TWT OPERATION IN WIRELESS NETWORKS

An access point (AP) affiliated with a non-simultaneous transmit and receive (NSTR) mobile AP multi-link device (MLD) and operating on a primary link may advertise a broadcast target wake time (TWT) schedule for the other AP affiliated with the same NSTR mobile AP MLD and operating on a nonprimary link by including a TWT element comprising a corresponding broadcast TWT parameter set field in the STA profile field of the Per-STA profile subelement of the basic multi-link element corresponding to the AP operating on the nonprimary link carried in beacon frames and/or probe response frame that it transmits on the primary link.

TECHNICAL FIELD

This disclosure relates generally to a wireless communication system, and more particularly to, for example, but not limited to, a target wake time (TWT) operation in wireless communication systems.

BACKGROUND

Wireless local area network (WLAN) technology has evolved toward increasing data rates and continues its growth in various markets such as home, enterprise and hotspots over the years since the late 1990s. WLAN allows devices to access the internet in the 2.4 GHZ, 5 GHZ, 6 GHz or 60 GHz frequency bands. WLANs are based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standards. IEEE 802.11 family of standards aims to increase speed and reliability and to extend the operating range of wireless networks.

WLAN devices are increasingly required to support a variety of delay-sensitive applications or real-time applications such as augmented reality (AR), robotics, artificial intelligence (AI), cloud computing, and unmanned vehicles. To implement extremely low latency and extremely high throughput required by such applications, multi-link operation (MLO) has been suggested for the WLAN. The WLAN is formed within a limited area such as a home, school, apartment, or office building by WLAN devices. Each WLAN device may have one or more stations (STAs) such as the access point (AP) STA and the non-access-point (non-AP) STA.

The MLO may enable a non-AP multi-link device (MLD) to set up multiple links with an AP MLD. Each of multiple links may enable channel access and frame exchanges between the non-AP MLD and the AP MLD independently, which may reduce latency and increase throughput.

The description set forth in the background section should not be assumed to be prior art merely because it is set forth in the background section. The background section may describe aspects or embodiments of the present disclosure.

SUMMARY

An aspect of the present disclosure provides an access point (AP) multi-link device (MLD) associated with a non-AP MLD in a wireless network. The AP MLD comprises at least two APs, each AP being affiliated with the AP MLD, and a processor coupled to the at least two Aps. The processor is configured to advertise, by a first AP affiliated with the AP MLD and operating on a primary link established between the first AP and a first STA affiliated with the non-AP MLD, a broadcast target wake time (TWT) schedule for a second AP affiliated with the AP MLD and operating on a non-primary link established between the second AP and a second STA affiliated with the non-AP MLD by including a TWT element comprising a broadcast TWT parameter set field corresponding to the second AP operating on the non-primary link in a broadcast frame via the primary link.

In some embodiments, the broadcast TWT parameter set field is included in a station (STA) profile field of a Per-STA profile subelement of a basic multi-link element.

In some embodiments, the broadcast frame is a beacon frame or a probe response frame.

In some embodiments, a value in a broadcast target wake time (TWT) persistence subfield corresponding to the broadcast TWT schedule is in reference to a most recent target beacon transmission time (TBTT) and beacon interval indicated by the first AP operating on the primary link.

In some embodiments, the AP MLD is a non-simultaneous transmit and receive (NSTR) mobile AP MLD.

In some embodiments, the processor is further configured to receive, by the second AP from the second STA, a TWT request to join the broadcast TWT schedule.

In some embodiments, the first AP is not in a multiple basic service set identifier (BSSID) set or the first AP corresponds to a transmitted BSSID in a multiple BSSID set.

In some embodiments, the primary link and the second link are a non-simultaneous transmit and receive (NSTR) link pair.

An aspect of the present disclosure provides an access point (AP) multi-link device (MLD) associated with a non-AP MLD in a wireless network. The AP MLD comprises at least two APs, each AP being affiliated with the AP MLD, and a processor coupled to the at least two Aps. The processor is configured to include, by a first AP affiliated with the AP MLD, a basic multi-link element for the AP MLD in a broadcast frame, wherein the basic multi-link element does not include a link information field unless the AP MLD is a non-simultaneous transmit and receive (NSTR) mobile AP MLD and the firs AP is operating on a primary link established between the first AP and a first STA affiliated with the non-AP MLD, and advertises a broadcast target wake time (TWT) schedule for a second AP affiliated with the AP MLD and operating on a non-primary link. The processor is configured to transmit, by the first AP affiliated with AP MLD, the broadcast frame.

In some embodiments, the first AP is not in a multiple basic service set identifier (BSSID) set or the first AP corresponds to a transmitted BSSID in a multiple BSSID set.

In some embodiments, the broadcast frame is a beacon frame or a probe response frame.

In some embodiments, the probe response frame is not in a multi-link probe response that the first AP transmits.

In some embodiments, when the first AP is affiliated with the NSTR mobile AP MLD and operating on the primary link and the first AP advertises the broadcast TWT schedule for the second AP, a station (STA) profile in the link formation field of the basic multi-link element only includes a broadcast TWT element for the second AP operating on the non-primary link.

An aspect of the present disclosure provides a non-access point (AP) multi-link device (MLD) associated with an AP MLD in a wireless network. The non-AP MLD comprises at least two STAs, each STA being affiliated with the non-AP MLD, and a processor coupled to the at least two STAs. The processor is configured to receive, by a first STA affiliated with the non-AP MLD and operating on a primary link established between the first STA and a first AP affiliated with the AP MLD, a broadcast frame via the primary link, the broadcast frame advertising a broadcast target wake time (TWT) schedule for a second AP affiliated with the AP MLD and operating on a non-primary link established between the second STA and an second AP affiliated with the AP MLD by including a TWT element comprising a broadcast TWT parameter set field corresponding to the second AP operating on the non-primary link. The processor is configured to transmit, by the second STA affiliated with the non-AP MLD and operating on the non-primary link, a TWT request to join the broadcast TWT schedule.

In some embodiments, the broadcast TWT parameter set field is included in a STA profile field of a Per-STA Profile subelement of a basic multi-link element.

