Providing information to enable efficient switching of operation modes

Abstract

A method performed by a wireless device to determine how long the wireless device can operate in a different mode. The method includes receiving a physical layer protocol data unit (PPDU) carrying an initial control frame, determining whether contents of the PPDU leading up to an intermediate error detection code field are valid using an error detection code extracted from the intermediate error detection code field, responsive to determining that the contents are valid, switching from operating in a first operation mode to operating in a second operation mode before completely receiving the PPDU, and determining a duration for which the wireless device can operate in the second operation mode based on the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field and the duration of the PPDU.

Description

SPECIFICATIONPROVIDING INFORMATION TO ENABLE EFFICIENT SWITCHING OF OPERATION MODESCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 637,640, filed April 23, 2024, titled “Method of providing information to enable efficient switching of channels and modes”, which is hereby incorporated by reference.TECHNICAL FIELD

[0002] The present disclosure generally relates to wireless communications, and more specifically, relates to determining how long a wireless device can operate in a different mode after mode switching.BACKGROUND

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

[0004] IEEE 802.1 Ibe, also known as “Wi-Fi 7”, is the next generation of the IEEE 802.11 family of standards for wireless local area networks. Currently under development, 802.1 Ibe aims to significantly improve upon the capabilities of its predecessor, 802.1 lax / Wi-Fi 6, by offering even higher data rates, lower latency, and increased reliability. The standard is expected to leverage advanced technologies such as multi-link operation (MLO), which allows devices to simultaneously use multiple frequency bands and channels for enhanced performance andreliability. Additionally, 802. l lbe will introduce 4096-QAM (Quadrature Amplitude Modulation), enabling higher data rates by encoding more bits per symbol. The standard will also feature improved medium access control (MAC) efficiency, enhanced power saving capabilities, and better support for high-density environments. With these advancements, 802.1 Ibe is expected to deliver theoretical maximum data rates of up to 46 gigabits per second (Gbps), making it suitable for bandwidth-intensive applications such as virtual and augmented reality, 8K video streaming, and high-performance gaming.

[0005] A station (STA) may transmit an initial control frame to another STA to reserve a transmission opportunity (TXOP) during which the STAs can communicate with each other without contention from other STAs. The initial control frame may include a duration value indicating the duration of the TXOP. The initial control frame may also include a frame check sequence (FCS) value that the STA that receives the initial control frame can use to verify the integrity of the initial control frame.

[0006] A STA that receives an initial control frame (and is the addressed recipient of the initial control frame) may switch operation modes to operate in a different operation mode during the TXOP reserved by the initial control frame. For example, a STA operating in a low power listen operation mode (in which the STA uses the minimum receiving bandwidth to save power) may switch to operating in a wider bandwidth operation mode (in which the STA uses a wider bandwidth) in response to receiving the initial control frame.

[0007] A STA that overhears an initial control frame (e.g., a STA that is able to receive the initial control frame but is not the addressed recipient of the initial control frame) may decide to perform other tasks during the TXOP reserved by the initial control frame. For example, a STA that overhears an initial control frame may decide to perform non-primary channel access (NPCA) operations during the TXOP. NPCA operations may involve transmitting and / or receiving traffic in the STA’s non-primary channel. The STA may need to switch operation modes to perform the other tasks. For example, if the STA decides to perform NCPA operations during the TXOP, the STA may need to switch from operating in a primary channel access operation mode (in which the STA transmits / receives traffic in the STA’s primary channel) to operating in a NPCA operation mode (in which the STA transmits / receives traffic in the STA’s non-primary channel).

[0008] Mode switching inevitably incurs delays (e.g., due to the hardware-level transitions that need to be made). To mitigate against such delays, an intermediate FCS value can be inserted somewhere in the middle of the initial control frame. A STA that receives such an initial control frame may attempt to verify the integrity of the contents of the initial control frame leading up tothe intermediate FCS value using the intermediate FCS value. If the STA is able to successfully verify the integrity of the contents, the STA may switch operation modes immediately after successfully verifying the integrity of the contents, even before completely decoding the entire initial control frame. That is, the STA may switch operation modes early. The STA may determine the duration for which it can operate in the new operation mode based on a duration value included in the initial control frame indicating the duration of the TXOP. The STA may operate in the new operation mode for the determined duration and then switch back to operating in the original / previous operation mode after the determined duration is over.

[0009] However, when the STA is able to switch operation modes early (e.g., before completely receiving / decoding the entire initial control frame), the duration value included in the initial control frame may not be an accurate reflection of the time that is available to the STA to operate in the new operation mode. The duration value included in the initial control frame indicates the duration of the TXOP starting from the end of the initial control frame. When the STA is able to switch operation modes early (e.g., before completely decoding the initial control frame), as described above, there may be additional time available for the STA to operate in the new operation mode. However, existing mode switching approaches do not take the availability of this additional time into consideration when determining how long the STA can operate in the new operation mode. As a result, existing mode switching approaches do not take advantage of the temporal advantage that is gained by switching operation modes early and thus do not maximize network utilization.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 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.

[0011] 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.

[0012] Figure 2 is a schematic diagram of a wireless device, in accordance with some embodiments of the present disclosure.

[0013] Figure 3A illustrates components of a wireless device configured to transmit data, in accordance with some embodiments of the present disclosure.

[0014] Figure 3B illustrates components of a wireless device configured to receive data, in accordance with some embodiments of the present disclosure.

[0015] Figure 4 illustrates interframe space (IFS) relationships, in accordance with some embodiments of the present disclosure.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] Figure 10 is a diagram showing a wireless network topology in which the mode switching approach described herein can be implemented, according to some embodiments.

[0022] Figure 11 is a diagram showing a non-HT format of a PPDU carrying an initial control frame, according to some embodiments.

[0023] Figure 12 is a diagram showing a format of UHR PPDU that includes a mode switching indicator, according to some embodiments.

[0024] Figure 13 is a diagram showing NPCA operations from the perspective of API, according to some embodiments.

[0025] Figure 14 is a flow diagram of a method for determining how long a wireless device can operate in a different operation mode after mode switching, according to some embodiments.

