Time Synchronization Over Wireless Networks for Latency-Sensitive Traffic

Abstract

The present disclosure provides a system and method for synchronizing wireless devices with each other. In some implementations, the device transmits an indication of an extended synchronization mode to at least one wireless station (STA) on a first communication link associated with a first access point (AP) of the device. The device transmits a plurality of synchronization frames during the extended synchronization mode on the first communication link more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between the first AP and a second AP of the device. In some instances, at least one of the plurality of synchronization frames can be a fast initial link setup (FILS) discovery frame carrying a TSF value of the first AP.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS)

[0001] This patent application claims priority to U.S. patent application Ser. No. 17 / 717,791 by NAIK et al., entitled "TIME SYNCHRONIZATION OVER A WIRELESS NETWORK FOR LATENCY-SENSITIVE TRAFFIC," filed on April 11, 2022, which is assigned to the assignee of this application and expressly incorporated by reference into this specification.

[0002] FIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to wireless communications, and more particularly to maintaining synchronization between wireless stations (STAs) and each of multiple access points (APs) of a device. [Background technology]

[0003]

[0003] A wireless local area network (WLAN) may be formed by one or more access points (APs) that provide a shared wireless medium for use by several client devices such as wireless stations (STAs). The basic building block of a WLAN that conforms to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards is a Basic Service Set (BSS) managed by the AP. Each BSS is identified by a Basic Service Set Identifier (BSSID) that is advertised by the AP in beacon frames that are periodically broadcast over the wireless medium so that STAs within wireless range of the AP can associate with the AP and establish a wireless communication link with the WLAN.

[0004]

[0004] Some wireless communication devices may be associated with low-latency applications that have strict end-to-end latency, throughput, and timing requirements for data traffic. Exemplary low-latency applications include, but are not limited to, real-time gaming applications, video communications, and augmented reality (AR) and virtual reality (VR) applications (collectively referred to as extended reality (XR) applications). Such low-latency applications may specify various latency, throughput, and timing requirements for wireless communication systems that provide connectivity to these applications. Therefore, it is desirable to ensure that a WLAN can meet the various latency, throughput, and timing requirements of such low-latency applications. Summary of the Invention

[0005]

[0005] The systems, methods, and devices of the present disclosure each have several innovative aspects, no single aspect of which is solely responsible for the desirable attributes disclosed herein.

[0006]

[0006] One innovative aspect of the subject matter described in this disclosure may be implemented in a wireless device. The wireless device may include at least one processor and at least one memory communicatively coupled to the at least one processor. In some implementations, the memory may store processor-readable code that, when executed by the at least one processor, is configured to transmit an indication of an extended synchronization mode to at least one wireless station (STA) over a first communication link associated with a first access point (AP) of the device. Execution of the processor-readable code is configured to transmit a plurality of synchronization frames during the extended synchronization mode over the first communication link more frequently than Target Beacon Transmission Times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a Timing Synchronization Function (TSF) offset between the first AP and a second AP of the device. In some aspects, each of the plurality of synchronization frames may also indicate a TSF value of the first AP. In some cases, the indication may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a Target Wake Time (TWT) response frame transmitted on the first communication link.

[0007] In various implementations, the device may be an AP multi-link device (MLD) including a first AP and a second AP, the first AP being associated with a first communication link and the second AP being associated with a second communication link occupying a different frequency band than the first communication link. In some implementations, the extended synchronization mode may be established with one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs scheduled on the first communication link. In some cases, at least one of the multiple synchronization frames may be a Fast Initial Link Setup (FILS) discovery frame carrying a TSF value of the first AP and a TSF offset value of the second AP. In other cases, the time period between successive transmissions of the synchronization frames may be about 20 milliseconds. In various aspects, the multiple synchronization frames may be transmitted at a data rate that is greater than a basic data rate associated with a beacon frame transmission on the first communications link.

[0008] In various implementations, the execution of the processor-readable code may be configured to terminate the extended synchronous mode in response to an indication of timing synchronization between the first AP and each of the plurality of STAs participating in the extended synchronous mode. In some instances, the termination of the extended synchronous mode may be further based on an indication of timing synchronization between the second AP and each of the plurality of STAs participating in the extended synchronous mode.

[0009]

[0009] In some other implementations, execution of the processor-readable code may be configured to receive a request from one or more STAs to initiate an extended synchronous mode, and an indication of the extended synchronous mode is transmitted based on the request.

[0010] In some implementations, execution of the processor-readable code can be configured to indicate to at least one STA a start time of the extended synchronization mode. In some instances, the indicated start time can be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a TWT response frame transmitted on the first communication link.

[0011]

[0011] In another implementation, the execution of the processor-readable code may be configured to indicate to at least one STA whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device. In some cases, the indication of the common clock or the common TSF value across the first AP and the second AP of the device may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a synchronization frame.

[0012]

[0012] In some other implementations, the execution of the processor-readable code may be configured to obtain a TSF offset between the first AP and each of the plurality of STAs, and indicate to each of the plurality of STAs whether participation in the extended synchronization mode is mandatory or voluntary based at least in part on the TSF offset. In some cases, whether participation in the extended synchronization mode is mandatory or voluntary for at least some of the plurality of STAs may be further based on an indication of latency-sensitive traffic on the first communication link. In some aspects, the execution of the processor-readable code may be configured to reject association requests from STAs that do not support the extended synchronization mode during a time period starting before a start time of the extended synchronization mode.

[0013] In various implementations, execution of the processor readable code may be configured to receive frames from the at least one STA indicating one or more of: an amount of clock drift between the at least one STA and the first AP during each beacon interval, whether the at least one STA participates in an enhanced synchronization mode, whether the at least one STA receives beacon frames on the first communication link or on a second communication link associated with the second AP, or a frequency at which the at least one STA receives beacon frames or synchronization frames indicating TSF information of the first AP. Execution of the processor readable code may be configured to schedule one or more TWT SPs or one or more r-TWT SPs for latency sensitive traffic on the first communication link based at least in part on the one or more instructions received from the at least one STA.

[0014] Another innovative aspect of the subject matter described in this disclosure may be implemented as a method for wireless communication by a device. In some implementations, the method includes transmitting an indication of an extended synchronization mode to at least one STA on a first communication link associated with a first AP of the device. The method includes transmitting a plurality of synchronization frames during the extended synchronization mode on the first communication link more frequently than a TBTT associated with the first communication link, each of the plurality of synchronization frames indicating a TSF offset between the first AP and a second AP of the device. In some aspects, each of the plurality of synchronization frames may also indicate a TSF value of the first AP. In some instances, the indication may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a TWT response frame transmitted on the first communication link.

[0015]

[0015] In various implementations, the device may be an AP MLD including a first AP and a second AP, the first AP being associated with a first communication link, and the second AP being associated with a second communication link occupying a different frequency band than the first communication link. In some implementations, the extended synchronization mode may be established with one or more TWT SPs or one or more restricted r-TWT SPs scheduled on the first communication link. In some cases, at least one of the multiple synchronization frames may be a FILS discovery frame carrying a TSF value of the first AP and a TSF offset value of the second AP. In other cases, the time period between successive transmissions of the synchronization frames may be about 20 milliseconds. In various aspects, the multiple synchronization frames may be transmitted at a data rate greater than a basic data rate associated with a beacon frame transmission on the first communication link.

[0016] In various implementations, the method may also include terminating the extended synchronization mode in response to an indication of timing synchronization between the first AP and each of the plurality of STAs participating in the extended synchronization mode. In some instances, the termination of the extended synchronization mode may be further based on an indication of timing synchronization between the second AP and each of the plurality of STAs participating in the extended synchronization mode.

[0017]

[0017] In some other implementations, the method may also include receiving a request from one or more STAs to initiate the extended synchronization mode, and an indication of the extended synchronization mode is sent based on the request.

[0018] In some implementations, the method may also include indicating a start time of the extended synchronization mode to the at least one STA. In some cases, the indicated start time may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a TWT response frame transmitted on the first communication link.

[0019]

[0019] In other implementations, the method may also include indicating to at least one STA whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device. In some cases, the indication of the common clock or the common TSF value across the first AP and the second AP of the device may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a synchronization frame.

[0020]

[0020] In some other implementations, the method may also include obtaining a TSF offset between the first AP and each of the plurality of STAs, and indicating to each of the plurality of STAs whether participation in the extended synchronization mode is mandatory or voluntary based at least in part on the TSF offset. In some cases, whether participation in the extended synchronization mode is mandatory or voluntary for at least some of the plurality of STAs may be further based on an indication of latency-sensitive traffic on the first communication link. In some aspects, the method may also include rejecting association requests from STAs that do not support the extended synchronization mode during a time period starting before a start time of the extended synchronization mode.

[0021] In various implementations, the method may also include receiving a frame from the at least one STA indicating one or more of: an amount of clock drift between the at least one STA and the first AP during each beacon interval, whether the at least one STA participates in an extended synchronization mode, whether the at least one STA receives beacon frames on the first communication link or on a second communication link associated with the second AP, or a frequency at which the at least one STA receives beacon frames or synchronization frames indicating TSF information of the first AP. The method may also include scheduling one or more TWT SPs or one or more r-TWT SPs for latency sensitive traffic on the first communication link based at least in part on the one or more indications received from the at least one STA.

[0022]

[0022] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. Please note that the relative dimensions of the following figures may not be drawn to scale. [Brief description of the drawings]

[0023] [Figure 1]

[0023] A pictorial diagram of an exemplary wireless communication network is shown. [Figure 2A]

[0024] 1 illustrates an exemplary protocol data unit (PDU) that may be used for communication between an access point (AP) and one or more wireless stations (STAs). [Figure 2B]

[0025] 2B illustrates exemplary fields within the PDU of FIG. 2A. [Figure 3A]

[0026] 4 illustrates another exemplary PDU that may be used for communication between an AP and one or more STAs. [Figure 3B]

[0027] 4 illustrates another exemplary PDU that may be used for communication between an AP and one or more STAs. [Figure 4]

[0028] 1 illustrates a block diagram of an exemplary wireless communication device. [Figure 5A]

[0029] 1 shows a block diagram of an exemplary access point (AP). [Figure 5B]

[0030] 1 shows a block diagram of an exemplary station (STA). [Figure 6]

[0031] 1 illustrates an exemplary communication system including an access point (AP) multilink device (MLD) and a non-AP MLD. [Figure 7]

[0032] 1 shows a timing diagram illustrating an example wireless communication. [Figure 8A]

[0033] 1 shows a timing diagram illustrating an exemplary beacon frame transmission. [Figure 8B]

[0034] 1 shows a timing diagram illustrating an example wireless communication between devices. [Figure 8C]

[0035] 4 shows another timing diagram illustrating an exemplary beacon frame transmission. [Figure 8D]

[0036] 4 shows another timing diagram illustrating exemplary wireless communication between devices. [Figure 9]

[0037] 1 shows a sequence diagram illustrating an example wireless communication supporting an extended synchronization mode, according to some implementations. [Figure 10]

[0038] 1 shows a timing diagram illustrating an example wireless communication supporting an extended synchronous mode, according to some implementations. [Figure 11]

[0039] 1 shows a flow diagram illustrating example operations for wireless communication supporting an enhanced synchronization mode, according to some implementations. [Figure 12]1 shows a flow diagram illustrating example operations for wireless communication supporting an enhanced synchronization mode, according to some implementations. [Figure 13] 1 shows a flow diagram illustrating example operations for wireless communication supporting an enhanced synchronization mode, according to some implementations. [Figure 14] 1 shows a flow diagram illustrating example operations for wireless communication supporting an enhanced synchronization mode, according to some implementations. [Figure 15] 1 shows a flow diagram illustrating example operations for wireless communication supporting an enhanced synchronization mode, according to some implementations. [Figure 16] 1 shows a flow diagram illustrating example operations for wireless communication supporting an enhanced synchronization mode, according to some implementations. [Figure 17] 1 shows a flow diagram illustrating example operations for wireless communication supporting an enhanced synchronization mode, according to some implementations. [Figure 18] 1 shows a flow diagram illustrating example operations for wireless communication supporting an enhanced synchronization mode, according to some implementations. [Figure 19]

[0040] 1 shows a flow diagram illustrating example operations for wireless communication supporting an extended synchronization mode, according to certain other implementations. [Figure 20] 1 shows a flow diagram illustrating example operations for wireless communication supporting an extended synchronization mode, according to certain other implementations. [Figure 21]

[0041] 1 illustrates a block diagram of an exemplary wireless communication device. [Figure 22]

[0042] 1 illustrates a block diagram of another example wireless communication device.

[0024]

[0043] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025]

[0044] The following description is directed to some specific implementations for the purpose of describing the innovative aspects of the present disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in many different ways. The described implementations can be implemented in any device, system, or network capable of transmitting and receiving radio frequency (RF) signals according to one or more of the Long Term Evolution (LTE), 3G, 4G, or 5G (New Radio (NR)) standards promulgated by the 3rd Generation Partnership Project (3GPP), the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, the IEEE 802.15 standard, or the Bluetooth® standard defined by the Bluetooth Special Interest Group (SIG), among others. The described implementations may be implemented in any device, system, or network 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 may also be implemented using other wireless communications protocols or RF signals suitable for use in one or more of a wireless wide area network (WWAN), a wireless personal area network (WPAN), a wireless local area network (WLAN), or an internet of things (IOT) network.

[0026]

[0045] The IEEE 802.11be amendment of the IEEE 802.11 standard describes a restricted target wake time (r-TWT) service period (SP) that may be allocated for latency-sensitive traffic. As used herein, the term "non-legacy STA" refers to any wireless station (STA) that supports the IEEE 802.11be amendment or a future generation of the IEEE 802.11 standard, while the term "low latency STA" refers to any non-legacy STA that has latency-sensitive traffic to transmit or receive. In contrast, the term "legacy STA" may refer to any STA that supports only IEEE 802.11ax or an earlier generation of the IEEE 802.11 standard. Non-legacy STAs that support r-TWT operation and acquire transmit opportunities (TXOPs) outside of an r-TWT SP must terminate their respective TXOPs prior to the initiation of any r-TWT SP of which they are not a member. Therefore, r-TWT SP can provide more predictable latency, reduced worst-case latency, or reduced jitter to latency-sensitive traffic with higher reliability.