In some embodiments, the broadcast frame is a beacon frame or a probe response frame.

In some embodiments, a value in a broadcast TWT persistence subfield corresponding to the broadcast TWT schedule is in reference to a most recent target beacon transmission time (TBTT) and beacon interval indicated by the first AP operating on the primary link.

In some embodiments, the AP MLD is a non-simultaneous transmit and receive (NSTR) mobile AP MLD.

In some embodiments, the first AP is not in a multiple basic service set identifier (BSSID) set or the first AP corresponds to a transmitted BSSID in a multiple BSSID set.

In some embodiments, the primary link and the second link are a non-simultaneous transmit and receive (NSTR) link pair.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with the appended drawings, is intended as a description of various implementations and is not intended to represent the only implementations in which the subject technology may be practiced. Rather, the detailed description includes specific details for the purpose of providing a thorough understanding of the inventive subject matter. As those skilled in the art would realize, the described implementations may be modified in various ways, all without departing from the scope of the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements.

The following description is directed to certain implementations for the purpose of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The examples in this disclosure are based on WLAN communication according to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, including IEEE 802.11be standard and any future amendments to the IEEE 802.11 standard. However, the described embodiments may be implemented in any device, system or network that is capable of transmitting and receiving radio frequency (RF) signals according to the IEEE 802.11 standard, the Bluetooth standard, Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1×EV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), 5G NR (New Radio), AMPS, or other known signals that are used to communicate within a wireless, cellular or internet of things (IoT) network, such as a system utilizing 3G, 4G, 5G, 6G, or further implementations thereof, technology.

Multi-link operation (MLO) is a key feature that is currently being developed by the standards body for next generation extremely high throughput (EHT) Wi-Fi systems in IEEE 802.11be. The Wi-Fi devices that support MLO are referred to as multi-link devices (MLD). With MLO, it is possible for a non-AP MLD to discover, authenticate, associate, and set up multiple links with an AP MLD. Channel access and frame exchange is possible on each link between the AP MLD and non-AP MLD.

FIG.1shows an example of a wireless network100in accordance with an embodiment. The embodiment of the wireless network100shown inFIG.1is for illustrative purposes only. Other embodiments of the wireless network100could be used without departing from the scope of this disclosure.

As shown inFIG.1, the wireless network100may include a plurality of wireless communication devices. Each wireless communication device may include one or more stations (STAs). The STA may be a logical entity that is a singly addressable instance of a medium access control (MAC) layer and a physical (PHY) layer interface to the wireless medium. The STA may be classified into an access point (AP) STA and a non-access point (non-AP) STA. The AP STA may be an entity that provides access to the distribution system service via the wireless medium for associated STAs. The non-AP STA may be a STA that is not contained within an AP-STA. For the sake of simplicity of description, an AP STA may be referred to as an AP and a non-AP STA may be referred to as a STA. In the example ofFIG.1, APs101and103are wireless communication devices, each of which may include one or more AP STAs. In such embodiments, APs101and103may be AP multi-link device (MLD). Similarly, STAs111-114are wireless communication devices, each of which may include one or more non-AP STAs. In such embodiments, STAs111-114may be non-AP MLD.

The APs101and103communicate with at least one network130, such as the Internet, a proprietary Internet Protocol (IP) network, or other data network. The AP101provides wireless access to the network130for a plurality of stations (STAs)111-114with a coverage are 120 of the AP101. The APs101and103may communicate with each other and with the STAs using Wi-Fi or other WLAN communication techniques.

InFIG.1, dotted lines show the approximate extents of the coverage area120and125of APs101and103, which are shown as approximately circular for the purposes of illustration and explanation. It should be clearly understood that coverage areas associated with APs, such as the coverage areas120and125, may have other shapes, including irregular shapes, depending on the configuration of the APs.

As described in more detail below, one or more of the APs may include circuitry and/or programming for management of MU-MIMO and OFDMA channel sounding in WLANs. AlthoughFIG.1shows one example of a wireless network100, various changes may be made toFIG.1. For example, the wireless network100could include any number of APs and any number of STAs in any suitable arrangement. Also, the AP101could communicate directly with any number of STAs and provide those STAs with wireless broadband access to the network130. Similarly, each AP101and103could communicate directly with the network130and provides STAs with direct wireless broadband access to the network130. Further, the APs101and/or103could provide access to other or additional external networks, such as external telephone networks or other types of data networks.

FIG.2Ashows an example of AP101in accordance with an embodiment. The embodiment of the AP101shown inFIG.2Ais for illustrative purposes, and the AP103ofFIG.1could have the same or similar configuration. However, APs come in a wide range of configurations, andFIG.2Adoes not limit the scope of this disclosure to any particular implementation of an AP.

As shown inFIG.2A, the AP101may include multiple antennas204a-204n, multiple radio frequency (RF) transceivers209a-209n, transmit (TX) processing circuitry214, and receive (RX) processing circuitry219. The AP101also may include a controller/processor224, a memory229, and a backhaul or network interface234. The RF transceivers209a-209nreceive, from the antennas204a-204n, incoming RF signals, such as signals transmitted by STAs in the network100. The RF transceivers209a-209ndown-convert the incoming RF signals to generate intermediate (IF) or baseband signals. The IF or baseband signals are sent to the RX processing circuitry219, which generates processed baseband signals by filtering, decoding, and/or digitizing the baseband or IF signals. The RX processing circuitry219transmits the processed baseband signals to the controller/processor224for further processing.

The TX processing circuitry214receives analog or digital data (such as voice data, web data, e-mail, or interactive video game data) from the controller/processor224. The TX processing circuitry214encodes, multiplexes, and/or digitizes the outgoing baseband data to generate processed baseband or IF signals. The RF transceivers209a-209nreceive the outgoing processed baseband or IF signals from the TX processing circuitry214and up-converts the baseband or IF signals to RF signals that are transmitted via the antennas204a-204n.