[0026] Figure 15 is a flow diagram of a method for indicating a non-primary channel access allowed duration, according to some embodiments.DETAILED DESCRIPTION

[0027] The present disclosure generally relates to wireless communications, and more specifically, relates to determining how long a wireless device can operate in a different mode after mode switching.

[0028] As mentioned above, a station (STA) that receives an initial control frame that includes an intermediate frame check sequence (FCS) field may switch operation modes early, before completely decoding the entire frame. By switching operation modes early, there may be additional time available for the STA to operate in the new operation mode. However, existing mode switching approaches do not take the availability of this additional time into consideration when determining how long the STA can operate in the new operation mode. As a result, existing mode switching approaches do not take advantage of the temporal advantage that is gained by switching operation modes early and thus do not maximize network utilization.

[0029] To address this issue, the present disclosure proposes inserting additional information into an initial control frame that allows the STA receiving the initial control frame to more accurately determine how long it can operate in the new operation mode (before it has to switch back to the original / previous operation mode), taking into consideration the additional time that is available for the STA to operate in the new operation mode due to the STA being able to switch operation modes early. For example, information regarding the length or duration from the start of the physical layer protocol data unit (PPDU) carrying the initial control frame to the end of the intermediate FCS field carrying the intermediate FCS value may be inserted into the initial control frame. A STA that overhears such initial control frame may use the inserted information to more accurately determine how long it can operate in the new operation mode. With such a mode switching approach, the STA may be able to stay in the new operation mode for a longer time, making use of additional time that would have otherwise been unused, thereby enhancing network utilization.

[0030] The initial control frame may be carried by a PPDU having a non-HT (non-High Throughput) PPDU format. In such case, the initial control frame may include an intermediate FCS field carrying an intermediate FCS value and a special user information (“user info”) field (that may be referred to herein as a “UHR Length” field) that carries information regarding the length or duration from the start of the PPDU to the end of the intermediate FCS field. The length or duration from the start of the PPDU to the end of the intermediate FCS field may be referred to herein as the UHR PPDU LENGTH. A STA that receives the PPDU may verify the integrity of the contents of the PPDU leading up to the intermediate FCS field using the intermediate FCS value carried by the intermediate FCS field and switch operation modes to anew operation mode immediately after successfully verifying the integrity of the contents. The STA may extract the information from the UHR Length field to determine the length or duration from the start of the PPDU to the end of the intermediate FCS field and use this information when determining how long the STA can operate in the new operation mode after mode switching.

[0031] Alternatively, the initial control frame may be carried by a PPDU having a Ultra High Reliability (UHR) PPDU format. In such case, the PPDU preamble may include a mode switching indicator indicating that mode switching is allowed and a SIG CRC (signal cyclic redundancy check) field carrying a CRC value that can be used to verify the integrity of the PPDU preamble. A STA that receives the PPDU may verify the integrity of the contents of the PPDU preamble using the CRC value carried by the SIG CRC field and switch operation modes to a new operation mode immediately after successfully verifying the integrity of the contents. The STA may use the preamble length or duration when determining how long the STA can operate in the new operation mode after mode switching. The STA may treat the preamble length or duration as being similar to the UHR PPDU LENGTH mentioned above since it indicates the length or duration from the start of the PPDU to the point at which the STA can switch operation modes.

[0032] An example embodiment is a method performed by a wireless device (e.g., implementing a STA or an AP in a wireless network) to determine how long the wireless device can operate in a different mode after mode switching. The method may include receiving a PPDU carrying an initial control frame, extracting an error detection code from an intermediate error detection code field included in the PPDU, determining whether contents of the PPDU leading up to the intermediate error detection code field are valid using the error detection code, responsive to determining that the contents of the PPDU leading up to the intermediate error detection code field are valid, switching from operating in a first operation mode to operating in a second operation mode before completely receiving the PPDU, determining a duration from a start of a preamble of the PPDU to an end of the intermediate error detection code field, determining a duration of the PPDU, determining a duration of a TXOP being reserved by the initial control frame, determining a duration for which the wireless device can operate in the second operation mode based on the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field, the duration of the PPDU, the duration of the TXOP, and a duration of a mode switching delay, operating in the second operation mode for the determined duration, and switching back to operating in the first operation mode after operating in the second operation mode for the determined duration.

[0033] 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.

[0034] 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.

[0035] Figure 1 shows a wireless local area network (WLAN) 100 with a basic service set (BSS) 102 that includes a plurality of wireless devices 104 (sometimes referred to as WLAN devices 104). Each of the wireless devices 104 may include a medium access control (MAC) layer and a physical (PHY) layer according to an IEEE (Institute of Electrical and Electronics Engineers) standard 802.11, including one or more of the amendments(e.g., 802.1 la / b / g / n / p / ac / ax / bd / be). In one embodiment, the MAC layer of a wireless device 104 may initiate transmission of a frame to another wireless device 104 by passing a PHY- TXSTART. request (TXVECTOR) to the PHY layer. The TXVECTOR provides parameters for generating and / or transmitting a corresponding frame. Similarly, a PHY layer of a receiving wireless device may generate an RXVECTOR, which includes parameters of a received frame and is passed to a MAC layer for processing.

[0036] The plurality of wireless devices 104 may include a wireless device 104A that is an access point (sometimes referred to as an AP station or AP STA) and the other wireless devices 104B1-104B4 that are non-AP stations (sometimes referred to as non-AP STAs). Alternatively, all the plurality of wireless devices 104 may be non-AP STAs in an ad-hoc networking environment. In general, the AP STA (e.g., wireless device 104A) and the non-AP STAs (e.g., wireless devices 104B1-104B4) may be collectively referred to as STAs. However, for ease of description, only the non-AP STAs may be referred to as STAs unless the context indicates otherwise. Although shown with four non-AP STAs (e.g., the wireless devices 104B1- 104B4), the WLAN 100 may include any number of non-AP STAs (e.g., one or more wireless devices 104B).

[0037] Figure 2 illustrates a schematic block diagram of a wireless device 104, according to an embodiment. The wireless device 104 may be the wireless device 104A (i.e., the AP of the WLAN 100) or any of the wireless devices 104B1-104B4 in Figure 1. The wireless device 104includes 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.

[0038] 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.

[0039] 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.