[0027]

[0046] Aspects of the present disclosure recognize that benefits of r-TWT operation may depend on the ability of STAs operating on a communication link to obtain accurate timing information of the AP responsible for scheduling r-TWT SPs on the communication link. For example, to avoid accessing a communication link during an r-TWT SP associated with a given communication link, non-member STAs should be configured with information indicating (with relative accuracy) the start time of the r-TWT SP. According to existing versions of the IEEE 802.11 standard, the start time of an r-TWT SP is represented as an integer value associated with a Timing Synchronization Function (TSF) timer of the AP (or BSS) that schedules the r-TWT SP. The AP broadcasts a beacon frame that carries the current value of the TSF timer based on the scheduled target beacon transmission times (TBTTs). STAs (and other APs) that receive the beacon frame can use the current TSF value to synchronize their respective local TSF timers.

[0028]

[0047] Imperfections in the clocks used by the AP and the AP's associated STAs (and other APs) to implement their respective TSF timers of the associated STAs may lead to clock drift between the AP and the associated STAs. The TSF offset between the AP and the AP's associated STAs resulting from the clock drift may affect the accuracy with which the associated STAs estimate the start time of the r-TWT SP on the communication link. The IEEE 802.11 standard specifies a beacon interval of 185,234,501 microseconds (μs) and allows a maximum clock drift between the AP and the AP's associated STAs to be ±100 parts-per million (ppm). Thus, the clock drift between the AP and the AP's associated STAs may be on the order of ±20 μs per beacon interval. STAs in Power Save (PS) mode may stay asleep during multiple beacon intervals and therefore may not listen for beacon frames every TBTT. For example, a STA in PS mode associated with Delivery Traffic Indication Map (DTIM)=4 will wake up to listen for beacon frames every 4th TBTT and will therefore miss three consecutive beacon frame transmissions during each DTIM period. As a result, the clock drift between a STA in PS mode with DTIM=4 and its associated AP will be ±4 per DTIM period. * It could be around 20μs=80μs.

[0029]

[0048] Some wireless devices may be capable of multi-link operation (MLO). MLO-enabled devices may be referred to as multi-link devices (MLDs). For example, an access point (AP) MLD may include multiple APs configured to communicate with a non-AP MLD (also referred to as a "STA MLD") over multiple respective communication links. Similarly, a non-AP MLD may include multiple STAs each configured to communicate over a respective one of multiple communication links associated with the AP MLD. Some non-AP MLDs may communicate with the AP MLD in parallel over each of the communication links, e.g., according to a multi-link multi-radio (MLMR) simultaneous transmit and receive (STR) or MLMR non-STR (NSTR) mode of operation. Other non-AP MLDs may communicate with the AP MLD over only one of the communication links at any given time, e.g., according to a multi-link single-radio (MLSR) or enhanced MLSR (EMLSR) mode of operation.

[0030]

[0049] When APs included in or associated with an AP MLD use different clocks for their respective TSF timers, clock drift between the respective clocks may lead to TSF offsets between APs in the AP MLD. The IEEE 802.11 standard allows a maximum clock drift between APs in the AP MLD of ±30 μs. Thus, for a STA in PS mode with DTIM=4 and associated with the first AP in the AP MLD, the clock drift between the STA and other APs in the AP MLD may be on the order of 30 μs+80 μs=±110 μs. Thus, when a STA relies on beacon frames communicated at beacon intervals for synchronization (especially when one or more beacons are skipped), the clock drift between the STA and other APs in the AP MLD may exceed acceptable levels. Therefore, to ensure that the TSF offset between a STA and its associated AP (or each AP in the AP MLD) does not allow the STA to inadvertently continue to hold a TXOP after the start time of the r-TWT SP or inadvertently access the communication link just before the start time of the r-TWT SP due to the TSF offset, it is necessary to maintain tighter synchronization between the STA and its associated AP, and more particularly, between the STA and each of the APs in the AP MLD.

[0031]

[0050] Implementations described herein provide an extended synchronization mode that allows synchronization messages to be communicated between an AP and a STA more frequently than a TBTT associated with a communication link. More specifically, a device may transmit an indication of an extended synchronization mode to a STA on a first communication link associated with a first AP device. The device may then transmit a plurality of synchronization frames on the first communication link during the extended synchronization mode more frequently than a TBTT associated with the first communication link, each of the plurality of synchronization frames indicating a TSF offset between the first AP and the second AP of the device. In this manner, the STA may be able to maintain closer synchronization with the AP compared to relying on synchronization on the TBTT to ensure that the STA terminates any TXOPs obtained outside of the r-TWT SP prior to the start of the r-TWT SP on the communication link (e.g., to help increase occurrence) and / or to ensure that the STA does not attempt to obtain access to the communication link immediately prior to the start of the r-TWT SP on the communication link. In this manner, the extended synchronous mode may enable r-TWT SP operation to provide more predictable latency, reduced worst-case latency, or reduced jitter to latency-sensitive traffic with greater reliability.

[0032]

[0051] Implementations of the subject matter described in this disclosure may be used to synchronize timing between STAs and APs in a manner that may prevent STAs operating on a communication link from inadvertently interfering with one or more r-TWT SPs scheduled on the communication link. Specifically, in various implementations, a device including a first AP may establish an extended synchronization mode in which participating STAs receive timing information of one or more associated APs or nearby APs with sufficient periodicity to ensure that a TSF offset between the STAs and the AP does not exceed a value that may allow the STAs to inadvertently access or occupy the shared wireless medium during r-TWT SPs scheduled on the shared wireless medium. For example, in some implementations, the device may transmit an indication of the extended synchronization mode to one or more STAs associated with the device on a first communication link associated with the device's first AP. In some cases, the indication may be in response to a presence of latency-sensitive traffic on the first communication link. In some other cases, the indication may be in response to a request from one or more STAs. In some aspects, the indication may also indicate a start time of the extended synchronization mode. In other aspects, the indication may also indicate whether participation in the enhanced synchronous mode is mandatory or voluntary for each of the one or more STAs.

[0033]

[0052] In some cases, the device may be an AP multi-link device (MLD) including a first AP and a second AP. The first AP may be associated with a first communication link, and the second AP may be associated with a second communication link occupying a different frequency band than the first communication link. For example, the first communication link may be a wireless channel in one of the 2.4 GHz frequency band, the 5 GHz frequency band, or the 6 GHz frequency band, and the second communication link may be a wireless channel in another one of the 2.4 GHz frequency band, the 5 GHz frequency band, or the 6 GHz frequency band.

[0034]

[0053] The device may transmit a plurality of synchronization frames on the first communication link during the extended synchronization mode more frequently than a TBTT associated with the first communication link. Each of the synchronization frames may indicate a TSF value of the first AP and a TSF offset between the first AP and the second AP of the device. The frequency at which the synchronization frames are transmitted on the first communication link may be associated with a level of timing accuracy that prevents participating STAs from occupying or accessing the first communication link during one or more r-TWT SPs scheduled on the first communication link. For example, in some instances, the synchronization frames may be transmitted at intervals of about 20 μs (although other suitable intervals may be used). STAs participating in the extended synchronization mode may use the TSF information indicated in the synchronization frames to synchronize their respective local TSF timers with the TSF timers of the first AP and the second AP of the device, for example, without receiving a beacon frame from the second AP. In some implementations, the extended synchronization mode may be established with one or more TWT SPs or r-TWT SPs on the first communication link. In some aspects, a device may reject association requests from STAs that do not support the extended synchronization mode during a time period starting prior to the start time of the extended synchronization mode and ending at the end of the extended synchronization mode.

[0035]

[0054] Particular implementations of the subject matter described in this disclosure may be implemented to achieve one or more of the following potential advantages: By synchronizing a STA's TSF timer with the respective TSF timers of the first and second APs of a device more frequently than the TBTTs of the first and second APs, aspects of the present disclosure may reduce the TSF offset between the STA and each of the first and second APs, for example, compared to a STA that relies on beacon frame transmissions to obtain the AP's TSF information. Additionally, by indicating the TSF offset between the first and second APs of a device in a synchronization frame, aspects of the present disclosure may enable STAs operating on a first communication link to synchronize their respective TSF timers with the TSF timer of the second AP without receiving a beacon frame broadcast by the second AP on the second communication link. In this manner, a single-radio device, such as an MLSR device or an EMLSR device, can synchronize its TSF timer with the respective TSF timers of both the device's first AP and second AP without switching between a first communication link and a second communication link to receive beacon frame transmissions from each of the device's first AP and second AP.

[0036]

[0055] Moreover, by participating in the extended synchronization mode disclosed herein, the STAs may be able to maintain the TSF offsets associated with the first and second APs of the device at or below a value associated with a level of timing accuracy to avoid inadvertently occupying or attempting to access the first communication link during one or more TWT or r-TWT SPs scheduled on the first communication link. Specifically, the improved timing synchronization achieved by using the extended synchronization mode disclosed herein may ensure that participating STAs terminate TXOPs obtained outside of an r-TWT SP prior to the start of an r-TWT SP of which they are not a member. In addition, the improved timing synchronization provided by the extended synchronization mode disclosed herein may ensure that participating STAs do not perform channel access operations prior to the start time of the r-TWT SP that may result in TXOPs that overlap with and therefore interfere with the r-TWT SP. In this manner, the enhanced synchronous mode disclosed herein may enable an r-TWT SP to provide more predictable latency, reduced worst-case latency, or reduced jitter to latency-sensitive traffic with greater reliability.

[0037]

[0056] FIG. 1 illustrates a block diagram of an exemplary wireless communication network 100. According to some aspects, the wireless communication network 100 may be an example of a wireless local area network (WLAN), such as a Wi-Fi network (also referred to below as WLAN 100). For example, the WLAN 100 may be a network that implements at least one of the IEEE 802.11 family of standards (such as those defined by the IEEE 802.11-2016 specification or amendments thereto, including but not limited to 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be). The WLAN 100 may include multiple wireless communication devices, such as an access point (AP) 102 and multiple stations (STAs) 104. Although only one AP 102 is shown, the WLAN 100 may also include multiple APs 102.

[0038]

[0057] Each of the STAs 104 may also be referred to as a mobile station (MS), mobile device, mobile handset, wireless handset, access terminal (AT), user equipment (UE), subscriber station (SS), or subscriber unit, among other possibilities. The STAs 104 may represent a variety of devices, such as a mobile phone, a personal digital assistant (PDA), other handheld device, a netbook, a notebook computer, a tablet computer, a laptop, a display device (e.g., a TV, a computer monitor, a navigation system, among others), a music device or other audio or stereo device, a remote control device ("remote"), a printer, a kitchen appliance or other household appliance, a key fob (e.g., for a passive keyless entry and start (PKES) system), among other possibilities.

[0039]

[0058] A single AP 102 and the associated set of STAs 104 may be referred to as a basic service set (BSS) managed by each AP 102. FIG. 1 additionally illustrates an example coverage area 106 of the AP 102, which may represent a basic service area (BSA) of the WLAN 100. The BSS may be identified to users by a service set identifier (SSID) and to other devices by a basic service set identifier (BSSID), which may be the medium access control (MAC) address of the AP 102. The AP 102 periodically broadcasts a beacon frame ("beacon") containing the BSSID to allow any STAs 104 within wireless range of the AP 102 to "associate" or reassociate with the AP 102 to establish a respective communication link 108 with the AP 102 (hereinafter also referred to as a "Wi-Fi link") or to maintain a communication link 108 with the AP 102. For example, the beacon may include an identification of a primary channel used by each AP 102, as well as a timing synchronization function to establish or maintain timing synchronization with the AP 102. The APs 102 may provide access to external networks to various STAs 104 in the WLAN via respective communication links 108.

[0040]

[0059] To establish a communication link 108 with an AP 102, each of the STAs 104 is configured to perform passive or active scanning operations ("scans") on frequency channels in one or more frequency bands (e.g., the 2.4 GHz, 5.0 GHz, 6.0 GHz, or 60 GHz bands). To perform passive scanning, the STAs 104 listen for beacons transmitted by the respective APs 102 at periodic time intervals called target beacon transmission times (TBTTs) (measured in time units (TUs), where one TU may equal 1024 microseconds (μs)). To perform active scanning, the STAs 104 generate probe requests and transmit them continuously on each channel to be scanned, and listen for probe responses from the APs 102. Each STA 104 may be configured to identify or select an AP 102 to associate with based on scan information obtained through passive or active scanning, and perform authentication and association operations to establish a communication link 108 with the selected AP 102. Upon completing the association operation, the AP 102 assigns an association identifier (AID) to the STA 104, which the AP 102 uses to track the STA 104.

[0041]

[0060] As a result of the increasing ubiquity of wireless networks, a STA 104 may have the opportunity to select one of many BSSs within range of the STA, or among multiple APs 102 that together form an extended service set (ESS) that includes multiple connected BSSs. The extended network station associated with the WLAN 100 may be connected to a wired or wireless distribution system that may allow multiple APs 102 to be connected in such an ESS. Thus, the STA 104 may be covered by more than one AP 102 and may associate with different APs 102 at different times for different transmissions. Additionally, after association with an AP 102, the STA 104 may also be configured to periodically scan the vicinity of the STA to find a more suitable AP 102 to associate with. For example, a STA 104 moving with respect to its associated AP 102 may perform a "roaming" scan to find another AP 102 with more desirable network characteristics, such as a greater received signal strength indicator (RSSI) or reduced traffic load.

[0042]

[0061] In some cases, the STAs 104 may form a network without involving the AP 102 or other devices other than the STAs 104 themselves. One example of such a network is an ad-hoc network (or wireless ad-hoc network). An ad-hoc network may alternatively be referred to as a mesh network or a peer-to-peer (P2P) network. In some cases, the ad-hoc network may be implemented within a larger wireless network, such as the WLAN 100. In such an implementation, the STAs 104 may be able to communicate with each other via the AP 102 using the communication link 108, but the STAs 104 may also communicate with each other directly via a direct communication link 110. Additionally, two STAs 104 may communicate via the direct communication link 110 regardless of whether both STAs 104 are associated with and served by the same AP 102. In such an ad-hoc system, one or more of the STAs 104 may assume the role filled by the AP 102 in the BSS. Such STAs 104 may be referred to as group owners (GOs) and may coordinate transmissions within the ad-hoc network. Examples of direct communication links 110 include Wi-Fi direct connections, connections established by using Wi-Fi Tunneled Direct Link Setup (TDLS) links, and other P2P group connections.

[0043]

[0062] The AP 102 and the STAs 104 may function and communicate (via respective communication links 108) in accordance with the IEEE 802.11 family of standards (such as those defined by the IEEE 802.11-2016 specification or amendments thereto, including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be). These standards define WLAN radio and baseband protocols for the PHY layer and medium access control (MAC) layer. The AP 102 and the STAs 104 transmit and receive wireless communications (hereinafter also referred to as "Wi-Fi communications") between each other in the form of physical layer convergence protocol (PLCP) protocol data units (PPDUs). The AP 102 and the STAs 104 in the WLAN 100 may transmit PPDUs over an unlicensed spectrum, which may be a portion of a spectrum including frequency bands traditionally used by Wi-Fi technology, such as the 2.4 GHz band, the 5.0 GHz band, the 60 GHz band, the 3.6 GHz band, and the 900 MHz band. Some implementations of the AP 102 and the STAs 104 described herein may also communicate in other frequency bands, such as the 6.0 GHz band, which may support both licensed and unlicensed communications. The AP 102 and the STAs 104 may also be configured to communicate over other frequency bands, such as shared licensed frequency bands, in which multiple operators may have authorization to operate in the same or overlapping frequency bands.

