Block acknowledgment transfer handling for wireless networks

Abstract

When a station (STA) roams from a first access point (AP) to a second AP, the first AP in a wireless network transfers the block acknowledgement (BA) session and related parameters of the STA to the second AP, allowing the STA to roam between APs without having to terminate and re-setup the BA session.

Description

Technical Field

[0001] This disclosure generally relates to wireless communication systems, and more particularly to, for example, but not limited to, block acknowledgment (ACK) establishment transfer processing for wireless networks. Background Technology

[0002] Since the late 1990s, Wireless Local Area Network (WLAN) technology has evolved towards increasing data rates and continues to grow in various markets such as homes, businesses, and hotspots. WLAN 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 standard family aims to improve speed and reliability and extend the operational range of wireless networks.

[0003] WLAN devices increasingly need to support a variety of latency-sensitive or real-time applications, such as augmented reality (AR), robotics, artificial intelligence (AI), cloud computing, and autonomous vehicles. To achieve the extremely low latency and extremely high throughput required for such applications, Multi-Link Operation (MLO) has been proposed for WLANs. A WLAN is formed by WLAN devices within a limited area such as a home, school, apartment, or office building. Each WLAN device can have one or more Stations (STAs), such as Access Point (AP) STAs and Non-Access Point (Non-AP) STAs.

[0004] MLO enables non-AP multi-link devices (MLDs) to establish multiple links with AP MLDs. Each of these links can independently enable channel access and frame switching between the non-AP MLD and the AP MLD, which can reduce latency and increase throughput.

[0005] The descriptions set forth in the Background section should not be assumed to be prior art simply because they are set forth in the Background section. The Background section may describe aspects or embodiments of this disclosure. Summary of the Invention

[0006] One aspect of this disclosure provides a first access point (AP) in a wireless network, including: a memory; and a processor coupled to the memory. The processor is configured to: receive a first frame from a slave station (STA), the first frame triggering a transfer block acknowledgment (BA) session to a second AP. The processor is configured to: communicate with the second AP to transfer the BA session or at least one parameter associated with the BA session. The processor is configured to send a second frame to the STA in response to the first frame.

[0007] In some examples, the first frame includes at least one of the following: an indication of intent to roam from the first AP to the second AP, an indication of the BA session to be transferred, an indication of the sequence number or one or more parameters associated with the BA session that can be reset at the second AP, or an indication of the traffic flow corresponding to the BA session.

[0008] In some examples, the second frame includes a response to the first frame and the expiration time of the BA session, where the BA session is invalid if the STA fails to roam to the second AP.

[0009] In some examples, at least one parameter is: i) an information item providing the latest sequence number to be used, ii) AP scoreboard parameters such that when the second AP begins sending frames to the STA, the second AP starts from the last state of the AP scoreboard parameters at the first AP, iii) STA scoreboard parameters such that the STA continues communication from the last state of the STA scoreboard parameters as if it were communicating with the first AP before roaming, or iv) BA session-related parameters.

[0010] In some examples, the second frame is sent after a BA session is established with the second AP.

[0011] In some examples, the first frame is received after roaming from the first AP to the second AP; and the processor is also configured to: determine that all buffered frames have been sent to the STA or the second AP; and based on the determination that all buffered frames have been sent to the STA or the second AP, terminate the BA session with the STA.

[0012] In some examples, the processor is also configured to send a third frame to the STA indicating the ability to support the transfer of the BA session.

[0013] In some examples, the first AP and the second AP are attached to a seamless roaming domain.

[0014] One aspect of this disclosure provides a first access point (AP) in a wireless network, comprising: a memory; and a processor coupled to the memory. The processor is configured to: receive a first frame from a slave station (STA) triggering the establishment of a block acknowledgment (BA) session at a second AP. The processor is configured to: communicate with the second AP to establish the BA session or at least one parameter associated with the BA session. The processor is configured to send a second frame to the STA in response to the first frame.

[0015] In some examples, the first frame indicates that the BA session establishment is for the second AP.

[0016] In some examples, the first frame is received before the STA roams to the second AP, and the first frame includes at least one of the following: an indication of roaming intent or a set of parameters for the BA session.

[0017] One aspect of this disclosure provides a station (STA) in a wireless network, including: a memory; and a processor coupled to the memory. The processor is configured to: send a first frame to a first access point (AP), the first frame triggering a transfer of a block acknowledgment (BA) session or at least one parameter associated with the BA session to a second AP. The processor is configured to: receive a second frame from the first AP or the second AP in response to the first frame, wherein the first AP communicates with the second AP to transfer the BA session or the at least one parameter associated with the BA session.

[0018] In some examples, the first frame includes at least one of the following: an indication of intent to roam from the first AP to the second AP, an indication of the BA session to be transferred, an indication of the sequence number or one or more parameters associated with the BA session that can be reset at the second AP, or an indication of the traffic flow corresponding to the BA session.

[0019] In some examples, the second frame includes a response to the first frame and the expiration time of the BA session, where the BA session is invalid if the STA fails to roam to the second AP.

[0020] In some examples, at least one parameter is: i) an information item providing the latest sequence number to be used, ii) AP scoreboard parameters such that when the second AP begins sending frames to the STA, the second AP starts from the last state of the AP scoreboard parameters at the first AP, iii) STA scoreboard parameters such that the STA continues communication from the last state of the STA scoreboard parameters as if it were communicating with the first AP before roaming, or iv) BA session-related parameters.

[0021] In some examples, the second frame is received after a BA session has been established with the second AP.

[0022] In some examples, the first frame is sent after roaming from the first AP to the second AP, and the processor is also configured to receive all buffered frames from the first AP.

[0023] In some examples, the processor is also configured to receive a third frame from the first AP indicating the ability to support the transfer of the BA session.

[0024] In some examples, the processor is also configured to send a third frame to the second AP to terminate the BA session.

[0025] In some examples, the first AP and the second AP are attached to a seamless roaming domain.

[0026] One aspect of this disclosure provides a method performed by a first access point (AP) in a wireless network. The method includes: receiving a first frame from a slave station (STA), the first frame triggering a transfer block acknowledgment (BA) session to a second AP. The method includes: communicating with the second AP to transfer the BA session or at least one parameter associated with the BA session. The method includes sending a second frame to the STA in response to the first frame.

