Signaling to allow overlapping basic service set (OBSS) transmission opportunity (TXOP) preemption

Abstract

Disclosed herein is a method performed by a sharing access point (AP) to allow a transmission opportunity (TXOP) held by the sharing AP to be preempted. The method includes transmitting a control frame, determining whether a response frame was received from at least one non-TXOP holder AP as a response to the control frame, and responsive to determining that the response frame was received from at least one non-TXOP holder AP, refraining from transmitting in the sharing AP's basic service set (BSS) to allow the TXOP to be preempted.

Description

SPECIFICATIONSIGNALING TO ALLOW OVERLAPPING BASIC SERVICE SET (OBSS) TRANSMISSION OPPORTUNITY (TXOP) PREEMPTIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 640,667, filed April 30, 2024, titled “Signaling for preemption request with TXOP sharing”, which is hereby incorporated by reference.TECHNICAL FIELD

[0002] The present disclosure generally relates to wireless communications, and more specifically, relates to signaling to allow overlapping basic service set (OBSS) transmission opportunity (TXOP) preemption.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. The IEEE 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] IEEE 802.1 Ibe, also known as “Wi-Fi 7”, is the next generation of the IEEE 802.11 family of standards for wireless local area networks. Currently under development, 802.1 Ibe aims to significantly improve upon the capabilities of its predecessor, 802.1 lax / Wi-Fi 6, by offering even higher data rates, lower latency, and increased reliability. The standard is expected to leverage advanced technologies such as multi-link operation (MLO), which allows devices to simultaneously use multiple frequency bands and channels for enhanced performance andreliability. Additionally, 802. l lbe will introduce 4096-QAM (Quadrature Amplitude Modulation), enabling higher data rates by encoding more bits per symbol. The standard will also feature improved medium access control (MAC) efficiency, enhanced power saving capabilities, and better support for high-density environments. With these advancements, 802.1 Ibe is expected to deliver theoretical maximum data rates of up to 46 gigabits per second (Gbps), making it suitable for bandwidth-intensive applications such as virtual and augmented reality, 8K video streaming, and high-performance gaming. The IEEE 802.1 Ibe standard is projected to be finalized by the end of 2024, paving the way for the next generation of Wi-Fi devices and networks.

[0005] The scope of future wireless networking standards (e.g., beyond IEEE 802.1 Ibe wireless networking standard) is expected to include schemes for supporting low latency (LL) traffic in different scenarios. LL traffic is traffic that needs to be transmitted with low latency (e.g., urgent traffic). LL traffic can be categorized into two types: periodic LL traffic and aperiodic (i.e., event-based) LL traffic. A multi-access point (AP) coordination scheme that divides / shares resource between APs (e.g., coordinated spatial reuse (C-SR), coordinated time division multiple access (C-TDMA), coordinated orthogonal frequency division multiple access (C-OFDMA), etc.) can be used to support periodic LL traffic. A preemption scheme can be used to support periodic LL traffic or aperiodic LL traffic. A preemption scheme may allow devices, including the transmission opportunity (TXOP) holder, to preempt the TXOP holder’s ongoing TXOP to support LL traffic. Existing preemption schemes are designed for a single basic service set (BSS) scenario (e.g., to support DL / UL (downlink / uplink) LL traffic during an UL / DL (uplink / downlink) TXOP). For example, when an AP is the TXOP holder, the downlink TXOP may be preempted to support uplink (UL) LL traffic. Also, when a non-AP STA is the TXOP holder, the uplink TXOP may be preempted to support downlink (DL) LL traffic.However, existing preemption schemes may not be able to support LL traffic that occurs at overlapping BSS (OBSS) devices (e.g., APs and / or non-AP stations (STAs) that belong to an OBSS with respect to the TXOP holder).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 3A 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 (CSMA / CA)-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.

[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 multi-basic service set (BSS) wireless network topology with multiple non-TXOP holder access points (APs), according to some embodiments.

[0018] Figure 11 is a diagram showing a frame exchange sequence where multiple non-TXOP holder APs participate in a channel contention mechanism to preempt a sharing AP's TXOP, according to some embodiments.