[0044]

[0063] Each of the frequency bands may include multiple sub-bands or frequency channels. For example, PPDUs conforming to the IEEE 802.11n, 802.11ac, and 802.11ax standard revisions may be transmitted on the 2.4 GHz and 5.0 GHz bands, each of which is divided into multiple 20 MHz channels. Thus, these PPDUs are transmitted over physical channels with a minimum bandwidth of 20 MHz, although larger channels may be formed through channel bonding. For example, PPDUs may be transmitted over physical channels with bandwidths of 40 MHz, 80 MHz, 160, or 320 MHz by bonding together multiple 20 MHz channels.

[0045]

[0064] Each PPDU is a composite structure that includes a PHY preamble and a payload in the form of a PLCP service data unit (PSDU). Information provided in the preamble may be used by a receiving device to decode subsequent data in the PSDU. In cases where the PPDU is transmitted over bonded channels, the preamble field may be replicated 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 applications. The legacy preamble may also generally be used to maintain compatibility with legacy devices. The format, coding, and information provided therein of the non-legacy portion of the preamble is based on the particular IEEE 802.11 protocol that will be used to transmit the payload.

[0046]

[0065] 2A illustrates an exemplary protocol data unit (PDU) 200 usable for wireless communication between an AP 102 and one or more STAs 104. For example, the PDU 200 may be configured as a PPDU. As illustrated, the PDU 200 includes a PHY preamble 202 and a payload 204. For example, the preamble 202 may include a legacy portion that itself includes a legacy short training field (L-STF) 206, which may consist of two BPSK symbols, a legacy long training field (L-LTF) 208, which may consist of two BPSK symbols, and a legacy signal field (L-SIG) 210, which may consist of two BPSK symbols. The legacy portion of the preamble 202 may be configured in accordance with the IEEE 802.11a wireless communication protocol standard. The preamble 202 may also include a non-legacy portion that includes one or more non-legacy fields 212 that conform to an IEEE wireless communication protocol, such as, for example, an IEEE 802.11ac, 802.11ax, 802.11be, or later wireless communication protocol standard.

[0047]

[0066] The L-STF 206 generally enables the receiving device to perform automatic gain control (AGC) and coarse timing and frequency estimation. The L-LTF 208 generally enables the receiving device to perform fine timing and frequency estimation, and also enables the receiving device to perform an initial estimation of the wireless channel. The L-SIG 210 generally enables the receiving device to determine the duration of a PDU and use the determined duration to avoid transmitting at the beginning of the PDU. For example, the L-STF 206, the L-LTF 208, and the L-SIG 210 may be modulated according to a binary phase shift keying (BPSK) modulation scheme. The payload 204 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 suitable modulation scheme. The payload 204 may include a PSDU that includes a data field (DATA) 214, which may carry higher layer data, for example in the form of Medium Access Control (MAC) protocol data units (MPDUs) or aggregated MPDUs (A-MPDUs).

[0048]

[0067] 2B illustrates an example L-SIG 210 in the PDU 200 of FIG. 2A. The L-SIG 210 includes a data rate field 222, a reserved bit 224, a length field 226, a parity bit 228, and a tail field 230. The data rate field 222 indicates a data rate (note that the data rate indicated in the data rate field 222 may not be the actual data rate of the data carried in the payload 204). The length field 226 indicates the length of the packet, for example, in units of symbols or bytes. The parity bit 228 may be used to detect bit errors. The tail field 230 includes tail bits that may be used by a receiving device to terminate the operation of a decoder (e.g., a Viterbi decoder). The receiving device may use the data rate and length indicated in the data rate field 222 and the length field 226 to determine the duration of the packet, for example, in units of microseconds (μs) or other time units.

[0049]

[0068] 3A illustrates another exemplary PDU 300 usable for wireless communication between an AP and one or more STAs. The PDU 300 may be used for SU, OFDMA, or MU-MIMO transmissions. The PDU 300 may be formatted as a High Efficiency (HE) WLAN PPDU in accordance with the IEEE 802.11ax amendment to the IEEE 802.11 wireless communication protocol standard. The PDU 300 includes a PHY preamble including a legacy portion 302 and a non-legacy portion 304. The PDU 300 may further include a payload 306 following the preamble, for example in the form of a PSDU including a data field 324.

[0050]

[0069] The legacy portion 302 of the preamble includes an L-STF 308, an L-LTF 310, and an L-SIG 312. The non-legacy portion 304 includes a repetition of L-SIG (RL-SIG) 314, a first HE signal field (HE-SIG-A) 316, an HE short training field (HE-STF) 320, and one or more HE long training fields (or symbols) (HE long training fields (HE-LTFs) 322). In the case of OFDMA or MU-MIMO communications, the non-legacy portion 304 further includes a second HE signal field (HE-SIG-B) 318 that is coded separately from the HE-SIG-A 316. In cases involving the use of bonded channels, such as the L-STF 308, L-LTF 310, and L-SIG 312, the information in the RL-SIG 314 and HE-SIG-A 316 may be duplicated and transmitted in each of the 20 MHz component channels. In contrast, the content of the HE-SIG-B 318 may be unique to each 20 MHz channel and the particular STA 104 targeted.

[0051]

[0070] The RL-SIG 314 may indicate to the HE compatible STAs 104 that the PDU 300 is an HE PPDU. The AP 102 may use the HE-SIG-A 316 to identify the STAs 104 and inform the STAs 104 that the AP has scheduled UL or DL ​​resources for the STAs 104. For example, the HE-SIG-A 316 may include a resource allocation subfield indicating resource allocations for the identified STAs 104. The HE-SIG-A 316 may be decoded by each HE compatible STA 104 served by the AP 102. In the case of a MU transmission, the HE-SIG-A 316 further includes information usable by each identified STA 104 to decode an associated HE-SIG-B 318. For example, the HE-SIG-A 316 may indicate frame formats including the location and length of the HE-SIG-B 318, available channel bandwidth, and modulation and coding schemes (MCSs), among other examples. The HE-SIG-A 316 may also include HE WLAN signaling information usable by STAs 104 other than the identified STA 104.

[0052]

[0071] The HE-SIG-B 318 may carry STA-specific scheduling information, such as, for example, a STA-specific (or "user-specific") MCS value and STA-specific RU allocation information. In the context of DL MU-OFDMA, such information allows each STA 104 to identify and decode corresponding resource units (RUs) in the associated data field 324. Each HE-SIG-B 318 includes a common field and at least one STA-specific field. The common field may indicate RU allocations for multiple STAs 104, including RU allocations in the frequency domain, which RUs are allocated for MU-MIMO transmissions, which RUs correspond to MU-OFDMA transmissions, and the number of users in the allocation, among other examples. The common field may be encoded with common bits, CRC bits, and tail bits. The user-specific fields are assigned to a particular STA 104 and may be used to schedule specific RUs and indicate the scheduling to other WLAN devices. Each user-specific field may include multiple user block fields. Each user block field may include two user fields containing information for two respective STAs to decode the respective RU payloads in the data field 324.

[0053]

[0072] 3B illustrates another exemplary PPDU 350 usable for wireless communication between an AP and one or more STAs. The PDU 350 may be used for SU, OFDMA, or MU-MIMO transmissions. The PDU 350 may be formatted as an Extreme High Throughput (EHT) WLAN PPDU according to the IEEE 802.11be amendment to the IEEE 802.11 wireless communication protocol standard, or as a PPDU compliant with any later (post-EHT) version of a new wireless communication protocol that complies with a future IEEE 802.11 wireless communication protocol standard or other wireless communication standard. The PDU 350 includes a PHY preamble that includes a legacy portion 352 and a non-legacy portion 354. The PDU 350 may further include a PHY payload 356 following the preamble, for example in the form of a PSDU that includes a data field 376.

[0054]

[0073] The legacy portion 352 of the preamble includes an L-STF 358, an L-LTF 360, and an L-SIG 362. The non-legacy portion 354 of the preamble includes an RL-SIG 364 and a number of wireless communication protocol version dependent signal fields following the RL-SIG 364. For example, the non-legacy portion 354 may include a generic signal field 366 (referred to herein as “U-SIG 366”) and an EHT signal field 368 (referred to herein as “EHT-SIG 368”). One or both of the U-SIG 366 and the EHT-SIG 368 may be configured as and carry version dependent information for other wireless communication protocol versions beyond EHT. The non-legacy portion 354 further includes an additional short training field 372 (referred to herein as “EHT-STF 372” although it may be configured as other wireless communication protocol versions beyond EHT and carry version dependent information therefor) and one or more additional long training fields 374 (referred to herein as “EHT-LTF 374” although it may be configured as other wireless communication protocol versions beyond EHT and carry version dependent information therefor). In cases involving the use of bonded channels, such as the L-STF 358, L-LTF 360, and L-SIG 362, the information in the U-SIG 366 and EHT-SIG 368 may be duplicated and transmitted in each of the 20 MHz component channels. In some implementations, the EHT-SIG 368 may additionally or alternatively carry information in one or more 20 MHz non-primary channels that is different from the information carried in the 20 MHz primary channel.

[0055]

[0074] The EHT-SIG 368 may include one or more jointly coded symbols and may be coded in a different block than the block in which the U-SIG 366 is coded. The EHT-SIG 368 may be used by the AP to identify the STAs 104 and inform the STAs 104 that the AP has scheduled UL or DL ​​resources for them. The EHT-SIG 368 may be decoded by each compatible STA 104 served by the AP 102. The EHT-SIG 368 may be used by a receiving device to interpret bits in the data field 376. For example, the EHT-SIG 368 may include RU allocation information, spatial stream configuration information, and per-user signaling information such as MCS, among other examples. The EHT-SIG 368 may further include a cyclic redundancy check (CRC) (e.g., 4 bits) and a tail (e.g., 6 bits) that may be used for a binary convolutional code (BCC). In some implementations, the EHT-SIG 368 may include one or more code blocks, each including a CRC and a tail. In some aspects, each of the code blocks may be coded separately.

[0056]

[0075] The EHT-SIG 368 may carry STA-specific scheduling information, such as, for example, a user-specific MCS value and user-specific RU allocation information. The EHT-SIG 368 may be used by a receiving device to interpret bits in the data field 376. In the context of DL MU-OFDMA, such information allows each STA 104 to identify and decode the corresponding RU in the associated data field 376. Each EHT-SIG 368 may include a common field and at least one user-specific field. The common field may indicate RU distribution for multiple STAs 104, indicate RU allocation in the frequency domain, indicate which RUs are allocated for MU-MIMO transmissions, which RUs correspond to MU-OFDMA transmissions, and the number of users in the allocation, among other examples. The common field may be encoded with common bits, CRC bits, and tail bits. The user-specific fields are assigned to a particular STA 104 and may be used to schedule specific RUs and indicate the scheduling to other WLAN devices. Each user-specific field may include multiple user block fields. Each user block field may, for example, include two user fields containing information for two respective STAs to decode the respective RU payloads.

[0057]

[0076] The presence of RL-SIG 364 and U-SIG 366 may indicate to EHT or later version compliant STAs 104 that the PPDU 350 is an EHT PPDU, or a PPDU that complies with any later (post-EHT) version of a new wireless communications protocol that complies with a future IEEE 802.11 wireless communications protocol standard. For example, U-SIG 366 may be used by a receiving device to interpret bits in one or more of EHT-SIG 368 or data field 376.

[0058]

[0077] 4 shows a block diagram of an example wireless communication device 400. In some implementations, the wireless communication device 400 may be an example of a device for use in a STA, such as one of the STAs 104 described above with reference to FIG. 1. In some implementations, the wireless communication device 400 may be an example of a device for use in an AP, such as the AP 102 described above with reference to FIG. 1. The wireless communication device 400 is capable of transmitting (or outputting for transmission) and receiving wireless communications (e.g., in the form of wireless packets). For example, the wireless communication device 400 may 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) that conform to IEEE 802.11 standards, such as those defined by the IEEE 802.11-2016 specification or amendments thereof, including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be.

[0059]

[0078] The wireless communication device 400 may be or include a chip, system on chip (SoC), chipset, package, or device including one or more modems 402, e.g., a Wi-Fi (IEEE 802.11 compliant) modem. In some implementations, the one or more modems 402 (collectively "modems 402") additionally include a WWAN modem (e.g., a 3GPP 4G LTE or 5G compliant modem). In some implementations, the wireless communication device 400 also includes one or more radios 404 (collectively "radios 404"). In some implementations, the wireless communication device 400 further includes one or more processors, processing blocks, or processing elements (collectively "processor 406") and one or more memory blocks or elements (collectively "memory 408").

[0060]

[0079] The modem 402 may include an intelligent hardware block or device, such as, for example, an application-specific integrated circuit (ASIC), among other possibilities. The modem 402 is configured to implement a PHY layer. For example, the modem 402 is configured to modulate packets and output modulated packets to the radio 404 for transmission over a wireless medium. The modem 402 is also configured to obtain modulated packets received by the radio 404 and demodulate the packets to provide demodulated packets. In addition to a modulator and demodulator, the modem 402 may further include digital signal processing (DSP) circuitry, an automatic gain control (AGC), a coder, a decoder, a multiplexer, and a demultiplexer. For example, while in a transmit mode, data obtained from the processor 406 is provided to a coder, which encodes the data to provide coded bits. The coded bits are then mapped (using a selected MCS) to points in a modulation constellation to provide modulated symbols. The modulated symbols are then encoded into N SS number of spatial streams or N STS The modulated symbols in each spatial or space-time stream may then be multiplexed and transformed via an inverse fast Fourier transform (IFFT) block, followed by providing to a DSP circuit for Tx windowing and filtering. The digital signal may then be provided to a digital-to-analog converter (DAC). The resulting analog signal may then be provided to a frequency up-converter and radio 404. In an implementation with beamforming, the modulated symbols in each spatial stream are precoded via a steering matrix before being provided to the IFFT block.

