Non-primary channel access (NPCA) channel switching decision making process based on network allocation vector (NAV) status

Abstract

Disclosed herein is a method performed by a non-access point station (non-AP STA) that belongs to a basic service set (BSS) to perform non-primary channel access (NPCA). The non-AP STA may be capable of maintaining capable of maintaining an intra-basic service set (intra-BSS) network allocation vector (NAV) and a basic NAV. The method includes overhearing a first overlapping basic service set (OBSS) physical layer protocol data unit (PPDU) in a primary channel of the BSS and switching from operating in the primary channel of the BSS to operating in a NPCA primary channel of the BSS in response to overhearing the first OBSS PPDU despite the basic NAV being active.

Description

SPECIFICATIONNON-PRIMARY CHANNEL ACCESS (NPCA) CHANNEL SWITCHING DECISION MAKING PROCESS BASED ON NETWORK ALLOCATION VECTOR (NAV) STATUSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 790,630, filed April 17, 2025, titled “Method for determining NPCA operation based on the configured NAV (Network Allocation Vector)”, which is hereby incorporated by reference.TECHNICAL FIELD

[0002] The present disclosure generally relates to wireless communications, and more specifically, relates to a non-primary channel access (NPCA) channel switching decision making process based on network allocation vector (NAV) status.BACKGROUND

[0003] Institute of Electrical and Electronics Engineers (IEEE) 802.11 is a set of standards for implementing wireless local area network communication in various frequencies, including but not limited to the 2.4 gigahertz (GHz), 5 GHz, 6 GHz, and 60 GHz bands. These standards define the protocols that enable Wi-Fi devices to communicate with each other. TheIEEE 802.11 family of standards has evolved over time to accommodate higher data rates, improved security, and better performance in different environments. Some of the most widely used standards include 802.11a, 802.11b, 802.11g, 802.1 In, 802.1 lac, and 802.1 lax (also known as “Wi-Fi 6”). These standards specify the modulation techniques, channel bandwidths, and other technical aspects that facilitate interoperability between devices from various manufacturers. IEEE 802.11 has played an important role in the widespread adoption of wireless networking in homes, offices, and public spaces, enabling users to connect their devices to the internet and each other without the need for wired connections.

[0004] Non-primary channel access (NPCA) is a technology that allows transmission and reception to be performed in an idle non-primary channel (e.g., a secondary channel) if the primary channel is busy. That is, even if the primary channel is busy, if there is a non-primary channel that is idle, NPCA allows transmission / reception in the idle non-primary channel.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0005] A STA that is capable of performing NPCA may receive / overhear a physical layer protocol data unit (PPDU) that was transmitted by the current OBSS (overlapping BSS) TXOP (transmission opportunity) holder or a third-party OBSS while its NAV (network allocation vector) is active. However, the existing IEEE 802.11 wireless networking standards do not take the NAV status into consideration when deciding whether to switch channels to perform NPCA.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The disclosure will be more fully understood from the detailed description provided below and the accompanying drawings that depict various embodiments of the disclosure.However, these drawings should not be interpreted as limiting the disclosure to the specific embodiments shown; they are provided for explanation and understanding only.

[0007] Figure 1 illustrates an example of a wireless local area network (WLAN) with a basic service set (BSS) that includes multiple wireless devices, in accordance with some embodiments of the present disclosure.

[0008] Figure 2 is a schematic diagram of a wireless device, in accordance with some embodiments of the present disclosure.

[0009] Figure 3 A illustrates components of a wireless device configured to transmit data, in accordance with some embodiments of the present disclosure.

[0010] Figure 3B illustrates components of a wireless device configured to receive data, in accordance with some embodiments of the present disclosure.

[0011] Figure 4 illustrates interframe space (IFS) relationships, in accordance with some embodiments of the present disclosure.

[0012] Figure 5 illustrates a Carrier Sense Multiple Access with Collision Avoidance (CSMAZCA)-based frame transmission procedure, in accordance with some embodiments of the present disclosure.

[0013] Figure 6 illustrates maximum physical layer (PHY) rates for Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards, in accordance with some embodiments of the present disclosure.

[0014] Figure 7 provides a detailed description of fields in Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) frames, including their purposes and characteristics, in accordance with some embodiments of the present disclosure.

[0015] Figure 8 illustrates an example of multi-user (MU) transmission in Orthogonal Frequency-Division Multiple Access (OFDMA), in accordance with some embodiments of the present disclosure.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0016] Figure 9 illustrates an example of an access point sending a trigger frame to multiple associated stations and receiving Uplink Orthogonal Frequency-Division Multiple Access Trigger-Based Physical Protocol Data Units (UL OFDMA TB PPDUs) in response, in accordance with some embodiments of the present disclosure.

[0017] Figure 10 is a diagram showing a wireless network topology in which an overlapping basic service set (OBSS) physical layer protocol data unit (PPDU) can be received while network allocation vector (NAV) is active, according to some embodiments.

[0018] Figure 11 is a diagram showing a scenario where the non-primary channel access (NPCA)-capable access point (AP) is outside the transmission range of the OBSS PPDU, according to some embodiments.

[0019] Figure 12 is a diagram showing a scenario where the NPCA-capable AP is within the transmission range of the OBSS PPDU, according to some embodiments.

[0020] Figure 13 is a flow diagram of a NPCA channel switching decision making process, according to some embodiments.

[0021] Figure 14 is a flow diagram showing a method for performing NPCA channel switching, according to some embodiments.

[0022] Figure 15 is a flow diagram showing a method for making a NPCA channel switching decision, according to some embodiments.DETAILED DESCRIPTION

[0023] The present disclosure generally relates to wireless communications, and more specifically, relates to a non-primary channel access (NPCA) channel switching decision making process based on network allocation vector (NAV) status.

[0024] As mentioned earlier herein, A STA that is capable of performing NPCA may receive / overhear a physical layer protocol data unit (PPDU) that was transmitted by the current OBSS (overlapping basic service set) TXOP (transmission opportunity) holder or a third-party OBSS while its NAV (network allocation vector) is active. However, the existing IEEE 802.11 wireless networking standards do not take the NAV status into consideration when deciding whether to switch channels to perform NPCA.

[0025] The present disclosure defines NPCA channel switching decision rules for whether a non-AP STA that is capable of performing NPCA is allowed to switch channels to perform NPCA when the STA receive s / overhears an OBSS PPDU while its intra-BSS NAV and / or basic NAV are active. The NPCA channel switching decision rules may be designed to take the access point’s (AP’s) channel switching behavior into consideration.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0026] In an embodiment, a STA decides not to perform NPCA channel switching even after receiving / overhearing an OBSS PPDU if its intra-BSS NAV is active (because, as will be described in additional detail herein, it can be inferred from the intra-BSS NAV being set that the STA’s associated AP will likely not be able to overhear / decode the OBSS PPDU and thus not perform NPCA channel switching). In an embodiment, the STA decides to perform NPCA channel switching upon receiving / overhearing an OBSS PPDU despite its basic NAV being set (assuming that the intra-BSS NAV is not set).

[0027] In an embodiment, the STA determines whether the originator of the OBSS PPDU that was received during the STA’s intra-BSS NAV period (while the STA’s intra-BSS NAV was active) is an OBSS TXOP holder. If the originator of the OBSS PPDU is determined to be an OBSS TXOP holder, the STA may assess whether this OBSS TXOP holder could affect the AP associated with the STA during subsequent transmissions. Based on this assessment, the STA may individually determine whether to perform NPCA channel switching (whether to switch from operating in the primary channel to operating in the NPCA primary channel) to perform NPCA. Specifically, the STA may determine not to perform NPCA channel switching (remain operating in the primary channel) despite receiving / overhearing a subsequent OBSS PPDU after the STA’s intra-BSS NAV has expired if the subsequent OBSS PPDU originates from the same OBSS TXOP holder. The reasoning for this behavior is as follows. If the OBSS TXOP holder transmitted a PPDU while the STA’s intra-BSS NAV was still active, this likely means that the OBSS TXOP holder is in a hidden relationship with respect to the AP associated with the STA (because otherwise the mutual protection rules would have prevented the OBSS TXOP holder from transmitting a PPDU while the STA’s intra-BSS NAV was active). Thus, the AP associated with the STA will likely not be able to receive / overhear the OBSS TXOP holder’s subsequent PPDU and thus not perform NPCA channel switching (and thus it is meaningless for the STA to perform NPCA channel switching in this case). Such NPCA channel switching decision rule takes the associated AP’s behavior into consideration, which can help avoid unnecessary channel switching and thus reduce the STA’s power consumption and maintain overall network stability.

[0028] For purposes of illustration, various embodiments are described herein in the context of wireless networks that are based on IEEE 802.11 standards and using terminology and concepts thereof. Those skilled in the art will appreciate that the embodiments disclosed herein can be modified / adapted for use in other types of wireless networks.