[0019] Figure 12 is a diagram showing a frame exchange sequence where a sharing AP maintains its TXOP because it does not receive a preemption indicator frame from a non-TXOP holder AP, according to some embodiments.

[0020] Figure 13 is a flow diagram of a method for allowing a TXOP to be preempted, according to some embodiments.

[0021] Figure 14 is a flow diagram of a method for preempting a TXOP, according to some embodiments.DETAILED DESCRIPTION

[0022] The present disclosure generally relates to wireless communications, and more specifically, relates to signaling to allow overlapping basic service set (OBSS) transmission opportunity (TXOP) preemption.

[0023] As mentioned above, existing preemption schemes are designed for a single basic service set (BSS) scenario and thus may not be able to support low latency traffic that occurs at OBSS devices (e.g., access points (APs) and / or non-AP stations (STAs) that belong to an OBSS with respect to the transmission opportunity (TXOP) holder).

[0024] The present disclosure introduces an OBSS TXOP preemption technique that allows OBSS devices to preempt a TXOP. The OBSS TXOP preemption technique described herein may be able to support low latency traffic that occurs at OBSS devices before the end of the current TXOP holder’s TXOP.

[0025] According to some embodiments, a sharing AP that holds a TXOP may transmit a control frame to invite any non-TXOP holder APs within its coverage area to request preemption of the sharing AP’s TXOP. As used herein, a sharing AP may be an AP that is willing to share a TXOP held by the AP with other APs. Any non-TXOP holder APs that receive the control frame may transmit a response frame to the sharing AP as a response to the control frame (e.g., after a short interframe space (SIFS) interval after receiving the control frame) if the non-TXOP holder AP wishes to preempt the sharing AP’s TXOP. The sharing AP may determine whether a response frame was received from at least one non-TXOP holder AP as a response to the control frame. If the sharing AP determines that it has received a response frame from at least one non-TXOP holder AP, the sharing AP may refrain from transmitting in the sharing AP’s BSS to allow the sharing AP’s TXOP to be preempted. Also, after transmitting the response frame, the non-TXOP holder APs that transmitted a response frame may participate in a channel contention mechanism to try to acquire the channel. The non-TXOP holder AP that is able to acquire the channel may transmit traffic in its own BSS, thereby preempting thesharing AP’s TXOP. If the sharing AP determines that it has not received a response frame as a response to the control frame (e.g., not received a response frame within a point coordination function interframe space (PIFS) interval after transmitting the control frame), the sharing AP may assume that there are no non-TXOP holder APs that wish to preempt the TXOP and maintain its TXOP by resuming / continuing transmission in the sharing AP’s BSS.

[0026] With the OBSS TXOP preemption technique described herein, a sharing AP may transmit a control frame to give non-TXOP holder APs an opportunity to preempt the sharing AP’s TXOP, if so desired. Non-TXOP holder APs that receive the control frame from the sharing AP and that wish to preempt the sharing AP’s TXOP may transmit response frames and participate in a channel contention mechanism. The non-TXOP holder AP that is able to acquire the channel after participating in the channel contention mechanism may preempt the sharing AP’s TXOP. The OBSS TXOP preemption technique described herein may be used to support low latency traffic that may occur in OBSSs (BSSs operated by non-TXOP holder APs) without having to wait until the end of the sharing AP’s TXOP.

[0027] 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.

[0028] 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 art 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.

[0029] 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 receivingwireless device may generate an RXVECTOR, which includes parameters of a received frame and is passed to a MAC layer for processing.

[0030] 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).

[0031] 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 104A (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.

[0032] 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.

[0033] 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.

[0034] 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 ofthe PHY layer. These functions may be performed in software, hardware, or a combination thereof according to an implementation.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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., asymbol) 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.

[0049] 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.

[0050] When the TxSP 324 performs a MIMO or MU-MIMO transmission, some blocks before the spatial mapper may be provided for each user.

[0051] 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.

[0052] 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.

