may be identified in the capability exchange performed early in the association.

[0106] In one embodiment, the AP may add several dummy user information subfields to the user information list field 512 described. These dummy subfields may be addressed using a reserved AID or any other AID as needed. This may extend the time available before the STA is required to send index-based CSI feedback.

[0107] In one embodiment, the AP may group the STAs based on their capabilities, in which case powerful devices may be triggered to send their CSI feedback in the first round of trigger / CSI feedback, as well as computationally limited devices may be triggered to send their feedback later. The grouping of STAs may also be based on capability exchanges performed in association, and may consist of two or more groups classified by their processing capabilities.

[0108] In one embodiment, the AP may signal that the expected inter-frame space is longer than SIFS by using one or more bits in the common information field 510 in the trigger frame 500 described in Figure 5. In one example, extended inter-frame space (EIFS) may be used instead of SIFS. In another example, the AP may signal that the inter-frame space is N times SIFS, and to enable this option, the AP may signal a parameter N using one or more bits in the common information field.

[0109] In some cases, it may be desirable to enable mixed feedback within the same channel sounding session. This may allow receiving CSI feedback from both a legacy STA and an STA supporting the Extended Channel Sounding scheme within the same channel sounding round. In one embodiment, the AP may group the STAs so that the legacy STA may be triggered in a trigger frame within a triggering / CSI feedback round, while the advanced STA may be triggered in a separate trigger frame in the next round. This may allow more time for the STA supporting the Extended Channel Sounding scheme to process the CSI feedback.

[0110] In multi-AP channel sounding, as illustrated in Figure 2, CSI feedback about the channel between coordinating / coordinated APs and STAs involved in the sounding session can be collected in different ways. In one method (Method 1), each AP can collect CSI feedback from its associated STA and from the OBSS STA. In another method (Method 2), each AP can collect CSI feedback only from its associated STA. In yet another method (Method 3), the coordinating AP collects feedback from all STAs for all APs.

[0111] In the three extended channel sounding schemes described above, the CSI feedback can be index-based feedback, where the index can refer to a precoding matrix / vector that is most correlated with the true channel matrix V. Therefore, the feedback can be very few bits per subcarrier (compared to tens to hundreds of octets in legacy compressed beamforming feedback).

[0112] In one embodiment (considering method 2 above), an AP may trigger its associated STA to transmit a combined index-based beamforming report, including CSI feedback between the STA and all or some of the APs involved in the sounding session. For example, one bit in the STA information field 312 having an AID 12 corresponding to a given STA in the trigger frame 500 may be reused to indicate whether the STA is expected to send individual CSI feedback (channel feedback only to its associated AP) or combined CSI feedback. Additionally or alternatively, a trigger-dependent user information subfield 618 of the user information field 512 may be used to indicate whether the expected feedback is individual feedback or combined feedback. An AP receiving combined CSI feedback, including CSI feedback from other APs, may then transmit those CSI feedback wirelessly or using wired backhaul.

[0113] The following embodiments address how to design an efficient sounding protocol, as illustrated in Figure 2, to reduce the overall duration, including the MAP-NDPA frame 206, NDP frames 210a, 210b, and 210c, trigger frame 214, and feedback reports 216a, 216b, and 216c.

[0114] A sounding protocol with enabled V-index (VI) feedback (where only the index of a predefined V-matrix is ​​fed back, and the predefined V-matrix is ​​known by the beamformer and beamformer) is described below. In the VI feedback protocol, the STA may require a longer processing time to determine the V-matrix index that best (or worst) matches the real channel for beam invalidation. Therefore, the sounding protocol may require an extended design to compensate for the longer processing time required for VI feedback. Multiple solutions exist that may be used in different scenarios.

[0115] In one scenario, there may be two Class 2 STAs, as shown in Figure 8. As shown in Figure 8, beamformer 802 transmits NDPA 806, NDP 808, and an extended BFRP trigger 810. The extended BFRP trigger frame 810 may have the trigger frame format 500 described in Figure 5 above.

[0116] In response to the extended BFRP trigger 810, beamformers 804a and 804b transmit feedback reports 812a and 812b, respectively. In the scenario shown in Figure 8 (i.e., the scenario with only two Class 2 STAs), one approach is to define a longer waiting time 814 between the extended BFRP trigger frame 810 and the feedback reports 812a and 812b. This longer waiting time 814 may be nSIFS (e.g., n=3), but may also be indicated in the extended BFRP trigger 810. In Figure 8, beamformer 802 may be an AP, while beamformers 804a and 804b may be STAs.