The controller/processor224can include one or more processors or other processing devices that control the overall operation of the AP101. For example, the controller/processor224could control the reception of uplink signals and the transmission of downlink signals by the RF transceivers209a-209n, the RX processing circuitry219, and the TX processing circuitry214in accordance with well-known principles. The controller/processor224could support additional functions as well, such as more advanced wireless communication functions. For instance, the controller/processor224could support beam forming or directional routing operations in which outgoing signals from multiple antennas204a-204nare weighted differently to effectively steer the outgoing signals in a desired direction. The controller/processor224could also support OFDMA operations in which outgoing signals are assigned to different subsets of subcarriers for different recipients (e.g., different STAs111-114). Any of a wide variety of other functions could be supported in the AP101by the controller/processor224including a combination of DL MU-MIMO and OFDMA in the same transmit opportunity. In some embodiments, the controller/processor224may include at least one microprocessor or microcontroller. The controller/processor224is also capable of executing programs and other processes resident in the memory229, such as an OS. The controller/processor224can move data into or out of the memory229as required by an executing process.

The controller/processor224is also coupled to the backhaul or network interface234. The backhaul or network interface234allows the AP101to communicate with other devices or systems over a backhaul connection or over a network. The interface234could support communications over any suitable wired or wireless connection(s). For example, the interface234could allow the AP101to communicate over a wired or wireless local area network or over a wired or wireless connection to a larger network (such as the Internet). The interface234may include any suitable structure supporting communications over a wired or wireless connection, such as an Ethernet or RF transceiver. The memory229is coupled to the controller/processor224. Part of the memory229could include a RAM, and another part of the memory229could include a Flash memory or other ROM.

As described in more detail below, the AP101may include circuitry and/or programming for management of channel sounding procedures in WLANs. AlthoughFIG.2Aillustrates one example of AP101, various changes may be made toFIG.2A. For example, the AP101could include any number of each component shown inFIG.2A. As a particular example, an AP could include a number of interfaces234, and the controller/processor224could support routing functions to route data between different network addresses. As another example, while shown as including a single instance of TX processing circuitry214and a single instance of RX processing circuitry219, the AP101could include multiple instances of each (such as one per RF transceiver). Alternatively, only one antenna and RF transceiver path may be included, such as in legacy APs. Also, various components inFIG.2Acould be combined, further subdivided, or omitted and additional components could be added according to particular needs.

As shown inFIG.2A, in some embodiment, the AP101may be an AP MLD that includes multiple APs202a-202n. Each AP202a-202nis affiliated with the AP MLD101and includes multiple antennas204a-204n, multiple radio frequency (RF) transceivers209a-209n, transmit (TX) processing circuitry214, and receive (RX) processing circuitry219. Each APs202a-202nmay independently communicate with the controller/processor224and other components of the AP MLD101.FIG.2Ashows that each AP202a-202nhas separate multiple antennas, but each AP202a-202ncan share multiple antennas204a-204nwithout needing separate multiple antennas. Each AP202a-202nmay represent a physical (PHY) layer and a lower media access control (MAC) layer.

FIG.2Bshows an example of STA111in accordance with an embodiment. The embodiment of the STA111shown inFIG.2Bis for illustrative purposes, and the STAs111-114ofFIG.1could have the same or similar configuration. However, STAs come in a wide variety of configurations, andFIG.2Bdoes not limit the scope of this disclosure to any particular implementation of a STA.

As shown inFIG.2B, the STA111may include antenna(s)205, a RF transceiver210, TX processing circuitry215, a microphone220, and RX processing circuitry225. The STA111also may include a speaker230, a controller/processor240, an input/output (I/O) interface (IF)245, a touchscreen250, a display255, and a memory260. The memory260may include an operating system (OS)261and one or more applications262.

The RF transceiver210receives, from the antenna(s)205, an incoming RF signal transmitted by an AP of the network100. The RF transceiver210down-converts the incoming RF signal to generate an IF or baseband signal. The IF or baseband signal is sent to the RX processing circuitry225, which generates a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. The RX processing circuitry225transmits the processed baseband signal to the speaker230(such as for voice data) or to the controller/processor240for further processing (such as for web browsing data).

The TX processing circuitry215receives analog or digital voice data from the microphone220or other outgoing baseband data (such as web data, e-mail, or interactive video game data) from the controller/processor240. The TX processing circuitry215encodes, multiplexes, and/or digitizes the outgoing baseband data to generate a processed baseband or IF signal. The RF transceiver210receives the outgoing processed baseband or IF signal from the TX processing circuitry215and up-converts the baseband or IF signal to an RF signal that is transmitted via the antenna(s)205.

The controller/processor240can include one or more processors and execute the basic OS program261stored in the memory260in order to control the overall operation of the STA111. In one such operation, the controller/processor240controls the reception of downlink signals and the transmission of uplink signals by the RF transceiver210, the RX processing circuitry225, and the TX processing circuitry215in accordance with well-known principles. The controller/processor240can also include processing circuitry configured to provide management of channel sounding procedures in WLANs. In some embodiments, the controller/processor240may include at least one microprocessor or microcontroller.

The controller/processor240is also capable of executing other processes and programs resident in the memory260, such as operations for management of channel sounding procedures in WLANs. The controller/processor240can move data into or out of the memory260as required by an executing process. In some embodiments, the controller/processor240is configured to execute a plurality of applications262, such as applications for channel sounding, including feedback computation based on a received null data packet announcement (NDPA) and null data packet (NDP) and transmitting the beamforming feedback report in response to a trigger frame (TF). The controller/processor240can operate the plurality of applications262based on the OS program261or in response to a signal received from an AP. The controller/processor240is also coupled to the I/O interface245, which provides STA111with the ability to connect to other devices such as laptop computers and handheld computers. The I/O interface245is the communication path between these accessories and the main controller/processor240.

The controller/processor240is also coupled to the input250(such as touchscreen) and the display255. The operator of the STA111can use the input250to enter data into the STA111. The display255may be a liquid crystal display, light emitting diode display, or other display capable of rendering text and/or at least limited graphics, such as from web sites. The memory260is coupled to the controller/processor240. Part of the memory260could include a random access memory (RAM), and another part of the memory260could include a Flash memory or other read-only memory (ROM).

