Method and apparatus for low latency communication in wireless local area network system

Abstract

The invention provides a low-delay communication method and device in a wireless local area network system. Provided is a method performed by a station (STA) in a wireless local area network system, the method comprising the steps of: performing at least one of transmission and reception by using a first chain in a first link; performing at least one of transmitting and receiving by using the second link in the second link; receiving an initial frame for starting an enhanced multi-link multi-radio frequency (EMLMR) operation in the first link; switching the second link from the second link to the first link on the basis of the initial frame; transmitting information for sending the data frame on the second link; switching the second link from the first link to the second link on the basis of the information; receiving a trigger frame in the second link; and transmitting the data frame in the second link on the basis of at least one of the information and the trigger frame.

Description

Technical Field

[0001] This invention relates to a wireless local area network (WLAN) system, and more specifically, to a method and apparatus for low-latency communication in a WLAN system. Background Technology

[0002] Recently, with the widespread adoption of mobile devices, wireless LAN technology, which provides fast wireless communication services to mobile devices, has attracted attention. Wireless LAN technology is a technology that uses wireless communication to enable mobile devices (such as smartphones, tablets, laptops, portable multimedia players, embedded devices, etc.) to wirelessly access the internet.

[0003] As applications requiring higher throughput and / or real-time transmission emerge, extended frequency bandwidth and / or efficient retransmission operations can be supported in wireless LANs. Furthermore, simultaneous use of multiple channels or multiple links can be supported.

[0004] On the other hand, the techniques described in the background section are written to improve the understanding of the background of the present invention, and may include content that is not yet known to those skilled in the art to which the present invention pertains. Summary of the Invention

[0005] Technical issues The present invention aims to provide a method and apparatus for rapidly transmitting data stored in a wireless local area network (WLAN) terminal during data reception from another WLAN terminal in a wireless local area network (WLAN) system.

[0006] This invention aims to provide a method and apparatus for rapidly transmitting data stored in a terminal and requiring low latency in a wireless local area network system.

[0007] This invention aims to provide a method and apparatus for requesting scheduling in a wireless local area network system to transmit data during data reception.

[0008] This invention aims to provide a method and apparatus for a terminal to perform multi-link, multi-radio operation to rapidly transmit data requiring low latency in a wireless local area network system.

[0009] The technical objectives to be achieved in this invention are not limited to those described above, and those skilled in the art who apply the technical configuration of this invention may consider other technical objectives not mentioned herein from the embodiments of the invention described below.

[0010] Technical solution According to an embodiment of the present invention, a method performed by a station (STA) in a wireless local area network system includes: performing at least one of transmitting and receiving on a first link; performing at least one of transmitting and receiving on a second link; receiving an initial frame on the first link for initiating enhanced multi-link multi-radio (EMLMR) operation; switching the second link from the second link to the first link based on the initial frame; transmitting information for the transmission of data frames on the second link; switching the second link from the first link to the second link based on the information; receiving a trigger frame on the second link; and transmitting data frames on the second link based on at least one of the information and the trigger frame.

[0011] A method performed by an access point (AP) in a wireless local area network system includes: transmitting an initial frame on a first link to initiate EMLMR operation; transmitting information for the transmission of data frames on a second link; receiving information approving the use of the second link; and transmitting data frames on the second link.

[0012] According to another embodiment of the present invention, a method performed by an AP in a wireless local area network system includes: transmitting an initial frame for initiating EMLMR operation on a first link; receiving information for the transmission of data frames on a second link; transmitting a trigger frame on the second link; and receiving data frames on the second link based on the information.

[0013] According to another embodiment of the present invention, a method performed by a STA in a wireless local area network system includes: performing at least one of transmitting and receiving on a first link using a first link; performing at least one of transmitting and receiving on a second link using a second link; receiving an initial frame on the first link for initiating EMLMR operation; switching the second link to the first link based on the initial frame; receiving information for the transmission of data frames on the second link; switching the second link from the first link to the second link based on the information; sending information approving the use of the second link; and receiving delay-sensitive data on the second link based on the information.

[0014] According to another embodiment of the present invention, a STA in a wireless local area network system includes a transceiver and a processor coupled to the transceiver, and the processor is configured to: perform at least one of transmitting and receiving on a first link using a first link; perform at least one of transmitting and receiving on a second link using a second link; receive an initial frame for initiating EMLMR operation on the first link; switch the second link (RF link) to the first link based on the initial frame and first information; transmit information for the transmission of data frames on the second link; switch the second link from the first link to the second link based on the information; receive a trigger frame on the second link; and transmit data frames on the second link based on at least one of the information and the trigger frame.

[0015] According to another embodiment of the present invention, an access point (AP) in a wireless local area network system includes a transceiver and a processor coupled to the transceiver, and the processor is configured to: transmit an initial frame for initiating EMLMR operation on a first link; transmit information for transmitting data frames on a second link; receive information approving the use of the second link; and transmit data frames on the second link.

[0016] Beneficial effects According to the present invention, a wireless local area network (WLAN) terminal and a communication method are provided, which can request to share a TXOP obtained by another WLAN terminal, so as to quickly transmit data requiring low latency during communication in the WLAN system.

[0017] According to the present invention, a wireless local area network (WLAN) terminal and a communication method are provided, which can quickly transmit data that requires low-latency transmission, thereby reducing the data transmission latency in the WLAN system.

[0018] According to the present invention, a wireless local area network terminal and a communication method can be provided, which can rapidly transmit data using multiple links.

[0019] The effects obtained in this invention are not limited to those described above, and those skilled in the art of applying the technical configurations of this invention can clearly deduce and understand other effects not mentioned above from the following description of the embodiments of this invention. That is, those skilled in the art can also deduce unintended effects in implementing the configurations described in this invention from the embodiments of this invention. Attached Figure Description

[0020] Figure 1 A block diagram of a communication node in a wireless local area network system is shown.

[0021] Figure 2 This illustrates the concept of multiple links set up between multi-link devices (MLDs) in a wireless local area network system.

[0022] Figure 3a A first implementation of a low-latency transmission method for EMLMR wireless local area networks is shown.

[0023] Figure 3b A second implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0024] Figure 4a A third implementation scheme of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0025] Figure 4bA fourth implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0026] Figure 5a A fifth implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0027] Figure 5b A sixth implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0028] Figure 6a A seventh implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0029] Figure 6b An eighth embodiment of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0030] Figure 7 A ninth implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0031] Figure 8 A tenth embodiment of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0032] Figure 9 An eleventh implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0033] Figure 10a A twelfth embodiment of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0034] Figure 10b A thirteenth implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0035] Figure 11 A flowchart of a method for operating the STA according to an embodiment of the present invention is shown.

[0036] Figure 12 A flowchart of a method for operating an AP according to an embodiment of the present invention is shown.

[0037] Figure 13 A flowchart of a method for operating an AP according to an embodiment of the present invention is shown.

[0038] Figure 14 A flowchart of a method for operating the STA according to an embodiment of the present invention is shown. Detailed Implementation

[0039] In the following description, embodiments of the invention will be specifically described with reference to the accompanying drawings to enable those skilled in the art to readily implement the embodiments. However, the invention may be embodied in different forms and is not limited to the embodiments described herein.

[0040] In describing this invention, detailed descriptions of known functions and configurations will be omitted where such descriptions might obscure the subject matter. Additionally, in the accompanying drawings, portions irrelevant to the description of the invention are omitted, and the same reference numerals refer to the same parts.

[0041] In this invention, when a component is "connected," "linked," or "coupled" to another component, it may include not only a direct connection but also an indirect connection between the two components. Furthermore, when a component "comprises" or "has" other components, this means that other components may be further included without excluding them, unless the context clearly indicates otherwise.

[0042] In this invention, terms such as first, second, etc., are used only for the purpose of distinguishing one component from other components, and the order or importance of components is not limited unless otherwise stated. Accordingly, within the scope of this invention, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0043] In this invention, the distinction between components is intended to clearly describe each of their characteristics, and does not necessarily imply that the components are separate from each other. That is, multiple components may be integrated to form a single hardware or software unit, or a single component may be distributed to form multiple hardware or software units. Accordingly, such integrated or distributed implementations are included within the scope of this invention, even if not specifically mentioned.

[0044] In this invention, the components described in the various embodiments do not necessarily represent essential components, and some of these components may be optional. Accordingly, embodiments comprising a subset of the components described in one embodiment are also included within the scope of this invention. Furthermore, embodiments including other components besides those described in the various embodiments are also included within the scope of this invention.

[0045] In this invention, for ease of description, expressions of positional relationships used herein are provided, such as above, below, left, and right, and the positional relationships described in the specification can be interpreted in reverse when the accompanying drawings shown in the specification are viewed in reverse.

[0046] The following describes a wireless local area network (WLAN) communication system applying embodiments of the present invention. The WLAN communication system applying embodiments of the present invention is not limited to the following description, and the embodiments of the present invention can be applied to various WLAN communication systems. The WLAN communication system may also be referred to as a "wireless local area network" or a "wireless local area network system".

[0047] Figure 1 A block diagram of a communication node in a wireless local area network system is shown.

[0048] refer to Figure 1 Communication node 100 can be an access point (AP), a station (STA), an AP multi-link device (MLD), or a non-AP MLD. STAs can be non-AP STAs. The operating channel width supported by the AP can be 20 MHz, 80 MHz, or 160 MHz, etc. The operating channel width supported by the STA can be 20 MHz or 80 MHz.

[0049] Communication node 100 may include at least one processor 110, memory 120, and at least one transmitting / receiving device 130 connected to a network and performing communication. Transmitting / receiving device 130 may also be referred to as a transceiver, radio frequency (RF) unit, or RF module. Additionally, communication node 100 may further include an input interface device 140, an output interface device 150, and a storage device 160. Components included in communication node 100 can be connected via bus 170 and perform communication between them.

[0050] However, each component included in communication node 100 may be connected not via common bus 170, but via a separate interface or separate bus around processor 110. For example, processor 110 may be connected via a dedicated interface to at least one of memory 120, transmitting / receiving device 130, input interface device 140, output interface device 150, and storage device 160.

[0051] Processor 110 can execute program instructions stored in at least one of memory 120 and storage device 160. Processor 110 can be a central processing unit (CPU), graphics processing unit (GPU), or dedicated processor that performs methods according to embodiments of the present invention. Memory 120 and storage device 160 can each be configured as at least one volatile storage medium and at least one non-volatile storage medium. For example, memory 120 can be configured as at least one read-only memory (ROM) and random access memory (RAM).

[0052] Figure 2 The concept of multiple links set up between multiple link devices (MLDs) in a wireless local area network system is illustrated.

[0053] refer to Figure 2 An MLD can have a medium access control (MAC) address. In an implementation, the MLD can be an AP MLD and / or a non-AP MLD. The MAC address of the MLD can be used in the multi-link establishment process between the non-AP MLD and the AP MLD. The MAC address of the AP MLD can be different from the MAC address of the non-AP MLD. APs associated with an AP MLD can have different MAC addresses, and STAs associated with a non-AP MLD can have different MAC addresses. An AP existing in an AP MLD and having a different MAC address can be responsible for the corresponding link and act as an independent AP.

[0054] A STA residing in a non-AP MLD and having a different MAC address can be responsible for the corresponding link and act as an independent STA. A non-AP MLD can be referred to as a STA MLD. An MLD can support simultaneous transmit and receive (STR) operations. In this case, the MLD can perform transmit operations on link 1 and receive operations on link 2. An MLD supporting STR operations can be referred to as a STR MLD (e.g., a STR AP MLD or a STR non-AP MLD). In implementations, a link can be a channel or a frequency band. A device that does not support STR operations can be referred to as a non-STR (NSTR) AP MLD or an NSTR non-AP MLD (or an NSTR STA MLD).

[0055] MLDs can utilize discontinuous bandwidth extension schemes (e.g., 80 MHz + 80 MHz) to send and receive frames on multiple links. Multi-link operation can include multi-band transmission. An AP MLD can include multiple APs, and these APs can operate on different links. Each AP can perform lower-level MAC layer functions. Each AP can be referred to as a "communication node" or a "lower-level entity." A communication node (i.e., an AP) can be configured according to the upper layer (or...) Figure 1 The processor 110 shown is operated under the control of the processor. A non-AP MLD may include multiple STAs, and these STAs may operate on different links. Each STA may be referred to as a "communication node" or a "lower-level entity." A communication node (e.g., an STA) can operate according to the control of an upper layer (or...). Figure 1 The processor 110 shown is operated under its control.

[0056] MLDs can perform communication across multiple frequency bands. For example, an MLD can perform communication using a 40 MHz bandwidth in the 2.4 GHz band, and a 160 MHz bandwidth in the 5 GHz band, depending on a channel extension scheme (e.g., a bandwidth extension scheme). An MLD can also perform communication using a 160 MHz bandwidth in the 5 GHz band and a 160 MHz bandwidth in the 6 GHz band. A single frequency band (e.g., a single channel) used by an MLD can be defined as a single link. Alternatively, multiple links can be configured within a single frequency band used by an MLD. For example, an MLD can configure one link in the 2.4 GHz band and two links in the 6 GHz band. The links can be referred to as Link 1, Link 2, and Link 3, respectively. Alternatively, the links can be referred to as Link 1, Link 2, and Link 3, respectively. Link numbers can be set by the AP, and an identifier (ID) can be assigned to each link.

[0057] A Multi-Link Ledger (MLD) (e.g., an AP MLD and / or a non-AP MLD) can configure multiple links by executing access and / or negotiation procedures for multi-link operation. In this case, the number of links and / or the links to be used among the multiple links can be configured. A non-AP MLD (e.g., a STA) can identify information about the frequency bands that can communicate with the AP MLD. During the multi-link operation negotiation procedure between the non-AP MLD and the AP MLD, the non-AP MLD can configure one or more links supported by the AP MLD for multi-link operation. A STA that does not support multi-link operation (e.g., a STA according to IEEE 802.11 a / b / g / n / ac / ax) can access one or more links supported by the AP MLD.