[0027] In some examples, the first frame includes at least one of the following: an indication of intent to roam from the first AP to the second AP, an indication of the BA session to be transferred, an indication of the sequence number or one or more parameters associated with the BA session that can be reset at the second AP, or an indication of the traffic flow corresponding to the BA session.

[0028] In some examples, the second frame includes a response to the first frame and the expiration time of the BA session, where the BA session is invalid if the STA fails to roam to the second AP.

[0029] In some examples, at least one parameter is: i) an information item that provides the latest sequence number to be used, ii) AP scoreboard parameters such that when the second AP begins to send frames to the STA, the second AP starts from the last state of the AP scoreboard parameters at the first AP, iii) STA scoreboard parameters such that the STA continues to communicate from the last state of the STA scoreboard parameters as if it were communicating with the first AP before roaming, or iv) BA session-related parameters.

[0030] In some examples, the second frame is sent after a BA session is established with the second AP.

[0031] In some examples, the first frame is received after roaming from the first AP to the second AP. In some examples, the method includes determining that all buffered frames have been sent to the STA or the second AP. The method includes terminating the BA session with the STA based on determining that all buffered frames have been sent to the STA or the second AP.

[0032] In some examples, the method includes sending a third frame to the STA indicating the ability to support the transfer of the BA session.

[0033] In some examples, the first AP and the second AP are attached to a seamless roaming domain.

[0034] One aspect of this disclosure provides a method performed by a first access point (AP) in a wireless network. The method includes: receiving a first frame from a slave station (STA) that triggers the establishment of a block acknowledgment (BA) session at a second AP. The method includes: communicating with the second AP to establish the BA session or at least one parameter associated with the BA session. The method includes sending a second frame to the STA in response to the first frame.

[0035] In some examples, the first frame indicates that the BA session establishment is for the second AP.

[0036] In some examples, the first frame is received before the STA roams to the second AP, and the first frame includes an indication of roaming intent or at least one of the parameters in the BA session's parameter set.

[0037] One aspect of this disclosure provides a method performed by a station (STA) in a wireless network. The method includes: sending a first frame to a first access point (AP), the first frame triggering a transfer block acknowledgment (BA) session to a second AP or at least one parameter associated with the BA session. The method also includes: receiving a second frame from the first AP or the second AP in response to the first frame, wherein the first AP communicates with the second AP to transfer the BA session or the at least one parameter associated with the BA session.

[0038] In some examples, the first frame includes at least one of the following: an indication of intent to roam from the first AP to the second AP, an indication of the BA session to be transferred, an indication of the sequence number or one or more parameters associated with the BA session that can be reset at the second AP, or an indication of the traffic flow corresponding to the BA session.

[0039] In some examples, the second frame includes a response to the first frame and the expiration time of the BA session, where the BA session is invalid if the STA fails to roam to the second AP.

[0040] In some examples, at least one parameter is: i) an information item providing the latest sequence number to be used, ii) AP scoreboard parameters such that when the second AP begins sending frames to the STA, the second AP starts from the last state of the AP scoreboard parameters at the first AP, iii) STA scoreboard parameters such that the STA continues communication from the last state of the STA scoreboard parameters as if it were communicating with the first AP before roaming, or iv) BA session-related parameters.

[0041] In some examples, the second frame is received after a BA session has been established with the second AP.

[0042] In some examples, the first frame is sent after roaming from the first AP to the second AP. In some examples, the method includes receiving all buffered frames from the first AP.

[0043] In some examples, the method includes receiving a third frame from the first AP indicating the ability to support the transfer of the BA session.

[0044] In some examples, the method includes sending a third frame to the second AP to terminate the BA session.

[0045] In some examples, the first AP and the second AP are attached to a seamless roaming domain.

[0046] According to this disclosure, an efficient process is provided for transferring a BA session from one AP to another. Attached Figure Description

[0047] Figure 1 An example of a wireless network according to an embodiment is shown.

[0048] Figure 2a An example of an AP according to an embodiment is shown.

[0049] Figure 2b An example of a STA according to an embodiment is shown.

[0050] Figure 3 An example of multi-link communication operation according to an embodiment is shown.

[0051] Figure 4 The stages of the mobility handover process according to an embodiment are shown.

[0052] Figure 5 A BA session transfer according to an embodiment is illustrated.

[0053] Figure 6 The establishment of a BA session at the target AP is illustrated according to an embodiment.

[0054] Figure 7 A flowchart of an example procedure for BA session transfer by a non-AP STA, according to an embodiment, is shown.

[0055] Figure 8 A flowchart of an example process for BA session transfer by AP according to an embodiment is shown.

[0056] In one or more embodiments, not all components depicted in each figure are necessary, and one or more embodiments may include additional components not shown in the figures. Variations in the arrangement and type of components may be made without departing from the scope of this subject matter disclosure. Additional components, different components, or fewer components may be utilized within the scope of this subject matter disclosure. Detailed Implementation

[0057] The detailed description set forth below in conjunction with the accompanying drawings is intended to describe various embodiments and is not intended to represent the only embodiments in which the subject matter can be practiced. Rather, this detailed description includes specific details to provide a thorough understanding of the subject matter of the invention. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the scope of this disclosure. Therefore, the drawings and description are to be considered illustrative rather than restrictive in nature. The same reference numerals denote the same elements.

[0058] The following description pertains to certain implementations for the purpose of describing the innovative aspects of this disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in a variety of different ways. The examples in this disclosure are based on WLAN communication in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, including the IEEE 802.11be standard and any future revisions to the IEEE 802.11 standard. However, the described embodiments can be implemented in any device, system, or network capable of transmitting and receiving radio frequency (RF) signals according to the IEEE 802.11 standard, Bluetooth standard, Global System for Mobile Communications (GSM), GSM / General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunking Radio (TETRA), Wideband CDMA (W-CDMA), Evolved Data Optimized (EV-DO), 1xEV-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 used for communication within wireless, cellular, or Internet of Things (IoT) networks, such as systems utilizing 3G, 4G, 5G, 6G, or further implementations thereof.