[0053] 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 correspond to the receiving SPU 226, the RF receiver 244, and an antenna of the antenna unit 250 of Figure 2, respectively.

[0054] The RxSP 326 includes a GI remover 318, a Fourier transformer (FT) 316, a demapper 314, a deinterleaver 312, and a decoder 310.

[0055] 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.

[0056] 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.

[0057] 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 STBCdecoder for despreading the constellation points from the space-time streams into one or more spatial streams.

[0058] 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.

[0059] 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.

[0060] When the received transmission is the MIMO or MU-MIMO transmission, theRxSP 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.

[0061] 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.

[0062] 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 deparser 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.

[0063] 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.

[0064] 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 ofspace-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.

[0065] 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’ (AIF S [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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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 station 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.

[0074] 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.

[0075] 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 inresponse 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).

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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. An 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.

[0080] 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 variouscharacteristics of UHR (e.g., max PHY rate, PHY rate enhancement, bandwidth / number of spatial streams, and operating bands) are still to be determined.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 GHz band (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.

[0085] 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.

[0086] 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), andRepeated Legacy Signal Field (RL-SIG). These fields are used to maintain compatibility with older Wi-Fi standards.

[0087] 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.

[0088] Figure 7 provides a more detailed description of each field in the EHT PPDU frame, including their purposes and characteristics.

[0089] 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.

[0090] 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.

[0091] 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 modifications or newly defined mechanisms may be required to facilitate efficient and collision- free operation.

[0092] 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.

[0093] 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.

[0094] 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).

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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 subpacket. 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, subpacketswith corresponding SPIDs to be transmitted are in increasing order of SPID but can be exchanged / switched except for the first SPID.

[0103] 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 the IEEE 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.

[0104] In the context of coordinated TDMA (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.

[0105] The operation of various AP coordination schemes has been discussed in theIEEE 802.1 Ibe and UHR standards:

[0106] 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.

[0107] Coordinated OFDMA (C-OFDMA): APs transmit on orthogonal frequency resources by coordinating and splitting the spectrum, enabling more efficient spectrum utilization.

[0108] Joint Transmission (JTX): Multiple APs transmit jointly to a given user simultaneously by sharing data between the APs.

[0109] Coordinated Spatial Reuse (C-SR): Multiple APs or STAs adjust their transmit power to reduce interference between APs.

[0110] By implementing these AP coordination schemes, WLAN systems can improve their overall throughput and efficiency by leveraging the cooperation between multiple APs.

[0111] Figure 10 is a diagram showing a multi-BSS wireless network topology with multiple non-TXOP holder APs, according to some embodiments.

[0112] As shown in the diagram, the multi-BSS wireless network may include a first AP (“API”), a second AP (“AP2”), a third AP (“AP3”), a first STA (“STA1”), a second STA (“STA2”), and a third STA (“STA3”). API may operate a first BSS (“BSS1”), AP2 may operate a second BSS (“BSS2”), and AP3 may operate a third BSS (“BSS3”). As shown in the diagram, the coverage area of BSS1 may overlap with the coverage areas of BSS2 and BSS3.BSS1 and BSS2 may be OBSSs with respect to each other (and vice versa). Also, BSS1 and BSS3 may be OBSSs with respect to each other (and vice versa). STA1 may be associated with API and belong to BSS1. STA2 may be associated with AP2 and belong to BSS2. STA3 may be associated with AP3 and belong to BSS3. In this example, it is assumed that API is the TXOP holder (and sharing AP) and that AP2 and AP3 are non-TXOP holder APs.

