Apparatus and method for fast error reporting in wireless local area network system

Abstract

For fast error reporting in a wireless local area network system, such a method for operating a station (STA) in a wireless local area network system may comprise the steps of: transmitting a plurality of frames in a first link; receiving, in the second link, an error report of a frame for which an error is detected among the plurality of frames; and transmitting, based on the error report, a resending frame including the frame in which the error is detected, in which each of the plurality of frames includes a delimiter, and the delimiter includes information for distinguishing each of the plurality of frames.

Description

TECHNICAL FIELD

[0001] The present application relates to a wireless local area network (WLAN) system, and more particularly, to an apparatus and method for fast error reporting in a wireless local area network (WLAN) system. BACKGROUND

[0002] Recently, as mobile devices are popularized, a wireless local area network technology capable of providing a fast wireless communication service to the mobile devices has been spotlighted. The wireless local area network technology can be a technology for supporting a mobile device (e.g., a smart phone, a smart tablet, a laptop computer, a portable multimedia player, an embedded device, etc.) to access the Internet in a wireless manner based on a wireless communication technology.

[0003] As applications requiring higher throughput and applications requiring real-time transmission have emerged, an IEEE 802.11be standard as an Extreme High Throughput (EHT) wireless local area network technology is being developed. The IEEE 802.11be standard can target supporting a high throughput of 30 Gbps. The IEEE 802.11be standard can support a technology for reducing transmission latency. In addition, the IEEE 802.11be standard can support a further extended frequency bandwidth (e.g., a 320 MHz bandwidth), a multi-link transmission and aggregation operation including operation using multiple frequency bands (multi-band), a multi-Access Point (AP) transmission operation, and / or an efficient retransmission operation (e.g., a Hybrid Automatic Repeat Request (HARQ) operation).

[0004] On the other hand, the technology described in the background section is written in order to improve the understanding of the background of the present application, and can include what is not known to those of ordinary skill in the art to which the present application pertains. SUMMARY

[0005] TECHNICAL PROBLEM The present application provides a method and apparatus for detecting and reporting errors in a frame received by an Access Point (AP) in a wireless local area network system.

[0006] The present application provides a method and apparatus for enabling a Station (STA) to quickly recover a frame in which an error is detected in a wireless local area network system.

[0007] The present application provides a method and apparatus for enabling an AP and a STA utilizing a Simultaneous Transmit and Receive (STR) link pair to report and recover errors in a frame utilizing multiple links in a wireless local area network system.

[0008] The present application provides a method and apparatus for identifying a frame for recovery from an error frame in a wireless LAN system.

[0009] The present application provides a method and apparatus for exchanging information for identifying a frame in a wireless LAN system.

[0010] The technical objects to be achieved in the present application are not limited to the above described, and other technical objects not mentioned herein can be considered by those skilled in the art of the technical field to which the present application pertains from the embodiments of the present application to be described below.

[0011] Technical Solution According to an embodiment of the present application, a method for operating a station (STA) in a wireless LAN system can include transmitting a plurality of frames in a first link, receiving an error report of a frame in which an error is detected among the plurality of frames in a second link, and transmitting a retransmission frame including the frame in which the error is detected based on the error report. Each of the plurality of frames includes a delimiter, and the delimiter includes information for distinguishing each of the plurality of frames.

[0012] A method for operating an access point (AP) in a wireless LAN system can include receiving a plurality of frames in a first link, detecting an error in at least one frame among the plurality of frames, transmitting an error report based on the frame in which the error is detected, and receiving a retransmission frame transmitted based on the error report. Each of the plurality of frames includes a delimiter, and the delimiter includes information for distinguishing each of the plurality of frames.

[0013] A station (STA) in a wireless LAN system can include a transceiver and a processor connected to the transceiver. The processor can be configured to transmit a plurality of frames in a first link, receive an error report of a frame in which an error is detected among the plurality of frames in a second link, and transmit a retransmission frame including the frame in which the error is detected based on the error report. Each of the plurality of frames includes a delimiter, and the delimiter includes information for distinguishing each of the plurality of frames.

[0014] An access point (AP) in a wireless LAN system can include a transceiver and a processor connected to the transceiver. The processor can be configured to receive a plurality of frames in a first link, detect an error in at least one frame among the plurality of frames, transmit an error report based on the frame in which the error is detected, and receive a retransmission frame transmitted based on the error report. Each of the plurality of frames includes a delimiter, and the delimiter includes information for distinguishing each of the plurality of frames.

[0015] Advantageous Effects According to the present application, a feedback frame including time information capable of identifying a frame in which an error is detected can be transmitted in a wireless LAN system.

[0016] According to the present application, an MPDU including information about a previous MPDU and a next MPDU can be transmitted.

[0017] According to the present application, an AP can recognize a frame in which an error is detected and transmit a feedback frame.

[0018] Effects obtained in the present application are not limited to the above-mentioned effects, and other effects not mentioned above can be clearly deduced and understood by persons skilled in the art of the technical field to which the present application pertains from the following description of embodiments of the present application. That is, persons skilled in the art can also deduce, from the embodiments of the present application, effects unintended in implementing the configurations described in the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a block diagram showing a first embodiment of a communication node constituting a wireless local area network system.