[0059] Depending on the network type, other well-known terms may be used instead of "access point" or "AP," such as "router" or "gateway." 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 also be referred to as a STA. Furthermore, depending on the network type, other well-known terms may be used instead of "station" or "STA," such as "mobile station," "subscriber station," "remote terminal," "user equipment," "wireless terminal," or "user device." For convenience, the terms "station" and "STA" are used in this disclosure to refer to a remote wireless device that wirelessly accesses an AP or competes for a wireless channel in a WLAN, whether the STA is a mobile device (such as a mobile phone or smartphone) or is generally considered a fixed device (such as a desktop computer, AP, media player, fixed sensor, television, etc.).

[0060] Multilink Operation (MLO) is a key feature currently being developed by the standards body for next-generation Ultra High Throughput (EHT) Wi-Fi systems in IEEE 802.11be. Wi-Fi devices that support MLO are called Multilink Devices (MLDs). Using MLO, a non-AP MLD can discover, authenticate, associate, and establish multiple links with an AP MLD. Channel access and frame switching can occur on each link between the AP MLD and non-AP MLDs.

[0061] Figure 1 An example of a wireless network 100 according to an embodiment is shown. Figure 1 The illustrated embodiment of the wireless network 100 is for illustrative purposes only. Other embodiments of the wireless network 100 may be used without departing from the scope of this disclosure.

[0062] like Figure 1 As shown, wireless network 100 may include multiple wireless communication devices. Each wireless communication device may include one or more stations (STAs). An STA may be a logical entity that is a separate addressable instance of an interface to the Media Access Control (MAC) layer and Physical (PHY) layer of the wireless medium. STAs may be classified as Access Point (AP) STAs and Non-Access Point (Non-AP) STAs. An AP STA may be an entity that provides access to distribution system services to an associated STA via the wireless medium. A Non-AP STA may be a STA that is not included within an AP-STA. For simplicity, an AP STA may be referred to as an AP, and a Non-AP STA may be referred to as a STA. Figure 1In the example, APs 101 and 103 are wireless communication devices, each of which may include one or more AP STAs. In such an embodiment, APs 101 and 103 may be AP multilink devices (MLDs). Similarly, STAs 111-114 are wireless communication devices, each of which may include one or more non-AP STAs. In such an embodiment, STAs 111-114 may be non-AP MLDs.

[0063] AP 101 and AP 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 to multiple stations 111-114 in the coverage area 120 of AP 101. AP 101 and 103 can communicate with each other and with STAs using Wi-Fi or other WLAN communication technologies.

[0064] Depending on the network type, other well-known terms may be used instead of "access point" or "AP," such as "router" or "gateway." 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 also be referred to as a STA. Furthermore, depending on the network type, other well-known terms may be used instead of "station" or "STA," such as "mobile station," "subscriber station," "remote terminal," "user equipment," "wireless terminal," or "user device." For convenience, the terms "station" and "STA" are used in this disclosure to refer to a remote wireless device that wirelessly accesses an AP or competes for a wireless channel in a WLAN, whether the STA is a mobile device (such as a mobile phone or smartphone) or is generally considered a fixed device (such as a desktop computer, AP, media player, fixed sensor, television, etc.).

[0065] exist Figure 1 In the diagram, the dashed lines indicate the approximate extent of the coverage areas 120 and 125 of AP 101 and AP 103, which are shown as approximately circular for illustrative and explanatory purposes. It should be clearly understood that, depending on the configuration of the APs, the coverage areas associated with the APs (such as coverage areas 120 and 125) may have other shapes, including irregular shapes.

[0066] As described in more detail below, one or more APs in an AP may include circuitry and / or programming for the management of MU-MIMO and OFDMA channel detection in a WLAN. Although Figure 1 An example of a wireless network 100 is shown, but more details can be found on other wireless networks. Figure 1Various modifications can be made. For example, wireless network 100 can include any number of APs and any number of STAs in any suitable arrangement. Furthermore, AP 101 can communicate directly with any number of STAs and provide them with wireless broadband access to network 130. Similarly, each AP 101 and AP 103 can communicate directly with network 130 and provide STAs with direct wireless broadband access to network 130. Additionally, AP 101 and / or AP 103 can provide access to other or additional external networks, such as external telephone networks or other types of data networks.

[0067] Figure 2a An example of AP 101 according to an embodiment is shown. Figure 2a The embodiment of AP 101 shown is for illustrative purposes, and Figure 1 AP 103 can have the same or similar configuration. However, APs have a wide variety of configurations, and Figure 2a This disclosure is not intended to limit the scope to any particular implementation of AP.

[0068] like Figure 2a As shown, AP 101 may include multiple antennas 204a-204n, multiple radio frequency (RF) transceivers 209a-209n, transmit (TX) processing circuitry 214, and receive (RX) processing circuitry 219. AP 101 may also include a controller / processor 224, a memory 229, and a backhaul or network interface 234. RF transceivers 209a-209n receive incoming RF signals from antennas 204a-204n, such as signals transmitted by STAs in network 100. RF transceivers 209a-209n down-convert the incoming RF signals to generate intermediate (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. RX processing circuitry 219 sends the processed baseband signals to controller / processor 224 for further processing.

[0069] TX processing circuit 214 receives analog or digital data (such as voice data, network data, email, or interactive video game data) from controller / processor 224. TX processing circuit 214 encodes, multiplexes, and / or digitizes the outgoing baseband data to generate a processed baseband or IF signal. RF transceivers 209a-209n receive the processed baseband or IF signal from TX processing circuit 214 and up-convert the baseband or IF signal into an RF signal transmitted via antennas 204a-204n.

[0070] The controller / processor 224 may include one or more processors or other processing devices that control the overall operation of the AP 101. For example, the controller / processor 224 may control the RF transceivers 209a-209n, the RX processing circuitry 219, and the TX processing circuitry 214 to receive uplink signals and transmit downlink signals, based on well-known principles. The controller / processor 224 may also support additional functions, such as more advanced wireless communication capabilities. For example, the controller / processor 224 may support beamforming or directional routing operations, where outgoing signals from multiple antennas 204a-204n are weighted differently to effectively direct outgoing signals in a desired direction. The controller / processor 224 may also support OFDMA operations, where outgoing signals are assigned to different subcarrier subsets for different receivers (e.g., different STAs 111-114). The controller / processor 224 may support a variety of other functions in the AP 101, including combining DLMU-MIMO and OFDMA in the same transmission opportunity. In some examples, controller / processor 224 may include at least one microprocessor or microcontroller. Controller / processor 224 is also capable of executing programs and other processes, such as an operating system, residing in memory 229. Controller / processor 224 may move data into or out of memory 229 as needed for the execution process.

