Target wake-up time teardown process for multilink devices

Abstract

A method and apparatus for facilitating a target wake-up time (TWT) teardown operation by a multi-link device (MLD) in a wireless local area network. A non-access point (AP) MLD includes at least one processor and a station (STA), where the STA is configured to form a link with an AP of the AP MLD, and at least one TWT schedule or agreement is established on at least one of the links. The at least one processor is operatively coupled to the STA and configured to identify at least one of the links and generate or interpret a first message indicating that a TWT teardown is to be performed for the identified at least one link. The first of the STAs is configured to transmit the first message to or receive from a first of the APs via the first of the links.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to power management in wireless communication systems including multi-link devices.Embodiments of the present disclosure relate to a method and apparatus for enhancing target wake-up time operation of multi-link devices in a wireless local area network communication system. [Background technology]

[0002] Wireless Local Area Network (WLAN) technology allows devices to access the Internet in the 2.4 GHz, 5 GHz, 6 GHz or 60 GHz frequency bands. WLAN is based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. The IEEE 802.11 family of standards aims to increase the speed, reliability and range of wireless networks.

[0003] Next generation extremely high throughput (EHT) WI-FI systems, such as IEEE 802.11be, support multiple bands of operation called links, through which access point (AP) devices and non-AP devices can communicate with each other. Thus, both AP and non-AP devices can be capable of communication on different bands / links, called multi-link operation (MLO). WI-FI devices that support MLO are called multi-link devices (MLDs). With MLO, a non-access point (non-AP) MLD can discover, authenticate, associate, and set up multiple links with an AP MLD. Channel access and frame exchange are possible on each link that is set up between an AP MLD and a non-AP MLD. The components of the MLD that are involved in transmitting and receiving on one link are called stations (STAs).

[0004] Target Wake Time (TWT) is one of the most important features for power management in WI-FI networks, which was developed by IEEE 802.11ah and later adopted and modified in IEEE 802.11ax. With TWT operation, it is enough for a STA to wake up only at the pre-scheduled time negotiated with another STA or AP in the network. In the IEEE 802.11ax standard, two types of TWT operation are possible: individual TWT operation and broadcast TWT operation. An individual TWT agreement can be established between two STAs or between a STA and an AP. Meanwhile, with broadcast TWT operation, an AP can set up a shared TWT session for a group of STAs.

[0005] Limited TWT (rTWT or r-TWT) operation is a new feature introduced in IEEE 802.11be that provides additional protection for STAs scheduled with limited TWT in order to timely serve latency-sensitive applications. Limited TWT is based on the broadcast TWT mechanism, but there are several key properties that make limited TWT operation an important feature for supporting low-latency applications in next-generation WLAN systems. Limited TWT provides a protected service period for other STAs in a basic service set (BSS) that are not members of the rTWT schedule by transmitting a quiet element to them, where the quiet interval corresponds to the overlap of the quiet element with the initial part of the limited TWT service period (SP). Thus, it gives more channel access opportunities to STAs scheduled with rTWT members, which helps latency-sensitive traffic flows. Summary of the Invention [Means for solving the problem]

[0006] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure provide a method and apparatus for facilitating TWT teardown operations by an MLD in a WLAN.

[0007] In one embodiment, a non-AP MLD is provided, including a STA and at least one processor operably coupled to the STA. The STA is configured to form a link with an AP of the AP MLD. At least one TWT schedule or agreement is established on at least one of the links. The at least one processor is configured to generate or interpret a first message that identifies at least one of the links and indicates that a TWT teardown is performed for the identified at least one link. A first one of the STAs is configured to transmit or receive the first message to or from a first one of the APs via the first one of the links.

[0008] In another embodiment, an AP MLD is provided, including an AP and at least one processor operably coupled to the AP. The AP is configured to form links with STAs of a non-AP MLD. At least one TWT schedule or agreement is established on at least one of the links. The at least one processor is configured to generate or interpret a first message that identifies at least one of the links and indicates that a TWT teardown is performed for the identified at least one link. A first AP of the APs is configured to transmit or receive the first message to or from a first STA of the STAs via a first link of the links.

[0009] In another embodiment, a method of wireless communication performed by a non-AP MLD including a STA is provided. The STA is configured to form a link with an AP of the AP MLD and at least one TWT schedule or agreement is established on at least one of the links. The method includes generating or interpreting a first message that identifies at least one of the links and indicates that a TWT teardown is performed for the identified at least one link, and transmitting or receiving the first message to a first AP of the APs via the first link of the links.

[0010] Other technical features will be readily apparent to those skilled in the art from the following drawings, descriptions and claims.

[0011] Before turning to the detailed description below, it may be advantageous to provide definitions of some terms used throughout this patent document. The term "couple" and its derivatives refer to any direct or indirect connection between two or more elements, whether or not those elements are in physical contact with one another. The terms "transmit," "receive," and "communicate," and their derivatives, encompass both direct and indirect communication. The terms "include" and "comprise," and their derivatives, mean an open-ended inclusion. The term "or" is inclusive and means and / or. The phrase "associated with," and its derivatives, mean including, included within, interconnected with, containing, contained in, connected to or with, coupled to or with, communicable with, cooperate with, interleaved, juxtaposed, adjacent to, bound to or with, having, having a right of, having a relationship to or with, and the like. The term "controller" refers to any device, system, or part thereof that controls at least one operation. Such a controller may be implemented in hardware or a combination of hardware, software and / or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase "at least one," when used in conjunction with a list of items, means that different combinations of one or more of the listed items may be used, or only one item in the list may be required. For example, "at least one of A, B, and C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.As used herein, terms such as "first" and "second" or "first" and "second" may be used merely to distinguish a corresponding component from another component and do not limit the components in other aspects (e.g., importance or order). When an element (e.g., a first element) is referred to as being "coupled with," "coupled to," "connected with," or "connected to" another element (e.g., a second element) with or without the terms "operably" or "communicatively," it should be understood to mean that the element can be coupled to the other element directly (e.g., wired), wirelessly, or through a third element.