[0061]

[0080] While in the receive mode, the digital signal received from the radio 404 is provided to the DSP circuit, which is configured to acquire the received signal, for example, by detecting the presence of a signal and estimating an initial timing and frequency offset. The DSP circuit is further configured to digitally condition the digital signal, for example, using channel (narrowband) filtering, analog impairment adjustment (such as to correct I / Q imbalance), and applying a digital gain to obtain a narrowband signal. The output of the DSP circuit may then be provided to an AGC, which is configured to use information extracted from the digital signal in one or more received training fields, for example, to determine an appropriate gain. The output of the DSP circuit is also coupled to a demodulator, which is configured to extract modulated symbols from the signal and calculate, for example, logarithm likelihood ratios (LLRs) for each bit position of each subcarrier in each spatial stream. The demodulator is coupled to a decoder, which may be configured to process the LLRs to provide decoded bits. The decoded bits from all of the spatial streams are then provided to a demultiplexer for demultiplexing. The demultiplexed bits may then be descrambled and provided to the MAC layer (processor 406) for processing, evaluation, or interpretation.

[0062]

[0081] The radio 404 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 transmitter and RF receiver may each include various DSP circuits, including at least one power amplifier (PA) and at least one low-noise amplifier (LNA). The RF transmitter and RF receiver may then be coupled to one or more antennas. For example, in some implementations, the wireless communication device 400 may include or be coupled to multiple transmit antennas (each with a corresponding transmit chain) and multiple receive antennas (each with a corresponding receive chain). Symbols output from the modem 402 are provided to the radio 404, which then transmits the symbols via the coupled antenna. Similarly, symbols received via the antennas are obtained by the radio 404, which then provides the symbols to the modem 402.

[0063]

[0082] The processor 406 may include an intelligent hardware block or device, such as, for example, a processing core, processing block, central processing unit (CPU), microprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), programmable logic device (PLD) such as 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 406 processes information received via the radio 404 and modem 402, and processes information to be output via the modem 402 and radio 404 for transmission over a wireless medium. For example, the processor 406 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 frame coding and decoding, spatial multiplexing, space-time block coding (STBC), beamforming, and OFDMA resource allocation, among other operations or techniques. In some implementations, the processor 406 can control the modem 402 to cause the modem to perform various operations described above.

[0064]

[0083] The memory 408 may include a tangible storage medium, such as a random-access memory (RAM) or a read-only memory (ROM), or a combination thereof. The memory 408 may also store non-transitory processor or computer executable software (SW) code that includes instructions that, when executed by the processor 406, cause the processor to perform various operations described herein for wireless communication, including generating, transmitting, receiving, and interpreting MPDUs, frames, or packets. For example, various functions of the components disclosed herein, or various blocks or steps of the methods, operations, processes, or algorithms disclosed herein, may be implemented as one or more modules of one or more computer programs.

[0065]

[0084] FIG. 5A illustrates a block diagram of an exemplary AP 502. For example, the AP 502 may be an exemplary implementation of the AP 102 described with reference to FIG. 1. The AP 502 includes a wireless communication device (WCD) 510. For example, the wireless communication device 510 may be an exemplary implementation of the wireless communication device 400 described with reference to FIG. 4. The AP 502 also includes multiple antennas 520 coupled to the wireless communication device 510 for transmitting and receiving wireless communications. In some implementations, the AP 502 additionally includes an application processor 530 coupled to the wireless communication device 510 and a memory 540 coupled to the application processor 530. The AP 502 further includes at least one external network interface 550 that enables the AP 502 to communicate with a core network or a backhaul network to provide access to external networks, including the Internet. For example, the external network interface 550 may include one or both of a wired (e.g., Ethernet) network interface and a wireless network interface (such as a WWAN interface). Some of the above-mentioned components may communicate directly or indirectly with some of the other components via at least one bus. The AP 502 further includes a housing that contains the wireless communication device 510, the application processor 530, the memory 540, and at least a portion of the antenna 520 and an external network interface 550.

[0066]

[0085] 5B illustrates a block diagram of an exemplary STA 504. For example, the STA 504 may be an exemplary implementation of the STA 104 described with reference to FIG. 1. The STA 504 includes a wireless communication device 515. For example, the wireless communication device 515 may be an exemplary implementation of the wireless communication device 400 described with reference to FIG. 4. The STA 504 also includes one or more antennas 525 coupled with the wireless communication device 515 for transmitting and receiving wireless communications. The STA 504 additionally includes an application processor 535 coupled with the wireless communication device 515 and a memory 545 coupled with the application processor 535. In some implementations, the STA 504 further includes a user interface (UI) 555 (such as a touch screen or keypad) and a display 565, which may be integrated with the UI 555 to form a touch screen display. In some implementations, the STA 504 may further include one or more sensors 575, such as, for example, one or more inertial sensors, accelerometers, temperature sensors, pressure sensors, or altitude sensors. Some of the above-mentioned components may communicate directly or indirectly with other components via at least one bus. The STA 504 further includes a housing that contains the wireless communication device 515, the application processor 535, the memory 545, and at least a portion of the antenna 525, the UI 555, and the display 565.

[0067]

[0086] Figure 6 shows an example communication system 600 including an AP MLD 610 and a non-AP MLD 620. In some implementations, the AP MLD 610 may be an example of any of the APs 102 of Figure 1, the wireless communication device 400 of Figure 4, or the AP 502 of Figure 5. The non-AP MLD 720 may be an example of any of the STAs 104 of Figure 1, the wireless communication device 400 of Figure 4, or the STA 504 of Figure 5.

[0068]

[0087] The AP MLD 610 includes multiple APs 612-616 associated with (or operating on) the communication links 602-606, respectively. In the example of FIG. 6, the AP MLD 610 is shown to include only three APs. However, in some implementations, the AP MLD 610 may include fewer or more APs than those illustrated in FIG. 6. Although the APs 612-616 may share a common association context (through the AP MLD 610), each of the APs 612-616 may establish a respective BSS on the AP's associated communication links. The APs 612-616 may also establish their respective communication links 602-606 on different frequency bands. For example, the AP 612 may operate on the 2.4 GHz frequency band, the AP 614 may operate on the 5 GHz frequency band, and the AP 616 may operate on the 6 GHz frequency band.

[0069]

[0088] The non-AP MLD 620 includes multiple STAs 622-626 that may be configured to communicate over the communication links 602-606, respectively. Thus, the STA 622 may operate on the 2.4 GHz frequency band, the STA 624 may operate on the 5 GHz frequency band, and the STA 626 may operate on the 6 GHz frequency band. In the example of FIG. 6, the non-AP MLD 620 is shown to include only three STAs. However, in some implementations, the non-AP MLD 620 may include fewer or more STAs than those illustrated in FIG. 6. The IEEE 802.11be amendment of the IEEE 802.11 standard defines several modes in which the non-AP MLD may operate. The various operating modes depend on the number of wireless radios associated with the non-AP MLD and the ability of the non-AP MLD to communicate (e.g., by transmitting or receiving) in parallel over multiple communication links.

[0070]

[0089] In some implementations, the non-AP MLD 620 may include a single radio or may otherwise be capable of communicating on only one link at a time. In such implementations, the non-AP MLD 620 may operate in a multi-link single-radio (MLSR) mode or an enhanced MLSR (EMLSR) mode. A non-AP MLD operating in an EMLSR mode may listen in parallel for certain types of communications (such as buffer status report poll (BSRP) frames or multi-user request-to-send (MU-RTS) frames) on multiple communications links, but may only transmit or receive on one communications link at any given time. For example, the STAs 622 and 624 may listen in parallel on their respective links 602 and 604 during a listen interval. However, if STA 622 detects a BSRP frame on link 602, non-AP MLD 620 then tunes each of the non-AP MLD's antennas (including the antenna used by STA 624 during the listen interval) to operate on link 602. In contrast, a non-AP MLD operating in MLSR mode can only listen to and transmit or receive on one communication link at any given time. For example, STA 622 must be in power save mode whenever STA 624 is active.

[0071]

[0090] In some other implementations, the non-AP MLD 620 may include multiple radios and may be capable of simultaneous communication on each of the links. In such implementations, the non-AP MLD 620 may operate in a multi-link multi-radio (MLMR) simultaneous transmit / receive (STR) mode or a multi-link multi-radio non-STR (NSTR) mode. A non-AP MLD operating in an MLMR STR mode may transmit and receive simultaneously (or in parallel) on multiple communication links. For example, STA 622 may transmit or receive on link 602, while STA 624 transmits or receives in parallel on link 604. More specifically, such communication may be asynchronous. In other words, STA 622 may be transmitting on link 602, while STA 624 is receiving on link 604. In contrast, a non-AP MLD operating in an MLMR NSTR mode may transmit and receive simultaneously on multiple communication links only if such communication is synchronous. For example, STAs 624 and 626 can transmit in parallel on links 604 and 606 and can receive in parallel on links 604 and 606. However, STA 624 cannot be transmitting on link 604 while STA 626 is receiving on link 606.

[0072]

[0091] Furthermore, a non-AP MLD may include multiple radios, but may be capable of simultaneous communication on only a subset of links. In such implementations, the non-AP MLD 620 may operate in an enhanced MLMR (EMLMR) mode or a hybrid EMLSR mode. A non-AP MLD operating in EMLMR mode supports MLMR STR operation between a particular pair of communication links. For example, STAs 622 and 624 may communicate in parallel on their respective links 602 and 604 according to an MLMR STR operation mode.

[0073]

[0092] FIG. 7 shows a timing diagram 700 illustrating an example of wireless communication between devices belonging to a BSS. In the example of FIG. 7, the BSS may include multiple non-legacy STAs 702 and 704 supporting r-TWT operation. More specifically, STA 702 may be a low-latency STA that is a member of an r-TWT SP for a time period between times t3 and t8, while STA 704 may be a non-member STA. In some implementations, each of STAs 702 and 704 may be an example of any of STAs 104 of FIG. 1, wireless communication device 400 of FIG. 4, or STA 504 of FIG. 5B. Although only two non-legacy STAs 702 and 704 are shown in the example of FIG. 7, in an actual implementation, the BSS may include any number of legacy or non-legacy STAs.

[0074]

[0093] The non-member STA 704 attempts to access the shared wireless channel prior to the start of the r-TWT SP at time t3. More specifically, the non-member STA 704 detects that the channel is idle for a threshold duration from time t0 to t1 based on a channel sensing operation (e.g., clear channel assessment (CCA)), and further counts down a random backoff (RBO) duration from time t1 to t2 before attempting to acquire a TXOP. For example, the threshold duration (from time t0 to t1) may be an arbitration interframe spacing (AIFS) duration associated with a particular access category (AC) of data traffic. Thus, the RBO duration (from time t1 to t2) may be randomly selected from a range of RBOs spanning a contention window associated with the AC. At time t2, the non-member STA 704 detects that the wireless channel is still idle and proceeds to acquire a TXOP, for example, by starting transmission over the shared channel. 7, the desired TXOP may be longer than the remaining duration before the start of the r-TWT SP at time t3. However, because existing rules for r-TWT operation require non-member STAs to terminate their TXOPs by the start of the r-TWT SP, non-member STA 704 must shorten its TXOP between times t2 and t3.

[0075]

[0094] The low-latency STA 702 attempts to access the shared wireless channel at the beginning of the r-TWT SP. In the example of FIG. 7, the low-latency STA 702 detects the channel to be idle for the AIFS duration from time t3 to t4, and further counts down the RBO duration from time t4 to t6 before attempting to acquire a TXOP. As shown in FIG. 7, the non-member STA 704 also attempts to access the shared wireless channel at the beginning of the r-TWT SP. For example, the non-member STA 704 detects the channel to be idle for the AIFS duration from time t3 to t5, and further counts down the RBO duration beginning at time t5. In some implementations, the data traffic associated with the low-latency STA 702 may be assigned to a higher priority AC than the data traffic associated with the non-member STA 704. Thus, the AIFS or RBO duration associated with the low-latency STA 702 may be shorter than the AIFS or RBO duration associated with the non-member STA 704, respectively. As a result, the low latency STA 702 wins access to the wireless channel at time t6, eg, by initiating transmission over the shared channel, and acquires the TXOP.

[0076]

[0095] At time t6, the non-member STAs 704 detect that the wireless medium is busy and refrain from accessing the shared channel for the duration of the TXOP (from t6 to t8). After the TXOP ends, at time t8, the non-member STAs 704 may attempt to access the wireless channel again. In this manner, r-TWT operation may prioritize latency-sensitive traffic in the BSS, for example, by requiring non-member STAs to end their TXOP by the start of any r-TWT SP of which they are not members. Additionally, the AP (not shown for simplicity) may suppress all traffic from legacy STAs associated with the BSS by scheduling a quiet interval to overlap with at least a portion of the r-TWT SP (e.g., one or more time units (TUs) beginning at time t3). For example, the duration of the quiet interval may be indicated by one or more quiet elements included in a management frame (e.g., a beacon frame or a probe response frame) transmitted by the AP prior to the start of the r-TWT SP.

[0077]

[0096] As described, aspects of the present disclosure recognize that the benefits of r-TWT operation may depend on the ability of non-legacy STAs, such as STAs 702 and 704 of FIG. 7, to obtain accurate timing information of the AP responsible for scheduling the r-TWT SP on the communication link. Specifically, to avoid interference with the scheduled r-TWT SP on the communication link, the non-member STAs must know the start time of the r-TWT SP relatively accurately. However, because the start time of the r-TWT SP is expressed as an integer value based on the TSF timer of the AP that schedules the r-TWT SP on the communication link, a TSF offset between the non-member STA and the scheduling AP may cause the non-member STA to miscalculate the r-TWT SP start time and inadvertently occupy the communication link for at least a portion of the r-TWT SP.

[0078]

[0097] FIG. 8A shows a timing diagram 800A illustrating an example beacon frame transmission. The timing diagram 800A shows a first AP 810 operating on a first communication link (Link 1) and a second AP 820 operating on a second communication link (Link 2). The APs 810 and 820 may be examples of the AP 102 of FIG. 1, the wireless communication device 400 of FIG. 4, the AP 502 of FIG. 5A, or the AP MLD 610 of FIG. 6. In some implementations, the APs 810 and 820 may be part of or associated with an AP MLD configured to communicate on multiple different communication links. For example, although only two APs 810 and 820 are shown in FIG. 8A for simplicity, the AP MLD may include one or more other APs configured to operate on one or more other respective communication links. In some aspects, link 1 may be a wireless channel in one of the 2.4 GHz frequency band, the 5 GHz frequency band, or the 6 GHz frequency band, and link 2 may be a wireless channel in another one of the 2.4 GHz frequency band, the 5 GHz frequency band, or the 6 GHz frequency band.