AlthoughFIG.2Bshows one example of STA111, various changes may be made toFIG.2B. For example, various components inFIG.2Bcould be combined, further subdivided, or omitted and additional components could be added according to particular needs. In particular examples, the STA111may include any number of antenna(s)205for MIMO communication with an AP101. In another example, the STA111may not include voice communication or the controller/processor240could be divided into multiple processors, such as one or more central processing units (CPUs) and one or more graphics processing units (GPUs). Also, whileFIG.2Billustrates the STA111configured as a mobile telephone or smartphone, STAs could be configured to operate as other types of mobile or stationary devices.

As shown inFIG.2B, in some embodiment, the STA111may be a non-AP MLD that includes multiple STAs203a-203n. Each STA203a-203nis affiliated with the non-AP MLD111and includes an antenna(s)205, a RF transceiver210, TX processing circuitry215, and RX processing circuitry225. Each STAs203a-203nmay independently communicate with the controller/processor240and other components of the non-AP MLD111.FIG.2Bshows that each STA203a-203nhas a separate antenna, but each STA203a-203ncan share the antenna205without needing separate antennas. Each STA203a-203nmay represent a physical (PHY) layer and a lower media access control (MAC) layer.

FIG.3shows an example of multi-link communication operation in accordance with an embodiment. The multi-link communication operation may be usable in IEEE 802.11be standard and any future amendments to IEEE 802.11 standard. InFIG.3, an AP MLD310may be the wireless communication device101and103inFIG.1and a non-AP MLD220may be one of the wireless communication devices111-114inFIG.1.

As shown inFIG.3, the AP MLD310may include a plurality of affiliated APs, for example, including AP 1, AP 2, and AP 3. Each affiliated AP may include a PHY interface to wireless medium (Link 1, Link 2, or Link 3). The AP MLD310may include a single MAC service access point (SAP)318through which the affiliated APs of the AP MLD310communicate with a higher layer (Layer 3 or network layer). Each affiliated AP of the AP MLD310may have a MAC address (lower MAC address) different from any other affiliated APs of the AP MLD310. The AP MLD310may have a MLD MAC address (upper MAC address) and the affiliated APs share the single MAC SAP318to Layer 3. Thus, the affiliated APs share a single IP address, and Layer 3 recognizes the AP MLD310by assigning the single IP address.

The non-AP MLD320may include a plurality of affiliated STAs, for example, including STA 1, STA 2, and STA 3. Each affiliated STA may include a PHY interface to the wireless medium (Link 1, Link 2, or Link 3). The non-AP MLD320may include a single MAC SAP328through which the affiliated STAs of the non-AP MLD320communicate with a higher layer (Layer 3 or network layer). Each affiliated STA of the non-AP MLD320may have a MAC address (lower MAC address) different from any other affiliated STAs of the non-AP MLD320. The non-AP MLD320may have a MLD MAC address (upper MAC address) and the affiliated STAs share the single MAC SAP328to Layer 3. Thus, the affiliated STAs share a single IP address, and Layer 3 recognizes the non-AP MLD320by assigning the single IP address.

The AP MLD310and the non-AP MLD320may set up multiple links between their affiliate APs and STAs. In this example, the AP 1 and the STA 1 may set up Link 1 which operates in 2.4 GHz band. Similarly, the AP 2 and the STA 2 may set up Link 2 which operates in 5 GHZ band, and the AP 3 and the STA 3 may set up Link 3 which operates in 6 GHz band. Each link may enable channel access and frame exchange between the AP MLD310and the non-AP MLD320independently, which may increase date throughput and reduce latency. Upon associating with an AP MLD on a set of links (setup links), each non-AP device is assigned a unique association identifier (AID).

The following documents are hereby incorporated by reference in their entirety into the present disclosure as if fully set forth herein: i) IEEE 802.11-2020, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications” and ii) IEEE P802.11be/D3.0, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.”

Target wake time (TWT) operation is a feature of power management in WLAN networks. The TWT operation has been introduced in IEEE 802.11ah standard and later modified in IEEE 802.11ax standard. The TWT operation enables an AP to manage activity in the basic service set (BSS) to minimize contention between STAs and reduce the required wake times for STAs during the TWT operation. It can be achieved by allocating STAs to operate at non-overlapping times or frequencies and perform the frame exchange sequences in pre-scheduled service periods. In the TWT operation, a STA can wake up at pre-scheduled times that have been negotiated with an AP or another STA in the BSS. The STA does not need to be aware of TWT parameter values of other STAs within the BSS or of STAs in other BSSs. The STA does not need to be aware that a TWT service period (SP) is used to exchange frames with other STAs. Frames transmitted during a TWT SP can employ any PPDU (physical layer protocol data unit) format supported by the pair of STAs that have established the corresponding TWT agreement or TWT schedule, including, but not limited to, HE MU (high efficiency multi-user) PPDU, HE TB (high efficiency trigger based) PPDU.

IEEE 802.11 standard describes two types of TWT operations: individual TWT operation and broadcast TWT operation. In the individual TWT operation, an individual TWT agreement can be established between two STAs or between a STA and an AP. The negotiation for the individual TWT operation may occur between two STAs or between a STA and an AP on an individual basis. An AP may have TWT agreements with multiple STAs. Any changes in the TWT agreement between the AP and one STA do not affect the TWT agreement between the AP and other STAs.

On the other hand, the broadcast TWT operates in a membership-based approach. In broadcast TWT operation, an AP can set up a shared TWT session for a group of STAs. The AP is typically the controller of the broadcast TWT schedule. The non-AP STAs in the BSS can request membership in the broadcast TWT schedule, or the AP can send unsolicited response to a STA to make the STA a member of the broadcast TWT schedule that the AP maintains in the BSS. The AP may advertise and maintain multiple broadcast TWT schedules in the BSS. When a change is made to any broadcast TWT schedules in the BSS, it may affect all or some of STAs that are members of the corresponding broadcast TWT schedule.

