CN117356038A

CN117356038A - Multi-AP channel sounding feedback procedure for WLAN systems

Info

Publication number: CN117356038A
Application number: CN202280036689.6A
Authority: CN
Inventors: M·萨阿德; 娄汉卿; 王晓飞; 林梓楠; 杨瑞
Original assignee: InterDigital Patent Holdings Inc
Current assignee: InterDigital Patent Holdings Inc
Priority date: 2021-04-23
Filing date: 2022-04-22
Publication date: 2024-01-05

Abstract

A Station (STA) associated with a first Access Point (AP) that is a member of a multi-AP set receives a trigger frame from a second AP that is also a member of the multi-AP set. The STA is not associated with the second AP. The trigger frame includes an Association Identifier (AID) related to an association between the STA and the first AP and an AP identifier (APID) of the first AP. The STA transmits a feedback message to the second AP, the feedback message including information indicating a channel quality of a communication channel between the STA and the second AP. Various formats of trigger frames for requesting feedback from an OBSS STA are disclosed.

Description

Multi-AP channel sounding feedback procedure for WLAN systems

Cross Reference to Related Applications

The present application claims the benefit of U.S. provisional application No. 63/178,936 filed on month 4 of 2021 and U.S. provisional application No. 63/191,651 filed on month 5 of 2021, the contents of which are incorporated herein by reference.

Background

A Wireless Local Area Network (WLAN) in an infrastructure Basic Service Set (BSS) mode may include an Access Point (AP) for the BSS and one or more Stations (STAs) associated with the AP. An AP may access or interface with a Distributed System (DS) or other type of wired/wireless network that carries traffic into and out of the BSS. Traffic originating outside the BSS to the STA arrives through the AP and can be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be sent to the AP to be delivered to the respective destination. Traffic between STAs within the BSS may also be sent through the AP, with the source STA sending traffic to the AP and the AP delivering the traffic to the destination STA.

According to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, such as 802.11ac and/or 802.11ax, for infrastructure modes of operation, an ap may transmit beacons on a fixed channel (typically the primary channel). This channel may be 20MHz wide and may be the operating channel of a BSS. This channel may also be used by STAs to establish a connection with the AP. The basic channel access mechanism in 802.11 systems may be carrier sense multiple access/collision avoidance (CSMA/CA). In this mode of operation, some or each STA, including the AP, may sense the primary channel. If a channel busy is detected, the STA may fall back. Thus, one STA may transmit at any given time in the BSS.

In an embodiment operating in accordance with the 802.11n standard, high Throughput (HT) STAs may also communicate using a 40MHz wide channel. This may be achieved by combining the primary 20MHz channel with an adjacent 20MHz channel to form a 40MHz wide continuous channel.

In an embodiment operating in accordance with the 802.11ac standard, very High Throughput (VHT) STAs may support channels that are 20MHz, 40MHz, 80MHz, and/or 160MHz wide. The 40MHz and 80MHz channels may be formed by combining consecutive 20MHz channels similar to the 802.11n channel described above. The 160MHz channel may be formed by combining 8 consecutive 20MHz channels, or by combining two non-consecutive 80MHz channels (this may also be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data may be passed through a segment parser that splits the data into two streams. An Inverse Discrete Fourier Transform (IDFT) operation and time domain processing may be performed on each stream separately. The streams may then be mapped onto two channels and data may be transmitted. At the receiver, this mechanism may be reversed and the combined data may be sent to the MAC.

To improve spectral efficiency, a system operating in accordance with the 802.11ac standard may implement the concept of downlink multi-user MIMO (MU-MIMO) transmission from an AP to multiple STAs in a time frame of the same symbol, e.g., during a downlink OFDM symbol. For embodiments operating in accordance with the 802.11ah standard, the possibility of using downlink MU-MIMO may also be considered. It is important to note that interference to waveform transmissions to multiple STAs may not be a problem since downlink MU-MIMO as used in 802.11ac may use the same symbol timing for transmissions to multiple STAs. However, all STAs involved in the MU-MIMO transmission from the AP may need to use the same channel or frequency band, and this may limit the operating bandwidth to the minimum channel bandwidth supported by the STA included as the destination of the MU-MIMO transmission from the AP.

Disclosure of Invention

In one embodiment, the trigger frame is a beamforming report poll (BFRP) trigger frame. The BFRP trigger frame includes a user information field including an AID related to association between the STA and the first AP. The user information field also includes a trigger related user information field including an Overlapping Basic Service Set (OBSS) indicator and an APID of the first AP. The OBSS indicator indicates that the APID is an Overlapping Basic Service Set (OBSS) AP.

In another embodiment, the trigger frame is a BFRP trigger frame, and the BFRP trigger frame includes a new special user information field and at least one user information field. The new special user information field includes a user pointer field associated with the corresponding user information field. The user pointer field includes an APID and the corresponding user information field includes an AID related to association between the STA and the first AP.

In the disclosed embodiments, OBSS STAs (i.e., unassociated STAs) that receive the BFRP trigger frame may be explicitly identified using AID and APID. The OBSS STA may then transmit feedback to the unassociated AP.

Drawings

A more detailed understanding of the description may be derived from the following description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements, and in which:

FIG. 1A is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented;

fig. 1B is a system diagram illustrating an exemplary wireless transmit/receive unit (WTRU) that may be used within the communication system shown in fig. 1A according to one embodiment;

fig. 1C is a system diagram illustrating an exemplary Radio Access Network (RAN) and an exemplary Core Network (CN) that may be used within the communication system shown in fig. 1A according to one embodiment;

fig. 1D is a system diagram illustrating another exemplary RAN and another exemplary CN that may be used in the communication system shown in fig. 1A according to one embodiment;

fig. 2 illustrates an example of a sequential channel sounding procedure and a joint channel sounding procedure performed in a multi-AP system;

fig. 3 illustrates an example of a High Efficiency (HE) Null Data Packet (NDP) announcement frame format;

fig. 4 shows an example of a STA information field format in an EHT NDP announcement frame;

fig. 5 shows an example of a trigger frame format;

fig. 6 shows an example of an Extremely High Throughput (EHT) variant user information field format;

FIG. 7 illustrates an example of an EHT special user information field format;

fig. 8 illustrates an exemplary process for collecting Channel State Information (CSI) feedback from Overlapping BSS (OBSS) STAs;

Fig. 9 illustrates another exemplary process for collecting CSI feedback from an OBSS STA;

fig. 10 provides an example of EHT/enhanced compression beamforming/Channel Quality Information (CQI) frame action field format;

FIG. 11 illustrates an example of a trigger related user information subfield;

FIG. 12 shows an example of new special user information that may be included in a trigger frame;

fig. 13 shows an example of a modified EHT/enhanced Multiple Input Multiple Output (MIMO) control field; and is also provided with

Fig. 14 shows two embodiments for requesting OBSS STA feedback using a trigger frame.

Detailed Description

Fig. 1A is a diagram illustrating an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple-access system that provides content, such as voice, data, video, messages, broadcasts, etc., to a plurality of wireless users. Communication system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, communication system 100 may employ 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, filter Bank Multicarrier (FBMC), and the like.

As shown in fig. 1A, the communication system 100 may include wireless 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, although it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and/or communicate in a wireless environment. For example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a Station (STA), may be configured to transmit and/or receive wireless signals, and may include User Equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular telephones, personal Digital Assistants (PDAs), smartphones, laptop computers, netbooks, personal computers, wireless sensors, hot spot or Mi-Fi devices, internet of things (IoT) devices, watches or other wearable devices, head Mounted Displays (HMDs), vehicles, drones, medical devices and applications (e.g., tele-surgery), industrial devices and applications (e.g., robots and/or other wireless devices operating in an industrial and/or automated processing chain environment), consumer electronic devices, devices operating on a commercial and/or industrial wireless network, and the like. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

Communication system 100 may also include base station 114a and/or base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the internet 110, and/or the other networks 112. As an example, the base stations 114a, 114B may be Base Transceiver Stations (BTSs), node bs, evolved node bs (enbs), home node bs, home evolved node bs, next generation node bs, such as a gnnode B (gNB), new air interface (NR) node bs, site controllers, access Points (APs), wireless routers, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and/or network elements.