[0117] There are at least two options for including this indication (i.e., latency 814) in the extended BFRP trigger 810. In one option, the indication may use reserved bits in a common information field (such as the common information field 510 in the trigger frame 500 in Figure 5) to indicate whether the latency is normal (i.e., SIFS or longer than normal (e.g., nSIFS, n>1)). In another option, the indication may use a feedback segment retransmission bitmap indicated in the trigger-dependent user information subfield 618. In the VI feedback scheme, the feedback bits are significantly reduced, so there will be far fewer segments in the report. One bit in the feedback segment retransmission bitmap may be used to indicate whether the latency is longer.

[0118] As shown in Figure 8, beamformer 802 may be AP, while beamformers 804a and 804b may be STA.

[0119] Alternatively, another approach might be to group C2 STAs based on their capabilities (e.g., signal processing capabilities, or the ability to access different subsets of a predefined set of precoders). The same group of C2 STAs could then be scheduled to feed back CSIs simultaneously.

[0120] Figure 9 shows an exemplary sounding protocol for group-based VI feedback. For example, beamformers 904a and 904b may be EHT R2 STA (i.e., Group 1), while beamformers 904c and 904d may be later STA (i.e., Group 2).

[0121] The beamformer 902 transmits NDPA 906, NDP 908, and the extended BFRP trigger 910a. Upon receiving the extended BFRP trigger 910a, the beamformers 904a and 904b (which have high processing power or can access only a smaller subset of the precoder) transmit feedback reports 912a and 912b. The extended BFRP triggers 910a and 910b may have the trigger frame format 500 described in Figure 5 above. The beamformer 902 may be an AP, while the beamformers 904a, 904b, 904c, and 904d may be STAs.

[0122] Next, beamformer 902 transmits an extended BFRP trigger 910b. Upon receiving the extended BFRP trigger 910b, beamformers 904c and 904d (which have lower processing power or access to a larger subset of the precoder) are scheduled to transmit feedback 914a and 914b after feedback 914a and 914b. Trigger frames may be sent before each group of VI feedback transmissions. The waiting time between each BFRP trigger frame and the VI feedback is the normal waiting time (i.e., SIFS).

[0123] In another scenario, there may be a mix of classified STAs, each required to report channel state information for (1) Class 1 STAs (EHT R1 and earlier STAs) and (2) Class 2 STAs (EHT R2 and later STAs). Figure 10 shows an exemplary VI sounding protocol with mixed-class STAs (i.e., C1 STAs and C2 STAs).

[0124] EHT R1 STA is an EHT STA that does not implement any EHT functions that cannot be shown in the EHT capability elements. Pre-EHT STAs are legacy STAs that do not implement EHT functions. EHT R2 and later STAs are STAs that implement advanced functions that are not present in legacy and EHT R1 STAs.

[0125] Figure 10 shows an example of a VI sounding protocol using a mixed class of STAs (e.g., C1 STA and C2 STA). Similar to Figures 8 and 9, the beamformer 1002 transmits NDPA 1006, NDP 1008, extended BFRP trigger 1010a, and extended BFRP trigger 1010b. Extended BFRP triggers 1010a and 1010b may have the trigger frame format 500 described in Figure 5 above.

[0126] As shown in Figure 10, one method may be to first request beamforming reports 1012a and 1012b from beamformers 1004a and 1004b (i.e., C1 STA) via an extended BFRP trigger 1010a. After the legacy compressed beamforming reports 1012a and 1012b are reported, VI feedback reports 1014a and 1014b are requested by another extended trigger frame 1010b. The legacy non-AP (C1) STA can send back a compressed beamforming report with an allocated potentially larger BW using the OFDMA method. The C2 STA can also send VI feedback using OFDMA. The waiting period between the trigger frame and the beamforming report or VI report is the same (i.e., SIFS as shown in Figure 10). Beamformer 1002 may be an AP, while beamformers 1004a, 1004b, 1004c, and 1004d may be STAs.

[0127] Multiple implementations address the sounding procedure for beamformed NDPs (where the NDP is precoded by multiple precoders, and the STA is requested to send the precoder indices). For example, precoders with the best match for the channel (or worst match for beam invalidation), or precoders with the minimum match for the channel, are described below. Multiple implementations may be used for various scenarios.

[0128] In one scenario, only Class 2 STAs (i.e., STAs with EHT R2 or later) may be required to transmit channel state information. The EHT symbol may be applied along with all N_B precoders transmitted within a single NDP frame.