[0058] When the frequency band gaps between multiple links (e.g., the frequency band gap between link 1 and link 2 in the frequency domain) are sufficient, the MLD can perform STR operations. For example, the MLD can use link 1 to transmit Physical Layer Convergence Procedure (PLCP) Protocol Data Unit (PPDU) 1 and can use link 2 to receive PPDU 2. On the other hand, when the frequency band gaps between multiple links are insufficient and the MLD performs STR operations, in-device coexistence (IDC) interference may occur, that is, interference between multiple links. Accordingly, when the frequency band gaps between multiple links are insufficient, the MLD may not be able to perform STR operations. The link pairs in the above interference relationship can be link pairs restricted to non-simultaneous transmit and receive (NSTR). Here, the MLD can be an NSTR AP MLD or an NSTR non-AP MLD.

[0059] For example, multiple links, including Link 1, Link 2, and Link 3, can be set up between the AP MLD and the non-AP MLD 1. When the band gap between Link 1 and Link 3 is sufficient, the AP MLD can perform STR operations using Link 1 and Link 3. That is, the AP MLD can use Link 1 to send frames and use Link 3 to receive frames. When the band gap between Link 1 and Link 2 is insufficient, the AP MLD may not be able to perform STR operations using Link 1 and Link 2. When the band gap between Link 2 and Link 3 is insufficient, the AP MLD may not be able to perform STR operations using Link 2 and Link 3.

[0060] On the other hand, in a wireless LAN system, a negotiation process for multi-link operation can be performed during the access process between the STA and the AP.

[0061] A device that supports multiple links (e.g., an AP or a STA) can be called a multi-link device (MLD). An AP that supports multiple links can be called an AP MLD, and an STA that supports multiple links can be called a non-AP MLD or a STA MLD. An AP MLD can have a physical address (e.g., a MAC address) for each link. An AP MLD can be implemented as if an AP were independently responsible for each link. Multiple APs can be managed within a single AP MLD. Accordingly, coordination can be performed between multiple APs belonging to the same AP MLD. A STA MLD can have a physical address (e.g., a MAC address) for each link. A STA MLD can be implemented as if an STA were independently responsible for each link. Multiple STAs can be managed within a single STA MLD. Accordingly, coordination can be performed between multiple STAs belonging to the same STA MLD.

[0062] For example, AP 1 of the AP MLD and STA 1 of the STA MLD can each be responsible for the first link and perform communication using the first link. AP 2 of the AP MLD and STA 2 of the STA MLD can each be responsible for the second link and perform communication using the second link. STA 2 can receive state change information for the first link on the second link. In this case, STAMLD can collect information received from each link (e.g., state change information) and control the operations performed by STA 1 based on the collected information.

[0063] Next, methods for transmitting and receiving data in a wireless local area network system will be described. When a method (e.g., signal transmission or reception) performed at a first communication node is described, a corresponding second communication node can perform a method (e.g., signal reception or transmission) corresponding to the method performed at the first communication node. That is, when the operation of a STA is described, its corresponding AP can perform an operation corresponding to the STA's operation. On the other hand, when the operation of an AP is described, its corresponding STA can perform an operation corresponding to the AP's operation. In the implementation, the operation of a STA can be interpreted as the operation of a STA MLD, the operation of a STA MLD can be interpreted as the operation of a STA, the operation of an AP can be interpreted as the operation of an AP MLD, and the operation of an AP MLD can be interpreted as the operation of an AP.

[0064] Figure 3a A first implementation of a low-latency transmission method for EMLMR wireless local area networks is shown.

[0065] Figure 3b A second implementation of the EMLMR low-latency transmission method for wireless local area networks is shown.

[0066] refer to Figure 3a and Figure 3b AP1 101 and STA1 103 can operate on the first link, and AP2 105 and STA2 107 can operate on the second link. AP1 101 and AP2 105 can be APs belonging to AP MLD1. STA1 103 and STA2 107 can be STAs belonging to STA MLD1. That is, the AP and STA operating on the first link of AP MLD1 and STA MLD1 can be AP1 101 and STA1 103 respectively, and the AP and STA operating on the second link of AP MLD1 and STA MLD1 can be AP2 105 and STA2 107 respectively.

[0067] STA MLD1 can be an MLD that supports EMLMR operation. STA MLD1 can perform EMLMR operation on both the first and second links. That is, the first and second links can be referred to as EMLMR links. In EMLMR operation, the STA MLD with multiple radios first receives an initial frame 300 from the AP on each of the multiple links, based on the spatial flow capability of each link via a determined number of spatial flows (NSS), and then switches the receive and transmit chains to the link that received the initial frame 300. The receive and transmit chains can be referred to as radio chain chains. The radio chain can be referred to as a radio module. After receiving the initial frame 300, the STA MLD can communicate with the AP MLD via the switched radio chain using the NSS set during the EMLMR setup process. To perform EMLMR operation, the STA MLD can send an enhanced multi-link operating mode notification (EML OMN) frame to the AP MLD. The EML OMN frame can include information about the MCS and NSS to be used in the EMLMR operation. The EML OMN frame is an action frame that includes EML control fields. When frame reception is complete, the STA MLD can switch the RF chain to the EMLMR link that did not receive the initial frame 300. Until frame reception is complete, the STA MLD cannot receive data on the EMLMR link that did not receive the initial frame 300. Until frame transmission is complete, the AP MLD cannot transmit data on the EMLMR link that did not receive the initial frame 300. When the STA MLD performs EMLMR operation on an EMLMR link and intends to transmit a frame to the AP MLD, the STA MLD's STA can switch the RF chain and transmit the frame to the AP MLD's AP using the MCS and NSS to be used for EMLMR operation. When the STA MLD's STA completes frame transmission, the STA MLD can operate on each of multiple links according to the spatial flow capabilities of each link. When the STA MLD's STA transmits a frame to the AP MLD's AP, the AP MLD cannot transmit frames to any STA other than the STA MLD's STA that performed the transmission.

[0068] On the first link, AP1 101 can execute a channel access procedure to send frames to STA1 103. The channel access procedure can be an EDCA backoff procedure. When the EDCA backoff procedure is successful, AP1 101 acquires a TXOP, which is a period of time during which multiple frames can be sent. That is, AP1 101 is the TXOP holder. AP1 101 can send an initial frame 300 to STA1 103. The per-link spatial stream capability of STA1 103 can be NSS=2. Accordingly, AP1 101 can use two spatial streams to send frames to STA1 103. STA1 103 can respond to AP1 101's frames using a Block Acknowledgment (BACK, BA) frame. STAMLD1 can switch the radio chain to the first link after receiving the initial frame 300 from AP1 101. STA MLD1 can perform transmission and reception in EMLMR operations through four spatial streams. In other words, the spatial stream capability exchanged in the EML OMN frame and used for EMLMR operation can be NSS=4. Accordingly, after STA MLD1 switches the RF chain to the first link, STA1103 can use four spatial streams to send or receive frames. AP1101 can use four spatial streams to send data frame 302 to STA1103. STA2107 cannot perform frame transmission. When STA MLD1 receives data frame 302 on the first link, there may be data that STA MLD1 wants to transmit on the second link. The data to be transmitted on the second link may be data that needs to be transmitted quickly. Accordingly, STA1103 of STA MLD1 can indicate a request to send and receive frames on another EMLMR link that STA MLD1 is not currently receiving on in the BA frame 304 sent to AP1101. This request can be called an EMLMR quick transmission request message. EMLMR fast transmission request information may include at least one of the following: a link bitmap, trigger frame request information, MCS-NSS information to be used on the indicated link, MCS-NSS information to be used on the current link, and delay limit information. The link bitmap may indicate the links that STA MLD1 intends to further utilize. For example, STA MLD1 may indicate a second link. The trigger frame request information is a request for trigger frame 306 to be used on the link indicated by STA MLD1 in the link bitmap. For example, since STA MLD1 indicates a second link in the link bitmap, AP2 105 of AP MLD1 may send a trigger frame to STA2 107 of STA MLD1 on the second link. The MCS-NSS information to be used on the indicated link indicates the MCS and NSS information supported on the link indicated by STA MLD1 in the link bitmap.STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information of the link indicated by STA MLD1 in the link bitmap. The MCS-NSS information to be used on the current link indicates the MCS and NSS information supported on the link in the initial exchange frame 300. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information of the link in the initial exchange frame 300. In another approach, STA MLD1 and AP MLD1 can operate according to the spatial flow capabilities of each link. Delay limit information is information indicating when STA MLD1 must send data to AP MLD1. For example, when STA specifies delay limit information as 1 ms, this indicates that STA expects to share TXOPs from the TXOP holder within 1 ms. Delay limit information may further include per AC or per TID time information. For example, STA may indicate delay limit information for each AC, such as 1 ms for AC_VO and 5 ms for AC_BE. Alternatively, the STA can indicate delay limit information for each TID, such as 1 ms for TID 1 and 3 ms for TID 3. Indications for delay limit information for each AC and for each TID can be used simultaneously. Based on the delay limit information, AP MLD1 can change the channel access parameters (e.g., EDCA parameters) used to transmit trigger frames or downlink frames on the link indicated by STA MLD1 in the link bitmap. The EMLMR fast transmission request information sent by STA1 103 to AP1 101 can be included in the MAC header of a QoS empty frame in the form of A-control and can be transmitted in the form of an A-MPDU aggregated with a BA frame. The EMLMR fast transmission request information can be auxiliary AP request+ (AAR+) information as extended AAR information. In another approach, the EMLMR fast transmission request information can be information configured in the form of A-control, or it can be included in the frame sent by STA1 103 to AP1 101 in the form of indicator bits, subfields, or information elements, or in any other form.

[0069] STA1 103 may send an EMLMR fast transmission request to AP1 101, which may request the transmission of a trigger frame 306 on the second link. Upon receiving a BA frame 304 including the EMLMR fast transmission request information sent by STA1 103, AP1 101 of AP MLD1 may include an indicator acknowledging the use of the second link in a downlink frame 308. The indicator acknowledging the use of the second link may indicate whether STA2 107 and AP2 105 are able to communicate on the second link. The indicator acknowledging the use of the second link may be configured in at least one form including an A-control field, subfield, indicator bit, and information element in the MAC header or MAC data frame. Alternatively, the indicator acknowledging the use of the second link may be indicated by a PHY preamble. For example, the indicator acknowledging the use of the second link may be indicated by a change in the number of spatial streams (NSS) of the transmitted PPDU (e.g., a decrease in NSS compared to a previous frame reception), and the change in NSS may be notified via a PHY preamble. Alternatively, the indicator confirming the use of the second link can be indicated based on changes in the NSS and MCS field values ​​of the user field included in the PHY preamble for Extremely High Throughput (EHT)-SIG or Ultra High Reliability (UHR)-SIG. When the backoff counter reaches zero, AP2 105 of APMLD1 can perform a channel access procedure (e.g., EDCA backoff operation) and send trigger frame 306 to STA2 107. The channel access procedure of AP2 105 can be performed faster based on the delay limit information of the EMLMR fast transmission request information sent by STA1 103 to AP1 101. Alternatively, even when the backoff counter reaches zero, if no EMLMR delay has elapsed since the end time of the transmission of BA frame 304 including the EMLMR fast transmission request from STA1 103, AP2 105 may not send trigger frame 306, but instead keep the backoff counter at zero. After the EMLMR delay has elapsed, AP2 105 can send trigger frame 306 to STA2 107. The EMLMR delay is the time required for STA MLD to switch radio chains to perform EMLMR operation. Since STA2 107 has not detected the channel on the second link for at least the predetermined time, STA2 107 can set a MediumSyncDelay timer on the second link.The length of the MediumSyncDelay timer can be set to a preset value, such as PPDUMaxTime, which is the maximum length of a PPDU. When the MediumSyncDelay timer operates, STA2 107 needs to perform a clear channel assessment (CCA) to determine whether the channel is occupied. CCA is a channel detection operation. When STA2 107 receives the trigger frame 306 from AP2 105, it initializes the MediumSyncDelay timer and can perform frame transmission and reception. The trigger frame 306 sent by AP2 105 to STA2 107 can indicate the length of the resource based on the EMLMR fast transmission request information sent by STA1 103 to AP1 101. STA2 107 can send a frame 310 requiring fast transmission to AP2 105. On the first link, AP1 101 and STA1 103 can use two spatial streams to send and receive frame 310 based on the EMLMR fast transmission request indicated by STA1 103. On the second link, AP2 105 and STA2 107 can use two spatial streams to send and receive frame 310 according to the EMLMR fast transmission request indicated by STA1 103.

[0070] refer to Figure 3b When the EMLMR delay time has elapsed after the duration of aSIFSTime + aSlotTime + aRxPHYStartDelay since the end of communication between AP2 105 and STA2 107 on the second link, AP1 101 and STA1 103 on the first link can perform communication operations based on the spatiotemporal flow capabilities of the EMLMR operation exchanged via EML OMN frames on the first link. For example, AP1 101 and STA1 103 can utilize four spatial flows to perform frame transmission and reception operations.

[0071] Figure 4a and Figure 4b This is a timing diagram illustrating the third and fourth implementation schemes of the EMLMR low-latency transmission method for wireless local area networks.