Base station 114a may be part of RAN 104 that may also include other base stations and/or network elements (not shown), such as Base Station Controllers (BSCs), radio Network Controllers (RNCs), relay nodes, and the like. Base station 114a and/or base station 114b may be configured to transmit and/or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage of wireless services to a particular geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with base station 114a may be divided into three sectors. Thus, in an embodiment, the base station 114a may include three transceivers, i.e., one for each sector of a cell. In an embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of a cell. For example, beamforming may be used to transmit and/or receive signals in a desired spatial direction.

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

More specifically, as noted above, communication system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, or the like. For example, the base station 114a and WTRUs 102a, 102b, 102c in the RAN 104 may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) terrestrial radio access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 116.WCDMA may include communication protocols such as High Speed Packet Access (HSPA) and/or evolved HSPA (hspa+). HSPA may include high speed Downlink (DL) packet access (HSDPA) and/or high speed Uplink (UL) packet access (HSUPA).

In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as evolved UMTS terrestrial radio access (E-UTRA), which may use Long Term Evolution (LTE) and/or LTE-advanced (LTE-a) and/or LTE-advanced Pro (LTE-a Pro) to establish the air interface 116.

In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may use NR to establish the air interface 116.

In embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, e.g., using a Dual Connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and/or transmissions sent to/from multiple types of base stations (e.g., enbs and gnbs).

In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., wireless fidelity (WiFi)), IEEE 802.16 (i.e., worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000 1X, CDMA EV-DO, tentative standard 2000 (IS-2000), tentative standard 95 (IS-95), tentative standard 856 (IS-856), global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE), GSM EDGE (GERAN), and the like.

The base station 114B in fig. 1A may be, for example, a wireless router, home node B, home evolved node B, or access point, and may utilize any suitable RAT to facilitate wireless connections in local areas such as business, home, vehicle, campus, industrial facility, air corridor (e.g., for use by drones), road, etc. In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a Wireless Local Area Network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a Wireless Personal Area Network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-a Pro, NR, etc.) to establish a pico cell or femto cell. As shown in fig. 1A, the base station 114b may be directly connected to the internet 110. Thus, the base station 114b may not need to access the internet 110 via the CN 106.

The RAN 104 may communicate with a CN 106, which may be any type of network configured to provide voice, data, application, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102 d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 may provide call control, billing services, mobile location based services, prepaid calls, internet connections, video distribution, etc., and/or perform advanced security functions such as user authentication. Although not shown in fig. 1A, it should be appreciated that RAN 104 and/or CN 106 may communicate directly or indirectly with other RANs that employ the same RAT as RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104 that may utilize NR radio technology, the CN 106 may also communicate with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, wiMAX, E-UTRA, or WiFi radio technology.

The CN 106 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the internet 110, and/or other networks 112.PSTN 108 may include circuit-switched telephone networks that provide Plain Old Telephone Services (POTS). The internet 110 may include a global system for interconnecting computer networks and devices using common communication protocols, such as Transmission Control Protocol (TCP), user Datagram Protocol (UDP), and/or Internet Protocol (IP) in the TCP/IP internet protocol suite. Network 112 may include wired and/or wireless communication networks owned and/or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

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

Fig. 1B is a system diagram illustrating an exemplary WTRU 102. As shown in fig. 1B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit/receive element 122, a speaker/microphone 124, a keypad 126, a display/touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a Global Positioning System (GPS) chipset 136, and/or other peripheral devices 138, etc. It should be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a Digital Signal Processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs), any other type of Integrated Circuit (IC), a state machine, or the like. 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 may be coupled to a transmit/receive element 122. Although fig. 1B depicts the processor 118 and the transceiver 120 as separate components, it should be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

The transmit/receive element 122 may be configured to transmit signals to and receive signals from a base station (e.g., base station 114 a) over the air interface 116. For example, in one embodiment, the transmit/receive element 122 may be an antenna configured to transmit and/or receive RF signals. In one embodiment, the transmit/receive element 122 may be an emitter/detector configured to emit 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 RF and optical signals. It should be appreciated that the transmit/receive element 122 may be configured to transmit and/or receive any combination of wireless signals.

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

The transceiver 120 may be configured to modulate signals to be transmitted by the transmit/receive element 122 and demodulate signals received by the transmit/receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, 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).

The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker/microphone 124, a keypad 126, and/or a display/touchpad 128, such as a Liquid Crystal Display (LCD) display unit or an Organic Light Emitting Diode (OLED) display unit. The processor 118 may also output user data to the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128. Further, the processor 118 may access information from and store data in any type of suitable memory, such as the non-removable memory 130 and/or the removable memory 132. The non-removable memory 130 may include Random Access Memory (RAM), read Only Memory (ROM), a hard disk, or any other type of memory storage device. 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 never physically locate memory access information on the WTRU 102, such as on a server or home computer (not shown), and store the data in that memory.

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

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

The processor 118 may also be coupled to other peripheral devices 138, which may include one or more software modules and/or hardware modules that provide additional features, functionality, and/or wired or wireless connections. For example, the number of the cells to be processed, peripheral devices 138 may include accelerometers, electronic compasses, satellite transceivers, digital cameras (for photographs and/or video), universal Serial Bus (USB) ports, vibrating devices, television transceivers, hands-free headsets, wireless communications devices, and the like,Modules, frequency Modulation (FM) radio units, digital music players, media players, video game player modules, internet browsers, virtual reality and/or augmented reality (VR/AR) devices, activity trackers, and the like. The peripheral device 138 may include one or more sensors. The sensor may be one or more of the following : gyroscopes, accelerometers, hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors; geographic position sensors, altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, humidity sensors, and the like.

WTRU 102 may include a full duplex radio for which transmission and reception of some or all signals (e.g., associated with a particular subframe for UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and/or simultaneous. The full duplex radio station may include an interference management unit for reducing and/or substantially eliminating self-interference via hardware (e.g., choke) or via signal processing by a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which some or all signals are transmitted and received (e.g., associated with a particular subframe for UL (e.g., for transmission) or DL (e.g., for reception).

Fig. 1C is a system diagram illustrating a RAN 104 and a CN 106 according to an embodiment. As noted above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using an E-UTRA radio technology. RAN 104 may also communicate with CN 106.

RAN 104 may include enode bs 160a, 160B, 160c, but it should be understood that RAN 104 may include any number of enode bs while remaining consistent with an embodiment. The enode bs 160a, 160B, 160c may each include one or more transceivers to communicate with the WTRUs 102a, 102B, 102c over the air interface 116. In an embodiment, the evolved node bs 160a, 160B, 160c may implement MIMO technology. Thus, the enode B160 a may use multiple antennas to transmit wireless signals to and/or receive wireless signals from the WTRU 102a, for example.

Each of the evolved node bs 160a, 160B, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and/or DL, and the like. As shown in fig. 1C, the enode bs 160a, 160B, 160C may communicate with each other over an X2 interface.

The CN 106 shown in fig. 1C may include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) gateway (PGW) 166. Although the foregoing elements are depicted as part of the CN 106, it should be appreciated that any of these elements may be owned and/or operated by entities other than the CN operator.

The MME 162 may be connected to each of the evolved node bs 162a, 162B, 162c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating the user of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c, and the like. MME 162 may provide control plane functionality for switching between RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and/or WCDMA.

SGW 164 may be connected to each of the evolved node bs 160a, 160B, 160c in RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to/from the WTRUs 102a, 102b, 102 c. The SGW 164 may perform other functions such as anchoring user planes during inter-enode B handover, triggering paging when DL data is available to the WTRUs 102a, 102B, 102c, managing and storing the contexts of the WTRUs 102a, 102B, 102c, etc.