[0029] In the following detailed description, only certain embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the Docket No. 1002P25013W01Client Matter No. P25-013WO1art would realize, the described embodiments may be modified in different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

[0030] Figure 1 shows a wireless local area network (WLAN) 100 with a basic service set (BSS) 102 that includes a plurality of wireless devices 104 (sometimes referred to as WLAN devices 104). Each of the wireless devices 104 may include a medium access control (MAC) layer and a physical (PHY) layer according to an IEEE (Institute of Electrical and Electronics Engineers) standard 802.11, including one or more of the amendments(e.g., 802.1 la / b / g / n / p / ac / ax / bd / be). In one embodiment, the MAC layer of a wireless device 104 may initiate transmission of a frame to another wireless device 104 by passing a PHY-TXSTART. request (TXVECTOR) to the PHY layer. The TXVECTOR provides parameters for generating and / or transmitting a corresponding frame. Similarly, a PHY layer of a receiving wireless device may generate an RXVECTOR, which includes parameters of a received frame and is passed to a MAC layer for processing.

[0031] The plurality of wireless devices 104 may include a wireless device 104A that is an access point (sometimes referred to as an AP station or AP STA) and the other wireless devices 104B1-104B4 that are non-AP stations (sometimes referred to as non-AP STAs).Alternatively, all the plurality of wireless devices 104 may be non-AP STAs in an ad-hoc networking environment. In general, the AP STA (e.g., wireless device 104A) and the non-AP STAs (e.g., wireless devices 104B1-104B4) may be collectively referred to as STAs. However, for ease of description, only the non-AP STAs may be referred to as STAs unless the context indicates otherwise. Although shown with four non-AP STAs (e.g., the wireless devices 104B1-104B4), the WLAN 100 may include any number of non-AP STAs (e.g., one or more wireless devices 104B).

[0032] Figure 2 illustrates a schematic block diagram of a wireless device 104, according to an embodiment. The wireless device 104 may be the wireless device 104 A (i.e., the AP of the WLAN 100) or any of the wireless devices 104B1-104B4 in Figure 1. The wireless device 104 includes a baseband processor 210, a radio frequency (RF) transceiver 240, an antenna unit 250, a storage device (e.g., memory device) 232, one or more input interfaces 234, and one or more output interfaces 236. The baseband processor 210, the storage device 232, the input interfaces 234, the output interfaces 236, and the RF transceiver 240 may communicate with each other via a bus 260.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0033] The baseband processor 210 performs baseband signal processing and includes a MAC processor 212 and a PHY processor 222. The baseband processor 210 may utilize the memory 232, which may include a non-transitory computer / machine readable medium having software (e.g., computer / machine programing instructions) and data stored therein.

[0034] In an embodiment, the MAC processor 212 includes a MAC software processing unit 214 and a MAC hardware processing unit 216. The MAC software processing unit 214 may implement a first plurality of functions of the MAC layer by executing MAC software, which may be included in the software stored in the storage device 232. The MAC hardware processing unit 216 may implement a second plurality of functions of the MAC layer in specialpurpose hardware. However, the MAC processor 212 is not limited thereto. For example, the MAC processor 212 may be configured to perform the first and second plurality of functions entirely in software or entirely in hardware according to an implementation.

[0035] The PHY processor 222 includes a transmitting (TX) signal processing unit (SPU) 224 and a receiving (RX) SPU 226. The PHY processor 222 implements a plurality of functions of the PHY layer. These functions may be performed in software, hardware, or a combination thereof according to an implementation.

[0036] Functions performed by the transmitting SPU 224 may include one or more of Forward Error Correction (FEC) encoding, stream parsing into one or more spatial streams, diversity encoding of the spatial streams into a plurality of space-time streams, spatial mapping of the space-time streams to transmit chains, inverse Fourier Transform (iFT) computation, Cyclic Prefix (CP) insertion to create a Guard Interval (GI), and the like. Functions performed by the receiving SPU 226 may include inverses of the functions performed by the transmitting SPU 224, such as GI removal, Fourier Transform computation, and the like.

[0037] The RF transceiver 240 includes an RF transmitter 242 and an RF receiver 244. The RF transceiver 240 is configured to transmit first information received from the baseband processor 210 to the WLAN 100 (e.g., to another WLAN device 104 of the WLAN 100) and provide second information received from the WLAN 100 (e.g., from another WLAN device 104 of the WLAN 100) to the baseband processor 210.

[0038] The antenna unit 250 includes one or more antennas. When Multiple-Input Multiple-Output (MIMO) or Multi-User MIMO (MU-MIMO) is used, the antenna unit 250 may include a plurality of antennas. In an embodiment, the antennas in the antenna unit 250 may operate as a beam-formed antenna array. In an embodiment, the antennas in the antenna unit 250 may be directional antennas, which may be fixed or steerable.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0039] The input interfaces 234 receive information from a user, and the output interfaces 236 output information to the user. The input interfaces 234 may include one or more of a keyboard, keypad, mouse, touchscreen, microphone, and the like. The output interfaces 236 may include one or more of a display device, touch screen, speaker, and the like.

[0040] As described herein, many functions of the WLAN device 104 may be implemented in either hardware or software. Which functions are implemented in software and which functions are implemented in hardware will vary according to constraints imposed on a design. The constraints may include one or more of design cost, manufacturing cost, time to market, power consumption, available semiconductor technology, etc.

[0041] As described herein, a wide variety of electronic devices, circuits, firmware, software, and combinations thereof may be used to implement the functions of the components of the WLAN device 104. Furthermore, the WLAN device 104 may include other components, such as application processors, storage interfaces, clock generator circuits, power supply circuits, and the like, which have been omitted in the interest of brevity.

[0042] Figure 3 A illustrates components of a WLAN device 104 configured to transmit data according to an embodiment, including a transmitting (Tx) SPU (TxSP) 324, an RF transmitter 342, and an antenna 352. In an embodiment, the TxSP 324, the RF transmitter 342, and the antenna 352 correspond to the transmitting SPU 224, the RF transmitter 242, and an antenna of the antenna unit 250 of Figure 2, respectively.

[0043] The TxSP 324 includes an encoder 300, an interleaver 302, a mapper 304, an inverse Fourier transformer (IFT) 306, and a guard interval (GI) inserter 308.

[0044] The encoder 300 receives and encodes input data. In an embodiment, the encoder 300 includes a forward error correction (FEC) encoder. The FEC encoder may include a binary convolution code (BCC) encoder followed by a puncturing device. The FEC encoder may include a low-density parity-check (LDPC) encoder.

[0045] The TxSP 324 may further include a scrambler for scrambling the input data before the encoding is performed by the encoder 300 to reduce the probability of long sequences of 0s or Is. When the encoder 300 performs the BCC encoding, the TxSP 324 may further include an encoder parser for demultiplexing the scrambled bits among a plurality of BCC encoders. If LDPC encoding is used in the encoder, the TxSP 324 may not use the encoder parser.

[0046] The interleaver 302 interleaves the bits of each stream output from the encoder 300 to change an order of bits therein. The interleaver 302 may apply the interleaving only when the encoder 300 performs BCC encoding and otherwise may output the stream output from the encoder 300 without changing the order of the bits therein.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0047] The mapper 304 maps the sequence of bits output from the interleaver 302 to constellation points. If the encoder 300 performed LDPC encoding, the mapper 304 may also perform LDPC tone mapping in addition to constellation mapping.

[0048] When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324 may include a plurality of interleavers 302 and a plurality of mappers 304 according to a number of spatial streams (NSS) of the transmission. The TxSP 324 may further include a stream parser for dividing the output of the encoder 300 into blocks and may respectively send the blocks to different interleavers 302 or mappers 304. The TxSP 324 may further include a space-time block code (STBC) encoder for spreading the constellation points from the spatial streams into a number of space-time streams (NSTS) and a spatial mapper for mapping the space-time streams to transmit chains. The spatial mapper may use direct mapping, spatial expansion, or beamforming.

[0049] The IFT 306 converts a block of the constellation points output from the mapper 304 (or, when MIMO or MU-MIMO is performed, the spatial mapper) to a time domain block (i.e., a symbol) by using an inverse discrete Fourier transform (IDFT) or an inverse fast Fourier transform (IFFT). If the STBC encoder and the spatial mapper are used, the IFT 306 may be provided for each transmit chain.

[0050] When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324 may insert cyclic shift diversities (CSDs) to prevent unintentional beamforming. The TxSP 324 may perform the insertion of the CSD before or after the IFT 306. The CSD may be specified per transmit chain or may be specified per space-time stream. Alternatively, the CSD may be applied as a part of the spatial mapper.