[0072] refer to Figure 4a and Figure 4bAP1 101 and STA1 103 can operate on the first link, and AP2 105 and STA2 107 can operate on the second link. AP1 101 and AP2 105 can be APs belonging to AP MLD1. STA1 103 and STA2 107 can be STAs belonging to STA MLD1. That is, the AP and STA operating on the first link of AP MLD1 and STA MLD1 can be AP1 101 and STA1 103 respectively, and the AP and STA operating on the second link of AP MLD1 and STA MLD1 can be AP2 105 and STA2 107 respectively.

[0073] STA MLD1 can be an MLD that supports EMLMR operation. STA MLD1 can perform EMLMR operation on a first link and a second link. That is, the first link and the second link can be referred to as EMLMR links. In EMLMR operation, the STA MLD with multiple radios first receives an initial frame 400 from the AP on each of the multiple links, based on the spatial flow capability of each link via a determined number of spatial flows (NSS), and then switches the receive chain and transmit chain to the link that received the initial frame 400. The receive chain and transmit chain can be referred to as radio chain. After receiving the initial frame 400, the STA MLD can communicate with the AP MLD via the switched radio chain using the NSS set during the EMLMR setup process. To perform EMLMR operation, the STA MLD can send an Enhanced Multi-Link Operation Mode Notification (EML OMN) frame to the AP MLD. The EML OMN frame can include information about the MCS and NSS to be used in the EMLMR operation. The EML OMN frame is an action frame that includes EML control fields. When frame reception is complete, the STA MLD can switch the radio chain to the EMLMR link that did not receive the initial frame 400. Until frame reception is complete, the STAMLD cannot receive data on an EMLMR link where the initial frame 400 has not been received. Until frame transmission is complete, the AP MLD cannot perform transmission on an EMLMR link where the initial frame 400 has not been received. When the STA MLD performs EMLMR operation on an EMLMR link and intends to transmit a frame to the AP MLD, the STA MLD's STA can switch radio chains and transmit the frame to the AP MLD using the MCS and NSS intended for EMLMR operation. When the STA MLD's STA completes frame transmission, the STA MLD can operate on each of multiple links according to the spatial flow capabilities of each link. When the STA MLD's STA transmits a frame to the AP MLD's AP, the AP MLD cannot transmit frames to any STA other than the STA MLD's STA that performed the transmission.

[0074] On the first link, AP1 101 can execute a channel access procedure to send frames to STA1 103. The channel access procedure can be an EDCA backoff procedure. When the EDCA backoff procedure is successful, AP1 101 acquires a TXOP, which is a period of time during which multiple frames can be sent. That is, AP1 101 is the TXOP holder. AP1 101 can send an initial frame 400 to STA1 103. The per-link spatial stream capability of STA1 103 can be NSS=2. Accordingly, AP1 101 can use two spatial streams to send frames to STA1 103. STA1 103 can respond to AP1 101's frames using a Block Acknowledgment (BA) frame. STA MLD1 can switch the RF chain to the first link after receiving the initial frame 400 from AP1 101. STA MLD1 can perform transmit and receive operations in EMLMR using four spatial streams. In other words, the spatial stream capability exchanged in the EML OMN frame and used for EMLMR operations can be NSS=4. Accordingly, after STA MLD1 switches the RF chain to the first link, STA1 103 can use four spatial streams to send or receive frames. AP1 101 can use the four spatial streams to send data frame 402 to STA1 103. STA2 107 cannot perform frame transmission. When STA MLD1 receives data frames on the first link, data that STA MLD1 needs to transmit on the second link may arise. The data to be transmitted on the second link may be data that needs to be transmitted quickly. Accordingly, STA1 103 of STA MLD1 may indicate a request to send and receive frames on another EMLMR link that STA MLD1 is not currently receiving on in a BA frame 404 sent to AP1 101. This request may be called EMLMR Fast Transmission Request Information. EMLMR Fast Transmission Request Information may include at least one of the following: a link bitmap, trigger frame request information, MCS-NSS information to be used on the indicated link, MCS-NSS information to be used on the current link, and delay limit information. The link bitmap may indicate the link that STA MLD1 intends to use further. For example, STA MLD1 can indicate a second link. The trigger frame request information is information requesting that trigger frame 406 be triggered on the link indicated by STA MLD1 in the link bitmap. For example, since STA MLD1 indicates a second link in the link bitmap, AP2 105 of AP MLD1 can send trigger frame 406 to STA2 107 of STA MLD1 on the second link. The MCS-NSS information to be used on the indicated link indicates the MCS and NSS information supported on the link indicated by STA MLD1 in the link bitmap. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information regarding the link indicated by STA MLD1 in the link bitmap.The MCS-NSS information to be used on the current link indicates the MCS and NSS information supported on the link in the initial exchange frame 400. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information of the link in the initial exchange frame 400. In another approach, STA MLD1 and AP MLD1 can operate based on the spatial flow capabilities of each link. Delay limit information is information indicating when STA MLD1 must send data to AP MLD1. For example, when STA specifies delay limit information as 1 ms, this indicates that STA expects to share TXOPs from the TXOP holder within 1 ms. Delay limit information may further include per-AC or per-TID time information. For example, STA may indicate delay limit information for each AC, such as 1 ms for AC_VO and 5 ms for AC_BE. Alternatively, STA may indicate delay limit information for each TID, such as 1 ms for TID 1 and 3 ms for TID 3. Indications for delay limit information for each AC and for each TID can be used simultaneously. Based on the delay limit information, AP MLD1 can change the channel access parameters (e.g., EDCA parameters) used to transmit trigger frame 406 or downlink frames on the link indicated by STA MLD1 in the link bitmap. The EMLMR fast transmission request information sent by STA1 103 to AP1 101 can be included in the MAC header of a QoS empty frame in the form of A-control and can be transmitted in the form of an A-MPDU aggregated with a BA frame. The EMLMR fast transmission request information can be auxiliary AP request+ (AAR+) information as extended AAR information. In another approach, the EMLMR fast transmission request information can be information configured in the form of A-control, or it can be included in the frame sent by STA1 103 to AP1101 in the form of indicator bits, subfields, or information elements, or in any other form.

[0075] STA1 103 may send an EMLMR fast transmission request to AP1 101, which may request the transmission of a trigger frame 406 on the second link. Upon receiving a BA frame 404 including the EMLMR fast transmission request information sent by STA1 103, AP1 101 of AP MLD1 may include an indicator acknowledging the use of the second link in a downlink frame 408. The indicator acknowledging the use of the second link may indicate whether STA2 107 and AP2 105 are able to communicate on the second link. The indicator acknowledging the use of the second link may be configured in at least one form including an A-control field, subfield, indicator bit, and information element in the MAC header or MAC data frame. Alternatively, the indicator acknowledging the use of the second link may be indicated by a PHY preamble. For example, the indicator acknowledging the use of the second link may be indicated by a change in the number of spatial streams (NSS) of the transmitted PPDU (e.g., a decrease in NSS compared to a previous frame reception), and the change in NSS may be notified via a PHY preamble. Alternatively, the indicator confirming the use of the second link can be based on changes in the NSS and MCS field values ​​of the user field included in the PHY preamble for Extremely High Throughput (EHT)-SIG or Ultra High Reliability (UHR)-SIG. For example, downlink frame 402 transmitted by AP1 101 of AP MLD1 before receiving the Fast Transmission Request message from STA MLD1 may have an NSS of 4 (that is, the NSS used for EMLMR operation). However, when the indicator confirming AP MLD1's use of the second link confirms that STA MLD1 is using the second link, the NSS of downlink frame 408 transmitted by AP1 101 of AP MLD1 after receiving the Fast Transmission Request message from STA MLD1 can be reduced from 4 (e.g., reduced from 4 to 2). That is, downlink frame 408 can be reduced to within the flow capacity of each link space before being transmitted. When the indicator confirming AP MLD1's use of the second link does not confirm STA MLD1's use of the second link, the NSS of the third downlink frame transmitted by AP MLD1's AP1 101 may remain at 4 instead of decreasing. When the second link requested by STA MLD1 is busy, AP MLD1 does not confirm STA MLD1's use of the second link. Alternatively, AP MLD1 may not confirm the use of the second link if at least one or more of the MCS-NSS information requested by STA MLD1 (e.g., MCS-NSS information to be used on the current link and MCS-NSS information to be used on the indicated link), delay limits, and trigger frame request information are not satisfied.

[0076] STA MLD1 checks and confirms the indicator for AP MLD1's use of the second link. If AP MLD1 does not confirm the use of the second link, STA MLD1 continues communication on the first link. When AP MLD1 confirms the use of the second link, STA MLD1 operates based on the MCS-NSS information requested by AP1 101 on both the first and second links (e.g., the MCS-NSS information to be used on the current link and the MCS-NSS information to be used on the indicated link). STA MLD1 may not immediately operate based on the MCS-NSS information to be used on the indicated link or the link space flow capabilities on the second link. For example, STA2 107 of STA MLD1 can operate after an EMLMR delay starting from the time point when the indicator confirming the use of the second link is acknowledged (e.g., the time point when STA1 103 of STA MLD1 first decodes the MAC header and / or MAC frame body included in the frame sent by AP1 101 of AP MLD1, or the time point when STA1 103 of STA MLD1 decodes the PHY preamble of frame 408 sent by AP1 101 and acknowledges the NSS). When the indicator confirming the use of the second link is indicated in the form of a PHY preamble, the operation of STA1 103 of STA MLD1 decoding the PHY preamble of frame 408 sent by AP1 101 and acknowledging the NSS can be performed as follows: The PHY layer of STA1 103 decodes the PHY preamble included in frame 408 of AP1 101. The PHY layer identifies the NSS of frame 408 transmitted by AP1 101 based on the preamble and generates primitives (e.g., PHY-RXSTART. indicator primitives including RXVECTOR information). The RXVECTOR information is physical layer information that directly or indirectly indicates the NSS. The PHY layer of STA1 103 sends PHY primitives to the MAC layer of STA1 103 (that is, the MAC sublayer below MLD). The MAC layer of STA1 103 can identify the NSS of frame 408 transmitted by AP1 101. Alternatively, instead of identifying the NSS, the MAC layer of STA1 103 can send PHY primitive information to the MAC layer of STA MLD1 (that is, the MAC sublayer above MLD), and the MAC layer of STA MLD1 can identify the NSS.

[0077] After AP1 of AP MLD1 sends an indicator confirming the use of the second link, or after AP1 101 receives the EMLMR fast transmission request information from STA1 103, AP2 105 of AP MLD1 can execute a channel access procedure (e.g., EDCA backoff operation) and send a trigger frame 406 to STA2 107 when the backoff counter reaches zero. The channel access procedure of AP2 105 can be executed more quickly based on the delay limit information of the EMLMR fast transmission request information sent by STA1 103 to AP1 101. Alternatively, even when the backoff counter reaches zero, if no EMLMR delay has elapsed since the first confirmation of the indicator confirming the use of the second link, AP2 105 may not send the trigger frame 406, but instead keep the backoff counter at zero. When an EMLMR delay has elapsed since the first confirmation of the indicator confirming the use of the second link, AP2 105 may send the trigger frame 406 to STA2 107. EMLMR delay is the time required for STA MLD to switch radio chains during EMLMR operation. Since STA2 107 has not detected the channel on the second link for at least a predetermined time, STA2 107 can set a MediumSyncDelay timer on the second link. The length of the MediumSyncDelay timer can be set to a preset value, for example, aPPDUMaxTime, which is the maximum length of the PPDU. When the MediumSyncDelay timer operates, STA2 107 needs to perform a free channel assessment (CCA) to determine if the channel is occupied. CCA is the channel detection operation. When STA2 107 receives trigger frame 406 from AP2 105, it initializes the MediumSyncDelay timer and can perform frame transmission and reception. The trigger frame 406 sent by AP2 105 to STA2 107 can indicate the length of the resource based on the EMLMR fast transmission request information sent by STA1 103 to AP1 101. STA2 107 can send a frame 410 indicating the need for fast transmission to AP2 105. On the first link, AP1 101 and STA1 103 can send and receive frame 410 using two spatial streams, based on the EMLMR fast transmission request indicated by STA1 103. On the second link, AP2 105 and STA2 107 can send and receive frame 410 using two spatial streams, based on the EMLMR fast transmission request indicated by STA1 103.

[0078] refer to Figure 4bWhen the EMLMR delay time has elapsed after the duration of aSIFSTime + aSlotTime + aRxPHYStartDelay since the end of communication between AP2 105 and STA2 107 on the second link, AP1 101 and STA1 103 on the first link can perform communication operations based on the spatiotemporal flow capabilities of the EMLMR operation exchanged via EML OMN frames on the first link. For example, AP1 101 and STA1 103 can utilize four spatial flows to perform frame transmission and reception operations.

[0079] Figure 5a and Figure 5b This is a timing diagram illustrating the fifth and sixth implementation schemes of the EMLMR low-latency transmission method for wireless local area networks.

[0080] refer to Figure 5a and Figure 5b AP1 101 and STA1 103 can operate on the first link, and AP2 105 and STA2 107 can operate on the second link. AP1 101 and AP2 105 can be APs belonging to AP MLD1. STA1 103 and STA2 107 can be STAs belonging to STA MLD1. That is, the AP and STA operating on the first link of AP MLD1 and STA MLD1 can be AP1 101 and STA1 103 respectively, and the AP and STA operating on the second link of AP MLD1 and STA MLD1 can be AP2 105 and STA2 107 respectively.