[0040] The PHY processor 222 includes a transmitting (TX) signal processing unit (SPU) 224 and a receiving (RX) SPU 226. The PHY processor 222 implements a plurality of functions of the PHY layer. These functions may be performed in software, hardware, or a combination thereof according to an implementation.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The TxSP 324 includes an encoder 300, an interleaver 302, a mapper 304, an inverse Fourier transformer (IFT) 306, and a guard interval (GI) inserter 308.

[0049] 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.

[0050] 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 anencoder 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] The IFT 306 converts a block of the constellation points output from the mapper 304 (or, when MIMO or MU-MIMO is performed, the spatial mapper) to a time domain block (i.e., a symbol) by using an inverse discrete Fourier transform (IDFT) or an inverse fast Fourier transform (IFFT). If the STBC encoder and the spatial mapper are used, the IFT 306 may be provided for each transmit chain.

[0055] 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.

[0056] When the TxSP 324 performs a MIMO or MU-MIMO transmission, some blocks before the spatial mapper may be provided for each user.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] The RxSP 326 includes a GI remover 318, a Fourier transformer (FT) 316, a demapper 314, a deinterleaver 312, and a decoder 310.

[0061] 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.

[0062] 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.

[0063] When the received transmission is the MIMO or MU-MIMO transmission, the RxSP 326 may include a spatial demapper for converting the respective outputs of the FTs 316 of the receiver chains to constellation points of a plurality of space-time streams, and an STBC decoder for despreading the constellation points from the space-time streams into one or more spatial streams.

[0064] 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.

[0065] 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.

[0066] 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 326may further include a stream deparser for combining the streams output from the deinterleavers 312.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] The PHY entity for IEEE 802.11 is based on Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). In either OFDM or OFDMA Physical (PHY) layers, a STA (e.g., a wireless device 104) is capable of transmitting and receiving Physical Layer (PHY) Protocol Data Units (PPDUs) (also referred to as PLCP (Physical Layer Convergence Procedure) Protocol Data Units) that are compliant with the mandatory PHY specifications. A PHY specification defines a set of Modulation and Coding Schemes (MCS) and a maximum number of spatial streams. Some PHY entities define downlink (DL) and uplink (UL) Multi-User (MU) transmissions having a maximum number of space-time streams (STS) per user and employing up to a predetermined total number of STSs. A PHY entity may provide support for 10 Megahertz (MHz), 20 MHz, 40 MHz, 80 MHz, 160 MHz, 240 MHz, and 320 MHz contiguous channel widths and support for an 80+80, 80+160 MHz, and 160+160 MHz non-contiguous channel width. Each channel includes a plurality of subcarriers, which may also be referred to as tones. A PHY entity may define signaling fields denoted as Legacy Signal (L-SIG), Signal A (SIG-A), and Signal B (SIG-B), and the like within a PPDU by which some necessary information about PHY Service Data Unit (PSDU) attributes are communicated. The descriptions below, for sake of completeness and brevity, refer to OFDM-based 802.11 technology. Unless otherwise indicated, a station refers to a non-AP STA.

[0071] 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 fortransmission 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] After determining that the channel is not used by other devices (that is, that the channel is IDLE) during a DIFS (and performing backoff if required), the station STA1 may transmit a Request-To-Send (RTS) frame to the station STA2. Upon receiving the RTS frame, after a SIFS the station STA2 may transmit a Clear-To-Send (CTS) frame as a response to the RTS frame. If Dual-CTS is enabled and the station STA2 is an AP, the AP may send two CTS frames in response to the RTS frame (e.g., a first CTS frame in a non-High Throughput format and a second CTS frame in the HT format).

[0082] 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.

[0083] 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 framehas 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.

[0084] 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.

[0085] 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.

[0086] The IEEE 802.1 Ibn (Ultra High Reliability, UHR) working group has been established to address the growing demand for higher peak throughput and reliability in Wi-Fi. As shown in Figure 6, the peak PHY rate has significantly increased from IEEE 802.1 lb to IEEE 802.1 Ibe (Wi-Fi 7), with the latter focusing on further improving peak throughput. The UHR study group aims to enhance the tail of the latency distribution and jitter to support applications that require low latency, such as video-over- WLAN, gaming, AR, and VR. It is noted that various characteristics of UHR (e.g., max PHY rate, PHY rate enhancement, bandwidth / number of spatial streams, and operating bands) are still to be determined.

[0087] 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.

[0088] 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 lowlatency 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] The Extremely High Throughput (EHT) PPDU frame encompasses several components. It includes a legacy part, which comprises fields such as the Legacy Short Training Field (L-STF), Legacy Long Training Field (L-LTF), Legacy Signal Field (L-SIG), and Repeated Legacy Signal Field (RL-SIG). These fields are used to maintain compatibility with older Wi-Fi standards.

[0093] 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.

[0094] Figure 7 provides a more detailed description of each field in the EHT PPDU frame, including their purposes and characteristics.

[0095] 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.

[0096] 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, incertain 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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).

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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 decodethe 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.

[0108] In a second type of HARQ scheme, also referred to as an incremental redundancy (IR) HARQ (IR-HARQ) scheme, different puncturing patterns are used for each subpacket such that the signal changes for each retransmitted subpacket in comparison to the originally transmitted subpacket. IR-HARQ alternatively uses two puncturing patterns for odd numbered and even numbered transmissions, respectively. The redundancy scheme of IR-HARQ improves the log likelihood ratio (LLR) of parity bit(s) in order to combine information sent across different transmissions due to requests and lowers the code rate as the additional subpacket is used. This results in a lower error rate of the subpacket in comparison to CC-HARQ. The puncturing pattern used in IR-HARQ is indicated by a subpacket identity (SPID) indication. The SPID of the first subpacket may always be set to 0 and all the systematic bits and the punctured parity bits are transmitted in the first subpacket. Self-decoding is possible when the receiving signal- to-noise ratio (SNR) environment is good (i.e., a high SNR). In some embodiments, subpackets with corresponding SPIDs to be transmitted are in increasing order of SPID but can be exchanged / switched except for the first SPID.

[0109] AP coordination has been considered as a potential technology to improve WLAN system throughput in the IEEE 802.1 Ibe standard and is still being discussed in the IEEE 802.1 Ibn (UHR) standard. To support various AP coordination schemes, such as coordinated beamforming, OFDMA, TDMA, spatial reuse, and joint transmission, a predefined mechanism for APs is necessary.