An AP MLD is typically able to simultaneously transmit and receive frames over all of its links. However, the current version of IEEE 802.11be standard defines a special type of AP MLD, referred to as a ‘non-simultaneous transmit and receive (NSTR) mobile AP MLD,’ which is a mobile AP MLD having an NSTR link pair. In this disclosure, a mobile AP refers to AP that is capable of keeping its basic service set (BSS) operational while its location is changed. Two kinds of links are defined for the NSRT mobile AP MLD: primary link and non-primary link. A beacon frame or a probe response frame can only be sent over the primary link and cannot be sent over the non-primary link. Moreover, when transmitting a PPDU over the non-primary link, an AP affiliated with the NSTR mobile AP MLD that is operating on the non-primary link, or a non-AP STA affiliated with a non-AP MLD that is associated with the NSTR mobile AP MLD and operating on the non-primary link, needs to align the PPDU with a PPDU transmitted over the primary link.

FIG.4shows an example NSTR operation in accordance with an embodiment. The operation depicted inFIG.4is for illustration purposes and does not limit the scope of this disclosure to any particular implementations.

InFIG.4, an AP MLD410includes affiliated AP 1 and AP 2, and a non-AP MLD420includes affiliated STA 1 and STA 2. In this example ofFIG.4, the AP MLD410is an NSTR mobile AP MLD. An NSTR link pair is established between the AP MLD410and the non-AP MLD420. Specifically, a primary link is established between AP 1 and STA 1, while a non-primary link is established between AP 2 and STA 2. The AP MLD410and the non-AP MLD420exchanges PPDUs in both primary link and non-primary link. However, PPDUs transmitted on the non-primary link from AP 2 and STA 2 are aligned with PPDUs transmitted in the primary link.

According to the current WLAN system, a broadcast TWT schedule can be advertised by a TWT scheduling AP by including a corresponding TWT element in a beacon frame or a probe response frame that the TWT scheduling AP transmits. However, an AP affiliated with an NSTR mobile AP MLD and operating on the non-primary link does not transmit a beacon frame or a probe response frame. Therefore, in the current WLAN system, there is no mechanism to advertise a broadcast TWT schedule for the non-primary link of the NSTR mobile AP MLD.

This disclosure provides various example procedures for broadcast TWT operation with an NSTR mobile AP MLD.

In some embodiments, an AP affiliated with an NSTR mobile AP MLD and operating on a non-primary link may advertise a broadcast TWT schedule for the non-primary link by carrying an TWT element, comprising a corresponding broadcast TWT schedule, in a beacon frame and/or a probe response frame transmitted on a primary link. It is because there is no beaconing on the non-primary link of the NSTR mobile AP MLD. Therefore, the advertisement for the broadcast TWT schedule for the non-primary link can be made through the AP operating on the primary link at the NSTR mobile AP MLD.

FIG.5shows an example process for advertising a broadcast TWT schedule for an NSTR mobile AP MLD in accordance with an embodiment. For explanatory and illustration purposes, the example process500may be performed by AP 1 and AP 2 depicted inFIG.4. Although one or more operations are described or shown in particular sequential order, in other embodiments the operations may be rearranged in a different order, which may include performance of multiple operations in at least partially overlapping time periods.

Referring toFIGS.4and5, the process500may begin in operation501. In operation501, an NSTR mobile MLD (e.g., AP MLD410inFIG.4) intends to advertise a broadcast TWT schedule for a non-primary link.

In operation503, an AP affiliated with the NSTR mobile AP MLD and operating on the primary link (e.g., AP 1 inFIG.4) advertises the broadcast TWT schedule on the primary link on behalf of the AP affiliated with the same NSTR mobile AM MLD and operating on the non-primary link (e.g., AP 2 inFIG.4).

In some embodiments, a broadcast TWT schedule for a non-primary link can be advertised by including a corresponding TWT element in a Per-STA profile subelement transmitted on a primary link. Specifically, an AP affiliated with an NSTR mobile AP MLD and operating on a primary link may advertise a broadcast TWT schedule for an AP affiliated with the same NSTR mobile MLD and operating on a non-primary link. This can be achieved by including a TWT element comprising a corresponding broadcast TWT parameter set field in a STA profile field of a Per-STA profile subelement of a basic multi-link element. The corresponding broadcast TWT parameter set field corresponds to the AP operating on the non-primary link and is carried in a beacon frame and/or a probe response frame transmitted on the primary link. The value in the broadcast TWT persistence subfield corresponding to the broadcast TWT schedule may be in reference to the most recent target beacon transmission time (TBTT) and beacon interval (BI) indicated by the AP operating on the primary link.

FIG.6shows an example process for advertising a broadcast TWT schedule for an NSTR mobile AP MLD in accordance with an embodiment. For explanatory and illustration purposes, the example process600may be performed by AP 1 and AP 2 depicted inFIG.4. Although one or more operations are described or shown in particular sequential order, in other embodiments the operations may be rearranged in a different order, which may include performance of multiple operations in at least partially overlapping time periods. The process inFIG.6illustrates an example to advertise a broadcast TWT schedule for a non-primary link by including a corresponding TWT element in a Per-STA profile subelement transmitted on a primary link.

Referring toFIGS.4and6, the process600may begin in operation601. In operation601, an NSTR mobile MLD (e.g., AP MLD410inFIG.4) intends to advertise a broadcast TWT schedule for a non-primary link.

In operation603, an AP affiliated with an NSTR mobile AP MLD and operating on a primary link (e.g., AP 1 inFIG.4) may advertise a broadcast TWT schedule for an AP affiliated with the same NSTR mobile MLD and operating on a non-primary link (e.g., AP 2 inFIG.4). This can be achieved by including a TWT element comprising a corresponding broadcast TWT parameter set field in a STA profile field of a Per-STA profile subelement within a link information (link info) field of a basic multi-link element. The corresponding broadcast TWT parameter set field corresponds to the AP operating on the non-primary link and is carried in a beacon frame and/or a probe response frame transmitted on the primary link.