[0129] Figure 11 shows an example of a beamformed NDP sounding protocol using only Class 2 (C2) STAs. The beamformer 1102 transmits an NDPA 1106, an NDP 1108, and an extended BFRP trigger 1110. The NDP 1108 may be a beamformed NDP with multiple beams. The extended BFRP trigger 1110 may have the trigger frame format 500 described in Figure 5 above. Upon receiving the extended BFRP trigger 1110, one or more C2 beamformers 1104 transmit a feedback report 1112. The beamformer 1102 may be an AP, but the beamformers 1104 may be STAs.

[0130] Alternatively, as shown in Figure 12, the beamformer can transmit EHT symbols with different precoders in K NDPs so that the non-AP STA does not need to process many EHTs in a short time. To reduce the overall duration, an exemplary value of K may be 2 or 3.

[0131] Figure 12 shows another example of a beamformed NDP sounding protocol using a C2 STA. As shown in Figure 12, similar to Figure 11, the beamformer 1202 transmits an NDP 1206. However, in contrast to Figure 11, instead of transmitting a single NDP frame, the beamformer 1202 transmits one or more beamformed NDPs 1204a, 1204b, and 1204n. The beamformer 1202 then transmits an extended BFRP trigger frame 1210. In response, one or more beamformers 1204 transmit a feedback report 1212. The extended BFRP trigger frame 1210 may have the trigger frame format 500 described in Figure 5 above. The beamformer 1202 may be an AP, while the beamformers 1204 may be STAs.

[0132] In another scenario, there is a mix of C1 and C2 STAs that are required to transmit channel status information. As shown in Figure 13, to enable inverse capability, the beamformer can choose to have the first NDP transmitted with one precoder or non-precoder, and the remaining NDPs transmitted with precoded EHT symbols, as shown in Figure 13.

[0133] Similar to Figure 12, in Figure 13, the beamformer 1302 transmits an NDPA 1306 and one or more beamformed NDPs 1304a, 1304b, and 1304n. Next, the beamformer 1302 transmits an extended BFRP trigger 1310. In response, one or more beamformers 1304 transmit a feedback report 1312. The extended BFRP trigger 1310 may have the trigger frame format 500 described in Figure 5 above. The beamformer 1302 may be an AP, while the beamformers 1304 may be STAs.

[0134] However, in contrast to Figure 12, in order to enable reverse capability, the beamformer may choose to transmit the first NDP with one precoder or non-precoder, as shown in Figure 13, and the remaining NDPs with precoded EHT symbols.

[0135] In this case, the number of EHTs may differ for each NDP. Information regarding the number of EHT-LTFs and the transmission mode of the EHTs (precoded or unprecoded) may be shown in the NDPA STA information subfield 312, as shown in Figures 3 and 4. Alternatively, SIFs between NDPs may be removed. The duration of each NDP should be defined in the NDPA. NDP → BFRP → BF may be repeated for beam fine-tuning and beam tracking.

[0136] The following describes implementation methods for optimizing the sounding procedure in a MAP environment. In one method, when multiple APs request index-based feedback, the STA requested to send it can combine its feedback reports and send them back to one AP (e.g., its associated AP). The AP that receives feedback from multiple APs can then forward the CSI to the corresponding AP.

[0137] Figure 14 shows an example of a MAP sounding protocol using index feedback. In Figure 14, AP1 1402a is associated with STA 1404a and 1404b, and AP2 1402b is associated with STA 1404c and 1404d. AP1 1402a transmits NDPA 1406a, NDPA 1408a, and an extended BFRP trigger 1410a. AP2 1402b can transmit NDPA 1406b, NDPA 1408b, and an extended BFRP trigger 1410b. Upon receiving the extended BFRP trigger 1410a, STA1404a can transmit an index feedback report 1412a, and STA1404b can transmit an index feedback report 1412b. Upon receiving an extended BFRP trigger 1410b, STA1404c may transmit an index feedback report 1412c, and STA1404d may transmit an index feedback report 1412d. Index feedback reports 1412a, 1412b, 1412c, and 1412d may be transmitted simultaneously. Index feedback reports 1412a, 1412b, 1412c, and 1412d may be VI feedback, beam index feedback, or other short feedback reports.

[0138] The extended BFRP triggers 1410a and 1410b may have the trigger frame format 500 described in Figure 5 above.

[0139] An AP can trigger its associated STA to send a combined feedback report, including VI feedback for several APs within the same CSI feedback frame. To enable this feature, several modifications can be introduced to the EHT compressed beamforming / CQI frame format.