[0071] The controller / processor 224 is also coupled to a backhaul or network interface 234. The backhaul or network interface 234 allows the AP 101 to communicate with other devices or systems via a backhaul connection or over a network. Interface 234 can support communication via any suitable wired or wireless connection. For example, interface 234 can allow the AP 101 to communicate with a larger network (such as the Internet) via a wired or wireless local area network or via a wired or wireless connection. Interface 234 can include any suitable structure that supports communication via a wired or wireless connection, such as an Ethernet or RF transceiver. Memory 229 is coupled to the controller / processor 224. A portion of memory 229 can include RAM, and another portion of memory 229 can include flash memory or other ROM.

[0072] As described in more detail below, AP 101 may include circuitry and / or procedures for managing the channel detection process in a WLAN. Although Figure 2a An example of AP 101 is shown, but it is possible to compare it with other versions. Figure 2a Various changes can be made. For example, AP101 can include any number of... Figure 2aEach component shown. As a specific example, the AP may include multiple interfaces 234, and the controller / processor 224 may support routing functionality to route data between different network addresses. As another example, although shown as a single instance including TX processing circuitry 214 and a single instance including RX processing circuitry 219, AP 101 may include multiple instances of each (e.g., one for each RF transceiver). Alternatively, only one antenna and RF transceiver path may be included, as in a conventional AP. Moreover, Figure 2a The various components can be combined, further subdivided, or omitted, and additional components can be added as needed.

[0073] like Figure 2a As shown, in some embodiments, AP 101 may be an AP MLD comprising multiple APs 202A-202N. Each AP 202a-202n is attached to AP MLD 101 and includes multiple antennas 204a-204n, multiple radio frequency (RF) transceivers 209a-209n, transmit (TX) processing circuitry 214, and receive (RX) processing circuitry 219. Each AP 202a-202n may communicate independently with the controller / processor 224 and other components of AP MLD 101. Figure 2a The diagram shows that each AP 202a-202n has multiple separate antennas, but each AP 202a-202n can share multiple antennas 204a-204n without requiring separate multiple antennas. Each AP 202a-202n can represent the physical (PHY) layer and the lower media access control (MAC) layer.

[0074] Figure 2b An example of STA 111 according to an embodiment is shown. Figure 2b The embodiment of STA 111 shown is for illustrative purposes, and Figure 1 STAs 111-114 can have the same or similar configurations. However, STAs appear in a wide variety of configurations, and Figure 2b This disclosure is not intended to limit the scope of any particular implementation of STA.

[0075] like Figure 2b As shown, STA 111 may include one or more antennas 205, an RF transceiver 210, a TX processing circuit 215, a microphone 220, and an RX processing circuit 225. STA 111 may also include a speaker 230, a controller / processor 240, an input / output (I / O) interface (IF) 245, a touchscreen 250, a display 255, and a memory 260. The memory 260 may include an operating system (OS) 261 and one or more applications 262.

[0076] RF transceiver 210 receives incoming RF signals transmitted by the AP of network 100 from antenna 205. RF transceiver 210 down-converts the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are sent to RX processing circuitry 225, which generates processed baseband signals by filtering, decoding, and / or digitizing the baseband or IF signals. RX processing circuitry 225 sends the processed baseband signals to speaker 230 (e.g., for voice data) or to controller / processor 240 for further processing (e.g., for web browsing data).

[0077] TX processing circuitry 215 receives analog or digital voice data from microphone 220, or other outgoing baseband data (such as web data, email, or interactive video game data) from controller / processor 240. TX processing circuitry 215 encodes, multiplexes, and / or digitizes the outgoing baseband data to generate a processed baseband or IF signal. RF transceiver 210 receives the processed outgoing baseband or IF signal from TX processing circuitry 215 and up-converts the baseband or IF signal into an RF signal transmitted via antenna 205.

[0078] The controller / processor 240 may include one or more processors and executes a basic OS program 261 stored in memory 260 to control the overall operation of STA 111. In one such operation, the controller / processor 240 controls the RF transceiver 210, RX processing circuitry 225, and TX processing circuitry 215 to receive downlink signals and transmit uplink signals according to well-known principles. The controller / processor 240 may also include processing circuitry configured to provide management of the channel detection process in the WLAN. In some examples, the controller / processor 240 may include at least one microprocessor or microcontroller.

[0079] The controller / processor 240 is also capable of executing other processes and programs residing in the memory 260, such as operations for managing channel sensing processes in the WLAN. The controller / processor 240 can move data into or out of the memory 260 as needed for the execution of the process. In some examples, the controller / processor 240 is configured to execute multiple applications 262, such as applications for channel sensing, including feedback calculations based on received Null Data Packet Advertisements (NDPA) and Null Data Packets (NDP), and sending beamforming feedback reports in response to trigger frames (TF). The controller / processor 240 can operate the multiple applications 262 based on the OS program 261 or in response to signals received from the AP. The controller / processor 240 is also coupled to an I / O interface 245, which provides the STA 111 with the ability to connect to other devices such as laptops and handheld computers. The I / O interface 245 is the communication path between these accessories and the main controller / processor 240.

[0080] The controller / processor 240 is also coupled to input 250 (e.g., a touchscreen) and display 255. An operator of STA 111 can use input 250 to input data into STA 111. Display 255 may be a liquid crystal display, a light-emitting diode display, or other display capable of displaying text and / or at least limited graphics (such as from a website). Memory 260 is coupled to the controller / processor 240. A portion of memory 260 may include random access memory (RAM), and another portion of memory 260 may include flash memory or other read-only memory (ROM).