[0051] When the TxSP 324 performs a MIMO or MU-MIMO transmission, some blocks before the spatial mapper may be provided for each user.

[0052] The GI inserter 308 prepends a GI to each symbol produced by the IFT 306. Each GI may include a Cyclic Prefix (CP) corresponding to a repeated portion of the end of the symbol that the GI precedes. The TxSP 324 may optionally perform windowing to smooth edges of each symbol after inserting the GI.

[0053] The RF transmitter 342 converts the symbols into an RF signal and transmits the RF signal via the antenna 352. When the TxSP 324 performs a MIMO or MU-MIMO transmission, the GI inserter 308 and the RF transmitter 342 may be provided for each transmit chain.

[0054] Figure 3B illustrates components of a WLAN device 104 configured to receive data according to an embodiment, including a Receiver (Rx) SPU (RxSP) 326, an RF receiver 344, and an antenna 354. In an embodiment, the RxSP 326, RF receiver 344, and antenna 354 may Docket No. 1002P25013W01Client Matter No. P25-013WO1correspond to the receiving SPU 226, the RF receiver 244, and an antenna of the antenna unit 250 of Figure 2, respectively.

[0055] The RxSP 326 includes a GI remover 318, a Fourier transformer (FT) 316, a demapper 314, a deinterleaver 312, and a decoder 310.

[0056] The RF receiver 344 receives an RF signal via the antenna 354 and converts the RF signal into symbols. The GI remover 318 removes the GI from each of the symbols. When the received transmission is a MIMO or MU-MIMO transmission, the RF receiver 344 and the GI remover 318 may be provided for each receive chain.

[0057] The FT 316 converts each symbol (that is, each time domain block) into a frequency domain block of constellation points by using a discrete Fourier transform (DFT) or a fast Fourier transform (FFT). The FT 316 may be provided for each receive chain.

[0058] When the received transmission is the MIMO or MU-MIMO transmission, the RxSP 326 may include a spatial demapper for converting the respective outputs of the FTs 316 of the receiver chains to constellation points of a plurality of space-time streams, and an STBC decoder for despreading the constellation points from the space-time streams into one or more spatial streams.

[0059] The demapper 314 demaps the constellation points output from the FT 316 or the STBC decoder to bit streams. If the received transmission was encoded using LDPC encoding, the demapper 314 may further perform LDPC tone demapping before performing the constellation demapping.

[0060] The deinterleaver 312 deinterleaves the bits of each stream output from the demapper 314. The deinterleaver 312 may perform the deinterleaving only when the received transmission was encoded using BCC encoding, and otherwise may output the stream output by the demapper 314 without performing deinterleaving.

[0061] When the received transmission is the MIMO or MU-MIMO transmission, the RxSP 326 may use a plurality of demappers 314 and a plurality of deinterleavers 312 corresponding to the number of spatial streams of the transmission. In this case, the RxSP 326 may further include a stream deparser for combining the streams output from the deinterleavers 312.

[0062] The decoder 310 decodes the streams output from the deinterleaver 312 or the stream deparser. In an embodiment, the decoder 310 includes an FEC decoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

[0063] The RxSP 326 may further include a descrambler for descrambling the decoded data. When the decoder 310 performs BCC decoding, the RxSP 326 may further include an encoder Docket No. 1002P25013W01Client Matter No. P25-013WO1deparser for multiplexing the data decoded by a plurality of BCC decoders. When the decoder 310 performs the LDPC decoding, the RxSP 326 may not use the encoder deparser.

[0064] Before making a transmission, wireless devices such as wireless device 104 will assess the availability of the wireless medium using Clear Channel Assessment (CCA). If the medium is occupied, CCA may determine that it is busy, while if the medium is available, CCA determines that it is idle.

[0065] The PHY entity for IEEE 802.11 is based on Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). In either OFDM or OFDMA Physical (PHY) layers, a STA (e.g., a wireless device 104) is capable of transmitting and receiving Physical Layer (PHY) Protocol Data Units (PPDUs) (also referred to as PLCP (Physical Layer Convergence Procedure) Protocol Data Units) that are compliant with the mandatory PHY specifications. A PHY specification defines a set of Modulation and Coding Schemes (MCS) and a maximum number of spatial streams. Some PHY entities define downlink (DL) and uplink (UL) Multi-User (MU) transmissions having a maximum number of space-time streams (STS) per user and employing up to a predetermined total number of STSs. A PHY entity may provide support for 10 Megahertz (MHz), 20 MHz, 40 MHz, 80 MHz, 160 MHz, 240 MHz, and 320 MHz contiguous channel widths and support for an 80+80, 80+160 MHz, and 160+160 MHz non-contiguous channel width. Each channel includes a plurality of subcarriers, which may also be referred to as tones. A PHY entity may define signaling fields denoted as Legacy Signal (L-SIG), Signal A (SIG-A), and Signal B (SIG-B), and the like within a PPDU by which some necessary information about PHY Service Data Unit (PSDU) attributes are communicated. The descriptions below, for sake of completeness and brevity, refer to OFDM-based 802.11 technology. Unless otherwise indicated, a station refers to a non-AP STA.

[0066] Figure 4 illustrates Inter-Frame Space (IFS) relationships. In particular, Figure 4 illustrates a Short IFS (SIFS), a Point Coordination Function (PCF) IFS (PIFS), a Distributed Coordination Function (DCF) IFS (DIFS), and an Arbitration IFSs corresponding to an Access Category (AC) ‘i’ (AIFS[i]). Figure 4 also illustrates a slot time and a data frame is used for transmission of data forwarded to a higher layer. As shown, a WLAN device 104 transmits the data frame after performing backoff if a DIFS has elapsed during which the medium has been idle.

[0067] A management frame may be used for exchanging management information, which is not forwarded to the higher layer. Subtype frames of the management frame include a beacon frame, an association request / response frame, a probe request / response frame, and an authentication request / response frame.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0068] A control frame may be used for controlling access to the medium. Subtype frames of the control frame include a request to send (RTS) frame, a clear to send (CTS) frame, and an acknowledgement (ACK) frame.

[0069] When the control frame is not a response frame of another frame, the WLAN device 104 transmits the control frame after performing backoff if a DIFS has elapsed during which the medium has been idle. When the control frame is the response frame of another frame, the WLAN device 104 transmits the control frame after a SIFS has elapsed without performing backoff or checking whether the medium is idle.

[0070] A WLAN device 104 that supports Quality of Service (QoS) functionality (that is, a QoS STA) may transmit the frame after performing backoff if an AIFS for an associated access category (AC) (i.e., AIFS[AC]) has elapsed. When transmitted by the QoS STA, any of the data frame, the management frame, and the control frame, which is not the response frame, may use the AIFS [AC] of the AC of the transmitted frame.

[0071] A WLAN device 104 may perform a backoff procedure when the WLAN device 104 that is ready to transfer a frame finds the medium busy. The backoff procedure includes determining a random backoff time composed of N backoff slots, where each backoff slot has a duration equal to a slot time and N being an integer number greater than or equal to zero. The backoff time may be determined according to a length of a Contention Window (CW). In an embodiment, the backoff time may be determined according to an AC of the frame. All backoff slots occur following a DIFS or Extended IFS (EIFS) period during which the medium is determined to be idle for the duration of the period.

[0072] When the WLAN device 104 detects no medium activity for the duration of a particular backoff slot, the backoff procedure shall decrement the backoff time by the slot time. When the WLAN device 104 determines that the medium is busy during a backoff slot, the backoff procedure is suspended until the medium is again determined to be idle for the duration of a DIFS or EIFS period. The WLAN device 104 may perform transmission or retransmission of the frame when the backoff timer reaches zero.

[0073] The backoff procedure operates so that when multiple WLAN devices 104 are deferring and execute the backoff procedure, each WLAN device 104 may select a backoff time using a random function and the WLAN device 104 that selects the smallest backoff time may win the contention, reducing the probability of a collision.

[0074] Figure 5 illustrates a Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) based frame transmission procedure for avoiding collision between frames in a channel according to an embodiment. Figure 5 shows a first station STA1 transmitting data, a second Docket No. 1002P25013W01Client Matter No. P25-013WO1station STA2 receiving the data, and a third station STA3 that may be located in an area where a frame transmitted from the STA1 can be received, a frame transmitted from the second station STA2 can be received, or both can be received. The stations STA1, STA2, and STA3 may be WLAN devices 104 of Figure 1.

[0075] The station STA1 may determine whether the channel is busy by carrier sensing. The station STA1 may determine channel occupation / status based on an energy level in the channel or an autocorrelation of signals in the channel, or may determine the channel occupation by using a network allocation vector (NAV) timer.

