Patent Description:
A wireless local area network (WLAN) may be formed by one or more access points (APs) that provide a shared wireless communication medium for use by a number of client devices also referred to as stations (STAs). The basic building block of a WLAN conforming to the Institute of Electrical and Electronics Engineers (IEEE) <NUM> family of standards is a Basic Service Set (BSS), which is managed by an AP. Each BSS is identified by a Basic Service Set Identifier (BSSID) that is advertised by the AP. An AP periodically broadcasts beacon frames to enable any STAs within wireless range of the AP to establish or maintain a communication link with the WLAN.

Some traffic, such as gaming traffic, has strict end-to-end latency and packet loss requirements, and may be classified as low-latency or latency sensitive traffic. It is desirable for WLANs to recognize latency sensitive traffic, and to ensure that latency sensitive traffic can be handled without violating any associated latency, packet loss, or data throughput requirements.

Document IEEE <NUM>-<NUM>/0353r2 discusses MU-RTS/CTS for TWT protection. Document <CIT> relates to triggered target wake time operation. Document IEEE <NUM>-<NUM>/1045r3 discusses prioritized EDCA channel access.

The systems, methods, and devices of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

One innovative aspect of the subject matter described in this disclosure can be implemented as a method for wireless communications. In some implementations, the method may be performed by a wireless communication device operating as an access point (AP), and may include establishing a restricted target wake time (TWT) session on a wireless medium for one or more wireless stations (STAs) associated with latency sensitive traffic. The restricted TWT session may include one or more restricted TWT service periods (SPs) for communications on the wireless medium with only the one or more STAs associated with the latency sensitive traffic. The method may include transmitting a clear-to-send (CTS) frame on the wireless medium at a start of each restricted TWT SP of the one or more restricted TWT SPs. The CTS frame may indicate to other STAs that the wireless medium is busy or unavailable for a duration of the respective restricted TWT SP. The method may include transmitting latency sensitive data to or receiving latency sensitive data from the one or more STAs during at least one restricted TWT SP of the one or more restricted TWT SPs. In some implementations, a receiver address (RA) of the CTS frame may be set to a configured medium access control (MAC) address indicating that STAs belonging to the restricted TWT session are permitted to access the wireless medium during the respective restricted TWT SP. In some instances, the configured MAC address may correspond to a configured network allocation vector (NAV) setting for the other STAs.

In some implementations, the method may also include indicating that each of the other STAs is to terminate a transmit opportunity (TXOP) on the wireless medium at or before the start of each restricted TWT SP of the one or more restricted TWT SPs. In some other implementations, the method may also include indicating that each of the other STAs is not permitted to access the wireless medium during each restricted TWT SP of the one or more restricted TWT SPs. In some instances, the indications may be included in a TWT Parameter Information field of a TWT element carried in one or more beacon frames transmitted from the AP.

In some implementations, the method may also include detecting an absence of data transmissions from the one or more STAs for more than a time period during a respective restricted TWT SP, and releasing control of the wireless medium during a remaining portion of the respective restricted TWT SP based on detecting the absence of data transmissions from the one or more STAs. In some instances, releasing control of the wireless medium may include transmitting a contention-free end (CF-END) frame on the wireless medium.

In some implementations, establishing the restricted TWT session may include transmitting a frame indicating a latency sensitive traffic priority associated with the restricted TWT session, and receiving, from each of the one or more STAs, a request to become members of the restricted TWT session based on the indicated latency sensitive traffic priority. In some instances, the indicated latency sensitive traffic priority may correspond to one or more selected traffic identifiers (TIDs). For example, the one or more selected TIDs may be associated with a voice access category (AC_VO). In some other instances, the indicated latency sensitive traffic priority may correspond to a selected traffic flow. For example, the selected traffic flow may be identified by an IP <NUM>-tuple or an IPv6 flow label.

In some implementations, the frame may be one or more of a beacon frame, a probe response frame, an association frame, or a re-association frame, and may include one or more TWT parameters associated with the restricted TWT session. In some instances, the one or more TWT parameters may be included in a TWT Parameter Information field of a TWT element carried in one or more beacon frames transmitted from the AP. In some other instances, the one or more TWT parameters may indicate whether the restricted TWT session is a peer-to-peer TWT session. In addition, or in the alternative, the one or more TWT parameters may indicate whether the restricted TWT session is full.

In some other implementations, establishing the restricted TWT session may also include verifying that each of the one or more STAs is associated with the indicated latency sensitive traffic priority, and joining the one or more STAs to the restricted TWT session based on their respective verifications. In addition, or in the alternative, establishing the restricted TWT session may also include determining a periodicity of the latency sensitive traffic associated with at least one of the one or more STAs, and configuring a TWT interval based on the determined periodicity.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a wireless communication device operating as an AP. The AP may include at least one modem, at least one processor communicatively coupled with the at least one modem, and at least one memory communicatively coupled with the at least one processor. The at least one memory may store processor-readable code that, when executed by the at least one processor in conjunction with the at least one modem, is configured to establish a restricted TWT session on a wireless medium for one or more STAs associated with latency sensitive traffic. The restricted TWT session may include one or more restricted TWT SPs for communications on the wireless medium with only the one or more STAs associated with the latency sensitive traffic. Execution of the processor-readable code may be configured to transmit a CTS frame on the wireless medium at a start of each restricted TWT SP of the one or more restricted TWT SPs. The CTS frame may indicate to other STAs that the wireless medium is unavailable for a duration of the respective restricted TWT SP. Execution of the processor-readable code may be configured to transmit latency sensitive data to or receive latency sensitive data from the one or more STAs during at least one restricted TWT SP of the one or more restricted TWT SPs. In some implementations, an RA of the CTS frame may be set to a configured MAC address indicating that STAs belonging to the restricted TWT session are permitted to access the wireless medium during the respective restricted TWT SP. In some instances, the configured MAC address may correspond to a configured NAV setting for the other STAs.

In some implementations, execution of the processor-readable code may also be configured to indicate that each of the other STAs is to terminate a TXOP on the wireless medium at or before the start of each restricted TWT SP of the one or more restricted TWT SPs. In some other implementations, execution of the processor-readable code may also be configured to indicate that each of the other STAs is not permitted to access the wireless medium during each restricted TWT SP of the one or more restricted TWT SPs. In some instances, the indications may be included in a TWT Parameter Information field of a TWT element carried in one or more beacon frames transmitted from the AP.