[0012] As used herein, the term "module" may include a hardware, software, or firmware implemented unit and may be used interchangeably with other terms, such as "logic," "logic block," "portion," or "circuit." A module may be a single integrated component or a minimum unit or portion thereof adapted to perform one or more functions. For example, according to one embodiment, a module may be implemented in the form of an application specific integrated circuit (ASIC).

[0013] Moreover, various functions described below may be implemented or supported by one or more computer programs, each of which is formed from computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, procedures, functions, objects, classes, instances, associated data, or portions thereof adapted for implementation in suitable computer-readable program code. The phrase "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer-readable medium" includes any type of medium accessible by a computer, such as read-only memory (ROM), random access memory (RAM), hard disk drive, compact disc (CD), digital video disc (DVD), or any other type of memory. A "non-transitory" computer-readable medium excludes wired, wireless, optical, or other communication links that transport transient electrical or other signals. Non-transitory computer-readable media include media on which data may be permanently stored, such as a rewritable optical disk or an erasable memory device, and media on which data may be stored and later overwritten.

[0014] Definitions for several other terms are provided throughout this patent document. In most cases, those of skill in the art should understand that such definitions apply to previous as well as future uses of the term so defined.

[0015] For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts and in which: [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 illustrates an exemplary wireless network in accordance with various embodiments of the present disclosure. [Figure 2A] FIG. 2 illustrates an exemplary AP according to various embodiments of the present disclosure. [Figure 2B] FIG. 2 illustrates an exemplary STA according to various embodiments of the present disclosure. [Diagram 3] FIG. 2 illustrates an example of various timing components for a TWT SP, according to an embodiment of the present disclosure. [Figure 4] FIG. 2 illustrates an example format of a TWT flow field, according to an embodiment of the present disclosure. [Diagram 5] FIG. 2 illustrates an example format of a TWT flow field, according to an embodiment of the present disclosure. [Figure 6] FIG. 2 illustrates an example format of a TWT flow field, according to an embodiment of the present disclosure. [Figure 7] A diagram illustrating an example format of a TWT flow field including a link ID bitmap, according to an embodiment of the present disclosure. [Figure 8] A diagram illustrating an example format of a TWT flow field including a link ID bitmap, according to an embodiment of the present disclosure. [Figure 9] A diagram illustrating an example format of a TWT flow field including a link ID bitmap, according to an embodiment of the present disclosure. [Figure 10] FIG. 1 illustrates an example of the use of TWT teardown frames in the context of multi-link operation, in accordance with an embodiment of the present disclosure. [Figure 11] A diagram illustrating an example format of a TWT flow field including a link ID subfield, according to an embodiment of the present disclosure. [Figure 12] A diagram illustrating an example format of a TWT flow field including a link ID subfield, according to an embodiment of the present disclosure. [Figure 13] A diagram illustrating an example format of a TWT flow field including a link ID subfield, according to an embodiment of the present disclosure. [Figure 14]A diagram illustrating an example format of a TWT flow field including a TWT schedule exclusion subfield, in accordance with an embodiment of the present disclosure. [Figure 15] FIG. 1 illustrates an example process for the use of TWT teardown frames in the context of a multi-link device. [Figure 16A] FIG. 1 illustrates an example process for facilitating a TWT teardown operation by an MLD, in accordance with various embodiments of the present disclosure. [Figure 16B] FIG. 1 illustrates an example process for facilitating a TWT teardown operation by an MLD, in accordance with various embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] 1-16B described below and the various embodiments used to illustrate the principles of the present disclosure in this patent document are for illustrative purposes only and should not be construed as limiting the scope of the present disclosure in any way. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged system or device.

[0018] The TWT teardown frame is used to tear down a TWT agreement or TWT schedule established between an AP and a non-AP STA. The embodiments of the present disclosure recognize that the use of TWT teardown frames in multi-link operation is not defined in the current 802.11 standard.

[0019] As a result, embodiments of the present disclosure provide a mechanism to facilitate use by an MLD of a TWT teardown frame to teardown a TWT schedule or agreement in multi-link operation.

[0020] Embodiments of the present disclosure further recognize that there is currently no way to remove any particular TWT agreement or schedule from a group of schedules or agreements being torn down, which is not very conducive for restricted TWT operation because an r-TWT scheduled STA may have multiple broadcast TWT schedules and restricted TWT schedules, and the scheduled STA may want to tear down the broadcast TWT schedule, for example, to save power while maintaining the r-TWT schedule for low latency traffic.

[0021] As a result, embodiments of the present disclosure provide a mechanism for facilitating selective exclusion of TWT schedules from the TWT teardown process using TWT teardown frames.

[0022] The embodiments of the present disclosure also recognize that currently, a TWT teardown frame is a unicast frame that cannot be transmitted to multiple STAs simultaneously. For example, an AP that schedules r-TWTs in conjunction with AP MLD may want to disable a link for a certain period of time, but currently there is no way to use a TWT teardown frame to tear down all TWT schedules operating on the link before the link is disabled or removed.