[0110] 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.

[0111] The operation of various AP coordination schemes has been discussed in the IEEE 802.1 Ibe and UHR standards:

[0112] 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.

[0113] Coordinated OFDMA (C-OFDMA): APs transmit on orthogonal frequency resources by coordinating and splitting the spectrum, enabling more efficient spectrum utilization.

[0114] Joint Transmission (JTX): Multiple APs transmit jointly to a given user simultaneously by sharing data between the APs.

[0115] Coordinated Spatial Reuse (C-SR): Multiple APs or STAs adjust their transmit power to reduce interference between APs.

[0116] By implementing these AP coordination schemes, WLAN systems can improve their overall throughput and efficiency by leveraging the cooperation between multiple APs.

[0117] Figure 10 is a diagram showing a wireless network topology in which the mode switching approach described herein can be implemented, according to some embodiments.

[0118] As shown in the diagram, the wireless network includes a first AP (“API”) that operates a first basic service set (“BSS1”), a first STA (“STA1-1”) that belongs to BSS1, and a second STA (“STA1-2”) that belongs to BSS1. The wireless network further includes a second AP (“AP2”) that operates a second basic service set (“BSS2”), a third STA (“STA2-1”) that belongs to BSS2, and a fourth STA (“STA2-2”) that belongs to BSS2. BSS2 is an OBSS from the perspective of BSS1. It is assumed that API, STA1-1, and STA1-2 are within the transmission range of AP2.

[0119] In this example, it is assumed that AP2 may transmit a MU-RTS frame to its associated STAs (STA2-1 and STA2-2) to reserve a TXOP for frame exchange in BSS2. Also, it is assumed that API, STA1-1, and STA1-2 can overhear the MU-RTS frame and switch operation modes in response to overhearing the MU-RTS frame to perform other tasks during the TXOP. BSS1 is the target BSS in this example in that it is the BSS that includes the AP / STAs that can perform switch operation modes and perform other tasks. For example, API may perform NPCA operations, dynamic subband operation (DSO) operations, or in-device coexistence (IDC) operations during the TXOP. NPCA is a technology that allows a wireless device to transmit data in a non-primary channel when the primary channel is busy. DSO is a technology that allows a wireless device to be dynamically allocated frequency resources outside of its current operating bandwidth. IDC is a technology that allows a wireless device that is equipped with an additional type of wireless communication technology (in addition toWi-Fi) such as Bluetooth to transmit data using the additional wireless communication technology when Wi-Fi is not being used. API may need to switch operation modes to perform the other tasks. For example, to perform NPCA operations, API may need to switch operation modes from a primary channel access operation mode (in which API transmits data in the primary channel) to a NPCA operation mode (in which API transmits data in a non-primary channel). As another example, to perform DSO operations, API may need to switch operation modes from a first operation mode to a second operation mode, where API uses different subbands in the first operation mode and the second operation mode. As another example, to perform IDC operations, API may need to switch operation modes from a Wi-Fi operation mode to a IDC operation mode (e.g., in which API suspends Wi-Fi operations and performs Bluetooth operations)

[0120] In this context, the MU-RTS frame is an example of an initial control frame. An initial control frame may be any type of control frame that is used for initiating and / or controlling communications. For example, the initial control frame may be a trigger frame such as a MU-RTS frame or buffer status report poll (BSRP) frame. A trigger frame may include special user info fields with special association ID (AID) field values to convey new / additional information to STAs that recognize the special AID field values (e.g., UHR STAs).

[0121] An initial control frame may be used for waking up a STA that is operating in a low power listen (LPL) operation mode (e.g., in which the STA only activates / uses the minimum receiving bandwidth (e.g., 20 MHz bandwidth)) to cause the STA to operate in a wide bandwidth operation mode (e.g., in which the STA uses a 80 MHz bandwidth). In such case, the initial control frame may include various information such as information regarding the width of the wider bandwidth, the modulation coding scheme (MCS), and / or the number of spatial streams (Nss).

[0122] For purposes of explanation only, various embodiments will be described in a context where API performs NPCA operations during the TXOP. It should be appreciated, however, that the mode switching approach described herein can be used with other technologies such as DSO, IDC, and LPL. Also, for purposes of explanation only, various embodiments will be described in the context of the wireless network topology shown in Figure 10. It should be appreciated, however, that the mode switching approach described herein can be applied in wireless networks having different topologies from the particular topology shown in the diagram to gain similar benefits.

[0123] Figure 11 is a diagram showing a non-HT format of a PPDU carrying an initial control frame, according to some embodiments.

[0124] As shown in the diagram, the PPDU includes a preamble 1102, a frame control field 1104, a duration field 1106, a receiver address (RA) field 1108, a transmitter address (TA) field 1110, a common information field 1112, a special user info field 1114 (also referred to herein as the “UHR Length” field), a user info list field 1116, an intermediate FCS field 1118, a user info field 1120, a user info field 1122, a padding field 1124, and a FCS field 1126. The fields that appear after the preamble 1102 may form an initial control frame. User info field 1120 and user info field 1122 may be interpreted / understood by legacy wireless devices (e.g., up to IEEE 802.1 IbeZEHT). User info field 1114 (UHR Length field) may be interpreted / understood by newer wireless devices (e.g., IEEE 802.1 Ibn / UHR) that support the technique described herein. The user info list field 1116 may be a concatenation of user info fields and may be interpreted / understood by legacy wireless devices and newer wireless devices.

[0125] A legacy STA that does not support / understand the UHR Length field 1114 may decode the entire PPDU and verify the integrity of the contents of the PPDU using the FCS value included in the FCS field 1126 (that appears at the end of the PPDU).

[0126] A STA (which could be a AP STA (e.g., API) or a non-AP STA) that supports / understands the intermediate FCS field 1118 (e.g., a UHR STA) may decode the contents of the PPDU leading up to the intermediate FCS field 1118 and verify the integrity of the contents using the intermediate FCS value carried by the intermediate FCS field 1118. If the STA is able to successfully verify the integrity of the contents of the PPDU leading up to the intermediate FCS field 1118 (i.e., the contents are valid), the STA may switch operation modes to the NPCA operation mode immediately after verifying the integrity of the contents, even before completely decoding the entire PPDU (the STA may switch operation modes early).