[0079]

[0098] The AP810 broadcasts a plurality of first beacon frames B11-B31 at respective times TBTT(1)1-TBTT(3)1 on link 1, and the AP820 broadcasts a plurality of second beacon frames B12-B32 at respective times TBTT(1)2-TBTT(3)2 on link 2. Each of the first beacon frames B11-B31 broadcasted on link 1 may include a current TSF value of the AP810 and a TSF offset between the AP810 and the AP820, and each of the second beacon frames B12-B32 broadcasted on link 2 may include a current TSF value of the AP820 and a TSF offset between the AP820 and the AP810. In some cases, the TSF timer of AP810 may be used as a reference for the TSF offset between AP810 and AP820, and the beacon interval associated with AP810 (and thus the corresponding transmission times TBTT(1)1 to TBTT(3)1) may be used as a reference for the timing offset between AP810 and AP820.

[0080]

[0099] 8A example, AP 820 has a slower clock than AP 810 (or AP 810 has a faster clock than AP 820), which may cause a continuously increasing time offset between the beacon transmission times TBTT(1)1-TBTT(3)1 associated with AP 810 and the beacon transmission times TBTT(1)2-TBTT(3)2 associated with AP 820. For example, the transmission of a first beacon frame B11 on link 1 is aligned with the transmission of a first beacon frame B12 on link 2, but the transmission of a second beacon frame B21 on link 1 occurs before the transmission of a second beacon frame B22 on link 2 by a time period equal to Δt, the transmission of a third beacon frame B31 on link 1 occurs before the transmission of a third beacon frame B32 on link 2 by a time period equal to Δ2t, and so on. Thus, the beacon transmission times TBTT(1)1 through TBTT(3)1 associated with the AP 810 may occur earlier and earlier than the beacon transmission times TBTT(1)2 through TBTT(3)2 associated with the AP 820.

[0081]

[0100] FIG. 8B shows a timing diagram 800B illustrating an example wireless communication between devices. The timing diagram 800B includes the AP 820 of FIG. 8A and a STA 830. The STA 830 may be any suitable device, such as one or more of the STA 104 of FIG. 1, the wireless communication device 400 of FIG. 4, the STA 504 of FIG. 5B, or the non-AP MLD 620 of FIG. 6. In some implementations, the STA 830 may be part of a non-AP MLD configured to communicate on multiple different communication links. For example, although only one STA 830 is shown in FIG. 8B for simplicity, the non-AP MLD may include one or more other STAs configured to operate on one or more other respective communication links.

[0082]

[0101] In the example of FIG. 8B, the STA 830 operates as a non-legacy STA on link 2 and obtains TSF information from beacon frames TBTT(1)1-TBTT(3)1 broadcast on link 1 by the AP 810 of FIG. 8A. Specifically, the STA 830 does not listen to and does not receive beacon frames TBTT(1)2-TBTT(3)2 broadcast on link 2 by the AP 820. Thus, the STA 830 does not receive the current TSF value of the AP 820 from the beacon frame transmission, and therefore may estimate the current TSF value of the AP 820 based on the current TSF value of the AP 810 and the TSF offset between the AP 810 and the AP 820, for example, as indicated in the beacon frames TBTT(1)2-TBTT(3)2 broadcast on link 2 by the AP 820.

[0083]

[0102] AP 820 schedules r-TWT SP 840 on link 2 between times t4 and t6. In the example of FIG. 8B, STA 830 is not a member of r-TWT SP 840 and therefore must terminate any TXOP obtained outside of r-TWT SP 840 prior to the start time of r-TWT SP 840, e.g., as specified in the 802.11be amendment to the IEEE 802.11 standard. As described, AP 820 has a slower clock than AP 810, and STA 830 synchronizes its local TSF timer based on AP 810's current TSF value obtained from beacon frames TBTT(1)1-TBTT(3)1 broadcasted on link 1. The TSF offset between the STA 830 and the AP 820, including the TSF offset between the STA 830 and the AP 820 as well as the TSF offset between the AP 810 and the AP 820, causes the STA 830 to determine a start time for the r-TWT SP 840 that is earlier than the start time determined by the AP 820.

[0084]

[0103] For example, after acquiring the current TSF value of the AP 810 from a beacon frame transmission on link 1, the STA 830 may perform a CCA operation on link 2. Specifically, between time t0 and t1, the STA 830 detects that link 2 is idle for the AIFS duration and counts down the RBO duration before attempting to acquire a TXOP on link 2. At time t1, the STA 830 detects that link 2 is still idle and acquires a TXOP on link 2. The TXOP acquired by the STA 830 is longer than the duration of the time remaining before the start of the r-TWT SP840, and therefore the STA 830 must end the TXOP before the start of the r-TWT SP840 on link 2. As described, the TSF offset between the STA 830 and the AP 820 causes the STA 830 to erroneously determine that the start time of the r-TWT SP840 occurs at time t2, instead of the correct start time which occurs at time t4. As a result, the STA 830 ends the TXOP early at time t2.

[0085]

[0104] Existing rules for r-TWT SP allow a non-member STA, such as STA 830, to access a communication link prior to the start time of the r-TWT SP, as long as the non-member STA terminates any acquired TXOP before the start of the r-TWT SP. In the example of FIG. 8B, after terminating the TXOP early at time t2, STA 830 detects that link 2 is idle for the AIFS+RBO duration between time t2 and t3, and acquires another TXOP 845 on link 2 at time t3. As described, STA 830 determines that the r-TWT SP 840 starts at time t2 (rather than at time t4) and does not terminate the TXOP 840. As shown, the TXOP 845 spans a duration between time t3 and t5, thereby preventing any member STA from accessing link 2 during at least a portion of the r-TWT SP 840.

[0086]

[0105] 8C shows another timing diagram 850 illustrating an example beacon frame transmission. The timing diagram 850 shows the APs 810 and 820 of FIG. 8A broadcasting beacon frames on link 1 and link 2, respectively. Specifically, the AP 810 broadcasts beacon frames B11-B31 on link 1 at respective times TBTT(1)1-TBTT(3)1, and the AP 820 broadcasts beacon frames B12-B32 on link 2 at respective times TBTT(1)2-TBTT(3)2. Each of the beacon frames B11-B31 broadcasted on link 1 may include a current TSF value of the AP 810 and a TSF offset between the AP 810 and the AP 820, and each of the beacon frames B12-B32 broadcasted on link 2 may include a current TSF value of the AP 820 and a TSF offset between the AP 820 and the AP 810. As described, the TSF timer of AP810 may be used as a reference for the TSF offset between AP810 and AP820, and the beacon interval associated with AP810 (and thus the corresponding transmission times TBTT(1)1 to TBTT(3)1) may be used as a reference for the timing offset between AP810 and AP820.

[0087]

[0106] 8C example, AP 820 has a slower clock than AP 810 (or AP 810 has a faster clock than AP 820), which may cause beacon transmission times TBTT(1)1-TBTT(3)1 associated with AP 810 to occur at increasingly later times than corresponding beacon transmission times TBTT(1)2-TBTT(3)2 associated with AP 820. For example, the respective transmissions of a first beacon frame B11 on link 1 and a first beacon frame B12 on link 2 are aligned with one another (and thus have the same TBTT), but the transmission of a second beacon frame B22 on link 2 occurs before the transmission of a second beacon frame B21 on link 1 by an offset amount=Δt, the transmission of a third beacon frame B32 on link 2 occurs before the transmission of a third beacon frame B31 on link 1 by an offset amount=Δ2t, and so on. Thus, the second beacon transmission time TBTT(2)1 associated with link 1 occurs a time period equal to Δt after the corresponding second beacon transmission time TBTT(2)2 associated with link 2, and the third beacon transmission time TBTT(3)1 associated with link 1 occurs a time period equal to Δ2t after the corresponding third beacon transmission time TBTT(3)2 associated with link 2.

[0088]

[0107] FIG. 8D shows a timing diagram 850B illustrating an example wireless communication between devices. The timing diagram 850B includes the AP 820 of FIG. 8C and the STA 830. As described, the STA 830 operates as a non-legacy STA on link 2 and obtains TSF information from beacon frames TBTT(1)1-TBTT(3)1 broadcasted on link 1 by the AP 810. The STA 830 does not receive the current TSF value of the AP 820 from the beacon frame transmission, but instead estimates the current TSF value of the AP 820 based on the current TSF value of the AP 810 and the TSF offset between the AP 810 and the AP 820, e.g., as indicated in the beacon frames TBTT(1)2-TBTT(3)2 broadcasted on link 2 by the AP 820.

[0089]

[0108] AP 820 schedules r-TWT SP 860 on link 2 between times t2 and t6. In the example of FIG. 8D, STA 830 is not a member of r-TWT SP 860 and therefore must terminate any TXOP obtained outside of r-TWT SP 860 prior to the start time of r-TWT SP 860. As described, AP 810 has a slower clock than AP 820, and STA 830 synchronizes its local TSF timer based on AP 810's current TSF value obtained from beacon frames TBTT(1)1-TBTT(3)1 broadcasted on link 1. The TSF offset between STA 830 and AP 820 causes STA 830 to determine a start time for r-TWT SP 860 that is later than the start time determined by AP 820.

[0090]

[0109] For example, after acquiring the current TSF value of the AP 810 from a beacon frame transmission on link 1, the STA 830 may perform a CCA operation on link 2. Specifically, between time t0 and t1, the STA 830 detects that link 2 is idle for the AIFS duration and counts down the RBO duration before attempting to acquire a TXOP on link 2. At time t1, the STA 830 detects that link 2 is still idle and acquires a TXOP on link 2. The TXOP acquired by the STA 830 is longer than the duration of the time remaining before the start of the r-TWT SP860, and therefore, the STA 830 terminates the TXOP at time t3 in an attempt to comply with the existing rules for r-TWT operation. However, because the AP 810 has a slower clock than the AP 820, the start time of the r-TWT SP860 estimated by the STA 830, time t3, occurs after the correct start time of the r-TWT SP860, time t2. Thus, although STA 830 terminates the TXOP early, the TXOP held by STA 830 overlaps with r-TWT SP 860 from time t2 to t3, thereby preventing any member STA from accessing link 2 during at least a portion of r-TWT SP 860 spanning time t2 to t3. Thus, as explained above, tighter synchronization needs to be maintained between the AP and the AP's associated STAs, and more particularly, between the STAs and the APs in the AP MLD, to ensure that the TSF offset resulting from clock drift does not cause non-member STAs to hold a TXOP or attempt to acquire a TXOP during an r-TWT SP scheduled on the shared wireless medium.

[0091]

[0110] Implementations of the subject matter described in this disclosure may be used to synchronize timing between STAs and APs in a manner that may prevent STAs operating on a communication link from inadvertently interfering with one or more r-TWT SPs scheduled on the communication link. Specifically, in various implementations, a device including a first AP may establish an extended synchronization mode in which participating STAs receive timing information of one or more associated APs or nearby APs with sufficient periodicity to ensure that a TSF offset between the STAs and the AP does not exceed a value that may allow the STAs to inadvertently access or occupy the shared wireless medium during r-TWT SPs scheduled on the shared wireless medium. For example, in some implementations, the device may transmit an indication of the extended synchronization mode to one or more STAs associated with the device on a first communication link associated with the device's first AP. In some cases, the indication may be in response to a presence of latency-sensitive traffic on the first communication link. In some other cases, the indication may be in response to a request from one or more STAs. In some aspects, the indication may also indicate a start time of the extended synchronization mode. In other aspects, the indication may also indicate whether participation in the enhanced synchronous mode is mandatory or voluntary for each of the one or more STAs.

[0092]

[0111] The device may transmit a plurality of synchronization frames on the first communication link during the extended synchronization mode more frequently than a TBTT associated with the first communication link. Each of the synchronization frames may indicate a TSF value of the first AP and a TSF offset between the first AP and the second AP of the device. The frequency at which the synchronization frames are transmitted on the first communication link may be associated with a level of timing accuracy that prevents participating STAs from occupying or accessing the first communication link during one or more r-TWT SPs scheduled on the first communication link. For example, in some instances, the synchronization frames may be transmitted at intervals of about 20 μs (although other suitable intervals may be used). STAs participating in the extended synchronization mode may use the TSF information indicated in the synchronization frames to synchronize their respective local TSF timers with the TSF timers of the first AP and the second AP of the device, for example, without receiving a beacon frame from the second AP. In some implementations, the extended synchronization mode may be established with one or more TWT SPs or r-TWT SPs on the first communication link. In some aspects, a device may reject association requests from STAs that do not support the extended synchronization mode during a time period starting prior to the start time of the extended synchronization mode and ending at the end of the extended synchronization mode.

[0093]

[0112] FIG. 9 shows a sequence diagram illustrating an example wireless communication 900 supporting an extended synchronization mode according to some implementations. The wireless communication device 900 may be implemented between an AP 910, an AP 920, and a STA 930. The APs 910 and 920 may be part of or associated with an AP MLD configured to communicate over multiple different communication links. Specifically, the AP 910 may be configured to operate over a first communication link, and the AP 920 may be configured to operate over a second communication link different from the first communication link. In some instances, the first communication link may be a wireless channel in one of the 2.4 GHz frequency band, the 5 GHz frequency band, or the 6 GHz frequency band, and the second communication link may be a wireless channel in another one of the 2.4 GHz frequency band, the 5 GHz frequency band, or the 6 GHz frequency band.

[0094]

[0113] In some implementations, the APs 910 and 920 may be an example of the AP 102 of Figure 1, the wireless communication device 400 of Figure 4, the AP 502 of Figure 5A, or the AP MLD 610 of Figure 6, and the STA 930 may be an example of any of the STAs 104 of Figure 1, the wireless communication device 400 of Figure 4, the STA 504 of Figure 5B, or the non-AP MLD 620 of Figure 6. Although not shown for simplicity, the STA 930 may be part of or associated with a STA MLD that includes one or more other STAs that may operate on one or more other communication links of the AP MLD.

[0095]

[0114] In the example of FIG. 9, the AP 910 establishes or schedules an extended synchronization mode for a STA operating on a first communication link, and the STA 930 operates as a non-legacy STA supporting r-TWT SP operation. The AP 910 transmits a frame carrying an indication of the extended synchronization mode on the first communication link to the STA 930. The frame may be one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame transmitted on the first communication link. In some implementations, the frame may also indicate whether participation in the extended synchronization mode is mandatory or voluntary for the STA 930 (and for other STAs associated with the first communication link). For example, in some instances, the AP 910 may obtain a TSF offset between the TSF timer of the AP and the TSF timer of each of the multiple STAs operating on the first communication link (including the STA 930) and may determine whether participation in the extended synchronization mode is mandatory or voluntary based at least in part on the TSF offset. In some aspects, whether participation in the extended synchronous mode is mandatory or voluntary for at least some STAs may also be based on an indication of latency-sensitive traffic on the first communication link. For example, when latency-sensitive traffic is present on the first communication link, the AP 910 may be more likely to consider participation in the extended synchronous mode mandatory.