The SGW 164 may be connected to a PGW 166 that may provide the WTRUs 102a, 102b, 102c with access to a packet switched network, such as the internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

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

Although the WTRU is depicted in fig. 1A-1D as a wireless terminal, it is contemplated that in some representative embodiments such a terminal may use a wired communication interface with a communication network (e.g., temporarily or permanently).

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in an infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more Stations (STAs) associated with the AP. The AP may have access or interface to a Distribution System (DS) or another type of wired/wireless network that carries traffic to and/or from the BSS. Traffic originating outside the BSS and directed to the STA may arrive through the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be sent to the AP to be delivered to the respective destination. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may pass the traffic to the destination STA. Traffic between STAs within a BSS may be considered and/or referred to as point-to-point traffic. Point-to-point traffic may be sent between (e.g., directly between) the source and destination STAs using Direct Link Setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z Tunnel DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs (e.g., all STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

When using the 802.11ac infrastructure mode of operation or similar modes of operation, the AP may transmit beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20MHz wide bandwidth) or a dynamically set width. The primary channel may be an operating channel of the BSS and may be used by STAs to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access/collision avoidance (CSMA/CA) may be implemented, for example, in an 802.11 system. For CSMA/CA, STAs (e.g., each STA), including the AP, may listen to the primary channel. If the primary channel is listened to/detected by a particular STA and/or determined to be busy, the particular STA may backoff. One STA (e.g., only one station) may transmit at any given time in a given BSS.

High Throughput (HT) STAs may communicate using 40MHz wide channels, for example, via a combination of a primary 20MHz channel with an adjacent or non-adjacent 20MHz channel to form a 40MHz wide channel.

Very High Throughput (VHT) STAs may support channels that are 20MHz, 40MHz, 80MHz, and/or 160MHz wide. 40MHz and/or 80MHz channels may be formed by combining consecutive 20MHz channels. The 160MHz channel may be formed by combining 8 consecutive 20MHz channels, or by combining two non-consecutive 80MHz channels (this may be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data may pass through a segment parser that may split the data into two streams. An Inverse Fast Fourier Transform (IFFT) process and a time domain process may be performed on each stream separately. These streams may be mapped to two 80MHz channels and data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed and the combined data may be sent to a Medium Access Control (MAC).

The 802.11af and 802.11ah support modes of operation below 1 GHz. Channel operating bandwidth and carrier are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11 ac. The 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the television white space (TVWS) spectrum, and the 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 802.11ah may support meter type control/Machine Type Communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including supporting (e.g., supporting only) certain bandwidths and/or limited bandwidths. MTC devices may include batteries with battery lives above a threshold (e.g., to maintain very long battery lives).

WLAN systems that can support multiple channels, and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include channels that can be designated as primary channels. 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 STAs from all STAs operating in the BSS (which support a minimum bandwidth mode of operation). In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only) 1MHz mode, the primary channel may be 1MHz wide, even though the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and/or other channel bandwidth modes of operation. The carrier sense and/or Network Allocation Vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because the STA is transmitting to the AP (only supporting 1MHz mode of operation), all available frequency bands may be considered busy even if most available frequency bands remain idle.

The available frequency band for 802.11ah in the united states is 902MHz to 928MHz. In 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.

Fig. 1D is a system diagram illustrating a RAN 104 and a CN 106 according to an embodiment. As noted above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. RAN 104 may also communicate with CN 106.

RAN 104 may include gnbs 180a, 180b, 180c, although it will be appreciated that RAN 104 may include any number of gnbs while remaining consistent with an embodiment. Each of the gnbs 180a, 180b, 180c may include one or more transceivers to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the gnbs 180a, 180b, 180c may implement MIMO technology. For example, the gnbs 180a, 108b may utilize beamforming to transmit signals to and/or receive signals from the gnbs 180a, 180b, 180 c. Thus, the gNB 180a may use multiple antennas to transmit wireless signals to and/or receive wireless signals from the WTRU 102a, for example. In an embodiment, the gnbs 180a, 180b, 180c may implement carrier aggregation techniques. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on the unlicensed spectrum while the remaining component carriers may be on the licensed spectrum. In embodiments, the gnbs 180a, 180b, 180c may implement coordinated multipoint (CoMP) techniques. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and/or gNB 180 c).

The WTRUs 102a, 102b, 102c may communicate with the gnbs 180a, 180b, 180c using transmissions associated with the scalable parameter sets. For example, the OFDM symbol interval and/or OFDM subcarrier interval may vary from transmission to transmission, from cell to cell, and/or from part of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gnbs 180a, 180b, 180c using various or scalable length subframes or Transmission Time Intervals (TTIs) (e.g., including different numbers of OFDM symbols and/or continuously varying absolute time lengths).

The gnbs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in an independent configuration and/or in a non-independent configuration. In a standalone configuration, the WTRUs 102a, 102B, 102c may communicate with the gnbs 180a, 180B, 180c while also not accessing other RANs (e.g., such as the enode bs 160a, 160B, 160 c). In an independent configuration, the WTRUs 102a, 102b, 102c may use one or more of the gnbs 180a, 180b, 180c as mobility anchor points. In an independent configuration, the WTRUs 102a, 102b, 102c may use signals in unlicensed frequency bands to communicate with the gnbs 180a, 180b, 180 c. In a non-standalone configuration, the WTRUs 102a, 102B, 102c may communicate or connect with the gnbs 180a, 180B, 180c, while also communicating or connecting with other RANs (such as the enode bs 160a, 160B, 160 c). For example, the WTRUs 102a, 102B, 102c may implement DC principles to communicate with one or more gnbs 180a, 180B, 180c and one or more enodebs 160a, 160B, 160c substantially simultaneously. In a non-standalone configuration, the enode bs 160a, 160B, 160c may serve as mobility anchors for the WTRUs 102a, 102B, 102c, and the gnbs 180a, 180B, 180c may provide additional coverage and/or throughput for serving the WTRUs 102a, 102B, 102 c.

Each of the gnbs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and/or DL, support of network slices, interworking between DC, NR, and E-UTRA, routing of user plane data towards User Plane Functions (UPFs) 184a, 184b, routing of control plane information towards access and mobility management functions (AMFs) 182a, 182b, and so on. As shown in fig. 1D, gnbs 180a, 180b, 180c may communicate with each other through an Xn interface.

The CN 106 shown in fig. 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. Although the foregoing elements are depicted as part of the CN 106, it should be appreciated that any of these elements may be owned and/or operated by entities other than the CN operator.

The AMFs 182a, 182b may be connected to one or more of the gnbs 180a, 180b, 180c in the RAN 104 via an N2 interface and may function as control nodes. For example, the AMFs 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slices (e.g., handling of different Protocol Data Unit (PDU) sessions with different requirements), selection of a particular SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMFs 182a, 182b may use network slices to customize CN support for the WTRUs 102a, 102b, 102c based on the type of service used by the WTRUs 102a, 102b, 102 c. For example, different network slices may be established for different use cases, such as services relying on ultra high reliability low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, services for MTC access, and so on. The AMFs 182a, 182b may provide control plane functionality for switching between the RAN 104 and other RANs (not shown) employing other radio technologies, such as LTE, LTE-A, LTE-a Pro, and/or non-3 GPP access technologies, such as WiFi.

The SMFs 183a, 183b may be connected to AMFs 182a, 182b in the CN 106 via an N11 interface. The SMFs 183a, 183b may also be connected to UPFs 184a, 184b in the CN 106 via an N4 interface. SMFs 183a, 183b may select and control UPFs 184a, 184b and configure traffic routing through UPFs 184a, 184b. The SMFs 183a, 183b may perform other functions such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, ethernet-based, etc.

The UPFs 184a, 184b may be connected to one or more of the gnbs 180a, 180b, 180c in the RAN 104 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to a packet-switched network, such as the internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. UPFs 184, 184b may perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multi-host PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, and the like.

