Transmission opportunity (TXOP) sharing considering fairness and low latency traffic

Abstract

A method performed by a sharing access point (AP) to share a transmission opportunity (TXOP) owned by the sharing AP with a shared AP. The method includes generating and transmitting a control frame indicating that the sharing AP is sharing the TXOP with the shared AP, wherein the control frame includes a first field that indicates a network allocation vector (NAV) protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP, wherein the NAV protection duration is set to be shorter than a duration of the time period allocated for the shared AP.

Description

TRANSMISSION OPPORTUNITY (TXOP) SHARING CONSIDERING FAIRNESS AND LOW LATENCY TRAFFICCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 558,492, filed February 27, 2024, titled “Methods and apparatus to handle fairness and low latency traffic between coordinated multiple APs”, and U.S. Provisional Application No. 63 / 558,501, filed February 27, 2024, titled “Explicit TXOP return considering fairness and low latency traffic 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 transmission opportunity (TXOP) sharing in a wireless network.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, 802.11be 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 multi-AP coordination 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 / or joint transmission (JTX) to increase spectral efficiency in high density network scenarios.

[0006] The use of C-TDMA may create fairness issues for stations (STAs) that do not participate in C-TDMA. For example, under the existing rules of IEEE 802.11 wireless networking standards, when a sharing access point (AP) shares its transmission opportunity (TXOP) with a shared AP, STAs that are hidden to the shared AP may not be able to transmit during the time period allocated for the shared AP even though the transmission of the hidden STA’s will not interfere with the shared AP’s transmission. Also, when a sharing AP shares its TXOP with a shared AP, the sharing AP might not be able to transmit aperiodic low latency traffic until after the time period allocated for the shared AP is over, which can significantly delay the low latency traffic. Existing wireless networking standards do not address the fairness issue and do not support aperiodic low latency traffic that occurs on the sharing AP side.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] 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.

[0008] 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.

[0009] Figure 2 is a schematic diagram of a wireless device, in accordance with some embodiments of the present disclosure.

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

[0011] Figure 3B illustrates components of a wireless device configured to receive data, in accordance with some embodiments of the present disclosure.

[0012] Figure 4 illustrates interframe space (IFS) relationships, in accordance with some embodiments of the present disclosure.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] Figure 8 illustrates an example of multi-user (MU) transmission in Orthogonal Frequency -Di vision Multiple Access (OFDMA), in accordance with some embodiments of the present disclosure.

[0017] 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.

[0018] Figure 10 is a diagram showing an example where the network allocation vector (NAV) protection duration is set to correspond to the sum of the duration of a response frame transmission and a predefined margin duration, according to some embodiments.

[0019] Figure 11 is a diagram showing example where the NAV protection duration is set to correspond to a NAV timeout duration, according to some embodiments.

[0020] Figure 12 is a diagram showing a situation where low latency traffic occurs on the sharing AP side but the sharing AP is not able to transmit the low latency traffic even after theshared AP returns the transmission opportunity (TXOP) to the sharing AP, according to some embodiments.

[0021] Figure 13 is a diagram showing a scenario where a sharing AP successfully accesses the channel following an implicit TXOP return approach, according to some embodiments.

[0022] Figure 14 is a diagram showing a scenario where a shared AP successfully accesses the channel following an implicit TXOP return approach, according to some embodiments.

[0023] Figure 15 is a diagram showing a scenario where a sharing AP resumes transmission after receiving an explicit TXOP return frame, according to some embodiments.

[0024] Figure 16 is a diagram showing a scenario where a sharing AP resumes transmission after detecting an explicit TXOP return indication, according to some embodiments.

[0025] Figure 17 is a diagram showing a scenario where a sharing AP reallocates the TXOP to the shared AP after detecting an explicit TXOP return indication, according to some embodiments.

[0026] Figure 18 is a flow diagram of a method for sharing a TXOP with a shared AP, according to some embodiments.

[0027] Figure 19 is a flow diagram of a method for following an implicit TXOP return approach, according to some embodiments.

[0028] Figure 20 is a flow diagram of a method for following an explicit TXOP return approach, according to some embodiments.

[0029] Figure 21 is a flow diagram of a method for sharing in a TXOP owned by a sharing AP, according to some embodiments.

[0030] Figure 22 is a flow diagram of a method for following an implicit TXOP return approach, according to some embodiments.

[0031] Figure 23 is a flow diagram of a method for following an explicit TXOP return approach, according to some embodiments.DETAILED DESCRIPTION

[0032] The present disclosure generally relates to wireless communications, and more specifically, relates to transmission opportunity (TXOP) sharing in a wireless network.

[0033] The present disclosure describes TXOP sharing techniques that take fairness issues into consideration and can support low latency traffic that might occur on the sharing access point (AP) side. For example, the TXOP sharing techniques described herein may allow stations (STAs) that are hidden to a shared AP to access the channel during a time period allocated for the shared AP within the TXOP. Also, the TXOP sharing techniques described herein mayallow the shared AP to implicitly or explicitly return the TXOP to the sharing AP to allow the sharing AP to transmit low latency traffic, if needed. As used herein, a sharing AP may be an AP that initiates multi-AP coordination. In the context of TXOP sharing, the sharing AP may be the TXOP owner that is sharing its TXOP with a shared AP (e.g., the sharing AP allocates some time within the TXOP for the shared AP). As used herein, a shared AP may be an AP that participates in a multi-AP coordination initiated by the sharing AP. In the context of TXOP sharing, the shared AP may be an AP that is allocated some time within the sharing AP’s TXOP.

[0034] According to some embodiments, a sharing AP may generate and transmit a control frame indicating that the sharing AP is sharing the TXOP with the shared AP. The control frame may include a first field that indicates a network allocation vector (NAV) protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP. The NAV protection duration may be set to be shorter than the duration of the time period allocated for the shared AP. Setting the NAV protection duration to be shorter than the duration of the time period allocated for the shared AP allows STAs that are hidden to the shared AP to transmit data during the time period allocated for the shared AP.

[0035] Responsive to receiving the control frame, the shared AP may transmit a response frame to the sharing AP. The shared AP may then initiate a frame exchange sequence within its basic service set (BSS) during the time period allocated for the shared AP. In an embodiment, the sharing AP allocates time for the shared AP in multiple segments. Thus, the time period allocated for the shared AP may be one of a plurality of time periods allocated for the shared AP within the TXOP.

[0036] The shared AP may follow an implicit TXOP return approach or an explicit TXOP return approach to give the sharing AP an opportunity to reclaim the TXOP, if needed (e.g., to transmit aperiodic low latency traffic that occurs on the sharing AP side).

[0037] With the implicit TXOP return approach, if the shared AP needs to resume transmission within the TXOP, the shared AP may attempt to access the channel after a second interframe space interval (e.g., point coordination function interframe space (PIFS) interval) after an end of a NAV protection time period for the frame exchange sequence. The second interframe space interval may be longer than a first interframe space interval (e.g., short interframe space (SIFS) interval) used by the sharing AP after the end of the NAV protection time period. Thus, by using the shorter interframe space interval, the sharing AP may be given channel access priority over the shared AP.

[0038] With a first embodiment of the explicit TXOP return approach, the shared AP may transmit a TXOP return frame to the sharing AP after the frame exchange sequence to return theTXOP to the sharing AP before an end of the time period allocated for the shared AP. Responsive to receiving the TXOP return frame, the sharing AP may attempt to access the channel after an interframe space (e.g., SIFS) interval after receiving the TXOP return frame if the sharing AP needs to reclaim the TXOP. With a second embodiment of the explicit TXOP return approach, the shared AP may include a TXOP return indication in a frame transmitted during the frame exchange sequence to return the TXOP to the sharing AP before an end of the time period allocated for the shared AP. Responsive to detecting the TXOP return indication in the frame exchange sequence, the sharing AP may attempt to access the channel after an interframe space interval (e.g., PIFS interval) after the end of the NAV protection time period if the sharing AP needs to reclaim the TXOP.

[0039] Segmenting the time allocated for the shared AP within the TXOP into multiple segments and allowing the shared AP to implicitly or explicitly return the TXOP to the sharing AP may allow the sharing AP to reclaim the TXOP sooner if the sharing AP has low latency data to transmit.

[0040] 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.

[0041] 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.

[0042] Figure 1 shows a wireless local area network (WLAN) 100 with a basic service set (BSS) 102 that includes a plurality of wireless devices 104 (sometimes referred to as WLAN devices 104). Each of the wireless devices 104 may include a medium access control (MAC) layer and a physical (PHY) layer according to an IEEE (Institute of Electrical and Electronics Engineers) standard 802.11, including one or more of the amendments(e.g., 802.1 la / b / g / n / p / ac / ax / bd / be). In one embodiment, the MAC layer of a wireless device 104 may initiate transmission of a frame to another wireless device 104 by passing a PHY- TXSTART. request (TXVECTOR) to the PHY layer. The TXVECTOR provides parameters for generating and / or transmitting a corresponding frame. Similarly, a PHY layer of a receivingwireless device may generate an RXVECTOR, which includes parameters of a received frame and is passed to a MAC layer for processing.