[0023] As a result, embodiments of the present disclosure provide a mechanism for facilitating the use of broadcast TWT teardown frames by MLDs.

[0024] Embodiments of the present disclosure further recognize that currently, TWT teardown frames cannot operate at the MLD level, for example, an MLD may want to teardown a TWT schedule or agreement on multiple links to save power, but there is currently no way to indicate one or more links among multiple links between an AP MLD and a non-AP MLD for which a TWT teardown frame is intended.

[0025] 1 illustrates an exemplary wireless network 100 in accordance with various embodiments of the present disclosure. The embodiment of wireless network 100 illustrated in FIG. 1 is for illustration purposes only. Other embodiments of wireless network 100 may be used without departing from the scope of the present disclosure.

[0026] Wireless network 100 includes APs 101 and 103. APs 101 and 103 communicate with at least one network 130, such as the Internet, a proprietary Internet Protocol (IP) network, or other data network. AP 101 provides wireless access to network 130 for multiple STAs 111-114 within its coverage area 120. APs 101-103 may communicate with each other and with STAs 111-114 using Wi-Fi or other WLAN communication techniques.

[0027] Depending on the network type, other well-known terms such as "router" or "gateway" may be used in place of "access point" or "AP". For convenience, the term "AP" is used in this disclosure to refer to a network infrastructure component that provides wireless access to remote terminals. In a WLAN, assuming that the AP also competes for a wireless channel, the AP may be referred to as a STA (e.g., an AP STA). Also depending on the network type, other well-known terms such as "mobile station", "subscriber station", "remote terminal", "user equipment", "wireless terminal", or "user device" may be used in place of "station" or "STA". For convenience, the terms "station" and "STA" are used in this disclosure to refer to a remote wireless equipment that wirelessly accesses an AP or competes for a wireless channel in a WLAN, regardless of whether the STA is a mobile device (such as a mobile phone or smartphone) or is typically considered a fixed device (such as a desktop computer, AP, media player, fixed sensor, television, etc.). This type of STA may also be referred to as a non-AP STA.

[0028] In various embodiments of the present disclosure, each of the APs 101 and 103 and each of the STAs 111-114 may be an MLD. In such embodiments, the APs 101 and 103 may be AP MLDs and the STAs 111-114 may be non-AP MLDs. Each MLD is associated with two or more STAs. For ease of explanation, an AP MLD is described herein as being associated with two or more APs (e.g., two or more AP STAs) and a non-AP MLD is described herein as being associated with two or more STAs (e.g., two or more non-AP STAs).

[0029] The dotted lines indicate the approximate extents of coverage areas 120 and 125, which are shown as generally circular for purposes of illustration and explanation only. It should be clearly understood that coverage areas associated with an AP, such as coverage areas 120 and 125, may have other shapes, including irregular shapes, depending on the configuration of the AP and variations in the radio environment associated with natural and man-made obstacles.

[0030] As described in more detail below, one or more of the APs may include circuitry and / or programming to facilitate TWT teardown operations by MLD in a WLAN. Although FIG. 1 illustrates an example of wireless network 100, various modifications may be made to FIG. 1. For example, wireless network 100 may include any number of APs and any number of STAs in any suitable arrangement. Similarly, AP 101 may directly communicate with any number of STAs and provide those STAs with wireless broadband access to network 130. Similarly, each AP 101-103 may directly communicate with network 130 and provide the STAs with direct wireless broadband access to network 130. Additionally, AP 101 and / or 103 may provide access to other or additional external networks, such as an external telephone network or other type of data network.

[0031] FIG. 2A illustrates an exemplary AP 101 according to various embodiments of the present disclosure. The embodiment of the AP 101 illustrated in FIG. 2A is for illustration purposes only, and the AP 103 of FIG. 1 may have the same or similar configuration. In the embodiment described herein below, the AP 101 is an AP MLD. However, while APs appear in a variety of configurations, FIG. 2A does not limit the scope of the present disclosure to any particular implementation of an AP.

[0032] The AP MLD 101 is in association with multiple APs 202a-202n (which may be referred to as AP1-APn, for example). Each of the associated APs 202a-202n includes multiple antennas 204a-204n, multiple RF transceivers 209a-209n, a transmit (TX) processing circuit 214, and a receive (RX) processing circuit 219. The AP MLD 101 also includes a controller / processor 224, a memory 229, and a backhaul or network interface 234.

[0033] The illustrated components of each cooperating AP 202a-202n may represent the physical (PHY) layer and lower media access control (LMAC) layer in the open systems interconnection (OSI) network model. In such an embodiment, the illustrated components of the AP MLD 101 represent a single upper MAC (UMAC) layer and other higher layers in the OSI model that are shared by all of the cooperating APs 202a-202n.

[0034] For each associated AP 202a-202n, RF transceivers 209a-209n receive incoming RF signals, such as signals transmitted by STAs in the network 100, from antennas 204a-204n. In some embodiments, each associated AP 202a-202n operates in a different bandwidth, e.g., 2.4 GHz, 5 GHz, or 6 GHz, such that the incoming RF signals received by each associated AP may be at different frequencies of RF. The RF transceivers 209a-209n downconvert the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are sent to RX processing circuitry 219, which generates processed baseband signals by filtering, decoding, and / or digitizing the baseband or IF signals. The RX processing circuitry 219 sends the processed baseband signals to the controller / processor 224 for further processing.

