Returning and resuming a transmission opportunity (TXOP) in coordinated time division multiple access (c-TDMA)

Abstract

A method performed by a sharing access point (AP) that belongs to a first basic service set (BSS) to resume a transmission opportunity (TXOP) that was shared by the sharing AP with a shared AP that belongs to a second BSS. The method includes detecting a TXOP return indicator in a frame exchange sequence in the second BSS during the TXOP, responsive to detecting the TXOP return indicator in the frame exchange sequence in the second BSS, performing a carrier sense of a channel after the frame exchange sequence in the second BSS to determine whether the channel is idle or busy, and responsive to determining that the channel is idle, starting a second frame exchange sequence in the first BSS after a first interframe space (IFS) interval after the frame exchange sequence in the second BSS.

Description

SPECIFICATIONRETURNING AND RESUMING A TRANSMISSION OPPORTUNITY (TXOP) IN COORDINATED TIME DIVISION MULTIPLE ACCESS (C-TDMA)CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 636,644, filed April 19, 2024, titled “Indication of returning TXOP in coordinated time division multiple access (C-TDMA)”, and U.S. Provisional Application No. 63 / 637,626, filed April 23, 2024, titled “Indication of returning TXOP in coordinated time division multiple access (C-TDMA)”, which are hereby incorporated by reference.TECHNICAL FIELD

[0002] The present disclosure generally relates to wireless communications, and more specifically, relates to returning and resuming a transmission opportunity in a coordinated time division multiple access (C-TDMA) scenario.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 expectedto leverage advanced technologies such as multi-link operation (MLO), which allows devices to simultaneously use multiple frequency bands and channels for enhanced performance and reliability. 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 various multi-AP schemes such as coordinated time division multiple access (C-TDMA), coordinated orthogonal frequency division multiple access (C-OFDMA), coordinated beamforming (C-BF), coordinated nulling, and joint transmission (JTX) to increase spectral efficiency in high density network scenarios. In the current IEEE 802.11 wireless networking standard, after a sharing AP shares its transmission opportunity (TXOP) with a shared AP (e.g., as part of C-TDMA), the shared AP may wish to return the TXOP back to the sharing AP (e.g., so that the sharing AP can use the remaining portion of the TXOP) if the shared AP does not have any more data to transmit during the TXOP. The shared AP may try to notify the sharing AP of the shared AP’s intention to return the TXOP back to the sharing AP. However, the sharing AP may not be able to receive the notification due to interference from overlapping basic service set (OBSS) stations STAs (e.g., third-party STAs). To address this problem, a new mechanism for allowing a shared AP to return the remaining portion of a shared TXOP back to the sharing AP is needed.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 stream classification service (SCS) information exchange, according to some embodiments.

[0018] Figure 11 is a diagram showing a combination of Case 1 and Case A, according to some embodiments.

[0019] Figure 12 is a diagram showing a combination of Case 2 and Case D, according to some embodiments.

[0020] Figure 13 is a diagram showing a combination of Case 3 and Case B, according to some embodiments.

[0021] Figure 14 is a diagram showing a combination of Case 3 and Case C, according to some embodiments.

[0022] Figure 15 is a diagram showing a combination of Case 4 and Case E, according to some embodiments.

[0023] Figure 16 is a diagram showing a combination of Case 4 and Case G, according to some embodiments.

[0024] Figure 17 is a diagram showing a combination of Case 4 and Case F, according to some embodiments.

[0025] Figure 18 is a diagram showing a combination of Case 5 and Case E, according to some embodiments.

[0026] Figure 19 is a diagram showing a combination of Case 5 and Case F, according to some embodiments.

[0027] Figure 20 is a diagram showing a combination of Case 4 and Case F followed by a combination of Case 1 and Case A, according to some embodiments.

[0028] Figure 21 is a flow diagram of a method for resuming a TXOP, according to some embodiments.

[0029] Figure 22 is a flow diagram of a method for returning a TXOP, according to some embodiments.

[0030] Figure 23 is a flow diagram of a method for not resuming a TXOP, according to some embodiments.

[0031] Figure 24 is a flow diagram of a method for maintaining a TXOP, according to some embodiments.DETAILED DESCRIPTION

[0032] The present disclosure generally relates to wireless communications, and more specifically, relates to techniques for returning and resuming a transmission opportunity (TXOP) in a coordinated time division multiple access (C-TDMA) scenario.

[0033] The present disclosure describes techniques that allow a shared AP to efficiently return the remaining portion of a TXOP that was shared by the sharing AP with the shared AP back to the sharing AP. The shared AP may provide multiple opportunities for the sharing AP to resume the TXOP. The use of the techniques described herein may allow the sharing AP to resume the TXOP if the sharing AP has data (e.g., urgent data) to transmit during the TXOP, which allows the TXOP to be used more efficiently.

[0034] According to some embodiments, a sharing AP may share a portion of its TXOP with a shared AP using C-TDMA techniques. As used herein, a sharing AP may be an AP that originally holds the TXOP and that shares the TXOP with a shared AP (e.g., allocates a portionof the TXOP for the shared AP to use). As used herein, a sharing AP may be an AP that the sharing AP shares its TXOP with. In a C-TDMA TXOP sharing scenario, the shared AP may temporarily become the TXOP holder (although the sharing AP is the original TXOP holder). Thus, during the TXOP, the shared AP and STAs that belong to the shared AP’s BSS may perform a frame exchange sequence in the shared AP’s BSS. The shared AP and / or the STAs that belong to the shared AP’s BSS may add a TXOP return indicator in the frame exchange sequence to indicate that they are willing to return the remaining portion of the TXOP back to the sharing AP. If the sharing AP detects the TXOP return indicator in the frame exchange sequence in the shared AP’s BSS (e.g., by overhearing the transmissions in the second BSS), the sharing AP may perform a carrier sense of the channel after the frame exchange sequence in the shared AP’s BSS to determine whether the channel is idle or busy. If the channel is idle and the sharing AP wishes to resume the TXOP (e.g., because the sharing AP has urgent data to transmit), the sharing AP may transmit a response frame to the shared AP after a first interframe space (IFS) interval (e.g., a short interframe space (SIFS) interval) after the frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator) to indicate that the sharing AP wishes to resume the TXOP. The sharing AP may then start a frame exchange sequence in the sharing AP’s BSS after transmitting the response frame to the shared AP. Otherwise, if the channel is busy or the sharing AP does not wish to resume the TXOP, the sharing AP may do nothing. The shared AP may also perform a carrier sense of the channel after the frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator) to determine whether the channel is idle or busy. If the channel is idle and the shared AP wishes to maintain the TXOP (e.g., because the shared AP has additional data to transmit), the shared AP may start a new frame exchange sequence in the shared AP’s BSS after a second IFS interval (e.g., a point coordination function interframe space (PIFS) interval) after the previous frame exchange sequence in the shared AP’s BSS. The second IFS interval may be longer than the first IFS interval (that is used by the sharing AP) to give transmission priority to the sharing AP. However, if the channel is busy or the shared AP does not wish to maintain the TXOP, the shared AP may refrain from resuming transmission in the shared AP’s BSS to return the TXOP to the sharing AP.