[0043] 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 104 A) 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- IO4B4), the WLAN 100 may include any number of non-AP STAs (e.g., one or more wireless devices 104B).

[0044] Figure 2 illustrates a schematic block diagram of a wireless device 104, according to an embodiment. The wireless device 104 may be the wireless device 104 A (i.e., the AP of the WLAN 100) or any of the wireless devices 104B1-104B4 in Figure 1. The wireless device 104 includes a baseband processor 210, a radio frequency (RF) transceiver 240, an antenna unit 250, a storage device (e.g., memory device) 232, one or more input interfaces 234, and one or more output interfaces 236. The baseband processor 210, the storage device 232, the input interfaces 234, the output interfaces 236, and the RF transceiver 240 may communicate with each other via a bus 260.

[0045] 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.

[0046] In an embodiment, the MAC processor 212 includes a MAC software processing unit 214 and a MAC hardware processing unit 216. The MAC software processing unit 214 may implement a first plurality of functions of the MAC layer by executing MAC software, which may be included in the software stored in the storage device 232. The MAC hardware processing unit 216 may implement a second plurality of functions of the MAC layer in specialpurpose hardware. However, the MAC processor 212 is not limited thereto. For example, the MAC processor 212 may be configured to perform the first and second plurality of functions entirely in software or entirely in hardware according to an implementation.

[0047] The PHY processor 222 includes a transmitting (TX) signal processing unit (SPU) 224 and a receiving (RX) SPU 226. The PHY processor 222 implements a plurality of functions ofthe PHY layer. These functions may be performed in software, hardware, or a combination thereof according to an implementation.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] As described herein, a wide variety of electronic devices, circuits, firmware, software, and combinations thereof may be used to implement the functions of the components of the WLAN device 104. Furthermore, the WLAN device 104 may include other components, such as application processors, storage interfaces, clock generator circuits, power supply circuits, and the like, which have been omitted in the interest of brevity.

[0054] 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.

[0055] The TxSP 324 includes an encoder 300, an interleaver 302, a mapper 304, an inverse Fourier transformer (TFT) 306, and a guard interval (GI) inserter 308.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324 may include a plurality of interleavers 302 and a plurality of mappers 304 according to a number of spatial streams (NSS) of the transmission. The TxSP 324 may further include a stream parser for dividing the output of the encoder 300 into blocks and may respectively send the blocks to different interleavers 302 or mappers 304. The TxSP 324 may further include a space-time block code (STBC) encoder for spreading the constellation points from the spatial streams into a number of space-time streams (NSTS) and a spatial mapper for mapping the space-time streams to transmit chains. The spatial mapper may use direct mapping, spatial expansion, or beamforming.

[0061] The IFT 306 converts a block of the constellation points output from the mapper 304 (or, when MIMO or MU-MIMO is performed, the spatial mapper) to a time domain block (i.e., asymbol) by using an inverse discrete Fourier transform (IDFT) or an inverse fast Fourier transform (IFFT). If the STBC encoder and the spatial mapper are used, the IFT 306 may be provided for each transmit chain.

[0062] 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.

[0063] When the TxSP 324 performs a MIMO or MU-MIMO transmission, some blocks before the spatial mapper may be provided for each user.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] The RxSP 326 includes a GI remover 318, a Fourier transformer (FT) 316, a demapper 314, a deinterleaver 312, and a decoder 310.

[0068] 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.

[0069] 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.

[0070] When the received transmission is the MIMO or MU-MIMO transmission, the RxSP 326 may include a spatial demapper for converting the respective outputs of the FTs 316 of the receiver chains to constellation points of a plurality of space-time streams, and an STBCdecoder for despreading the constellation points from the space-time streams into one or more spatial streams.

[0071] 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.

[0072] 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.

[0073] When the received transmission is the MIMO or MU-MIMO transmission, the RxSP 326 may use a plurality of demappers 314 and a plurality of deinterleavers 312 corresponding to the number of spatial streams of the transmission. In this case, the RxSP 326 may further include a stream deparser for combining the streams output from the deinterleavers 312.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] The PHY entity for IEEE 802.11 is based on Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). In either OFDM or OFDMA Physical (PHY) layers, a STA (e.g., a wireless device 104) is capable of transmitting and receiving Physical Layer (PHY) Protocol Data Units (PPDUs) (also referred to as PLCP (Physical Layer Convergence Procedure) Protocol Data Units) that are compliant with the mandatory PHY specifications. A PHY specification defines a set of Modulation and Coding Schemes (MCS) and a maximum number of spatial streams. Some PHY entities define downlink (DL) and uplink (UL) Multi-User (MU) transmissions having a maximum number ofspace-time streams (STS) per user and employing up to a predetermined total number of STSs. A PHY entity may provide support for 10 Megahertz (MHz), 20 MHz, 40 MHz, 80 MHz, 160 MHz, 240 MHz, and 320 MHz contiguous channel widths and support for an 80+80, 80+160 MHz, and 160+160 MHz non-contiguous channel width. Each channel includes a plurality of subcarriers, which may also be referred to as tones. A PHY entity may define signaling fields denoted as Legacy Signal (L-SIG), Signal A (SIG-A), and Signal B (SIG-B), and the like within a PPDU by which some necessary information about PHY Service Data Unit (PSDU) attributes are communicated. The descriptions below, for sake of completeness and brevity, refer to OFDM-based 802.11 technology. Unless otherwise indicated, a station refers to a non-AP STA.

[0078] Figure 4 illustrates Inter-Frame Space (IFS) relationships. In particular, Figure 4 illustrates a Short IFS (SIFS), a Point Coordination Function (PCF) IFS (PIFS), a Distributed Coordination Function (DCF) IFS (DIFS), and an Arbitration IFSs corresponding to an Access Category (AC) ‘i’ (AIFS [i]). Figure 4 also illustrates a slot time and a data frame is used for transmission of data forwarded to a higher layer. As shown, a WLAN device 104 transmits the data frame after performing backoff if a DIFS has elapsed during which the medium has been idle.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] A WLAN device 104 that supports Quality of Service (QoS) functionality (that is, a QoS STA) may transmit the frame after performing backoff if an AIFS for an associated access category (AC) (i.e., AIFS[AC]) has elapsed. When transmitted by the QoS STA, any of the data frame, the management frame, and the control frame, which is not the response frame, may use the AIFS[AC] of the AC of the transmitted frame.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] After determining that the channel is not used by other devices (that is, that the channel is IDLE) during a DIFS (and performing backoff if required), the station STA1 may transmit a Request-To-Send (RTS) frame to the station STA2. Upon receiving the RTS frame, after a SIFS the station STA2 may transmit a Clear-To-Send (CTS) frame as a response to the RTS frame. If Dual-CTS is enabled and the station STA2 is an AP, the AP may send two CTS frames inresponse to the RTS frame (e.g., a first CTS frame in a non-High Throughput format and a second CTS frame in the HT format).

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The IEEE 802.1 Ibn (Ultra High Reliability, UHR) working group has been established to address the growing demand for higher peak throughput and reliability in Wi-Fi. As shown in Figure 6, the peak PHY rate has significantly increased from IEEE 802.1 lb to IEEE 802.1 Ibe (Wi-Fi 7), with the latter focusing on further improving peak throughput. The UHR study group aims to enhance the tail of the latency distribution and jitter to support applications that require low latency, such as video-over- WLAN, gaming, AR, and VR. It is noted that variouscharacteristics of UHR (e.g., max PHY rate, PHY rate enhancement, bandwidth / number of spatial streams, and operating bands) are still to be determined.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] The Extremely High Throughput (EHT) PPDU frame encompasses several components. It includes a legacy part, which comprises fields such as the Legacy Short Training Field (L-STF), Legacy Long Training Field (L-LTF), Legacy Signal Field (L-SIG), andRepeated Legacy Signal Field (RL-SIG). These fields are used to maintain compatibility with older Wi-Fi standards.

[0100] 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.

[0101] Figure 7 provides a more detailed description of each field in the EHT PPDU frame, including their purposes and characteristics.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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).

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] Wireless network systems can rely on retransmission of media access control (MAC) protocol data units (MPDUs) when the transmitter (TX) does not receive an acknowledgement from the receiver (RX) or MPDUs are not successfully decoded by the receiver. Using an automatic repeat request (ARQ) approach, the receiver discards the last failed MPDU before receiving the newly retransmitted MPDU. With requirements of enhanced reliability and reduced latency, the wireless network system can evolve toward a hybrid ARQ (HARQ) approach.

[0113] 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.

[0114] 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.