[0035] For each associated AP 202a-202n, the TX processing circuitry 214 receives analog or digital data (such as voice data, web data, email, or interactive video game data) from the controller / processor 224. The TX processing circuitry 214 encodes, multiplexes, and / or digitizes the outgoing baseband data to generate processed baseband or IF signals. The RF transceivers 209a-209n receive the outgoing processed baseband or IF signals from the TX processing circuitry 214 and upconvert the baseband or IF signals to RF signals transmitted via the antennas 204a-204n. In embodiments in which each associated AP 202a-202n operates in a different bandwidth, e.g., 2.4 GHz, 5 GHz, or 6 GHz, the outgoing RF signals transmitted by each associated AP may be at different frequencies of RF.

[0036] The controller / processor 224 may include one or more processors or other processing devices that control the overall operation of the AP MLD 101. For example, the controller / processor 224 may control the reception of forward channel signals and the transmission of reverse channel signals by the RF transceivers 209a-209n, the RX processing circuitry 219, and the TX processing circuitry 214 in accordance with well-known principles. The controller / processor 224 may also support additional functionality, such as more advanced wireless communication functions. For example, the controller / processor 224 may support beamforming or directional routing operations in which outgoing signals from multiple antennas 204a-204n are weighted differently to effectively steer the outgoing signals in a desired direction. The controller / processor 224 may also support OFDMA operations in which outgoing signals are assigned to different subsets of subcarriers for different recipients (e.g., different STAs 111-114). Any of a variety of other functions may be supported within the AP MLD 101 by the controller / processor 224, including facilitating TWT teardown operations by the MLD in the WLAN. In some embodiments, the controller / processor 224 includes at least one microprocessor or microcontroller. The controller / processor 224 may also execute programs and other processes that reside within the memory 229, such as an OS. The controller / processor 224 may move data in and out of the memory 229 as required by the processes it executes.

[0037] The controller / processor 224 is also coupled to a backhaul or network interface 234. The backhaul or network interface 234 allows the AP MLD 101 to communicate with other devices or systems over a backhaul connection or over a network. The interface 234 can support communication over any suitable wired or wireless connection. For example, the interface 234 may allow the AP MLD 101 to communicate over a wired or wireless local area network or to a larger network (such as the Internet) over a wired or wireless connection. The interface 234 includes any suitable structure that supports communication over a wired or wireless connection, such as an Ethernet or RF transceiver. The memory 229 is coupled to the controller / processor 224. A portion of the memory 229 can include RAM, and another portion of the memory 229 can include flash memory or other ROM.

[0038] As described in more detail below, the AP MLD 101 may include circuitry and / or programming for facilitating TWT teardown operations by MLDs in a WLAN. Although FIG. 2A illustrates one example of an AP MLD 101, various modifications may be made to FIG. 2A. For example, the AP MLD 101 may include any number of each of the components illustrated in FIG. 2A. As a particular example, the AP MLD 101 may include multiple interfaces 234, and the controller / processor 224 may support a routing function to route data between different network addresses. As another particular example, although each associated AP 202a-202n is illustrated as including a single instance of the TX processing circuit 214 and a single instance of the RX processing circuit 219, the AP MLD 101 may include multiple instances of each of one or more of the associated APs 202a-202n (e.g., one per RF transceiver). Alternatively, only one antenna and RF transceiver path may be included in one or more of the cooperating APs 202a-202n, such as in a legacy AP. Similarly, various components of FIG. 2A may be combined, further subdivided or omitted, and additional components may be added according to particular needs.

[0039] FIG. 2B illustrates an exemplary STA 111 according to various embodiments of the present disclosure. The embodiment of the STA 111 illustrated in FIG. 2B is for illustration purposes only, and the STAs 111-114 in FIG. 1 may have the same or similar configurations. In the embodiment described herein below, the STA 111 is a non-AP MLD. However, while STAs appear in a variety of configurations, FIG. 2B does not limit the scope of the present disclosure to any particular implementation of the STA.

[0040] The non-AP MLD 111 is associated with a plurality of STAs 203a-203n (which may be referred to as, for example, STA1-STAn). Each of the associated STAs 203a-203n includes an antenna 205, a radio frequency (RF) transceiver 210, a TX processing circuit 215, and a receive (RX) processing circuit 225. The non-AP MLD 111 also includes a microphone 220, a speaker 230, a controller / processor 240, an input / output (I / O) interface (IF) 245, a touch screen 250, a display 255, and a memory 260. The memory 260 includes an operating system (OS) 261 and one or more applications 262.

[0041] The illustrated components of each cooperating STA 203a-203n may represent the PHY and LMAC layers in the OSI network model. In such an embodiment, the illustrated components of the non-AP MLD 111 represent a single UMAC layer and other higher layers in the OSI model that are shared by all of the cooperating STAs 203a-203n.

[0042] For each associated STA 203a-203n, the RF transceiver 210 receives from the antenna 205 an incoming RF signal transmitted by an AP of the network 100. In some embodiments, each associated STA 203a-203n operates in a different bandwidth, e.g., 2.4 GHz, 5 GHz, or 6 GHz, such that the incoming RF signal received by each associated STA may be at a different frequency of RF. The RF transceiver 210 downconverts the incoming RF signal to generate an intermediate frequency (IF) or baseband signal. The IF or baseband signal is sent to the RX processing circuit 225, which generates a processed baseband signal by filtering, decoding, and / or digitizing the baseband or IF signal. The RX processing circuit 225 sends the processed baseband signal to the speaker 230 (e.g., for voice data) or to the controller / processor 240 for further processing (e.g., for web browsing data).