In some implementations, execution of the processor-readable code may also be configured to detect an absence of data transmissions from the one or more STAs for more than a time period during a respective restricted TWT SP, and to release control of the wireless medium during a remaining portion of the respective restricted TWT SP based on detecting the absence of data transmissions from the one or more STAs. In some instances, releasing control of the wireless medium may include transmitting a CF-END frame on the wireless medium.

In some implementations, establishing the restricted TWT session may include transmitting a frame indicating a latency sensitive traffic priority associated with the restricted TWT session, and receiving, from each of the one or more STAs, a request to become members of the restricted TWT session based on the indicated latency sensitive traffic priority. In some instances, the indicated latency sensitive traffic priority may correspond to one or more selected TIDs. For example, the one or more selected TIDs may be associated with a voice access category (AC_VO). In some other instances, the indicated latency sensitive traffic priority may correspond to a selected traffic flow. For example, the selected traffic flow may be identified by an IP <NUM>-tuple or an IPv6 flow label.

The following description is directed to certain implementations for the purposes of describing innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations can be implemented in any device, system, or network that is capable of transmitting and receiving radio frequency (RF) signals according to one or more of the Institute of Electrical and Electronics Engineers (IEEE) <NUM> standards, the IEEE <NUM> standards, the Bluetooth® standards as defined by the Bluetooth Special Interest Group (SIG), or the Long Term Evolution (LTE), <NUM>, <NUM> or <NUM> (New Radio (NR)) standards promulgated by the 3rd Generation Partnership Project (3GPP), among others. The described implementations can be implemented in any device, system or network that is capable of transmitting and receiving RF signals according to one or more of the following technologies or techniques: code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), single-user (SU) multiple-input multiple-output (MIMO), and multi-user (MU) MIMO. The described implementations also can be implemented using other wireless communication protocols or RF signals suitable for use in one or more of a wireless personal area network (WPAN), a wireless local area network (WLAN), a wireless wide area network (WWAN), or an internet of things (IOT) network.

Various implementations relate generally to restricted target wake time (TWT) sessions on a wireless medium. Some implementations more specifically relate to establishing a restricted TWT session for wireless stations having or associated with latency sensitive traffic having strict end-to-end latency and packet loss requirements. In accordance with some aspects of the present disclosure, an AP may establish or schedule a restricted target wake time (TWT) session on a wireless medium for one or more wireless stations (STAs) associated with latency sensitive traffic. The restricted TWT session may include a plurality of restricted TWT service periods (SPs) for communications on the wireless medium with only the one or more STAs associated with the latency sensitive traffic. The AP may transmit a clear-to-send (CTS) frame on the wireless medium at a start of each restricted TWT SP to prevent contention on the wireless medium. In some instances, the AP may set the receiver address (RA) of the CTS frame to a configured medium access control (MAC) address indicating that STAs belonging to the restricted TWT session are allowed to access the wireless medium during the respective restricted TWT SP, and may therefore ignore the CTS frame. Setting the RA of the CTS frame to the configured MAC address may also indicate a certain value to which other STAs that do not belong to the restricted TWT session may set their respective network allocation vectors (NAVs).

In some implementations, the AP may transmit a frame including one or more TWT parameters associated with the restricted TWT session. The frame, which may be a beacon frame, a probe response frame, an association frame, or a re-association frame, may also indicate a latency sensitive traffic priority associated with the restricted TWT session. In some instances, the indicated latency sensitive traffic priority may correspond to one or more selected traffic identifiers (TIDs). The selected TIDs may be associated with a certain access category (such as a voice access category), may correspond to a selected traffic flow, or may correspond to a configured label.

Particular aspects of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. As discussed, traffic originating from many real-time applications can have stringent latency requirements (e.g., very low average latency, worst case latency on the order of a few to tens of milliseconds, and small jitter). In some aspects, the described techniques provide enhanced medium access and resource reservation mechanisms. For example, by establishing a restricted TWT session for STAs having or associated with latency sensitive traffic (such as gaming traffic), the AP may provide STAs that are members of the restricted TWT session with more predictable latency, reduced worst-case latency, and reduced jitter. In this way, the AP may ensure that such STAs are afforded sufficient access to the wireless medium to meet the strict end-to-end latency and packet loss requirements associated with the latency sensitive traffic.

<FIG> shows a block diagram of an example wireless communication network such as a wireless local area network (WLAN) <NUM>. In some aspects, the wireless communication network may be referred to as a Wi-Fi network. For example, the WLAN <NUM> can be a network implementing at least one of the IEEE <NUM> family of standards (such as that defined by the IEEE <NUM>-<NUM> specification or amendments thereof including, but not limited to, <NUM>. 11ah, <NUM>. 11ad, <NUM>. 11ay, <NUM>. 11ax, <NUM>. 11az, <NUM>. 11ba, and <NUM>. The WLAN <NUM> may include numerous wireless communication devices such as an access point (AP) <NUM> and multiple stations (STAs) <NUM>. While only one AP <NUM> is shown, the WLAN <NUM> also can include multiple APs <NUM>.

Each of the STAs <NUM> also may be referred to as a mobile station (MS), a mobile device, a mobile handset, a wireless handset, an access terminal (AT), a user equipment (UE), a subscriber station (SS), or a subscriber unit, among other possibilities. The STAs <NUM> may represent various devices such as mobile phones, personal digital assistant (PDAs), other handheld devices, netbooks, notebook computers, tablet computers, laptops, display devices (for example, TVs, computer monitors, navigation systems, among others), music or other audio or stereo devices, remote control devices ("remotes"), printers, kitchen or other household appliances, key fobs (for example, for passive keyless entry and start (PKES) systems), among other possibilities.

A single AP <NUM> and an associated set of STAs <NUM> may be referred to as a basic service set (BSS), which is managed by the respective AP <NUM>. <FIG> additionally shows an example coverage area <NUM> of the AP <NUM>, which may represent a basic service area (BSA) of the WLAN <NUM>. The BSS may be identified to users by a service set identifier (SSID), as well as to other devices by a basic service set identifier (BSSID), which may be a medium access control (MAC) address of the AP <NUM>. The AP <NUM> periodically broadcasts beacon frames ("beacons") including the BSSID to enable any STAs <NUM> within wireless range of the AP <NUM> to "associate" or re-associate with the AP <NUM> to establish a respective communication link <NUM> (hereinafter also referred to as a "Wi-Fi link"), or to maintain a communication link <NUM>, with the AP <NUM>. For example, the beacons can include an identification of a primary channel used by the respective AP <NUM> as well as a timing synchronization function for establishing or maintaining timing synchronization with the AP <NUM>. The AP <NUM> may provide access to external networks to various STAs <NUM> in the WLAN via respective communication links <NUM>.