[0115] In a second type of HARQ scheme, also referred to as an incremental redundancy (IR) HARQ (IR-HARQ) scheme, different puncturing patterns are used for each subpacket such that the signal changes for each retransmitted subpacket in comparison to the originally transmitted subpacket. IR-HARQ alternatively uses two puncturing patterns for odd numbered and even numbered transmissions, respectively. The redundancy scheme of IR-HARQ improves the log likelihood ratio (LLR) of parity bit(s) in order to combine information sent across different transmissions due to requests and lowers the code rate as the additional subpacket is used. This results in a lower error rate of the subpacket in comparison to CC-HARQ. The puncturing pattern used in IR-HARQ is indicated by a subpacket identity (SPID) indication. The SPID of the first subpacket may always be set to 0 and all the systematic bits and the punctured parity bits are transmitted in the first subpacket. Self-decoding is possible when the receiving signal- to-noise ratio (SNR) environment is good (i.e., a high SNR). In some embodiments, subpacketswith corresponding SPIDs to be transmitted are in increasing order of SPID but can be exchanged / switched except for the first SPID.

[0116] 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 802.11bn (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.

[0117] 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.

[0118] The operation of various AP coordination schemes has been discussed in the IEEE 802.1 Ibe and UHR standards:

[0119] 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.

[0120] Coordinated OFDMA (C-OFDMA): APs transmit on orthogonal frequency resources by coordinating and splitting the spectrum, enabling more efficient spectrum utilization.

[0121] Joint Transmission (JTX): Multiple APs transmit jointly to a given user simultaneously by sharing data between the APs.

[0122] Coordinated Spatial Reuse (C-SR): Multiple APs or STAs adjust their transmit power to reduce interference between APs.

[0123] By implementing these AP coordination schemes, WLAN systems can improve their overall throughput and efficiency by leveraging the cooperation between multiple APs.

[0124] 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). The expansion to TXOP sharing between multiple BSSs may expand the scope of STAs that are affected by the TXOP sharing. Existing TXOP sharing techniques are designed with TXOP sharing within a single BSS in mind and may not be efficient in scenarios where a TXOP is shared between multiple BSSs. For example, maintaining NAV for a channel reservation period is reasonable within a single BSS toensure that the frame exchange sequence between the TXOP holder and the recipient STAs can be completed without interference. However, when a TXOP can be shared between multiple BSSs, it may not be efficient in terms of fairness to maintain the NAV of STAs that do not participate in the TXOP sharing, and in particular to maintain the NAV of STAs that are hidden to the shared AP.

[0125] For example, it can be assumed that a shared AP and STAs that are hidden to the shared AP are located near a sharing AP in a dense network scenario. A sharing AP may transmit a multi-user request-to-send TXOP sharing (MU RTS TXS) trigger frame to a shared AP to share its TXOP with the shared AP. The STAs that are hidden to the shared AP may be able to overhear the multi-user request-to-send TXOP sharing (MU RTS TXS) trigger frame transmitted by the sharing AP but may not be able to overhear the corresponding clear-to-send (CTS) frame transmitted by the shared AP (which is transmitted by the shared AP as a response to the MU RTS TXS trigger frame). In this situation, the rules of the existing IEEE 802.11 wireless networking standards specify that the STA should maintain its NAV when it overhears the MU RTS TXS trigger frame, regardless of whether it overhears the corresponding CTS frame or not. This approach is reasonable for a scenario where a TXOP is shared within a single BSS. However, this approach can result in unfairness / inefficiency when a TXOP is shared between multiple BSSs in C-TDMA. When a TXOP is shared between multiple BSSs, the future frame exchange sequence will occur on the shared AP side rather than on the sharing AP side since the TXOP is being shared by the sharing AP with the shared AP (i.e., the shared AP essentially becomes the TXOP holder during the time period allocated for the shared AP). Thus, the STAs that are hidden to the shared AP should be able to transmit / receive data without interference but the existing rules require that the hidden STAs maintain their NAV (and thus do not allow the hidden STAs to transmit data) during the time period allocated for the shared AP, which results in unfairness / inefficiency. In the present disclosure, this issue may be referred to as fairness issue #1. Fairness issue #1 relates to the problem of allowing STAs that are hidden to a shared AP to access the channel during a time period allocated for the shared AP within the TXOP.

[0126] The STAs that are hidden to the shared AP may implement different versions of a wireless networking standard (e.g., IEEE 802.1 In, IEEE 802.1 lac, IEEE 802.1 lax, IEEE 802.1 Ibe, etc.) and thus may behave differently in terms of setting their respective NAVs. It is desirable that the hidden STAs are offered equivalent channel access opportunity during a time period allocated for the shared AP, regardless of the version of the wireless networking standard they implement. In the present disclosure, this issue may be referred to as fairnessissue #2. Fairness issue #2 relates to the problem of ensuring that STAs that are hidden to a shared AP can fairly try to access the channel (given equivalent channel access opportunity) during the time period allocated for the shared AP regardless of the version of the wireless networking standard they implement.

[0127] Before addressing the two fairness issues, the behavior of STAs (including legacy STAs) that are hidden to a shared AP are described for a situation where the STAs are only able to overhear the MU RTS TXS trigger frame transmitted by the sharing AP.

[0128] The following scenario is considered. A sharing AP and a shared AP may participate in C-TDMA. The sharing AP may transmit a MU RTS TXS trigger frame to the shared AP to share its TXOP with the shared AP. The MU RTS TXS trigger frame may include a duration / ID field that indicates a NAV protection duration and a user info field that indicates a time period allocated for the shared AP within the TXOP. The NAV protection duration and the duration of the time period allocated for the shared AP may be the same or be almost the same (only have negligible differences). The shared AP may transmit a CTS frame as a response to the MU RTS TXS trigger frame but the STAs that are hidden to the shared AP may not be able to overhear the CTS frame.

[0129] In the above-described scenario, STAs that are hidden to the shared AP may behave as follows depending on the version of the wireless networking standard that they implement. It is assumed that a STA that overhears the MU RTS TXS trigger frame uses information from the MU RTS TX trigger frame to update its NAV.

[0130] Legacy STAs except IEEE 80.1 Ibe STA: permitted to reset its NAV after the NAV timeout (NAVtimeout) has expired.

[0131] IEEE 802.1 Ibe STA: should not reset its NAV after the NAVTimeout has expired.

[0132] IEEE 802.1 Ibn STA (future STAs): For a STA associated with the sharing AP (case #1), the STA may maintain NAV or not during the NAV protection duration indicated by the duration / ID field of the MU RTS TXS trigger frame or the duration of the time period allocated for the shared AP indicated by the user info field of the MU RTS TXS trigger frame. For a STA that is not associated with the sharing AP (case #2), the STA may implement behavior #1, behavior #2, or behavior #3. With behavior #1, the STA behaves according to the behavior specified by IEEE 802.1 Ibe. With behavior #2, the STA resets its NAV after the NAVtimeout has expired and tries to access the channel during the time period allocated for the shared AP. With behavior #3, the STA behaves according to case #1 mentioned above.

[0133] TXOP sharing techniques to address fairness issue #1 and fairness issue #2 are now described, taking into consideration the above-described heterogenous behaviors of STAs implementing different versions of a wireless networking standard.

[0134] To address fairness issue #1 and fairness issue #2, after the sharing AP shares its TXOP with the shared AP, STAs hidden to the shared AP should not be restricted from accessing the channel during the time period allocated for the shared AP. At the same time, the hidden STAs should be guaranteed equivalent channel access opportunity regardless of the version of the wireless networking standard they implement. Stated differently, when STAs implementing different versions of a wireless networking standard (e.g., IEEE 802.1 lax, IEEE 802.1 Ibe, IEEE 802.11.bn, etc.) overhear the MU RTS TXS trigger frame, a solution is needed to ensure fairness between them by considering their different behaviors (e.g., in terms of maintaining and resetting NAV).

[0135] In an embodiment, the NAV protection duration indicated by the duration / ID field of the MU RTS TXS trigger frame is set to be shorter than the duration of the time period allocated for the shared AP indicated by the user info field of the MU RTS TXS trigger frame. For example, the value of the duration / ID field of the MU RTS TXS trigger frame can be set as follows.

[0136] The value included in the duration / ID field of the MU RTS TXS trigger frame may be set to (CTS response time + @(pending time)). Here, “CTS response time” may be (l*aSIFSTime + CTS Time), where “aSIFSTime” is a duration of a SIFS interval and “CTS Time” is a duration of a CTS frame transmission. Also, “@(pending time)” may be a short amount of time (a predefined margin duration) that allows a shared AP to initiate a transmission within its BSS.

[0137] While a MU RTS TXS trigger frame and CTS frame are mentioned above as examples of frames that can be used for TXOP sharing, it should be appreciated that the TXOP sharing techniques described herein can be implemented using other types of control frames. Thus, the use of MU RTS TXS trigger frame and CTS frame should be regarded as illustrative rather than limiting.