[0043] For each associated STA 203a-203n, the TX processing circuitry 215 receives analog or digital voice data from the microphone 220 or other outgoing baseband data (such as web data, email, or interactive video game data) from the controller / processor 240. The TX processing circuitry 215 encodes, multiplexes, and / or digitizes the outgoing baseband data to generate a processed baseband or IF signal. The RF transceiver 210 receives the outgoing processed baseband or IF signal from the TX processing circuitry 215 and upconverts the baseband or IF signal to an RF signal that is transmitted via the antenna 205. In an embodiment in which each associated STA 203a-203n operates in a different bandwidth, e.g., 2.4 GHz, 5 GHz, or 6 GHz, the outgoing RF signal transmitted by each associated STA may be at a different frequency of RF.

[0044] The controller / processor 240 may include one or more processors and execute a base OS program 261 stored in memory 260 to control the overall operation of the non-AP MLD 111. In one such operation, the main controller / processor 240 controls the reception of forward channel signals and the transmission of reverse channel signals by the RF transceiver 210, the RX processing circuitry 225, and the TX processing circuitry 215 in accordance with well-known principles. The main controller / processor 240 may also include processing circuitry configured to facilitate TWT teardown operations by the MLD in the WLAN. In some embodiments, the controller / processor 240 includes at least one microprocessor or microcontroller.

[0045] The controller / processor 240 may also execute other processes and programs resident in the memory 260, such as operations for facilitating TWT teardown operations by MLDs in a WLAN. The controller / processor 240 may move data into and out of the memory 260 as required by the processes it executes. In some embodiments, the controller / processor 240 is configured to execute multiple applications 262, such as an application for facilitating TWT teardown operations by MLDs in a WLAN. The controller / processor 240 may operate the multiple applications 262 based on an OS program 261 or in response to signals received from an AP. The main controller / processor 240 is also coupled to an I / O interface 245 that gives the non-AP MLD 111 the ability to connect to other devices, such as laptop computers and handheld computers. The I / O interface 245 is the communication path between these accessories and the main controller 240.

[0046] The controller / processor 240 is also coupled to a touch screen 250 and a display 255. An operator of the non-AP MLD 111 can use the touch screen 250 to input data into the non-AP MLD 111. The display 255 can be a liquid crystal display, a light emitting diode display, or other display capable of depicting text and / or at least limited graphics, for example from a website. The memory 260 is coupled to the controller / processor 240. A portion of the memory 260 can include random access memory (RAM) and another portion of the memory 260 can include flash memory or other read only memory (ROM).

[0047] Although FIG. 2B illustrates an example of a non-AP MLD 111, various modifications may be made to FIG. 2B. For example, various components of FIG. 2B may be combined, further subdivided or omitted, and additional components may be added according to specific needs. In a particular example, one or more of the cooperating STAs 203a-203n may include any number of antennas 205 for MIMO communication with the AP 101. In another example, the non-AP MLD 111 does not include voice communication, or the controller / processor 240 may be divided into multiple processors, such as one or more central processing units (CPUs) and one or more graphic processing units (GPUs). Also, although FIG. 2B illustrates the non-AP MLD 111 configured as a mobile phone or smartphone, the non-AP MLD may be configured to operate as other types of mobile or fixed devices.

[0048] 3 illustrates an example of various timing components for a TWT SP according to an embodiment of the present disclosure. In this example, STA1 may be a non-AP STA, such as STA111. STA1 is the STA that has been scheduled with a TWT, and AP1 (not shown) is the AP that schedules its associated TWT.

[0049] STA1 establishes a broadcast TWT schedule with AP1. t1 is the value of the target awake time indicated in the Target Wake Time field in the Broadcast TWT Parameter Set field of the TWT element. Thus, t1 is the time when STA1 should ideally be able to start frame changes with AP1. Starting from t1, the duration for which the STA needs to stay awake is the value of the nominal awake time (T) indicated in the Nominal Minimum TWT Wake Duration field in the Broadcast TWT Parameter Set field. For various reasons, STA1 cannot start frame exchange with AP1 at the nominal SP start time t1. The actual SP start time may be much later. In the figure, the actual SP start time is shown as time t2. The minimum awake duration for STA1 is also adjusted due to the delayed actual SP start time, shown as AdjustedMinimumTWTWakeDuration=T-(t2-t1).

[0050] As mentioned above, the TWT teardown frame is used to teardown a TWT agreement or TWT schedule established between an AP and a non-AP STA. The format of the TWT teardown frame is shown in Table 1.

[0051] [Table 1]

[0052] 5 illustrates an example format of a TWT flow field 502 according to an embodiment of the present disclosure. The TWT flow field 502 is an example format for the TWT flow field in a TWT teardown frame of Table 1 when the negotiation type subfield is set to 2.

[0053] 6 illustrates an example format of a TWT flow field 602 according to an embodiment of the present disclosure. The TWT flow field 602 is an example format for the TWT flow field in a TWT teardown frame of Table 1 when the negotiation type subfield is set to 3.

[0054] According to one embodiment, during multi-link operation, a STA associated with the MLD may transmit a TWT teardown frame on a first link to teardown a TWT agreement or schedule established on a second link. The intended link on which the TWT schedule or agreement is to be torn down may be indicated by including a TWT link identifier (ID) subfield or a TWT link ID bitmap subfield in the TWT teardown frame.