[0076] After determining that the channel is not used by other devices (that is, that the channel is IDLE) during a DIFS (and performing backoff if required), the station STA1 may transmit a Request-To-Send (RTS) frame to the station STA2. Upon receiving the RTS frame, after a SIFS the station STA2 may transmit a Clear-To-Send (CTS) frame as a response to the RTS frame. If Dual-CTS is enabled and the station STA2 is an AP, the AP may send two CTS frames in response to the RTS frame (e.g., a first CTS frame in a non-High Throughput format and a second CTS frame in the HT format).

[0077] When the station STA3 receives the RTS frame, it may set a NAV timer of the station STA3 for a transmission duration of subsequently transmitted frames (for example, a duration of SIFS + CTS frame duration + SIFS + data frame duration + SIFS + ACK frame duration) using duration information included in the RTS frame. When the station STA3 receives the CTS frame, it may set the NAV timer of the station STA3 for a transmission duration of subsequently transmitted frames using duration information included in the CTS frame. Upon receiving a new frame before the NAV timer expires, the station STA3 may update the NAV timer of the station STA3 by using duration information included in the new frame. The station STA3 does not attempt to access the channel until the NAV timer expires.

[0078] When the station STA1 receives the CTS frame from the station STA2, it may transmit a data frame to the station STA2 after a SIFS period elapses from a time when the CTS frame has been completely received. Upon successfully receiving the data frame, the station STA2 may transmit an ACK frame as a response to the data frame after a SIFS period elapses.

[0079] When the NAV timer expires, the third station STA3 may determine whether the channel is busy using the carrier sensing. Upon determining that the channel is not used by other devices during a DIFS period after the NAV timer has expired, the station STA3 may attempt to access the channel after a contention window elapses according to a backoff process.

[0080] When Dual-CTS is enabled, a station that has obtained a transmission opportunity (TXOP) and that has no data to transmit may transmit a CF-End frame to cut short the TXOP. Docket No. 1002P25013W01Client Matter No. P25-013WO1An AP receiving a CF-End frame having a Basic Service Set Identifier (BSSID) of the AP as a destination address may respond by transmitting two more CF-End frames: a first CF-End frame using Space Time Block Coding (STBC) and a second CF-End frame using non-STBC. A station receiving a CF-End frame resets its NAV timer to 0 at the end of the PPDU containing the CF-End frame. Figure 5 shows the station STA2 transmitting an ACK frame to acknowledge the successful reception of a frame by the recipient.

[0081] The IEEE 802.1 Ibn (Ultra High Reliability, UHR) working group has been established to address the growing demand for higher peak throughput and reliability in Wi-Fi. As shown in Figure 6, the peak PHY rate has significantly increased from IEEE 802.1 lb to IEEE 802.1 Ibe (Wi-Fi 7), with the latter focusing on further improving peak throughput. The UHR study group aims to enhance the tail of the latency distribution and jitter to support applications that require low latency, such as video-over- WLAN, gaming, AR, and VR. It is noted that various characteristics of UHR (e.g., max PHY rate, PHY rate enhancement, bandwidth / number of spatial streams, and operating bands) are still to be determined.

[0082] The focus of IEEE 802.1 Ibe is primarily on WLAN indoor and outdoor operation with stationary and pedestrian speeds in the 2.4, 5, and 6 GHz frequency bands. In addition to peak PHY rate, different candidate features are under discussion. These candidate features include (1) a 320MHz bandwidth and a more efficient utilization of a non-contiguous spectrum, (2) multi -band / multi-channel aggregation and operation, (3) 16 spatial streams and Multiple Input Multiple Output (MIMO) protocol enhancements, (4) multi-Access Point (AP) Coordination (e.g., coordinated and joint transmission), (5) an enhanced link adaptation and retransmission protocol (e.g., Hybrid Automatic Repeat Request (HARQ)), and (6) adaptation to regulatory rules specific to a 6 GHz spectrum.

[0083] The focus of IEEE 802.1 Ibn (UHR) is still under discussion, with candidate features including MLO enhancements (e.g., in terms of increased throughput / reliability and decreased latency), latency and reliability improvements (e.g., multi-AP coordination to support low latency traffic), bandwidth expansion (e.g., to 240, 480, 640 MHz), aggregated PPDU (A-PPDU), enhanced multi-link single-radio (eMLSR) extensions to AP, roaming improvements, and power-saving schemes for prolonging battery life.

[0084] Some features, such as increasing the bandwidth and the number of spatial streams, are solutions that have been proven to be effective in previous projects focused on increasing link throughput and on which feasibility demonstration is achievable.

[0085] With respect to operational bands (e.g., 2.4 / 5 / 6 GHz) for IEEE 802.1 Ibe, more than 1 GHz of additional unlicensed spectrum is likely to be available because the 6 GHzDocket No. 1002P25013W01Client Matter No. P25-013WO1band (5.925- 7.125 GHz) is being considered for unlicensed use. This would allow APs and STAs to become tri -band devices. Larger than 160MHz data transmissions (e.g., 320 MHz or 640 MHz) could be considered to increase the maximum PHY rate. For example, 320 MHz or 160+160MHz data could be transmitted in the 6 GHz band. For example, 160+160 MHz data could be transmitted across the 5 and 6 GHz bands.

[0086] In the process of wireless communication, a transmitting station (STA) creates a Physical Layer Protocol Data Unit (PPDU) frame and sends it to a receiving STA. The receiving STA then receives, detects, and processes the PPDU.

[0087] The Extremely High Throughput (EHT) PPDU frame encompasses several components. It includes a legacy part, which comprises fields such as the Legacy Short Training Field (L-STF), Legacy Long Training Field (L-LTF), Legacy Signal Field (L-SIG), and Repeated Legacy Signal Field (RL-SIG). These fields are used to maintain compatibility with older Wi-Fi standards.

[0088] In addition to the legacy part, the EHT PPDU frame also contains the Universal Signal Field (U-SIG), EHT Signal Field (EHT-SIG), EHT Short Training Field (EHT-STF), and EHT Long Training Field (EHT-LTF). These fields are specific to the EHT standard and are used for various purposes, such as signaling, synchronization, and channel estimation.

[0089] Figure 7 provides a more detailed description of each field in the EHT PPDU frame, including their purposes and characteristics.

[0090] Regarding the Ultra High Reliability (UHR) PPDU, its frame structure is currently undefined and will be determined through further discussions within the relevant working group or study group. This indicates that the specifics of the UHR PPDU are still under development and will be finalized based on the outcomes of future deliberations.

[0091] The distributed nature of channel access networks, such as IEEE 802.11 WLANs, makes the carrier sense mechanism useful for ensuring collision-free operation. Each station (STA) uses its physical carrier sense to detect transmissions from other STAs. However, in certain situations, it may not be possible for a STA to detect every transmission. For instance, when one STA is located far away from another STA, it might perceive the medium as idle and start transmitting a frame, leading to collisions. To mitigate this hidden node problem, the network allocation vector (NAV) has been introduced.

[0092] As the IEEE 802.11 standard continues to evolve, it now includes scenarios where multiple users can simultaneously transmit or receive data within a basic service set (BSS), such as uplink (UL) and downlink (DL) multi-user (MU) transmissions in a cascaded manner. In these cases, the existing carrier sense and NAV mechanisms may not be sufficient, and Docket No. 1002P25013W01Client Matter No. P25-013WO1modifications or newly defined mechanisms may be required to facilitate efficient and collision-free operation.

[0093] For the purpose of this disclosure, MU transmission refers to situations where multiple frames are transmitted to or from multiple STAs simultaneously using different resources.Examples of these resources include different frequency resources in Orthogonal Frequency Division Multiple Access (OFDMA) transmission and different spatial streams in Multi-User Multiple Input Multiple Output (MU-MIMO) transmission. Consequently, downlink OFDMA (DL-OFDMA), downlink MU-MIMO (DL-MU-MIMO), uplink OFDMA (UL-OFDMA), uplink MU-MIMO (UL-MU-MIMO), and OFDMA with MU-MIMO are all considered examples of MU transmission.

[0094] Figure 8 illustrates an example of multi-user (MU) transmission in Orthogonal Frequency-Division Multiple Access (OFDMA), in accordance with some embodiments of the present disclosure.

[0095] In the IEEE 802.1 lax and 802.1 Ibe specifications, the trigger frame plays a useful role in facilitating uplink multi-user (MU) transmissions. The purpose of the trigger frame is to allocate resources and solicit one or more Trigger-based (TB) Physical Layer Protocol Data Unit (PPDU) transmissions from the associated stations (STAs).

[0096] The trigger frame contains information required by the responding STAs to send their Uplink TB PPDUs. This information includes the Trigger type, which specifies the type of TB PPDU expected, and the Uplink Length (UL Length), which indicates the duration of the uplink transmission.