[0113] API may use its obtained TXOP without constraints. API may request stream classification service (SCS) information from AP2 and AP3 when it becomes the TXOP holder. AP2 and AP3 may provide SCS information to API. The SCS information may include information regarding the quality of service (QoS) characteristics for time-sensitive network flows (e.g., indicating the urgency level of low latency traffic). API may decide to allocate a portion of its obtained TXOP to AP2 and then to AP3 (in that order) based on the SCS information (e.g., if the SCS information indicates that AP2 has more urgent traffic to transmit than AP3). API may decide to allocate a duration of “A” to AP2 (the TXOP sharing duration is “A”). However, before API shares its TXOP with AP2, API may check whether there are any non-TXOP holder APs within its coverage area that have more urgent aperiodic low latency traffic to transmit. API may accomplish this by transmitting a TXOP sharing (TXS) control frame that includes a preemption (PR) enabled indicator. Such frame may be referred to herein as a TXS(+PR) frame. API may include an indication of TXOP sharing duration “A” in the TXOP sharing control frame. The sharing AP may broadcast the TXOP sharing control frame. Non-TXOP holder APs that receive the TXOP sharing control frame and that wish to preempt the sharing AP’s TXOP may transmit a preemption indicator frame to the sharing AP as a response to the TXOP sharing control frame and then participate in a channel contention mechanism to try to acquire the channel. The non-TXOP that is able to acquire the channel after participating in the channel contention mechanism may start transmitting in its own BSS, thereby preempting the sharing AP’s TXOP. The PR enabled indication included in the TXOP sharing control frame may have the function of indirectly asking whether a non-TXOP holder AP wishes to preempt the sharing AP’s TXOP. In this sense, the TXOP sharing control frame can be viewed as a “polling” frame that polls non-TXOP holder APs regarding their interest in preempting the sharing AP’s TXOP.

[0114] Figure 11 is a diagram showing a frame exchange sequence where multiple non- TXOP holder APs participate in a channel contention mechanism to preempt a sharing AP’s TXOP, according to some embodiments. The frame exchange may involve API (which is a sharing AP in this example), AP2 (which is a non-TXOP holder AP in this example), AP3(which is also a non-TXOP holder AP in this example), STA1 (which is associated with API), and STA3 (which is associated with AP3).

[0115] As shown in the diagram, API may transmit a RTS frame 1105 to STA1 and STA1 may respond by transmitting a CTS frame 1110 to API. API is the TXOP holder and sharing AP in this example. During API’s TXOP, API may transmit PPDU 1115 to STA1 and STA1 may respond by transmitting BA frame 1120 to API .

[0116] API may then transmit a TXS(+PR) frame 1125 as a broadcast frame. As previously mentioned, the TXS(+PR) frame 1125 may be a TXOP sharing control frame that includes a preemption enabled indicator. In an embodiment, the preemption enabled indicator is included in the UHR SIG (ultra-high reliability signal) field included in the preamble of the TXS(+PR) frame 1125 (e.g., in a reserved field included in the UHR SIG field). In an embodiment, the preemption enabled indicator is included in an aggregated control (A-control) field included in the TXS(+PR) frame 1125 (e.g., within a new type of control field within an A-control field). While two example locations of where the preemption enabled indicator can be located are mentioned, it should be appreciated that the preemption enabled indicator can be included in other parts of the TXS(+PR) frame 1125. The preemption enabled indicator included in the TXS(+PR) frame 1125 may have the function of inviting any non-TXOP holder APs (e.g., AP2 and AP3) to transmit a preemption indicator frame if they wish to preempt API’s TXOP. The TXS(+PR) frame 1125 may include an indication of a TXOP sharing duration (“allocated duration for preemption” shown in the diagram).