[0055] 7 illustrates an example format of a TWT flow field 702 including a link ID bitmap according to an embodiment of the disclosure. The TWT flow field 702 is an example format for the TWT flow field in a TWT teardown frame of Table 1 when the negotiation type subfield is set to 0 or 1. According to this embodiment, a link ID bitmap subfield 704 may be included in the TWT flow field 702 of the TWT teardown frame. According to some embodiments, a link ID bitmap present subfield 706 may be present in the TWT flow field to indicate the presence of the link ID bitmap subfield 704 in the TWT flow field 702.

[0056] When the Link ID Bitmap Present subfield in the TWT Flow field is set to 1, it indicates that the Link ID Bitmap subfield is present in the TWT Flow field of the TWT teardown frame. Otherwise, the Link ID Bitmap subfield is not present in the TWT Flow field of the TWT teardown frame. According to one embodiment, when present in the TWT Flow field of the TWT teardown frame, the size of the Link ID Bitmap subfield is 16 bits long. According to another embodiment, when present in the TWT Flow field, the size of the Link ID Bitmap subfield is 8 bits long.

[0057] According to some embodiments, the Link ID Bitmap subfield in the TWT Flow field of the TWT Teardown frame indicates one or more links to which the TWT Teardown frame sent by the STA associated with the MLD applies. A value of 1 in bit position i of the Link ID Bitmap subfield of the TWT Flow field indicates that the link associated with Link ID i is a link to which the TWT Teardown frame sent by the STA associated with the MLD applies. A value of 0 in bit position i of the Link ID Bitmap subfield of the TWT Flow field indicates that the link associated with Link ID i is not a link to which the TWT Teardown frame sent by the STA associated with the MLD applies.

[0058] According to one embodiment, the Link ID Bitmap subfield of the TWT flow field may indicate at most one link. According to this embodiment, at most one bit position in the Link ID Bitmap subfield may be set to 1. According to another embodiment, the Link ID Bitmap subfield of the TWT flow field may indicate two or more links. According to this embodiment, two or more bit positions in the Link ID Bitmap subfield may be set to 1.

[0059] 8 illustrates an example format of a TWT flow field 802 that includes a link ID bitmap, according to an embodiment of the present disclosure. The TWT flow field 802 is an example format change to the TWT flow field 702 when the negotiation type subfield is set to 2.

[0060] 9 illustrates an example format of a TWT flow field 902 that includes a link ID bitmap in accordance with an embodiment of the present disclosure. The TWT flow field 902 is an example format change to the TWT flow field 702 when the negotiation type subfield is set to 3.

[0061] According to one embodiment, when a STA associated with an MLD transmits a TWT teardown frame that does not include a Link ID Bitmap subfield in the TWT flow field, it may indicate that the TWT teardown frame applies to the link on which the TWT teardown frame is transmitted.

[0062] According to one embodiment, a value of all zeros in the Link ID Bitmap subfield in the TWT Flow field is reserved. According to another embodiment, a value of all zeros in the Link ID Bitmap subfield in the TWT Flow field of a TWT Teardown frame indicates that the TWT Teardown frame applies to the link on which the TWT Teardown frame is transmitted.

[0063] 10 illustrates an example of the use of TWT teardown frames in the context of multi-link operation, according to an embodiment of the present disclosure. In the example of FIG. 10, the AP MLD can be AP MLD 101 and the non-AP MLD can be non-AP MLD 111. It will be understood that further references to AP MLD or non-AP MLD herein refer to AP MLD 101 or non-AP MLD 111, respectively. Although AP MLD 101 is shown with three associated APs, AP1, AP2, and AP3, and non-AP MLD 111 is shown with three associated STAs, STA1, STA2, and STA3, it will be understood that this is merely an example and that any suitable MLD with any number of associated APs or STAs may be used.

[0064] In this example, three links are established between the AP MLD and its associated non-AP MLD: link 1 between AP1 and STA1, link 2 between AP2 and STA2, and link 3 between AP3 and STA3. Three TWT schedules or agreements are set up: TWT Schedule 1 is established on link 1, TWT Schedule 2 is established on link 2, and TWT Schedule 3 is established on link 3. STA2, which is associated with the non-AP MLD, sends a TWT teardown frame 1002 to AP2, which is associated with the AP MLD, via link 2. In the TWT teardown frame 1002, STA2 indicates link 1 and link 3. Thus, TWT Schedule 1 and TWT Schedule 3 on link 1 and link 3 are torn down, respectively, while Schedule 2 on link 2 is maintained.

[0065] According to one embodiment, if multiple links are indicated in the Link ID Bitmap subfield of the TWT Flow field of the TWT Teardown frame, the Broadcast TWT ID subfield or the TWT Flow Identifier subfield of the TWT Flow field is reserved. According to another embodiment, if multiple links are indicated in the Link ID Bitmap subfield, the TWT Teardown frame applies to the TWT schedule or agreement on the links indicated in the Link ID Bitmap subfield, as indicated by the Broadcast TWT ID subfield or the TWT Flow Identifier subfield.

[0066] 11 illustrates an example format of a TWT flow field 1102 including a link ID subfield according to an embodiment of the present disclosure. The TWT flow field 1102 is an example format for the TWT flow field in a TWT teardown frame of Table 1 when the negotiation type subfield is set to 0 or 1. According to this embodiment, a link ID subfield 1104 may be included in the TWT flow field 1102 of a TWT teardown frame to indicate the link to which the TWT teardown frame applies.

[0067] 12 illustrates an example format of a TWT flow field 1202 including a Link ID subfield, according to an embodiment of the disclosure. The TWT flow field 1202 is an example format change to the TWT flow field 1102 when the Negotiation Type subfield is set to 2.