The CN 106 may facilitate communications with other networks. For example, the CN 106 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and/or wireless networks owned and/or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may connect to the DNs 185a, 185b through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the local DNs 185a, 185b.

In view of fig. 1A-1D and the corresponding descriptions of fig. 1A-1D, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more emulation devices (not shown): the WTRUs 102a-d, base stations 114a-B, eNodeBs 160a-160c, MME 162, SGW 164, PGW 166, gNB 180a-180c, AMFs 182a-182B, UPFs 184a-184B, SMFs 183a-183B, DNs 185a-185B, and/or any other devices described herein. The emulated device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation device may be used to test other devices and/or analog network and/or WTRU functions.

The simulation device may be designed to enable one or more tests of other devices in a laboratory environment and/or an operator network environment. For example, the one or more emulation devices can perform one or more or all of the functions while being fully or partially implemented and/or deployed as part of a wired and/or wireless communication network in order to test other devices within the communication network. The one or more emulation devices can perform one or more functions or all functions while being temporarily implemented/deployed as part of a wired and/or wireless communication network. The emulation device can be directly coupled to another device for testing purposes and/or perform testing using over-the-air wireless communications.

The one or more emulation devices can perform one or more (including all) functions while not being implemented/deployed as part of a wired and/or wireless communication network. For example, the simulation device may be used in a test laboratory and/or a test scenario in a non-deployed (e.g., test) wired and/or wireless communication network in order to enable testing of one or more components. The one or more simulation 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.

The IEEE 802.11 Extremely High Throughput (EHT) study group was established at month 9 of 2018. EHT development may provide a basis for the next major revision to the IEEE 802.11 standard following the 802.11 ax. The EHT research group explores the possibility of further increasing peak throughput and improving the efficiency of IEEE 802.11 networks. After the EHT study group is established, an 802.11be task group is also established to provide the 802.11EHT specification. The use cases and applications that are addressed include high throughput and low latency applications such as video over WLAN; augmented Reality (AR); virtual Reality (VR). The list of features discussed by EHT SG and 802.11be to achieve the goals of increasing peak throughput and improving efficiency include: multiple APs; multi-band/multi-link; a 320MHz bandwidth; 16 spatial streams; HARQ; an AP coordinate; and new designs for 6GHz channel access. The IEEE standards committee approves the IEEE 802.11be Task Group (TG) based on a Project Authorization Request (PAR) and a standard development Criteria (CSD) developed by the EHT research group.

Additional details regarding multi-AP transmissions according to the 802.11be standard are described herein. Basically, the multi-AP operation includes STAs that receive transmissions from multiple APs. The multi-AP transmission may be a MU transmission such that multiple transmissions are received from each AP simultaneously.

Coordinated multiple AP (C-MAP) transmissions may be supported in 802.11 be. Such a C-MAP transmission scheme may include: coordinated multi-AP OFDMA; coordinated multi-AP TDMA; coordinated multi-AP spatial reuse; coordinated beamforming/nulling; and joint transmission.

In the context of a coordinated multi-AP system, several terms are defined and used herein. For example, shared APs may refer to EHT APs or EHT AP sets that acquire transmission opportunities (TXOPs) and initiate multi-AP coordination. The shared AP is also referred to as a coordinator AP. A shared AP refers to an EHT AP or set of EHT APs coordinated by the shared AP for multi-AP transmissions. AP candidate sets refer to APs or AP sets that initiate or participate in multi-AP coordination.

For example, IEEE 802.11be may support mechanisms to determine whether an AP is part of an AP candidate set and may participate in coordinated multi-AP transmissions initiated by a shared AP as a shared AP. A procedure may be required for an AP to define the frequency/time resources that share its acquired TXOPs with the AP set. An AP that intends to use a resource (i.e., frequency or time) shared by another AP may be able to indicate its resource needs to the AP that shares the resource. 11be may support coordinated OFDMA and in coordinated OFDMA, DL OFDMA and its corresponding UL OFDMA acknowledgement are allowed.

Additional details regarding multi-AP channel sounding according to the 802.11be standard are described herein. Channel sounding according to the 802.11n and 802.11ac standards may be performed using two different schemes, commonly referred to as explicit channel sounding or implicit channel sounding. In explicit channel sounding, the AP may transmit NDP to STAs with preambles that allow the STAs to measure their own channels and send CSI feedback to the AP. In implicit channel sounding, an STA may send an NDP and an AP may measure the channel of the STA (assuming the channel is peer-to-peer).

802.11be may support the maximum number (e.g., 16) of spatial streams for SU-MIMO and for MU-MIMO. The maximum number of spatial streams allocated to each MU-MIMO scheduled non-AP STA may be limited to, for example, 4. The maximum number of users that can spatially multiplex DL transmissions may be, for example, 8 per RU.

802.11be may support two or more channel sounding modes in a multi-AP system. Two of these channel sounding modes may be sequential sounding and joint sounding. In sequential probing, each AP may independently transmit NDPs, with each AP having no overlapping probing periods. In other words, each AP performs probing in its own time period, and these probing time periods may then be referred to as sequential. In joint sounding, where the AP has less than or equal to a total of 8 antennas active on all LTF tones, and an 802.11ax P matrix is used across OFDM symbols. In other words, joint sounding in a multi-AP system includes APs with 8 or fewer antennas, all antennas may be made active on all LTF tones and an 802.11ax P matrix is used to transmit/receive sounding signals.

In other words, the four-step procedure may be used to obtain sounding feedback from STAs in BSSs operated by the AP and STAs in the overlapping BSSs that are not associated with the same AP.

Fig. 2 shows a signal flow diagram illustrating an example of both a sequential channel sounding procedure and a joint channel sounding procedure performed in a multi-AP system. To begin either process, in one example, the shared AP (AP 1) transmits a multi-AP NDPA, and then each AP (AP 1, AP2, and AP 3) in the coordination group may transmit an NDPA. In a sequential sounding scheme, each AP (AP 1, AP2, and AP 3) in the coordination group may transmit NDPs (i.e., time multiplexed) to all STAs in the coordination group in different non-overlapping times. In this scenario, each NDP may be separated by a short inter-frame space (SIFS) time interval. In a joint sounding scheme, coordinated APs (AP 1, AP2, and AP 3) may each transmit NDPs simultaneously, with different Long Training Field (LTF) tones spanning the entire bandwidth and being spatially multiplexed or using orthogonal codes. Otherwise, each AP may transmit its respective LTF tone only on selected tones such that there is no overlap of tones between APs. The STAs (STA 1, STA2, and STA 3) that receive the NDP frame may then determine CSI or CQI and transmit this information back to one of the APs in the coordination group (AP 1, AP2, or AP 3).

When an STA (such as STA1, STA2, or STA3 shown in fig. 2) receives the NDP, it may measure a channel and prepare a CSI feedback report. At least three different ways may be used to collect CSI from STAs. In some cases, each AP may collect all CSI including feedback of in-BSS and OBSS STAs. In some cases, each AP may collect CSI from only its associated STAs. And in some cases, the sharing AP (AP 1 in fig. 2) may collect CSI for all shared APs in the coordination group.

Various challenges exist in channel sounding in a multi-AP system. One such problem is that STAs involved in the sounding process may not be able to listen to the coordinator AP.

Other challenges may relate to synchronization of APs in a multi-AP coordination set; overhead, complexity, and performance of different probing schemes; variants of NDP transmission in explicit and implicit probing; and feedback collection and reduction.

The 802.11be TG has agreed to keep the structure of the NDP announcement (NDPA) similar to that of the 802.11ax NDPA, as shown in fig. 3. However, the STA information field depicted in fig. 3 is changed to accommodate the new features of the 802.11be EHT.

As mentioned, fig. 3 shows an example of a HE NDP announcement frame format conforming to 802.11 ax. Those skilled in the art will recognize the 802.11ax NDP announcement frame format. The frame includes a frame control field, a duration field, a Receiver Address (RA) field, and a Transmitter Address (TA) field in a MAC header. The sounding dialog token is followed by some number of STA info fields, shown in fig. 3 as STA info 1 through STA info n. The Frame Check Sequence (FCS) is the last field of a frame.