In some embodiments, if an AP affiliated with an NSTR mobile AP MLD and operating on a primary link advertises a broadcast TWT schedule for an AP affiliated with the same NSTR mobile MLD and operating on a non-primary link. This can be achieved by including a TWT element, comprising a corresponding broadcast TWT parameter set field in a Per-STA profile field of a Per-STA Profile subelement of a basic multi-link element. The basic multi-link element corresponds to the AP operating on the non-primary link and is carried in a beacon frame or a probe response frame on the primary link. In this scenario, a timing field, such as a target wake time field, in the TWT element may be in reference to a TSF of the primary link. In another embodiment, the timing field in the TWT element may be in reference to the TSF of the non-primary link.

In some embodiments, an AP affiliated with an NSTR mobile AP MLD and operating on a primary link advertises a TWT schedule on the primary link that is an aligned schedule. Since the NSTR mobile AP MLD can have a maximum of two links (e.g., primary link and non-primary link), the advertisement of the aligned schedule on the primary link may mean that the TWT schedule is also available on the non-primary link.

In some embodiments, if an AP affiliated with an NSTR mobile AP MLD and operating on a primary link intends to advertise a broadcast TWT schedule for an AP affiliated with the same NSTR mobile AP MLD and operating on a non-primary link, the AP operating on the primary link may advertise the broadcast TWT schedule on the primary link and indicate that the broadcast TWT schedule is an aligned schedule, for example, by setting an Aligned subfield of a Request Type filed in a corresponding broadcast TWT parameter set field to 1. Since an NSTR mobile AP MLD can have a maximum of two links (primary link and non-primary link), a non-AP MLD associated with the NSTR mobile AP MLD that receives the advertisement of the aligned schedule, through a beacon frame or a probe response frame on the primary link, can uniquely identify the presence of the aligned TWT schedule on the non-primary link.

FIG.7shows an example format of the TWT element in accordance with an embodiment.

InFIG.7, the TWT element700may include an Element identifier (ID) field, a length field, a Control field, and a TWT Parameter Information field. The Element ID field may include information to identify the TWT element700. The Length field may indicate a length of the TWT element700.

The Control field may include a null data PPDU (physical layer protocol data unit) (NDP) Paging Indicator subfield, a Responder power management (PM) Mode subfield, a Negotiation Type subfield, a TWT Information Frame Disabled subfield, a Wake Duration Unit subfield, a Link 1D Bitmap Present subfield, and an OBSS R-TWT subfield. The NDP Paging Indicator subfield may indicate whether an NDP paging field is present or not in an Individual TWT Parameter Set field. The Responder PM Mode subfield may indicate the power management mode, such as active mode and power save (PS) mode. The negotiation Type subfield may indicate whether the information included in the TWT element is for the negotiation of parameters of broadcast or individual TWT or Wake TBTT (target beacon transmission time) interval. The MSB (most significant bit) of the Negotiation Type subfield is the Broadcast field which indicates if one or more Broadcast TWT Parameter Sets are contained in the TWT element. The TWT Information Frame Disabled subfield may indicate whether the reception of TWT information frame is disabled by the STA. The Wake Duration Unit subfield may indicate the unit of the Nominal Minimum TWT Wake Duration subfield in the Broadcast TWT Parameter Set field. The Link 1D Bitmap Present subfield may indicate the presence of the Link 1D Bitmap field in the Individual TWT Parameter Set field. The OBSS R-TWT subfield may indicate whether the R-TWT schedules corresponding to the Broadcast TWT Parameter Set fields in the TWT element are the R-TWT schedule of the neighboring BSS. When the OBSS R-TWT subfield is set to ‘1’, it may indicate that the R-TWT schedules in the TWT element are the R-TWT schedule of the neighboring BSS. Otherwise, it indicates that there is no neighboring BSS's R-TWT schedule in the TWT element.

The TWT Parameter information field includes an individual TWT parameter set field or one or more Broadcast TWT Parameter Set fields. For the convenience of description,FIG.7illustrates the Broadcast TWT Parameter Set fields. The Broadcast TWT Parameter Set field710may include a Request Type field, a Target Wake Time field, a Nominal Minimum TWT Wake Duration field, a TWT Wake Interval Mantissa field, a Broadcast TWT Info field, and an optional Restricted TWT traffic Info field.

The Request Type field of the Broadcast TWT Parameter Set field710can be used to indicate the presence of the aligned TWT schedule. Referring toFIG.7, the Request Type field includes a TWT Request subfield, a TWT Setup Command subfield, a Trigger subfield, a Last Broadcast Parameter Set subfield, a Flow Type subfield, a Broadcast TWT Recommendation subfield, a TWT Wake Interval Exponent subfield, and an Aligned subfield. The Request Type field may be usable for Broadcast TWT operation.

The TWT Request subfield may indicate if the transmitting STA is a TWT scheduling AP (or STA) or a TWT scheduled STA (or AP). The TWT Setup Command subfield may indicate the type of TWT command, such as Request TWT, Suggest TWT, Demand TWT, TWT Grouping, Accept TWT, Alternate TWT, Dictate TWT and Reject TWT. The Trigger subfield may indicate whether the TWT SP indicated by the TWT element includes triggering frames. The Last Broadcast Parameter Set subfield may indicate whether another Broadcast TWT Parameter Set field follows this Broadcast TWT Parameter Set field. The Flow Type subfield may indicate the type of interaction, for example, an announced TWT or an unannounced TWT between the TWT scheduled STA and the TWT scheduling AP at TWT. The Broadcast TWT Recommendation subfield may indicate recommendations on the types of frames that are transmitted by TWT scheduled STAs and TWT scheduling AP during the broadcast TWT SP. For instance, the types of frames may be PS-Poll and QoS Null frames, management frames, control response frames, or No constraints on the frame. The TWT Wake Interval Exponent subfield may indicate the value of the exponent of the TWT wake interval value. The Aligned subfield may indicate whether one or more of other links of the AP MLD have broadcast TWT schedules that are aligned with the corresponding schedule. More specifically, if the subfield is set to 1, it may indicate that there are one or more schedules on other links that are aligned with the TWT schedule identified by the Broadcast TWT Parameter Set field. Otherwise, the schedule is no such schedule on the other links. As discussed above, in some embodiments, if an AP affiliated with an NSTR mobile AP MLD and operating on a primary link intends to advertise a broadcast TWT schedule for an AP affiliated with the same NSTR mobile AP MLD and operating on a non-primary link, the AP operating on the primary link may advertise the broadcast TWT schedule on the primary link and indicate that the broadcast TWT schedule is an aligned schedule, for example, by setting an Aligned subfield of a Request Type filed in a corresponding broadcast TWT parameter set field to 1.