[0081] although Figure 2b An example of STA 111 is shown, but it is possible to compare it with other models. Figure 2b Make various changes. For example, Figure 2b The various components can be combined, further subdivided, or omitted, and additional components can be added as needed. In a specific example, STA 111 may include any number of antennas 205 for MIMO communication with AP 101. In another example, STA 111 may 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 graphics processing units (GPUs). Furthermore, although... Figure 2b The STA 111 is shown configured as a mobile phone or smartphone, but the STA can be configured to operate as other types of mobile or fixed devices.

[0082] like Figure 2bAs shown, in some embodiments, STA 111 may be a non-AP MLD comprising multiple STAs 203A-203N. Each STA 203a-203n is attached to the non-AP MLD 111 and includes an antenna 205, an RF transceiver 210, a TX processing circuit 215, and an RX processing circuit 225. Each STA 203a-203n may independently communicate with the controller / processor 240 and other components of the non-AP MLD 111. Figure 2b It is shown that each STA 203a-203n has a separate antenna, but each STA 203a-203n can share antenna 205 without requiring a separate antenna. Each STA 203a-203n can represent the physical (PHY) layer and the lower media access control (MAC) layer.

[0083] Figure 3 An example of multi-link communication operation according to an embodiment is shown. Multi-link communication operation can be used in the IEEE 802.11be standard and any future revisions of the IEEE 802.11 standard. Figure 3 In the middle, AP MLD 310 can be Figure 1 Wireless communication devices 101 and 103 are included, and the non-AP MLD 220 can be... Figure 1 One of the wireless communication devices 111-114 in the series.

[0084] like Figure 3 As shown, AP MLD 310 may include multiple auxiliary APs, such as AP 1, AP 2, and AP 3. Each auxiliary AP may include a PHY interface to the wireless medium (Link 1, Link 2, or Link 3). AP MLD 310 may include a single MAC Service Access Point (SAP) 318 through which the auxiliary APs of AP MLD 310 communicate with higher layers (Layer 3 or network layer). Each auxiliary AP of AP MLD 310 may have a different MAC address (lower MAC address) than any other auxiliary AP of AP MLD 310. AP MLD 310 may have an MLD MAC address (upper-layer MAC address), and the auxiliary APs share a single MAC SAP 318 to Layer 3. Therefore, the auxiliary APs share a single IP address, and Layer 3 identifies AP MLD 310 by assigning a single IP address.

[0085] A non-AP MLD 320 may include multiple affiliated STAs, such as 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). A non-AP MLD 320 may include a single MAC SAP 328, through which affiliated STAs communicate with higher layers (Layer 3 or network layer). Each affiliated STA of a non-AP MLD 320 may have a different MAC address (lower MAC address) than any other affiliated STA of the non-AP MLD 320. A non-AP MLD 320 may have an MLD MAC address (upper MAC address), and the affiliated STAs share the single MAC SAP 328 to Layer 3. Therefore, affiliated STAs share a single IP address, and Layer 3 identifies the non-AP MLD 320 by assigning this single IP address.

[0086] AP MLD 310 and non-AP MLD 320 can establish multiple links between their associated APs and STAs. In this example, AP 1 and STA 1 can establish Link 1, operating in the 2.4 GHz band. Similarly, AP 2 and STA 2 can establish Link 2, operating in the 5 GHz band, and AP 3 and STA 3 can establish Link 3, operating in the 6 GHz band. Each link can independently enable channel access and frame exchange between AP MLD 310 and non-AP MLD 320, which can increase data throughput and reduce latency. When associated with an AP MLD on a set of links (link establishment), each non-AP device is assigned a unique Association Identifier (AID).

[0087] The following documents are incorporated herein by reference in their entirety, as if fully set forth herein: i) IEEE 802.11-2020, “Wireless LAN Media Access Control (MAC) and Physical Layer (PHY) Specification”, ii) IEEE 802.11ax-2021, “Wireless LAN Media Access Control (MAC) and Physical Layer (PHY) Specification”, and iii) IEEE P802.11be / D5.0, “Wireless LAN Media Access Control (MAC) and Physical Layer (PHY) Specification”.

[0088] When a user moves around the environment while holding the STA device, the signal strength from the STA to its connected AP can change. If the user's movement causes a significant decrease in signal strength, a handover may be necessary. During the handover process, the STA can switch from its currently associated AP to a new AP.

[0089] Figure 4The stages of a mobility handover process according to an embodiment are shown. Figure 4 As shown, in a traditional device without any mobility support, the handover process may involve several steps, including detection phase 401, search phase 403, 802.11 authentication phase 405, 802.11 association phase 407, 802.1X authentication phase 409, and 802.11 resource reservation phase 411.

[0090] During detection phase 401, the STA can determine that a handover is necessary. The process for detecting the need for a handover can be vendor-specific. For example, a particular vendor implementation may choose to trigger a handover when the signal strength of the currently associated AP drops below a certain threshold.

[0091] The detection phase 401 can be followed by the search phase 403. During the search phase 403, the STA can search for new APs to associate with. During the search phase 403, the STA can perform a scan of different channels to identify nearby APs. This can be done passively, for example, by listening to beacons on a specific channel, or actively, for example, by using a probe request and response process.

[0092] After the scanning process is complete, the next step is to perform 802.11 authentication (based on Open Systems / Shared Key) 405. Once the STA is authenticated, the next step is to perform 802.11 association 807. The 802.1X authentication phase 409, introduced in the IEEE 802.1i amendment, can include EAP authentication between the STA and the AAA server with the assistance of the AP. Finally, during the 802.11 resource reservation phase 411, the STA can establish various resources at the new AP. For example, the STA can perform QoS reservation, BA establishment, and other operations with the newly associated AP.

[0093] Typically, during handover, connections may be interrupted when the establishment process operates in a break-before-make manner. This can impact user experience, especially for multimedia services, which may suffer session interruptions due to the high latency encountered during handover.

[0094] To reduce handover latency, numerous procedures have been introduced into several standards. These procedures focus on eliminating or reducing latency encountered at various steps of the handover process. In 2008, the IEEE 802.11r standard introduced fast transition roaming, which eliminates the need for an authentication step during handover. In 2011, IEEE 802.11k introduced assisted roaming, which reduces the search phase by allowing the STA to request the AP to send channel information for candidate neighbor APs. In 2011, IEEE 802.11v also introduced network-assisted roaming to assist the search phase. In IEEE 802.11be, the fast BSS transition procedure was extended to cover MLO operations. This procedure helps reduce latency encountered due to 802.11 resource reservations. However, the STA may still need to perform association and authentication phases, which may take, for example, 10 milliseconds.