The STA info 1 field shown in fig. 3 is shown in more detail in fig. 4. Fig. 4 shows an example of a STA information field format in an EHT NDP announcement frame. The STA information field includes an Association Identifier (AID) field, a partial Bandwidth (BW) information field, reserved bits, nc fields, feedback types and Ng fields, disambiguation bits, codebook size bits, and reserved fields.

Fig. 5 shows an example of a trigger frame format. The trigger frame includes a frame control field, a duration field, an RA field, and a TA field in a MAC header of the trigger frame. The trigger frame also includes a variable length public information field, a variable length user information list field, a variable length padding field, and a final FCS field. The trigger frame may be used to allocate resources to one or more STAs and trigger single-user access or multi-user access in the uplink. In a manner that complies with the 802.11be standard, new variants of the user information field may be supported and special user information fields may be added after the public information field. Both enhancements may allow for a unified triggering scheme for both HE (802.11 ax compliant) and EHT (802.11 be compliant) devices.

Fig. 6 shows an example of an EHT user information field format. The EHT user information fields may include an AID12 field, a Resource Unit (RU) allocation field, a UL FEC coding type field, a UL EHT Modulation and Coding Scheme (MCS) field, reserved bits, a Spatial Stream (SS) allocation/random access RU (RA-RU) information field, a UL target received power field, a PS160 field, and a variable length trigger related user information field. The content of the trigger related user information is based on which type of trigger frame carries the EHT user information field. For example, a Beamforming Feedback Report Poll (BFRP) trigger frame may have trigger-related user information fields that carry some information, while a generic trigger frame may have trigger-related user information fields that carry other, different information.

Fig. 7 shows an example of an EHT special user information field format. The EHT special user information fields may include an AID12 field, a physical layer (PHY) version ID field, an UL bandwidth extension field, a spatial reuse 1 field, a spatial reuse 2 field, a U-SI ignore and validate field, a reserved field, and a variable length trigger related user information field. The content of the trigger related user information is based on which type of trigger frame carries the EHT user information field. For example, a Beamforming Feedback Report Poll (BFRP) trigger frame may have trigger-related user information fields that carry some information, while a generic trigger frame may have trigger-related user information fields that carry other, different information.

In the 802.11be system, the first problem exists in collecting CSI feedback from OBSS STAs. In MAP sounding, each AP involved in the sounding may collect CSI feedback from its associated STA and OBSS STA (i.e., STA associated with another AP). Feedback collection from OBSS STAs may be an open problem, especially when the OBSS STAs are at the edge of coverage. For example, an OBSS STA may listen for DL transmissions from the coordinating AP, but UL transmissions from the STA may not reach the coordinating AP well due to insufficient transmit power and/or insufficient number of transmit antennas.

A second problem exists in requesting CSI feedback from OBSS STAs using BFRP trigger frames. MAP sounding may involve collecting CSI feedback from associated STAs and from unassociated STAs to perform coordinated transmissions (e.g., coordinated Beamforming (CBF) and Joint Transmission (JTX)). Existing BFRP trigger frames may not support requesting CSI feedback from unassociated OBSS STAs. Several problems exist and must be addressed to enable MAP communication, including an indication that a BFRP trigger frame is triggering an unassociated STA from an OBSS, an identification of an unassociated OBSS STA, and a potential AID collision that several STAs from different BSSs may have the same AID.

A third problem exists in the optimization of the channel sounding feedback process. A beamforming transmitting end (beam former) and a beamforming receiving end (beam former) may experience different interference levels on different sub-channels. This problem may be more severe when preamble puncturing is allowed in most transmissions. For example, the AP may acquire a 320MHz channel and request the STA to feedback its CSI/CQI on the 320MHz channel. On the STA side, one or more sub-channels may experience heavier interference than the remaining sub-channels. The STA may not be able to obtain good channel measurements on severely interfered sub-channels. Thus, CSI/CQI feedback on the affected sub-channels may be unavailable or misleading.

Another problem exists in controlling the behavior of STAs designed for different standard versions. In a Signal (SIG) field defined in the IEEE 802.11 standard, some bits may be reserved without specific values for future versions. However, when future versions (assuming R2) of the device are available, the absence of particular values in the current version (assuming R1) creates at least two problems. One problem is the unpredictable behavior of R2 feature enabled devices operating in an R1 feature only BSS. Another problem is the ability to disable all R2 related features (not just a subset of R2 features) of the R2 feature enabled devices when needed.

Various solutions for solving some of the above problems using the above-described EHT user information field and/or EHT specific user information field will now be described. Some embodiments may provide a method of collecting CSI feedback from OBSS STAs and may address at least the problems discussed in the first problem introduced above.

In a MAP scenario, all STAs may not be able to hear all participating APs. Alternatively or additionally, the STA may listen for DL transmissions from one or more participating APs, but UL transmissions from one or more STAs may not reach one or more participating APs. Device-to-device (D2D) transmissions between STAs may help relay information to the AP.

FIG. 8 "error-! No reference source was found. "AND" error! No reference source was found. "fig. 9 illustrates an exemplary process for collecting CSI feedback from OBSS STAs. As shown in fig. 8, the sharing AP1 transmits a trigger frame to the associated STA11 and STA 12. Note that the first digit in the names of STA11 and STA12 indicates that STA is being associated with AP 1. Similarly, STA21 and STA22 are associated with AP2 and are considered OBSS STAs with respect to shared AP 1. AP1 and AP2 form a MAP group (or MAP coordination set), and AP1 is a shared AP and AP2 is a shared AP. NDPA/NDP sounding exchanges may be performed and these processes may focus on collecting CSI/CQI feedback.

With continued reference to fig. 8, the sharing AP (AP 1) may attempt to acquire Channel State Information (CSI) between itself and OBSS STAs or unassociated STAs (e.g., STA21 and STA 22). Instead of communicating directly with OBSS STAs, AP1 may require its associated STAs (e.g., STA11 and STA 12) to relay CSI information. AP1 may transmit a trigger frame to allocate one or more peer-to-peer (P2P) -triggered TXOP sharing Service Periods (SPs) to one or more associated STAs (STA 11 and STA 12). In general, the triggered TXOP sharing SP may be a period within the TXOP acquired by the AP (using a trigger frame) that may be used by the STA11 and STA12 to perform peer-to-peer transmissions, such as channel sounding relay procedures with other STAs including associated STAs and unassociated STAs. In the example shown in fig. 8, a peer MAP probe reporting procedure with OBSS/unassociated STAs (STA 21 and STA 22) is shown. This may be achieved by STA11 and STA12 transmitting peer BF poll frames to STA21 and STA22, respectively. STA21 may generate sounding feedback based on CSI measured between AP1 and STA21 in a previous sounding session. The STA22 may generate sounding feedback based on CSI measured between the AP1 and the STA22 in a previous sounding session. STA21 and STA22 may transmit CSI to STA11 and STA12, respectively. The sharing AP1 may transmit a BFRP trigger frame at the end of the triggered TXOP sharing SP to request aggregated feedback from its associated STAs (STA 11 and STA 12). In this way, the feedback STA21 and STA22 from the OBSS STA can be collected by sharing the AP 1.

In some embodiments, in a trigger frame or a special type of trigger frame, the sharing AP1 may include a user information field having an AID field corresponding to an associated STA (e.g., STA 11). The sharing AP1 may also allocate a duration for the triggered TXOP sharing SP. In some embodiments, the common information field, the special user information field, or one or more reserved bits in the user information field of the trigger frame may indicate that the user information field contains a time domain resource allocation. When one or more bits are set, then the RU allocation subfield may indicate the duration of the triggered TXOP sharing SP. Alternatively or additionally, other subfields (such as a UL FEC coding type subfield, and/or a UL MCS subfield, a UL DCM subfield, and/or a reserved subfield, and/or a UL target received power subfield, and/or an SS allocation/RA-RU subfield) may be diverted and used to indicate the duration of the TXOP sharing SP. In another embodiment, a combination of the above subfields may be used to indicate the duration of the triggered TXOP sharing SP.