[0035] According to some embodiments, a sharing AP may share a portion of its TXOP with a shared AP. In this case, the shared AP temporarily becomes the TXOP holder (although the sharing AP is the original TXOP holder). During the TXOP, the shared AP and STAs that belong to the shared AP’s BSS may perform a frame exchange sequence in the shared AP’s BSS. The shared AP and / or the STAs that belong to the shared AP’s BSS may add a TXOPreturn indicator in the frame exchange sequence to indicate that they are willing to return the remaining portion of the TXOP back to the sharing AP. If the sharing AP detects the TXOP return indicator in the frame exchange sequence in the shared AP’s BSS (e.g., by overhearing the transmissions in the second BSS), the sharing AP may perform a carrier sense of the channel after the frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator) to determine whether the channel is idle or busy. If the channel is idle and the sharing AP wishes to resume the TXOP (e.g., because the sharing AP has urgent data to transmit), the sharing AP may start a frame exchange sequence in the sharing AP’s BSS after a first IFS interval (e.g., a SIFS interval) after the frame exchange sequence in the shared AP’s BSS. Otherwise, if the channel is busy or the sharing AP does not wish to resume the TXOP, the sharing AP may do nothing. The shared AP may also perform a carrier sense of the channel after the frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator) to determine whether the channel is idle or busy. If the channel is idle and the shared AP wishes to maintain the TXOP (e.g., because the shared AP has additional data to transmit), the shared AP may start a new frame exchange sequence in the shared AP’s BSS after a second IFS interval (e.g., a PIFS interval) after the previous frame exchange sequence in the shared AP’s BSS. The second IFS interval may be longer than the first IFS interval (that is used by the sharing AP) to give transmission priority to the sharing AP. However, if the channel is busy or the shared AP does not wish to maintain the TXOP, the shared AP may refrain from resuming transmission in the shared AP’s BSS to return the TXOP to the sharing AP.

[0036] According to some embodiments, a sharing AP may share a portion of its TXOP with a shared AP. In this case, the shared AP temporarily becomes the TXOP holder (although the sharing AP is the original TXOP holder). During the TXOP, the shared AP and STAs that belong to the shared AP’s BSS may perform a frame exchange sequence in the shared AP’s BSS. The shared AP and / or the STAs that belong to the shared AP’s BSS may add a TXOP return indicator in the frame exchange sequence to indicate that they are willing to return the remaining portion of the TXOP back to the sharing AP. If the sharing AP detects the TXOP return indicator in the frame exchange sequence in the shared AP’s BSS (e.g., by overhearing the transmissions in the second BSS), the sharing AP may perform a carrier sense of the channel after the frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator) to determine whether the channel is idle or busy. If the channel is idle and the sharing AP does not wish to resume the TXOP, the sharing AP may transmit a response frame to the shared AP after a first IFS interval (e.g., a short interframe space (SIFS) interval) after the frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator) to indicatethat the sharing AP does not wish to resume the TXOP. The shared AP may also perform a carrier sense of the channel after the frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator) to determine whether the channel is idle or busy. If the channel is idle and the shared AP wishes to maintain the TXOP (e.g., because the shared AP has additional data to transmit), the shared AP may start a new frame exchange sequence in the shared AP’s BSS after a second IFS interval (e.g., a PIFS interval) after the previous frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator).However, if the channel is busy, the shared AP may refrain from resuming transmission in the shared AP’s BSS. After the frame exchange sequence in the shared AP’s BSS (that included the TXOP return indicator), the shared AP may determine whether it has received a response frame from the sharing AP indicating that the sharing AP does not wish to resume the TXOP. If the shared AP received the response frame from the sharing AP, the shared AP may perform a carrier sense of the channel after receiving the response frame to determine whether the channel is idle or busy. If the channel is idle and the shared AP wishes to maintain the TXOP, the shared AP may start a new frame exchange sequence in the shared AP’s BSS after receiving the response frame. If the shared AP does not wish to maintain the TXOP, the shared AP may refrain from transmitting in the shared AP’s BSS after receiving the response frame from the sharing AP.

[0037] 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.

[0038] 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.

[0039] 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 104may 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.

[0040] 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).

[0041] 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.

[0042] 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.

[0043] 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, theMAC 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 theWLAN 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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 streamsto transmit chains. The spatial mapper may use direct mapping, spatial expansion, or beamforming.

[0058] 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.

[0059] 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.

[0060] When the TxSP 324 performs a MIMO or MU-MIMO transmission, some blocks before the spatial mapper may be provided for each user.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] The RxSP 326 includes a GI remover 318, a Fourier transformer (FT) 316, a demapper 314, a deinterleaver 312, and a decoder 310.

[0065] 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.

[0066] 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.

[0067] When the received transmission is the MIMO or MU-MIMO transmission, theRxSP 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] The PHY entity for IEEE 802.11 is based on Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). In eitherOFDM 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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., AIFSfAC]) 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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).

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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 inFigure 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] Figure 7 provides a more detailed description of each field in the EHT PPDU frame, including their purposes and characteristics.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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).

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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 andreduced latency, the wireless network system can evolve toward a hybrid ARQ (HARQ) approach.

[0110] 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.

[0111] 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.

[0112] 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, subpackets with corresponding SPIDs to be transmitted are in increasing order of SPID but can be exchanged / switched except for the first SPID.

[0113] 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.

[0114] 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.

[0115] The operation of various AP coordination schemes has been discussed in the IEEE 802.1 Ibe and UHR standards:

[0116] 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.

[0117] Coordinated OFDMA (C-OFDMA): APs transmit on orthogonal frequency resources by coordinating and splitting the spectrum, enabling more efficient spectrum utilization.

[0118] Joint Transmission (JTX): Multiple APs transmit jointly to a given user simultaneously by sharing data between the APs.

[0119] Coordinated Spatial Reuse (C-SR): Multiple APs or STAs adjust their transmit power to reduce interference between APs.

[0120] By implementing these AP coordination schemes, WLAN systems can improve their overall throughput and efficiency by leveraging the cooperation between multiple APs.

[0121] In future wireless networks (e.g., beyond 802.1 Ibe wireless networks (e.g., “UHR”)), the concept of TXOP sharing is expected to expand from TXOP sharing within a single BSS to TXOP sharing between multiple BSSs (e.g., C-TDMA). For example, a sharing AP may share a portion of its TXOP with a shared AP. This may allow the shared AP to transmit data without having to wait until the sharing AP’s TXOP is over (e.g., which may be useful if the shared AP has data that needs to be transmitted urgently). According to existing TXOP rules (e.g., definedby existing IEEE 802.11 wireless networking standards), non-TXOP holder STAs must wait until the TXOP holder STA’s TXOP is over to transmit data. Also, the non-TXOP holder STAs are not guaranteed to obtain a TXOP after the TXOP holder STA’s TXOP is over even if the non-TXOP holder STAs have data that needs to be transmitted urgently. With C-TDMA, when the shared AP has data that needs to be transmitted urgently, the sharing AP may allocate a portion of its TXOP to the shared AP to allow the shared AP to transmit data.

[0122] During its allocated portion of the TXOP, the shared AP may determine that it no longer needs the TXOP (e.g., because it has no more data to transmit in its BSS) and try to return the remaining portion of the TXOP back to the sharing AP.

[0123] Before performing C-TDMA, the sharing AP may collect stream classification service (SCS) information from candidate APs (candidate APs to become shared APs). The SCS information for a candidate AP may include quality of service (QoS) information to support low latency traffic within the candidate AP’s own BSS. If an AP wishes to become one of the shared APs, it may provide SCS information that includes QoS information of its own BSS to the sharing AP. The sharing AP may compare the AP SCS information collected from the candidate APs and select one or more of the candidate APs to share its TXOP with based on the comparison results. That is, the sharing AP may use the SCS information collected from candidate APs to determine which candidate APs should have priority for TXOP sharing.

[0124] Figure 10 is a diagram showing a stream classification service (SCS) information exchange, according to some embodiments.

[0125] As shown in the diagram, multiple candidate APs (AP I -AP / z) may collect SCS information from their respective associated STAs. For example, API may collect SCS information from STAl l to STA1_ , AP2 may collect SCS information with STA2 1 to STA2_C and so on. SCS information may include information regarding MAC protocol data unit (MPDU) length, size, etc. Each candidate AP may consolidate the SCS information it has collected from its associated STAs and provide it to the sharing AP. The sharing AP may use the SCS information provided by the candidate APs (APl-APw) to select one or more candidate AP(s) that should become shared APs and how much time to allocate for each shared AP.

[0126] The sharing AP may share a portion of its TXOP with the shared APs. When the sharing AP shares a portion of its TXOP with a shared AP, the shared AP temporarily becomes the TXOP holder and may start a frame exchange sequence in the shared AP’s BSS. If the shared AP is able to support its frame exchange sequence before the end of its allocated time (e.g., due to clear channel condition) or the shared AP has transmitted all or almost all of itsurgent data before the end of its allocated time, the shared AP may decide to return the remaining portion of the TXOP back to the sharing AP.