[0095] This document describes the block acknowledgment (ACK) session transfer procedure according to this disclosure. In some examples, a block ACK (BA) session and / or its parameters can be transferred from one AP to another. BA session transfer can be completed before, during, or after roaming.

[0096] This document describes a pre-roaming BA session transfer procedure according to this disclosure. In some examples, a non-AP STA or AP may initiate the BA session transfer procedure before roaming occurs. This procedure can be initiated by the requesting entity transmitting an indication message. The indication message may include at least one or more of the information items indicated in Table 1.

[0097] [Table 1]

[0098] The above information items can be sent together or separately. They can be sent as part of any existing frame, element, field, or subfield in the standard, or they can be part of a newly defined frame, element, field, or subfield.

[0099] Table 2 provides examples of intent indication parameters.

[0100] [Table 2]

[0101] Table 3 provides example information items that can indicate link information.

[0102] [Table 3]

[0103] Table 4 provides examples of traffic flow indication parameters.

[0104] [Table 4]

[0105] In some examples, either the current AP or a non-AP STA can initiate a handover process. When the current AP initiates a handover, it can do so via a wired network or over the air. When a non-AP STA hands over a BA session, it can do so over the air by sending an indication message to the target AP.

[0106] In some examples, upon receiving an indication message, the target AP (which may be referred to herein as the new AP) may generate a response message that can be sent to a non-AP STA. The response message may include at least one or more of the information items shown in Table 5.

[0107] Table 5 provides examples of information items that can exist in a response message.

[0108] [Table 5]

[0109] The above information items can be sent together or separately. They can be sent as part of any existing frame / element / field / subfield in the standard, or they can be part of a newly defined frame / element / field / subfield.

[0110] Figure 5 A BA session transition according to an embodiment is illustrated. Although one or more operations are described or illustrated in a specific order, in other embodiments, the operations may be rearranged in a different order, which may include performing multiple operations in at least partially overlapping time periods. Specifically, Figure 5 The communication between a non-AP STA, the current AP, and the target AP is illustrated. The non-AP STA sends an indication message 501 to the current AP requesting a BA session transfer. In some examples, this indication message may include at least one or more of the information items shown in Table 1. Specifically, the indication message may include a roaming indication providing an indication of roaming intent, a BA session indication indicating the BA session to be transferred, and various other information.

[0111] Therefore, the current AP communicates with the target AP to perform a BA session transfer 503. The current AP then sends a response message 505 to the non-AP STA. The response message may include at least one or more of the information items shown in Table 5. Specifically, the response message may include a response to the parameters requested in the instruction message (e.g., the final values ​​of the parameters in Table 1), and a roaming deadline providing the deadline by which the non-AP STA needs to roam to the target AP before it.

[0112] This document describes a BA session transfer during roaming according to this disclosure. In some examples, a non-AP STA or AP can initiate a BA session transfer procedure during roaming. In some examples, when initiated during roaming, if the BA session transfer requires more than a threshold duration, the non-AP STA or AP can also provide an indication of the default mode to be used by the AP. This allows the non-AP STA to continue its data transmission in the default mode (e.g., using the basic BA mechanism instead of its variants) until a BA session has been established with the target AP. In some examples, for the default mode, the sequence number can be reset at the target AP, and one or more parameters associated with the BA session can be reset. When the BA is established at the target AP, the target AP can send an acknowledgment message to the non-AP STA for indication. Thereafter, the non-AP STA can use the BA session parameters for its operation.

[0113] In some examples, a non-AP STA can continue to operate with the current AP even before a BA session transfer confirmation has been received.

[0114] In some examples, if no BA session transfer confirmation is received within the timeout period, the non-AP STA can migrate to the target AP and re-establish the BA session.

[0115] In some examples, BA session indication and response messages can be part of a message exchanged to initiate roaming.

[0116] This document describes a BA transfer session after roaming according to this disclosure. In some examples, a non-AP STA can restart its BA session establishment process after roaming. When no BA session is established, a non-AP STA can operate in basic operating mode.

[0117] In some examples, a non-AP STA can request to transfer its BA session from the old AP as long as the data continuity protocol causes the clearing of cached frames at the old AP. The old AP can then delete the non-AP BA session after the cached frames at the old AP have been sent to the non-AP STA or transferred to the target AP.

[0118] This document describes the transfer parameters according to this disclosure. In some examples, when transferring a BA session, one or more of the parameters shown in Table 6 may be transferred.

[0119] Table 6 provides examples of BA session parameters that can be transmitted during roaming.

[0120] [Table 6]

[0121] The above parameters can be transmitted over the air or via a wired network.

[0122] This document describes the block ACK session establishment process according to this disclosure. In some examples, a non-AP STA can initiate a new BA session before roaming to a target AP. In some examples, a non-AP STA can send an indication message. This indication message may include at least one or more information items from the information items indicated for a new BA session as shown in Table 1. In some examples, there may be an indication that the setting is for the target AP rather than the current AP. In some examples, the indication may be made via a new ADDBA frame, which can be used to establish a new BA session at the target AP during roaming. Upon receiving the ADDBA message, the target AP can generate an ADDBA response message that can be transmitted to the non-AP.

[0123] Figure 6 An example procedure for establishing a BA session at a target AP according to an embodiment is shown. Although one or more operations are described or shown in a specific order, in other embodiments, the operations may be rearranged in a different order, which may include performing multiple operations in at least partially overlapping time periods. Specifically, Figure 6 The communication between a non-AP STA, the current AP, and the target AP is illustrated. The non-AP STA sends an ADDBA request frame 601 to the current AP to establish a new BA session at the target AP. Therefore, the current AP communicates with the target AP 603 to establish the new BA session. Specifically, upon receiving the ADDBA request frame 601, the target AP is able to generate an ADDBA response message that can be transmitted to the non-AP. Therefore, the current AP sends an ADDBA response frame 605 to the non-AP STA.