The Target Wake Time field may include an unsigned integer corresponding to a TSF (time synchronization function) time for the TWT scheduled STA to wake up. The Target Wake Time field may indicate the start time of the TWT service period (SP) on the corresponding link. The Nominal Minimum TWT Wake Duration field may indicate the minimum amount of time that the TWT scheduled STA is expected to be awake in order to complete the frame exchanges for the period of TWT wake interval. The TWT wake interval is the average time that the TWT scheduled STA expects to elapse between successive TWT SPs. The TWT Wake Interval Mantissa field may indicate the value of the mantissa of the TWT wake interval value. The Broadcast TWT Info field may include information related to the broadcast TWT, such as a restricted TWT traffic info present field, a restricted TWT schedule info field, a Broadcast TWT ID field and a Broadcast TWT Persistence field. The restricted TWT traffic info present field indicates whether the restricted TWT traffic info field is present. The restricted TWT schedule info field indicates whether an active R-TWT schedule is active. The Broadcast TWT ID field indicates a specific broadcast TWT for which the transmitting STA is providing TWT parameters. The Broadcast TWT persistence field indicates the number of TBTTs during which the Broadcast TWT SPs corresponding to this broadcast TWT parameter set are present.

FIG.8shows an example format of the multi-link element in accordance with an embodiment.

InFIG.8, the Multi-Link element800includes an Element identifier ID field, a length field, an Element ID Extension field, a Multi-Link Control field, a Common Info field, and a Link Info field. The Element ID field and the Element ID Extension field may include information to identify the Multi-Link element800. The Length field may indicate a length of the TWT element800. The Multi-Link Control field may include a type field indicating a type of the Multi-Link element800. In some implementations, a value of the type field indicates that the Multi-Link element800is a Basic Multi-Link element. The Common Info field may include information that is common to all the links with some exceptions.

The Link Info field may include information specific to one or more links and be optionally present. The Link Info field may include one or more Per-STA Profile subelements.FIG.8shows an example Per-STA Profile subelement included in the Link Info field of a Basic Multi-Link element. The Per-STA Profile subelement may include a Subelement ID field, a Length field, a STA Control field, a STA Info field, and a STA Profile field. The Subelement ID field may include information to identify the Per-STA Profile subelement. The Length field may indicate a length of the Per-STA Profile subelement. The STA Control field may include control information for the Basic Multi-Link element. The STA Profile field may include various information. In some embodiments, an AP affiliated with an NSTR mobile AP MLD and operating on a primary link may advertise a broadcast TWT schedule for an AP affiliated with the same NSTR mobile MLD and operating on a non-primary link. This can be achieved by including a TWT element comprising a corresponding broadcast TWT parameter set field in a STA profile field of a Per-STA profile subelement within the Link Info field of the basic multi-link element. The broadcast TWT parameter set field corresponds to the other AP operating on the non-primary link and is carried in a beacon frame and/or a probe response frame transmitted on the primary link.

FIG.9shows an example process for advertising a broadcast TWT schedule for an NSTR mobile AP MLD using an aligned schedule in accordance with an embodiment. For explanatory and illustration purposes, the example process900may be performed by AP 1 and AP 2 depicted inFIG.4. Although one or more operations are described or shown in particular sequential order, in other embodiments the operations may be rearranged in a different order, which may include performance of multiple operations in at least partially overlapping time periods.

Referring toFIGS.4and9, the process900may begin in operation901. In operation901, an NSTR mobile MLD (e.g., AP MLD410inFIG.4) intends to advertise a broadcast TWT schedule for a non-primary link.

In operation903, an AP affiliated with the NSTR mobile AP MLD and operating on the primary link (e.g., AP 1 inFIG.4) advertises the broadcast TWT schedule on the primary link and indicates that the broadcast TWT schedule is an aligned schedule.

In some embodiments, a STA is affiliated with a non-AP MLD associated with an NSTR mobile MLD and is operating on a non-primary link. When the STA sends a TWT request to an AP affiliated with the NSTR mobile MLD and operating on the non-primary link or the STA requests a membership for an aligned schedule on the non-primary link, the STA may use the same broadcast TWT ID that is used to identify the aligned schedule advertised on a primary link.

FIG.10shows an example process for advertising a broadcast TWT schedule in accordance with an embodiment. For explanatory and illustration purposes, the example process1000may be performed by STA 1 and STA 2 depicted inFIG.4. Although one or more operations are described or shown in particular sequential order, in other embodiments the operations may be rearranged in a different order, which may include performance of multiple operations in at least partially overlapping time periods. The process inFIG.10illustrates an example of the usage of an aligned schedule for advertising a broadcast TWT schedule for a non-primary link of an NSTR Mobile AP MLD.

Referring toFIGS.4and10, the process1000may begin in operation1001. In operation1001, a non-AP MLD (e.g., non-AP MLD420inFIG.4) is associated with an NSTR mobile AP MLD (e.g., AP MLD410inFIG.4). The non-AP MLD intends to establish a broadcast TWT schedule on a non-primary link.

In operation1003, a STA affiliated with the non-AP MLD and operating on a primary link (e.g., STA 1 inFIG.4) receives an advertisement of a broadcast TWT schedule via the primary link. In some embodiments, the advertisement may include an indication that the broadcast TWT schedule is an aligned schedule. The broadcast TWT ID of the aligned schedule advertised on the primary link may be set as B1, for example.

In operation1005, a STA affiliated with the non-AP MLD and operating on the non-primary link (e.g., STA 2 inFIG.4) sends a TWT request to the AP affiliated with the NSTR mobile AP MLD and operating on the non-primary link (e.g., AP 2 inFIG.4) via the non-primary link. The TWT request requests to become a member of the aligned schedule. The broadcast TWT ID of the broadcast TWT schedule for which the request is sent may be the same as B1.