[0097] Figure 9 illustrates an example scenario where an access point (AP) operating in an 80MHz bandwidth environment sends a Trigger frame to multiple associated STAs. Upon receiving the Trigger frame, the STAs respond by sending their respective Uplink Orthogonal Frequency Division Multiple Access (UL OFDMA) TB PPDUs, utilizing the allocated resources within the specified 80 MHz bandwidth.

[0098] After successfully receiving the UL OFDMA TB PPDUs, the AP acknowledges the STAs by sending an acknowledgement frame. This acknowledgement can be in the form of an 80MHz width multi-STA Block Acknowledgement (Block Ack) or a Block Acknowledgement with a Direct Feedback (DF) OFDMA method. The multi-STA Block Ack allows the AP to acknowledge multiple STAs simultaneously, while the Block Ack with DF OFDMA enables the AP to provide feedback to the STAs using the same OFDMA technique employed in the uplink transmission.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0099] The trigger frame is a useful component in enabling efficient uplink MU transmissions in IEEE 802.1 lax and 802.1 Ibe networks, by allocating resources and coordinating the uplink transmissions from multiple STAs within the same bandwidth.

[0100] Wireless network systems can rely on retransmission of media access control (MAC) protocol data units (MPDUs) when the transmitter (TX) does not receive an acknowledgement from the receiver (RX) or MPDUs are not successfully decoded by the receiver. Using an automatic repeat request (ARQ) approach, the receiver discards the last failed MPDU before receiving the newly retransmitted MPDU. With requirements of enhanced reliability and reduced latency, the wireless network system can evolve toward a hybrid ARQ (HARQ) approach.

[0101] There are two methods of HARQ processing. In a first type of HARQ scheme, also referred to as chase combining (CC) HARQ (CC-HARQ) scheme, signals to be retransmitted are the same as the signals that previously failed because all subpackets to be retransmitted use the same puncturing pattern. The puncturing is needed to remove some of the parity bits after encoding using an error-correction code. The reason why the same puncturing pattern is used with CC-HARQ is to generate a coded data sequence with forward error correction (FEC) and to make the receiver use a maximum-ratio combining (MRC) to combine the received, retransmitted bits with the same bits from the previous transmission. For example, information sequences are transmitted in packets with a fixed length. At a receiver, error correction and detection are carried out over the whole packet. However, the ARQ scheme may be inefficient in the presence of burst errors. To solve this more efficiently, subpackets are used. In subpacket transmissions, only those subpackets that include errors need to be retransmitted.

[0102] Since the receiver uses both the current and the previously received subpackets for decoding data, the error probability in decoding decreases as the number of used subpackets increases. The decoding process passes a cyclic redundancy check (CRC) and ends when the entire packet is decoded without error or the maximum number of subpackets is reached. In particular, this scheme operates on a stop-and-wait protocol such that if the receiver can decode the packet, it sends an acknowledgement (ACK) to the transmitter. When the transmitter receives an ACK successfully, it terminates the HARQ transmission of the packet. If the receiver cannot decode the packet, it sends a negative acknowledgement (NAK) to the transmitter and the transmitter performs the retransmission process.

[0103] In a second type of HARQ scheme, also referred to as an incremental redundancy (IR) HARQ (IR-HARQ) scheme, different puncturing patterns are used for each subpacket such that the signal changes for each retransmitted subpacket in comparison to the originally transmitted Docket No. 1002P25013W01Client Matter No. P25-013WO1subpacket. IR-HARQ alternatively uses two puncturing patterns for odd numbered and even numbered transmissions, respectively. The redundancy scheme of IR-HARQ improves the log likelihood ratio (LLR) of parity bit(s) in order to combine information sent across different transmissions due to requests and lowers the code rate as the additional subpacket is used. This results in a lower error rate of the subpacket in comparison to CC-HARQ. The puncturing pattern used in IR-HARQ is indicated by a subpacket identity (SPID) indication. The SPID of the first subpacket may always be set to 0 and all the systematic bits and the punctured parity bits are transmitted in the first subpacket. Self-decoding is possible when the receiving signal-to-noise ratio (SNR) environment is good (i.e., a high SNR). In some embodiments, subpackets with corresponding SPIDs to be transmitted are in increasing order of SPID but can be exchanged / switched except for the first SPID.

[0104] AP coordination has been considered as a potential technology to improve WLAN system throughput in the IEEE 802.1 Ibe standard and is still being discussed in theIEEE 802.1 Ibn (UHR) standard. To support various AP coordination schemes, such as coordinated beamforming, OFDMA, TDMA, spatial reuse, and joint transmission, a predefined mechanism for APs is necessary.

[0105] In the context of coordinated TDMA (co-TDMA or c-TDMA), the AP that obtains a transmit opportunity (TXOP) is referred to as the sharing AP. This AP initiates the AP coordination schemes to determine the AP candidate set by sending a frame, such as a Beacon frame or probe response frame, which includes information about the AP coordination scheme capabilities. The AP that participates in the AP coordination schemes after receiving the frame from the sharing AP is called the shared AP. The sharing AP is also known as the master AP or coordinating AP, while the shared AP is referred to as the slave AP or coordinated AP.

[0106] The operation of various AP coordination schemes has been discussed in the IEEE 802.1 Ibe and UHR standards:

[0107] Coordinated Beamforming (C-BF): Multiple APs transmit on the same frequency resource by coordinating and forming spatial nulls, allowing for simultaneous transmission from multiple APs.

[0108] Coordinated OFDMA (C-OFDMA): APs transmit on orthogonal frequency resources by coordinating and splitting the spectrum, enabling more efficient spectrum utilization.

[0109] Joint Transmission (JTX): Multiple APs transmit jointly to a given user simultaneously by sharing data between the APs.

[0110] Coordinated Spatial Reuse (C-SR): Multiple APs or STAs adjust their transmit power to reduce interference between APs.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0111] By implementing these AP coordination schemes, WLAN systems can improve their overall throughput and efficiency by leveraging the cooperation between multiple APs.

[0112] NPCA is a technology that allows transmission and reception to be performed in an idle non-primary channel (e.g., a secondary channel) if the primary channel is busy. That is, even if the primary channel is busy, if there is a non-primary channel that is idle, NPCA allows transmission / reception in the idle non-primary channel.

[0113] When a NPCA-capable AP or non-AP STA receives / overhears an OBSS transmission in its primary channel, it may switch from operating in the primary channel to operating in a NPCA primary channel to perform NPCA if the NPCA triggering conditions are satisfied.

[0114] The existing NPCA channel switching decision rules do not take NAV status into consideration. There is no defined rule for whether a STA that receives / overhears an OBSS PPDU can switch from operating in the primary channel to operating in the NPCA primary channel to perform NPCA when the STA’s intra-BSS NAV and / or basic NAV is active.

[0115] Starting with the IEEE 802.1 lax wireless networking standard, non-AP STAs are capable of maintaining both an intra-BSS NAV and a basic NAV. Even when both NAVs are set / active, it is still possible for a non-AP STA to receive / overhear OBSS PPDUs depending on the network topology. For example, a STA may receive additional OBSS PPDUs from the current TXOP holder (that originally caused the STA’s NAV to be set) or possibly from a third-party OBSS transmitter while the STA’s intra-BSS NAV and / or basic NAV is active. However, there is no rule defined in the existing wireless networking standards with regard to whether a NPCA-capable STA is allowed to perform NPCA channel switching when the STA receives / overhears an OBSS PPDU while any of its NAVs are active.

[0116] The present disclosure describes and defines rules for whether or not a NPCA-capable STA is allowed to perform NPCA when it receives an OBSS PPDU while either or both its intra-BSS NAV and basic NAV are active.

[0117] Figure 10 is a diagram showing a wireless network topology in which an OBSS PPDU can be received while NAV is active, according to some embodiments.

[0118] As shown in the diagram, the wireless network topology includes a first AP (API) that operates a first BSS (BSS1), a second AP (AP2) that operates a second BSS (BSS2), and a third AP (AP3) that operates a third BSS (BSS3). BSS1 may include three STAs: STA1-1, STA1-2, and STA1-3. BSS2 may include one STA: STA2-1. BSS3 may include one STA: STA3-1. API, STA1-1, STA1-2, and STA1-3 are capable of performing NPCA (they are NPCA-capable AP / STAs that have NPCA functionality enabled). For sake of explanation, the NPCA channel switching decision rules will primarily be described herein from the perspective Docket No. 1002P25013W01Client Matter No. P25-013WO1of STA1-3. From the perspective of STA1-3, AP2 and AP3 are OBSS APs and STA2-1 and STA3-1 are OBSS STAs. More generally, from the perspective of BSS1, both BSS2 and BSS3 are considered to be an OBSS.