[0138] Figure 10 is a diagram showing an example where the NAV protection duration is set to correspond to the sum of the duration of a response frame transmission and a predefined margin duration, according to some embodiments.

[0139] As shown in the diagram, the sharing AP may transmit a control frame 1005 to the shared AP to share a TXOP owned by the sharing AP with the shared AP. The control frame 1005 may include a first field that indicates a NAV protection duration and a second fieldthat indicates a time period allocated for the shared AP within the TXOP. In this example, the NAV protection duration (the duration of the “NAV Protection Time” shown in the diagram) is set to a duration corresponding to the sum of “CTS response time” and “@(pending time).” Notably, the NAV protection duration is shorter than the duration of the time period allocated for the shared AP (the duration of the “Allocate Time Period” shown in the diagram). The shared AP may transmit a response frame 1010 to the sharing AP as a response to the control frame 1005. The shared AP may then initiate a frame exchange sequence 1015 within its BSS after transmitting the response frame 1010. In an embodiment, the control frame 1005 is a MU RTS TXS trigger frame and the response frame 1010 is a CTS frame. In an embodiment, the first field is a duration / ID field of a MU RTS TXS trigger frame and the second field is a user info field of the MU RTS TXS trigger frame. Setting the NAV protection duration in this way allows STAs that are hidden to the shared AP to access the channel during the time period allocated for the shared AP (at the end of the “NAV Protection Time”).

[0140] As another example, the value of the duration / ID field of the MU RTS TXS trigger frame may be set to correspond to the duration of a NAV timeout for STAs that are hidden to the shared AP and not recipients of the MU RTS TXS trigger frame. For example, the value of the duration / ID field of the MU RTS TXS trigger frame can be set in the same way as described above except “@(pending time)” can be set as follows.

[0141] “@(pending time)” may be set to (T_NAVtimeout period - CTS response time). Here, “T NAVtimeout period” is the duration of a NAV timeout and “CTS response time” may be (l*aSIFSTime + CTS Time), where “aSIFSTime” is a duration of a SIFS interval and “CTS Time” is a duration of a CTS frame transmission. “T NAVtimeout period” may be set to (2*aSIFSTime + CTS Time + aRXPHYStartDelay + 2*aSlotTime), where “aSIFSTime” is a duration of a SIFS interval, “CTS Time” is a duration of a CTS frame transmission, “aRXPHYStartDelay” is a PHY reception delay, and “aSlotTime” is a duration of a slot. Thus, “@(pending time)” may be defined as follows:@(pending time) = T_NAVtimeout period - CTS response time = (2*aSIFSTime + CTS Time+aRXPHYStartDelay + 2*aSlotTime) - (PaSIFST time + CTS Time) = l*aSIFSTime +aRXPHYStartDelay + 2*aSlotTime

[0142] Using the above equation, the value included in the duration / ID field of the MU RTS TXS trigger frame may correspond to a NAV timeout duration.

[0143] Figure 11 is a diagram showing example where the NAV protection duration is set to correspond to a NAV timeout duration, according to some embodiments.

[0144] As shown in the diagram, the sharing AP 1150 may transmit a control frame 1105 to the shared AP 1160 to share a TXOP owned by the sharing AP 1150 with the shared AP 1160. The control frame 1105 may include a first field that indicates a NAV protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP. In this example, the NAV protection duration (the duration of the “NAV Protection Time” shown in the diagram) is set to correspond to the duration of a NAV timeout. Notably, the NAV protection duration is shorter than the duration of the time period allocated for the shared AP 1160 (the duration of the “Allocate Time Period” shown in the diagram). The shared AP 1160 may transmit a response frame 1110 to the sharing AP 1150 as a response to the control frame 1105. The shared AP 1160 may then initiate a frame exchange sequence 1115 within its BSS (e.g., transmit / receive data to / from STA 1165) after transmitting the response frame 1110. In an embodiment, the control frame 1105 is a MU RTS TXS trigger frame and the response frame 1110 is a CTS frame. In an embodiment, the first field is a duration / ID field of a MU RTS TXS trigger frame and the second field is a user info field of the MU RTS TXS trigger frame. Setting the NAV protection duration in this way allows STAs that are hidden to the shared AP (e.g., STA 1155) to access the channel within the time period allocated for the shared AP (at the end of the “NAV Protection Time”).

[0145] The TXOP sharing technique described above (e.g., setting the NAV protection duration to be shorter than the duration of the time period allocated for the shared AP) may address fairness issue #1 and fairness issue #2 mentioned above. However, this TXOP sharing technique may introduce another problem.

[0146] Due to the consideration of the fairness issue, there may be a situation where low latency traffic occurs on the sharing AP side just before the shared AP returns the unused portion of the TXOP to the sharing AP. Low latency traffic is traffic that needs to be transmitted urgently. Low latency traffic may occur randomly / aperiodically. However, the sharing AP may not be able to transmit its low latency traffic if the sharing AP cannot use the returned TXOP due to hidden STAs occupying the channel.

[0147] Figure 12 is a diagram showing a situation where low latency traffic occurs on the sharing AP side but the sharing AP is not able to transmit the low latency traffic even after the shared AP returns the TXOP to the sharing AP, according to some embodiments.

[0148] As shown in the diagram, the sharing AP may transmit a control frame 1205 to the shared AP to share a TXOP owned by the sharing AP with the shared AP. The control frame 1105 may include a first field that indicates a NAV protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP. The NAV protectionduration may be set to be shorter than the duration of the time period allocated for the shared AP to allow STAs that are hidden to the shared AP to access the channel during the time period allocated for the shared AP, as described herein above. The shared AP may transmit a response frame 1210 to the sharing AP as a response to the control frame 1205. The shared AP may then initiate a frame exchange sequence 1215 within its BSS after transmitting the response frame 1210. STAs that are hidden to the shared AP may access the channel after the NAV protection duration (after the “NAV Protection Time” shown in the diagram) if the channel is idle (based on using a CS (carrier sensing) mechanism). In this example, it is assumed that STAs that are hidden to the shared AP sense that the channel is idle and perform a frame exchange sequence 1220 during the time period allocated for the shared AP. Also, in this example, it is assumed that the sharing AP has low latency traffic to transmit during the shared AP’s frame exchange sequence 1215. After the shared AP’s frame exchange sequence 1215 is complete, the shared AP may transmit a TXOP return frame 1225 to the sharing AP to return the TXOP to the sharing AP. However, the sharing AP may not be able to receive the TXOP return frame 1225 due to a collision. Thus, the sharing AP may not be able to reclaim the TXOP and transmit the low latency traffic. In this case, the sharing AP may fail to use the TXOP returned by the shared AP and thus may not be able to transmit low latency traffic in a timely manner.

[0149] By allowing STAs that are hidden to the shared AP to occupy the channel during the time period allocated for the shared AP, the sharing AP nay not be able to reclaim the TXOP, which in turn does not allow the sharing AP to transmit low latency traffic.

[0150] Thus, there is a need to be able to address the fairness issues for STAs that are hidden to the shared AP while at the same time supporting low latency traffic that occurs on the sharing AP side.

[0151] As mentioned above, the fairness issues can be addressed by setting the NAV protection duration indicated by the duration / ID field of the MU RTS TXS trigger frame to be shorter than the duration of the time period allocated for the shared AP within the TXOP. This allows the STAs that are hidden to the shared AP to try to access the channel during the time period allocated for the shared AP.

[0152] In an embodiment, to support low latency traffic that occurs on the sharing AP side, the sharing AP may allocate time for the shared AP in multiple segments. Stated differently, time within the TXOP is not allocated to the shared AP all at once (in a single chunk) but may be allocated to the shared AP in multiple smaller segments. This may allow the sharing AP to transmit low latency traffic with less delay. This is because, according to TXOP sharing rules, the sharing AP cannot transmit low latency traffic until the time period allocated for the sharedAP is over because the shared AP is technically the TXOP holder during that time period. If the TXOP is shared in multiple smaller segments, there is a higher probably that the shared AP will use the entire segment, which may help prevent the probability of the TXOP return frame collision shown in Figure 12. At the same time, the sharing AP may have an opportunity to transmit low latency traffic sooner.

[0153] In an embodiment, a shared AP that has been allocated a time period within a TXOP owned by a sharing AP can return the TXOP back to the sharing AP using an implicit TXOP return approach or an explicit TXOP return approach. The implicit TXOP return approach and the explicit TXOP return approach are further described herein below.