To establish a communication link <NUM> with an AP <NUM>, each of the STAs <NUM> is configured to perform passive or active scanning operations ("scans") on frequency channels in one or more frequency bands (for example, the <NUM>, <NUM>, <NUM>, or <NUM> bands). To perform passive scanning, a STA <NUM> listens for beacons, which are transmitted by respective APs <NUM> at a periodic time interval referred to as the target beacon transmission time (TBTT) (measured in time units (TUs) where one TU may be equal to <NUM> microseconds (µs)). To perform active scanning, a STA <NUM> generates and sequentially transmits probe requests on each channel to be scanned and listens for probe responses from APs <NUM>. Each STA <NUM> may be configured to identify or select an AP <NUM> with which to associate based on the scanning information obtained through the passive or active scans, and to perform authentication and association operations to establish a communication link <NUM> with the selected AP <NUM>. The AP <NUM> assigns an association identifier (AID) to the STA <NUM> at the culmination of the association operations, which the AP <NUM> uses to track the STA <NUM>.

As a result of the increasing ubiquity of wireless networks, a STA <NUM> may have the opportunity to select one of many BSSs within range of the STA or to select among multiple APs <NUM> that together form an extended service set (ESS) including multiple connected BSSs. An extended network station associated with the WLAN <NUM> may be connected to a wired or wireless distribution system that may allow multiple APs <NUM> to be connected in such an ESS. As such, a STA <NUM> can be covered by more than one AP <NUM> and can associate with different APs <NUM> at different times for different transmissions. Additionally, after association with an AP <NUM>, a STA <NUM> also may be configured to periodically scan its surroundings to find a more suitable AP <NUM> with which to associate. For example, a STA <NUM> that is moving relative to its associated AP <NUM> may perform a "roaming" scan to find another AP <NUM> having more desirable network characteristics such as a greater received signal strength indicator (RSSI) or a reduced traffic load.

In some cases, STAs <NUM> may form networks without APs <NUM> or other equipment other than the STAs <NUM> themselves. One example of such a network is an ad hoc network (or wireless ad hoc network). Ad hoc networks may alternatively be referred to as mesh networks or peer-to-peer (P2P) networks. In some cases, ad hoc networks may be implemented within a larger wireless network such as the WLAN <NUM>. In such implementations, while the STAs <NUM> may be capable of communicating with each other through the AP <NUM> using communication links <NUM>, STAs <NUM> also can communicate directly with each other via direct wireless links <NUM>. Additionally, two STAs <NUM> may communicate via a direct communication link <NUM> regardless of whether both STAs <NUM> are associated with and served by the same AP <NUM>. In such an ad hoc system, one or more of the STAs <NUM> may assume the role filled by the AP <NUM> in a BSS. Such a STA <NUM> may be referred to as a group owner (GO) and may coordinate transmissions within the ad hoc network. Examples of direct wireless links <NUM> include Wi-Fi Direct connections, connections established by using a Wi-Fi Tunneled Direct Link Setup (TDLS) link, and other P2P group connections.

The APs <NUM> and STAs <NUM> may function and communicate (via the respective communication links <NUM>) according to the IEEE <NUM> family of standards (such as that defined by the IEEE <NUM>-<NUM> specification or amendments thereof including, but not limited to, <NUM>. 11ah, <NUM>. 11ad, <NUM>. 11ay, <NUM>. 11ax, <NUM>. 11az, <NUM>. 11ba, and <NUM>. These standards define the WLAN radio and baseband protocols for the PHY and medium access control (MAC) layers. The APs <NUM> and STAs <NUM> transmit and receive wireless communications (hereinafter also referred to as "Wi-Fi communications") to and from one another in the form of physical layer convergence protocol (PLCP) protocol data units (PPDUs). The APs <NUM> and STAs <NUM> in the WLAN <NUM> may transmit PPDUs over an unlicensed spectrum, which may be a portion of spectrum that includes frequency bands traditionally used by Wi-Fi technology, such as the <NUM> band, the <NUM> band, the <NUM> band, the <NUM> band, and the <NUM> band. Some implementations of the APs <NUM> and STAs <NUM> described herein also may communicate in other frequency bands, such as the <NUM> band, which may support both licensed and unlicensed communications. The APs <NUM> and STAs <NUM> also can be configured to communicate over other frequency bands such as shared licensed frequency bands, where multiple operators may have a license to operate in the same or overlapping frequency band or bands.

Each of the frequency bands may include multiple sub-bands or frequency channels. For example, PPDUs conforming to the IEEE <NUM>. 11n, <NUM>. 11ac, and <NUM>. 11ax standard amendments may be transmitted over the <NUM> and <NUM> bands, each of which is divided into multiple <NUM> channels. As such, these PPDUs are transmitted over a physical channel having a minimum bandwidth of <NUM>, but larger channels can be formed through channel bonding. For example, PPDUs may be transmitted over physical channels having bandwidths of <NUM>, <NUM>, <NUM>, or <NUM> by bonding together multiple <NUM> channels.

Each PPDU is a composite structure that includes a PHY preamble and a payload in the form of a PLCP service data unit (PSDU). The information provided in the preamble may be used by a receiving device to decode the subsequent data in the PSDU. In instances in which PPDUs are transmitted over a bonded channel, the preamble fields may be duplicated and transmitted in each of the multiple component channels. The PHY preamble may include both a legacy portion (or "legacy preamble") and a non-legacy portion (or "non-legacy preamble"). The legacy preamble may be used for packet detection, automatic gain control and channel estimation, among other uses. The legacy preamble also may generally be used to maintain compatibility with legacy devices. The format of, coding of, and information provided in the non-legacy portion of the preamble is based on the particular IEEE <NUM> protocol to be used to transmit the payload.