[0096]

[0115] The AP 910 may also indicate to the STA 930 a start time of the extended synchronization mode. In some aspects, the indicated start time may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a TWT response frame transmitted on the first communication link. The STA 930 receives an indication of the extended synchronization mode, a start time of the extended synchronization mode, and whether the STA 930's participation in the extended synchronization mode is mandatory or voluntary. Based on the indication of the extended synchronization mode, the STA 930 may prepare to monitor and / or receive a plurality of synchronization frames on the first communication link more frequently than a TBTT associated with the first communication link. The STA 930 may begin to prepare to monitor and / or receive a plurality of synchronization frames (e.g., enter or start the extended synchronization mode) based on the start time of the extended synchronization mode indicated by the AP 910. When the STA 930's participation in the extended synchronization mode is mandatory, the STA 930 may, for example, prepare to receive a plurality of synchronization frames transmitted on the first communication link and adjust the STA's local TSF timer based on the received TSF information. When STA930's participation in the extended synchronization mode is voluntary, STA930 may join the extended synchronization mode based on one or more of, for example, the presence of latency-sensitive traffic on one or more communication links, an indication that STA930 is to receive or be associated with latency-sensitive traffic, an indication that the TSF offset between STA930 and AP910 is greater than a first amount, or an indication that the TSF offset between STA930 and AP920 is greater than a second amount that is different from the first amount.

[0097]

[0116] In some instances, the AP 910 may indicate to the STA 930 whether the APs 910 and 920 share a common clock or a common TSF value across the APs 910 and 920. In some aspects, an indication of a common clock or a common TSF value is carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a synchronization frame. The STA 930 may receive the indication and determine whether timing synchronization with the AP 920 is required. For example, if the APs 910 and 920 share the same clock or the same TSF value, timing synchronization with both the APs 910 and 920 may be achieved based on synchronization between the respective TSF values ​​of the AP 910 and the STA 930. In another example, if the APs 910 and 920 do not share the same clock or the same TSF value, the STA 930 may voluntarily participate in an extended synchronization mode to ensure that the TSF offset between the STA 930 and each of the first AP 910 and the second AP 920 is less than a certain value, for example.

[0098]

[0117] During the extended synchronization mode, the AP 910 transmits multiple synchronization frames on the first communication link more frequently than the TBTT associated with the first communication link, such that multiple synchronization frames may be transmitted to the STAs 930 during each beacon interval of the AP 910. In various implementations, the synchronization frames may be FILS discovery frames that may be transmitted on the first communication link at a data rate greater than a basic data rate associated with a beacon frame transmission from the AP 910. In some aspects, the AP 910 may transmit synchronization frames on the first communication link at intervals of about 20 milliseconds. In other aspects, the AP 910 may transmit synchronization frames on the first communication link at other suitable intervals that are shorter than the beacon interval of the AP 910. In some implementations, the AP 910 may establish an extended synchronization mode with one or more TWT SPs or one or more r-TWT SPs scheduled on the first communication link.

[0099]

[0118] In some implementations, each of the synchronization frames may indicate a TSF offset between the AP 910 and the AP 920, for example, so that the STA 930 can synchronize the STA's TSF timer with the current TSF values ​​of the AP 910 and the AP 920. In some aspects, each of the synchronization frames may also indicate the TSF value of the AP 910. In some cases, the AP 910 may transmit an indication of the extended synchronization mode in response to a presence of latency-sensitive traffic on the first communication link. In other cases, the AP 910 may transmit an indication of the extended synchronization mode in response to a request from the STA 930 (or one or more other STAs associated with the first communication link).

[0100]

[0119] In various aspects, the AP 910 may reject association requests from legacy STAs 940 that do not support the extended synchronous mode during a time period beginning before the start time of the extended synchronous mode and ending at or after the end of the extended synchronous mode. For example, when the legacy STAs 940 transmit an association request frame to the AP 910 including a request that the AP 910 perform association and authentication operations with the legacy STAs 940, the AP 910 responds by transmitting an association response frame to the legacy STAs 940 that conveys a rejection of the association request. In this manner, the AP 910 may prevent the legacy device from accessing the first communication link during the extended synchronous mode. Rejecting such association requests during the extended synchronous mode may also prevent the legacy device that does not support r-TWT operation from attempting to obtain a TXOP that may interfere with the scheduled r-TWT SP on the first communication link.

[0101]

[0120] In some implementations, the STA 930 may transmit a frame to the AP 910 indicating one or more of: an amount of clock drift between the at least one STA and the first AP during each beacon interval, whether the at least one STA participates in the extended synchronization mode, whether the at least one STA receives beacon frames on the first communication link or on a second communication link associated with the second AP, or a frequency at which the at least one STA receives beacon frames indicating TSF information of the first AP. The AP 910 may receive the frame and establish one or more TWT SPs or one or more r-TWT SPs for latency-sensitive traffic on the first communication link based at least in part on the one or more indications received from the at least one STA.

[0102]

[0121] In various cases, the AP 910 may terminate the extended synchronization mode in response to an indication of timing synchronization between the first AP and each of the multiple STAs participating in the extended synchronization mode. In some cases, one or more of the multiple STAs may send an indication of timing synchronization to the AP 910. In some aspects, the termination of the extended synchronization mode may be further based on an indication of timing synchronization between the second AP and each of the multiple STAs participating in the extended synchronization mode.

[0103]

[0122] FIG. 10 shows a timing diagram illustrating an example wireless communication 1000 supporting an extended synchronous mode according to some other implementations. The timing diagram 1000 includes the AP 810 and the STA 830 described with reference to FIG. 8A-8B. As described, a TSF offset between the STA 830 and the AP 810 resulting from clock drift may cause the STA to erroneously estimate the start time of the r-TWT SP 1060 as time t2 instead of the correct start time t3. In some implementations, the AP 810 may obtain a time period associated with the TSF offset (e.g., a time offset between time t2 and t3) and schedule a guard SP at the beginning of the r-TWT SP 1060. Specifically, the guard SP may span a time period between time t3 and t4, for example, to prevent the STA 830 from attempting to access link 1 during the r-TWT SP 1060. For example, the non-member STA 830 detects that link 1 is idle for the AIFS duration and counts down the RBO duration from time t0 to t1 before attempting to acquire a TXOP. At time t1, the non-member STA 830 detects that link 1 is still idle and acquires a TXOP on link 1. In the example of FIG. 8B, the TXOP acquired by the non-member STA 830 may be longer than the duration remaining before the start of the r-TWT SP860, and the non-member STA 830 terminates the TXOP at time t3 in an attempt to comply with the existing rules for r-TWT operation. However, because the clock of the AP 810 is faster than the clock of the AP 820, the start time t3 of the r-TWT SP860 estimated by the non-member STA 830 occurs after the correct start time t4 of the r-TWT SP860. Specifically, the TXOP truncated by the non-member STA 830 spans a portion of the r-TWT SP 860 from time t2 to t3, thereby preventing any member STA from accessing link 1 during at least a portion of the r-TWT SP 860 spanning from t2 to t3.

[0104]

[0123] 11 illustrates a flow diagram illustrating example operations 1100 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1100 may be performed by a wireless device, such as the wireless communication device 400 described above with reference to FIG. 4. In some instances, the operations 1100 may be performed by a wireless device operating as or within an AP, such as the AP 102 of FIG. 1, the wireless communication device 400 of FIG. 4, the AP 502 of FIG. 5A, or the AP MLD 610 of FIG. 6.

[0105]

[0124] For example, at 1102, the device transmits an indication of an extended synchronization mode to at least one wireless station (STA) on a first communication link associated with a first access point (AP) of the device. At 1104, the device transmits a plurality of synchronization frames on the first communication link during the extended synchronization mode more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) value of the first AP and a TSF offset between the first AP and a second AP of the device. In some instances, the indication may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame transmitted on the first communication link. In some aspects, a time period between successive transmissions of the synchronization frames may be about 20 milliseconds. In other aspects, the plurality of synchronization frames may be transmitted at a data rate greater than a basic data rate associated with the beacon frame transmission on the first communication link.

[0106]

[0125] In some implementations, the device may be an AP multi-link device (MLD) including a first AP and a second AP, the first AP being associated with a first communication link and the second AP being associated with a second communication link occupying a different frequency band than the first communication link. In some instances, at least one of the plurality of synchronization frames may be a fast initial link setup (FILS) discovery frame carrying a TSF value of the first AP and a TSF offset value of the second AP. In various aspects, the indication of the extended synchronization mode may be transmitted based on an indication of latency-sensitive traffic on at least the first communication link. In some aspects, the extended synchronization mode may be established with one or more TWT service periods (SPs) or one or more restricted TWT (r-TWT) SPs scheduled on the first communication link.

[0107]

[0126] 12 illustrates a flow diagram illustrating example operations 1200 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1200 may be performed by a wireless device, such as the wireless communication device 400 described above with reference to FIG. 4. In some instances, the operations 1200 may be performed by a wireless device operating as or within an AP, such as the AP 102 of FIG. 1, the wireless communication device 400 of FIG. 4, the AP 502 of FIG. 5A, or the AP MLD 610 of FIG. 6.

[0108]

[0127] In some cases, operation 1200 may be performed after operation 1100 of Figure 11. For example, in block 1202, the device terminates the extended synchronization mode in response to an indication of timing synchronization between the first AP and each of the multiple STAs participating in the extended synchronization mode. In some aspects, the termination of the extended synchronization mode is further based on an indication of timing synchronization between the second AP and each of the multiple STAs participating in the extended synchronization mode.

[0109]

[0128] Figure 13 shows a flow diagram illustrating example operations 1300 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1300 may be performed by a wireless communication device, such as the wireless communication device 400 described above with reference to Figure 4. In some implementations, the operations 1300 may be performed by a wireless communication device operating as or within an AP, such as the AP 102 of Figure 1, the wireless communication device 400 of Figure 4, the AP 502 of Figure 5A, or the AP MLD 610 of Figure 6.

[0110]

[0129] In some cases, the operations 1300 may be performed prior to transmitting an indication of the extended synchronization mode at 1102 of Figure 11. For example, at block 1302, the device receives a request from one or more STAs to enter the extended synchronization mode, and the indication of the extended synchronization mode is transmitted based on the request.

[0111]

[0130] Figure 14 shows a flow diagram illustrating example operations 1400 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1400 may be performed by a wireless communication device, such as the wireless communication device 400 described above with reference to Figure 4. In some implementations, the operations 1400 may be performed by a wireless communication device operating as or within an AP, such as the AP 102 of Figure 1, the wireless communication device 400 of Figure 4, the AP 502 of Figure 5A, or the AP MLD 610 of Figure 6.

[0112]

[0131] In some cases, the operations 1400 may be performed prior to transmitting synchronization frames at 1104 of FIG. 11. For example, in block 1402, the device indicates a start time of the extended synchronization mode to at least one STA. In some cases, the indicated start time may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame transmitted on the first communication link.

[0113]

[0132] Figure 15 shows a flow diagram illustrating example operations 1500 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1500 may be performed by a wireless communication device, such as the wireless communication device 400 described above with reference to Figure 4. In some implementations, the operations 1500 may be performed by a wireless communication device operating as or within an AP, such as the AP 102 of Figure 1, the wireless communication device 400 of Figure 4, the AP 502 of Figure 5A, or the AP MLD 610 of Figure 6.

[0114]

[0133] In some cases, operation 1500 may be performed after operation 1100 of FIG. 11. For example, at block 1502, the device obtains a TSF offset between the first AP and each of the plurality of STAs. At 1504, the device indicates to each of the plurality of STAs whether participation in the extended synchronization mode is mandatory or voluntary based at least in part on the TSF offset. In some cases, whether participation in the extended synchronization mode is mandatory or voluntary for at least some of the plurality of STAs may be further based on an indication of latency-sensitive traffic on the first communication link.

[0115]

[0134] 16 illustrates a flow diagram illustrating example operations 1600 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1600 may be performed by a wireless communication device, such as the wireless communication device 400 described above with reference to FIG. 4. In some implementations, the operations 1600 may be performed by a wireless communication device operating as or within an AP, such as the AP 102 of FIG. 1, the wireless communication device 400 of FIG. 4, the AP 502 of FIG. 5A, or the AP MLD 610 of FIG. 6.

[0116]

[0135] In some cases, the operation 1600 may be performed at any time before, during, or after the operation 1100 of FIG. 11. For example, in block 1602, the device indicates to at least one STA whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device. In some cases, the indication of the common clock or the common TSF value across the first AP and the second AP of the device may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame. In other cases, the indication of the common clock or the common TSF value across the first AP and the second AP may be carried in a synchronization frame. The at least one STA may use the indication to determine whether or not participation in the extended synchronization mode should be used to maintain a certain level of timing synchronization with the second AP of the device. For example, if the first AP and the second AP of the device share a common clock or a common TSF value, there may not be any TSF offset between the first AP and the second AP of the device. Thus, at least one STA may be able to maintain sufficient timing synchronization with the first AP to avoid interfering with the r-TWT SP without participating in the extended synchronization mode.

[0117]

[0136] 17 shows a flow diagram illustrating example operations 1700 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1700 may be performed by a wireless communication device, such as the wireless communication device 400 described above with reference to FIG. 4. In some implementations, the operations 1700 may be performed by a wireless communication device operating as or within an AP, such as the AP 102 of FIG. 1, the wireless communication device 400 of FIG. 4, the AP 502 of FIG. 5A, or the AP MLD 610 of FIG. 6.

[0118]

[0137] In some instances, operations 1700 may be performed at any time during operations 1100 of FIG. 11. For example, in block 1702, the device rejects association requests from STAs that do not support the extended synchronization mode during a time period beginning before a start time of the extended synchronization mode. For example, the device may reject association requests on the first communications link from legacy devices to prevent such legacy devices from being able to contend for access to the first communications link during any r-TWT SPs scheduled on the first communications link.

[0119]

[0138] Figure 18 shows a flow diagram illustrating example operations 1800 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1800 may be performed by a wireless communication device, such as the wireless communication device 400 described above with reference to Figure 4. In some implementations, the operations 1800 may be performed by a wireless communication device operating as or within an AP, such as the AP 102 of Figure 1, the wireless communication device 400 of Figure 4, the AP 502 of Figure 5A, or the AP MLD 610 of Figure 6.