[0154] One or more of the features described herein may be combined to support low latency transmission on the sharing AP side while at the same time addressing fairness issues for hidden STAs. For example, the NAV protection duration indicated by the duration / ID field of the MU RTS TXS trigger frame may set to be shorter than the duration of the time period allocated for the shared AP, the sharing AP may allocate time for the shared AP within the TXOP in multiple smaller segments, and the shared AP may be able to return / relinquish the TXOP depending on the traffic situation at the shared AP to allow the sharing AP to reclaim the TXOP, if needed. The shared AP may return / relinquish the TXOP using an implicit TXOP return approach or an explicit TXOP return approach.Implicit TXOP Return

[0155] With the implicit TXOP return approach, a shared AP that has been allocated a time period within a TXOP can return / relinquish the TXOP to the sharing AP without providing an explicit indication to the sharing AP (e.g., without transmitting a separate frame or indication bit to the sharing AP).

[0156] The following parameter may be used for an implicit TXOP return:

[0157] Difif = (End of TXOP allocate time - End of NAV protection time)

[0158] On the sharing AP side, “End of NAV protection time” may be the end of the NAV protection time period for a frame exchange sequence in the shared AP’s BSS during the time period allocated for the shared AP within the TXOP, which can be determined based on overhearing frames transmitted during the frame exchange sequence. Also, “End of TXOP allocate time” may be the end of the time period allocated by the sharing AP for the shared AP within the TXOP.

[0159] On the shared AP side, “End of NAV protection time” may be the end of the NAV protection time period for a frame exchange sequence in the shared AP’s BSS during the timeperiod allocated for the shared AP within the TXOP. The NAV protection time period may be set to protect the frame exchange sequence from interference form STAs that are not involved in the frame exchange sequence. Also, “End of TXOP allocate time” may be the end of the time period allocated for the shared AP within the TXOP.

[0160] The “End of TXOP allocate time” and “End of NAV protection time” of the sharing AP and the shared AP may be the same.

[0161] In an embodiment, when “Diff ’ is shorter than or equal to PIFS (Diff < =PIFS), the sharing AP and the shared AP follow the implicit TXOP return approach.

[0162] With the implicit TXOP return approach, if the sharing AP needs to reclaim the TXOP (e.g., to support low latency traffic or to share the TXOP with another / different AP), the sharing AP may perform a carrier sense of the channel at the “End of NAV protection time” and attempt to access the channel after a XIFS interval (e.g., SIFS interval) if the channel is idle. If the sharing AP does not need to reclaim the TXOP, the sharing AP may perform a carrier sense of the channel at the “End of NAV protection time” and not attempt to access the channel after the XIFS interval even though the channel is idle to allow the shared AP and / or other APs / STAs to try to access the channel.

[0163] With the implicit TXOP return approach, if the shared AP needs to resume transmission within the TXOP, the shared AP may perform a carrier sense of the channel at the “End of NAV protection time” and attempt to access the channel after a XIFS’ interval (e.g., PIFS interval) if the channel is idle. If the shared AP does not need to resume transmission within the TXOP, the shared AP may perform a carrier sense of the channel at the “End of NAV protection time” and not attempt to access the channel after the XIFS’ interval even though the channel is idle. The XIFS interval may be longer than the XIFS’ interval, which means that the sharing AP gets transmission priority over the shared AP at the “End of NAV protection time.” In an embodiment, the XIFS interval is a SIFS interval and the XIFS’ interval is a PIFS interval. It should be appreciated, however, that other interframe space intervals can be used for the XIFS interval and / or the XIFS’ interval, so long as the duration of the XIFS interval is shorter than the duration of the XIFS’ interval.

[0164] In an embodiment, when “Diff’ is greater than XIFS’ (e.g., PIFS), the sharing AP and the shared AP follow the explicit TXOP return approach, which is further described elsewhere herein. In an embodiment, the shared AP performs a frame exchange by pre-segmentation of PPDU (e.g., such that the end of the data transmission closely aligns with the end of the time period allocated for the shared AP) to prevent a scenario where “Diff’ is greater than XIFS’ (e.g., and potentially avoid the need for an explicit TXOP return).

[0165] It is noted that a situation where “Diff ’ is less than zero cannot occur because the shared AP should not set the NAV protection duration for its frame exchange sequence to be longer than the duration of the time period allocated for the shared AP.

[0166] Figure 13 is a diagram showing a scenario where a sharing AP successfully accesses the channel following an implicit TXOP return approach, according to some embodiments.

[0167] As shown in the diagram, the sharing AP may transmit a control frame 1305 to the shared AP. The control frame 1305 may include a first field that indicates a NAV protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP. The NAV protection duration may be set to be shorter than the duration of the time period allocated for the shared AP to allow STAs that are hidden to the shared AP to access the channel during the time period allocated for the shared AP, as described herein above. The shared AP may transmit a response frame 1310 to the sharing AP as a response to the control frame 1305. The shared AP may then initiate a frame exchange sequence 1315 within its BSS after transmitting the response frame 1310. A NAV may be set for frame exchange sequence 1315 (shown in the diagram as “NAV set by shared AP’s BSS frame exchange”). In this example, “Diff’ (the difference between “End of TXOP allocate time” and “End of NAV protection time”) is shorter than or equal to PIFS. Also, in this example, it is assumed that the sharing AP needs to reclaim the TXOP. Thus, the sharing AP may start transmitting after a SIFS interval after the end of the NAV protection time period for the frame exchange sequence 1315. For example, the sharing AP may resume a frame exchange sequence 1320 or share the TXOP with another AP. The shared AP may be prevented from resuming its frame exchange sequence 1325 after a PIFS interval after the end of the NAV protection time period because the sharing AP has reclaimed the TXOP. Thus, in this case, the time period allocated for the shared AP (shown in the diagram as “Allocated Time Period”) is not extended.

[0168] Figure 14 is a diagram showing a scenario where a shared AP successfully accesses the channel following an implicit TXOP return approach, according to some embodiments.

[0169] As shown in the diagram, the sharing AP may transmit a control frame 1405 to the shared AP. The control frame 1405 may include a first field that indicates a NAV protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP. The NAV protection duration may be set to be shorter than the duration of the time period allocated for the shared AP to allow STAs that are hidden to the shared AP to access the channel during the time period allocated for the shared AP, as described herein above. The shared AP may transmit a response frame 1410 to the sharing AP as a response to the control frame 1405. The shared AP may then initiate a frame exchange sequence 1415 within its BSSafter transmitting the response frame 1410. A NAV may be set for frame exchange sequence 1415 (shown in the diagram as “NAV set by shared AP’s BSS frame exchange”). In this example, “Diff” (the difference between “End of TXOP allocate time” and “End of NAV protection time”) is shorter than or equal to PIFS. Also, in this example, it is assumed that the sharing AP does not need to reclaim the TXOP. Thus, at the end of the NAV protection time period for the frame exchange sequence 1415, the sharing AP may refrain from resuming its frame exchange sequence 1420. Also, in this example, it is assumed that the shared AP needs to resume transmission. Thus, the shared AP may start transmitting after a PIFS interval after the end of the NAV protection time period for the frame exchange sequence 1415 to resume the frame exchange sequence 1425. Thus, in this case, the time period allocated for the shared AP (shown in the diagram as “Allocated Time Period”) is extended.Explicit TXOP Return

[0170] With the explicit TXOP return approach, a shared AP that has been allocated a time period within a TXOP can return / relinquish the TXOP by providing an explicit indication to the sharing AP. The shared AP may return / relinquish the TXOP if the shared AP has no more data to transmit / receive within its BSS or there is not enough time remaining in the time period allocated for the shared AP to transmit the buffered data.

[0171] As will be described in additional detail herein, the explicit indication may be provided using a TXOP return frame (e.g., a contention free end (CF-END) frame) or a TXOP return indication included in a frame (e.g., downlink frame or uplink frame) transmitted during a frame exchange sequence in the shared AP’s BSS.

[0172] The same parameters that are used in the implicit TXOP return approach and described above such as “Diff,” “End of TXOP allocate time,” and “End of NAV protection time” may also be used for an explicit TXOP return.

[0173] In an embodiment, when “Diff’ is greater than PIFS, the sharing AP and the shared AP follow the explicit TXOP return approach.

[0174] In a first embodiment of the explicit TXOP return approach, the shared AP may return the TXOP to the sharing AP using a TXOP return frame (if there is enough time remaining in the time period allocated for the shared AP to transmit the TXOP return frame). The TXOP return frame may be a CF-END frame or other type of control frame. The shared AP may decide whether to transmit the TXOP return frame or not, for example, depending on whether there is enough time remaining in the time period allocated for the shared AP or not.

[0175] With the first embodiment of the explicit TXOP return approach, if the shared AP does not need to resume transmission within the TXOP (e.g., the shared AP has no more data to transmit during the time period allocated for the shared AP), the shared AP may transmit a TXOP return frame to the sharing AP to return the TXOP to the sharing AP before an end of the time period.