[0127] The STA that receives the PPDU may determine the duration of the TXOP being reserved by the initial control frame based on the duration value included in the duration field 1106. The duration value carried by the duration field 1106 may indicate the duration of the TXOP being reserved by the initial control frame carried by the PPDU starting from the end of the PPDU. With existing mode switching approaches, the STA may also determine the duration for which it can operate in the NPCA operation mode based on this duration value. The duration value may accurately reflect the amount of time that the STA has to operate in the NPCA operation mode (before it has to switch back to operating in the primary channel access operation mode) if the STA switches operation modes after decoding the entire PPDU.However, if the STA is able to switch operation modes early (before decoding the entire PPDU), then the duration value may not be an accurate reflection of the amount of time that that the STA has available to operate in the NPCA operation mode because it does not take into considerationthe additional time that is available due to the STA being able to switch operation modes early. Thus, with existing mode switching approaches, when the STA is able to switch operation modes early, the calculated NPCA allowed duration may be shorter than the amount of time that is actually available. As a result, the additional time gained by switching operation modes early is not efficiently utilized.

[0128] In an embodiment, additional information is inserted into the initial control frame to allow the STA receiving the initial control frame to more accurately determine how long it can operate in the NPCA operation mode. For example, the UHR Length field 1114 may be inserted in the initial control frame to carry a value indicating the length (e.g., in bytes) or duration from the start of the PPDU preamble 1102 to the end of the intermediate FCS field 1118 (this length is labeled as “UHR PPDU LENGTH” in the diagram, whereas the length of the entire PPDU is labeled as “PPDU LENGTH”). As will be described in additional detail herein, a STA receiving the initial control frame may determine the duration for which the STA can operate in the NPCA operation mode using such value. The duration may be determined in a manner that takes into consideration the additional time that the STA has available to operate in the NPCA operation mode due to the STA switching operation modes early. In the example shown in the diagram, the UHR Length field 1114 is placed immediately after the common information field 1112 but it should be appreciated that the UHR Length field 1114 could be placed elsewhere within the initial control frame.

[0129] Figure 12 is a diagram showing a format of UHR PPDU that includes a mode switching indicator, according to some embodiments.

[0130] As shown in the diagram, the PPDU includes a preamble that includes a STF field 1202, a LTF field 1204, a U-SIG field 1206, and a SIG CRC field 1212. The preamble may include other fields not shown in the diagram. The PPDU also includes a MAC protocol data unit (MPDU) 1214.

[0131] The U-SIG field 1206 may include a mode switching indicator 1210 indicating that the receiving STA is allowed to switch operation modes. When a STA receives such a PPDU and detects the mode switching indicator 1210, the STA may switch operation modes to the NPCA operation mode immediately after decoding the SIG CRC field 1212 (assuming that the STA is able to successfully verify the contents of the PPDU leading up to the SIG CRC field 1212 using the CRC value carried by the SIG CRC field 1212). Thus, the STA may be able to switch operation modes early, even before completely decoding the entire PPDU.

[0132] As will be described in additional detail herein, a STA receiving the PPDU may determine the duration for which the STA can operate in the NPCA mode using the preamblelength. The duration may be determined in a manner that takes into consideration the additional time that is available to operate in the NPCA operation mode due to the STA switching operation modes early. The STA may treat the preamble length as being similar to the UHR PPDU LENGTH mentioned above in that it indicates the length from the start of the PPDU to the point at which the STA can switch operation modes (early).

[0133] Also, the STA receiving the PPDU may determine whether it is an OBSS STA or an in-BSS STA based on the value carried by the BSS color field (not shown) included in the U- SIG field 1206. Thus, the STA may be able to determine whether it can perform NPCA operations even before interpreting the complete preamble. Therefore, there is no hindrance to the STA switching operation modes early to perform NPCA operations.

[0134] Figure 13 is a diagram showing NPCA operations from the perspective of API, according to some embodiments.

[0135] In the example shown in the diagram, API may initially operate in a primary channel access operation mode in which API transmits data in a primary 40 MHz channel that is composed of a primary 20 MHz channel (P20) and a secondary (non-primary) 20 MHz channel (S20). At time tO, API may receive a MU-RTS frame 1305 transmitted by AP2 that includes an intermediate FCS field. In this example, the MU-RTS frame 1305 functions as an initial control frame. The MU-RTS frame 1305 may have been transmitted by AP2 to reserve a TXOP in BSS2. STAs that belong to BSS2 may transmit a CTS frame 1310 to AP2 (as a response to the MU-RTS frame 1305) in the primary 40 MHz channel. AP2 and the STAs that belong to BSS2 may then perform OBSS frame exchange 1330 and OBSS frame exchange 1335 in the primary 40 MHz channel during the TXOP.

[0136] Between time tO and time tl, API may decode the UHR Length field included in the MU-RTS frame 1305. At time tl, API may verify the integrity of the contents of the MU-RTS frame 1305 leading up to the intermediate FCS field using the intermediate FCS value carried by the intermediate FCS field. If API is able to successfully verify the integrity of the contents, API may attempt to switch operation modes from the primary channel access operation mode (in which API uses the primary 40 MHz channel) to a NPCA operation mode (in which API uses a non-primary 40 MHz channel). In this example, it is assumed that API is able to successfully verify the integrity of the contents of the MU-RTS frame 1305 leading up to the intermediate FCS field so API may switch operation modes to the NCPA operation mode in which API uses the non-primary 40 MHz channel. The non-primary 40 MHz channel may include an auxiliary 20 MHz channel (A20). Due to hardware constraints, there may be a mode switching delay before API is able to operate in the NPCA operation mode. API may completemode switching at time t3. After completing mode switching, there may be an additional delay for synchronization in the auxiliary channel (A20). There may OBSS signals 1315 in the nonprimary 40 MHz channel. At time t4, API may perform an enhanced distributed channel access (EDC A) backoff procedure in the non-primary 40 MHz channel and then transmit a downlink PPDU 1320 to an associated STA (e.g., STA1-1) in the non-primary 40 MHz channel. API may then receive ACK frames 1325 in the non-primary 40 MHz channel. The TXOP ends at time t6 so API may need to switch back to operating in the primary channel access operation mode before time t6. As such, API and its associated STAs (e.g., STA1-1 and STA1-2) that belong to BSS1 may switch back to operating in the primary channel access operation mode in advance of time t6 (e.g., at time t5), taking into consideration the mode switching delay to switch back to the primary channel access operation mode. Unaddressed STAs (e.g., STAs belonging to BSS1 that did not participate in the NPCA frame exchange in the non-primary 40 MHz channel) may anticipate the frame exchange sequence and proactively switch back to operating in the primary 40 MHz channel.