[0068] 13 illustrates an example format of a TWT flow field 1302 including a Link ID subfield, according to an embodiment of the disclosure. The TWT flow field 1302 is an example format change to the TWT flow field 1102 when the Negotiation Type subfield is set to 3.

[0069] As noted above, there is currently no way to exclude any particular TWT agreement or schedule from a group of schedules or agreements being torn down using a TWT teardown frame. For example, when the Teardown All TWT subfield is set to 1 in the TWT Flows field of a TWT teardown frame, it indicates that all individual TWT agreements or broadcast TWT schedules are torn down by the TWT teardown frame.

[0070] 14 illustrates an example format of a TWT flow field 1402 including a TWT schedule excluded subfield according to an embodiment of the present disclosure. The TWT flow field 1402 is an example format for the TWT flow field in a TWT teardown frame of Table 1 when the negotiation type subfield is set to 3. According to this embodiment, an R-TWT Excluded subfield 1404 may be included in the TWT flow field 1402 of a TWT teardown frame to facilitate an indication that a restricted TWT schedule will not be torn down by the TWT teardown frame.

[0071] The size of the R-TWT Exclusion subfield 1404 may be 1 bit. If the Teardown All TWT subfield 1406 in the TWT Flows field is set to 1 and the R-TWT Exclusion subfield 1404 is set to 0, it may indicate that all TWT schedules or TWT agreements on the identified link are intended to be torn down, including the restricted TWT schedule. If the Teardown All TWT subfield 1406 in the TWT Flows field is set to 1 and the R-TWT Exclusion subfield 1404 is set to 1, it indicates that all TWT schedules or TWT agreements on the identified link are intended to be torn down, except for the R-TWT schedule.

[0072] 15 illustrates an example process 1502 for using a TWT teardown frame in the context of a multi-link device. In this example, a non-AP MLD has established at least two links between its associated STAs and a corresponding AP associated with the associated AP MLD. The non-AP MLD transmits a TWT teardown frame on one of the links (the second link) to tear down a TWT schedule or agreement on a different link (the first link).

[0073] 16A and 16B illustrate an example process for facilitating a TWT teardown operation by an MLD, according to various embodiments of the present disclosure. Although the processes 1600 and 1601 of FIG. 16A and FIG. 16B are described as being performed by a non-AP MLD, respectively, it is understood that a corresponding AP MLD performs the corresponding process. In addition, for convenience, the processes of FIG. 16A and FIG. 16B are described as being performed by a WI-FI non-AP MLD including a plurality of STAs, each including a transceiver configured to form a link with a corresponding AP associated with the WI-FI AP MLD. However, it is understood that any suitable wireless communication device may perform these processes.

[0074] 16A, process 1600 begins with the non-AP MLD generating a first message identifying at least one of the links and indicating that a TWT teardown is to be performed for the identified at least one link (step 1605). In some embodiments, the first message is a TWT teardown frame that includes a TWT flow field that identifies the at least one link.

[0075] The non-AP MLD then sends a first message to the AP MLD via a first one of the links (step 1610).

[0076] In some embodiments, the identified at least one link includes at least one link other than the first link, i.e., the first message is transmitted over one link to tear down a TWT schedule or agreement on the other link. In some embodiments, the identified at least one link may also include the first link (i.e., the link over which the first message is transmitted).

[0077] In some embodiments, to identify at least one link for which TWT teardown is to be performed, the non-AP MLD may include in the first message a bitmap having entries corresponding to link identifiers for each of the links, and set the entries of the bitmap while generating the first message to identify the at least one link for which TWT teardown is to be performed.

[0078] In other embodiments, to identify one link on which TWT teardown is performed, the non-AP MLD may include a link identifier subfield in the first message and set the link identifier subfield while generating the first message to identify one link on which TWT teardown is performed.

[0079] In some embodiments, the first message includes an indication that at least one type of TWT schedule or agreement is excluded from TWT teardown on the identified at least one link. For example, this may be an indication that a restricted TWT schedule is excluded from TWT teardown.

[0080] Referring now to FIG. 16B, process 1601 begins with the non-AP MLD receiving a first message from the AP MLD via a first one of the links (step 1615).

[0081] The non-AP MLD then interprets the first message, which identifies at least one of the links and indicates that a TWT teardown is to be performed for the identified at least one link (step 1620). As seen in FIG. 16A, the first message may be a TWT teardown frame that includes a TWT flow field that identifies the at least one link.

[0082] As seen in Figure 16A, in some embodiments, the identified at least one link includes at least one link other than the first link. That is, the first message is transmitted over one link to tear down a TWT schedule or agreement on the other link. In some embodiments, the identified at least one link may also include the first link (i.e., the link over which the first message is transmitted).

[0083] Similar to FIG. 16A, in some embodiments, the first message includes a bitmap having entries corresponding to link identifiers for each of the links, and the non-AP MLD may interpret the entries of the bitmap after receiving the first message to identify at least one link for which TWT teardown is to be performed.

[0084] Similar to FIG. 16A, in some embodiments, the first message may include a link identifier subfield, and the non-AP MLD may interpret the link identifier subfield after receiving the first message to identify one link on which TWT teardown is performed.

[0085] 16A, in some embodiments, the first message includes an indication that at least one type of TWT schedule or agreement is excluded from TWT teardown on at least one identified link. For example, this may be an indication that a restricted TWT schedule is excluded from TWT teardown.