[0176] Also, with the first embodiment of the explicit TXOP return approach, if the sharing AP needs to reclaim the TXOP (e.g., to support low latency traffic or to share the TXOP with another / different AP), the sharing AP may perform a carrier sense of the channel after receiving the TXOP return frame from the shared AP and attempt to access the channel after a XIFS interval (e.g., SIFS interval) if the channel is idle. If the sharing AP does not need to reclaim the TXOP, the sharing AP may perform a carrier sense of the channel after receiving the TXOP return frame from the shared AP and not attempt to access the channel after the XIFS interval even though the channel is idle to allow the shared AP and / or other APs / STAs to try to access the channel. This may mean that the sharing AP relinquishes the TXOP and makes the channel available for contention-based access.

[0177] Figure 15 is a diagram showing a scenario where a sharing AP resumes transmission after receiving an explicit TXOP return frame, according to some embodiments.

[0178] As shown in the diagram, the sharing AP may transmit a control frame 1505 to the shared AP. The control frame 1505 may include a first field that indicates a NAV protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP. The NAV protection duration may be set to be shorter than the duration of the time period allocated for the shared AP to allow STAs that are hidden to the shared AP to access the channel during the time period allocated for the shared AP, as described herein above. The shared AP may transmit a response frame 1510 to the sharing AP as a response to the control frame 1505. The shared AP may then initiate a frame exchange sequence 1515 within its BSS after transmitting the response frame 1510. In this example, it is assumed that the shared AP does not have additional data to transmit after the frame exchange sequence 1515. Thus, the shared AP may transmit a TXOP return frame 1520 to return the TXOP back to the sharing AP. Thus, in this case, the time period allocated for the shared AP (shown in the diagram as “Allocated Time Period”) is not extended. In this example, it is assumed that the sharing AP needs to reclaim the TXOP. Thus, the sharing AP may resume its frame exchange sequence 1525 in its BSS after receiving the TXOP return frame 1520.

[0179] In a second embodiment of the explicit TXOP return approach, the shared AP may return the TXOP to the sharing AP by including an explicit TXOP return indication in a frametransmitted during a frame exchange sequence in the shared AP’s BSS. The explicit TXOP return indication may be included in the frame preamble (e.g., in a SIG field) or a MAC header field. The explicit TXOP return indication may indicate to the sharing AP that the sharing AP can use the channel at the end of the current frame exchange sequence in the shared AP’s BSS if certain conditions are satisfied (e.g., the channel is idle). The sharing AP may determine when the frame exchange sequence in the shared AP’s BSS will end based on the NAV protection duration indicated by the frame exchange sequence (e.g., indicated by a duration / ID field of a frame transmitted during the frame exchange sequence).

[0180] With the second embodiment of the explicit TXOP return approach, if the shared AP does not need to resume transmission within the TXOP (e.g., the shared AP has no more data to transmit during the time period allocated for the shared AP), the shared AP may include a TXOP return indication in a frame transmitted during the frame exchange sequence (e.g., a downlink data frame, downlink block acknowledgement (BA) frame, and / or a trigger frame) to return the TXOP to the sharing AP before an end of the time period. In an embodiment, when STAs associated with the shared AP receive a frame that includes the TXOP return indication, they may also include a TXOP return indication in the frames they transmit (e.g., a BA frame or normal ACK frame that is transmitted as a response to a data frame transmitted by the shared AP). The TXOP return indication may be included in the frame preamble or a MAC header field. Having STAs include the TXOP return indication in the frames they transmit may allow the sharing AP to recognize that the shared AP is returning the TXOP even when the sharing AP is not able to overhear frames transmitted by the shared AP to the associated STAs. Having the TXOP return indication included in the frame preamble or MAC header field may increase the probability of the sharing AP being able to detect the TXOP return indication (e.g., the sharing AP may be able to detect the TXOP return indication even when the sharing AP cannot fully decode the MAC protocol data unit (MPDU)).

[0181] Also, with the second embodiment of the explicit TXOP return approach, if the sharing AP needs to reclaim the TXOP (e.g., to support low latency traffic or to share the TXOP with another / different AP), the sharing AP may perform a carrier sense of the channel after the end of the NAV protection time period for the frame exchange sequence in the shared AP’s BSS and attempt to access the channel after an interframe space interval (e.g., PIFS interval) if the channel is idle. If the sharing AP does not need to reclaim the TXOP, the sharing AP may perform a carrier sense of the channel at the end of the end of the NAV protection time period for the frame exchange sequence in the shared AP’s BSS and not attempt to access the channel after the interframe space interval (e.g., PIFS interval) even though the channel is idle.

[0182] Figure 16 is a diagram showing a scenario where a sharing AP resumes transmission after detecting an explicit TXOP return indication, according to some embodiments.

[0183] As shown in the diagram, the sharing AP may transmit a control frame 1605 to the shared AP. The control frame 1605 may include a first field that indicates a NAV protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP. The NAV protection duration may be set to be shorter than the duration of the time period allocated for the shared AP to allow STAs that are hidden to the shared AP to access the channel during the time period allocated for the shared AP, as described herein above. The shared AP may transmit a response frame 1610 to the sharing AP as a response to the control frame 1605. During the time period allocated for the shared AP, the shared AP may transmit a data frame 1615 to a non-AP STA that is associated with the shared AP. In this example, it is assumed that the shared AP does not have any additional data to transmit after transmitting the data frame 1615. Thus, the shared AP may include a TXOP return indication in the data frame 1615 (as depicted by the shading in the data frame 1615), which the sharing AP may overhear. The non-AP STA that is associated with the shared AP may transmit a BA frame 1620 to the shared AP as a response to the data frame 1615. The non-AP STA may also include a TXOP return indication in the BA frame 1620 (as depicted by the shading in the BA frame 1620) if it detects the TXOP return indication in the data frame 1615. The sharing AP may recognize that the shared AP is returning the TXOP to the sharing AP based on detecting the TXOP return indication in the data frame 1615 and / or the TXOP return indication in the BA frame 1620. Thus, in this case, the time period allocated for the shared AP (shown in the diagram as “Allocated Time Period”) is not extended. In this example, it is assumed that the sharing AP needs to reclaim the TXOP and thus the sharing AP may resume its frame exchange sequence 1625 in its BSS after a PIFS interval after the end of the NAV protection time period for the frame exchange sequence in the shared AP’s BSS.

[0184] In an embodiment, if the sharing AP detects an explicit TXOP return indication and the sharing AP does not need to reclaim the TXOP, the sharing AP may transmit a control frame to the shared AP after an interframe space interval after the end of the NAV protection time period for the frame exchange sequence in the shared AP’s BSS to reallocate the TXOP to the shared AP.

[0185] The sharing AP may detect the explicit TXOP return indication by overhearing frames transmitted during the frame exchange sequence in the shared AP’s BSS. If the sharing AP detects the explicit TXOP return indication, it may know that the shared AP will return the TXOP to the sharing AP at the end of the NAV protection time period for the frame exchangesequence in the shared AP’s BSS. As mentioned above, if the sharing AP needs to reclaim the TXOP (e.g., to support low latency traffic or to share the TXOP with another / different AP), the sharing AP may perform a carrier sense of the channel after the end of the NAV protection time period for the frame exchange sequence in the shared AP’s BSS and attempt to access the channel after an interframe space interval (e.g., PIFS interval) if the channel is idle. However, if the sharing AP does not need to reclaim the TXOP, the sharing AP may perform a carrier sense of the channel at the end of the NAV protection time period for the frame exchange sequence in the shared AP’s BSS and not attempt to access the channel after the interframe space interval (e.g., PIFS) even though the channel is idle and transmit a control frame to the shared AP to reallocate the TXOP to the shared AP.

[0186] If the shared AP has additional data to transmit but there is not enough time remaining the time period allocated for the shared AP to transmit the additional data, the shared AP may wait for the sharing AP to reallocate the TXOP to the shared AP and resume its frame exchange sequence after the TXOP has been reallocated to the shared AP.

[0187] Figure 17 is a diagram showing a scenario where a sharing AP reallocates the TXOP to the shared AP after detecting an explicit TXOP return indication, according to some embodiments.