<FIG> shows an example protocol data unit (PDU) <NUM> usable for communications between an AP and a number of STAs. For example, the PDU <NUM> can be configured as a PPDU. As shown, the PDU <NUM> includes a PHY preamble <NUM> and a PHY payload <NUM>. For example, the PHY preamble <NUM> may include a legacy portion that itself includes a legacy short training field (L-STF) <NUM>, a legacy long training field (L-LTF) <NUM>, and a legacy signaling field (L-SIG) <NUM>. The PHY preamble <NUM> may also include a non-legacy portion (not shown). The L-STF <NUM> generally enables a receiving device to perform automatic gain control (AGC) and coarse timing and frequency estimation. The L-LTF <NUM> generally enables a receiving device to perform fine timing and frequency estimation and also to estimate the wireless channel. The L-SIG <NUM> generally enables a receiving device to determine a duration of the PDU and use the determined duration to avoid transmitting on top of the PDU. For example, the L-STF <NUM>, the L-LTF <NUM>, and the L-SIG <NUM> may be modulated according to a binary phase shift keying (BPSK) modulation scheme. The payload <NUM> may be modulated according to a BPSK modulation scheme, a quadrature BPSK (Q-BPSK) modulation scheme, a quadrature amplitude modulation (QAM) modulation scheme, or another appropriate modulation scheme. The payload <NUM> may generally carry higher layer data, for example, in the form of medium access control (MAC) protocol data units (MPDUs) or aggregated MPDUs (A-MPDUs).

<FIG> shows an example L-SIG <NUM> in the PDU of <FIG>. The L-SIG <NUM> includes a data rate field <NUM>, a reserved bit <NUM>, a length field <NUM>, a parity bit <NUM>, and a tail field <NUM>. The data rate field <NUM> indicates a data rate (note that the data rate indicated in the data rate field <NUM> may not be the actual data rate of the data carried in the payload <NUM>). The length field <NUM> indicates a length of the packet in units of, for example, bytes. The parity bit <NUM> is used to detect bit errors. The tail field <NUM> includes tail bits that are used by the receiving device to terminate operation of a decoder (for example, a Viterbi decoder). The receiving device utilizes the data rate and the length indicated in the data rate field <NUM> and the length field <NUM> to determine a duration of the packet in units of, for example, microseconds (µs).

<FIG> shows an example PPDU <NUM> usable for communications between an AP <NUM> and a number of STAs <NUM>. As described above, each PPDU <NUM> includes a PHY preamble <NUM> and a PSDU <NUM>. Each PSDU <NUM> may carry one or more MAC protocol data units (MPDUs). For example, each PSDU <NUM> may carry an aggregated MPDU (A-MPDU) <NUM> that includes an aggregation of multiple MPDU subframes <NUM>. Each MPDU subframe <NUM> may carry an MPDU <NUM> that may include a MAC delimiter <NUM> and a MAC header <NUM> prior to the accompanying frame body <NUM>, which includes the data portion or "payload" of the MPDU <NUM>. The frame body <NUM> may carry one or more MAC service data unit (MSDU) subframes. For example, the frame body <NUM> may carry an aggregated MSDU (A-MSDU) <NUM> including multiple MSDU subframes <NUM>. Each MSDU subframe <NUM> contains a corresponding MSDU <NUM> including a subframe header <NUM>, a frame body <NUM>, and one or more padding bits <NUM>.

Referring back to the MPDU <NUM>, the MAC header <NUM> may include a number of fields containing information that defines or indicates characteristics or attributes of data encapsulated within the frame body <NUM>. The MAC header <NUM> also includes a number of fields indicating addresses for the data encapsulated within the frame body <NUM>. For example, the MAC header <NUM> may include a combination of a source address, a transmitter address, a receiver address, or a destination address. The MAC header <NUM> may include a frame control field containing control information. The frame control field specifies the frame type, for example, a data frame, a control frame, or a management frame. The MAC header <NUM> may further include a duration field indicating a duration extending from the end of the PPDU until the end of an acknowledgment (ACK) of the last PPDU to be transmitted by the wireless communication device (for example, a block ACK (BA) in the case of an A-MPDU). The use of the duration field serves to reserve the wireless medium for the indicated duration, thus establishing the NAV. Each MPDU <NUM> may also include a frame check sequence (FCS) field <NUM> for error detection. For example, the FCS field <NUM> may include a cyclic redundancy check (CRC), and may be followed by one or more padding bits <NUM>.

As described above, APs <NUM> and STAs <NUM> can support multi-user (MU) communications. That is, concurrent transmissions from one device to each of multiple devices (for example, multiple simultaneous downlink (DL) communications from an AP <NUM> to corresponding STAs <NUM>), or concurrent transmissions from multiple devices to a single device (for example, multiple simultaneous uplink (UL) transmissions from corresponding STAs <NUM> to an AP <NUM>). To support the MU transmissions, the APs <NUM> and STAs <NUM> may utilize multi-user multiple-input, multiple-output (MU-MIMO) and multi-user orthogonal frequency division multiple access (MU-OFDMA) techniques.

In MU-OFDMA schemes, the available frequency spectrum of the wireless channel may be divided into multiple resource units (RUs) each including a number of different frequency subcarriers ("tones"). Different RUs may be allocated or assigned by an AP <NUM> to different STAs <NUM> at particular times. The sizes and distributions of the RUs may be referred to as an RU allocation. In some implementations, RUs may be allocated in <NUM> intervals, and as such, the smallest RU may include <NUM> tones consisting of <NUM> data tones and <NUM> pilot tones. Consequently, in a <NUM> channel, up to <NUM> RUs (such as <NUM>, <NUM>-tone RUs) may be allocated (because some tones are reserved for other purposes). Similarly, in a <NUM> channel, up to <NUM> RUs may be allocated. Larger <NUM> tone, <NUM> tone, <NUM> tone, <NUM> tone and <NUM> tone RUs may also be allocated. Adjacent RUs may be separated by a null subcarrier (such as a DC subcarrier), for example, to reduce interference between adjacent RUs, to reduce receiver DC offset, and to avoid transmit center frequency leakage.

For UL MU transmissions, an AP <NUM> can transmit a trigger frame to initiate and synchronize an UL MU-OFDMA or UL MU-MIMO transmission from multiple STAs <NUM> to the AP <NUM>. Such trigger frames may thus enable multiple STAs <NUM> to send UL traffic to the AP <NUM> concurrently in time. A trigger frame may address one or more STAs <NUM> through respective association identifiers (AIDs), and may assign each AID (and thus each STA <NUM>) one or more RUs that can be used to send UL traffic to the AP <NUM>. The AP also may designate one or more random access (RA) RUs that unscheduled STAs <NUM> may contend for.