[0086] The above flow charts illustrate example methods or processes that may be implemented in accordance with the principles of the present disclosure, and various modifications may be made to the methods or processes illustrated in the flow charts. For example, although shown as a series of steps, various steps may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, steps may be omitted or substituted with other steps.

[0087] Although the present disclosure has been described with exemplary embodiments, various changes and modifications may be suggested to those skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims. The description in this application should not be read as implying that any particular element, step, or function is an essential element that must be included in the scope of the claims. The scope of the patented subject matter is defined by the claims. [Explanation of symbols]

[0088] 100 Wireless Network 101 Access Point (AP), AP MLD 103 AP 111 stations (STA), non-AP MLD 112 STA 113 STA 114 STA 120 Coverage Area 125 Coverage Area 130 Network 202a AP 202b AP 202n AP 203a STA 203b STA 203n STA 204a Antenna 204b Antenna 204n Antenna 205 Antenna 209a RF Transceiver 209b RF Transceiver 209n RF Transceiver 210 Antenna 214 Transmit (TX) processing circuit 215 TX processing circuit 219 Receiver (RX) processing circuit 220 Microphone 224 Controller / Processor 225 RX processing circuit 229 Memory 230 Speakers 234 Backhaul or Network Interface 240 Controllers / Processors 245 Input / Output (I / O) Interface (IF) 250 Touchscreen 255 Display 260 Memory 261 Operating System (OS) 262 Applications 402 Field 502 Target Wake Time (TWT) Flow Field 602 TWT Flow Field 702 TWT Flow Field 704 Link ID Bitmap subfield 706 Link ID Bitmap Present Subfield 802 TWT Flow Field 902 TWT Flow Field 1002 TWT Teardown Frame 1102 TWT Teardown Frame 1104 Link ID subfield 1202 TWT Flow Field 1302 TWT Flow Field 1402 WT Flow Field 1404 R-TWT Exclusion Subfield 1406 Teardown all TWT subfields

Claims

1. A station (STA) configured to form links with APs of an access point (AP) multi-link device (MLD), wherein at least one target wake time (TWT) schedule or agreement is established on at least one of the links; at least one processor operatively coupled to the STA, the at least one processor configured to generate or interpret a first message that identifies at least one of the links and indicates that a TWT teardown is to be performed for the identified at least one link; Including, A non-AP MLD, wherein a first one of the STAs is configured to transmit the first message to or receive the first message from a first one of the APs via a first one of the links.

2. The non-AP MLD of claim 1 , wherein the identified at least one link includes at least one link other than the first link.

3. the first message includes a bitmap having an entry corresponding to a link identifier for each of the links; The at least one processor: setting the entry of the bitmap while generating the first message to identify the at least one link for which the TWT teardown is to be performed; or interpreting the entry in the bitmap after receiving the first message to identify the at least one link for which the TWT teardown is to be performed. The non-AP MLD of claim 1 , further configured to:

4. the first message includes a link identifier subfield; The at least one processor: setting the link identifier subfield while generating the first message to identify one link over which the TWT teardown is to be performed; or interpreting the link identifier subfield after receiving the first message to identify the one link for which the TWT teardown is to be performed. The non-AP MLD of claim 1 , further configured to:

5. the first message includes an indication that at least one type of TWT schedule or agreement is excluded from the TWT teardown on the identified at least one link; 2. The non-AP MLD of claim 1, wherein the indication that at least one type of TWT schedule or agreement is excluded from the TWT teardown is an indication that a restricted TWT schedule is excluded from the TWT teardown.

6. The non-AP MLD of claim 1 , wherein the first message is a TWT teardown frame that includes a TWT flow field that identifies the at least one link.

7. An AP configured to form links with stations (STAs) of a non-Access Point (AP) Multi-Link Device (MLD), wherein at least one Target Wake Time (TWT) schedule or agreement is established on at least one of the links; at least one processor operably coupled to the AP, the at least one processor configured to generate or interpret a first message that identifies at least one of the links and indicates that a TWT teardown is to be performed for the identified at least one link; Including, A first AP of the APs is configured to transmit the first message to or receive the first message from a first STA of the STAs via a first link of the links, AP MLD.

8. The AP MLD of claim 7, wherein the identified at least one link includes at least one link other than the first link.

9. the first message includes a bitmap having an entry corresponding to a link identifier for each of the links; The at least one processor: setting the entry of the bitmap while generating the first message to identify the at least one link for which the TWT teardown is to be performed; or interpreting the entry in the bitmap after receiving the first message to identify the at least one link for which the TWT teardown is to be performed. The AP MLD of claim 7, further configured to:

10. the first message includes a link identifier subfield; The at least one processor: setting the link identifier subfield while generating the first message to identify one link over which the TWT teardown is to be performed; or interpreting the link identifier subfield after receiving the first message to identify the one link for which the TWT teardown is to be performed. The AP MLD of claim 7, further configured to:

11. the first message includes an indication that at least one type of TWT schedule or agreement is excluded from the TWT teardown on the identified at least one link; 8. The AP MLD of claim 7, wherein the indication that at least one type of TWT schedule or agreement is excluded from the TWT teardown is an indication that a restricted TWT schedule is excluded from the TWT teardown.

12. 8. The AP MLD of claim 7, wherein the first message is a TWT teardown frame including a TWT flow field that identifies the at least one link.

13. 7. A method of wireless communication, comprising operations performed by at least one processor of a non-access point (AP) multi-link device (MLD) according to any one of claims 1 to 6.

14. 13. A method of wireless communication, comprising operations performed by at least one processor of an access point (AP) multi-link device (MLD) according to any one of claims 7 to 12.

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