[0117] Responsive to receiving TXS(+PR) frame 1125 from API, AP2 and AP3 may transmit preemption indicator frames to API if they wish to preempt API’s TXOP. In this example, it is assumed that AP2 and AP3 wish to preempt API’s TXOP (e.g., because they have low latency traffic to transmit) so they each transmit a preemption indicator frame to sharing API as a response to the TXS(+PR) frame 1125. For example, as shown in the diagram, AP2 may transmit preemption indicator (PRI) frame 1130 to API and AP3 may transmit preemption indicator frame 1135 to API. Preemption indicator frame 1130 and preemption indicator frame 1135 may be transmitted simultaneously (e.g., be a MU transmission). Responsive to receiving the preemption indicator frames, API may refrain from resuming transmission in its own BSS (BSS1) to allow a non-TXOP holder AP to preempt the TXOP. After transmitting their respective preemption indicator frames, AP2 and AP3 may participate in a channel contention mechanism to try to acquire the channel. For example, AP2 and AP3 may perform an enhanced distributed channel access (EDCA) backoff procedure. The non-TXOP holder AP that is able to acquire the channel after participating in the channel contention mechanism maystart transmitting traffic in its own BSS. In the example shown in the diagram, it is assumed that AP3 is able to acquire the channel after participating in the channel contention mechanism and thus AP3 may transmit PPDU 1140 (which may include low latency data) to STA3 (thereby preempting API’s TXOP) and STA3 may respond by transmitting BA frame 1145 to AP3 (in BSS3). AP3 may determine the TXOP sharing duration (how long AP3 is allowed to preempt API’s TXOP for) based on information included in the TXS(+PR) frame 1125 and may utilize API’s TXOP for the TXOP sharing duration. When the TXOP sharing duration is over, API may resume transmission in its own BSS (BSS1). For example, as shown in the diagram, when the TXOP sharing duration is over, API may transmit PPDU 1150 to STA1 and STA1 may respond by transmitting BA frame 1155 to API.

[0118] In an embodiment, API determines the TXOP sharing duration based on SCS information (or other information regarding the urgency level of the traffic) of a non-TXOP holder AP. If API does not have SCS information of non-TXOP holder APs or otherwise does not have sufficient information regarding the traffic that non-TXOP holder APs wish to transmit, API may determine the TXOP sharing duration by itself.

[0119] If API does not receive any preemption indicator frames from non-TXOP holder APs as a response to the TXS(+PR) frame 1125, API may maintain its TXOP (keep transmitting in its own BSS (BSS1)). An example frame exchange sequence in which this occurs is shown in Figure 12 and described in connection thereto.

[0120] Figure 12 is a diagram showing a frame exchange sequence where a sharing AP maintains its TXOP because it does not receive a preemption indicator frame from a non-TXOP holder AP, according to some embodiments. The frame exchange may involve API (which is a sharing AP in this example), AP2 (which is a non-TXOP holder AP in this example), AP3 (which is also a non-TXOP holder AP in this example), STA1 (which is associated with API), and STA3 (which is associated with AP3).

[0121] As shown in the diagram, API may transmit a RTS frame 1205 to STA1 and STA1 may respond by transmitting a CTS frame 1210 to API. API is the TXOP holder and sharing AP in this example. During API’s TXOP, API may transmit PPDU 1215 to STA1 and STA1 may respond by transmitting BA frame 1220 to API.

[0122] API may then transmit a TXS(+PR) frame 1225 as a broadcast frame. The preemption enabled indicator included in the TXS(+PR) frame 1125 may have the function of inviting any non-TXOP holder APs (e.g., AP2 and AP3) to transmit a preemption indicator frame if they wish to preempt API’s TXOP. The TXS(+PR) frame 1125 may include an indication of TXOP sharing duration.

[0123] Responsive to receiving TXS(+PR) frame 1225 from API, AP2 and AP3 may transmit preemption indicator frames to API after a short interframe space (SIFS) interval after receiving the TXS(+PR) frame 1225 if they wish to preempt API’s TXOP. In this example, it is assumed that AP2 and AP3 do not wish to preempt API’s TXOP (e.g., because they do not have low latency traffic to transmit) so AP2 and AP3 do not transmit a preemption indicator frame. API may recognize that there are no non-TXOP holder APs that wish to preempt the TXOP if it does not receive a preemption indicator frame within a SIFS interval after transmitting the TXS(+PR) frame 1225. In this example, it is assumed that API recognizes that there are no non-TXOP holder APs that wish to preempt the TXOP so API may maintain its TXOP, for example, by transmitting PPDU 1230 to STA1 after a PIFS interval after transmitting the TXS(+PR) frame 1225. STA1 may respond by transmitting BA frame 1235 to API. API may continue utilizing the TXOP until the total TXOP duration acquired by API is over. For example, API may transmit PPDU 1240 to STA1 and STA1 may respond by transmitting BA frame 1245 to API, after which the total TXOP duration is over.