[0081] STA MLD1 can be an MLD that supports EMLMR operation. STA MLD1 can perform EMLMR operation on a first link and a second link. That is, the first link and the second link can be referred to as EMLMR links. In EMLMR operation, the STA MLD with multiple radios first receives an initial frame 500 from the AP on each of the multiple links, based on the spatial flow capability of each link via a determined number of spatial flows (NSS), and then switches the receive chain and transmit chain to the link that received the initial frame 500. The receive chain and transmit chain can be referred to as radio chain. After receiving the initial frame 500, the STA MLD can communicate with the AP MLD via the switched radio chain using the NSS set during the EMLMR setup process. To perform EMLMR operation, the STA MLD can send an Enhanced Multi-Link Operation Mode Notification (EML OMN) frame to the AP MLD. The EML OMN frame can include information about the MCS and NSS to be used in the EMLMR operation. The EML OMN frame is an action frame that includes EML control fields. When frame reception is complete, the STA MLD can switch the radio chain to the EMLMR link that did not receive the initial frame 500. Until frame reception is complete, the STAMLD cannot receive data on an EMLMR link where the initial frame 500 has not been received. Until frame transmission is complete, the AP MLD cannot perform transmission on an EMLMR link where the initial frame 500 has not been received. When the STA MLD performs EMLMR operation on an EMLMR link and intends to send a frame to the AP MLD, the STA MLD's STA can switch radio chains and send a frame to the AP MLD using the MCS and NSS intended for EMLMR operation. When the STA MLD's STA completes frame transmission, the STA MLD can operate on each of multiple links according to the spatial flow capabilities of each link. When the STA MLD's STA sends a frame to the AP MLD's AP, the AP MLD cannot send frames to any STA other than the STA MLD's STA that performed the transmission.

[0082] On the first link, AP1 101 can execute a channel access procedure to send frames to STA1 103. The channel access procedure can be an EDCA backoff procedure. When the EDCA backoff procedure is successful, AP1 101 acquires a TXOP, which is a period of time during which multiple frames can be sent. That is, AP1 101 is the TXOP holder. AP1 101 can send an initial frame 500 to STA1 103. The per-link spatial stream capability of STA1 103 can be NSS=2. Accordingly, AP1 101 can use two spatial streams to send frames to STA1 103. STA1 103 can respond to AP1 101's frames using a Block Acknowledgment (BA) frame. STA MLD1 can switch the RF chain to the first link after receiving the initial frame 500 from AP1 101. STA MLD1 can perform transmission and reception in EMLMR operations through four spatial streams. In other words, the spatial stream capability exchanged in the EML OMN frame and used for EMLMR operations can be NSS=4. Accordingly, after STA MLD1 switches the RF chain to the first link, STA1 103 can use four spatial streams to send or receive frames. AP1 101 can use the four spatial streams to send data frame 502 to STA1 103. STA2 107 cannot perform frame transmission. AP2 105 does not perform frame transmission to STA2 107. When AP MLD1 performs frame transmission on the first link, data may need to be transmitted to STA2 107 on the second link. The data to be transmitted on the second link may be data that needs to be transmitted quickly. Accordingly, AP1 101 of AP MLD1 may indicate a request to receive frames on another EMLMR link that STA1 103 is not currently receiving on in the data frame 502 sent to STA1 103. This request may be called RF handover request information. RF handover request information may include at least one of the following: a link bitmap, MCS-NSS information to be used on the indicated link, and MCS-NSS information to be used on the current link. The link bitmap can indicate the links that AP MLD1 intends to further use. For example, AP MLD1 can indicate a second link. The MCS-NSS information to be used on the indicated link indicates the MCS and NSS information supported by AP MLD1 on the link indicated in the link bitmap. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information about the link indicated by AP MLD1 in the link bitmap. The MCS-NSS information to be used on the current link indicates the MCS and NSS information supported on the link in the initial exchange frame 500. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information about the link in the initial exchange frame 500.In another approach, STA MLD1 and AP MLD1 can operate according to the spatial flow capabilities of each link. The radio frequency handover request information sent by AP1 101 to STA1 103 can be transmitted via the MAC header of a data frame included in the form of A-control. The radio frequency handover request information can be auxiliary AP Request+ (AAR+) information as extended AAR information. In another approach, the radio frequency handover request information can be information configured in the form of A-control, or it can be included in the frame sent by AP1 101 to STA1 103 in the form of indicator bits, subfields, or information elements, or in any other form.

[0083] After AP1 101 of AP MLD1 sends data frame 502, which includes radio frequency handover request information, to STA1 103, AP2 105 can perform a channel access procedure on the second link. The radio frequency handover request information is a request for STA MLD1 to receive frames on the second link. The channel access procedure can be an EDCA backoff operation. When the backoff counter reaches zero, AP2 105 of AP MLD1 can perform a channel access procedure (e.g., an EDCA backoff operation) and send downlink frame 506 to STA2 107. Alternatively, even when the backoff counter reaches zero, if no EMLMR delay has elapsed since the end of the transmission of data frame 502, which includes the radio frequency handover request information from AP1 101, AP2 105 may not send downlink data frame 506, but instead keep the backoff counter at zero. When the EMLMR delay has elapsed, AP2 105 can send downlink data frame 506 to STA2 107. EMLMR delay is the time required for the STA MLD switching radio chain to perform EMLMR operation.

[0084] In another approach, the transmission of data frame 506 by AP2 105 can be based on information included in BA frame 504 transmitted from STA1 103 to AP1 101. STA1 103 can respond to data frame 502 transmitted by AP1 101 by utilizing BA frame 504. BA frame 504 may further include information approving or rejecting the radio handover request transmitted from AP1 101 to STA1 103. When STA1 103 approves the radio handover request transmitted from AP1 101 in BA frame 504, AP MLD1 can perform a channel access procedure at AP2 105 on the second link. The channel access procedure may be an EDCA backoff operation. When the backoff counter reaches zero, AP2 105 of AP MLD1 can perform a channel access procedure (e.g., an EDCA backoff operation) and transmit downlink frame 506 to STA2 107. Even when the backoff counter reaches zero, if the EMLMR delay has not elapsed since the end of the transmission of BA frame 504 from STA1 103, AP2 105 may not send downlink data frame 506, but instead keep the backoff counter at zero. When the EMLMR delay has elapsed, AP2 105 may send downlink data frame 506 to STA2 107. The EMLMR delay is the time required for the STA MLD to switch radio chains during EMLMR operation. On the first link, AP1 101 and STA1 103 can use two spatial streams to send and receive frames according to the radio switching request indicated by AP1 101. On the second link, AP2 105 and STA2 107 can use two spatial streams to send and receive frame 506 according to the radio switching request indicated by AP1 101.

[0085] refer to Figure 5b When the EMLMR delay time has elapsed after the duration of aSIFSTime + aSlotTime + aRxPHYStartDelay since the end of communication between AP2 105 and STA2 107 on the second link, AP1 101 and STA1 103 on the first link can perform communication operations based on the spatiotemporal flow capabilities of the EMLMR operation exchanged via EML OMN frames on the first link. For example, AP1 101 and STA1 103 can utilize four spatial flows to perform frame transmission and reception operations.

[0086] Figure 6a and Figure 6b This is a timing diagram illustrating the seventh and eighth embodiments of the EMLMR low-latency transmission method for wireless local area networks.

[0087] refer to Figure 6a and Figure 6bAP1 101 and STA1 103 can operate on the first link, and AP2 105 and STA2 107 can operate on the second link. AP1 101 and AP2 105 can be APs belonging to AP MLD1. STA1 103 and STA2 107 can be STAs belonging to STA MLD1. That is, the AP and STA operating on the first link of AP MLD1 and STA MLD1 can be AP1 101 and STA1 103 respectively, and the AP and STA operating on the second link of AP MLD1 and STA MLD1 can be AP2 105 and STA2 107 respectively.

[0088] STA MLD1 can be an MLD that supports EMLMR operation. STA MLD1 can perform EMLMR operation on a first link and a second link. That is, the first link and the second link can be referred to as EMLMR links. In EMLMR operation, the STA MLD with multiple radios first receives an initial frame from the AP on each of the multiple links, based on the spatial flow capability of each link via a determined number of spatial flows (NSS), and then switches the receive chain and transmit chain to the link that received the initial frame. The receive chain and transmit chain can be referred to as radio chain. After receiving the initial frame, the STA MLD can communicate with the AP MLD via the switched radio chain using the NSS set during the EMLMR setup process. To perform EMLMR operation, the STA MLD can send an Enhanced Multi-Link Operation Mode Notification (EML OMN) frame to the AP MLD. The EML OMN frame can include information about the MCS and NSS to be used in the EMLMR operation. The EML OMN frame is an action frame that includes EML control fields. When frame reception is complete, the STA MLD can switch the radio chain to the EMLMR link that did not receive the initial frame. Until frame reception is complete, the STA MLD cannot receive data on an EMLMR link where the initial frame has not been received. Until frame transmission is complete, the AP MLD cannot perform transmission on an EMLMR link where the initial frame has not been received. When the STA MLD performs EMLMR operation on an EMLMR link and intends to transmit a frame to the AP MLD, the STA MLD's STA can switch radio chains and transmit the frame to the AP MLD using the MCS and NSS to be used for EMLMR operation. When the STA MLD's STA completes frame transmission, the STA MLD can operate on each of multiple links according to the spatial flow capabilities of each link. When the STA MLD's STA transmits a frame to the AP MLD's AP, the AP MLD cannot transmit frames to any STA other than the STA that performed the transmission.

[0089] On the first link, STA1 103 can execute a channel access procedure to send frames to AP1 101. The channel access procedure can be an EDCA backoff procedure. When the EDCA backoff procedure is successful, STA1 103 acquires a TXOP, which is a period of time during which multiple frames can be sent. That is, STA1 103 is the TXOP holder. STA1 103 can send frames to AP1 101. STA MLD1 can use four spatial streams for transmission and reception during EMLMR operation, therefore STA1 103 can use four spatial streams to send frames to AP1 101. In other words, the spatial stream capability exchanged in the EML OMN frame and used for EMLMR operation can be NSS=4. AP1 101 can respond to STA1 103's frames using a Block Acknowledgment (BA) frame 600. AP1 101 can use the four spatial streams to send data frames to STA1 103. STA2 107 cannot perform frame transmission. AP2 105 does not perform frame transmission to STA2 107. When AP MLD1 performs frame reception on the first link, data may need to be transmitted to STA2 107 on the second link. The data to be transmitted on the second link may be data that needs to be transmitted quickly. Accordingly, AP1 101 of AP MLD1 may indicate a request to receive frames on another EMLMR link that STA1 103 is not currently transmitting or receiving in a BA frame 600 sent to STA1 103. This request may be called radio frequency handover request information. Radio frequency handover request information may include at least one of the following: a link bitmap, MCS-NSS information to be used on the indicated link, and MCS-NSS information to be used on the current link. The link bitmap may indicate the link that AP MLD1 intends to use further. For example, AP MLD1 may indicate a second link. The MCS-NSS information to be used on the indicated link indicates the MCS and NSS information supported by AP MLD1 on the link indicated in the link bitmap. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information of the link indicated by AP MLD1 in the link bitmap. The MCS-NSS information to be used on the current link indicates the MCS and NSS information supported on the link at the time of the initial frame exchange. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information of the link at the time of the initial frame exchange. In another method, STA MLD1 and AP MLD1 can operate according to the spatial flow capabilities of each link. The radio frequency handover request information sent by AP1 101 to STA1 103 can be included in the MAC header of the QoS empty frame in the form of A-control and can be transmitted in the form of an A-MPDU aggregated with the BA frame. The radio frequency handover request information can be auxiliary AP request+ (AAR+) information as extended AAR information.In another approach, the radio frequency switching request information may be information configured in the form of A-control, or it may be included in a frame sent from AP1 101 to STA1 103 in the form of an indication bit, subfield, or information element, or in any other form.

[0090] After AP1 101 of AP MLD1 sends a BA frame 600 containing a radio frequency handover request to STA1 103, AP2 105 can perform a channel access procedure on the second link. The radio frequency handover request is a request for STA MLD1 to receive frame 602 on the second link. The channel access procedure can be an EDCA backoff operation. When the backoff counter reaches zero, AP2 105 of AP MLD1 can perform a channel access procedure (e.g., an EDCA backoff operation) and send downlink frame 602 to STA2 107. Alternatively, even when the backoff counter reaches zero, if no EMLMR delay has elapsed since the end of the transmission of BA frame 600 containing the radio frequency handover request from AP1 101, AP2 105 may not send downlink data frame 602, but instead keep the backoff counter at zero. When the EMLMR delay has elapsed, AP2 105 can send downlink data frame 602 to STA2 107. EMLMR delay is the time required for the STA MLD switching radio chain to perform EMLMR operation. On the first link, AP1 101 and STA1 103 can use two spatial streams to send and receive frames according to the radio switching request indicated by AP1 101. On the second link, AP2 105 and STA2 107 can use two spatial streams to send and receive frames according to the radio switching request indicated by AP1 101.

[0091] refer to Figure 6b When the EMLMR delay time has elapsed after the duration of aSIFSTime + aSlotTime + aRxPHYStartDelay since the end of communication between AP2 105 and STA2 107 on the second link, AP1 101 and STA1 103 on the first link can perform communication operations based on the spatiotemporal flow capabilities of the EMLMR operation exchanged via EML OMN frames on the first link. For example, AP1 101 and STA1 103 can utilize four spatial flows to perform frame transmission and reception operations.

[0092] Figure 7 This is a timing diagram illustrating the ninth embodiment of the EMLMR low-latency transmission method for wireless local area networks.

[0093] refer to Figure 7AP1 101 and STA1 103 can operate on the first link, and AP2 105 and STA2 107 can operate on the second link. AP1 101 and AP2 105 can be APs belonging to AP MLD1. STA1 103 and STA2 107 can be STAs belonging to STA MLD1. That is, the AP and STA operating on the first link of AP MLD1 and STA MLD1 can be AP1 101 and STA1 103 respectively, and the AP and STA operating on the second link of AP MLD1 and STA MLD1 can be AP2 105 and STA2 107 respectively.