<FIG> shows a block diagram of an example wireless communication device <NUM>. In some implementations, the wireless communication device <NUM> can be an example of a device for use in a STA such as one of the STAs <NUM> described above with reference to <FIG>. In some implementations, the wireless communication device <NUM> can be an example of a device for use in an AP such as the AP <NUM> described above with reference to <FIG>. The wireless communication device <NUM> is capable of transmitting (or outputting for transmission) and receiving wireless communications (for example, in the form of wireless packets). For example, the wireless communication device can be configured to transmit and receive packets in the form of physical layer convergence protocol (PLCP) protocol data units (PPDUs) and medium access control (MAC) protocol data units (MPDUs) conforming to an IEEE <NUM> standard, such as that defined by the IEEE <NUM>-<NUM> specification or amendments thereof including, but not limited to, <NUM>. 11ah, <NUM>. 11ad, <NUM>. 11ay, <NUM>. 11ax, <NUM>. 11az, <NUM>. 11ba, and <NUM>.

The wireless communication device <NUM> can be, or can include, a chip, system on chip (SoC), chipset, package, or device that includes one or more modems <NUM>, for example, a Wi-Fi (IEEE <NUM> compliant) modem. In some implementations, the one or more modems <NUM> (collectively "the modem <NUM>") additionally include a WWAN modem (for example, a 3GPP <NUM> LTE or <NUM> compliant modem). In some implementations, the wireless communication device <NUM> also includes one or more radios <NUM> (collectively "the radio <NUM>"). In some implementations, the wireless communication device <NUM> further includes one or more processors, processing blocks or processing elements <NUM> (collectively "the processor <NUM>"), and one or more memory blocks or elements <NUM> (collectively "the memory <NUM>").

The modem <NUM> can include an intelligent hardware block or device such as, for example, an application-specific integrated circuit (ASIC) among other possibilities. The modem <NUM> is generally configured to implement a PHY layer. For example, the modem <NUM> is configured to modulate packets and to output the modulated packets to the radio <NUM> for transmission over the wireless medium. The modem <NUM> is similarly configured to obtain modulated packets received by the radio <NUM> and to demodulate the packets to provide demodulated packets. In addition to a modulator and a demodulator, the modem <NUM> may further include digital signal processing (DSP) circuitry, automatic gain control (AGC), a coder, a decoder, a multiplexer, and a demultiplexer. For example, while in a transmission mode, data obtained from the processor <NUM> is provided to a coder, which encodes the data to provide encoded bits. The encoded bits are then mapped to points in a modulation constellation (using a selected MCS) to provide modulated symbols. The modulated symbols may then be mapped to a number NSS of spatial streams or a number NSTS of space-time streams. The modulated symbols in the respective spatial or space-time streams may then be multiplexed, transformed via an inverse fast Fourier transform (IFFT) block, and subsequently provided to the DSP circuitry for Tx windowing and filtering. The digital signals may then be provided to a digital-to-analog converter (DAC). The resultant analog signals may then be provided to a frequency upconverter, and ultimately, the radio <NUM>. In implementations involving beamforming, the modulated symbols in the respective spatial streams are precoded via a steering matrix prior to their provision to the IFFT block.

While in a reception mode, digital signals received from the radio <NUM> are provided to the DSP circuitry, which is configured to acquire a received signal, for example, by detecting the presence of the signal and estimating the initial timing and frequency offsets. The DSP circuitry is further configured to digitally condition the digital signals, for example, using channel (narrowband) filtering, analog impairment conditioning (such as correcting for I/Q imbalance), and applying digital gain to ultimately obtain a narrowband signal. The output of the DSP circuitry may then be fed to the AGC, which is configured to use information extracted from the digital signals, for example, in one or more received training fields, to determine an appropriate gain. The output of the DSP circuitry also is coupled with the demodulator, which is configured to extract modulated symbols from the signal and, for example, compute the logarithm likelihood ratios (LLRs) for each bit position of each subcarrier in each spatial stream. The demodulator is coupled with the decoder, which may be configured to process the LLRs to provide decoded bits. The decoded bits from all of the spatial streams are then fed to the demultiplexer for demultiplexing. The demultiplexed bits may then be descrambled and provided to the MAC layer (the processor <NUM>) for processing, evaluation, or interpretation.

The radio <NUM> generally includes at least one radio frequency (RF) transmitter (or "transmitter chain") and at least one RF receiver (or "receiver chain"), which may be combined into one or more transceivers. For example, the RF transmitters and receivers may include various DSP circuitry including at least one power amplifier (PA) and at least one low-noise amplifier (LNA), respectively. The RF transmitters and receivers may in turn be coupled to one or more antennas. For example, in some implementations, the wireless communication device <NUM> can include, or be coupled with, multiple transmit antennas (each with a corresponding transmit chain) and multiple receive antennas (each with a corresponding receive chain). The symbols output from the modem <NUM> are provided to the radio <NUM>, which then transmits the symbols via the coupled antennas. Similarly, symbols received via the antennas are obtained by the radio <NUM>, which then provides the symbols to the modem <NUM>.

The processor <NUM> can include an intelligent hardware block or device such as, for example, a processing core, a processing block, a central processing unit (CPU), a microprocessor, a microcontroller, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a programmable logic device (PLD) such as a field programmable gate array (FPGA), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The processor <NUM> processes information received through the radio <NUM> and the modem <NUM>, and processes information to be output through the modem <NUM> and the radio <NUM> for transmission through the wireless medium. For example, the processor <NUM> may implement a control plane and MAC layer configured to perform various operations related to the generation and transmission of MPDUs, frames, or packets. The MAC layer is configured to perform or facilitate the coding and decoding of frames, spatial multiplexing, space-time block coding (STBC), beamforming, and OFDMA resource allocation, among other operations or techniques. In some implementations, the processor <NUM> may generally control the modem <NUM> to cause the modem to perform various operations described above.

The memory <NUM> can include tangible storage media such as random-access memory (RAM) or read-only memory (ROM), or combinations thereof. The memory <NUM> also can store non-transitory processor- or computer-executable software (SW) code containing instructions that, when executed by the processor <NUM>, cause the processor to perform various operations described herein for wireless communication, including the generation, transmission, reception, and interpretation of MPDUs, frames or packets. For example, various functions of components disclosed herein, or various blocks or steps of a method, operation, process, or algorithm disclosed herein, can be implemented as one or more modules of one or more computer programs.