[0124] More generally, with the OBSS TXOP preemption technique described herein, a sharing AP may transmit a control frame (e.g., TXS(+PR) frame) to give non-TXOP holder APs an opportunity to preempt the sharing AP’s TXOP, if so desired. Non-TXOP holder APs that receive the control frame from the sharing AP and that wish to preempt the sharing AP’s TXOP may transmit a response frame (e.g., preemption indicator frame) after a first interframe space (IFS) interval after receiving the control frame and participate in a channel contention mechanism. The non-TXOP holder AP that is able to acquire the channel after participating in the channel contention mechanism may preempt the sharing AP’s TXOP by starting to transmit in its own BSS. If the sharing AP does not receive any response frames from non-TXOP holder APs, the sharing AP may maintain the sharing AP’s TXOP by starting to transmit in its own BSS after a second IFS interval after transmitting the control frame, where the second IFS interval is longer than the first IFS interval. For example, the first IFS interval may be a SIFS interval and the second IFS interval may be a PIFS interval, although it should be appreciated that other intervals / lengths can be used. The OBSS TXOP preemption technique described herein may be used to support low latency traffic that may occur in OBSSs (BSSs operated by non-TXOP holder APs) without having to wait until the end of the sharing AP’s TXOP.

[0125] The control frame transmitted by the sharing AP may be viewed as frame that indicates the sharing AP’s intention to share its TXOP with a non-TXOP holder AP and that also “polls” non-TXOP holder APs regarding their interest in preempting the sharing AP’s TXOP. Non-TXOP holder APs that receive the control frame may transmit a response frame to thesharing AP to indicate their desire to preempt the sharing AP’s TXOP. The non-TXOP holder APs that transmit a response frame to the sharing AP may participate in a channel contention mechanism after transmitting their response frames to try to acquire the channel. The non- TXOP holder AP that is able to acquire the channel may start transmitting in its own BSS, thereby preempting the sharing AP’s TXOP. If the sharing AP does not receive any response frames from non-TXOP holder APs, the sharing AP may assume that there are no non-TXOP holder APs that wish to preempt the sharing AP’s TXOP and resume transmitting in its own BSS. In an embodiment, the control frame is a TXOP sharing control frame (e.g., that includes a preemption enabled indicator) and the response frame is a preemption indicator frame. In another embodiment, the control frame is a polling announcement frame and the response frame is a multi-station block acknowledgement (M-BA) frame.

[0126] Turning now to Figure 13, a method 1300 will be described for allowing a TXOP to be preempted, in accordance with an example embodiment. The method 1300 may be performed by a sharing AP. The sharing AP may be implemented by a wireless device (e.g., wireless device 104).

[0127] Additionally, although shown in a particular order, in some embodiments the operations of the method 1300 (and the other methods shown in the other figures) may be performed in a different order. For example, although the operations of the method 1300 are shown in a sequential order, some of the operations may be performed in partially or entirely overlapping time periods.

[0128] At operation 1305, the sharing AP transmits a control frame. In an embodiment, the control frame includes a preemption enabled indicator (e.g., indicating the sharing AP’s intention to share its TXOP with a non-TXOP holder AP). In an embodiment, the preemption enabled indicator is included in a UHR-SIG field included in a preamble of the control frame. In an embodiment, the preemption enabled indicator is included in an A-control field included in the control frame. In an embodiment, the control frame is broadcasted (the control frame is a broadcasted frame). In an embodiment, the control frame includes an indication of a TXOP sharing duration. In an embodiment, the TXOP sharing duration is determined based on SCS information obtained from a non-TXOP holder AP.