[0124] This document describes the deletion of a transferred or established BA session according to this disclosure. In some examples, after a non-AP STA transfers a BA session or establishes a new BA session at the target AP, the non-AP STA may want to cancel the established BA session. For example, the application that established the BA session for its service may no longer be running. In some examples, the non-AP STA can do this by sending a delete message. In some examples, a modified Delete Block Ack (DELBA) frame may exist, which may carry an indication about where the BA referred to was established at the target AP.

[0125] In some examples, a non-AP can indicate to its current AP its intention to reuse a BA established at the target AP. The current AP can provide confirmation with a migration time value. Before or after this confirmation, the current AP can move the BA session and related parameters to the target AP.

[0126] In some examples, the current AP can indicate to a non-AP STA its intention to transfer the BA session and related parameters to the target AP. The current AP can provide an acknowledgment message to the non-AP STA upon completion of the transfer.

[0127] This document describes capability announcements according to this disclosure. In some examples, an AP and / or a non-AP STA that supports the BA session transfer procedure can announce the capability. In some examples, capability announcements can be made via a capability bit, which can be indicated with a predetermined value (e.g., 1) and with another predetermined value (e.g., 0) for other indications. Capability announcements can be made via management frames (e.g., beacon, probe response, etc. for APs, and probe request, (re)association request, etc. for non-APs).

[0128] In some examples, the AP-to-AP block Ack session transfer procedure can be performed by the AP itself. In other examples, the AP-to-AP block Ack session transfer procedure can be performed by the logical entity that handles mobility management procedures.

[0129] Figure 7 A flowchart illustrating an example procedure for BA session transfer by a non-AP STA, according to an embodiment, is shown. Although one or more operations are described or shown in a specific order, in other embodiments, the operations may be rearranged in a different order, which may include performing multiple operations in at least partially overlapping time periods. Figure 7 The flowchart depicted in the diagram illustrates the situation in non-AP STA (such as...) Figure 3 The operations performed in the STA shown in the figure.

[0130] In procedure 700, during operation 701, the non-AP STA sends an indication message to the current AP to transfer the BA session to the target AP. In some examples, the indication message may include at least one or more of the information items shown in Table 1. Specifically, the indication message may include a roaming indication providing an indication of roaming intent, a BA session indication indicating the BA session to be transferred, and various other information.

[0131] In operation 703, the non-AP STA receives a response message from the current AP or the target AP. The response message may include at least one or more of the information items shown in Table 5. Specifically, the response message may include a response to a requested parameter in the indication message (e.g., the final value of the parameter in Table 1) and a roaming deadline providing the deadline before which the non-AP STA needs to roam to the target AP.

[0132] In Operation 705, the non-AP STA communicates with the target AP.

[0133] Figure 8 According to an embodiment, a flowchart of an example procedure for BA session transfer by an AP is shown. Although one or more operations are described or shown in a specific order, in other embodiments, the operations may be rearranged in a different order, which may include performing multiple operations in at least partially overlapping time periods. Figure 8 The flowchart depicted in the diagram illustrates the process in AP (such as...) Figure 3 The operations performed in the AP shown in the figure.

[0134] In process 800, during operation 801, the AP receives an indication message from a non-AP STA to transfer a BA session to the target AP. In some examples, the indication message may include at least one or more of the information items shown in Table 1. Specifically, the indication message may include a roaming indication providing an indication of roaming intent, a BA session indication indicating the BA session to be transferred, and various other information.

[0135] In Operation 803, the AP communicates with the target AP to perform a BA session transfer.

[0136] In operation 805, the AP sends a response message to the non-AP STA regarding the BA session transfer. The response message may include at least one or more of the information items shown in Table 5. Specifically, the response message may include a response to the requested parameters in the indication message (e.g., the final values ​​of the parameters in Table 1), and a roaming deadline providing the deadline by which the non-AP STA needs to roam to the target AP before it. As described herein, embodiments of this disclosure are applicable to multi-link operations, but are not limited to single-link operations.

[0137] Embodiments of this disclosure provide a BA session transfer between a current AP MLD and a target AP MLD, which provides efficient wireless mobility management. Specifically, embodiments of this disclosure allow a non-AP STA to roam from the current AP MLD to the target AP MLD, and the BA session can be transferred to the target AP, thereby avoiding the need to terminate the BA session with the current AP and reset a new BA session with the target AP. This minimizes service interruptions or delays that would otherwise occur during these termination and setup processes.

[0138] Unless otherwise specified, references to singular elements are not intended to indicate one and only one, but rather one or more. For example, a “one” module can refer to one or more modules. In the absence of further constraints, elements preceded by “a,” “an,” “the,” or “the” do not preclude the presence of additional identical elements.

[0139] Titles and subtitles (if any) are used for convenience only and do not limit the invention. Words exemplified are used to indicate that they are intended as examples or illustrations. Where terms such as “comprising,” “having,” or similar are used, they are intended to adopt an open-ended meaning similar to “comprise”; wherein “comprise” refers to its meaning as interpreted as a transitional term in a claim. Relational terms such as “first” and “second” can be used to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between these entities or actions.

[0140] Phrases such as aspect, that aspect, on the other hand, some aspects, one or more aspects, implementation, that implementation, another implementation, some implementations, one or more implementations, embodiment, that embodiment, another embodiment, some examples, one or more embodiments, configuration, that configuration, another configuration, some configurations, one or more configurations, subject matter, disclosure, this disclosure, other variations thereof, etc., are for convenience and do not imply that disclosures associated with such phrases are essential to the subject matter, or that such disclosures apply to all configurations of the subject matter. Disclosures associated with such phrases may apply to all configurations or one or more configurations. Disclosures associated with such phrases may provide one or more examples. Phrases such as aspect or some aspects may refer to one or more aspects, and vice versa, and this similarly applies to other foregoing phrases.

[0141] The phrase "at least one" preceding a series of items, separated by the terms "and" or "or," modifies the list as a whole, rather than each member of the list. The phrase "at least one of..." does not require the selection of at least one item; rather, it allows for the inclusion of at least one of any one item, and / or at least one of any combination of items, and / or at least one of each item. For example, each of the phrases "at least one of A, B, and C" or "at least one of A, B, or C" refers to only A, only B, or only C; any combination of A, B, and C; and / or at least one of each of A, B, and C.