[0127] The present disclosure introduces techniques for allowing a shared AP to return a remaining portion of a TXOP (that was shared by a sharing AP with the shared AP) back to the sharing AP and for the sharing AP to resume the TXOP, if needed. The shared AP may provide multiple opportunities for the sharing AP to resume the TXOP.

[0128] As will be described in additional detail herein, the techniques for returning and resuming a TXOP may involve multiple phases.Phase 1

[0129] In phase 1, the shared AP may operate as follows. The shared AP may include a TXOP return indicator in a frame exchange sequence in the shared AP’s BSS during the TXOP. The TXOP return indicator may indicate that the shared AP is willing to return the TXOP back to the sharing AP. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PRI) indicating that the sharing AP is allowed to preempt the TXOP. Allowing the TXOP to be preempted may be viewed as being similar to being willing to return the TXOP.Phase 2-1

[0130] In phase 2-1, if the sharing AP detects a TXOP return indicator in a frame exchange sequence in the shared AP’s BSS, the sharing AP may recognize that the shared AP is willing to return the remaining portion of the TXOP back to the sharing AP. In such a scenario, the sharing AP may operate according to one of the cases described below.

[0131] Case 1 - If the sharing AP wishes to resume the TXOP, the sharing AP may resume the TXOP after transmitting a response frame (as a response to the TXOP return indicator included in the frame exchange sequence in the shared AP’s BSS) indicating that the sharing AP wishes to resume the TXOP. In an embodiment, the response frame is a preemption indicator (PRI) frame indicating that the sharing AP wishes to preempt the TXOP. Indicating that the sharing AP wishes to preempt the TXOP may be viewed as being similar to indicating that the sharing AP wishes to resume the TXOP.

[0132] Case 2 - If the sharing AP wishes to resume the TXOP, the sharing AP may resume the TXOP by starting a frame exchange sequence in the sharing AP’s BSS without transmitting a response frame indicating that the sharing AP wishes to resume the TXOP.

[0133] Case 3 - If the sharing AP does not wish to resume the TXOP, the sharing AP may transmit a response frame (as a response to the TXOP return indicator included in the frame exchange sequence in the shared AP’s BSS) indicating that the sharing AP does not wish toresume the TXOP. In an embodiment, the response frame is a PRI frame indicating that the sharing AP does not wish to resume the TXOP. Indicating that the sharing AP does not wish to preempt the TXOP may be viewed as being similar to indicating that the sharing AP does not wish to resume the TXOP.

[0134] Case 4 - If the sharing AP does not wish to resume the TXOP, the sharing AP may decide not to transmit a response frame indicating that the sharing AP wishes to resume the TXOP. That is, the sharing AP may do nothing.Phase 2-2

[0135] Case 5 - If the sharing AP is not able to detect the TXOP return indicator in the frame exchange sequence in the shared AP’s BSS, the sharing AP may not be able to recognize that the shared AP is willing to return the remaining portion of the TXOP. The sharing AP may not be able to detect the TXOP return indicator due to interference from STAs that are hidden to the shared AP or other OBSS STAs (third-party STAs). In this case, the sharing AP may do nothing.Phase 3

[0136] Phase 3 may start after Phase 2-1 and / or 2-2 described above. In phase 3, the shared AP may operate according to one of the cases described below.

[0137] Case A - The shared AP may receive a response frame from the sharing AP indicating that the sharing AP wishes to resume the TXOP.

[0138] Case B - The shared AP may receive a response frame from the sharing AP indicating that the sharing AP does not wish to resume the TXOP and the shared AP has data to be transmitted in the shared AP’s BSS.

[0139] Case C - The shared AP may receive a response frame from the sharing AP indicating that the sharing AP does not wish to resume the TXOP and the shared AP does not have data to be transmitted in the shared AP’s BSS.

[0140] Case D - The shared AP may not receive a response frame from the sharing AP but the shared AP may recognize that the sharing AP wishes to resume TXOP.

[0141] Case E - The shared AP may not receive a response frame from the sharing AP and the shared AP may recognize that OBSS STAs (e.g., third-party STAs except the sharing AP) are using the channel.

[0142] Case F -The shared AP may not receive a response frame from the sharing AP, the shared AP may recognize that there are no OBSS STAs (e.g., third-party STAs except thesharing AP) using the channel, and the shared AP has data to be transmitted in the shared AP’s BSS.

[0143] Case G - The shared AP may not receive a response frame from the sharing AP, the shared AP may recognize that there are no OBSS STAs (e.g., third-party STAs except the sharing AP) using the channel, and the shared AP does not have data to be transmitted in the shared AP’s BSS.

[0144] Various combinations of the cases for the phases mentioned above are shown in the figures and described herein to illustrate example embodiments.Case 1 and Case A

[0145] Figure 11 is a diagram showing a combination of Case 1 and Case A, according to some embodiments.

[0146] As shown in the diagram, the sharing AP may transmit a control frame 1105 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a multi-user request-to-send TXOP sharing trigger frame (MU-RTS TXS TF). Responsive to receiving the control frame 1105 from the sharing AP, the shared AP may transmit a response frame 1110 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1110 is a clear-to-send (CTS) frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared AP may use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0147] After the shared AP transmits the response frame 1110, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1115 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1120 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1120 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” In an embodiment, the shared AP includes the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based physical layer protocol data units (PPDUs) from the STAs associated with the shared AP. Additionally or alternatively, in an embodiment, the shared AP includes theTXOP return indicator in a block acknowledgement (BA) frame that the shared AP transmits to the STAs associated with the shared AP to acknowledge uplink trigger-based PPDUs transmitted by the STAs. In an embodiment, a non-AP STA that belongs to the shared AP’s BSS includes the TXOP return indicator in a frame that it transmits during the frame exchange sequence 1120 in the shared AP’s BSS. More generally (in the example shown in Figure 11 and other examples shown in the other figures), the shared AP and / or a non-AP STA that belongs to the shared AP’s BSS can include the TXOP return indicator in the frames that they transmit to indicate that the shared AP is willing to return the TXOP.

[0148] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1120 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1120. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS. For example, if the TXOP return indicator is included in a trigger frame transmitted by the shared AP in the shared AP’s BSS, the sharing AP may know to perform the carrier sense of the channel after the shared AP has received uplink trigger-based PPDUs from the STAs associated with the shared AP and the shared AP has transmitted a block acknowledgement (BA) frame to the STAs associated with the shared AP. If the sharing AP determines that the channel is idle (“CS result is IDLE”), the sharing AP may transmit a response frame 1125 after a XIFS interval after the frame exchange sequence 1120 in the shared AP’s BSS if the sharing AP wishes to resume the TXOP. The response frame 1125 may indicate that the sharing AP wishes to resume the TXOP. In an embodiment, the XIFS interval is a SIFS interval. In an embodiment, the response frame 1125 is a PRI frame. In the particular example shown in the diagram, it is assumed that the sharing AP determined that the channel is idle. Thus, the sharing AP transmits the response frame 1125. After transmitting the response frame 1125, the sharing AP may start a new frame exchange sequence 1135 in the sharing AP’s BSS (e.g., to support aperiodic low latency traffic arriving at the sharing AP) or share the TXOP with an AP (which could be the shared AP or a different AP).

[0149] Also, after the frame exchange sequence 1120, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”), the shared AP may resume transmission in the shared AP’s BSS after a X’lFS interval after the frame exchange sequence 1120. The X’lFS interval is an IFS interval that is longer than the XIFS interval to give the sharing AP transmission priority. In an embodiment, the X’lFS interval is a PIFS interval. Thus, if the sharing AP does not transmit a response frame 1125 after the frame exchange sequence 1120 in the shared AP’s BSS,the shared AP may start a frame exchange sequence 1130 to maintain the TXOP. If the shared AP determines that the channel is busy (“CS result is BUSY”), the shared AP may refrain from transmitting in the shared AP’s BSS to return the TXOP back to the sharing AP. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is busy (e.g., because the sharing AP transmitted the response frame 1125 after the XIFS interval). Thus, the shared AP refrains from transmitting in the shared AP’s BSS (e.g., does not start a new frame exchange sequence 1130) to return the TXOP back to the sharing AP.Case 2 and Case D

[0150] Figure 12 is a diagram showing a combination of Case 2 and Case D, according to some embodiments.