[0129] At operation 1310, the sharing AP determines whether a response frame was received from at least one non-TXOP holder AP. If a response frame was received from at least one non-TXOP holder AP, the method may proceed to operation 1320. Otherwise, if a response frame was not received from at least one non-TXOP holder AP, the method may proceed to operation 1315 at which the sharing AP starts to transmit in the sharing AP’s BSS. In anembodiment, the sharing AP starts to transmit in the sharing AP’s BSS after a first IFS interval after transmitting the control frame, wherein the first IFS interval is longer than a second IFS interval used by non-TXOP holder APs to transmit response frames after receiving the control frame. In an embodiment, the first IFS interval is a PIFS interval and the second IFS interval is a SIFS interval.

[0130] At operation 1320, the sharing AP refrains from transmitting in the sharing AP’s BSS to allow the TXOP to be preempted.

[0131] In an embodiment, at operation 1325, the sharing AP starts to transmit in the sharing AP’s BSS after the TXOP has been preempted for a TXOP sharing duration.

[0132] In an embodiment, the control frame is a TXOP sharing control frame and the response frame is a preemption indicator frame. In another embodiment, the control frame is a polling announcement frame and the response frame is a M-BA frame.

[0133] Turning now to Figure 14, a method 1400 will be described for preempting a TXOP, in accordance with an example embodiment. The method 1400 may be performed by a non- TXOP holder AP. The non-TXOP holder AP may be implemented by a wireless device (e.g., wireless device 104).

[0134] At operation 1405, the non-TXOP holder AP receives a control frame from a sharing AP. In an embodiment, the control frame includes a preemption enabled indicator (e.g., indicating the sharing AP’s intention to share its TXOP with a non-TXOP holder AP). In an embodiment, the preemption enabled indicator is included in a UHR-SIG field included in a preamble of the control frame. In an embodiment, the preemption enabled indicator is included in an A-control field included in the control frame. In an embodiment, the control frame is broadcasted (the control frame is a broadcasted frame). In an embodiment, the control frame includes an indication of a TXOP sharing duration.

[0135] At operation 1410, the non-TXOP holder AP determines it wishes to preempt the sharing AP’s TXOP. If the non-TXOP holder AP wishes to preempt the TXOP, the method may proceed to operation 1420. Otherwise, if the non-TXOP holder AP does not wish to preempt the TXOP, the method may proceed to operation 1415 at which the non-TXOP holder AP does not transmit a response frame to the sharing AP.

[0136] At operation 1420, the non-TXOP holder AP transmits a response frame to the sharing AP to indicate that the non-TXOP holder AP wishes to preempt the TXOP. In an embodiment, the response frame is transmitted to the sharing AP after a first IFS interval after receiving the control frame, wherein the first IFS interval is shorter than a second IFS interval used by the sharing AP to start transmitting in the sharing AP’s BSS after transmitting thecontrol frame. In an embodiment, the first IFS interval is a SIFS interval and the second IFS interval is a PIFS interval.

[0137] At operation 1425, after transmitting the response frame, the non-TXOP holder AP participates in a channel contention mechanism to try to acquire a channel.

[0138] At operation 1430, the non-TXOP holder AP transmits traffic in the non-TXOP holder AP’s BSS after participating in the channel contention mechanism (if the non-TXOP holder isa able to acquire the channel), thereby preempting the sharing AP’s TXOP. In an embodiment, the non-TXOP holder AP preempts the TXOP for the TXOP sharing duration.

[0139] In an embodiment, the control frame is a TXOP sharing control frame and the response frame is a preemption indicator frame. In an alternative embodiment, the control frame is a polling announcement frame and the response frame is a M-BA frame.

[0140] 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.

[0141] 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.

[0142] 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 processing 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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 beused 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.

[0147] 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.

Claims

CLAIMSWhat is claimed is:

1. A method performed by a sharing access point (AP) to allow a transmission opportunity (TXOP) held by the sharing AP to be preempted, the method comprising: transmitting a control frame; determining whether a response frame was received from at least one non-TXOP holder AP as a response to the control frame; and responsive to determining that the response frame was received from at least one non- TXOP holder AP, refraining from transmitting in the sharing AP’s basic service set (BSS) to allow the TXOP to be preempted.