[0120]

[0139] In some implementations, the operation 1800 may be performed any time before, during, or after the operation 1100 of FIG. 11. For example, at block 1802, the device receives a frame from the at least one STA indicating one or more of: an amount of clock drift between the at least one STA and the first AP during each beacon interval; whether the at least one STA participates in an extended synchronization mode; whether the at least one STA receives beacon frames on the first communication link or on a second communication link associated with the second AP; or a frequency at which the at least one STA receives beacon frames or synchronization frames indicating TSF information of the first AP. At 1804, the device schedules one or more TWT SPs or r-TWT SPs for latency sensitive traffic on the first communication link based at least in part on the one or more indications received from the at least one STA.

[0121]

[0140] 19 shows a flow diagram illustrating example operations 1900 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 1900 may be performed by a wireless device, such as the wireless communication device 400 described above with reference to FIG. 4. In some instances, the operations 1900 may be performed by a wireless device operating as or within a STA, such as one of the STAs 104 of FIG. 1, the wireless communication device 400 of FIG. 4, the STA 504 of FIG. 5B, or the non-AP MLD 620 of FIG. 6.

[0122]

[0141] For example, at 1902, the device receives an indication of an extended synchronization mode from a first AP of an AP multilink device (MLD) on a first communication link associated with the first AP. At 1904, the device receives a plurality of synchronization frames during the extended synchronization mode on the first communication link more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between the first AP and a second AP of the AP MLD. In some implementations, each of the plurality of synchronization frames may also indicate a TSF value of the first AP. In some instances, the indication may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a TWT response frame received on the first communication link. In some aspects, the time period between successive receipt of the synchronization frames may be about 20 milliseconds. In other aspects, the plurality of synchronization frames may be received at a data rate greater than a basic data rate associated with the beacon frame transmission on the first communication link.

[0123]

[0142] In various implementations, the device may be a non-AP MLD including a plurality of STAs configured to operate on a plurality of respective communication links. In some instances, at least one of the plurality of synchronization frames may be a FILS discovery frame carrying a TSF value of the first AP. In various aspects, an indication of an extended synchronization mode may be received based on an indication of latency sensitive traffic on at least the first communication link. In some aspects, the extended synchronization mode may be established with one or more TWT SPs or one or more r-TWT SPs scheduled on the first communication link.

[0124]

[0143] In some implementations, the device may send a request for the AP MLD to start the extended synchronization mode at 1906. In some instances, an indication of the extended synchronization mode may be received from the AP MLD based on the request.

[0125]

[0144] In other implementations, at 1908, the device may receive an indication of a start time of the extended synchronization mode from the AP MLD at 1908. In some cases, the indication of the extended synchronization mode may be received from the AP MLD based on a request. In some cases, the indicated start time may be carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a TWT response frame received on the first communication link.

[0126]

[0145] In some other implementations, at 1910, the device may receive an indication from the AP MLD of whether participation in the extended synchronization mode is mandatory or voluntary for the device based at least in part on the TSF offset between the first AP and each of the multiple STAs. In some cases, the indication of the common clock or common TSF value across the first AP and the second AP of the device may be carried in one or more of a beacon frame, a probe response frame, or a broadcast action frame. In other cases, the indication of the common clock or common TSF value across the first AP and the second AP may be carried in a synchronization frame. In some aspects, the device may use the indication to determine whether participation in the extended synchronization mode should be used to maintain a certain level of timing synchronization with the second AP of the AP MLD. For example, if the first AP and the second AP of the AP MLD share a common clock or a common TSF value, there may not be any TSF offset between the first AP and the second AP of the AP MLD. Thus, the device may be able to maintain sufficient timing synchronization with the first AP to avoid interfering with the r-TWT SP without participating in the extended synchronization mode.

[0127]

[0146] In some cases, at 1912, the device may receive an indication from the AP MLD of whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device.

[0128]

[0147] Figure 20 shows a flow diagram illustrating example operations 2000 for wireless communication supporting an extended synchronization mode, according to some implementations. The operations 2000 may be performed by a wireless communication device, such as the wireless communication device 400 described above with reference to Figure 4. In some implementations, the operations 2000 may be performed by a wireless device operating as or within a STA, such as one of the STAs 104 of Figure 1, the wireless communication device 400 of Figure 4, the STA 504 of Figure 5B, or the non-AP MLD 620 of Figure 6.

[0129]

[0148] In some cases, operation 2000 may be performed after operation 1900 of FIG. 19. For example, at 2002, the device transmits a frame to the AP MLD indicating one or more of: an amount of clock drift between the device and the first AP during each beacon interval; whether the device is participating in an extended synchronization mode; whether the device receives beacon frames on the first communication link or on a second communication link associated with the second AP; or a frequency at which the device receives beacon or synchronization frames indicating TSF information of the first AP. At 2004, the device receives an indication from the AP MLD of one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs for latency sensitive traffic on the first communication link based at least in part on one or more indications provided by the device.

[0130]

[0149] FIG. 21 illustrates a block diagram of an example wireless communication device 1900. In some implementations, the wireless communication device 2100 may be configured to perform the operations 1200, 1300, 1400, 1500, 1600, 1700, and 1800 described with reference to FIG. 12, FIG. 13, FIG. 14, FIG. 15, FIG. 16, FIG. 17, and FIG. 18, respectively. The wireless communication device 2100 may be an example implementation of any of the APs 102 of FIG. 1, the wireless communication device 400 of FIG. 4, the AP 502 of FIG. 5A, or the AP MLD 610 of FIG. 6. In some implementations, the wireless communication device 2100 may be an example of an AP MLD. More specifically, the wireless communication device 2100 may be a chip, SoC, chipset, package, or device including at least one processor and at least one modem (e.g., a Wi-Fi (IEEE 802.11) modem or a cellular modem).

[0131]

[0150] The wireless communication device 2100 includes a receiving component 2110, a communications manager 2120, and a transmitting component 2130. The communications manager 2120 further includes an extended synchronous mode component 2121, a sync frame component 2122, a TSF offset component 2123, a multilink component 2124, and a TWT component 2125. One or more portions of the components 2121-2125 may be implemented at least partially in hardware or firmware. In some implementations, one or more of the components 2121-2125 are implemented at least partially as software stored in a memory (such as the memory 408 of FIG. 4). For example, one or more portions of the components 2121-2125 may be implemented as non-transitory instructions (or "code") executable by a processor (such as the processor 406 of FIG. 4) to perform the functions or operations of the respective components.

[0132]

[0151] The receiving component 2110 is configured to receive RX signals from one or more other wireless communication devices, and the transmitting component 2130 is configured to transmit TX signals to one or more other wireless communication devices. The communications manager 2120 is configured to manage wireless communications with one or more other wireless communication devices. In some implementations, the extended synchronization mode component 2121 may establish an extended synchronization mode on one or more communication links associated with the wireless communication device 2100. The synchronization frame component 2122 may transmit multiple synchronization frames to one or more other wireless communication devices, such as STAs, non-AP MLDs, and client devices. The TSF offset component 2123 may determine or obtain TSF offsets between multiple APs in or associated with the wireless communication device 2100. The multilink component 2124 may establish multiple communication links associated with the wireless communication device 2100. The TWT component 2125 may schedule one or more TWT SPs or one or more r-TWT SPs for latency sensitive traffic on one or more communication links associated with the wireless communication device 2100.

[0133]

[0152] FIG. 22 illustrates a block diagram of an example wireless communication device 1900. In some implementations, the wireless communication device 2200 may be configured to perform the operations 1900 and 2000 described with reference to FIG. 19 and FIG. 20, respectively. The wireless communication device 2200 may be an example implementation of any of the STAs 104 of FIG. 1, the wireless communication device 400 of FIG. 4, the STA 504 of FIG. 5B, or the non-AP MLD 620 of FIG. 6. In some implementations, the wireless communication device 2200 may be an example of a STA MLD. More specifically, the wireless communication device 2200 may be a chip, SoC, chipset, package, or device including at least one processor and at least one modem (e.g., a Wi-Fi (IEEE 802.11) modem or a cellular modem).

[0134]

[0153] The wireless communication device 2200 includes a receiving component 2210, a communications manager 2220, and a transmitting component 2230. The communications manager 2220 further includes an extended synchronous mode component 2221, a sync frame component 2222, a TSF offset component 2223, a multilink component 2224, and a TWT component 2225. One or more portions of the components 2221-2225 may be implemented at least partially in hardware or firmware. In some implementations, one or more of the components 2221-2225 are implemented at least partially as software stored in a memory (such as the memory 408 of FIG. 4). For example, one or more portions of the components 2221-2225 may be implemented as non-transitory instructions (or "code") executable by a processor (such as the processor 406 of FIG. 4) to perform the functions or operations of the respective components.

[0135]

[0154] The receiving component 2210 is configured to receive RX signals from one or more other wireless communication devices, and the transmitting component 2230 is configured to transmit TX signals to one or more other wireless communication devices. The communications manager 2220 is configured to manage wireless communications with one or more other wireless communication devices. In some implementations, the extended synchronization mode component 2221 may coordinate the participation of the wireless communication device 2200 in one or more extended synchronization modes established on a communication link. The synchronization frame component 2222 may receive multiple synchronization frames from one or more APs of the AP MLD. The TSF offset component 2223 may determine or obtain a TSF offset between the wireless communication device 2200 and one or more other devices. The multilink component 2224 may establish multiple communication links associated with the wireless communication device 2200. The TWT component 2225 may schedule one or more TWT SPs or one or more r-TWT SPs for latency sensitive traffic on one or more communication links associated with the wireless communication device 2200.

[0136]