[0151] As shown in the diagram, the sharing AP may transmit a control frame 1205 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 1205 from the sharing AP, the shared AP may transmit a response frame 1210 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1210 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared AP may use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0152] After the shared AP transmits the response frame 1210, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1215 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1220 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1120 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0153] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1220 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1220. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP determines that the channel is idle (“CS result is IDLE”), the sharing AP may start a new frame exchange sequence 1225 in the sharing AP’s BSS after a XIFS interval (e.g., SIFS interval) after the frame exchange sequence 1220 in the shared AP’s BSS if the sharing AP wishes to resume the TXOP. In contrast to the combination of Case 1 and Case A described above, the sharing AP may start the new frame exchange sequence 1225 in the sharing AP’s BSS without transmitting a response frame (e.g., without transmitting response frame 1125). In the particular example shown in the diagram, it is assumed that the sharing AP determined that the channel is idle. Thus, the sharing AP may start frame exchange sequence 1225.

[0154] Also, after the frame exchange sequence 1220, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”), the shared AP may resume transmission in the shared AP’s BSS after a X’lFS interval (e.g., PIFS interval) after the frame exchange sequence 1220. The X’lFS interval is an IFS interval that is longer than the XIFS interval to give the sharing AP transmission priority. Thus, if the sharing AP does not start a new frame exchange sequence 1225 after the frame exchange sequence 1220 in the shared AP’s BSS, the shared AP may start a frame exchange sequence 1230 in the shared AP’s BSS to maintain the TXOP. If the shared AP determines that the channel is busy (“CS result is BUSY”), the shared AP may refrain from transmitting in the shared AP’s BSS to return the TXOP back to the sharing AP. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is busy (e.g., because the sharing AP started the new frame exchange sequence 1225 after the XIFS interval). Thus, the shared AP refrains from transmitting in the shared AP’s BSS (e.g., does not start a new frame exchange sequence 1230) to return the TXOP back to the sharing AP.Case 3 and Case B

[0155] Figure 13 is a diagram showing a combination of Case 3 and Case B, according to some embodiments.

[0156] As shown in the diagram, the sharing AP may transmit a control frame 1305 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 1305 from the sharing AP, the shared AP may transmit a response frame 1310 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1310 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared AP may use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0157] After the shared AP transmits the response frame 1310, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1315 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1320 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1120 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0158] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1320 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1320. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP determines that the channel is idle (“CS result is IDLE”), the sharing AP may transmit a response frame 1325 after a XIFS interval (e.g., SIFS interval) after the frame exchange sequence 1320 in the shared AP’s BSS if the sharing AP does not wish to resume the TXOP. The response frame 1325 may indicate that the sharing AP does not wish to resume the TXOP. In an embodiment, the response frame 1325 is a PRI frame (e.g., indicating that preemption is not desired). In the particular example shown in the diagram, it is assumedthat the sharing AP determined that the channel is idle and the sharing AP does not wish to resume the TXOP. Thus, the sharing AP transmits the response frame 1325.

[0159] Also, after the frame exchange sequence 1320, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”), the shared AP may resume transmission in the shared AP’s BSS after a XTFS interval (e.g., PIFS interval) after the frame exchange sequence 1320. The XTFS interval is an IFS interval that is longer than the XIFS interval to give the sharing AP transmission priority. Thus, if the sharing AP does not transmit anything after the frame exchange sequence 1320 in the shared AP’s BSS, the shared AP may start a frame exchange sequence to maintain the TXOP. If the shared AP determines that the channel is busy (“CS result is BUSY”), the shared AP may refrain from transmitting in the shared AP’s BSS. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is busy (e.g., because the sharing AP transmitted the response frame 1325 after the XIFS interval). If the shared AP receives a response frame 1325 from the sharing AP indicating that the sharing AP does not wish to resume the TXOP, the shared AP may perform a carrier sense of the channel after the response frame 1325. If the shared AP determines that the channel is idle (“CS result is IDLE”), the shared AP may start a new frame exchange sequence 1330 in the shared AP’s BSS after a XIFS interval after the response frame 1325 if the shared AP wishes to maintain the TXOP. In the particular example shown in the diagram, it is assumed that the shared AP wishes to maintain the TXOP (e.g., because it has data to transmit in the shared AP’s BSS) so the shared AP starts the new frame exchange sequence 1330. The shared AP may include a TXOP return indicator (e.g., preemption enabled indicator) in this new frame exchange sequence 1330 to indicate that the shared AP is willing to return the TXOP (e.g., to start Phase 1 again).Case 3 and Case C

[0160] Figure 14 is a diagram showing a combination of Case 3 and Case C, according to some embodiments.

[0161] As shown in the diagram, the sharing AP may transmit a control frame 1405 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 1405 from the sharing AP, the shared AP may transmit a response frame 1410 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1410 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared APmay use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0162] After the shared AP transmits the response frame 1410, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1415 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1420 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1420 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0163] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1420 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1420. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP determines that the channel is idle (“CS result is IDLE”), the sharing AP may transmit a response frame 1425 after a XIFS interval (e.g., SIFS interval) after the frame exchange sequence 1420 in the shared AP’s BSS if the sharing AP does not wish to resume the TXOP. The response frame 1425 may indicate that the sharing AP does not wish to resume the TXOP. In an embodiment, the response frame 1425 is a PRI frame (e.g., indicating that preemption is not desired). In the particular example shown in the diagram, it is assumed that the sharing AP determined that the channel is idle. Thus, the sharing AP transmits the response frame 1425 indicating that the sharing AP does not wish to resume the TXOP.

[0164] Also, after the frame exchange sequence 1420, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”), the shared AP may resume transmission in the shared AP’s BSS after a X’lFS interval (e.g., PIFS interval) after the frame exchange sequence 1420. The X’lFS interval is an IFS interval that is longer than the XIFS interval to give the sharing APtransmission priority. Thus, if the sharing AP does not transmit anything after the frame exchange sequence 1420 in the shared AP’s BSS, the shared AP may start a frame exchange sequence to maintain the TXOP. If the shared AP determines that the channel is busy (“CS result is BUSY”), the shared AP may refrain from transmitting in the shared AP’s BSS. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is busy (e.g., because the sharing AP transmitted the response frame 1425 after the XIFS interval). If the shared AP receives a response frame 1425 from the sharing AP indicating that the sharing AP does not wish to resume the TXOP and the shared AP does not wish to maintain the TXOP (e.g., because the shared AP does not have additional data to transmit in the shared AP’s BSS), the shared AP may abort the TXOP. In the particular example shown in the diagram, it is assumed that the shared AP does not wish to maintain the TXOP. As shown in the diagram, since the sharing AP does not wish to resume the TXOP and the shared AP does not wish to maintain the TXOP, there can be a contention free state.Case 4 and Case E

[0165] Figure 15 is a diagram showing a combination of Case 4 and Case E, according to some embodiments.

[0166] As shown in the diagram, the sharing AP may transmit a control frame 1505 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 1505 from the sharing AP, the shared AP may transmit a response frame 1510 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1510 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared AP may use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0167] After the shared AP transmits the response frame 1510, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1515 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1520 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1120 that includes the TXOP indicator is shown in the diagram as “Shared AP’s FrameExchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0168] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1520 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1520. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP does not wish to resume the TXOP (e.g., because the sharing AP does not have data to transmit in the sharing AP’s BSS), the sharing AP may do nothing regardless of whether the channel is idle or not. In the particular example shown in the diagram, it is assumed that the sharing AP does not wish to resume the TXOP so the sharing AP does nothing.