In some embodiments, in a trigger frame, the sharing AP1 may include more than one user information field with AIDs corresponding to its associated STAs (e.g., STA11 and STA 12). The sharing AP1 may allocate a plurality of slots to STAs, and each slot may be assigned to one STA. In some embodiments, the common information field, the special user information field, or one or more reserved bits in the user information field of the trigger frame may indicate that the user information field may contain a time domain resource allocation. In some embodiments, each user information field in the trigger frame may indicate or carry the duration of the triggered TXOP sharing SP. The first trigger TXOP sharing SP may start after a SIFS duration after the end of the trigger frame. STAs corresponding to the kth user information field may be allocated to share SPs using the kth triggered TXOP. Each STA may need to decode all of the user information fields before its own user information field to determine the start time of its assigned SP. In some embodiments, each user information field may carry the start time and duration of the allocated triggered TXOP sharing SP. In some embodiments, the common duration subfield may be carried in a common information field or a special user information field. The common duration subfield may indicate the duration of each triggered TXOP sharing SP. For example, all triggered TXOP sharing SPs may have the same duration. In this way, a STA may need to check the ordering of its own user information fields to determine the start time of its triggered TXOP sharing SP.

In some embodiments, in a trigger frame, the sharing AP1 may include more than one user information field, each user information field including an AID corresponding to each of its associated STAs (e.g., STA11, STA 12). The sharing AP1 may allocate time-frequency resources to STAs. In some embodiments, the trigger frame may indicate that the allocated triggered TXOP sharing SP is used for P2P CSI/CQI exchange. In some embodiments, the trigger frame may indicate the initiator and/or responder of the triggered TXOP sharing SP.

As shown in fig. 8, STA11 and/or STA12 may transmit a beamforming report poll (BFRP) frame or a BFRP trigger frame to request CSI/CQI reports from another STA (i.e., STA21 and/or STA 22). If more than one STA shares the triggered TXOP sharing SP, the STAs may perform their transmissions using the allocated time-frequency resources.

As shown in fig. 8, after the triggered TXOP shares the SP, the sharing AP1 may regain ownership of the TXOP. Then, as described above, the shared AP1 transmits a BFRP trigger frame to trigger CQI/CSI reports from one or more STAs (i.e., STA11 and STA 12).

In some embodiments, the aggregate beamforming report may be transmitted to the sharing AP1 in response to a BFRP trigger frame sent by the sharing AP 1. The aggregate beamforming report may carry multiple pairs of CSI/CQI reports between the transmitter and the receiver. For example, as "error! No reference source was found. As shown in fig. 8, the report from STA11 may carry CSI information between AP1 and STA11 and CSI information between STA21 and AP1 (e.g., information obtained by STA11 during the triggered TXOP sharing SP).

In some embodiments, the a-MPDU may be used to carry CSI information between a plurality of pairs of transmitters and receivers. With the a-MPDU format, a MAC header may be carried in each MPDU. For MPDUs carrying channels between two STAs, some address fields in the MAC header may be used to carry the MAC addresses of the two STAs. In some examples, each MPDU may be a HE compressed beamforming/CQI action frame, which may carry CSI between a pair of transmitters and receivers (e.g., AP1 and STA 11). Some address fields in the MAC header of the MPDU may contain MAC addresses of AP1 and STA 11.

Referring to FIG. 9, an embodiment is shown in which the "error-! No reference source was found. "the STA11 and the STA12 share SPs with TXOPs triggered by different allocated frequency resource sharing. Accordingly, STA11 and STA12 can transmit to STA21 and STA22, respectively, on the allocated resources. STA21 and STA22 may respond with one or more CSI/CQI reports that include measurements performed when AP1 transmits NDP sounding frames. In this example, AP1 may allocate a triggered TXOP-sharing SP with STA11 and STA12 by exchanging a trigger frame and a CTS frame. The STA11 may generate a sounding report based on CSI measured between the AP2 and the STA11 in a previous sounding session. The STA12 may generate a sounding report based on CSI measured between the AP2 and the STA12 in a previous sounding session. STA11 and STA12 may transmit their BF report frames to STA21 and STA22, respectively, along with the prepared sounding report. The STA21 may generate a sounding report based on CSI measured between the AP1 and the STA21 in a previous sounding session. The STA22 may generate a sounding report based on CSI measured between the AP1 and the STA22 in a previous sounding session. STA21 and STA22 may transmit their BF report frames to STA11 and STA12, respectively, along with the prepared sounding report. After the triggered TXOP sharing SP, the sharing AP1 may regain ownership of the TXOP. The shared AP1 then transmits a BFRP trigger frame to trigger CQI/CSI reports from one or more STAs. In this example, upon receiving the BFRP trigger frame from AP1, STA11 and STA12 may transmit their aggregate CSI reports to AP1, and STA21 and STA22 may transmit their aggregate CSI reports to AP 2. The transmissions may be multiplexed in the time/frequency/space domain.

Fig. 10 provides an example of EHT/enhanced compression beamforming/CQI frame action field format. In some embodiments, there are newly defined enhanced compressed beamforming/CQI action frames, such as "error-! No reference source was found. "shown in fig. 10. The MAP extension field may be added to the action frame. The MAP extension field may carry MAP related information. For example, it may carry a beamforming receiver/beamforming sender ID subfield with a MAC address or compressed MAC address, or another type of ID for the beamforming receiver and beamforming sender associated with CSI/CQI. The presence of the MAP extension field and/or the beamforming receiver/beamforming sender ID subfield may be optional. In one of the mandatory fields, such as the enhanced MIMO control field, a bit may be used to indicate the presence of a MAP extension field.

Note that the above procedure can be extended to a single BSS case where all STAs are associated with a single AP. Some STAs may be at the edge of the BSS and they may use other STAs to relay CSI/CQI information to the AP. It is further noted that the SIFS described above between transmissions may be replaced with other inter-frame intervals. The disclosed trigger frame design may be used in any situation where a triggered TXOP sharing SP may be used.

In other embodiments, the B25 of the EHT variant user information field in the trigger frame may be used to request CSI feedback from the OBSS STA using the BFRP trigger frame. The EHT user information field is shown in fig. 6. The reserved bit 25 (i.e., B25) may be renamed to an (in-BSS/OBSS) subfield and used to indicate that the user information is for a STA associated with another AP in the coordination group. For example, B25 may be set equal to 0 to indicate that the STA is an in-BSS STA. B25 may be set equal to 1 to indicate that the STA is an OBSS STA or vice versa. It should be noted that B25 may be just one example of a bit range for carrying in-BSS/OBSS bits; however, bits in other locations may be used for the same purpose.

In some embodiments, an indication may be carried in a special user information field and/or a common information field of the trigger frame that indicates whether the trigger frame is used to request transmission by STAs associated with the shared AP.

Fig. 11 shows an example of trigger related user information subfields in a BFRP trigger frame. In some examples, the trigger related user information subfield of the BFRP trigger frame indicates that the associated user information field is designated for an in-BSS STA or an OBSS STA, such as "error-! No reference source was found. "depicted in fig. 11. In one embodiment, the first bit triggering the relevant user information subfield may be named in-BSS/OBSS, where a value of 0 indicates in-BSS STA and a value of 1 indicates OBSS STA, or vice versa. The remaining bits of the subfield may be used to signal an APID, which may be an ID associated with the AP with which the STA is associated. Examples of APIDs may include the least significant 7 bits of AID11 assigned to each AP in a multi-AP coordination group; the entire AID11 assigned to each AP in the multi-AP coordination group; a portion of the compressed BSSID of the AP with which the STA is associated; or the entire compressed BSSID of the AP with which the STA is associated.