[0119] In the diagram, the transmission ranges of the different APs are depicted by differently dotted lines. API has a transmission range 1010 that can reach its in-BSS STAs (STA1-1, STA1-2, STA1-3), as well as AP3. AP2 has a transmission range 1020 that can reach its in-BSS STA (STA2-1), as well as STA1-3. AP3 has a transmission range 1030 that can reach its in-BSS STA (STA3-1), as well as API, STA1-2, and STA1-3.

[0120] The wireless network topology shown in the diagram is provided by way of example to help explain embodiments. It will be appreciated that the techniques and concepts described herein (e.g., the NPCA channel switching decision rules) can be applied to wireless networks that have a different topology than shown in the diagram.

[0121] NPCA channel switching decision rules for a case when the intra-BSS NAV is active are now described.

[0122] Within a given BSS, the AP that operates the BSS and a specific STA that belongs to the BSS may exchange frames during a TXOP. During this TXOP, the other STAs that belong to the BSS that are not participating in the frame exchange may set their intra-BSS NAVs to protect the ongoing frame exchange. However, even during such in-BSS operations, transmissions from an OBSS may occur, and certain STAs that belong to the BSS may be in a position where they can receive / overhear OBSS PPDUs.

[0123] According to existing NPCA operation rules, a non-AP STA is required to perform NPCA channel switching if the duration value associated with the received / overheard OBSS PPDU exceeds a predefined threshold value. However, since NPCA operates in a distributed manner (each AP / STA makes its own independent decision regarding whether to perform NPCA channel switching), it is difficult for the STA to determine whether its associated AP actually received the OBSS PPDU and will switch channels to perform NPCA. For example, a STA that is located at the edge of its associated AP's transmission range may frequently experience a situation where it sets its basic NAV due to an OBSS PPDU transmission, even while its intra-BSS NAV is still active.

[0124] However, it is extremely rare for an AP to correctly receive and decode an OBSS PPDU without error during its own TXOP. Furthermore, if the AP is within the transmission range of the OBSS PPDU, there is a high likelihood of a collision occurring that makes successful reception by the AP difficult.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0125] Thus, when a STA receives / overhears an OBSS PPDU while its intra-BSS NAV is set, it is unlikely that its associated AP will also be able to successfully receive / overhear that same OBSS PPDU, in which case the AP will not perform NPCA channel switching. As such, it may be meaningless for the STA to perform NPCA channel switching in such situations. Thus, in an embodiment, a STA does not perform NPCA channel switching when it receives / overhears an OBSS PPDU while its intra-BSS NAV is active.

[0126] Two example scenarios are now described based on the wireless network topology shown in Figure 10. The first scenario is a scenario where the NPCA-capable AP is outside the transmission range of the OBSS PPDU. The second scenario is a scenario where the NPCA-capable AP is within the transmission range of the OBSS PPDU.

[0127] Figure 11 is a diagram showing a scenario where the NPCA-capable AP is outside the transmission range of the OBSS PPDU, according to some embodiments.

[0128] As shown in the diagram, following an enhanced distributed channel access (EDCA) backoff, API may transmit request-to-send (RTS) frame 1105 to STA1-1, which may be overheard by STA1-3. STA1-3 may set its intra-BSS NAV upon overhearing RTS frame 1105. STA1-3 may be in a hidden relationship with STA1-1. Responsive to receiving RTS frame 1105, STA1-1 may transmit clear-to-send (CTS) frame 1110 to API. API may then transmit trigger frame 1115 to STA1-1 to solicit an uplink transmission from STA1-1. STA1-3 may overhear trigger frame 1115. Responsive to receiving trigger frame 1115, STA1-1 may transmit uplink trigger-based PPDU (UL TB PPDU) 1120 to API. Responsive to receiving UL TB PPDU 1120, API may transmit block acknowledgment (BA) frame 1125 to STA1-1, which may be overheard by STA 1-3.

[0129] The duration of STAl-l's UL TB PPDU 1120 may be relatively longer than the duration of a general control response frame. As a result, AP2, which is in a hidden relationship with both API and STA1-1, may perceive the channel as being idle and attempt to transmit to STA2-1. For example, while STA1-1 is transmitting UL TB PPDU 1120, AP2 may transmit downlink (DL) data frame 1130 to STA2-1 (following an EDCA backoff), which may be overheard by STA1-3. STA1-3 may set its basic NAV upon overhearing DL data frame 1130. Responsive to receiving DL data frame 1130, STA2-1 may transmit BA frame 1135 to AP2. AP2 may then transmit another DL data frame 1140 to STA2-1, which may be overheard by STA1-3. Responsive to receiving DL data frame 1140, STA2-1 may transmit BA frame 1145 to AP2. AP2 may then transmit yet another DL data frame 1150 to STA2-1, which may be overheard by STA1-3. Responsive to receiving DL data frame 1150, STA2-1 may transmit BA frame 1155 to AP2.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0130] In this example scenario, STA1-3, which is unable to overhear UL TB PPDU 1120 transmitted by STA1-1 (due to being in a hidden relationship with STA1-1), may be able to receive / overhear DL data frame 1130 transmitted by AP2. This is a case where STA1-3 receives / overhears an OBSS PPDU while its intra-BSS NAV is active. In this situation, STA1-3 may become eligible to perform NPCA. However, since API is not able to receive DL data frame 1130 in this network topology (due to API being in a hidden relationship with AP2), API will not perform NPCA. From the perspective of a STA, it should only perform NPCA channel switching if it can reasonably predict that its associated AP will also switch channels. Thus, in this scenario, the correct behavior is that STA1-3 should not perform NPCA channel switching but remain operating in the primary channel (since API will not perform NPCA channel switching anyway).

[0131] Figure 12 is a diagram showing a scenario where the NPCA-capable AP is within the transmission range of the OBSS PPDU, according to some embodiments.

[0132] As shown in the diagram, following an EDCA backoff, API may transmit RTS frame 1205 to STA1-1, which may be overheard by STA1-3 and AP3. STA1-3 may set its intra-BSS NAV upon overhearing RTS frame 1205. Also, AP3 may set its basic NAV upon overhearing RTS frame 1205. STA1-3 may be in a hidden relationship with STA1-1 and also be in a hidden relationship with STA3-1. Responsive to receiving RTS frame 1205, STA1-1 may transmit CTS frame 1210 to API. API may then transmit trigger frame 1215 to STA1-1 to solicit an uplink transmission from STA1-1. STA1-3 and AP3 may overhear trigger frame 1215. Responsive to receiving trigger frame 1215, STA1-1 may transmit UL TB PPDU 1220 to API.

[0133] During STAl-l’s transmission of UL TB PPDU 1220, STA3-1 may perceive the channel as being idle and transmit uplink (UL) data frame 1225 to AP3 (following an EDCA backoff). Responsive to receiving UL data frame 1225, AP3 may transmit BA frame 1230 to STA3-1, which may be overheard by STA1-3 and cause a collision at API. As a result, API may not be able to successfully receive and decode UL TB PPDU 1220 and thus may not transmit BA frame 1235 to STALL STA1-3 may set its basic NAV upon overhearing BA frame 1230.

[0134] After receiving BA frame 1230, STA3-1 may transmit another UL data frame 1240 to AP3. Responsive to receiving UL data frame 1240, AP3 may transmit BA frame 1245 to STA3-1, which may be overheard by STA1-3 and API. API may set its basic NAV upon overhearing BA frame 1245. STA3-1 may then transmit yet another UL data frame 1250 to AP3.Responsive to receiving UL data frame 1250, AP3 may transmit BA frame 1255 to STA3-1, which may be overheard by STA1-3 and API.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0135] In this example scenario, BA frame 1230 transmitted by AP3 to STA3-1 may be received / overheard as a valid OBSS PPDU by STA1-3. However, from API’s perspective, BA frame 1230 collides with UL TB PPDU 1220 transmitted by STA1-1. Thus, in this situation, STA1-3 detects BA frame 1230 (which is an OBSS frame from STAl-3’s perspective) and becomes eligible to perform NPCA. However, even though API is within the transmission range of BA frame 1230, the probability of a collision is very high. If a collision occurs, API will not be able to correctly receive / overhear BA frame 1230. As a result, API will not perform NPCA channel switching, and accordingly, the correct behavior in this scenario is for STA1-3 to also refrain from performing NPCA channel switching.

[0136] Accordingly, in an embodiment, a NPCA-capable non-AP STA that has an active intra-BSS NAV does not perform NPCA channel switching even if it receives / overhears an OBSS PPDU and all other conditions for performing NPCA channel switching are satisfied. The reasoning for this behavior is that when the intra-BSS NAV is active there is insufficient basis to assume that the associated AP will also be able to successfully receive / overhear the same OBSS PPDU (e.g., there is a high likelihood that there will be a collision at the AP).