[0169] Also, after the frame exchange sequence 1520, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”), the shared AP may resume transmission in the shared AP’s BSS after a X’lFS interval (e.g., PIFS interval) after the frame exchange sequence 1520. The X’lFS interval is an IFS interval that is longer than the XIFS interval to give the sharing AP transmission priority. If the shared AP determines that the channel is busy (“CS result is BUSY”), the shared AP may refrain from transmitting in the shared AP’s BSS. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is busy due to an OBSS frame exchange sequence 1525. Thus, the shared AP may refrain from transmitting in the shared AP’s BSS and may abort the TXOP regardless of whether it has data to transmit in the shared AP’s BSS or not.

[0170] In this case, the shared AP does not receive a frame from the sharing AP after frame exchange sequence 1520. The shared AP may not know the exact reason why it did not receive a frame from the sharing AP. There can be several reasons why the shared AP might not receive / detect frames transmitted by the sharing AP. It could be because the sharing AP does not wish to resume the TXOP or it could be the case that the sharing AP wishes to resume the TXOP (and transmitted a frame) but the shared AP was not able to receive frames from the sharing AP due to poor channel conditions.Case 4 and Case G

[0171] Figure 16 is a diagram showing a combination of Case 4 and Case G, according to some embodiments.

[0172] As shown in the diagram, the sharing AP may transmit a control frame 1605 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 1605 from the sharing AP, the shared AP may transmit a response frame 1610 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1610 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared AP may use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0173] After the shared AP transmits the response frame 1610, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1615 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1620 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1120 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0174] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1620 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1620. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP does not wish to resume the TXOP (e.g., because the sharing AP does not have data to transmit in the sharing AP’s BSS), the sharing AP may do nothing regardless of whether the channel is idle or not. In the particular example shown in the diagram, it is assumed that the sharing AP does not wish to resume the TXOP so the sharing AP does nothing.

[0175] Also, after the frame exchange sequence 1620, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”) and the shared AP wishes to maintain the TXOP (e.g., because the shared AP has data to transmit in the shared AP’s BSS), the shared AP may start a new frame exchange sequence in the shared AP’s BSS after a X’lFS interval (e.g., PIFS interval) after the previous frame exchange sequence 1620. The X’lFS interval is an IFS interval that is longer than the XIFS interval to give the sharing AP transmission priority. If the shared AP determines that the channel is busy (“CS result is BUSY”), the shared AP may refrain from transmitting in the shared AP’s BSS. If the shared AP determines that the channel is idle (“CS result is IDLE”) but the shared AP does not wish to maintain the TXOP (e.g., because the shared AP does not have data to transmit in the shared AP’s BSS), the shared AP may abort the TXOP or transmit a control frame 1625 to return the TXOP to the sharing AP. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is idle but the shared AP does not wish to maintain the TXOP so the shared AP transmits a control frame 1625 to return the TXOP back to the sharing AP. In an embodiment, the control frame 1625 is a CF-END frame.

[0176] In this case, the shared AP does not receive a frame from the sharing AP after frame exchange sequence 1620. The shared AP may not know the exact reason why it did not receive a frame from the sharing AP. There can be several reasons why the shared AP might not receive / detect frames transmitted by the sharing AP. It could be because the sharing AP does not wish to resume the TXOP or it could be the case that the sharing AP wishes to resume the TXOP (and transmitted a frame) but the shared AP was not able to receive frames from the sharing AP due to poor channel conditions.Case 4 and Case F

[0177] Figure 17 is a diagram showing a combination of Case 4 and Case F, according to some embodiments.

[0178] As shown in the diagram, the sharing AP may transmit a control frame 1705 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 1705 from the sharing AP, the shared AP may transmit a response frame 1710 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1710 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared APmay use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0179] After the shared AP transmits the response frame 1710, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1715 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1720 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1120 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0180] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1720 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1720. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP does not wish to resume the TXOP (e.g., because the sharing AP does not have data to transmit in the sharing AP’s BSS), the sharing AP may do nothing regardless of whether the channel is idle or not. In the particular example shown in the diagram, it is assumed that the sharing AP does not wish to resume the TXOP so the sharing AP does nothing.

[0181] Also, after the frame exchange sequence 1720, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”) and the shared AP wishes to maintain the TXOP (e.g., because the shared AP has data to transmit in the shared AP’s BSS), the shared AP may start a new frame exchange sequence 1725 in the shared AP’s BSS after a X’lFS interval (e.g., PIFS interval) after the previous frame exchange sequence 1720. The X’lFS interval is an IFS interval that is longer than the XIFS interval to give the sharing AP transmission priority. Thus, if the sharing AP does not transmit a response frame or start a new frame exchange sequence after the frame exchange sequence 1720 in the shared AP’s BSS, the shared AP may start aframe exchange sequence 1725 in the shared AP’s BSS to maintain the TXOP. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is idle (e.g., because the sharing AP does not transmit a frame and OBSS STAs also do not transmit a frame) and the shared AP wishes to maintain the TXOP so the shared AP starts a new frame exchange sequence 1725 in the shared AP’s BSS after a XTFS interval after the previous frame exchange sequence 1720. The shared AP may include a TXOP return indicator (e.g., preemption enabled indicator) in this new frame exchange sequence 1725 to indicate that the shared AP is willing to return the TXOP (e.g., to start Phase 1 again).

[0182] In this case, the shared AP does not receive a frame from the sharing AP after frame exchange sequence 1720. The shared AP may not know the exact reason why it did not receive a frame from the sharing AP. There can be several reasons why the shared AP might not receive / detect frames transmitted by the sharing AP. It could be because the sharing AP does not wish to resume the TXOP or it could be the case that the sharing AP wishes to resume the TXOP (and transmitted a frame) but the shared AP was not able to receive frames from the sharing AP due to poor channel conditions.Case 5 and Case E

[0183] Figure 18 is a diagram showing a combination of Case 5 and Case E, according to some embodiments.

[0184] As shown in the diagram, the sharing AP may transmit a control frame 1805 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 1805 from the sharing AP, the shared AP may transmit a response frame 1810 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1810 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared AP may use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0185] After the shared AP transmits the response frame 1810, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1815 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1820 in the shared AP’s BSS. In an embodiment, the TXOPreturn indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1820 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0186] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1820 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1820. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP determines that the channel is idle (“CS result is IDLE”), the sharing AP may transmit a response frame or start a frame exchange sequence in the sharing AP’s BSS after a XIFS interval (e.g., SIFS interval) after the frame exchange sequence 1820 in the shared AP’s BSS if the sharing AP wishes to resume the TXOP. However, if the sharing AP does not detect the TXOP return indicator in the frame exchange sequence 1820 in the shared AP’s BSS, the sharing AP may do nothing. In the particular example shown in the diagram, it is assumed that the sharing AP does not detect the TXOP return indicator included in the frame exchange sequence 1820 in the shared AP’s BSS due to interference from an OBSS frame exchange sequence 1825 so the sharing AP does nothing.

[0187] Also, after the frame exchange sequence 1820, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”), the shared AP may start a frame exchange sequence in the shared AP’s BSS after a X’lFS interval (e.g., PIFS interval) after the previous frame exchange sequence 1820 if the shared AP wishes to maintain the TXOP. The X’lFS interval is an IFS interval that is longer than the XIFS interval to give the sharing AP transmission priority. If the shared AP determines that the channel is busy (“CS result is BUSY”), the shared AP may refrain from transmitting in the shared AP’s BSS and abort the TXOP. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is busy due to an OBSS frame exchange sequence 1830. Thus, the shared AP refrains from transmitting in the shared AP’s BSS (e.g., does not start a new frame exchange sequence) and may abort the TXOP regardless of whether it has data to transmit in the shared AP’s BSS or not.

[0188] In this case, the shared AP does not receive a frame from the sharing AP after frame exchange sequence 1820. The shared AP may not know the exact reason why it did not receive a frame from the sharing AP. There can be several reasons why the shared AP might not receive / detect frames transmitted by the sharing AP. It could be because the sharing AP does not wish to resume the TXOP or it could be the case that the sharing AP wishes to resume the TXOP (and transmitted a frame) but the shared AP was not able to receive frames from the sharing AP due to poor channel conditions.Case 5 and Case F

[0189] Figure 19 is a diagram showing a combination of Case 5 and Case F, according to some embodiments.