[0155] Example implementations are described in the following numbered clauses. 1. At least one processor; at least one memory communicatively coupled to the at least one processor and storing processor-readable code; A device comprising: The processor-readable code, when executed by at least one processor, Transmitting an indication of an extended synchronization mode to at least one wireless station (STA) over a first communication link associated with a first access point (AP) of the device; transmitting a plurality of synchronization frames during an extended synchronization mode on the first communication link more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between a first AP and a second AP of the device; The device is configured as follows: 2. The device of clause 1, wherein at least one of the plurality of synchronization frames includes a fast initial link setup (FILS) discovery frame carrying a TSF value of the first AP. 3. A device described in any one or more of clauses 1-2, wherein the time period between successive transmissions of the synchronization frame is approximately 20 milliseconds. 4. A device described in any one or more of clauses 1-3, wherein multiple synchronization frames are transmitted at a data rate greater than a basic data rate associated with beacon frame transmissions on the first communications link. 5. A device described in any one or more of clauses 1 to 4, wherein the device includes an AP multi-link device (MLD) including a first AP and a second AP, the first AP being associated with a first communication link and the second AP being associated with a second communication link occupying a different frequency band than the first communication link. 6. A device described in any one or more of clauses 1 to 5, wherein the instruction is conveyed in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame transmitted on the first communication link. 7. Execution of processor-readable code exiting the extended synchronous mode in response to an indication of timing synchronization between the first AP and each of the plurality of STAs participating in the extended synchronous mode; 7. The device of any one or more of clauses 1-6, further configured to: 8. The device of clause 7, wherein exiting the extended synchronization mode is further based on an indication of timing synchronization between the second AP and each of a plurality of STAs participating in the extended synchronization mode. 9. A device described in any one or more of clauses 1-8, wherein the indication of the extended synchronization mode is sent based on an indication of latency-sensitive traffic on at least the first communications link. 10. Execution of processor-readable code receiving a request from one or more STAs to enter an extended synchronous mode; 10. The device of any one or more of clauses 1-9, further configured such that the indication of the extended synchronization mode is sent upon request. 11. Execution of processor-readable code Indicate the start time of the extended synchronous mode to at least one STA, 11. The device of any one or more of clauses 1-10, further configured to: 12. The device of claim 11, wherein the indicated start time is carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame transmitted on the first communications link. 13. Execution of processor-readable code Obtaining a TSF offset between a first AP and each of a plurality of STAs; indicating to each of a plurality of STAs whether participation in the enhanced synchronous mode is mandatory or voluntary based at least in part on the TSF offset; 13. The device of any one or more of clauses 1-12, further configured to: 14. The device of clause 13, wherein whether participation in the extended synchronous mode is mandatory or voluntary for at least some of the multiple STAs is further based on an indication of latency-sensitive traffic on the first communications link. 15. The device of any one or more of clauses 1-14, wherein an extended synchronization mode is established along with one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs scheduled on the first communications link. 16. Execution of processor-readable code indicating to at least one STA whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device; 16. The device of any one or more of clauses 1-15, further configured to: 17. The device of clause 16, wherein an indication of a common clock or common TSF value across the device's first AP and second AP is carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a synchronization frame. 18. Execution of processor-readable code rejecting association requests from STAs that do not support the enhanced synchronization mode during a time period that begins before the start time of the enhanced synchronization mode; 18. The device of any one or more of clauses 1-17, further configured to: 19. Execution of processor-readable code A frame, an amount of clock drift between the at least one STA and the first AP during each beacon interval; Whether at least one STA is participating in the enhanced synchronization mode, At least one STA receives a beacon frame on a first communication link or on a second communication link associated with a second AP; or a frequency at which at least one STA receives a beacon frame or a synchronization frame indicating the TSF information of the first AP; receiving a frame from at least one STA indicating one or more of: scheduling one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs for latency sensitive traffic on the first communication link based at least in part on the one or more instructions received from the at least one STA; 19. The device of any one or more of clauses 1-18, further configured to: 20. A method for wireless communication by a device, comprising: transmitting an indication of an extended synchronization mode to at least one wireless station (STA) over a first communication link associated with a first access point (AP) of the device; transmitting a plurality of synchronization frames during an extended synchronization mode on the first communication link more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between a first AP and a second AP of the device; A method comprising: 21. The method of clause 20, wherein at least one of the plurality of synchronization frames includes a fast initial link setup (FILS) discovery frame carrying a TSF value of the first AP. 22. A method according to any one or more of clauses 20-21, wherein the device comprises an AP multi-link device (MLD) including a first AP and a second AP, the first AP being associated with a first communication link and the second AP being associated with a second communication link occupying a different frequency band than the first communication link. 23. The method of any one or more of clauses 20-22, wherein the indication of the extended synchronization mode is sent based on an indication of latency sensitive traffic on at least the first communications link. twenty four. receiving a request from one or more STAs to enter an extended synchronous mode; 24. The method according to any one or more of clauses 20-23, further comprising: wherein the indication of the extended synchronization mode is sent upon request. twenty five. 25. The method of any one or more of clauses 20-24, further comprising indicating a start time of the extended synchronization mode to at least one STA. 26. Obtaining a TSF offset between a first AP and each of a plurality of STAs; indicating to each of a plurality of STAs whether participation in the enhanced synchronous mode is mandatory or voluntary based at least in part on the TSF offset; 26. The method according to any one or more of clauses 20 to 25, further comprising: 27. The method of clause 26, wherein whether participation in the extended synchronous mode is mandatory or voluntary for at least some of the multiple STAs is further based on an indication of latency-sensitive traffic on the first communications link. 28. The method of any one or more of clauses 20-27, wherein the extended synchronization mode is established along with one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs scheduled on the first communications link. 29. indicating to at least one STA whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device; 29. The method of any one or more of clauses 20-28, further comprising: 30. A frame, an amount of clock drift between the at least one STA and the first AP during each beacon interval; Whether at least one STA is participating in the enhanced synchronization mode, At least one STA receives a beacon frame on a first communication link or on a second communication link associated with a second AP; or a frequency at which at least one STA receives a beacon frame or a synchronization frame indicating the TSF information of the first AP; receiving a frame from at least one STA indicating one or more of: scheduling one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs for latency sensitive traffic on the first communication link based at least in part on the one or more indications received from the at least one STA; 30. The method of any one or more of clauses 20-29, further comprising: 31. At least one processor; at least one memory communicatively coupled to the at least one processor and storing processor-readable code; A device comprising: The processor-readable code, when executed by at least one processor, receiving an indication of an enhanced synchronization mode from a first access point (AP) of an AP multi-link device (MLD) over a first communication link associated with the first AP; receiving a plurality of synchronization frames during an extended synchronization mode on the first communication link more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between the first AP and the second AP of the AP MLD; The device is configured as follows: 32. The device of clause 31, wherein at least one of the plurality of synchronization frames includes a fast initial link setup (FILS) discovery frame carrying a TSF value of the first AP. 33. A device described in any one or more of clauses 31-32, wherein the time period between successive reception of a synchronization frame is approximately 20 milliseconds. 34. A device according to any one or more of clauses 31-33, wherein a plurality of synchronization frames are received at a data rate greater than a basic data rate associated with beacon frame transmissions on the first communications link. 35. A device described in any one or more of clauses 31 to 34, wherein the instruction is conveyed in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame received on the first communications link. 36. A device described in any one or more of clauses 31-35, wherein the indication of the extended synchronization mode is received based on an indication of latency-sensitive traffic on at least the first communications link. 37. Execution of processor-readable code Send a request to the AP MLD to start the extended synchronous mode, 37. The device of any one or more of clauses 31-36, further configured such that an indication of the extended synchronization mode is received upon request. 38. Execution of processor-readable code Receive an indication of the start time of the enhanced synchronization mode from the AP MLD, 38. The device of any one or more of clauses 31 to 37, further configured to: 39. The device of clause 38, wherein the indicated start time is conveyed in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame received on the first communications link. 40. Execution of processor-readable code receiving an indication from the AP MLD of whether participation in the enhanced synchronous mode is mandatory or voluntary for the device based at least in part on a TSF offset between the first AP and each of the plurality of STAs; 40. The device of any one or more of clauses 31 to 39, further configured to: 41. The device of clause 40, wherein whether participation in the extended synchronous mode is mandatory or voluntary for the device is further based on an indication of latency-sensitive traffic on the first communications link. 42. The device of any one or more of clauses 31-41, wherein the extended synchronization mode is established along with one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs scheduled on the first communications link. 43. Execution of processor-readable code receiving an indication from the AP MLD of whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device; 43. The device of any one or more of clauses 31 to 42, further configured to: 44. The device of clause 43, wherein an indication of a common clock or common TSF value across the device's first AP and second AP is carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a synchronization frame. 45. Execution of processor-readable code A frame, the amount of clock drift between the device and the first AP during each beacon interval; Whether the device is participating in enhanced sync mode, The device receives a beacon frame on either the first communication link or on a second communication link associated with a second AP; or how often the device receives a beacon frame or a synchronization frame indicating the TSF information of the first AP; sending a frame to the AP MLD indicating one or more of: receiving from the AP MLD an indication of one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs for latency sensitive traffic on the first communication link based at least in part on the one or more indications provided by the device; 45. The device of any one or more of clauses 31 to 44, further configured to: 46. ​​A method for wireless communication by a device, comprising: receiving an indication of an enhanced synchronization mode from a first access point (AP) of an AP multi-link device (MLD) over a first communication link associated with the first AP; receiving a plurality of synchronization frames during an extended synchronization mode on the first communication link more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between the first AP and the second AP of the AP MLD; A method comprising: 47. The method of clause 46, wherein at least one of the plurality of synchronization frames includes a fast initial link setup (FILS) discovery frame carrying a TSF value of the first AP. 48. The method of any one or more of clauses 46-47, wherein the time period between successive transmissions of the synchronization frame is about 20 milliseconds. 49. The method of any one or more of clauses 46-48, wherein the plurality of synchronization frames are received at a data rate greater than a basic data rate associated with beacon frame transmissions on the first communications link. 50. The method of any one or more of clauses 46-49, wherein the indication is conveyed in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame received on the first communications link. 51. The method of any one or more of clauses 46-50, wherein an indication of the extended synchronous mode is received based on an indication of latency sensitive traffic on at least the first communications link. 52. Sending a request to the AP MLD to enter the extended synchronous mode; 52. The method of any one or more of clauses 46-51, further comprising: wherein the indication of the extended synchronization mode is received upon request. 53. receiving an indication of a start time of an extended synchronous mode from an AP MLD; 53. The method of any one or more of clauses 46-52, further comprising: 54. The method of clause 53, wherein the indicated start time is conveyed in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame received on the first communications link. 55. receiving an indication from the AP MLD of whether participation in the enhanced synchronous mode is mandatory or voluntary for the device based at least in part on a TSF offset between the first AP and each of the plurality of STAs; 55. The method of any one or more of clauses 46-54, further comprising: 56. The method of clause 55, wherein whether participation in the extended synchronous mode is mandatory or voluntary for the device is further based on an indication of latency sensitive traffic on the first communications link. 57. The method of any one or more of clauses 46-56, wherein the extended synchronization mode is established along with one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs scheduled on the first communications link. 58. receiving an indication from the AP MLD of whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device; 58. The method according to any one or more of clauses 46 to 57, further comprising: 59. The method of clause 58, wherein an indication of a common clock or common TSF value across the first AP and the second AP of the device is carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a synchronization frame. 60. A frame, the amount of clock drift between the device and the first AP during each beacon interval; Whether the device is participating in enhanced sync mode, The device receives a beacon frame on either the first communication link or on a second communication link associated with a second AP; or how often the device receives a beacon frame or a synchronization frame indicating the TSF information of the first AP; sending a frame to the AP MLD indicating one or more of: receiving from the AP MLD an indication of one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs for latency sensitive traffic on the first communication link based at least in part on the one or more indications provided by the device; 60. The method of any one or more of clauses 46-59, further comprising:

[0137]

[0156] 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 encompass 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, b, and c. As used herein, "based on" is intended to be interpreted in an inclusive sense, unless expressly indicated otherwise. For example, "based on" may be used interchangeably with "based at least in part on," unless expressly indicated otherwise. Specifically, whatever "based on 'a'" or "based at least in part on 'a'" may be based only on "a" or based on a combination of "a" and one or more other factors, conditions, or information, unless the phrase refers to "based only on 'a'" or an equivalent in context.

[0138]

[0157] The various example components, logic, logic blocks, modules, circuits, operations, and algorithmic processes described with respect to implementations disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware, or software, including the structures disclosed herein and structural equivalents thereof. The interchangeability of hardware, firmware, and software has been described generally in terms of functionality and illustrated in the various example components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware, firmware, or software depends on the particular application and design constraints imposed on the overall system.

[0139]

[0158] Various modifications of the implementations described in this disclosure may be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the spirit or scope of the present disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with the present disclosure, the principles and novel features disclosed herein.

[0140]

[0159] Additionally, various features described herein in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations separately or in any suitable subcombination. Thus, although features may be described above as working in a particular combination, and may even initially be claimed as such, in some cases, one or more features from the claimed combination may be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0141]

[0160] Similarly, although operations are illustrated in the figures in a particular order, this should not be understood as requiring such operations to be performed in the particular order or sequential order shown, or that all of the operations shown be performed, to achieve a desired result. Furthermore, the figures may generally illustrate another exemplary process in the form of a flow diagram or flow chart. However, other operations not shown may be incorporated into the generally illustrated exemplary process. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. In some situations, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the program components and systems described may generally be integrated together in a single software product or packaged into multiple software products.

Claims

1. At least one processor; at least one memory communicatively coupled to the at least one processor and storing processor-readable code; A device comprising: The processor readable code, when executed by the at least one processor, Transmitting an indication of an extended synchronization mode to at least one wireless station (STA) over a first communication link associated with a first access point (AP) of the device; transmitting a plurality of synchronization frames on the first communication link during the extended synchronization mode more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between the first AP and a second AP of the device; The device is configured as follows:

2. The device of claim 1 , wherein at least one of the plurality of synchronization frames includes a Fast Initial Link Setup (FILS) discovery frame that carries a TSF value of the first AP.

3. The device of claim 1 , wherein the time period between successive transmissions of the synchronization frames is approximately 20 milliseconds.

4. The device of claim 1 , wherein the plurality of synchronization frames are transmitted at a data rate that is greater than a fundamental data rate associated with beacon frame transmissions on the first communications link.

5. 2. The device of claim 1, wherein the device comprises an AP multi-link device (MLD) including the first AP and the second AP, the first AP being associated with the first communication link and the second AP being associated with a second communication link occupying a different frequency band than the first communication link.

6. 2. The device of claim 1, wherein the indication is conveyed in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame transmitted on the first communications link.

7. Execution of the processor readable code comprises: in response to an indication of timing synchronization between the first AP and each of a plurality of STAs participating in the extended synchronization mode, exiting the extended synchronization mode. The device of claim 1 , further configured to:

8. 8. The device of claim 7, wherein the exit of the extended synchronous mode is further based on an indication of timing synchronization between the second AP and each of the multiple STAs participating in the extended synchronous mode.

9. 10. The device of claim 1, wherein the indication of the extended synchronization mode is sent based on at least an indication of latency-sensitive traffic on the first communications link.

10. Execution of the processor readable code comprises: receiving a request from one or more STAs to initiate the extended synchronous mode; 2. The device of claim 1, further configured to:

11. Execution of the processor readable code comprises: indicating a start time of the extended synchronous mode to the at least one STA; The device of claim 1 , further configured to:

12. 12. The device of claim 11, wherein the indicated start time is carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame transmitted on the first communications link.

13. Execution of the processor readable code comprises: Obtaining a TSF offset between the first AP and each of a plurality of STAs; indicating to each of a plurality of STAs whether participation in the extended synchronous mode is mandatory or voluntary based at least in part on the TSF offset; The device of claim 1 , further configured to:

14. 14. The device of claim 13, wherein whether participation in the extended synchronous mode is mandatory or voluntary for at least some of the plurality of STAs is further based on an indication of latency-sensitive traffic on the first communications link.

15. 2. The device of claim 1, wherein the extended synchronization mode is established along with one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs scheduled on the first communication link.

16. Execution of the processor readable code comprises: indicating to the at least one STA whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the device; The device of claim 1 , further configured to:

17. 17. The device of claim 16, wherein the indication of the common clock or the common TSF value across the first AP and the second AP of the device is carried in one or more of a beacon frame, a probe response frame, a broadcast action frame, or the synchronization frame.

18. Execution of the processor readable code comprises: rejecting association requests from STAs that do not support the extended synchronization mode during a time period starting before a start time of the extended synchronization mode. The device of claim 1 , further configured to:

19. Execution of the processor readable code comprises: A frame, an amount of clock drift between the at least one STA and the first AP during each beacon interval; whether the at least one STA is participating in the extended synchronous mode; the at least one STA receives a beacon frame over the first communication link or over a second communication link associated with the second AP; or a frequency at which the at least one STA receives a beacon frame or a synchronization frame indicating TSF information of the first AP; receiving a frame from the at least one STA indicating one or more of: scheduling one or more target wake time (TWT) service periods (SPs) or one or more restricted TWT (r-TWT) SPs for latency sensitive traffic on the first communications link based at least in part on the one or more indications received from the at least one STA; The device of claim 1 , further configured to:

20. 1. A method for wireless communication by a device, comprising: transmitting an indication of an extended synchronization mode to at least one wireless station (STA) over a first communication link associated with a first access point (AP) of the device; transmitting a plurality of synchronization frames on the first communication link during the extended synchronization mode more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between the first AP and a second AP of the device; A method comprising:

21. At least one processor; at least one memory communicatively coupled to the at least one processor and storing processor-readable code; A device comprising: The processor readable code, when executed by the at least one processor, receiving an indication of an extended synchronization mode from a first access point (AP) of an AP multi-link device (MLD) over a first communication link associated with the first AP; receiving a plurality of synchronization frames on the first communication link during the extended synchronization mode more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between the first AP and a second AP of the AP MLD; The device is configured as follows:

22. 22. The device of claim 21, wherein at least one of the plurality of synchronization frames includes a Fast Initial Link Setup (FILS) discovery frame carrying a TSF value of the first AP.

23. 22. The device of claim 21, wherein the time period between successive receipt of the synchronization frames is approximately 20 milliseconds.

24. 22. The device of claim 21, wherein the plurality of synchronization frames are received at a data rate that is greater than a fundamental data rate associated with beacon frame transmissions on the first communications link.

25. 22. The device of claim 21, wherein the indication is conveyed in one or more of a beacon frame, a probe response frame, a broadcast action frame, or a target wake time (TWT) response frame received on the first communications link.

26. 22. The device of claim 21, wherein the indication of the extended synchronization mode is received based on an indication of latency sensitive traffic on at least the first communications link.

27. Execution of the processor readable code comprises: sending a request to the AP MLD to initiate the extended synchronous mode; 22. The device of claim 21, further configured to:

28. Execution of the processor readable code comprises: receiving an indication of a start time of the extended synchronous mode from the AP MLD; 22. The device of claim 21, further configured to:

29. Execution of the processor readable code comprises: receiving an indication from the AP MLD of whether the first AP and the second AP share a common clock or a common TSF value across the first AP and the second AP of the AP MLD; 22. The device of claim 21, further configured to:

30. 1. A method for wireless communication by a device, comprising: receiving an indication of an enhanced synchronization mode from a first access point (AP) of an AP multi-link device (MLD) over a first communication link associated with the first AP; receiving a plurality of synchronization frames during the extended synchronization mode on the first communication link more frequently than target beacon transmission times (TBTTs) associated with the first communication link, each of the plurality of synchronization frames indicating a timing synchronization function (TSF) offset between the first AP and a second AP of the AP MLD; A method comprising:

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