<FIG> shows a block diagram of an example AP <NUM>. For example, the AP <NUM> can be an example implementation of the AP <NUM> described with reference to <FIG>. The AP <NUM> includes a wireless communication device (WCD) <NUM>. For example, the wireless communication device <NUM> may be an example implementation of the wireless communication device <NUM> described with reference to <FIG>. The AP <NUM> also includes multiple antennas <NUM> coupled with the wireless communication device <NUM> to transmit and receive wireless communications. In some implementations, the AP <NUM> additionally includes an application processor <NUM> coupled with the wireless communication device <NUM>, and a memory <NUM> coupled with the application processor <NUM>. The AP <NUM> further includes at least one external network interface <NUM> that enables the AP <NUM> to communicate with a core network or backhaul network to gain access to external networks including the Internet. For example, the external network interface <NUM> may include one or both of a wired (for example, Ethernet) network interface and a wireless network interface (such as a WWAN interface). Ones of the aforementioned components can communicate with other ones of the components directly or indirectly, over at least one bus. The AP <NUM> further includes a housing that encompasses the wireless communication device <NUM>, the application processor <NUM>, the memory <NUM>, and at least portions of the antennas <NUM> and external network interface <NUM>.

<FIG> shows a block diagram of an example STA <NUM>. For example, the STA <NUM> can be an example implementation of one or more of the STAs <NUM> described with reference to <FIG>. The STA <NUM> includes a wireless communication device <NUM>. For example, the wireless communication device <NUM> may be an example implementation of the wireless communication device <NUM> described with reference to <FIG>. The STA <NUM> also includes one or more antennas <NUM> coupled with the wireless communication device <NUM> to transmit and receive wireless communications. The STA <NUM> additionally includes an application processor <NUM> coupled with the wireless communication device <NUM>, and a memory <NUM> coupled with the application processor <NUM>. In some implementations, the STA <NUM> further includes a user interface (UI) <NUM> (such as a touchscreen or keypad) and a display <NUM>, which may be integrated with the UI <NUM> to form a touchscreen display. In some implementations, the STA <NUM> may further include one or more sensors <NUM> such as, for example, one or more inertial sensors, accelerometers, temperature sensors, pressure sensors, or altitude sensors. Ones of the aforementioned components can communicate with other ones of the components directly or indirectly, over at least one bus. The STA <NUM> further includes a housing (not shown for simplicity) that encompasses the wireless communication device <NUM>, the application processor <NUM>, the memory <NUM>, and at least portions of the antennas <NUM>, UI <NUM>, and display <NUM>.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively.

In some implementations, the process <NUM> begins in block <NUM> with establishing a restricted target wake time (TWT) session on a wireless medium for one or more wireless stations (STAs) associated with latency sensitive traffic, the restricted TWT session including one or more restricted TWT service periods (SPs) for communications on the wireless medium with only the one or more STAs associated with the latency sensitive traffic. In block <NUM>, the process <NUM> proceeds with transmitting a clear-to-send (CTS) frame on the wireless medium at a start of each restricted TWT SP of the one or more restricted TWT SPs, the CTS frame indicating to other STAs that the wireless medium is busy or unavailable for a duration of the respective restricted TWT SP. In block <NUM>, the process <NUM> proceeds with transmitting latency sensitive data to, or receiving latency sensitive data from, the one or more STAs during at least one restricted TWT SP of the one or more restricted TWT SPs.

In some implementations, a receiver address (RA) of the CTS frame is set to a configured medium access control (MAC) address indicating that STAs belonging to the restricted TWT session are permitted to access the wireless medium during the respective restricted TWT SP. In some instances, the configured MAC address corresponds to a configured network allocation vector (NAV) setting for the other STAs.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. In some instances, the process <NUM> may be performed after establishing the restricted TWT session in block <NUM> of <FIG>. For example, at block <NUM>, the process <NUM> includes indicating that each of the other STAs is to terminate a transmit opportunity (TXOP) on the wireless medium at or before the start of each restricted TWT SP of the one or more restricted TWT SPs. In some instances, the indication may be included in a TWT Element carried in one or more beacon frames transmitted from the AP. In some other instances, the indication may be included in another field of the beacon frames, or may be included in another suitable management frame transmitted from the AP.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. In some instances, the process <NUM> may be performed after establishing the restricted TWT session in block <NUM> of <FIG>. For example, at block <NUM>, the process <NUM> includes indicating that each of the other STAs is not permitted to access the wireless medium during each restricted TWT SP of the one or more restricted TWT SPs. In some instances, the indication may be included in a TWT Element carried in one or more beacon frames transmitted from the AP. In some other instances, the indication may be included in another field of the beacon frames, or may be included in another suitable management frame transmitted from the AP.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. In some instances, the process <NUM> may be performed after transmitting or receiving the latency sensitive data in block <NUM> of <FIG>. For example, at block <NUM>, the process <NUM> includes permitting one or more of the other STAs to access the wireless medium during time periods outside the one or more restricted TWT SPs of the restricted TWT session.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. In some instances, the process <NUM> may be performed after establishing the restricted TWT session in block <NUM> of <FIG>. For example, at block <NUM>, the process <NUM> begins with detecting an absence of data transmissions from the one or more STAs for more than a time period during a respective restricted TWT SP. At block <NUM>, the process <NUM> proceeds with releasing control of the wireless medium during a remaining portion of the respective restricted TWT SP based on detecting the absence of data transmissions from the one or more STAs. In some instances, the AP may release control of the wireless medium by transmitting a contention-free end (CF-END) frame on the wireless medium, which may signal an end of the respective restricted TWT SP.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. In some instances, the process <NUM> may be one implementation of establishing the restricted TWT session in block <NUM> of <FIG>. For example, at block <NUM>, the process <NUM> begins with transmitting a frame indicating a latency sensitive traffic priority associated with the restricted TWT session. At block <NUM>, the process <NUM> proceeds with receiving, from each of the one or more STAs, a request to become a member of the restricted TWT session based on the indicated latency sensitive traffic priority.

In some implementations, the indicated latency sensitive traffic priority may correspond to one or more selected traffic identifiers (TIDs). In some instances, the one or more selected TIDs may be associated with a voice access category (AC_VO). In some other instances, the one or more selected TIDs may be associated with another access category. In some other implementations, the indicated latency sensitive traffic priority may correspond to a selected traffic flow. In some instances, the selected traffic flow may be identified by an IP <NUM>-tuple or an IPv6 flow label.