[0020] Figure 2 A first embodiment of a negotiation procedure for multi-link operation in a wireless local area network system is shown.

[0021] Figure 3 A first embodiment of a fast error feedback method is shown.

[0022] Figure 4a A second embodiment of a fast error feedback method is shown.

[0023] Figure 4b A third embodiment of a fast error feedback method is shown.

[0024] Figure 5 A fourth embodiment of a fast error feedback method is shown.

[0025] Figure 6 A fifth embodiment of a fast error feedback method is shown.

[0026] Figure 7 A flowchart showing an error recovery procedure according to an embodiment of the present application is shown.

[0027] Figure 8 A flowchart showing an error recovery procedure according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0028] The present application can have various modifications and embodiments, specific embodiments of which are shown in the drawings and described in detail in the detailed description. However, this is not intended to limit the present application to specific embodiments, but should be understood to include all modifications, equivalents, or alternatives contained in the spirit and technical scope of the present application.

[0029] The terms first, second, etc. can be used to describe various components, but the components should not be limited by these terms. These terms are only used to distinguish one component from another. For example, a first component could be termed a second component, and, similarly, a second component could be termed a first component, without departing from the scope of the present application. The terms and / or a combination of multiple related terms refer to any one of the related terms.

[0030] When it is said that a component is "coupled to" or "connected to" another component, it should be understood that the component is directly connected to the other component or connected to the other component through any other components in between. On the other hand, when it is said that a component is "directly connected to" or "directly coupled to" another component, it should be understood that there are no other components between the components.

[0031] The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present application. The singular expression includes the plural expression, unless the context clearly dictates otherwise. In the present application, terms such as "include" or "have" are intended to indicate that there is a feature, number, step, operation, component, part or a combination thereof described in the specification, but it should be understood that the possibility of existence or addition of one or more other features, numbers, steps, operations, components, parts or a combination thereof is not precluded.

[0032] Unless otherwise defined, all terms (including technical terms or scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense, unless expressly so defined herein.

[0033] Hereinafter, various exemplary embodiments of the present application will be described in greater detail with reference to the accompanying drawings. In order to facilitate overall understanding of the present application in describing the present application, the same reference numerals are used throughout the drawings for the same components and repetitive description thereof is omitted.

[0034] Hereinafter, a wireless communication system to which embodiments of the present application are applied will be described. The wireless communication system to which embodiments of the present application are applied is not limited to the following description and can be applied to various wireless communication systems. The wireless communication system can be referred to as a "wireless communication network."

[0035] Figure 1 A block diagram of a communication node in a wireless local area network system is shown.

[0036] Reference Figure 1Communication 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. The operating channel width supported by the STA can be 20 MHz or 80 MHz.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] Figure 2 This is a flowchart illustrating a first implementation of a negotiation process for multi-link operation in a wireless local area network system.

[0041] refer to Figure 2 In the basic service set (BSS), the access process between a station (STA) and an access point (AP) may include a probe step for detecting the access point, an authentication step between the station and the detected access point, and an association step between the station and the authenticated access point.

[0042] During the probe phase, a station can detect one or more access points using either a passive or active scanning method. When using a passive scanning method, the station can detect one or more access points by listening to beacon frames sent by them. When using an active scanning method, the station can send probe request frames and can detect one or more access points by receiving probe response frames (responses to the probe request frames) from one or more access points.

[0043] When one or more access points are detected, the station can perform authentication steps with the detected access points. In this case, the station can perform authentication steps with multiple access points. Authentication algorithms according to the IEEE 802.11 standard can be divided into, for example, open system algorithms that exchange two authentication frames and shared key algorithms that exchange four authentication frames.

[0044] The station can send authentication request frames based on the authentication algorithm according to the IEEE 802.11 standard, and can complete authentication with the access point by receiving authentication response frames (which are responses to the authentication request frames) from the access point.

[0045] Once authentication with an access point is complete, the station can perform the association step with that access point. In this case, the station can select one of the access points with which it has already completed the authentication step, and can then perform the association step with the selected access point. That is, the station can send an association request frame to the selected access point and complete the association with the selected access point by receiving an association response frame (which is a response to the association request frame) from the selected access point.

[0046] On the other hand, multi-link operation can be supported in a wireless LAN system. A multi-link device (MLD) can include one or more STAs associated with the MLD. The MLD can be a logical entity. MLDs can be divided into AP MLDs and non-AP MLDs. Each STA associated with an AP MLD can be an AP, and each STA associated with a non-AP MLD can be a non-AP STA.

[0047] To configure multi-link operation, a multi-link discovery process and a multi-link establishment process can be performed. The multi-link discovery process can be performed during the probe step between the station and the access point. In this case, the multi-link information element (MLIE) can be included in the beacon frame, probe request frame, and / or probe response frame.