[0094] STA MLD1 can be an MLD that supports EMLMR operation. STA MLD1 can perform EMLMR operation on a first link and a second link. That is, the first link and the second link can be referred to as EMLMR links. In EMLMR operation, the STA MLD with multiple radios first receives an initial frame 700 from the AP on each of the multiple links, based on the spatial flow capability of each link via a determined number of spatial flows (NSS), and then switches the receive chain and transmit chain to the link that received the initial frame 700. The receive chain and transmit chain can be referred to as radio chain. After receiving the initial frame 700, the STA MLD can communicate with the AP MLD via the switched radio chain using the NSS set during the EMLMR setup process. To perform EMLMR operation, the STA MLD can send an Enhanced Multi-Link Operation Mode Notification (EML OMN) frame to the AP MLD. The EML OMN frame can include information about the MCS and NSS to be used in the EMLMR operation. The EML OMN frame is an action frame that includes EML control fields. When frame reception is complete, the STA MLD can switch the radio chain to the EMLMR link that did not receive the initial frame 700. Until frame reception is complete, the STAMLD cannot receive data on an EMLMR link where the initial frame 700 has not been received. Until frame transmission is complete, the AP MLD cannot perform transmission on an EMLMR link where the initial frame 700 has not been received. When the STA MLD performs EMLMR operation on an EMLMR link and intends to transmit a frame to the AP MLD, the STA MLD's STA can switch radio chains and transmit the frame to the AP MLD using the MCS and NSS intended for EMLMR operation. When the STA MLD's STA completes frame transmission, the STA MLD can operate on each of multiple links according to the spatial flow capabilities of each link. When the STA MLD's STA transmits a frame to the AP MLD, the AP MLD cannot transmit frames to any STA other than the STA MLD's STA that performed the transmission.

[0095] On the first link, AP1 101 can execute a channel access procedure to send frames to STA1 103. The channel access procedure can be an EDCA backoff procedure. When the EDCA backoff procedure is successful, AP1 101 acquires a TXOP, which is a period of time during which multiple frames can be sent. That is, AP1 101 is the TXOP holder. AP1 101 can send an initial frame 700 to STA1 103. The spatial stream capability per link of STA1 103 can be NSS=2. Accordingly, AP1 101 can use two spatial streams to send frames to STA1 103. STA MLD1 can switch the RF chain to the first link after receiving the initial frame 700 from AP1 101. STA MLD1 can perform transmit and receive operations in EMLMR operations using four spatial streams. In other words, the spatial stream capability exchanged in the EML OMN frame and used for EMLMR operations can be NSS=4. Accordingly, after STA MLD1 switches the RF chain to the first link, STA1 103 can use four spatial streams to transmit or receive frames. AP1 101 can use the four spatial streams to transmit data frames to STA1 103. AP1 101 can continuously transmit downlink frames to STA1 103 at XIFS intervals. XIFS can be shorter than or equal to SIFS. Alternatively, XIFS can be a longer interval than SIFS (e.g., PIFS). During the XIFS between frames transmitted by AP1 101, STA1 103 can transmit frames to AP1 101. STA2 107 cannot perform frame transmission. When STA MLD1 receives data frames on the first link, there may be data that STA MLD1 needs to transmit on the second link. The data to be transmitted on the second link can be data that needs to be transmitted quickly. Accordingly, STA1103 of STA MLD1 can transmit frame 702 on another EMLMR link where reception is not currently being performed. Frame 702 includes a request to send and receive frames during the XIFS period between frames sent to AP1 101. This request may be referred to as EMLMR Fast Transmission Request Information and may be included in the MAC header of a QoS empty frame, BA frame, or other frame sent by STA1 103 to AP1 101 in various forms. The EMLMR Fast Transmission Request Information may include at least one of the following: a link bitmap, trigger frame request information, MCS-NSS information to be used on the indicated link, MCS-NSS information to be used on the current link, and delay limit information. The link bitmap may indicate the links that STA MLD1 intends to use further. For example, STA MLD1 may indicate a second link. The trigger frame request information is information requesting that frame 704 be triggered on the link indicated by STA MLD1 in the link bitmap.For example, since STA MLD1 indicates a second link in the link bitmap, AP2 105 of AP MLD1 can send trigger frame 704 to STA2 107 of STA MLD1 on the second link. The MCS-NSS information to be used on the indicated link indicates the MCS and NSS information supported on the link indicated by STAMLD1 in the link bitmap. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information about the link indicated by STAMLD1 in the link bitmap. The MCS-NSS information to be used on the current link indicates the MCS and NSS information supported on the link that exchanged the initial frame 700. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information about the link that exchanged the initial frame 700. In another approach, STA MLD1 and AP MLD1 can operate based on the spatial flow capabilities of each link. Delay limit information is information indicating when STA MLD1 must send data to AP MLD1. For example, when the STA specifies a delay limit of 1 ms, this indicates that the STA intends to share the TXOP from the TXOP holder within 1 ms. The delay limit information may further include per-AC or per-TID time information. For example, the STA may indicate delay limit information for each AC, such as 1 ms for AC_VO and 5 ms for AC_BE. Alternatively, the STA may indicate delay limit information for each TID, such as 1 ms for TID 1 and 3 ms for TID 3. Indications for delay limit information for each AC and for each TID can be used simultaneously. Based on the delay limit information, AP MLD1 may change the channel access parameters (e.g., EDCA parameters) used to send trigger frame 704 or downlink frame 706 on the link indicated by STA MLD1 in the link bitmap. The EMLMR fast transmission request information sent by STA1 103 to AP1 101 may be included in the MAC header of a QoS empty frame in the form of A-control and may be transmitted in the form of an A-MPDU aggregated with a BA frame. EMLMR fast transmission request information can be an auxiliary AP request+ (AAR+) message as extended AAR information. In another approach, EMLMR fast transmission request information can be information configured in the form of A-control, or it can be included in a frame sent from STA1 103 to AP1101 in the form of indicator bits, subfields, or information elements, or in any other form.

[0096] STA1 103 can send an EMLMR fast transmission request to AP1 101, which may request the transmission of a trigger frame 704 on the second link. After receiving a BA frame 702 including the EMLMR fast transmission request information sent by STA1 103, AP1 101 of AP MLD1 may include an indicator acknowledging the use of the second link in a downlink frame 706. The indicator acknowledging the use of the second link may indicate whether STA2 107 and AP2 105 can communicate on the second link. The indicator acknowledging the use of the second link may be configured in at least one form of an A-control field, a subfield, an indicator bit, and an information element. When the backoff counter reaches zero, AP2 105 of AP MLD1 may perform a channel access procedure (e.g., EDCA backoff operation) and send a trigger frame 704 to STA2 107. The channel access procedure of AP2 105 may be performed faster based on the delay limit information of the EMLMR fast transmission request information sent by STA1 103 to AP1 101. Alternatively, even when the backoff counter reaches zero, if no EMLMR delay has elapsed since the end of the transmission of BA frame 702, which includes the EMLMR fast transmission request from STA1 103, AP2 105 may not send trigger frame 704, but instead keep the backoff counter at zero. When the EMLMR delay has elapsed, AP2 105 may send trigger frame 704 to STA2 107. Since STA2 107 has not detected the channel on the second link for at least a predetermined time, STA2 107 may set a MediumSyncDelay timer on the second link. The length of the MediumSyncDelay timer can be set to PPDUMaxTime, which is the preset maximum length of the PPDU, and STA2 107 needs to perform CCA when the MediumSyncDelay timer operates. CCA is the channel detection operation. When STA2 107 receives trigger frame 704 from AP2 105, it initializes the MediumSyncDelay timer and can perform frame transmission and reception. The trigger frame 704 sent by AP2 105 to STA2 107 can indicate the length of the resource based on the EMLMR fast transmission request information sent by STA1 103 to AP1 101. STA2 107 can send a frame 706 indicating the need for fast transmission to AP2 105. On the first link, AP1 101 and STA1 103 can use two spatial streams to send and receive frames based on the EMLMR fast transmission request indicated by STA1 103. On the second link, AP2 105 and STA2 107 can use two spatial streams to send and receive frame 706 based on the EMLMR fast transmission request indicated by STA1 103.

[0097] When the EMLMR delay time has elapsed after the duration of aSIFSTime + aSlotTime + aRxPHYStartDelay since the end of communication between AP2 105 and STA2 107 on the second link, AP1 101 and STA1 103 on the first link can perform communication operations based on the spatiotemporal flow capabilities of the EMLMR operations exchanged via EML OMN frames on the first link. For example, AP1 101 and STA1 103 can utilize four spatial flows to perform frame transmission and reception operations.

[0098] Figure 8 This is a timing diagram illustrating the tenth embodiment of the EMLMR low-latency transmission method for wireless local area networks.

[0099] refer to Figure 8 AP1 101 and STA1 103 can operate on the first link, and AP2 105 and STA2 107 can operate on the second link. AP1 101 and AP2 105 can be APs belonging to AP MLD1. STA1 103 and STA2 107 can be STAs belonging to STA MLD1. That is, the AP and STA operating on the first link of AP MLD1 and STA MLD1 can be AP1 101 and STA1 103 respectively, and the AP and STA operating on the second link of AP MLD1 and STA MLD1 can be AP2 105 and STA2 107 respectively.

[0100] STA MLD1 can be an MLD that supports EMLMR operation. STA MLD1 can perform EMLMR operation on a first link and a second link. That is, the first link and the second link can be referred to as EMLMR links. In EMLMR operation, the STA MLD with multiple radios first receives an initial frame 800 from the AP on each of the multiple links, based on the spatial flow capability of each link via a determined number of spatial flows (NSS), and then switches the receive chain and transmit chain to the link that received the initial frame 800. The receive chain and transmit chain can be referred to as radio chain. After receiving the initial frame 800, the STA MLD can communicate with the AP MLD via the switched radio chain using the NSS set during the EMLMR setup process. To perform EMLMR operation, the STA MLD can send an Enhanced Multi-Link Operation Mode Notification (EML OMN) frame to the AP MLD. The EML OMN frame can include information about the MCS and NSS to be used in the EMLMR operation. The EML OMN frame is an action frame that includes EML control fields. When frame reception is complete, the STA MLD can switch the radio chain to the EMLMR link that did not receive the initial frame 800. Until frame reception is complete, the STAMLD cannot receive data on an EMLMR link where the initial frame 800 has not been received. Until frame transmission is complete, the AP MLD cannot perform transmission on an EMLMR link where the initial frame 800 has not been received. When the STA MLD performs EMLMR operation on an EMLMR link and intends to send a frame to the AP MLD, the STA MLD's STA can switch radio chains and use the MCS and NSS to be used for EMLMR operation to send a frame to the AP MLD. When the STA MLD's STA completes frame transmission, the STA MLD can operate on each of multiple links according to the spatial flow capabilities of each link. When the STA MLD's STA sends a frame to the AP MLD's AP, the AP MLD cannot send frames to any STA other than the STA MLD's STA that performed the transmission.

[0101] On the first link, AP1 101 can execute a channel access procedure to send frames to STA1 103. The channel access procedure can be an EDCA backoff procedure. When the EDCA backoff procedure is successful, AP1 101 acquires a TXOP, which is a period of time during which multiple frames can be sent. That is, AP1 101 is the TXOP holder. AP1 101 can send an initial frame 800 to STA1 103. The spatial stream capability per link of STA1 103 can be NSS=2. Accordingly, AP1 101 can use two spatial streams to send frames to STA1 103. STA MLD1 can switch the RF chain to the first link after receiving the initial frame 800 from AP1 101. STA MLD1 can perform transmit and receive operations in EMLMR using four spatial streams. In other words, the spatial stream capability exchanged in the EML OMN frame and used for EMLMR operations can be NSS=4. Accordingly, after STA MLD1 switches the RF chain to the first link, STA1 103 can use four spatial streams to transmit or receive frames. AP1 101 can use the four spatial streams to transmit data frames to STA1 103. AP1 101 can continuously transmit downlink frames to STA1 103 at XIFS intervals. XIFS can be shorter than or equal to SIFS. Alternatively, XIFS can be a longer interval than SIFS (e.g., PIFS). During the XIFS between frames transmitted by AP1 101, STA1 103 can transmit frames to AP1 101. STA2 107 cannot perform frame transmission. AP2 105 does not perform frame transmission to STA2 107. When AP MLD1 performs frame transmission on the first link, data may need to be transmitted to STA2 107 on the second link. The data to be transmitted on the second link may be data that needs to be transmitted quickly. Accordingly, AP1 101 of AP MLD1 may indicate a request to receive frames on another EMLMR link that STA1 103 is not currently receiving in a data frame 802 sent to STA1 103. This request may be referred to as radio frequency handover request information. The radio frequency handover request information may include at least one of the following: a link bitmap, MCS-NSS information to be used on the indicated link, and MCS-NSS information to be used on the current link. The link bitmap may indicate the link that AP MLD1 intends to use further. For example, AP MLD1 may indicate a second link. The MCS-NSS information to be used on the indicated link indicates the MCS and NSS information supported by AP MLD1 on the link indicated in the link bitmap. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information regarding the link indicated by AP MLD1 in the link bitmap.The MCS-NSS information to be used on the current link indicates the MCS and NSS information supported on the link in the initial exchange frame 800. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information of the link in the initial exchange frame 800. In another approach, STA MLD1 and AP MLD1 can operate according to the spatial flow capabilities of each link. RF handover request information sent by AP1 101 to STA1 103 can be transmitted in the MAC header of a data frame included in the form of A-control. The RF handover request information can be auxiliary AP Request+ (AAR+) information as extended AAR information. In another approach, the RF handover request information can be information configured in the form of A-control, or it can be included in the frame sent by AP1 101 to STA1 103 in the form of indicator bits, subfields, or information elements, or in any other form.