In some implementations, the frame may be one or more of a beacon frame, a probe response frame, an association frame, or a re-association frame. In some instances, the frame may include one or more TWT parameters associated with the restricted TWT session. The one or more TWT parameters may be included in a TWT Parameter Information field of a TWT element carried in one or more beacon frames transmitted by the AP. In some instances, the one or more TWT parameters may indicate whether the restricted TWT session is a peer-to-peer TWT session. In some other instances, the one or more TWT parameters may indicate whether the restricted TWT session is full.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. In some instances, the process <NUM> may be performed after establishing the restricted TWT session in block <NUM> of <FIG>. For example, at block <NUM>, the process <NUM> includes permitting the one or more STAs to transmit or receive only traffic corresponding to the one or more selected TIDs during each restricted TWT SP of the one or more restricted TWT SPs.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. In some instances, the process <NUM> may be performed before or concurrently with establishing the restricted TWT session in block <NUM> of <FIG>. For example, at block <NUM>, the process <NUM> begins with verifying that each of the one or more STAs is associated with the indicated latency sensitive traffic priority. At block <NUM>, the process <NUM> proceeds with joining the one or more STAs to the restricted TWT session based on their respective verifications.

<FIG> shows a flowchart illustrating an example process <NUM> for wireless communication that supports restricted TWT sessions according to some implementations. The process <NUM> may be performed by a wireless communication device such as the wireless communication device <NUM> described above with reference to <FIG>. In some implementations, the process <NUM> may be performed by a wireless communication device operating as or within an AP, such as one of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. In some instances, the process <NUM> may be one implementation of establishing the restricted TWT session in block <NUM> of <FIG>. For example, at block <NUM>, the process <NUM> begins with determining a periodicity of the latency sensitive traffic associated with at least one of the one or more STAs. At block <NUM>, the process <NUM> proceeds with configuring a TWT wake interval based on the determined periodicity.

<FIG> shows a timing diagram 1300A illustrating the transmissions of communications that support restricted TWT sessions according to some implementations. The communications shown in the timing diagram 1300A are exchanged between an AP, two wireless stations STA1a and STA1b that are associated with latency sensitive traffic and that are members of a TWT session established by the AP, and another wireless station STA2 that is not associated with latency sensitive traffic and that is not a member of the TWT session established by the AP. As such, stations STA1a and STA1b may be referred to herein as latency sensitive STAs, and station STA2 may be referred to herein as a non-latency sensitive STA. The AP may be one example of the APs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively. Each of the wireless stations STA1a, STA1b, and STA2 may be one example of the STAs <NUM> and <NUM> described above with reference to <FIG> and <FIG>, respectively.

For simplicity, only two stations STA1a and STA1b are shown as members of the restricted TWT session, and only one station STA2 is shown to be associated with the AP but not a member of the restricted TWT session. In some other implementations, the restricted TWT session may include fewer or more STAs than those depicted in the example of <FIG>.

Prior to time t<NUM>, the AP may establish the restricted TWT session for one or more STAs associated with latency sensitive traffic. The restricted TWT session may include one or more restricted TWT service periods (SPs) for communications on the wireless medium with only for STAs that are associated with latency sensitive traffic and that are members of the restricted TWT session. As discussed, each of stations STA1a and STA1b is associated with latency sensitive traffic and is a member of the restricted TWT session; station STA2 is not associated with latency sensitive traffic and is not a member of the restricted TWT session.

The AP may advertise the restricted TWT session by including a TWT Element in beacon frames broadcasted to its associated STAs. The TWT Element may indicate the existence of the restricted TWT session, may indicate that the restricted TWT session is associated with latency sensitive traffic, and may indicate one or more parameters of the restricted TWT session. For example, the one or more parameters may indicate a duration of the restricted TWT SPs, may indicate a duration of the restricted TWT wake interval, may indicate whether the restricted TWT session is a broadcast TWT session or an individual TWT session, may indicate whether the restricted TWT session is a peer-to-peer TWT session, may indicate the operating channel, may indicate the target wake times, and may indicate other TWT information.

In some implementations, the TWT Element may indicate that the restricted TWT session is for STAs that have or are associated with latency sensitive traffic corresponding to one or more selected traffic identifiers (TIDs). For example, in some instances, the selected TIDs may be associated with a voice access category (AC_VO). In some other implementations, the TWT Element may indicate that the restricted TWT session is for STAs that have or are associated with latency sensitive traffic corresponding to a configured label or to a selected traffic flow. For example, in some instances, the configured label or the selected traffic flow may be identified by an IP <NUM>-tuple or an IPv6 flow label. The stations STA1a and STA1b may receive the TWT Element, and may request the AP to add or join STA1a and STA1b to the restricted TWT session. In some instances, the requests sent by stations STA1a and STA1b may indicate that the respective stations STA1a and STA1b have latency sensitive traffic corresponding to the selected TIDs indicated in the TWT Element. The AP may verify that the TID(s) associated with the respective traffic flows of stations STA1a and STA1b match the selected TIDs indicated in the TWT Element before allowing the stations STA1a and STA1b to join the restricted TWT session.

In some instances, the TWT element may also include an indication for other STAs (such as STA2) to terminate their respective TXOPs on the wireless medium at or before the start of each restricted TWT SP of the restricted TWT session. For example, STA2 may receive one or more beacon frames broadcast from the AP, may decode the TWT Element, and may terminate its transmission of UL data at or before time t<NUM> based on the indication. In some instances, the indication to terminate TXOPs may be carried in the TWT Parameter Information field of the TWT element.

At time t<NUM>, which corresponds to the start of the restricted TWT SP, the stations STA1a and STA1b wake up, and the AP transmits a clear-to-send (CTS) frame on the wireless medium. The CTS frame may indicate to STA2 (and other STAs which do not belong to the restricted TWT session) that the wireless medium is unavailable for the duration of the restricted TWT SP. Station STA2 (and the other STAs) receives the CTS frame and does not access the wireless medium during the restricted TWT SP, for example, by setting its NAV to a time period corresponding to the duration of the restricted TWT SP. In some instances, the AP may set the receiver address (RA) of the CTS frame to a configured MAC address that indicates a certain value to which STA2 and other non-participating STAs may set their respective NAVs. Setting the RA of the CTS frame to the configured MAC address may also indicate that the stations STA1a and STA1b (and additional STAs that have joined the restricted TWT session) can ignore the CTS frame (and therefore do not set their NAVs).

As shown, STA1a transmits UL data on the wireless medium to the AP at time t<NUM>, and STA1b transmits UL data on the wireless medium to the AP at time t<NUM>. In some other implementations, stations STA1a and STA1b may concurrently transmit UL data to the AP using any suitable multi-user signaling technique (such as OFDMA or MU-MIMO).