2. The method of claim 1, wherein the control frame includes a preemption enabled indicator.

3. The method of claim 2, wherein the preemption enabled indicator is included in an ultra high reliability signal (UHR-SIG) field included in a preamble of the control frame.

4. The method of claim 2, wherein the preemption enabled indicator is included in an aggregated control (A-control) field included in the control frame.

5. The method of claim 1, wherein the control frame is a broadcasted.

6. The method of claim 1, wherein the control frame includes an indication of a TXOP sharing duration.

7. The method of claim 6, further comprising: starting to transmit in the sharing AP’s BSS after the TXOP has been preempted for the TXOP sharing duration.

8. The method of claim 6, wherein the TXOP sharing duration is determined based on stream classification service (SCS) information obtained from a non-TXOP holder AP.

9. The method of claim 1, wherein if the sharing AP determines that the response frame was not received from at least one non-TXOP holder AP, the sharing AP starts to transmit in the sharing AP’s BSS.

10. The method of claim 9, wherein the sharing AP starts to transmit in the sharing AP’s BSS after a first interframe space (IFS) interval after transmitting the control frame, wherein the first IFS interval is longer than a second IFS interval used by non-TXOP holder APs to transmit response frames after receiving the control frame.

11. The method of claim 10, wherein the first IFS interval is a point coordination function IFS (PIFS) interval and the second IFS interval is a short IFS (SIFS) interval.

12. The method of claim 1, wherein the control frame is a TXOP sharing control frame and the response frame is a preemption indicator frame.

13. The method of claim 1, wherein the control frame is a polling announcement frame and the response frame is a multi-station block acknowledgement (M-BA) frame.

14. A method performed by a non-transmission opportunity holder access point (non-TXOP holder AP) to preempt a transmission opportunity (TXOP) held by a sharing AP, the method comprising: receiving a control frame from a sharing AP; responsive to receiving the control frame, transmitting a response frame to the sharing AP to indicate that the non-TXOP holder AP wishes to preempt the TXOP; after transmitting the response frame, participating in a channel contention mechanism to try to acquire a channel; and transmitting traffic in the non-TXOP holder AP’s basic service set (BSS) after participating in the channel contention mechanism.

15. The method of claim 14, wherein the control frame includes a preemption enabled indicator.

16. The method of claim 15, wherein the preemption enabled indicator is included in an ultra high reliability signal (UHR-SIG) field included in a preamble of the control frame.

17. The method of claim 15, wherein the preemption enabled indicator is included in an aggregated control (A-control) field included in the control frame.

18. The method of claim 14, wherein the control frame is broadcasted.

19. The method of claim 14, wherein the control frame includes an indication of a TXOP sharing duration.

20. The method of claim 19, wherein the non-TXOP holder AP preempts the TXOP for the TXOP sharing duration.

21. The method of claim 14, wherein the response frame is transmitted to the sharing AP after a first interframe space (IFS) interval after receiving the control frame, wherein the first interframe space (IFS) interval is shorter than a second IFS interval used by the sharing AP to start transmitting in the sharing AP’s BSS after transmitting the control frame.

22. The method of claim 21, wherein the first IFS interval is a short IFS (SIFS) interval and the second IFS interval is a point coordination function IFS (PIFS) interval.

23. The method of claim 14, wherein the control frame is a TXOP sharing control frame and the response frame is a preemption indicator frame.

24. The method of claim 14, wherein the control frame is a polling announcement frame and the response frame is a multi-station block acknowledgement (M-BA) frame.

25. A wireless device to implement a sharing access point (AP), the wireless device comprising: a radio frequency transceiver; a memory device storing a set of instructions; and a processor coupled to the memory device, wherein the set of instructions, when executed by the processor, causes the sharing AP to perform the method of any one of claims 1-13.

26. A wireless device to implement a non-transmission opportunity holder access point (non- TXOP holder AP), the wireless device comprising: a radio frequency transceiver; a memory device storing a set of instructions; and a processor coupled to the memory device, wherein the set of instructions, when executed by the processor, causes the non-TXOP holder AP to perform the method of any one of claims 14-24.

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