[0142] It should be understood that the specific order or hierarchy of the disclosed steps, operations, or processes is an illustration of exemplary methods. Unless otherwise expressly stated, it should be understood that the specific order or hierarchy of steps, operations, or processes may be performed in a different order. Some steps, operations, or processes may be performed simultaneously, or may be performed as part of one or more other steps, operations, or processes. The appended method claims (if any) present elements of various steps, operations, or processes in a sample order, but this does not imply limitation to the specific order or hierarchy presented. These may be performed serially, linearly, in parallel, or in different orders. It should be understood that the described instructions, operations, and systems can generally be integrated together into a single software / hardware product or packaged into multiple software / hardware products.

[0143] This disclosure is provided to enable any person skilled in the art to practice the various aspects described herein. In some cases, well-known structures and components are shown in block diagram form to avoid obscuring the concept of the subject matter. This disclosure provides various examples of the subject matter, and the subject matter is not limited to these examples. Various modifications to these aspects will be apparent to those skilled in the art, and the principles described herein can be applied to other aspects.

[0144] All structural and functional equivalents of the various aspects described herein, whether now or hereafter known to a person skilled in the art, are expressly incorporated herein by reference and are intended to be covered by the claims. Furthermore, nothing disclosed herein is intended to be offered to the public, whether or not such disclosure is explicitly stated in the claims. No claim element is to be interpreted pursuant to paragraph 6 of 35 US.C. § 112 unless it is expressly stated using the phrase “means for…” or, in the case of a method claim, using the phrase “steps for…”.

[0145] The title, background information, description of the drawings, abstract, and figures are incorporated herein by reference and are provided as illustrative examples rather than as limiting descriptions. It should be understood at the time of filing that they are not intended to limit the scope or meaning of the claims. Furthermore, in the detailed description, it will become apparent that the description provides illustrative examples and that various features are combined in various embodiments for the purpose of simplifying the disclosure. The approach of this disclosure should not be construed as reflecting an intention to require more features than expressly recited in each claim. Rather, as reflected in the following claims, the inventive subject matter lies in all features of fewer than those in a single disclosure configuration or operation. The appended claims are incorporated herein by reference, wherein each claim is independently claimed as a separate subject matter.

[0146] The claims are not intended to be limited to the aspects described herein, but rather to conform to the full scope consistent with the language claims and to include all legal equivalents. Nevertheless, no claim is intended to include subject matter that does not meet the requirements of applicable patent law, nor should it be interpreted in this way.

Claims

1. A station (STA) (111) in a wireless network, comprising: Memory (260); and A processor (240) coupled to the memory, the processor (240) being configured to: Send a first frame to a first access point (AP), the first frame triggering a transfer block acknowledgment (BA) session to a second AP or at least one parameter associated with the BA session; Receive a second frame in response to the first frame from the first AP or the second AP, wherein the first AP communicates with the second AP to transfer the BA session or the at least one parameter associated with the BA session.

2. The STA according to claim 1, wherein, The first frame includes at least one of the following: an indication of intent to roam from the first AP to the second AP, an indication of the BA session to be transferred, an indication of the ability to reset the sequence number or one or more parameters associated with the BA session at the second AP, or an indication of the service flow corresponding to the BA session.

3. The STA according to claim 1 or 2, wherein, The second frame includes a response to the first frame and the expiration time of the BA session, wherein the BA session is invalid if the STA fails to roam to the second AP.

4. The STA according to any one of the preceding claims, wherein, The at least one parameter is: i) an information item providing the latest sequence number to be used, ii) AP scoreboard parameters such that when the second AP begins to send frames to the STA, the second AP starts from the last state of the AP scoreboard parameters at the first AP, iii) STA scoreboard parameters such that the STA continues to communicate from the last state of the STA scoreboard parameters as if communicating with the first AP before roaming, or iv) BA session-related parameters.

5. The STA according to any one of the preceding claims, wherein, The second frame was received after the BA session was established with the second AP.

6. The STA according to any one of the preceding claims, wherein, The first frame is sent after roaming from the first AP to the second AP, wherein the processor is further configured to: Receive all buffered frames from the first AP.

7. The STA according to any one of the preceding claims, wherein, The processor (240) is also configured to: A third frame is received from the first AP, the third frame indicating the ability to support the transfer of the BA session.

8. The STA according to any one of the preceding claims, wherein, The processor (240) is also configured to: Send a third frame to the second AP to terminate the BA session.

9. The STA according to any one of the preceding claims, wherein, The first AP and the second AP are attached to a seamless roaming domain.

10. A first access point (AP) (101) in a wireless network, comprising: Memory (229); and Processor (224), coupled to memory (229), processor (224) is configured to: The first frame of the transfer from the primary station (STA) to the second access point (AP) is received in the trigger block acknowledgment (BA) session. Communicate with the second AP to transfer the BA session or at least one parameter associated with the BA session; and In response to the first frame, a second frame is sent to the STA.

11. The first AP according to claim 10, wherein, The first frame includes at least one of the following: an indication of intent to roam from the first AP to the second AP, an indication of the BA session to be transferred, an indication of the ability to reset the sequence number or one or more parameters associated with the BA session at the second AP, or an indication of the service flow corresponding to the BA session.

12. The first AP according to claim 10 or 11, wherein, The second frame includes a response to the first frame and the expiration time of the BA session, wherein the BA session is invalid if the STA fails to roam to the second AP.

13. A first access point (AP) (101) in a wireless network, comprising: Memory (229); and Processor (224), coupled to the memory, wherein processor (224) is configured to: The slave station (STA) receives the first frame that triggers the establishment of a block acknowledgment (BA) session at the second access point; Communicating with the second AP to establish the BA session or at least one parameter associated with the BA session; and In response to the first frame, a second frame is sent to the STA.

14. The first AP according to claim 13, wherein, The first frame indicates that the BA session establishment is for the second AP.

15. The first AP according to claim 13 or 14, wherein, The first frame is received before the STA roams to the second AP, and the first frame includes at least one indication of roaming intent or a set of parameters for the BA session.

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