At time t<NUM>, the restricted TWT SP ends, and station STA2 may access the wireless medium. In some instances, STA2 may use a contention-based channel access mechanism (such as an EDCA mechanism) to gain access to the wireless medium. In the example of <FIG>, STA2 gains access to the wireless medium, and transmits UL data to the AP at time t<NUM>. Time t<NUM> may signal an end to the restricted TWT wake interval.

<FIG> shows a timing diagram 1300B illustrating the transmissions of communications that support restricted TWT sessions according to some other implementations. The timing diagram 1300B of <FIG> is similar to the timing diagram 1300A of <FIG>, except that in the example of <FIG>, the AP detects an absence of data transmissions from stations STA1a and STA1b during the restricted TWT SP. Specifically, the AP may monitor the wireless medium for UL transmissions from the stations STA1a and STA1b during the restricted TWT SP. If the AP does not detect any UL transmissions from the stations STA1a and STA1b for more than a certain time period of the restricted TWT SP, the AP may release the wireless medium. In some instances, the AP may release the wireless medium by transmitting a contention-free end (CF-END) frame that terminates the restricted TWT SP. STA2 receives the CF-END frame, gains access to the wireless medium, and transmits UL data to the AP at time t<NUM>. Time t<NUM> indicates the scheduled end of the restricted TWT SP, and time t<NUM> indicates the end of the restricted TWT wake interval.

<FIG> shows an example structure of a TWT Element <NUM> usable for wireless communications that support restricted TWT sessions according to some implementations. The TWT Element <NUM> may include an element ID field <NUM>, a length field <NUM>, a control field <NUM>, and a TWT parameter information field <NUM>. The element ID field <NUM> indicates that the element is a TWT Element. The length field <NUM> indicates a length of the TWT Element <NUM>. The control field <NUM> includes various control information for the restricted TWT session. The TWT parameter information field <NUM> contains either a single individual TWT Parameter Set field or one or more Broadcast TWT Parameter Set fields.

<FIG> shows an example structure of a broadcast TWT Parameter Set field <NUM> usable for wireless communications that support restricted TWT sessions according to some implementations. The broadcast TWT Parameter Set field <NUM> may include a request type field <NUM>, a target wake time field <NUM>, a nominal minimum TWT wake duration field <NUM>, a TWT wake interval mantissa field <NUM>, and a broadcast TWT Info field <NUM>.

<FIG> shows an example structure of a Request Type field <NUM> of a Broadcast TWT Parameter Set field usable for wireless communications that support restricted TWT sessions according to some implementations. The Request Type field <NUM> may include a TWT request field <NUM>, a TWT setup command field <NUM>, a trigger field <NUM>, a last broadcast parameter set field <NUM>, a flow type field <NUM>, a broadcast TWT recommendation field <NUM>, a TWT wake interval exponent field <NUM>, and a number of reserved bits <NUM>. In some implementations, the broadcast TWT recommendation field <NUM> may indicates whether the restricted TWT session is a peer-to-peer TWT session or a broadcast TWT session.

<FIG> shows a block diagram of an example wireless communication device <NUM> according to some implementations. In some implementations, the wireless communication device <NUM> is configured to perform one or more of the processes described above with reference to <FIG>, <FIG>, <FIG>, <FIG>. In some implementations, the wireless communication device <NUM> can be an example implementation of the wireless communication device <NUM> described above with reference to <FIG>. For example, the wireless communication device <NUM> can be a chip, SoC, chipset, package or device that includes at least one processor and at least one modem (for example, a Wi-Fi (IEEE <NUM>) modem or a cellular modem).

The wireless communication device <NUM> includes a reception component <NUM>, a communication manager <NUM>, and a transmission component <NUM>. The communication manager <NUM> may further include a restricted TWT session component <NUM>, an early TWT SP termination component <NUM>, and a latency sensitive traffic determination component <NUM>. Portions of one or more of the components <NUM>, <NUM>, and <NUM> may be implemented at least in part in hardware or firmware. In some implementations, at least one of the components <NUM>, <NUM>, or <NUM> is implemented at least in part as software stored in a memory (such as the memory <NUM>). For example, portions of one or more of the components <NUM>, <NUM>, and <NUM> can be implemented as non-transitory instructions or code executable by a processor (such as the processor <NUM>) to perform the functions or operations of the respective component.

The reception component <NUM> is configured to receive RX signals from other wireless communication devices. In some implementations, the RX signals may include UL data from one or more STAs belonging to a restricted TWT session (such as latency sensitive STAs), may include UL data from one or more other STAs (such as non-latency sensitive STAs), and may include requests to join the restricted TWT session. In some implementations, the restricted TWT session component <NUM> establishes and schedules one or more restricted TWT sessions on a wireless medium. The early TWT SP termination component <NUM> determines whether there is an absence of data transmissions from STAs belonging to the restricted TWT session for more than a certain time period of a respective TWT SP. The latency sensitive traffic determination component <NUM> determines whether traffic associated with a STA qualifies as latency sensitive traffic, for example, based on whether a TID of the STA's traffic flow matches one or more TIDs indicated in the TWT Element. The transmission component <NUM> is configured to transmit TX signals to other wireless communication devices. In some implementations, the TX signals may include a beacon frames, CTS frames, CF-END frames, or trigger frames.

As used herein, a phrase referring to "at least one of" or "one or more of" a list of items refers to any combination of those items, including single members. For example, "at least one of: a, b, or c" is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a and b and c.

The various illustrative components, logic, logical blocks, modules, circuits, operations, and algorithm processes described in connection with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware, or software, including the structures disclosed in this specification and the structural equivalents thereof.

Various modifications to the implementations described in this disclosure may be readily apparent to persons having ordinary skill in the art, and the generic principles defined herein may be applied to other implementations.

Additionally, various features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. As such, although features may be described above as acting in particular combinations, and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Claim 1:
A method (<NUM>) for wireless communication performed by an access point, AP, comprising:
establishing (<NUM>) a restricted target wake time, TWT, session on a wireless medium for one or more wireless stations, STAs, associated with latency sensitive traffic, the restricted TWT session including one or more restricted TWT service periods, SPs, for communications on the wireless medium with only the one or more STAs associated with the latency sensitive traffic;
transmitting (<NUM>) a clear-to-send, CTS, frame on the wireless medium at a start of each restricted TWT SP of the one or more restricted TWT SPs, the CTS frame indicating to other STAs that the wireless medium is unavailable for a duration of the respective restricted TWT SP; and
transmitting (<NUM>) latency sensitive data to, or receiving latency sensitive data from, the one or more STAs during at least one restricted TWT SP of the one or more restricted TWT SPs.