[0188] As shown in the diagram, the sharing AP may transmit a control frame 1705 to the shared AP. The control frame 1705 may include a first field that indicates a NAV protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP. The NAV protection duration may be set to be shorter than the duration of the time period allocated for the shared AP to allow STAs that are hidden to the shared AP to access the channel during the time period allocated for the shared AP, as described herein above. The shared AP may transmit a response frame 1710 to the sharing AP as a response to the control frame 1705. During the time period allocated for the shared AP, the shared AP may transmit a data frame 1715 to a non-AP STA that is associated with the shared AP. In this example, it is assumed that the shared AP does not have any additional data to transmit after transmitting the data frame 1715. Thus, the shared AP may include a TXOP return indication in the data frame 1715 (as depicted by the shading in the data frame 1715), which the sharing AP may overhear. The non-AP STA that is associated with the shared AP may transmit a BA frame 1720 to the shared AP as a response to the data frame 1715. The non-AP STA may also include a TXOP return indication in the BA frame 1620 (as depicted by the shading in the BA frame 1620) if it detects the TXOP return indication in the data frame 1615. The sharing AP may recognize that the shared AP is returning the TXOP to the sharing AP based on detectingthe TXOP return indication in the data frame 1615 and / or the TXOP return indication in the BA frame 1720. Thus, in this case, the time period allocated for the shared AP (shown in the diagram as “Allocated Time Period”) is not extended. In this example, it is assumed that the sharing AP does not need to reclaim the TXOP and thus the sharing AP may transmit another control frame 1725 to the shared AP after a PIFS interval after the end of the NAV protection time period for the frame exchange sequence in the shared AP’s BSS to reallocate the TXOP to the shared AP. The shared AP may transmit a response frame 1730 as a response to the control frame 1725 and resume its frame exchange sequence 1735 in the shared AP’s BSS.

[0189] In an embodiment, the sharing AP controls whether the shared AP follows the implicit TXOP return approach or the explicit TXOP return approach. For example, the sharing AP may request that the shared AP provide an explicit TXOP return indication. If the shared AP receives such a request, the shared AP may follow the explicit TXOP return approach described herein. However, if the shared AP does not receive such a request, the shared AP may follow the implicit TXOP return approach described herein.

[0190] The TXOP sharing techniques described herein may allow STAs that are hidden to the shared AP to attempt to access the channel during a time period allocated for the shared AP, which may address the fairness issues mentioned herein and increase network utilization in a situation where a TXOP is being shared between different BSSs. Also, the TXOP sharing techniques described herein may support aperiodic low latency traffic that occurs on the sharing AP side by segmenting the time allocated for the shared AP within the TXOP and using an implicit TXOP return approach and / or an explicit TXOP return approach.

[0191] Turning now to Figure 18, a method 1800 will be described for sharing a TXOP with a shared AP, in accordance with an example embodiment. The method 1800 may be performed by a sharing AP. The sharing AP may be implemented by a wireless device (e.g., wireless device 104).

[0192] Additionally, although shown in a particular order, in some embodiments the operations of the method 1800 (and the other methods shown in the other figures) may be performed in a different order. For example, although the operations of the method 1800 are shown in a sequential order, some of the operations may be performed in partially or entirely overlapping time periods.

[0193] At operation 1805, the sharing AP generates a control frame (e.g., MU RTS TXS trigger frame) for indicating that the sharing AP is sharing the TXOP with the shared AP, wherein the control frame includes a first field that indicates a NAV protection duration and a second field that indicates a time period (e.g., one of a plurality of time periods) allocated for theshared AP within the TXOP, wherein the NAV protection duration is set to be shorter than a duration of the time period allocated for the shared AP. In an embodiment, the NAV protection duration is set to a duration corresponding to a sum of a response frame transmission duration and a predefined margin duration (e.g., CTS response time + @(pending time)). In an embodiment, the NAV protection duration is set to a duration corresponding to a NAV timeout duration. In an embodiment, the time period allocated for the shared AP is one of a plurality of time periods allocated for the shared AP within the TXOP.

[0194] At operation 1810, the sharing AP transmits the control frame to the shared AP.

[0195] Also, as shown in the diagram, the sharing AP may follow an implicit TXOP return approach at block 1815 or follow an explicit TXOP approach at block 1820. Example operations for following the implicit TXOP return approach are shown in Figure 19 and examples operations for following the implicit TXOP return approach are shown in Figure 20.

[0196] Turning now to Figure 19, a method 1900 will be described for following an implicit TXOP return approach, in accordance with an example embodiment. The method 1900 may be performed by a sharing AP. The sharing AP may be implemented by a wireless device (e.g., wireless device 104).

[0197] At operation 1905, the sharing AP determines an end of a NAV protection time period for a frame exchange sequence involving the shared AP within the time period allocated for the shared AP.

[0198] At operation 1910, the sharing AP determines whether it needs to reclaim the TXOP. If the sharing AP needs to reclaim the TXOP, the flow moves to operation 1915. At operation 1915, the sharing AP attempts to access a channel after a first interframe space (e.g., SIFS) interval after the end of the NAV protection time period, wherein the first interframe space interval is shorter than a second interframe space (e.g., PIFS) interval that is used by the shared AP after the end of the NAV protection time period. If the sharing AP does not need to reclaim the TXOP, the flow moves to operation 1920. At operation 1920, the sharing AP does not attempt to access a channel after a first interframe space (e.g., SIFS) interval after the end of the NAV protection time period.

[0199] In an embodiment, the attempt to access the channel is made when a difference between an end of the time period allocated for the shared AP and the end of the NAV protection time period is shorter than or equal to the second interframe space interval (e.g., “Difif ’ <= PIFS).

[0200] Turning now to Figure 20, a method 2000 will be described for following an explicit TXOP return approach, in accordance with an example embodiment. The method 2000 may beperformed by a sharing AP. The sharing AP may be implemented by a wireless device (e.g., wireless device 104).

[0201] At operation 2005, the sharing AP receives a TXOP return frame from the shared AP.

[0202] At operation 2010, the sharing AP determines whether it needs to reclaim the TXOP. If the sharing AP needs to reclaim the TXOP, the flow moves to operation 2015. At operation 2015, the sharing AP attempts to access a channel after an interframe space (e.g., SIFS) interval after receiving the TXOP return frame. If the sharing AP does not need to reclaim the TXOP, the flow moves to operation 2020. At operation 2020, the sharing AP does not attempt to access a channel after an interframe space (e.g., SIFS) interval after receiving the TXOP return frame.

[0203] In an embodiment, the sharing AP determines an end of a NAV protection time period for a frame exchange sequence involving the shared AP within the time period allocated for the shared AP. Responsive to detecting a TXOP return indication in the frame exchange sequence, the sharing AP may attempt to access a channel after an interframe space interval after the end of the NAV protection time period if the sharing AP needs to reclaim the TXOP. In an embodiment, no attempt to access the channel is made after the interframe space interval after the end of the NAV protection time period if the sharing AP does not need to reclaim the TXOP. In an embodiment, the interframe space interval is a PIFS interval.

[0204] In an embodiment, the sharing AP transmits a second control frame to the shared AP after the interframe space interval after the end of the NAV protection time period to reallocate time within the TXOP to the shared AP if the sharing AP does not need to reclaim the TXOP.

[0205] In an embodiment, the sharing AP transmits a request to the shared AP to provide an explicit TXOP return indication. The shared AP may provide the explicit TXOP return indication in response to receiving the request, wherein the explicit TXOP return indication is provided in the form of a TXOP return frame (e.g., CF-END frame) or a TXOP return indication in a frame transmitted during a frame exchange sequence during the time period allocated for the shared AP.

[0206] Turning now to Figure 21, a method 2100 will be described for sharing in a transmission opportunity (TXOP) owned by a sharing AP, in accordance with an example embodiment. The method 2100 may be performed by a shared AP. The shared AP may be implemented by a wireless device (e.g., wireless device 104).

[0207] At operation 2105, the shared AP receives a control frame (e.g., MU RTS TXS trigger frame) from the sharing AP indicating that the sharing AP is sharing the TXOP owned by thesharing AP with the shared AP, wherein the control frame includes a field that indicates a time period of a plurality of time periods allocated for the shared AP within the TXOP.

[0208] At operation 2110, responsive to receiving the control frame, the shared AP transmits a response frame (e.g., CTS frame) to the sharing AP.

[0209] At operation 2115, the shared AP initiates a frame exchange sequence within a BSS of the shared AP during the time period.

[0210] Also, as shown in the diagram, the shared AP may follow an implicit TXOP return approach at block 2120 or follow an explicit TXOP approach at block 2125. Example operations for following the implicit TXOP return approach are shown in Figure 22 and examples operations for following the implicit TXOP return approach are shown in Figure 23.

[0211] Turning now to Figure 22, a method 2200 will be described for following an implicit TXOP return approach, in accordance with an example embodiment. The method 2200 may be performed by a shared AP. The shared AP may be implemented by a wireless device (e.g., wireless device 104).

[0212] At operation 2205, the shared AP determines whether it needs to resume transmission within the TXOP. If the shared AP needs to resume transmission within the TXOP, the flow moves to operation 2210. At operation 2210, the shared AP attempts to access a channel after a second interframe space (e.g., PIFS) interval after the end of the NAV protection time period for the frame exchange sequence, wherein the second interframe space interval is longer than a first interframe space (e.g., SIFS) interval that is used by the sharing AP after the end of the NAV protection time period. If the shared AP does not need to resume transmission within the TXOP, the flow moves to operation 2215. At operation 2215, the shared AP does not attempt to access a channel after a second interframe space (e.g., PIFS) interval after the end of the NAV protection time period.