[0140] In one embodiment, several entries may be added to the EHT action field value table to illustrate a new format for extended feedback. For example, an entry with value 1 (or any other value) may be added to indicate that the feedback management frame carries extended index-based CSI feedback, while another entry with value 2 (or any other value) may be added to indicate that the feedback management frame carries combined extended index-based CSI feedback. Table 3 shows exemplary EHT action field values.

[0141] [Table 3]

[0142] In one embodiment, one or more bits in the EHT MIMO control field can be used to indicate that the beamforming feedback frame is carrying either an individual enhanced beamforming report or a combined enhanced beamforming report. For example, one bit may be named individual / combined, so that it is set to 0 to signal that the beamforming report being carried is an individual report, or to 1 to indicate that the beamforming report is a combined report.

[0143] In one embodiment, a subfield may be added to the MIMO control field having a size of 2 bits or more (the number of combined reports subfield), which may be used to indicate how many beamforming reports are combined in the feedback frame (the N parameter shown in Table 4).

[0144] [Table 4]

[0145] In one example, if the minimum number of combined reports is two (N=2), 2 bits may be used. Table 5 shows an example of encoding.

[0146] [Table 5]

[0147] In one embodiment, combined reports may be ordered in ascending order of AP IDs such that the first enhanced beamforming report is directed to the AP with the smallest ID, and the last enhanced beamforming report is directed to the AP with the largest ID. A trigger AP that sends a trigger frame to request the transmission of an enhanced beamforming report may have a list of all APs involved in this channel sounding session and a mapping of which APs can expect channel sounding feedback from which STAs. This information may be exchanged in a multi-AP NDPA, which may be sent as the first step in a multi-AP channel sounding procedure.

[0148] In one embodiment, a combined report map field may be added to the enhanced beamforming / CQI frame to indicate which beamforming report is addressed to which AP, as shown in Table 6. For example, the combined report map may be designed to consist of N elements, each representing an AP ID that maps to the corresponding report (e.g., the first AP ID is the AP mapped to the first enhanced beamforming report, and so on).

[0149] [Table 6]

[0150] Figure 15 shows an exemplary embodiment of a single beamformed MAP sounding procedure. Beamformer 1502a may transmit a leading AP NDPA. Beamformers 1502a and 1502b then transmit NDPAs 1508a and 1508b, NDPPs 1510a and 1510b, and extended BFRP triggers 1512a and 1512b, respectively. In response, beamformer 1504a transmits BF index 1514a, beamformer 1504b transmits BF index 1514b, beamformer 1504c transmits BF index 1514c, and beamformer 1504d transmits BF index 1514d. Extended BFRP triggers 1510a and 1510b may have the trigger frame format 500 described in Figure 5 above.

[0151] In Figure 15, N AP = 2, and it is assumed that the beamform can be either C2 or C1. As shown in Figure 15, this embodiment assumes that the number of EHT-LTFs is

[0152]

number

[0153] Each AP may apply a different number of precoders to EHT_LTF, i.e., N B,i This may differ for each AP. SS,BF-NDP,i and N B,i Both of them are AP i This is indicated by the NDPA STA information field transmitted from. Some APs are not precoded EHT-LTF, i.e., N B,i You may send =1.

[0154] FIG. 16 shows an example of a single beamformed NDP frame 1600. The NDP frame 1600 may include an L-STF field 1602, an L-LTF field 1604, an L-SIG field 1606, an RL-SIG field 1608, a U-SIG field 1610, an EHT-SIG field 1612, an EHT-STF field 1614, one or more AP1-EHT-LTF fields 1616, one or more AP2-EHT-LTF fields 1618, and a PE field 1620. The fields 1602 to 1612 may be transmitted by a leading AP or another AP.