[0102] After AP1 101 of AP MLD1 sends data frame 802, which includes radio frequency handover request information, to STA1 103, AP2 105 can perform a channel access procedure on the second link. The radio frequency handover request information is a request for STA MLD1 to receive frames on the second link. The channel access procedure can be an EDCA backoff operation. When the backoff counter reaches zero, AP2 105 of AP MLD1 can perform a channel access procedure (e.g., an EDCA backoff operation) and send downlink frame 804 to STA2 107. Alternatively, even when the backoff counter reaches zero, if no EMLMR delay has elapsed since the end of the transmission of data frame 802, which includes the radio frequency handover request information from AP1 101, AP2 105 may not send downlink data frame 804, but instead keep the backoff counter at zero. When the EMLMR delay has elapsed, AP2 105 can send downlink data frame 804 to STA2 107. EMLMR delay is the time required for the STA MLD switching radio chain to perform EMLMR operation. On the first link, AP1 101 and STA1 103 can use two spatial streams to send and receive frames according to the radio switching request indicated by AP1 101. On the second link, AP2 105 and STA2 107 can use two spatial streams to send and receive frames according to the radio switching request indicated by AP1 101.

[0103] When the EMLMR delay time has elapsed after the duration of aSIFSTime + aSlotTime + aRxPHYStartDelay since the end of communication between AP2 105 and STA2 107 on the second link, AP1 101 and STA1 103 on the first link can perform communication operations based on the spatiotemporal flow capabilities of the EMLMR operations exchanged via EML OMN frames on the first link. For example, AP1 101 and STA1 103 can utilize four spatial flows to perform frame transmission and reception operations.

[0104] Figure 9 This is a timing diagram illustrating the eleventh embodiment of the EMLMR low-latency transmission method for wireless local area networks.

[0105] refer to Figure 9 AP1 101 and STA1 103 can operate on the first link, and AP2 105 and STA2 107 can operate on the second link. AP1 101 and AP2 105 can be APs belonging to AP MLD1. STA1 103 and STA2 107 can be STAs belonging to STA MLD1. That is, the AP and STA operating on the first link of AP MLD1 and STA MLD1 can be AP1 101 and STA1 103 respectively, and the AP and STA operating on the second link of AP MLD1 and STA MLD1 can be AP2 105 and STA2 107 respectively.

[0106] STA MLD1 can be an MLD that supports EMLMR operation. STA MLD1 can perform EMLMR operation on a first link and a second link. That is, the first link and the second link can be referred to as EMLMR links. In EMLMR operation, the STA MLD with multiple radios first receives an initial frame from the AP on each of the multiple links, based on the spatial flow capability of each link via a determined number of spatial flows (NSS), and then switches the receive chain and transmit chain to the link that received the initial frame. The receive chain and transmit chain can be referred to as radio chain. After receiving the initial frame, the STA MLD can communicate with the AP MLD via the switched radio chain using the NSS set during the EMLMR setup process. To perform EMLMR operation, the STA MLD can send an Enhanced Multi-Link Operation Mode Notification (EML OMN) frame to the AP MLD. The EML OMN frame can include information about the MCS and NSS to be used in the EMLMR operation. The EML OMN frame is an action frame that includes EML control fields. When frame reception is complete, the STA MLD can switch the radio chain to the EMLMR link that did not receive the initial frame. Until frame reception is complete, the STA MLD cannot receive data on an EMLMR link where the initial frame has not been received. Until frame transmission is complete, the AP MLD cannot perform transmission on an EMLMR link where the initial frame has not been received. When the STA MLD performs EMLMR operation on an EMLMR link and intends to transmit a frame to the AP MLD, the STA MLD's STA can switch radio chains and transmit the frame to the AP MLD using the MCS and NSS to be used for EMLMR operation. When the STA MLD's STA completes frame transmission, the STA MLD can operate on each of multiple links according to the spatial flow capabilities of each link. When the STA MLD's STA transmits a frame to the AP MLD's AP, the AP MLD cannot transmit frames to any STA other than the STA that performed the transmission.

[0107] On the first link, STA1 103 can execute a channel access procedure to send frames to AP1 101. The channel access procedure can be an EDCA backoff procedure. When the EDCA backoff procedure is successful, STA1 103 acquires a TXOP, which is a time period during which multiple frames can be sent. That is, STA1 103 is the TXOP holder. STA1 103 can send frames to AP1 101. STA MLD1 can utilize four spatial streams to perform transmit or receive operations in EMLMR. In other words, the spatial stream capacity exchanged in EML OMN frames and used for EMLMR operations can be NSS=4. Accordingly, STA1 103 can use four spatial streams to send frames to AP1 101. AP1 101 can use four spatial streams to send data frames to STA1 103. STA1 103 can continuously send downlink frames to AP1 101 at XIFS intervals. XIFS can be shorter than or equal to SIFS. Alternatively, XIFS can be a longer interval than SIFS (e.g., PIFS). During the XIFS between frames transmitted by STA1 103, AP1 101 can transmit frames to STA1 103. STA2 107 cannot perform frame transmission. AP2 105 does not perform frame transmission to STA2 107. When AP MLD1 performs frame reception on the first link, data may need to be transmitted to STA2 107 on the second link. The data to be transmitted on the second link may be data that needs to be transmitted quickly. Accordingly, AP1 101 of AP MLD1 may indicate a request to receive frames on another EMLMR link that STA1 103 is not currently transmitting or receiving on in frame 900 sent to STA1 103. This request may be referred to as RF handover request information. RF handover request information may include at least one of the following: a link bitmap, MCS-NSS information to be used on the indicated link, and MCS-NSS information to be used on the current link. The link bitmap may indicate the link that AP MLD1 intends to use further. For example, AP MLD1 can indicate a second link. The MCS-NSS information to be used on the indicated link indicates the MCS and NSS information supported on the link indicated by AP MLD1 in the link bitmap. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information about the link indicated by AP MLD1 in the link bitmap. The MCS-NSS information to be used on the current link indicates the MCS and NSS information supported on the link exchanging the initial frame. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information about the link exchanging the initial frame. In another approach, STA MLD1 and AP MLD1 can operate based on the spatial flow capabilities of each link.The radio frequency handover request information sent by AP1101 to STA1103 can be included in the MAC header of a QoS empty frame in the form of A-control, and can be transmitted in the form of an A-MPDU aggregated with a BA frame. The radio frequency handover request information can be auxiliary AP Request+ (AAR+) information as extended AAR information. In another approach, the radio frequency handover request information can be information configured in the form of A-control, or it can be included in the frame sent by AP1101 to STA1103 in the form of indicator bits, subfields, or information elements, or in any other form.

[0108] After AP1 101 of AP MLD1 sends frame 900, which includes radio frequency handover request information, to STA1 103 during the XIFS period between frames transmitted by STA1 103, AP2 105 can perform a channel access procedure on the second link. The radio frequency handover request information is information requesting STA MLD1 to receive frames on the second link. The channel access procedure can be an EDCA backoff operation. When the backoff counter reaches zero, AP2 105 of AP MLD1 can perform a channel access procedure (e.g., an EDCA backoff operation) and send downlink frame 902 to STA2 107. Even when the backoff counter reaches zero, if no EMLMR delay has elapsed since the end of the transmission of frame 900, which includes the radio frequency handover request information from AP1 101, AP2 105 may not send downlink data frame 902, but instead keep the backoff counter at zero. When the EMLMR delay has elapsed, AP2 105 can send downlink data frame 902 to STA2 107. EMLMR delay is the time required for the STA MLD switching radio chain to perform EMLMR operation. On the first link, AP1 101 and STA1 103 can use two spatial streams to send and receive frames according to the radio switching request indicated by AP1 101. On the second link, AP2 105 and STA2 107 can use two spatial streams to send and receive frames according to the radio switching request indicated by AP1 101.

[0109] When the EMLMR delay time has elapsed after the duration of aSIFSTime + aSlotTime + aRxPHYStartDelay since the end of communication between AP2 105 and STA2 107 on the second link, AP1 101 and STA1 103 on the first link can perform communication operations based on the spatiotemporal flow capabilities of the EMLMR operations exchanged via EML OMN frames on the first link. For example, AP1 101 and STA1 103 can utilize four spatial flows to perform frame transmission and reception operations.

[0110] Figure 10a and Figure 10b This is a timing diagram illustrating the twelfth and thirteenth implementation schemes of the EMLMR low-latency transmission method for wireless local area networks.

[0111] refer to Figure 10a and Figure 10b AP1 101 and STA1 103 can operate on the first link, and AP2 105 and STA2 107 can operate on the second link. AP1 101 and AP2 105 can be APs belonging to AP MLD1. STA1 103 and STA2 107 can be STAs belonging to STA MLD1. That is, the AP and STA operating on the first link of AP MLD1 and STA MLD1 can be AP1 101 and STA1 103 respectively, and the AP and STA operating on the second link of AP MLD1 and STA MLD1 can be AP2 105 and STA2 107 respectively.

[0112] STA MLD1 can be an MLD that supports EMLMR operation. STA MLD1 can perform EMLMR operation on a first link and a second link. That is, the first link and the second link can be referred to as EMLMR links. In EMLMR operation, the STA MLD with multiple radio frequencies first receives an initial frame 1000 from the AP on each of the multiple links, based on the spatial flow capability of each link via a determined number of spatial flows (NSS), and then switches the receive chain and transmit chain to the link that received the initial frame 1000. The receive chain and transmit chain can be referred to as radio frequency chains. After receiving the initial frame 1000, the STA MLD can communicate with the AP MLD via the switched radio frequency chain using the NSS set during the EMLMR setup process. To perform EMLMR operation, the STA MLD can send an Enhanced Multi-Link Operation Mode Notification (EML OMN) frame to the AP MLD. The EML OMN frame can include information about the MCS and NSS to be used in the EMLMR operation. The EML OMN frame is an action frame that includes EML control fields. When frame reception is complete, the STA MLD can switch the RF chain to an EMLMR link that did not receive the initial frame 1000. Until frame reception is complete, the STA MLD cannot receive data on an EMLMR link that did not receive the initial frame 1000. Until frame transmission is complete, the AP MLD cannot perform transmission on an EMLMR link that did not receive the initial frame 1000. When the STA MLD performs EMLMR operation on an EMLMR link and intends to transmit a frame to the AP MLD, the STA MLD's STA can switch the RF chain and transmit the frame to the AP MLD's AP using the MCS and NSS to be used for EMLMR operation. When the STA MLD's STA completes frame transmission, the STA MLD can operate on each of multiple links according to the spatial flow capabilities of each link. When the STA MLD's STA transmits a frame to the AP MLD's AP, the AP MLD cannot transmit frames to any STA other than the STA MLD's STA that performed the transmission.

[0113] On the first link, AP1 101 can execute a channel access procedure to send frames to STA1 103. The channel access procedure can be an EDCA backoff procedure. When the EDCA backoff procedure is successful, AP1 101 acquires a TXOP, which is a period of time during which multiple frames can be sent. That is, AP1 101 is the TXOP holder. AP1 101 can send an initial frame 1000 to STA1 103. The per-link spatial stream capability of STA1 103 can be NSS=2. Accordingly, AP1 101 can use two spatial streams to send frames to STA1 103. STA1 103 can respond to AP1 101's frames using a Block Acknowledgment (BA) frame. STA MLD1 can switch the RF chain to the first link after receiving the initial frame 1000 from AP1 101. STA MLD1 can perform transmission and reception in EMLMR operations through four spatial streams. In other words, the spatial stream capability exchanged in the EML OMN frame and used for EMLMR operation can be NSS=4. Accordingly, after STA MLD1 switches the RF chain to the first link, STA1 103 can use four spatial streams to send or receive frames. AP1 101 can use four spatial streams to send data frames to STA1 103. STA2 107 cannot perform frame transmission. When STA MLD1 receives data frames on the first link, there may be data that STA MLD1 wants to transmit on the second link. The data to be transmitted on the second link may not be data to be transmitted to the AP, but may be data to be transmitted via direct communication (e.g., P2P communication). The data to be transmitted via P2P communication is not data to be sent to the AP MLD, but data to be sent to another WLAN terminal. Alternatively, the data to be transmitted on the second link may not be transmitted via WLAN communication. That is, the data to be transmitted on the second link may be data transmitted using a non-802.11 protocol. Accordingly, STA1 103 of STA MLD1 may indicate a request to send and receive frames on another EMLMR link that STA MLD1 is not currently receiving on in a BA frame 1002 sent to AP1 101. This request may be referred to as EMLMR fast transmission request information. EMLMR fast transmission request information may be auxiliary AP request+ (AAR+) information as extended AAR information. In another approach, EMLMR fast transmission request information may be information configured in the form of A-control, or may be included in a frame sent by STA1 103 to AP1 101 in the form of indicator bits, subfields, or information elements, or in any other form. EMLMR fast transmission request information may include at least one of the following: link bitmap, MCS-NSS information to be used on the current link, trigger frame request information, communication duration, and communication start and finish information.The link bitmap can indicate the links that STA MLD1 intends to use further. For example, STA MLD1 can indicate a second link. Since STA MLD1 indicates a second link in the link bitmap, STA MLD1 indicates that P2P communication or non-802.11 communication will be performed on the second link. The MCS-NSS information to be used on the current link indicates the MCS and NSS information supported on the link in the initial frame 1000 of the exchange. STA MLD1 and AP MLD1 perform communication based on the MCS-NSS information of the link in the initial frame 1000 of the exchange. In another method, STA MLD1 and AP MLD1 can operate based on the spatial flow capabilities of each link. The communication duration indicates the duration of communication performed on the link indicated by STA MLD in the link bitmap, and the communication start and finish information can indicate whether STA MLD performed communication on the link indicated by STA MLD in the bitmap.