[0137] Starting at time t6, API may operate in the primary channel access mode again. For example, after a synchronization delay that ends at time t7, API may transmit request-to-send (RTS) frame 1340, transmit CTS frame 1345, and receive a 40 MHz PPDU 1350 in the primary 40 MHz channel.

[0138] With the availability of the UHR PPDU LENGTH information in the MU-RTS frame 1305, API may determine the duration for which it can operate in the NPCA operation mode (the permitted time on the actual / exact air interface) based on the following two factors:

[0139] 1) The duration of the TXOP being reserved by the MU-RTS frame 1305 (e.g., the duration from time t2 to time t6 in the example shown in the diagram). This duration may be determined based on the duration value included in the duration field included in the MAC header of the MU-RTS frame 1305 or similar field.

[0140] 2) The duration from the end of the intermediate FCS field to the end of the PPDU carrying the MU-RTS frame 1305 (e.g., the duration from time tl to time t2 in the example shown in the diagram). This duration may be determined based on subtracting theUHR PPDU LENGTH from the length of the entire PPDU. The UHR PPDU LENGTH may be extracted from the UHR Length field. The duration of the entire PPDU may be determined based on the value included in the L LENGTH field included in the SIG field of the preamble.

[0141] More specifically, the duration for which API can operate in the NPCA mode can be determined based on the duration of the TXOP being reserved by the MU-RTS frame 1305, the duration from the end of the intermediate FCS field to the end of the PPDU carrying the MU-RTS frame 1305, the duration of the entire PPDU carrying the MU-RTS frame 1305, and the duration of the mode switching delay (e.g., the time it takes to switch operation modes from the primary channel access operation mode to the NPCA operation mode and vice versa).

[0142] For example, the duration for which API can operate in the NPCA mode may be determined according to the following equation:NPCA allowed duration = OBSS TXOP DURATION + (t2-tl) - (2 * Switching delay) Equation I

[0143] In Equation I above, “NPCA allowed duration" is the duration for which API can operate in the NPCA operation mode, “OBSS TXOP DURATION' is the duration of the OBSS TXOP ( the TXOP being reserved by the MU-RTS frame 1305), t2 is the time at which the PPDU carrying the MU-RTS frame 1305 ends, tl is the time at which the intermediate FCS field included in the MU-RTS frame 1305 ends, and “Switching delay" is the duration of the mode switching delay. In Equation I, it is assumed that the mode switching delay for switching operation modes from the primary channel access operation mode to the NPCA operation mode and the mode switching delay for switching operation modes from the NPCA operation mode to the primary channel access mode are the same. However, it should be appreciated that these mode switching delays could be different and that Equation I can be modified to reflect this.

[0144] In practice, the duration “t2-tl” could be longer than the duration of the mode switching delay. For example, this may be the case if there is a significant amount of content that comes after the intermediate FCS field to provide various functionality such as padding, providing additional information related to the initial control frame, and / or providing information to legacy STAs.

[0145] By explicitly providing information regarding the length or duration from the start of the preamble of the PPDU to the end of the intermediate FCS field included in the initial control frame (e.g., MU-RTS frame 1305), a STA receiving the initial control frame can determine how long the STA can operate in a different operation mode (e.g., NPCA operation mode), taking into consideration the additional time that is available for the STA to operate in the different operation mode due to the STA switching operation modes early. This may allow the STA to operate in the different operation mode for a longer period of time. This may reduce the overhead incurred during mode switching and enable more efficient utilization of the available time. When using the non-HT PPDU format, it is inevitable to be influenced by the processing time at the MAC layer. Considering the MAC processing delay, mode switching delay, and even the need for performing EDCA backoff, significant delay / overhead is expected whenswitching operation modes. The mode switching approach described herein allows for using the available time in a more efficient manner.

[0146] Examples have mostly been described for the case where the PPDU carrying the initial control frame has a non-HT PPDU format (e.g., the format shown in Figure 11). However, the approach described herein for determining how long a STA can operate in a different operation mode can also be implemented using other PPDU formats such as the UHR PPDU format shown in Figure 12. For example, a STA receiving a PPDU having the UHR PPDU format may switch operation modes immediately after successfully verifying the contents of the PPDU preamble using the CRC value included in the SIG CRC field (e.g., SIG CRC field 1212 in Figure 12). The STA may determine the duration for which the STA can operate in the new operation mode based on the duration of the TXOP being reserved by the initial control frame, the duration of the entire preamble, the duration of the entire PPDU, and the duration of the mode switching delay.

[0147] More generally, the duration for which a STA can operate in a different mode may be determined according to the following equation: allowed duration = TXOP duration + (x - y) - (2 * switching delay) Equation 2

[0148] In Equation 2, allowed duration is the duration for which the wireless device can operate in the different mode, TXOP duration is the duration of the TXOP, x is the duration of the PPDU, y is the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field, and switching delay is the duration of the mode switching delay. When the PPDU has a non-HT PPDU format, the intermediate FCS field may be the intermediate error detection code field. When the PPDU has a UHR PPDU format, the SIG CRC may be the intermediate error detection code field.

[0149] Embodiments have been described primarily in the context where the STA receiving the initial control frame is not the addressed recipient of the initial control frame (i.e., the STA overhears the initial control frame) and can operate in a different operation mode (e.g., NPCA operation mode) during the TXOP reserved by the initial control frame. However, in some embodiments, the STA that is the intended recipient of the initial control frame can perform similar operations to more accurately determine how long it can operate in a different mode.