[0155] Interleaved AP transmissions may be used to reduce the number of EHT-LTFs in the MAP sounding protocol. As shown in FIG. 17, in one implementation, the APs can send their EHT-LTFs on different tones. In this example, the total number of EHT-LTFs in a single beamformed NDP is N EHT-LTF = N×M. Here

[0156]

Number

[0157] In another implementation, interleaved multi-beam transmissions may be used to reduce the number of EHT-LTFs in the MAP sounding protocol. In this embodiment, as shown in FIG. 18, this method is to apply different precoders on different tones to the EHT-LTFs from the same AP. In this example, the total number of EHT-LTFs in a single beamformed NDP is

[0158]

Number

[0159] In another implementation, interleaved multibeam and AP transmissions may be used to reduce the number of EHT-LTFs in the MAP sounding protocol. This implementation applies different precoders with different tones to EHT-LTFs from different APs, as shown in Figure 19. In this example, the total number of EHT-LTFs in a single beamformed NDP is

[0160]

number

[0161] In one embodiment, two bits in the EHT PHY capability information field can be used to indicate different MU beamformer capabilities with respect to bandwidth support. For example, only B61 and B60 are used to indicate different MU beamformer capabilities. When both bits (B61 and B60) are set to 0, it indicates a MU beamformer that does not support a 160 MHz channel width in the HE capability element and supports only an 80 MHz channel width. When bits (B61 and B60) are set to 01, it indicates a MU beamformer that supports a 160 MHz channel width. When bits (B61 and B60) are set to 10, it indicates that the beamformer is a MU beamformer that supports a 320 MHz channel width. B62 may be reserved for other purposes. Alternatively, any other two bits from B60 and B62 may be used to indicate the MU beamformer capability with respect to bandwidth support, and the remaining bit is reserved for other uses.

[0162] In one embodiment, the STA identified in the EHT NDP announcement frame may be the same as the STA triggered by the BFRP trigger frame in the same TXOP of the EHT TB sounding sequence.

[0163] While features and elements are described above in specific combinations, those skilled in the art will understand that each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein can be implemented in computer programs, software, or firmware embedded in computer-readable media for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via 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 associated 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 use in beamform, Receiving a null data packet announcement frame (NDPA) from the beamformer, Receiving null data packet (NDP) frames from the beamformer based on the NDPA, The beamformer receives an Extended Beamforming Request Pole (BFRP) trigger frame including an indication of the feedback format, Based on the NDP frame, a feedback frame including a feedback report is transmitted to the beamformer using the format indicated by the feedback format of the BFRP trigger frame. Methods that include...

2. The method according to claim 1, wherein the BFRP trigger frame is an extended beamforming report pole (BFRP) trigger frame.

3. The method according to claim 1, wherein the feedback report is a beamforming report.

4. The method according to claim 1, wherein the feedback report is a vector index (VI) feedback report.

5. The method according to claim 1, wherein the beamformer is an access point (AP).

6. The method according to claim 1, wherein the beamformer is a station (STA).

7. It's beamform, Processor and Receiver and Transmitter and, Equipped with, The processor and the receiver Receiving a null data packet announcement frame (NDPA) from the beamformer, Receiving null data packet (NDP) frames from the beamformer based on the NDPA, The system is configured to receive an Extended Beamforming Request Pole (BFRP) trigger frame from the beamformer, which includes an indication of the feedback format. A beamformer is configured such that the processor and the transmitter transmit a feedback frame, including a feedback report, to the beamformer based on the NDP frame, using the format indicated by the feedback format of the BFRP trigger frame.

8. The beamforming according to claim 7, wherein the BFRP trigger frame is an extended beamforming report pole (BFRP) trigger frame.

9. The beamforming machine according to claim 7, wherein the feedback report is a beamforming report.

10. The beamformer according to claim 7, wherein the feedback report is a vector index (VI) feedback report.

11. The beamformer according to claim 7, wherein the beamformer is an access point (AP).

12. The beamformer according to claim 7, wherein the beamformer is a station (STA).

13. A method performed by a beamformer, Sending a Null Data Packet Announcement Frame (NDPA) and Sending a null data packet (NDP) frame, Sending a first Extended Beamforming Request Pole (BFRP) trigger frame that includes a feedback format indication, Based on the indication of the feedback format, receive one or more beamforming reports from a first set of beamformers. Sending a second Extended Beamforming Request Pole (BFRP) trigger frame that includes a feedback format indication, Based on the indication of the feedback format, receive one or more feedback reports from a second set of beamformers, Methods that include...

14. The method according to claim 13, wherein the feedback report is a vector index (VI) feedback report.

15. The method according to claim 13, wherein the beamformer is an access point (AP).

16. The method according to claim 13, wherein the beamformer is a station (STA).

17. The method according to claim 1, wherein the feedback frame is further based on the NDPA.

18. The beamformation according to claim 7, wherein the feedback frame is further based on the NDPA.

19. The method according to claim 2, wherein the BFRP trigger frame includes a trigger-dependent user information subfield.

20. The beamformer according to claim 8, wherein the BFRP trigger frame includes a trigger-dependent user information subfield.

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