[0190] As shown in the diagram, the sharing AP may transmit a control frame 1905 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 1905 from the sharing AP, the shared AP may transmit a response frame 1910 to the sharing AP to accept / acknowledge the TXOP sharing. In an embodiment, the response frame 1910 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared AP may use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0191] After the shared AP transmits the response frame 1910, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 1915 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 1920 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 1920 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0192] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 1920 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 1920. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP determines that the channel is idle (“CS result is IDLE”), the sharing AP may start a new frame exchange sequence in the sharing AP’s BSS after a XIFS interval (e.g., SIFS interval) after the frame exchange sequence 1920 in the shared AP’s BSS if the sharing AP wishes to resume the TXOP. If the sharing AP determines that the channel is busy or does not detect the TXOP return indicator in the frame exchange sequence 1920 in the shared AP’s BSS, the sharing AP may do nothing. In the particular example shown in the diagram, it is assumed that the sharing AP determines that the channel is busy (e.g., due to OBSS frame exchange 1925) so the sharing AP does nothing.

[0193] Also, after the frame exchange sequence 1920, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle (“CS result is IDLE”) and the shared AP wishes to maintain the TXOP (e.g., because the shared AP has data to transmit in the shared AP’s BSS), the shared AP may start a new frame exchange sequence 1930 in the shared AP’s BSS after a X’lFS interval (e.g., PIFS interval) after the previous frame exchange sequence 1920. The X’lFS interval is an IFS interval that is longer than the XIFS interval to give the sharing AP transmission priority. Thus, if the sharing AP does not transmit a response frame or start a new frame exchange sequence after the frame exchange sequence 1920 in the shared AP’s BSS, the shared AP may start a frame exchange sequence 1930 in the shared AP’s BSS to maintain the TXOP. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is idle (e.g., because the sharing AP does not transmit a frame and OBSS STAs also do not transmit a frame) and the shared AP wishes to maintain the TXOP so the shared AP starts a new frame exchange sequence 1930 in the shared AP’s BSS after a X’lFS interval after the previous frame exchange sequence 1920. The shared AP may include a TXOP return indicator (e.g., preemption enabled indicator) in this new frame exchange sequence 1930 to indicate that the shared AP is willing to return the TXOP (e.g., to start Phase 1 again).

[0194] The sharing AP may not be able to detect the TXOP return indicator included in the frame exchange sequence 1930 in the shared AP’s BSS due to the OBSS frame exchange 1925. Thus, the sharing AP may do nothing after the frame exchange sequence 1930. The shared AP may perform a carrier sense after the frame exchange sequence 1930 in the shared AP’s BSSand determine that the channel is idle. Thus, the shared AP may start another new frame exchange sequence 1935 in the shared AP’s BSS. The shared AP may include a TXOP return indicator (e.g., preemption enabled indicator) in this new frame exchange sequence 1935 to indicate that the shared AP is willing to return the TXOP (e.g., to start Phase 1 again). The sharing AP may detect the TXOP return indicator included in the frame exchange sequence 1935 (e.g., because the OBSS frame exchange 1925 is over). In the particular example shown in the diagram, it is assumed at this time that the sharing AP wishes to resume the TXOP (e.g., because the sharing AP has data to transmit in the sharing AP’s BSS) and determined that the channel is idle so the sharing AP transmits a response frame 1940 (e.g., PRI frame) to the shared AP after a XIFS interval after the frame exchange sequence 1935 in the shared AP’s BSS and starts a new frame exchange sequence 1950 in the sharing AP’s BSS. The shared AP may perform a carrier sense of the channel after the frame exchange sequence 1935 in the shared AP’s BSS and may determine that the channel is busy (due to the sharing AP transmitting the response frame 1940). Thus, the shared AP may refrain from transmitting in the shared AP’s BSS (does not start frame exchange sequence 1945).

[0195] As shown in the diagram, the shared AP may include a TXOP return indicator in multiple frame exchange sequences to give the sharing AP multiple opportunities to resume the TXOP. Thus, even if the sharing AP is plagued by OBSS interference (e.g., OBSS frame exchange 1925), the sharing AP may be able to eventually detect a TXOP return indicator after the OBSS frame exchange is over. Upon detecting the TXOP return indicator, the sharing AP may transmit a response frame to the shared AP to resume the TXOP, if so desired.

[0196] In this case, the shared AP does not receive a frame from the sharing AP after frame exchange sequence 1920 and frame exchange sequence 1930. The shared AP may not know the exact reason why it did not receive a frame from the sharing AP. There can be several reasons why the shared AP might not receive / detect frames transmitted by the sharing AP. It could be because the sharing AP does not wish to resume the TXOP or it could be the case that the sharing AP wishes to resume the TXOP (and transmitted a frame) but the shared AP was not able to receive frames from the sharing AP due to poor channel conditions.

[0197] Figure 20 is a diagram showing a combination of Case 4 and Case F followed by a combination of Case 1 and Case A, according to some embodiments.

[0198] As shown in the diagram, the sharing AP may transmit a control frame 2005 to the shared AP to share its TXOP with the shared AP. In an embodiment, the control frame is a MU- RTS TXS TF. Responsive to receiving the control frame 2005 from the sharing AP, the shared AP may transmit a response frame 2010 to the sharing AP to accept / acknowledge the TXOPsharing. In an embodiment, the response frame 2010 is a CTS frame. The TXOP sharing may allocate a time period within the sharing AP’s TXOP that the shared AP can use. The shared AP may use all of the allocated time period or just use a portion of the allocated time period and return the remaining portion back to the sharing AP.

[0199] After the shared AP transmits the response frame 2010, the shared AP and STA(s) that belong to the shared AP’s BSS may perform a frame exchange sequence 2015 in the shared AP’s BSS. The shared AP may decide to return the remaining portion of the TXOP back to the sharing AP according to some conditions (e.g., if the shared AP does not have additional data to transmit in the shared AP’s BSS). If the shared AP decides to return the remaining portion of the TXOP back to the sharing AP, the shared AP may include a TXOP return indicator in the next frame exchange sequence 2020 in the shared AP’s BSS. In an embodiment, the TXOP return indicator is a preemption enabled indicator (PR enabled). Thus, the frame exchange sequence 2020 that includes the TXOP indicator is shown in the diagram as “Shared AP’s Frame Exchange + PR Enabled.” The shared AP may include the TXOP return indicator in a trigger frame that the shared AP transmits to STAs associated with the shared AP to solicit uplink trigger-based PPDUs from the STAs associated with the shared AP and / or the BA frame that the shared AP transmits to the STAs associated with the shared AP, in a similar manner as described above for the combination of Case 1 and Case A.

[0200] If the sharing AP detects the TXOP return indicator in the frame exchange sequence 2020 in the shared AP’s BSS, the sharing AP may perform a carrier sense of the channel after the frame exchange sequence 2020. The sharing AP may know the starting point of when to perform the carrier sense of the channel based on the frame(s) transmitted in the shared AP’s BSS, in a similar manner as described above for the combination of Case 1 and Case A. If the sharing AP determines that the channel is idle (“CS result is IDLE”), the sharing AP may transmit a response frame (e.g., a PRI frame) after a XIFS interval (e.g., SIFS interval) after the frame exchange sequence 2020 in the shared AP’s BSS if the sharing AP wishes to resume the TXOP and then start a new frame exchange sequence in the sharing AP’s BSS. If the sharing AP determines that the channel is busy or does not detect the TXOP return indicator in the frame exchange sequence 2020 in the shared AP’s BSS, the sharing AP may do nothing. In the particular example shown in the diagram, it is assumed that the sharing AP does not wish to resume the TXOP so the sharing AP does nothing.