[0114] STA MLD1 and AP MLD1 can perform communication on the first link using fewer spatial flows (e.g., 2SS) than when setting up EMLMR. STA MLD1 can communicate with another STA or perform non-802.11 communication 1004 on the second link. AP MLD2 does not perform communication during the communication duration indicated by STA MLD1. In another approach, the period during which STA MLD1 performs communication on the second link can be uncertain. Accordingly, STA MLD1 can instead of indicating a specific communication duration, sending an EMLMR fast transmission request message to AP MLD1 at the start and end of each communication, thereby indicating the period during which AP MLD1 is not allowed to perform transmissions to STA MLD1 on the second link. The start and end of communication can be indicated by communication start and end information present in the EMLMR fast transmission request message.

[0115] refer to Figure 10b When the communication duration of the second link indicated by STA MLD1 expires, AP MLD1 and STAMLD1 can perform communication on the first link using the spatial streams (e.g., 4SS) set when EMLMR is set up. In another method, when STA MLD1 indicates the start of communication on the second link of AP MLD1 via communication start and finish information present in the EMLMR fast transmission request information, it can perform communication using a smaller number of spatial streams (e.g., 2SS) than the number set when EMLMR is set up. When STA MLD1 indicates the end of communication on the second link of AP MLD1 via communication start and finish information present in the EMLMR fast transmission request information, it can perform communication using the number of spatial streams (e.g., 4SS) set when EMLMR is set up.

[0116] exist Figure 10a and Figure 10b In the context of EMLMR, when STA MLD1 sends a trigger frame request message to AP MLD1 indicating a trigger frame on the second link, AP MLD1 can perform a TXOP sharing operation on the second link. The TXOP sharing operation can be a triggered TXOP sharing operation and can be performed via AP MLD1's MU-RTS TXS (TXOP sharing) frame. The MU-RTS TXS frame can include STA MLD1's AID, and the TXS mode can be indicated as 2 or 1. STA MLD1 can respond to the MU-RTS TXS frame via a CTS frame on the second link. When the TXS mode is indicated as 2, STA MLD1 can perform P2P communication or communicate with the AP on the second link within the time indicated by the MU-RTS TXS frame. When the TXS mode is indicated as 1, STA MLD1 can communicate with the AP within the time indicated by the MU-RTS TXS frame on the second link.

[0117] Figure 11 A flowchart illustrating a method for operating a STA according to an embodiment of the present invention is shown. For example, the STA may be an MLD. In other words, the STA may utilize multiple links, including a first link and a second link, to transmit or receive frames. Here, frames may include control frames (e.g., BA frames), initial frames, and data frames (e.g., PPDU, MPDU, or A-MPDU). Figure 11 This illustrates the operation of the STA transmitting data frames (e.g., low-latency data) on the second link.

[0118] refer to Figure 11 In step S1101, the STA receives the initial frame (e.g., Figure 3a The initial frame (300) can be received using the first link. The initial frame may include at least one of the following: information for switching the radio chain, information for initiating EMLMR operation, and information for configuring EMLMR. The initial frame is transmitted by the AP and may be a frame indicating the start of EMLMR operation. The initial frame can be sent and received using a predefined NSS.

[0119] In step S1103, the STA sends a frame including first information to the AP. The first information may be information associated with EMLMR operation. For example, the first information may be information including at least one of the MCS and NSS used for EMLMR operation. The frame including the first information may be, for example, an EML OMN frame.

[0120] In step S1105, the STA switches the radio frequency chain based on the initial frame and the first information. In other words, the STA performs EMLMR operation based on the initial frame and the first information. The radio frequency chain includes a first chain and a second chain. Before performing EMLMR operation, the STA can use the first chain to perform communication on the first link. The STA can use the second chain to perform communication on the second link. In order to perform transmission and reception on the first link, the STA can switch the radio frequency chain from the second link to the first link. For example, the STA can switch the second chain from the second link to the first link. Here, the first link can be a link that has received the initial frame. The second link can be a link that has not received the initial frame. In other words, the NSS of a link that has not received the initial frame (e.g., the second link) can be used on a link that has received the initial frame (e.g., the first link). For example, when each link has two spatial streams, the STA can use four spatial streams to perform transmission and reception on the first link.

[0121] After switching RF chains, the STA can utilize the first link to perform operations with the AP (e.g., Figure 3a Communication with AP1 (101). In other words, the STA can send frames to the AP and receive frames from the AP using the first link.

[0122] In step S1107, the STA can transmit second information. The second information may be information indicating the existence of data to be transmitted using the second link. In other words, the second information may be information indicating the existence of data to be transmitted on a link where EMLMR operation is not performed. For example, the data to be transmitted using the second link may be time-sensitive data. Time-sensitive data can be transmitted using data frames. The second information can be transmitted using the first link. For example, data frames transmitted on the first link (e.g., Figure 3a The BA frame 304 may include second information. The second information may include information for transmitting data frames on the second link.

[0123] The second information may include at least one of the following: a link bitmap, trigger frame request information, MCS information for the indicated link, NSS information for the indicated link, MCS information for the current link, NSS information for the current link, and delay limit information. The link bitmap indicates the link to which a data frame is to be transmitted. In other words, the link bitmap indicates a link that has not received an initial frame. According to an embodiment of the invention, the link bitmap may indicate a second link. The trigger frame request information requests a trigger frame (e.g., on the link indicated by the link bitmap) on the link indicated by the link bitmap. Figure 3aThe information in the trigger frame 306. The indicated link is the link indicated by the link bitmap. The current link is the link performing the EMLMR operation. In other words, the current link is the link that received the initial frame (e.g., the first link). Delay limit information is information associated with the time of transmitting data or frames. Delay limit information can be information used to change channel access parameters.

[0124] The second information can be represented in various forms. For example, the second information can be in the form of A-control and can be included in the MAC header of a QoS empty frame. As another example, the second information can be in the form of AAR+ extended AAR information. As yet another example, the second information can be represented as an indicator bit, a subfield, and an information element.

[0125] In step S1109, the STA can switch the RF chain to the second link based on the second information. For example, the STA can switch the second chain to the second link based on the second information. The STA can receive information indicating the use of the second link on the first link (e.g., an indicator confirming the use of the second link). The information indicating the use of the second link can be included in a control frame or a data frame (e.g., Figure 4a The information in data frame 408. For example, the STA can switch the radio link from the first link to the second link based on at least one of the second information and information indicating the use of the second link. As another example, the STA can send the second information to the AP and then switch the radio link to the second link.

[0126] In step S1111, the STA can receive a trigger frame. The STA can switch RF chains and then receive a trigger frame. The STA can also use a second link to receive a trigger frame.

[0127] The trigger frame may be a frame that includes information indicating the size of the resources used to send the data frame. Here, the size of the resources may be a value determined based on the second information. For example, the trigger frame request information included in the second information may include information about the size of the resources required to send the data frame.

[0128] The STA can set the MediumSyncDelay time before receiving the trigger frame on the second link. The STA can initialize the MediumSyncDelay time after receiving the trigger frame on the second link. The STA can receive the trigger frame and then send and receive frames on the second link.

[0129] In step S1113, the STA can send a data frame to the AP using the second link. For example, the STA can use the NSS of the second link to send the data frame. As another example, the STA can send the data frame based on second information. For example, the STA can send the data frame based on at least one of the MCS information and the NSS information of the indicated link. As yet another example, the STA can send the data frame based on a trigger frame. The STA can send the data frame based on the size of the resource included in the trigger frame. In other words, the STA can send the data frame based on at least one of the second information and the trigger frame.

[0130] Data frames can be included in uplink frames (e.g., Figure 3a It is transmitted in the uplink frame 310. The STA can send data frames and then receive BA from the AP.

[0131] The STA can transmit data frames and then use the second link's RF chain on the first link to transmit and receive frames. In other words, the STA can perform EMLMR operations on the first link. That is, the STA can switch RF chains. On the other hand, the STA can choose not to perform EMLMR operations on the first link after transmitting data frames.

[0132] Figure 12 A flowchart illustrating a method for operating an AP according to an embodiment of the present invention is shown. For example, the AP may be an MLD. In other words, the AP may utilize multiple links, including a first link and a second link, to send or receive frames. Here, frames may include control frames (e.g., BA frames), initiation frames, and data frames (e.g., PPDU, MPDU, or A-MPDU). Figure 12 The operation of an AP receiving data frames (e.g., low-latency data) is illustrated.

[0133] refer to Figure 12 In step S1201, the AP sends an initial frame to the STA (e.g., Figure 3a The initial frame (300) can be received using the first link. The initial frame may include at least one of the following: information for switching the radio frequency chain, information for initiating EMLMR operation, and information for configuring EMLMR. The initial frame may be a frame indicating the start of EMLMR operation. The initial frame can be received using a predefined NSS.

[0134] In step S1203, the AP receives a frame including first information from the STA. The first information may be information associated with EMLMR operation. For example, the first information may be information including at least one of the MCS and NSS used for EMLMR operation. The frame including the first information may be, for example, an EML OMN frame.

[0135] In step S1205, the AP can receive second information from the STA. The second information may be information indicating the existence of data to be transmitted using the second link. In other words, the second information may be information indicating the existence of data to be transmitted on a link where EMLMR operation is not performed. For example, the data to be transmitted using the second link may be time-sensitive data. Time-sensitive data can be transmitted using data frames. The second information may be information sent from the STA. For example, the AP may receive a control frame including the second information (e.g., Figure 3a (BA frame 304). As another example, the AP may receive a data frame that includes second information (e.g., PPDU, MPDU, or A-MPDU). The second information may include information for transmitting data frames on the second link.

[0136] The second information may include at least one of the following: a link bitmap, trigger frame request information, MCS information for the indicated link, NSS information for the indicated link, MCS information for the current link, NSS information for the current link, and delay limit information. The link bitmap indicates the link to which a data frame is to be transmitted. In other words, the link bitmap indicates a link that has not received an initial frame. According to an embodiment of the invention, the link bitmap may indicate a second link. The trigger frame request information requests a trigger frame (e.g., on the link indicated by the link bitmap) on the link indicated by the link bitmap. Figure 3a The information in the trigger frame 306. The indicated link is the link indicated by the link bitmap. The current link is the link performing the EMLMR operation. In other words, the current link is the link that received the initial frame (e.g., the first link). Delay limit information is information associated with the time of transmitting data or frames. Delay limit information can be information used to change channel access parameters.

[0137] The second information can be represented in various forms. For example, the second information can be in the form of A-control and can be included in the MAC header of a QoS empty frame. As another example, the second information can be in the form of AAR+ extended AAR information. As yet another example, the second information can be represented as an indicator bit, a subfield, and an information element.

[0138] In step S1207, the AP may send at least one of a trigger frame and information indicating the use of the second link to the STA. The AP may send the trigger frame after receiving the second information. The AP may send the information indicating the use of the second link (e.g., an indicator confirming the use of the second link) after sending the trigger frame or before sending the trigger frame. The AP may use the second link to send the trigger frame. The AP may use the first link to transmit the information indicating the use of the second link. The information indicating the use of the second link may be included in a control frame or a data frame (e.g., Figure 4aInformation in data frame 408. Information indicating the use of the second link may be included in a different frame than the trigger frame.

[0139] The trigger frame may be a frame that includes information indicating the size of the resources used to send the data frame. Here, the size of the resources may be a value determined based on the second information. For example, the trigger frame request information included in the second information may include information about the size of the resources required to send the data frame.

[0140] The AP can perform a backoff operation. For example, the AP can send a data frame to the STA when the backoff counter reaches zero. As another example, the AP can send a trigger frame to the STA when the backoff counter reaches zero and a predefined time (e.g., EMLMR delay) has elapsed since the end of transmission of the frame including the second information. The backoff operation can be performed before the AP sends the trigger frame. The backoff operation can also begin after information indicating the use of the second link has been transmitted.

[0141] In step S1209, the AP can receive data frames from the STA using the second link. For example, the AP can use the NSS of the second link to receive data frames. As another example, the AP can receive data frames based on second information. For example, the AP can receive data frames based on at least one of the MCS information for the indicated link and the NSS information for the indicated link. For example, the data frame can be included in the uplink frame (e.g., Figure 3a The data is received in the uplink frame 310. The AP can receive the data frame and then send a BA to the STA.

[0142] The access point (AP) can receive data frames and then use the radio frequency chain of the second link on the first link to send and receive frames. In other words, the AP can perform EMLMR operation on the first link. Alternatively, the AP can choose not to perform EMLMR operation on the first link after sending data frames.

[0143] Figure 13 A flowchart illustrating a method for operating an AP according to an embodiment of the present invention is shown. For example, the AP may be an MLD. In other words, the AP may utilize multiple links, including a first link and a second link, to send or receive frames. Here, frames may include control frames (e.g., BA frames), initiation frames, and data frames (e.g., PPDU, MPDU, or A-MPDU). Figure 13 The diagram illustrates the operation of an AP sending data frames (e.g., low-latency data).

[0144] refer to Figure 13 In step S1301, the AP sends an initial frame to the STA (e.g., Figure 5aThe initial frame (500) can be transmitted using the first link. The initial frame may include at least one of the following: information for switching the radio frequency chain, information for initiating EMLMR operation, and information for configuring EMLMR. The initial frame may be a frame indicating the start of EMLMR operation. The initial frame can be sent and received using a predefined NSS.

[0145] In step S1303, the AP receives a frame including first information from the STA. The first information may be information associated with EMLMR operation. For example, the first information may be information including at least one of the MCS and NSS used for EMLMR operation. The frame including the first information may be, for example, an EML OMN frame.