In some embodiments, reserved bits of the EHT special user information field (e.g., B37-B39 of the EHT special user information field shown in fig. 7 described in the preceding paragraph) may be used to signal the number of STAs from the OBSS that are triggered in the trigger frame. In this embodiment, the user information field of the OBSS STA may be located directly after the special user information field. In other words, the EHT special user information field is the first field after the common information field in the trigger frame.

In some embodiments, the trigger related user information subfield of the special user information field may be used to signal a mapping of the subsequent list of user information indicating which STA or STAs are in-BSS STAs and which STA or STAs are OBSS STAs. The reserved bits (B37-B39) in the special user information field as shown in fig. 7 described in the above paragraph may indicate the number of trigger-related user information subfields in the special user information field. The ordering of the trigger related user information subfields may indicate a mapping to a user information subfield subsequent to a particular user information field, wherein each trigger related user information subfield may be mapped to a user information subfield in the same order. Each trigger related user information subfield may include a bit to indicate that the subfield is mapped to an in-BSS or OBSS STA, and the remaining bits may be used to include an APID.

Fig. 12 shows a new special user information field format that may be included in a trigger frame, as discussed above. For example, the new special user information field may be placed just after the existing special user information field. The new special user information field may use another special ID to indicate that it is used for multi-AP triggering purposes. The subfields of the new special user information field may be defined as follows. The AID12 may be set to a special ID. The number of triggered OBSS users field may indicate how many OBSS users were triggered in the current trigger frame. This is followed by a plurality of user pointer subfields, where each user pointer subfield may point to one of the user information fields that follows the new special user information field. In some embodiments, the user pointer subfield may include a subfield that explicitly indicates the ordering of the user information field in the trigger frame. In some embodiments, the user pointer sub-fields may have the same order of user information fields, where all user information fields of the OBSS STA may, for example, be located just after the new special user information field. In such cases, the ordering may be indicated implicitly. Further, the user pointer subfield may include an APID associated with the OBSS STA.

In some embodiments, a trigger frame (e.g., a BFRP trigger frame) may be used to trigger a feedback transmission from a STA associated with another AP, such as an OBSS AP. For example, when a first member AP in the multi-AP set wishes to request sounding feedback from an STA associated with a second member AP, the requesting AP (first AP) may send a trigger frame, e.g., a BFRP trigger frame, that includes a Receiver Address (RA) set to the BSSID of the BSS of the second AP. The BFRP trigger frame may include an indication that the BFRP trigger frame targets STAs associated with the BSS of the second AP. For example, such an indication may be a group bit in the RA MAC address. Alternatively or additionally, the indication may be one or more bits contained in the trigger frame, such as one or more bits contained in a common information field of the trigger frame.

In some embodiments, a trigger frame (e.g., a BFRP trigger frame) may contain one or more new special user information fields. The new special user information field or user information field may contain an ID or AID associated with an AP of a multiple AP set (MPS). The user information field following the special user information field may contain an AID that represents the STA associated with the member AP. The AID of the STA used in the user information field may be the AID assigned to the STA by the member AP with which the STA is associated. The additional special user information field or user information field may contain an ID or AID of another member AP each representing the MPS. The user information field following the special user information field or user information field of the second member AP representing the MPS may contain an ID or AID for the STA associated with the second member AP. The ID or AID may be an AID assigned to the STA by the second member AP.

In some embodiments, an AP may use a trigger frame (e.g., a BFRP trigger frame) to trigger feedback transmissions from STAs associated with one or more APs, such as one or more member APs that may belong to the same MPS. The RA address of the trigger frame may be set to a MAC address representing the MPS.

In some embodiments, a trigger frame (e.g., a BFRP trigger frame) may contain one or more special user information fields. The special user information field may contain an ID or AID that represents the MPS. The user information field following the special user information field may contain an AID representing one or more STAs belonging to the MPS.

In some embodiments, a trigger frame (e.g., a BFRP trigger frame) may use one or more random access RUs/RRUs to request feedback transmissions from the MPS or from a particular BSS belonging to one member AP of the MPS.

The coordinator member AP of the MPS may advertise one or more member APs included in a multi-AP set (MPS). The coordinator member AP may indicate one or more member APs for which its associated STA should receive the probe frame, calculate feedback, and respond to the trigger frame or BFRP trigger frame to provide the probe feedback.

In addition, when a STA is requested by a member AP in the same MPS by triggering (e.g., by BFRP trigger frame), the member AP may advertise one or more IDs or AIDs to be used for each of its associated STAs.

STAs associated with a member AP belonging to the MPS may respond to a trigger frame (e.g., a BFRP trigger frame) transmitted by a member AP of the same MPS if one or more or a subset or combination of the following conditions are met. For example, a trigger frame or BFRP trigger frame may be transmitted by a member AP belonging to the same MPS, which may have been advertised by an AP associated with the STA. The trigger frame or BFRP trigger frame may be transmitted with an RA address representing a BSS (e.g., BSSID) to which the STA belongs, and/or the trigger frame may contain an indication that the trigger frame is for an STA belonging to the BSS.

The trigger frame or BFRP trigger frame may contain a new special user information field that may contain an ID or AID that indicates the BSS to which the STA belongs or the AP with which the STA is associated. Another condition may be satisfied when an ID or AID contained in the user information field matches an ID or AID belonging to a STA that may be assigned to the STA by a member AP. The ID or AID may be assigned or indicated as a regular AID or as an ID or AID that should be used when requested by a trigger or BFRP trigger frame transmitted by a member AP of the MPS to which the AP to which the STA is associated belongs, or addressed to the BSS, or after a new special user information field containing an ID or AID that indicates the BSS to which the STA belongs or the AP with which the STA is associated.

Another condition may be met when a trigger frame or BFRP trigger frame may indicate a random access RU/MRU when requested by the trigger or BFRP frame (which is transmitted by a member AP of the MPS to which the STA's associated AP belongs), or addressed to the BSS, or after a special user information field containing an ID or AID indicating the BSS to which the STA belongs or the AP with which the STA is associated.

The STA may respond to the trigger or BFRP trigger frame with a feedback transmission, such as a beamforming report, a compressed beamforming report, CSI, MIMO feedback, or other type of feedback frame, using the allocated RU/MRU as indicated in the trigger or BFRP trigger frame, or using one or more of a UORA mechanism and an assigned random access RU/RRU.

It is desirable to optimize the channel feedback process. The solutions described in the following embodiments may at least solve the problems discussed above. In a beamforming feedback frame, the STA may transmit a measured channel bitmap field, which may indicate CSI/CQI information on certain subchannels. The measured channel bitmap field may be carried in an EHT/enhanced compressed beamforming/CQI action frame. In some embodiments, the EHT/enhanced MIMO control field may carry a measured channel bitmap field.

Fig. 13 shows an example of a modified EHT/enhanced MIMO control field. The EHT/enhanced MIMO control field may include an Nc index field, an Nr index field, a Bandwidth (BW) field, a packet field, a feedback type field, a first reserved field, a remaining feedback segment field, a first feedback segment field, a partial FB BW information field, a sounding dialog token number field, a codebook information field, and/or a second reserved field. In some embodiments, a partial BW information subfield may be used to carry the measurement channel bitmap field described above. In some embodiments, the subfields may be renamed to partial FB BW information, as shown in fig. 13. In some embodiments, multiple bits (e.g., 9 bits) may be used for the subfield. Bit 0 (B0) may indicate resolution. For example, when the BW subfield is set to 0 to 3 (or BW is equal to or less than 160 MHz), then B0 may be set to 0 and the measured channel bitmap resolution is 20MHz. The measured channel bitmap may have, for example, 8 bits, and each bit may indicate whether CSI/CQI on the corresponding 20MHz subchannel is included in the report. When the BW subfield is set to 4 (or BW is equal to 320 MHz), then B0 may be set to 1 and the measured channel bitmap resolution may be 40MHz. The measured channel bitmap may have 8 bits, and each bit may indicate whether CSI/CQI on the corresponding 40MHz subchannel is included in the report. In some approaches, multiple bits (e.g., 8 bits) may be used for the measured channel bitmap, and resolution may be implicitly signaled by the BW subfield.