FIG.11shows an example of an aligned schedule in accordance with an embodiment. The operation depicted inFIG.11is for illustration purposes and does not limit the scope of this disclosure to any particular implementations.

Referring toFIG.11, an NSTR link pair including primary link and non-primary link is established between the AP MLD410and the non-AP MLD420. The AP MLD410is an NSTR mobile AP MLD. UnlikeFIG.4, the non-primary link is established between AP 1 and STA 1, while the primary link is established between AP 2 and STA 2. As shown, a broadcast TWT schedule A (“Schedule-A”) is established on the non-primary link between AP 1 and STA1, while a broadcast TWT schedule B (“Schedule-B) is established on the primary link between AP 2 and STA 1. Schedule-A and Schedule-B are aligned with each other. InFIG.11, Schedule-A and Schedule-B may have the same TWT parameters including the broadcast TWT ID, as explained with reference toFIG.10.

In some embodiments, an NSTR mobile AP MLD can advertise or establish a first broadcast TWT schedule for a non-primary link via a primary link if a primary link has a second broadcast TWT schedule such that the start time and the end time of the TWT SP corresponding to the first broadcast TWT schedule on the non-primary link overlaps in time with the TWT SP corresponding to the second TWT schedule on the primary link.

FIG.12shows an example of establishing a broadcast TWT in accordance with an embodiment. The operation depicted inFIG.12is for illustration purposes and does not limit the scope of this disclosure to any particular implementations.

The example ofFIG.12is similar to the example ofFIG.11, except for the TWT SP duration. Referring toFIG.12, Schedule-A and Schedule-B are aligned in the start time of the TWT SP, while the TWT SP duration of Schedule-B is longer than the TWT SP duration of Schedule-A. The start time and the end time of the TWT SP of Schedule-A overlaps in time with the TWT SP of Schedule-B. In the scenario, the AP MLD410can advertise or establish Schedule-A for the non-primary link via the primary link.

In some embodiments, an AP affiliated with an NSTR mobile AP MLD intends to advertise a broadcast TWT schedule for a non-primary link by including a corresponding a TWT element comprising a corresponding broadcast TWT parameter set field in a beacon frame or a probe response frame transmitted on a primary link. The AP may include a link info field in a basic multi-link element for an AP affiliated with the NSTR mobile AP MLD and operating on the non-primary link.

In some embodiments, an AP affiliated with an NSTR mobile AP MLD and operating on a primary link may advertise a broadcast TWT schedule for the other AP affiliated with the same NSTR mobile AP MLD and operating on a non-primary link by including a TWT element comprising a corresponding broadcast TWT parameter set field in the STA Profile field of the Per-STA Profile subelement of the basic multi-link element corresponding to the AP operating on the nonprimary link carried in the beacon frames and probe response frames that it transmits on the primary link. The value in the broadcast TWT persistence subfield corresponding to the broadcast TWT schedule shall be in reference to the most recent TBTT and Beacon Interval indicated by the AP operating on the primary link.

In some embodiments, if an AP affiliated with an AP MLD is not in a multiple BSSID set or the AP corresponds to a transmitted BSSID in a multiple BSSID set, then the AP, in a beacon frame and/or a probe Response frame that is not a multi-link probe response that it transmits, may selectively include or not include the link Info field of the basic multi-link element for the AP MLD. In some implementations, the AP may not include the link Info field of the basic multi-link element for the AP MLD unless the AP is affiliated with an NSTR mobile AP MLD and operating on the primary link, and advertises a broadcast TWT schedule for the other AP affiliated with the same NSTR mobile AP MLD and operating on the nonprimary link, in which case the link Info field only includes a broadcast TWT element for that AP operating on the nonprimary channel. In some implementations, the AP may include the link Info field of the basic multi-link element for the AP MLD if the AP is affiliated with the NSTR mobile AP MLD and operating on the primary link, and advertises a broadcast TWT schedule for the other AP affiliated with the same NSTR mobile AP MLD and operating on the primary. In this case, the link Info field only includes a broadcast TWT element for the AP operating on the non-primary link.

In some embodiments, a broadcast TWT schedule advertised for the AP affiliated with an NSTR mobile AP MLD and operating on the nonprimary link is aligned with the broadcast TWT schedule advertised for the other AP affiliated with the same NSTR mobile AP MLD and operating on the primary link.

FIG.13shows an example process for advertising a broadcast TWT schedule in accordance with an embodiment. For explanatory and illustration purposes, the example process1300may be performed by STA 1 and STA 2 depicted inFIG.4. Although one or more operations are described or shown in particular sequential order, in other embodiments the operations may be rearranged in a different order, which may include performance of multiple operations in at least partially overlapping time periods. The process inFIG.13illustrates a general operation of a non-AP MLD to establish a broadcast TWT schedule for a non-primary link of an NSTR Mobile AP MLD.

Referring toFIGS.4and13, the process1300may begin in operation1301. In operation1301, a non-AP MLD (e.g., non-AP MLD420inFIG.4) is associated with an NSTR mobile AP MLD (e.g., AP MLD410inFIG.4). The non-AP MLD intends to establish a broadcast TWT schedule on a non-primary link.

In operation1303, a STA affiliated with the non-AP MLD and operating on a primary link (e.g., STA 1 inFIG.4) receives an advertisement of a broadcast TWT schedule via the primary link. In some embodiments, a TWT element comprising a corresponding broadcast TWT parameter set field is included in a STA profile field of a Per-STA profile subelement within a link information (link info) field of a basic multi-link element. The basic multi-link element corresponds to the AP operating on the non-primary link and is carried in a beacon frame and/or a probe response frame transmitted on the primary link.

In operation1305, a STA affiliated with the non-AP MLD and operating on the non-primary link (e.g., STA 2 inFIG.4) sends a TWT request to the AP affiliated with the NSTR mobile AP MLD and operating on the non-primary link (e.g., AP 2 inFIG.4) via the non-primary link. The TWT request may request to become a member of the broadcast TWT schedule.

All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using a phrase means for or, in the case of a method claim, the element is recited using the phrase step for.