[0213] In an embodiment, the attempt to access the channel is made when a difference between an end of the time period allocated for the shared AP and the end of the NAV protection time period is shorter than or equal to the second interframe space interval (e.g., “Difif” <= PIFS).

[0214] Turning now to Figure 23, a method 2300 will be described for following an explicit TXOP return approach, in accordance with an example embodiment. The method 2300 may be performed by a shared AP. The shared AP may be implemented by a wireless device (e.g., wireless device 104).

[0215] At operation 2305, the shared AP transmits a TXOP return frame to the sharing AP after the frame exchange sequence to return the TXOP to the sharing AP before an end of the time period allocated for the shared AP.

[0216] In an embodiment, the TXOP return frame is transmitted when a difference between an end of the time period and an end of a NAV protection time period for the frame exchange sequence is longer than a PIFS interval (e.g., “Diff ’ > PIFS).

[0217] In an embodiment, the shared AP includes a TXOP return indication in a frame transmitted during the frame exchange sequence to return the TXOP to the sharing AP before an end of the time period. In an embodiment, the shared AP receives a second control frame from the sharing AP after the frame exchange sequence indicating that the sharing AP is reallocating time within the TXOP to the shared AP. Responsive to receiving the second control frame, the shared AP may transmit a second response frame to the sharing AP and initiate a second frame exchange sequence within the BSS of the shared AP during the reallocated time.

[0218] In an embodiment, responsive to receiving a request from the sharing AP to provide an explicit TXOP return indication, the shared AP follows an explicit TXOP return approach. In an embodiment, responsive to not receiving a request from the sharing AP to provide an explicit TXOP return indication, the shared AP follows an implicit TXOP return approach.

[0219] 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.

[0220] 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 includeone or more other hardware or software elements, including a network interface, a display device, etc.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] 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 willappear 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.

[0225] The present disclosure can be provided as a computer program product, or software, that can include a machine-readable medium having stored thereon instructions, which can be used to program a computer system (or other electronic devices) to perform a process according to the present disclosure. A machine-readable medium includes any mechanism for storing information in a form readable by a machine (e.g., a computer). In some embodiments, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium such as a read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory components, etc.

[0226] In the foregoing specification, embodiments of the disclosure have been described with reference to specific example embodiments thereof. It will be evident that various modifications can be made thereto without departing from the broader spirit and scope of embodiments of the disclosure as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Claims

CLAIMSWhat is claimed is:

1. A method performed by a sharing access point (AP) to share a transmission opportunity (TXOP) owned by the sharing AP with a shared AP, the method comprising: generating a control frame for indicating that the sharing AP is sharing the TXOP with the shared AP, wherein the control frame includes a first field that indicates a network allocation vector (NAV) protection duration and a second field that indicates a time period allocated for the shared AP within the TXOP, wherein the NAV protection duration is set to be shorter than a duration of the time period allocated for the shared AP; and transmitting the control frame to the shared AP.

2. The method of claim 1, wherein the NAV protection duration is set to a duration corresponding to a sum of a response frame transmission duration and a predefined margin duration.

3. The method of claim 1, wherein the NAV protection duration is set to a duration corresponding to a NAV timeout duration.

4. The method of claim 1, wherein the time period allocated for the shared AP is one of a plurality of time periods allocated for the shared AP within the TXOP.

5. The method of claim 4, further comprising: determining an end of a NAV protection time period for a frame exchange sequence involving the shared AP within the time period allocated for the shared AP; and attempting to access a channel after a first interframe space interval after the end of the NAV protection time period if the sharing AP needs to reclaim the TXOP, wherein the first interframe space interval is shorter than a second interframe space interval that is used by the shared AP after the end of the NAV protection time period.

6. The method of claim 5, wherein no attempt to access the channel is made after the first interframe space interval after the end of the NAV protection time period if the sharing AP does not need to reclaim the TXOP.

7. The method of claim 5, wherein the first interframe space interval is a short interframe space (SIFS) interval and the second interframe space interval is a point coordination function interframe space (PIFS) interval.

8. The method of claim 5, wherein the attempt to access the channel is made when a difference between an end of the time period allocated for the shared AP and the end of the NAV protection time period is shorter than or equal to the second interframe space interval.

9. The method of claim 4, further comprising: responsive to receiving a TXOP return frame from the shared AP, attempting to access a channel after an interframe space interval after receiving the TXOP return frame if the sharing AP needs to reclaim the TXOP.

10. The method of claim 9, wherein no attempt to access the channel is made after the interframe space interval after receiving the TXOP return frame if the sharing AP does not need to reclaim the TXOP.

11. The method of claim 9, wherein the interframe space interval is a short interframe space (SIFS) interval.

12. The method of claim 4, further comprising: determining an end of a NAV protection time period for a frame exchange sequence involving the shared AP within the time period allocated for the shared AP; and responsive to detecting a TXOP return indication in the frame exchange sequence, attempting to access a channel after an interframe space interval after the end of the NAV protection time period if the sharing AP needs to reclaim the TXOP.

13. The method of claim 12, wherein no attempt to access the channel is made after the interframe space interval after the end of the NAV protection time period if the sharing AP does not need to reclaim the TXOP.

14. The method of claim 12, wherein the interframe space interval is a point coordination function interframe space (PIFS) interval.

15. The method of claim 12, further comprising: transmitting a second control frame to the shared AP after the interframe space interval after the end of the NAV protection time period to reallocate time within the TXOP to the shared AP if the sharing AP does not need to reclaim the TXOP.

16. The method of claim 4, further comprising: transmitting a request to the shared AP to provide an explicit TXOP return indication.

17. The method of claim 16, wherein the shared AP provides the explicit TXOP return indication in response to receiving the request, wherein the explicit TXOP return indication is provided in a form of a TXOP return frame or a TXOP return indication in a frame transmitted during a frame exchange sequence during the time period allocated for the shared AP.

18. The method of claim 1, wherein the control frame is a multi-user request-to-send TXOP sharing (MU RTS TXS) trigger frame.

19. The method of claim 18, wherein the first field is a duration / ID field of the MU RTS TXS trigger frame and the second field is a user information field of the MU RTS TXS trigger frame.

20. A method performed by a shared access point (AP) to share in a transmission opportunity (TXOP) owned by a sharing AP, the method comprising: receiving a control frame from the sharing AP indicating that the sharing AP is sharing the TXOP owned by the sharing AP with the shared AP, wherein the control frame includes a field that indicates a time period of a plurality of time periods allocated for the shared AP within the TXOP; responsive to receiving the control frame, transmitting a response frame to the sharing AP; and initiating a frame exchange sequence within a basic service set (BSS) of the shared AP during the time period.

21. The method of claim 20, further comprising: attempting to access a channel after a second interframe space interval after an end of a network allocation vector (NAV) protection time period for the frame exchange sequence if the shared AP needs to resume transmission within the TXOP, wherein the second interframe space interval is longer than a first interframespace interval used by the sharing AP after the end of the NAV protection time period.

22. The method of claim 21, wherein no attempt to access the channel is made after the second interframe space interval after the end of the NAV protection time period if the shared AP does not need to resume transmission within the TXOP.

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

24. The method of claim 21, wherein the attempt to access the channel is made when a difference between an end of the time period allocated for the shared AP and the end of the NAV protection time period is shorter than or equal to the second interframe space interval.

25. The method of claim 20, further comprising: transmitting a TXOP return frame to the sharing AP after the frame exchange sequence to return the TXOP to the sharing AP before an end of the time period.

26. The method of claim 25, wherein the TXOP return frame is transmitted when a difference between an end of the time period and an end of a network allocation vector (NAV) protection time period for the frame exchange sequence is longer than a point coordination function interframe space (PIFS) interval.

27. The method of claim 20, further comprising: including a TXOP return indication in a frame transmitted during the frame exchange sequence to return the TXOP to the sharing AP before an end of the time period.

28. The method of claim 27, further comprising: receiving a second control frame from the sharing AP after the frame exchange sequence indicating that the sharing AP is reallocating time within the TXOP to the shared AP; responsive to receiving the second control frame, transmitting a second response frame to the sharing AP; and initiating a second frame exchange sequence within the BSS of the shared AP during the reallocated time.

29. The method of claim 20, further comprising: responsive to receiving a request from the sharing AP to provide an explicit TXOP return indication, following an explicit TXOP return approach.

30. The method of claim 20, further comprising: responsive to not receiving a request from the sharing AP to provide an explicit TXOP return indication, following an implicit TXOP return approach.

31. The method of claim 20, wherein the control frame is a multi-user request-to-send TXOP sharing (MU RTS TXS) trigger frame and the response frame is a clear-to-send (CTS) frame.

32. 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 1-19.

33. 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 20-31.

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