[0150] For example, to save power, a STA may normally operate in a LPL operation mode in which the STA only activates the minimal components needed to receive PPDUs using the minimum receiving bandwidth (e.g., 20 MHz bandwidth). When the STA receives an initial control frame for waking up the STA, the STA may switch from operating in the low powerlisten operation mode to operating in a wider bandwidth operation mode and transmit / receive data using a wider bandwidth (e.g., 80 MHz bandwidth) during the TXOP. When the TXOP is over, the STA may switch back to operating in the low power listen operation mode to save power. If the STA is able to switch operation modes early (e.g., before completely receiving the initial control frame), the STA may use the approach described herein to determine how long it can operate in the wider bandwidth operation mode in a manner that takes into consideration the additional time that is available due to the STA switching operation modes early.

[0151] In an embodiment, the STA (e.g., AP STA or non-AP STA) that transmits the initial control frame determines the duration for which other STAs can operate in a different operation mode using the approach described herein (e.g., using Equation 2) and inserts an indication of the determined duration in the initial control frame before transmitting the initial control frame. The determined duration may be inserted into a MPDU included in the PPDU carrying the initial control frame or a signal field included in a preamble of the PPDU. The STA may transmit the initial control frame while the STA is operating in the original operation mode or the different operation mode. Transmitting such an initial control frame while operating in the different operation mode may be useful to synchronize the durations (e.g., NPCA allowed duration) for other STAs. For example, considering the wireless network topology shown in Figure 10, API, STA1-1, and STA1-2 may switch operation modes to the NPCA operation mode in response overhearing a MU-RTS frame transmitted by AP2. API, STA1-1, and STA1-2 may each determine the NPCA allowed duration using the approach described herein. However, the NPCA allowed durations determined by the different AP / STAs may not be aligned due to certain factors. If API is able to transmit and advertise its determined NPCA allowed duration, the associated STAs operating in the NPCA operation mode can know when API will switch back to the primary channel access operation mode (switch back to using the primary channel). With this information, the associated STAs may be able to switch back to the primary channel access operation mode almost simultaneously.

[0152] As another example, suppose there is another STA that belongs to B SSI (“STA1-3”) that switches to operating in the NPCA operation mode after overhearing a frame transmitted by an arbitrary AP (“AP3”). In this case, STA1-3 may determine a NPCA allowed duration that is different from the NPCA allowed duration determined by API, STA1-1, and STA1-2. Thus, it may be beneficial for API to announce the NPCA allowed duration it will be using to its associated STAs to achieve synchronization. Thus, the ability to transmit this duration information while operating in the NPCA operation mode may be useful.

[0153] Turning now to Figure 14, a method 1400 will be described for determining how long a wireless device can operate in a different operation mode after mode switching, in accordance with an example embodiment. The method 1400 may be performed by a wireless device (e.g., wireless device 104).

[0154] Additionally, although shown in a particular order, in some embodiments the operations of the method 1400 (and the other methods shown in the other figures) may be performed in a different order. For example, although the operations of the method 1400 are shown in a sequential order, some of the operations may be performed in partially or entirely overlapping time periods.

[0155] At operation 1405, the wireless device receives a PPDU carrying an initial control frame. In an embodiment, the initial control frame is a MU-RTS frame. In an embodiment, the initial control frame is a BSRP frame.

[0156] At operation 1410, the wireless device extracts an error detection code from an intermediate error detection code field included in the PPDU.

[0157] At operation 1415, the wireless device determines whether contents of the PPDU leading up to the intermediate error detection code field are valid using the error detection code.

[0158] At operation 1420, responsive to determining that the contents of the PPDU leading up to the intermediate error detection code field are valid, the wireless device switches from operating in a first operation mode to operating in a second operation mode before completely receiving the PPDU. In an embodiment, the first operation mode is a Wi-Fi operation mode and the second operation mode is an in-device coexistence operation mode. In an embodiment, the first operation mode is a low power listening mode and the second operation mode is a full capability operation mode. In an embodiment, STA uses different subbands in the first operation mode and the second operation mode (e.g., as part of performing DSO operations). In an embodiment, the first operation mode is a primary channel access operation mode and the second operation mode is a non-primary channel access operation mode.

[0159] At operation 1425, the wireless device determines a duration from a start of a preamble of the PPDU to an end of the intermediate error detection code field.

[0160] At operation 1430, the wireless device determines a duration of the PPDU.

[0161] At operation 1435, the wireless device determines a duration of a TXOP being reserved by the initial control frame.

[0162] At operation 1440, the wireless device determines a duration for which the wireless device can operate in the second operation mode based on the duration from the start of thepreamble of the PPDU to the end of the intermediate error detection code field, the duration of the PPDU, the duration of the TXOP, and a duration of a mode switching delay.

[0163] In an embodiment, the duration for which the wireless device can operate in the second operation mode is determined according to the following equation: allowed duration = TXOP duration + (x - y) - (2 * switching delay), wherein allowed duration is the duration for which the wireless device can operate in the second operation mode, TXOP duration is the duration of the TXOP, x is the duration of the PPDU, y is the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field, and switching delay is the duration of the mode switching delay.

[0164] At operation 1445, the wireless device operates in the second operation mode for the determined duration.

[0165] At operation 1450, the wireless device switches back to operating in the first operation mode after operating in the second operation mode for the determined duration.

[0166] In an embodiment, the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field is determined based on a first value extracted from a first field included in the PPDU, the duration of the PPDU is determined based on a second value extracted from a second field included in the PPDU, and the duration of the TXOP is determined based on a third value extracted from a third field included in the PPDU. In an embodiment, the first field is a user information field included in the initial control frame, the second field is a legacy signal field included in the preamble of the PPDU, the third field is a duration field included in the initial control frame, and the intermediate error detection code field is an intermediate frame check sequence field included in the initial control frame. In an embodiment, the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field is a duration of the preamble of the PPDU and the intermediate error detection code field is a signal cyclic redundancy check (SIG CRC) field included in the preamble of the PPDU.

[0167] Turning now to Figure 15, a method 1500 will be described for indicating a nonprimary channel access allowed duration, in accordance with an example embodiment. The method 1500 may be performed by a wireless device (e.g., wireless device 104).

[0168] At operation 1505, the wireless device generates a PPDU carrying an initial control frame, wherein the PPDU includes an intermediate error detection code field carrying an error detection code for contents of the PPDU leading up to the error detection code field, wherein the initial control frame includes an indication of a duration of a TXOP being reserved by the initialcontrol frame. In an embodiment, the initial control frame is a MU-RTS frame. In an embodiment, the initial control frame is a BSRP frame.