[0137] NPCA channel switching decision rules for a case when the basic NAV is active are now described.

[0138] A NPCA-capable STA may choose not to perform NPCA channels switching even after receiving / overhearing an OBSS PPDU for various reasons. One reason could be that the duration of the OBSS PPDU is not long enough to satisfy the minimum NPCA operation duration requirement. Another reason could be that NPCA operation is temporarily suppressed for all STAs within the BSS. Another reason could be that NPCA operation is not permitted because the OBSS PPDU is received while the intra-BSS NAV is active, as described earlier herein.

[0139] It is assumed that upon receiving / overhearing an OBSS PPDU while its intra-BSS NAV is active, the STA does not perform NPCA channel switching but instead sets its basic NAV.

[0140] As shown in the scenarios shown in Figure 11 and Figure 12 and described above, it is difficult for an individual STA to accurately determine whether its associated AP is within the transmission range of the received / overheard OBSS PPDU. Thus, in cases where a STA receives / overhears an OBSS PPDU while its intra-BSS NAV is active due to in-BSS operation, NPCA operation is not triggered (NPCA channel switching is not performed). Since the STA does not perform NPCA channel switching and remains operating in the primary channel, it may set the basic NAV based on the received OBSS PPDU.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0141] It is now considered how an individual STA can predict whether the associated AP will perform NPCA channel switching upon the STA receiving / overhearing an OBSS PPDU (e.g., DL data frame 1140 or BA frame 1245) after the intra-BSS NAV has expired.

[0142] In the example shown in Figure 11, when STA1-3 receives / overhears DL data frame 1130 (transmitted by AP2) while its intra-BSS NAV is active, STA1-3 can recognize that this DL data frame 1130 is not a control response frame but a transmission by an OBSS TXOP holder. The fact that a transmission by an OBSS TXOP holder is successfully received without error during an ongoing in-BSS operation indicates that STA1-3 is located near the edge of the transmission range of the transmitting OBSS TXOP holder. The reasoning for this is because if the OBSS TXOP holder were in a position to affect the in-BSS TXOP holder that caused STA1-3’s intra-BSS NAV to be set (API in this example), the OBSS PPDU would not have been transmitted due to mutual protection rules. Stated differently, if a STA is able to receive / overhear an OBSS PPDU transmitted by an OBSS TXOP holder while the STA’s intra-BSS NAV is active, it can be inferred that the AP associated with the STA is likely outside the transmission range of the OBSS TXOP holder. Thus, if a STA recognizes that an OBSS PPDU received / overheard during the intra-BSS NAV period (while the STA’s intra-BSS NAV is active) originated from a specific OBSS TXOP holder, the STA may choose not to perform NPCA channel switching if the STA receives / overhears a subsequent PPDU transmitted by the same OBSS TXOP holder after the intra-BSS NAV has expired and set its basic NAV.

[0143] If the OBSS PPDU received / overheard during the intra-BSS NAV period is a control response frame transmitted by an OBSS TXOP responder, it is difficult for the STA to determine whether the transmission will be successfully received / overheard by the STA’s associated AP. This is because a TXOP responder is allowed to transmit a control response frame in response to successful reception of a frame, regardless of the NAV status. For example, in the scenario shown in Figure 12, AP3 can transmit a BA frame even while its basic NAV is set, which may affect API and STA1-3. In contrast, in the scenario shown in Figure 11, when AP2 transmits a control response frame in response to STA2-l's uplink transmission, it may affect STA1-3, but it will not affect API. As such, a control response received from an OBSS during the intra-BSS NAV period is an uncertain indicator for inferring whether a collision will occur at the associated AP. Thus, in an embodiment, if a STA receives / overhears a control response frame from the same OBSS TXOP responder after the intra-BSS NAV has expired and only the basic NAV is set, the STA is still allowed to perform NPCA channel switching.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0144] In an embodiment, whether the duration value of the received / overheard OBSS PPDU is greater or less than the currently set basic NAV value does not directly affect the decision to perform NPCA channel switching. Stated differently, even if the duration value of the OBSS PPDU is less than the currently set NAV value, it is reasonable to set the NPCA operating duration based on the duration value, as long as the AP can decode the OBSS PPDU successfully. However, if the OBSS PPDU received / overheard during the intra-BSS NAV period can be identified as a transmission from an OBSS TXOP holder, it becomes possible to infer whether the associated AP could have received the OBSS PPDU. This, in turn, allows the STA to indirectly determine whether NPCA channel switching should be performed.

[0145] In an embodiment, NPCA operation is restricted or allowed as follows. When the intra-BSS NAV of a non-AP STA is inactive, NPCA operation is allowed upon receiving / overhearing an OBSS PPDU, regardless of the currently set basic NAV value (regardless of whether the basic NAV is active or not). However, if an OBSS PPDU is received while the intra-BSS NAV is active, NPCA operation is restricted. If the OBSS PPDU was transmitted by an OBSS TXOP holder, and another PPDU transmitted by the same OBSS TXOP holder is later received while only the basic NAV is active, it may be inferred that the previous transmission did not reach the associated AP. In such a case, NPCA operation may be restricted.

[0146] A STA may determine whether the originator of an OBSS PPDU that the STA received during the intra-BSS NAV period is an OBSS TXOP holder. If the originator is a TXOP holder, the STA may use this information to assess whether this OBSS TXOP holder could affect the AP associated with the STA in future transmissions. This allows the STA to make an independent decision regarding whether to perform NPCA channel switching.

[0147] Figure 13 is a flow diagram of a NPCA channel switching decision making process, according to some embodiments. The process may be carried out by a (non-AP) STA.

[0148] At operation 1310, the STA may overhear an OBSS PPDU and extract information from the OBSS PPDU such as the duration for NAV setting, BSS Color, frame type and subtype, and receiver address (RA), and transmitter address (TA). In an embodiment, the STA determines whether the transmitter / originator of the OBSS PPDU is a TXOP holder based on the frame type and subtype.

[0149] At operation 1320, the STA may determine whether it has NPCA capability or not. If the STA does not have NPCA capability, the process may proceed to operation 1360, where the STA sets its basic NAV, and the process ends. Otherwise, if the STA has NPCA capability, the process may proceed to operation 1330.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0150] At operation 1330, the STA may determine whether its intra-BSS NAV is active (e.g., has a non-zero value). If the intra-BSS NAV is active, the process may proceed to operation 1360, where the STA sets its basic NAV, and the process ends. Otherwise, if the intra-BSS NAV is not active (e.g., has a zero value), the process may proceed to operation 1340.

[0151] At operation 1340, the STA may determine whether a previous PPDU that was overheard while the intra-BSS NAV was active was transmitted by the same OBSS TXOP holder that transmitted the currently received / overheard OBSS PPDU. If so, the process may proceed to operation 1360, where the STA sets its basic NAV, and the process ends. Otherwise, if this is not the case (e.g., the currently received / overheard OBSS PPDU was transmitted by a different OBSS or not transmitted by a TXOP holder), the process may proceed to operation 1350. The STA may determine whether the currently received / overheard OBSS PPDU has been transmitted by the same OBSS TXOP holder that transmitted the previous PPDU based on comparing the BSS color fields, frame type and subtype fields, and / or RA / TA fields.

[0152] At operation 1350, the STA may determine whether the duration intended for NAV setting is greater than the NPCA operation threshold duration. The NPCA operation threshold duration may be the minimum duration for which NPCA is to be performed. If the duration intended for NAV setting is not greater than the NPCA operation threshold duration, the process may proceed to operation 1360, where the STA sets its basic NAV, and the process ends.Otherwise, if the duration intended for NAV setting is greater than the NPCA operation threshold duration, the process may proceed to operation 1370.

[0153] At operation 1370, the STA may switch from operating in the primary channel to operating in the NPCA primary channel (perform NPCA channel switching) to perform NPCA, and the process may end.

[0154] The NPCA channel switching decision making process enables a NPCA-capable STA to determine whether to perform NPCA channel switching in different NAV status scenarios. By predicting, from its own perspective, whether the associated AP is also likely to perform NPCA channel switching, an individual STA can avoid unnecessary NPCA channel switching. This contributes to power saving and helps maintain a stable connection with the AP.

[0155] Turning now to Figure 14, a method 1400 will be described for performing NPCA channel switching, in accordance with an example embodiment. The method 1400 may be performed by a non-AP STA that belongs to a BSS. The non-AP STA may be capable of maintaining an intra-BSS NAV and a basic NAV. The non-AP STA may be implemented by a wireless device (e.g., wireless device 104).Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0156] Additionally, although shown in a particular order, in some embodiments the operations of the method 1400 may be performed in a different order. For example, although the operations of the method 1400 are shown in a sequential order, some of the operations may be performed in partially or entirely overlapping time periods.