[0146] In step S1305, the AP may send second information to the STA. The second information may be information indicating the existence of data to be transmitted using the second link. In other words, the second information may be information indicating the existence of data to be transmitted on a link where EMLMR operation is not performed. For example, the data to be transmitted using the second link may be time-sensitive data. Time-sensitive data can be transmitted using data frames. The second information can be included in control frames or data frames (e.g., Figure 5a The data is transmitted in a frame (502). For example, the AP may send a control frame (e.g., a BA frame) that includes second information. As another example, the AP may send a data frame (e.g., a PPDU, MPDU, or A-MPDU) that includes second information. The second information may include information for sending data frames on the second link.

[0147] The second information may include at least one of a link bitmap, trigger frame request information, MCS information for the indicated link, NSS information for the indicated link, MCS information for the current link, NSS information for the current link, and delay limit information. The link bitmap indicates the link to which a data frame is to be transmitted. In other words, the link bitmap indicates a link that has not received an initial frame. According to an embodiment of the invention, the link bitmap may indicate a second link. The trigger frame request information is information requesting a trigger frame on the link indicated by the link bitmap. The indicated link is the link indicated by the link bitmap. The current link is the link performing EMLMR operation. In other words, the current link is the link that received the initial frame (e.g., the first link). The delay limit information is information associated with the time of transmitting data or frames. The delay limit information may be information used to change channel access parameters.

[0148] The second information can be represented in various forms. For example, the second information can be in the form of A-control and can be included in the MAC header of the data frame. As another example, the second information can be in the form of AAR+ extended AAR information. As yet another example, the second information can be represented as an indicator bit, a subfield, and a information element.

[0149] According to an embodiment of the present invention, after sending the second information, the AP can utilize the first link to receive information approving the use of the second link. The information approving the use of the second link may be included in a control frame (e.g., Figure 5a The information in the BA frame (504) or data frame. The information approving the use of the second link can be information sent in response to the second information. In other words, the information approving the use of the second link can be information sent by the STA in response to the second information. On the other hand, the AP can receive information denying the use of the second link. When the AP receives information denying the use of the second link, step S1307 is not executed.

[0150] In step S1307, the AP can send a data frame to the STA using the second link. For example, the AP can use the NSS of the second link to send the data frame. As another example, the AP can send the data frame based on second information. For example, the AP can send the data frame based on at least one of the MCS information for the indicated link and the NSS information for the indicated link. For example, the data frame can be included in the downlink frame (e.g., Figure 5a It is transmitted in downlink frame 506. The AP can send data frames and then receive BA from the STA.

[0151] An AP can perform a backoff operation to send a data frame. For example, the AP can send a data frame to the STA when the backoff counter reaches zero. As another example, the AP can send a data frame to the STA when the backoff counter reaches zero and a predefined time (e.g., an EMLMR delay) has elapsed since the end time of transmission of the data frame including second information. The backoff operation can be performed before the AP sends the data frame.

[0152] The access point (AP) can send data frames and then use the radio frequency chain of the second link on the first link to send and receive frames. In other words, the AP can perform EMLMR operation on the first link. Alternatively, the AP can choose not to perform EMLMR operation on the first link after sending data frames.

[0153] Figure 14A flowchart illustrating a method for operating a STA according to an embodiment of the present invention is shown. For example, the STA may be an MLD. In other words, the STA may utilize multiple links, including a first link and a second link, to transmit or receive frames. Here, frames may include control frames (e.g., BA frames), initial frames, and data frames (e.g., PPDU, MPDU, or A-MPDU). Figure 14 The operation of a STA receiving data frames (e.g., low-latency data) is illustrated.

[0154] refer to Figure 14 In step S1401, the STA receives an initial frame from the AP (e.g., Figure 5a The initial frame (500) can be transmitted using the first link. The initial frame may include at least one of the following: information for switching the radio frequency chain, information for initiating EMLMR operation, and information for configuring EMLMR. The initial frame may be a frame indicating the start of EMLMR operation. The initial frame can be received using a predefined NSS.

[0155] In step S1403, the STA receives a frame including first information from the AP. The first information may be information associated with EMLMR operation. For example, the first information may be information including at least one of the MCS and NSS used for EMLMR operation. The frame including the first information may be, for example, an EML OMN frame.

[0156] In step S1405, the STA switches the radio frequency chain based on the initial frame and the first information. In other words, the STA performs EMLMR operation based on the initial frame and the first information. The radio frequency chain includes a first chain and a second chain. Before performing EMLMR operation, the STA can use the first chain to perform communication on the first link. The STA can use the second chain to perform communication on the second link. In order to perform transmission and reception on the first link, the STA can switch the radio frequency chain from the second link to the first link. For example, the STA can switch the second chain from the second link to the first link. Here, the first link can be a link that has received the initial frame. The second link can be a link that has not received the initial frame. In other words, the NSS of a link that has not received the initial frame (e.g., the second link) can be used on a link that has received the initial frame (e.g., the first link). For example, when each link has two spatial streams, the STA can use four spatial streams to perform transmission and reception on the first link.

[0157] In step S1407, the STA can receive second information from the AP. The second information may be information indicating the existence of data to be transmitted using the second link. In other words, the second information may be information indicating the existence of data to be transmitted on a link where EMLMR operation is not performed. For example, the data to be transmitted using the second link may be time-sensitive data. Time-sensitive data can be transmitted using data frames. The second information can be included in control frames or data frames (e.g., Figure 5a The data is transmitted in a data frame (502). For example, the STA can receive a control frame (e.g., a BA frame) that includes second information. As another example, the STA can receive a data frame (e.g., a PPDU, MPDU, or A-MPDU) that includes second information. The second information may include information for transmitting data frames on the second link.

[0158] The second information may include at least one of a link bitmap, trigger frame request information, MCS information for the indicated link, NSS information for the indicated link, MCS information for the current link, NSS information for the current link, and delay limit information. The link bitmap indicates the link to which a data frame is to be transmitted. In other words, the link bitmap indicates a link that has not received an initial frame. According to an embodiment of the invention, the link bitmap may indicate a second link. The trigger frame request information is information requesting a trigger frame on the link indicated by the link bitmap. The indicated link is the link indicated by the link bitmap. The current link is the link performing EMLMR operation. In other words, the current link is the link that received the initial frame (e.g., the first link). The delay limit information is information associated with the time of transmitting data or frames. The delay limit information may be information used to change channel access parameters. The information included in the second information may represent conditions for transmitting data frames using the second link. For example, when the NSS included in the NSS information for the indicated link is unavailable, data frames may not be transmitted using the second link.

[0159] The second information can be represented in various forms. For example, the second information can be in the form of A-control and can be included in the MAC header of the data frame. As another example, the second information can be in the form of AAR+ extended AAR information. As yet another example, the second information can be represented as an indicator bit, a subfield, and a information element.

[0160] According to an embodiment of the present invention, after receiving the second information, the STA can use the first link to send information approving the use of the second link. The information approving the use of the second link may be included in a control frame (e.g., Figure 5aThe information in the BA frame 504 or data frame. The information approving the use of the second link can be sent as a response to the second information. In other words, the information approving the use of the second link can be sent by the STA in response to the second information. On the other hand, the STA can send information rejecting the use of the second link. For example, when the conditions for using the second link to send data frames are not met, the STA can send information rejecting the use of the second link. When the STA sends information rejecting the use of the second link, step S1409 is not executed.

[0161] In step S1409, the STA can switch the RF chain to the second link based on the second information. For example, the STA can switch the RF chain from the first link to the second link based on at least one of the second information and information approving the use of the second link. As another example, the STA can receive the second information from the AP and then switch the RF chain to the second link. For example, the STA can switch the second link to the second link.

[0162] In step S1411, the STA can receive data frames from the AP using the second link. For example, the STA can use the NSS of the second link to receive data frames. As another example, the STA can receive data frames based on second information. For example, the STA can receive data frames based on at least one of the MCS information for the indicated link and the NSS information for the indicated link. For example, the data frame can be included in the downlink frame (e.g., Figure 5a The STA receives the data frame from the downlink frame 506. The STA can receive the data frame and then send the BA to the AP.

[0163] The STA can receive data frames and then use the RF chain of the second link on the first link to transmit and receive frames. In other words, the STA can switch RF chains to perform EMLMR operation on the first link. Alternatively, the STA can choose not to perform EMLMR operation on the first link after transmitting data frames.

[0164] The operation of the method according to an exemplary embodiment of the present invention can be implemented as a computer-readable program or code in a computer-readable recording medium. The computer-readable recording medium may include all types of recording means for storing data that can be read by a computer system. Furthermore, the computer-readable recording medium can store and execute programs or code that can be distributed across computer systems connected via a network and read in a distributed manner by a computer.

[0165] Additionally, computer-readable recording media may include hardware devices specifically configured to store and execute program commands, such as ROM, RAM, or flash memory. Program commands may include not only machine language code created by a compiler but also high-level language code that can be executed by a computer using an interpreter.

[0166] Although the invention has been described with reference to preferred embodiments thereof, those skilled in the art will understand that various modifications and alterations may be made to the invention without departing from the scope and spirit of the invention as defined by the appended claims.

[0167] Industrial availability This disclosure can be used in devices and recording media in wireless local area network systems.

Claims

1. A method performed by a station (STA) in a wireless local area network system, the method comprising: At least one of sending and receiving is performed on the first link using the first link; At least one of sending and receiving is performed on the second link; Receive an initial frame on the first link to initiate Enhanced Multi-Link Multi-Radio (EMLMR) operation; Based on the initial frame, switch the second link from the second link to the first link; Information for data frame transmission is sent on the second link; Based on the information, switch the second link from the first link to the second link; Receive trigger frames on the second link; as well as Based on the information and at least one of the trigger frames, a data frame is transmitted on the second link.

2. The method according to claim 1, wherein, The information includes information about the modulation and coding scheme (MCS) and number of spatial streams (NSS) used for the second link, as well as information about the request trigger frame.

3. The method according to claim 1, wherein, Switching the second chain from the first chain includes: Receive information indicating the use of the second link as a response to the information; and The second link is switched based on the aforementioned information and information indicating the use of the second link.

4. The method according to claim 3, wherein, Based on the fact that the second link is busy, the information indicating the use of the second link includes information to refuse the use of the second link, and not to switch the second link.

5. The method according to claim 3, wherein, The information includes conditions for sending data frames using the second link, and Wherein, if the condition is not met, the information indicating the use of the second link includes information to refuse the use of the second link and not to switch the second link.

6. The method according to claim 3, wherein, The information indicating the use of the second link is provided by the PHY preamble.

7. The method according to claim 6, wherein, The PHY preamble includes information indicating the NSS of the downlink frame transmitted on the first link, and Switching the second chain from the first chain to the second chain further includes: Decode the preamble at the PHY layer to generate primitives; NSS is identified at the MAC layer based on the aforementioned primitives; and Information indicating the use of the second link is obtained based on NSS.

8. The method according to claim 7, wherein, The primitive includes RXVECTOR information.

9. A method performed by an access point (AP) in a wireless local area network system, the method comprising: Send an initial frame on the first link to begin Enhanced Multi-Link Multi-Radio (EMLMR) operation; Information for data frame transmission is sent on the second link; Receive information approving the use of the second link; as well as Data frames are sent on the second link.

10. The method according to claim 9, wherein, The information includes information about the modulation and coding scheme (MCS) and the number of spatial streams (NSS) used for the second link.

11. The method of claim 9, further comprising performing a channel access procedure on a second link.

12. The method according to claim 11, wherein, The channel access procedure includes counting operations for Enhanced Distributed Channel Access (EDCA) backoffs, and The backoff counter is zero, and the data frame is sent after an EMLMR delay from the end of the transmission of the first information.

13. The method according to claim 11, wherein, The channel access procedure includes counting EDCA backoff operations, and The data frame is sent after an EMLMR delay, based on a backoff counter of zero and the end of the transmission of information from the point when the use of the second link is approved.

14. A method performed by an access point (AP) in a wireless local area network system, the method comprising: Send an initial frame on the first link to begin Enhanced Multi-Link Multi-Radio (EMLMR) operation; Receive information for data frame transmission on the second link; Send a trigger frame on the second link; as well as Based on the information, data frames are received on the second link.

15. A method performed by a station (STA) in a wireless local area network system, the method comprising: At least one of sending and receiving is performed on the first link using the first link; At least one of sending and receiving is performed on the second link; Receive an initial frame on the first link to initiate Enhanced Multi-Link Multi-Radio (EMLMR) operation; Based on the initial frame, switch the second link of the second link to the first link; Receive information for data frame transmission on the second link; Based on the information, switch the second link from the first link to the second link; Send information approving the use of the second link; as well as Based on the information, delay-sensitive data is received on the second link.

16. A station (STA) in a wireless local area network system, the STA comprising: transceiver; and The processor, which is connected to the transceiver, The processor is configured as follows: At least one of sending and receiving is performed on the first link using the first link; At least one of sending and receiving is performed on the second link; Receive an initial frame on the first link to initiate Enhanced Multi-Link Multi-Radio (EMLMR) operation; The second link (RF link) is switched to the first link based on the initial frame and the first information; Information for data frame transmission is sent on the second link; Based on the information, switch the second link from the first link to the second link; Receive trigger frames on the second link; and A data frame is sent based on at least one of the information and the trigger frame.

17. An access point (AP) in a wireless local area network system, the AP comprising: transceiver; and The processor, which is connected to the transceiver, The processor is configured as follows: Send an initial frame on the first link to begin Enhanced Multi-Link Multi-Radio (EMLMR) operation; Information for data frame transmission is sent on the second link; Receive information approving the use of the second link; and Data frames are sent on the second link.

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