[0201] Also, after the frame exchange sequence 2020, the shared AP may perform a carrier sense of the channel (at the same time as the sharing AP). If the shared AP determines that the channel is idle and the shared AP has data to transmit in the shared AP’s BSS, the shared APmay start a new frame exchange sequence 2025 in the shared AP’s BSS after a X’lFS interval (e.g., PIFS interval) after the previous frame exchange sequence 2020. Thus, if the sharing AP does not transmit a response frame or start a new frame exchange sequence after the frame exchange sequence 2020 in the shared AP’s BSS, the shared AP may start a frame exchange sequence 2025 in the shared AP’s BSS to maintain the TXOP. In the particular example shown in the diagram, it is assumed that the shared AP determined that the channel is idle (e.g., because the sharing AP does not transmit a frame and OBSS STAs also do not transmit a frame) and the shared AP wishes to maintain the TXOP (e.g., because the shared AP has data to transmit in the shared AP’s BSS) so the shared AP starts a new frame exchange sequence 2025 in the shared AP’s BSS after a X’lFS interval after the previous frame exchange sequence 2020. The shared AP may include a TXOP return indicator (e.g., preemption enabled indicator) in this new frame exchange sequence 2025 to indicate that the shared AP is willing to return the TXOP (e.g., to start Phase 1 again).

[0202] In the particular example shown in the diagram, it is assumed that after detecting the TXOP indicator included in the frame exchange sequence 2025 in the shared AP’s BSS, the sharing AP still does not wish to resume the TXOP so the sharing AP does nothing. Also, in the particular example shown in the diagram, it is assumed that the shared AP wishes to maintain the TXOP after the frame exchange sequence 2025 (and the channel is idle) so the shared AP starts another new frame exchange sequence 2030 in the shared AP’s BSS. The shared AP may include a TXOP return indicator in this new frame exchange sequence 2030 to indicate that the shared AP is willing to return the TXOP (e.g., to start Phase 1 again).

[0203] In the particular example shown in the diagram, it is assumed that the sharing AP detects the TXOP return indicator included in the frame exchange sequence 2030 and that the sharing AP wishes to resume the TXOP at this time. Thus, the sharing AP transmits a response frame 2035 (e.g., PRI frame) to the shared AP after a XIFS interval after the frame exchange sequence 2030 in the shared AP’s BSS and starts a new frame exchange sequence 2045 in the sharing AP’s BSS. The shared AP may perform a carrier sense of the channel after the frame exchange sequence 2030 in the sharing AP’s BSS and may determine that the channel is busy (e.g., due to the sharing AP transmitting response frame 2035). Thus, the shared AP may refrain from transmitting in the shared AP’s BSS (does not start frame exchange sequence 2040).

[0204] As shown in the diagram, the shared AP may include a TXOP return indicator in multiple frame exchange sequences to give the sharing AP multiple opportunities to resume the TXOP. When the shared AP no longer wishes to maintain the TXOP (e.g., because it does nothave any more data to transmit), the shared AP may transmit a control frame (e.g., CF-END frame) to explicitly return the TXOP back to the sharing AP.

[0205] The use of the techniques described herein may allow a shared AP to efficiently return the remaining portion of a TXOP that was shared with the shared AP back to the sharing AP. The shared AP may provide several opportunities for the sharing AP to resume the TXOP. The use of the techniques described herein may allow the sharing AP to resume the TXOP if the sharing AP has data (e.g., urgent data) to transmit during the shared TXOP, which allows the TXOP to be used more efficiently.

[0206] Turning now to Figure 21, a method 2100 will be described for resuming a TXOP, in accordance with an example embodiment. The method 2100 may be performed by a sharing AP that belongs to a first BSS to resume a TXOP that was shared by the sharing AP with a shared AP that belongs to a second BSS. The sharing AP may be implemented by a wireless device (e.g., wireless device 104).

[0207] At operation 2105, the sharing AP detects a TXOP return indicator in a frame exchange sequence in the second BSS during the TXOP. In an embodiment, the TXOP return indicator is detected in a frame transmitted by the shared AP. In an embodiment, the TXOP return indicator is detected in a frame transmitted by a non-AP STA that belongs to the second BSS.

[0208] At operation 2110, responsive to detecting the TXOP return indicator in the frame exchange sequence in the second BSS, the sharing AP performs a carrier sense of a channel after the frame exchange sequence in the second BSS to determine whether the channel is idle or busy. In an embodiment, if the sharing AP does not detect the TXOP return indicator in the frame exchange sequence in the second BSS, the sharing AP refrains from transmitting after the frame exchange sequence in the second BSS. In an embodiment, the sharing AP does not detect the TXOP return indicator in the frame exchange sequence in the second BSS because of a transmission by a third-party STA, wherein the third-party STA is a STA that does not belong to the first BSS or the second BSS.

[0209] At operation 2115, responsive to determining that the channel is idle, the sharing AP starts a second frame exchange sequence in the first BSS (without transmitting a response frame (e.g., without transmitting a PRI frame) after a first IFS (e.g., SIFS) interval after the frame exchange sequence in the second BSS, wherein the first IFS interval is shorter than a second IFS (e.g., PIFS) interval used by the shared AP when the shared AP wishes to maintain the TXOP after the frame exchange sequence in the second BSS.

[0210] In an embodiment, if the sharing AP does not wish to resume the TXOP, the sharing AP refrains from transmitting after the frame exchange sequence in the second BSS. In an embodiment, the sharing AP receives a control frame (e.g., CF-END frame) from the shared AP after the frame exchange sequence in the second BSS, wherein the control frame indicates that the shared AP is returning the TXOP to the sharing AP.

[0211] Turning now to Figure 22, a method 2200 will be described for returning a TXOP, in accordance with an example embodiment. The method 2200 may be performed by a shared AP that belongs to a first BSS to try to return a TXOP that was shared with the shared AP by a sharing AP. The shared AP may be implemented by a wireless device (e.g., wireless device 104).

[0212] At operation 2205, the shared AP performs a carrier sense of a channel after a frame exchange sequence in the first BSS to determine whether the channel is idle or busy, wherein the frame exchange sequence includes a TXOP return indicator. In an embodiment, the TXOP return indicator is included in a frame transmitted by the shared AP. In an embodiment, the TXOP return indicator is included in a frame transmitted by a non-AP STA that belongs to the first BSS.

[0213] At operation 2210, responsive to determining that the channel is busy, the shared AP refrains from resuming transmission in the first BSS to return the TXOP to the sharing AP. In an embodiment, the channel is busy because the sharing AP resumed the TXOP after the frame exchange sequence in the first BSS. In an embodiment, the channel is busy because of a transmission by a third-party STA, wherein the third-party STA is a STA that does not belong to the first BSS or the second BSS.

[0214] In an embodiment, if the channel is determined to be idle and the shared AP has additional data to transmit in the first BSS, the shared AP starts a second frame exchange sequence in the first BSS after a first IFS interval after the frame exchange sequence in the first BSS, wherein the first IFS interval is longer than a second IFS interval used by the sharing AP when the sharing AP wishes to resume the TXOP after the frame exchange sequence in the first BSS. In an embodiment, the second frame exchange sequence includes a second TXOP return indicator.

[0215] In an embodiment, if the channel is determined to be idle and the shared AP does not have additional data to transmit in the first BSS, the shared AP transmits a control frame (e.g., CF-END frame) after a first IFS interval after the frame exchange sequence in the first BSS to return the TXOP to the sharing AP, wherein the first IFS interval is longer than a second IFSinterval used by the sharing AP when the sharing AP wishes to resume the TXOP after the frame exchange sequence in the first BSS.

[0216] Turning now to Figure 23, a method 2300 will be described for not resuming a TXOP, in accordance with an example embodiment. The method 2300 may be performed by a sharing AP that belongs to a first BSS to allow a shared AP that belongs to a second BSS to maintain a TXOP that was shared by the sharing AP with the shared AP. The sharing AP may be implemented by a wireless device (e.g., wireless device 104).

[0217] At operation 2305, the sharing AP detects a TXOP return indicator in a frame exchange sequence in the second BSS during the TXOP.