[0157] At operation 1405, the non-AP STA overhears a first PPDU in a primary channel of the BSS.

[0158] At operation 1410, the non-AP STA switches from operating in the primary channel of the BSS to operating in a NPCA primary channel of the BSS in response to overhearing the OBSS PPDU (and determining / confirming that the intra-BSS NAV is not active) despite the basic NAV being active. After performing such NPCA channel switching, the non-AP STA may transmit and / or receive PPDUs in the NPCA primary channel (e.g., in the NPCA available channel that includes the NPCA primary channel)

[0159] Turning now to Figure 15, a method 1500 will be described for making a NPCA channel switching decision, in accordance with an example embodiment. The method 1500 may be performed by a non-AP STA that belongs to a BSS. The non-AP STA may be capable of maintaining an intra-BSS NAV and a basic NAV. The non-AP STA may be implemented by a wireless device (e.g., wireless device 104).

[0160] At operation 1505, the non-AP STA overhears a first OBSS PPDU in a primary channel of the BSS.

[0161] At operation 1510, the non-AP STA refrains from switching channels despite overhearing the first OBSS PPDU in response to determining that the intra-BSS NAV is active.

[0162] At operation 1515, the non-AP STA sets the basic NAV in response to overhearing the first OBSS PPDU.

[0163] At operation 1520, the non-AP STA overhears a second OBSS PPDU in the primary channel of the BSS after the intra-BSS NAV has expired and while the basic NAV is active.

[0164] At operation 1525, the non-AP STA determines whether the second OBSS PPDU was transmitted by the same OBSS TXOP holder that transmitted the first OBSS PPDU. In an embodiment, the determining whether the second OBSS PPDU was transmitted by the same OBSS TXOP holder that transmitted the first OBSS PPDU is based on comparing a frame type, a frame subtype, and a BSS color associated with the second OBSS PPDU and the first OBSS PPDU.

[0165] If the second OBSS PPDU was not transmitted by the same OBSS TXOP holder that transmitted the first OBSS PPDU (e.g., the second OBSS PPDU was transmitted from a different BSS or was not transmitted by a TXOP holder) (and other NPCA operation conditions Docket No. 1002P25013W01Client Matter No. P25-013WO1are satisfied), the method may proceed to operation 1535, at which the non-AP STA switches from operating in the primary channel to operating in a NPCA primary channel of the BSS. In an embodiment, the switching from operating in the primary channel to operating in the NPCA primary channel is performed further in response to determining that the intra-BSS NAV is not active and that a duration associated with the second OBSS PPDU is longer than a NPCA operation threshold duration. After performing such NPCA channel switching, the non-AP STA may transmit and / or receive PPDUs in the NPCA primary channel (e.g., in the NPCA available channel that includes the NPCA primary channel). Returning to operation 1525, if the second OBSS PPDU was not transmitted by the same OBSS TXOP holder that transmitted the first OBSS PPDU, the method may proceed to operation 1530, at which the non-AP STA refrains from switching channels (remains operating in the primary channel) despite overhearing the second OBSS PPDU.

[0166] Although many of the solutions and techniques provided herein have been described with reference to a WLAN system, it should be understood that these solutions and techniques are also applicable to other network environments, such as cellular telecommunication networks, wired networks, etc. In some embodiments, the solutions and techniques provided herein may be or may be embodied in an article of manufacture in which a non-transitory machine-readable medium (such as microelectronic memory) has stored thereon instructions which program one or more data processing components (generically referred to here as a “processor” or “processing unit”) to perform the operations described herein. In other embodiments, some of these operations might be performed by specific hardware components that contain hardwired logic (e.g., dedicated digital filter blocks and state machines). Those operations might alternatively be performed by any combination of programmed data processing components and fixed hardwired circuit components.

[0167] In some cases, an embodiment may be an apparatus (e.g., an AP STA, a non-AP STA, or another network or computing device) that includes one or more hardware and software logic structures for performing one or more of the operations described herein. For example, as described herein, an apparatus may include a memory unit, which stores instructions that may be executed by a hardware processor installed in the apparatus. The apparatus may also include one or more other hardware or software elements, including a network interface, a display device, etc.

[0168] Some portions of the preceding detailed descriptions have been presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data Docket No. 1002P25013W01Client Matter No. P25-013WO1processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consi stent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

[0169] It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. The present disclosure can refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage systems.

[0170] The present disclosure also relates to an apparatus for performing the operations herein. This apparatus can be specially constructed for the intended purposes, or it can include a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. For example, a computer system or other data processing system may carry out the computer-implemented methods described herein in response to its processor executing a computer program (e.g., a sequence of instructions) contained in a memory or other non-transitory machine-readable storage medium. Such a computer program can be stored in a computer readable storage medium, such as, but not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, each coupled to a computer system bus.

[0171] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems can be used with programs in accordance with the teachings herein, or it can prove convenient to construct a more specialized apparatus to perform the method. The structure for a variety of these systems will appear as set forth in the description below. In addition, the present disclosure is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages can be used to implement the teachings of the disclosure as described herein.Docket No. 1002P25013W01Client Matter No. P25-013WO1

[0172] The present disclosure can be provided as a computer program product, or software, that can include a machine-readable medium having stored thereon instructions, which can be used to program a computer system (or other electronic devices) to perform a process according to the present disclosure. A machine-readable medium includes any mechanism for storing information in a form readable by a machine (e.g., a computer). In some embodiments, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium such as a read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory components, etc.

[0173] In the foregoing specification, embodiments of the disclosure have been described with reference to specific example embodiments thereof. It will be evident that various modifications can be made thereto without departing from the broader spirit and scope of embodiments of the disclosure as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.Docket No. 1002P25013W01Client Matter No. P25-013WO1

Claims

CLAIMSWhat is claimed is:

1. A method performed by a non-access point station (non-AP STA) that belongs to a basic service set (BSS) to perform non-primary channel access (NPCA), wherein the non-AP STA is capable of maintaining an intra-basic service set (intra-BSS) network allocation vector (NAV) and a basic NAV and, the method comprising:overhearing a first overlapping basic service set (OBSS) physical layer protocol data unit (PPDU) in a primary channel of the BSS; andswitching from operating in the primary channel of the BSS to operating in a NPCA primary channel of the BSS in response to overhearing the first OBSS PPDU despite the basic NAV being active.

2. The method of claim 1, further comprising:overhearing a second OBSS PPDU in the primary channel of the BSS; and refraining from switching channels despite overhearing the second OBSS PPDU in response to determining that the intra-BSS NAV is active.

3. The method of claim 2, further comprising:setting the basic NAV in response to overhearing the second OBSS PPDU; overhearing a third OBSS PPDU in the primary channel of the BSS after the intra-BSS NAV has expired and while the basic NAV is active; andrefraining from switching channels despite overhearing the third OBSS PPDU in response to determining that the third OBSS PPDU was transmitted by a same OBSS transmission opportunity (TXOP) holder that transmitted the second OBSS PPDU.

4. The method of claim 3, wherein the determining that the third OBSS PPDU was transmitted by the same OBSS TXOP holder that transmitted the second OBSS PPDU is based on comparing a frame type, a frame subtype, and a BSS color associated with the third OBSS PPDU and the second OBSS PPDU.

5. The method of claim 2, further comprising:setting the basic NAV in response to overhearing the second OBSS PPDU; overhearing a third OBSS PPDU in the primary channel of the BSS after the intra-BSS NAV has expired and while the basic NAV is active; andDocket No. 1002P25013W01Client Matter No. P25-013WO1switching from operating in the primary channel to operating in the NPCA primary channel in response to overhearing the third OBSS PPDU and determining that the third OBSS PPDU was transmitted from a different BSS than the second OBSS PPDU or that the second OBSS PPDU was not transmitted by a TXOP holder.

6. The method of claim 5, wherein the switching from operating in the primary channel to operating in the NPCA primary channel in response to overhearing the third OBSS PPDU is performed further in response to determining that the intra-BSS NAV is not active and that a duration associated with the first OBSS PPDU is longer than a NPCA operation threshold duration.

7. A wireless device configured to implement a non-access point station (non-AP STA) that is to belong to a basic service set (BSS), the wireless device comprising:a radio frequency transceiver;a memory device storing a set of instructions; anda processor coupled to the memory device, wherein the set of instructions, when executed by the processor, causes the non-AP STA to perform the method of any one of claims 1-6.

8. A non-transitory machine-readable medium having computer code stored therein, which when executed by a processor of a wireless device that implements a non-access point station (non-AP STA), causes the non-AP STA to perform the method of any one of claims 1-6.Docket No. 1002P25013W01Client Matter No. P25-013WO1

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