In other embodiments, a probing procedure with an enhanced partial FB BW information field may be utilized. For example, the beamforming sender may transmit an NDPA frame to one or more beamforming receivers to begin the sounding process. The beamforming receiver may then detect the NDPA frame addressed to it and prepare for the upcoming probe. The beamforming sender may then transmit one or more NDP frames after the NDPA frame. The beamforming sender may transmit a BFRP trigger frame to trigger BF reports from one or more beamforming receivers.

In the case where the beamforming receiver may experience relatively high interference on one or more of the subchannels on which the sounding/NDP frame is transmitted, or the beamforming receiver may have NAV settings on one or more of the subchannels, for example, the NDP frame may be transmitted on subchannels 1-4 and the beamforming receiver may detect that subchannel 3 may be busy, a solution is needed. The beamforming receiver may include a partial FB BW information field in the enhanced MIMO control field in the compressed BF/CQI frame. The partial FB BW information field may indicate on which sub-channel no BF/CQI report is present. In the above example, there is no BF/CQI report on subchannel 3 because the subchannel is determined to be busy based on the NAV setting.

Reports relating to the subchannels identified in the partial FB BW information field may not be included in the compressed beamforming report field and/or the MU-specific beamforming report field and/or the CQI report field. In the above example, the report related to subchannel 3 may not be included.

In further embodiments, to address the above-described issues with respect to different standard versions, one solution may be to set 1 bit or several bits in the reserved bits for indicating the version or versions that the device is capable of supporting. Other reserved bits may be used for other purposes of version 1, such as PAPR (peak to average power ratio) of the control signal field, or some R1 specific features (i.e., features for R1 devices only). If these bits are used to control the PAPR or other purposes of the transmission signal, they may be different for different channel bandwidths and/or sub-channel/preamble puncturing patterns, and/or MCS, and/or guard intervals.

In another embodiment, there are a total of N reserved bits. For example, one bit may be used to indicate whether a device is capable of operating according to version 1. If the bit is set to indicate version 1, the remaining N-1 reserved bits may be used to indicate any sequence to reduce PAPR, and the receiver may ignore the N-1 reserved bits. If the bit is set to indicate version 2 or an updated version, the remaining N-1 reserved bits may be used to indicate the characteristics of version 2 or an updated version. In this case, the version 1 receiver may ignore the N-1 reserved bits, but the version 2 receiver may understand its meaning.

In summary, referring to fig. 14, two embodiments are disclosed herein that support feedback from OBSS STAs in a multi-AP system. The trigger frame shown in fig. 14 is the same trigger frame shown and described in fig. 5. The trigger frame may be a BFRP trigger frame. In some embodiments described above, they are generally referred to as "design 1", with the user information field described above with reference to fig. 6 appearing after the common information field of the trigger frame. In the variable length trigger related user information field described with reference to fig. 11, the user information field includes an indication of whether the STA addressed in the user information field is associated with an in-BSS or an OBSS, and an APID identifying the AP to which the STA addressed in the user information field is associated. An STA that has a matching AID for the user information field and whose associated AP's APID matches the APID in the trigger related user information field may generate feedback and transmit the feedback to the AP that sent the trigger frame. In "design 2", the new special user information field occurs after the common information field of the trigger frame, as described above in connection with fig. 12. The new special user information field includes one or more user pointer fields, one for each user information field that appears in the trigger frame. Each user pointer field includes an ordering field and an APID field that indicate the order of the user information fields in the user information list. The STA having the corresponding APID in the special user information field may find the user information field in the user information list in the order specified by the ordering subfield. If the STA AID matches the AID in the user information field, the STA may generate feedback and transmit the feedback to the AP that sent the trigger frame. In two of these designs, the STA may be directed to transmit feedback to the AP that the STA is not associated with.

Although the features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with other features and elements. Furthermore, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer readable medium for execution by a computer or processor. Examples of computer readable media include electronic signals (transmitted over a wired or wireless connection) 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 the software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

While the solutions described herein contemplate 802.11 specific protocols, it should be appreciated that the solutions described herein are not limited to this scenario and are applicable to other wireless systems as well. Although SIFS may be used to represent various inter-frame intervals in examples of designs and processes, all other inter-frame intervals such as RIFS, AIFS, DIFS or other time intervals may be applied to the same solution. Although four RBs per triggered TXOP are shown as an example in some figures, the number of RBs/channels and bandwidths actually used may be different. For example, while a particular bit may be used to signal in-BSS/OBSS, other bits may be used to signal this information.

Claims

1. A Station (STA) associated with a first Access Point (AP) that is a member of a set of multiple APs, the STA comprising:

a transceiver configured to receive a trigger frame from a second AP that is also a member of the multi-AP set, wherein the STA is not associated with the second AP, the trigger frame including an Association Identifier (AID) related to an association between the STA and the first AP and an AP identifier (APID) of the first AP; and is also provided with

The transceiver is further configured to transmit a feedback message to the second AP, the feedback message including information indicating a channel quality of a communication channel between the STA and the second AP.

2. The STA of claim 1, further comprising:

a processor configured to determine that the AID included in the trigger frame corresponds to a stored AID related to the association between the STA and the first AP, determine that the APID included in the trigger frame corresponds to an APID of the first AP, and generate the feedback message.

3. The STA of claim 2, wherein the feedback message is a beamforming report.

4. The STA of claim 2, wherein the feedback message includes Channel Quality Information (CQI).

5. The STA of claim 1, wherein the second AP is associated with an Overlapping Basic Service Set (OBSS) AP.

6. The STA of claim 1, wherein the trigger frame is a beamforming report poll (BFRP) trigger frame.

7. The STA of claim 6, wherein the trigger frame comprises a user information field including the AID, and the user information field comprises a trigger related user information field including an Overlapping Basic Service Set (OBSS) indicator and the APID of the first AP.

8. The STA of claim 7, wherein the OBSS indicator indicates that the APID is an OBSS AP.

9. The STA of claim 6, wherein the trigger frame comprises a new special user information field comprising a user pointer field associated with a corresponding user information field, wherein the user pointer field comprises the APID and the corresponding user information field comprises the AID.

10. A method for use in a Station (STA) associated with a first Access Point (AP) that is a member of a set of multiple APs, the method comprising:

receiving a trigger frame from a second AP that is also a member of the multi-AP set, wherein the STA is not associated with the second AP, the trigger frame including an Association Identifier (AID) related to an association between the STA and the first AP and an AP identifier (APID) of the first AP; and

And transmitting a feedback message to the second AP, the feedback message including information indicating a channel quality of a communication channel between the STA and the second AP.

11. The method of claim 10, further comprising:

determining that the AID included in the trigger frame corresponds to a stored AID related to the association between the STA and the first AP;

determining that the APID included in the trigger frame corresponds to an APID of the first AP; and

and generating the feedback message.

12. The STA of claim 11, wherein the feedback message is a beamforming report.

13. The STA of claim 1, wherein the feedback message includes Channel Quality Information (CQI).

14. The STA of claim 10, wherein the second AP is associated with an Overlapping Basic Service Set (OBSS) AP.

15. The STA of claim 10, wherein the trigger frame is a beamforming report poll (BFRP) trigger frame.

16. The STA of claim 15, wherein the trigger frame comprises a user information field including the AID, and the user information field comprises a trigger related user information field including an Overlapping Basic Service Set (OBSS) indicator and the APID of the first AP.

17. The STA of claim 16, wherein the OBSS indicator indicates that the APID is an OBSS AP.

18. The STA of claim 15, wherein the trigger frame comprises a new special user information field comprising a user pointer field associated with a corresponding user information field, wherein the user pointer field comprises the APID and the corresponding user information field comprises the AID.