[0218] At operation 2310, responsive to detecting the TXOP return indicator in the frame exchange sequence in the second BSS, the sharing AP performs a carrier sense of a channel after the frame exchange sequence in the second BSS to determine whether the channel is idle or busy. In an embodiment, the TXOP return indicator is detected in a frame transmitted by the shared AP. In an embodiment, the TXOP return indicator is detected in a frame transmitted by a non-AP STA that belongs to the second BSS.

[0219] At operation 2315, responsive to determining that the channel is idle and determining that the sharing AP does not wish to resume the TXOP, the sharing AP transmits a response frame to the shared AP after the frame exchange sequence in the second BSS, wherein the response frame indicates that the sharing AP does not wish to resume the TXOP. In an embodiment, the response frame is transmitted after a SIFS interval after the frame exchange sequence in the second BSS.

[0220] Turning now to Figure 24, a method 2400 will be described for maintaining a TXOP, in accordance with an example embodiment. The method 2400 may be performed by a shared AP that belongs to a first BSS to maintain a TXOP that was shared with the shared AP by a sharing AP that belongs to a second BSS. The shared AP may be implemented by a wireless device (e.g., wireless device 104).

[0221] At operation 2405, the shared AP starts a frame exchange sequence in the first BSS, wherein the frame exchange sequence includes a TXOP return indicator. In an embodiment, the TXOP return indicator is included in a frame transmitted by the shared AP. In an embodiment, the TXOP return indicator is included in a frame transmitted by a non-AP STA that belongs to the first BSS.

[0222] At operation 2410, the shared AP determines whether a response frame indicating that the sharing AP does not wish to resume the TXOP was received from the sharing AP after the frame exchange sequence in the first BSS.

[0223] At operation 2415, responsive to determining that the response frame was received from the sharing AP after the frame exchange sequence in the first BSS, the shared AP performs a carrier sense of a channel after receiving the response frame to determine whether the channel is idle or busy.

[0224] At operation 2420, responsive to determining that the channel is idle, the shared AP starts a second frame exchange sequence in the first BSS after receiving the response frame (to maintain the TXOP). In an embodiment, the second frame exchange sequence includes a second TXOP return indicator.

[0225] In an embodiment, if the shared AP does not have additional data to transmit in the first BSS, the shared AP refrains from transmitting in the first BSS after receiving the response frame.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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) that belongs to a first basic service set (BSS) to resume a transmission opportunity (TXOP) that was shared by the sharing AP with a shared AP that belongs to a second BSS, the method comprising: detecting a TXOP return indicator in a frame exchange sequence in the second BSS during the TXOP; responsive to detecting the TXOP return indicator in the frame exchange sequence in the second BSS, performing a carrier sense of a channel after the frame exchange sequence in the second BSS to determine whether the channel is idle or busy; and responsive to determining that the channel is idle, starting a second frame exchange sequence in the first BSS after a first interframe space (IFS) interval after the frame exchange sequence in the second BSS, wherein the first IFS interval is shorter than a second IFS interval used by the shared AP when the shared AP wishes to maintain the TXOP after the frame exchange sequence in the second BSS.

2. The method of claim 1, wherein if the sharing AP does not wish to resume the TXOP, the sharing AP refrains from transmitting after the frame exchange sequence in the second BSS.

3. The method of claim 2, wherein the sharing AP receives a control frame from the shared AP after the frame exchange sequence in the second BSS, wherein the control frame indicates that the shared AP is returning the TXOP to the sharing AP.

4. The method of claim 1, wherein if the sharing AP does not detect the TXOP return indicator in the frame exchange sequence in the second BSS, the sharing AP refrains from transmitting after the frame exchange sequence in the second BSS.

5. The method of claim 4, wherein the sharing AP does not detect the TXOP return indicator in the frame exchange sequence in the second BSS because of a transmission by a third-party station (STA), wherein the third-party STA is a STA that does not belong to the first BSS or the second BSS.

6. The method of claim 1, wherein the TXOP return indicator is detected in a frame transmitted by a non-AP station (STA) that belongs to the second BSS.

7. A method performed by a shared access point (AP) that belongs to a first basic service set (BSS) to try to return a transmission opportunity (TXOP) that was shared with the shared AP by a sharing AP that belongs to a second BSS, the method comprising: performing a carrier sense of a channel after a frame exchange sequence in the first BSS to determine whether the channel is idle or busy, wherein the frame exchange sequence includes a TXOP return indicator; and responsive to determining that the channel is busy, refraining from resuming transmission in the first BSS to return the TXOP to the sharing AP.

8. The method of claim 7, wherein the channel is busy because the sharing AP resumed the TXOP after the frame exchange sequence in the first BSS.

9. The method of claim 7, wherein the channel is busy because of a transmission by a third- party station (STA), wherein the third-party STA is a STA that does not belong to the first BSS or the second BSS.

10. The method of claim 7, wherein if the channel is determined to be idle and the shared AP has additional data to transmit in the first BSS, the shared AP starts a second frame exchange sequence in the first BSS after a first interframe space (IFS) interval after the frame exchange sequence in the first BSS, wherein the first IFS interval is longer than a second IFS interval used by the sharing AP when the sharing AP wishes to resume the TXOP after the frame exchange sequence in the first BSS.

11. The method of claim 10, wherein the second frame exchange sequence includes a second TXOP return indicator.

12. The method of claim 7, wherein if the channel is determined to be idle and the shared AP does not have additional data to transmit in the first BSS, the shared AP transmits a control frame after a first interframe space (IFS) interval after the frame exchange sequence in the first BSS to return the TXOP to the sharing AP, wherein the first IFS interval is longer than a second IFS interval used by the sharing AP when the sharing AP wishes to resume the TXOP after the frame exchange sequence in the first BSS.

13. The method of claim 7, wherein the TXOP return indicator is included in a frame transmitted by the shared AP.

14. A method performed by a sharing access point (AP) that belongs to a first basic service set (BSS) to allow a shared AP that belongs to a second BSS to maintain a transmission opportunity (TXOP) that was shared by the sharing AP with the shared AP, the method comprising: detecting a TXOP return indicator in a frame exchange sequence in the second BSS during the TXOP; responsive to detecting the TXOP return indicator in the frame exchange sequence in the second BSS, performing a carrier sense of a channel after the frame exchange sequence in the second BSS to determine whether the channel is idle or busy; and responsive to determining that the channel is idle and determining that the sharing AP does not wish to resume the TXOP, transmitting a response frame to the shared AP after the frame exchange sequence in the second BSS, wherein the response frame indicates that the sharing AP does not wish to resume the TXOP.

15. The method of claim 14, wherein the response frame is transmitted after a short interframe space (SIFS) interval after the frame exchange sequence in the second BSS.

16. The method of claim 14, wherein the TXOP return indicator is detected in a frame transmitted by a non-AP station (STA) that belongs to the second BSS.

17. A method performed by a shared access point (AP) that belongs to a first basic service set (BSS) to maintain a transmission opportunity (TXOP) that was shared with the shared AP by a sharing AP that belongs to a second BSS, the method comprising: determining whether a response frame indicating that the sharing AP does not wish to resume the TXOP was received from the sharing AP after a frame exchange sequence in the first BSS, wherein the frame exchange sequence includes a TXOP return indicator; responsive to determining that the response frame was received from the sharing AP after the frame exchange sequence in the first BSS, performing a carrier sense of a channel after receiving the response frame to determine whether the channel is idle or busy; and responsive to determining that the channel is idle, starting a second frame exchange sequence in the first BSS after receiving the response frame.

18. The method of claim 17, wherein the second frame exchange sequence includes a secondTXOP return indicator.

19. The method of claim 17, wherein if the shared AP does not have additional data to transmit in the first BSS, the shared AP refrains from transmitting in the first BSS after receiving the response frame.

20. The method of claim 17, wherein the TXOP return indicator is included in a frame transmitted by the shared AP.

21. 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 1-6.

22. A wireless device to implement a shared 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 shared AP to perform the method of any one of claims 7-13.

23. 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 14-16.

24. A wireless device to implement a shared access point (AP), 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 shared AP to perform the method of any one of claims 17-20.

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