[0169] At operation 1510, the wireless device determines the NPCA allowed duration based on a duration from a start of a preamble of the PPDU to an end of the intermediate error detection code field, a duration of the PPDU, the duration of the TXOP, and a duration of a mode switching delay.

[0170] In an embodiment, the NPCA allowed duration is determined according to the following equation: allowed duration = TXOP duration + (x - y) - (2 * switching delay), wherein allowed duration is the NPCA allowed duration, TXOP duration is the duration of the TXOP, x is the duration of the PPDU, y is the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field, and switching delay is the duration of the mode switching delay.

[0171] At operation 1515, the wireless device inserts an indication of the NPCA allowed duration in the PPDU. In an embodiment, the indication of the NPCA allowed duration is included in a MPDU included in the PPDU. In an embodiment, the indication of the NPCA allowed duration is included in a signal field included in the preamble of the PPDU.

[0172] At operation 1520, the wireless device transmits the PPDU. In an embodiment, the PPDU is transmitted while the wireless device is operating in a NPCA operation mode.

[0173] 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.

[0174] 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, asdescribed herein, an apparatus may include a memory unit, which stores instructions that may be executed by a hardware processor installed in the apparatus. The apparatus may also include one or more other hardware or software elements, including a network interface, a display device, etc.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems can be used withprograms in accordance with the teachings herein, or it can prove convenient to construct a more specialized apparatus to perform the method. The structure for a variety of these systems will appear as set forth in the description below. In addition, the present disclosure is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages can be used to implement the teachings of the disclosure as described herein.

[0179] 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.

[0180] 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 wireless device to determine how long the wireless device can operate in a different operation mode after mode switching, the method comprising: receiving a physical layer protocol data unit (PPDU) carrying an initial control frame; extracting an error detection code from an intermediate error detection code field included in the PPDU; determining whether contents of the PPDU leading up to the intermediate error detection code field are valid using the error detection code; responsive to determining that the contents of the PPDU leading up to the intermediate error detection code field are valid, switching from operating in a first operation mode to operating in a second operation mode before completely receiving the PPDU; determining a duration from a start of a preamble of the PPDU to an end of the intermediate error detection code field; determining a duration of the PPDU; determining a duration of a transmission opportunity (TXOP) being reserved by the initial control frame; determining a duration for which the wireless device can operate in the second operation mode based on the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field, the duration of the PPDU, the duration of the TXOP, and a duration of a mode switching delay; operating in the second operation mode for the determined duration; and switching back to operating in the first operation mode after operating in the second operation mode for the determined duration.

2. The method of claim 1, wherein the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field is determined based on a first value extracted from a first field included in the PPDU, the duration of the PPDU is determined based on a second value extracted from a second field included in the PPDU, and the duration of the TXOP is determined based on a third value extracted from a third field included in the PPDU.

3. The method of claim 2, wherein the first field is a user information field included in the initial control frame, the second field is a legacy signal field included in the preamble of thePPDU, the third field is a duration field included in the initial control frame, and the intermediate error detection code field is an intermediate frame check sequence field included in the initial control frame.

4. The method of claim 1, wherein the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field is a duration of the preamble of the PPDU and the intermediate error detection code field is a signal cyclic redundancy check (SIG CRC) field included in the preamble of the PPDU.

5. The method of claim 1, wherein the first operation mode is a Wi-Fi operation mode and the second operation mode is an in-device coexistence operation mode.

6. The method of claim 1, wherein the first operation mode is a low power listening mode and the second operation mode is a full capability operation mode.

7. The method of claim 1, wherein the STA uses different subbands in the first operation mode and the second operation mode .

8. The method of claim 1, wherein the first operation mode is a primary channel access operation mode and the second operation mode is a non-primary channel access operation mode.

9. The method of claim 1, wherein the duration for which the wireless device can operate in the second operation mode is determined according to the following equation: allowed duration = TXOP duration + (x - y) - (2 * switching delay), wherein allowed duration is the duration for which the wireless device can operate in the second operation mode, TXOP duration is the duration of the TXOP, x is the duration of the PPDU, y is the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field, and switching delay is the duration of the mode switching delay.

10. The method of claim 1, wherein the initial control frame is a multi-user request-to-send (MU-RTS) frame.

11. The method of claim 1, wherein the initial control frame is a buffer status report poll (BSRP) frame.

12. A method performed by a wireless device to indicate a non-primary channel access (NPCA) allowed duration, the method comprising: generating a physical layer protocol data unit (PPDU) carrying an initial control frame, wherein the PPDU includes an intermediate error detection code field carrying an error detection code for contents of the PPDU leading up to the error detection code field, wherein the initial control frame includes an indication of a duration of a transmission opportunity (TXOP) being reserved by the initial control frame; determining the NPCA allowed duration based on a duration from a start of a preamble of the PPDU to an end of the intermediate error detection code field, a duration of the PPDU, the duration of the TXOP, and a duration of a mode switching delay; inserting an indication of the NPCA allowed duration in the PPDU; and transmitting the PPDU.

13. The method of claim 12, wherein the indication of the NPCA allowed duration is included in a media access control protocol data unit (MPDU) included in the PPDU.

14. The method of claim 12, wherein the indication of the NPCA allowed duration is included in a signal field included in the preamble of the PPDU.

15. The method of claim 12, wherein the initial control frame is a multi-user request-to-send (MU-RTS) frame.

16. The method of claim 12, wherein the initial control frame is a buffer status report poll (BSRP) frame.

17. The method of claim 12, wherein the NPCA allowed duration is determined according to the following equation: allowed duration = TXOP duration + (x - y) - (2 * switching delay), wherein allowed duration is the NPCA allowed duration, TXOP duration is the duration of the TXOP, x is the duration of the PPDU, y is the duration from the start of the preamble of the PPDU to the end of the intermediate error detection code field, and switching delay is the duration of the mode switching delay.

18. The method of claim 12, wherein the PPDU is transmitted while the wireless device is operating in a NPCA operation mode.

19. A 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 wireless device to perform the method of any one of claims 1-11.

20. A 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 wireless device to perform the method of any one of claims 12-18.

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