[0048] For example, in order to perform multi-link operation, during the probing step, information indicating whether multi-link operation is available and information about available links can be exchanged between the access point (e.g., an AP associated with an MLD) and the station (e.g., a non-AP STA associated with an MLD).

[0049] During the negotiation process for multi-link operation (e.g., multi-link establishment process), the access point and / or station can send information about the links to be used for multi-link operation. The negotiation process for multi-link operation can be performed during the access process between the station and the access point (e.g., in the association step), and the information elements required for multi-link operation can be set or changed via action frames during the negotiation process.

[0050] Furthermore, during the access process between the station and the access point (e.g., in the association step), the available links of the access point can be configured, and an identifier (ID) can be assigned to each link. Subsequently, during the negotiation and / or change process for multi-link operation, information indicating whether each link is active can be sent, and this information can be represented using the link ID.

[0051] Information indicating whether multi-link operation is available can be sent and received during the exchange of performance information elements (e.g., extremely high throughput (EHT) performance information elements) between the station and the access point. Performance information elements may include information about supported frequency bands, information about supported links (e.g., the ID and / or number of supported links), and information about links capable of simultaneous transmit and receive (STR) operation (e.g., link frequency band information and link spacing information). Performance information elements may further include information separately indicating which links are capable of STR operation.

[0052] Figure 3 A first implementation of the rapid error feedback method is shown.

[0053] refer to Figure 3AP MLD 1 and STA MLD 1 can operate in a wireless LAN. AP MLD 1 operates on the first link with AP 1 301, and AP MLD 1 operates on the second link with AP 2 303. That is, AP1 301 and AP 2 303 can be associated with AP MLD 1. Similarly, STA MLD 1 operates on the first link with STA 1 311, and STA MLD 1 operates on the second link with STA 2 313. That is, STA 1 311 and STA 2 313 can be associated with STA MLD 1. In the second link, STA Y320 associated with STA MLD X can operate. X and Y can be natural numbers. For example, STA MLD X can or cannot be STA MLD 1. STA Y320 can or cannot be STA 2 313. The first and second links of STA MLD 1 can be links capable of simultaneous transmission and reception (STR link pair). Alternatively, the first and second links of STA MLD 1 can be links that cannot transmit and receive simultaneously (NSTR link pair), but can be conditional STR link pair or conditional NSTR link pair, which can transmit in one link while receiving in the other link when STA MLD 1 receives frames transmitted by the AP using strong transmit power and / or a low modulation and coding scheme (MCS).

[0054] STA 1 311 can acquire a transmission opportunity (TXOP) in the first link. TXOP acquisition is achieved when STA 1 311's EDCAF determines to transmit via a channel access procedure (e.g., EDCA backoff operation). STA 1 311 can transmit frames (e.g., PPDU (Physical Layer Protocol Data Unit), MPDU (MAC Layer Protocol Data Unit), A-MPDU (Aggregated MPDU)) within a TXOP. STA 1 311 can transmit A-MPDUs to AP 1 301, and an A-MPDU comprises multiple MPDUs. Delimiters that distinguish MPDUs can be included between MPDUs. The delimiter can consist of 32 bits and can include at least one of an MPDU length indicator (e.g., 14 bits), a CRC (Cyclic Redundancy Check) (e.g., 8 bits), and a delimiter signature (e.g., 8 bits). When AP 1 301 receives an MPDU sent by STA 1 311, it can receive MPDU #1, MPDU #2 330, and MPDU #3 340 sequentially. Among the MPDUs received by AP 1 301, MPDU #2 330 may contain errors (e.g., undecoded, FCS (Frame Check Sequence) error) and may not be received correctly. Because MPDU #2 330 is not received correctly, AP 1 301 may be unable to send the data in the queue to the upper layer. Alternatively, MPDU #2 330 may be a frame that urgently needs to be sent to the upper layer. Because MPDU #2 330 is not received correctly, it is not sent to the upper layer. To send a feedback frame 350 to recover MPDU #2 330, AP 2 303 may perform a channel access procedure (e.g., EDCA backoff operation) in the second link. The channel access procedure of AP 2 303 can be restarted to send a feedback frame 350 for recovering MPDU #2 330. Alternatively, the channel access procedure previously performed by AP 2 303 can continue instead of restarting the channel access procedure. The channel access procedure of AP 2 303 can be successful (e.g., the EDCA backoff counter reaches 0). AP 2 303 sends a feedback frame 350 to STA 2 313 indicating that MPDU #2 330 was not correctly received. The channel access procedure of AP 2 303 can be performed for each AC (access class). The feedback frame 350 can be sent through the channel access procedure of any AC (e.g., through the EDCAF of the AC whose channel access procedure completed fastest). Alternatively, if there is an EDCAF of any type of AC where AP 2 303 has successfully performed the channel access procedure (e.g., the EDCA backoff counter reaches 0) and remains at 0, the feedback frame 350 can be sent immediately.

[0055] Alternatively, feedback frame 350 can be sent via a channel access procedure associated with the AC of the MPDU of the frame sent by STA 1 311 to AP 1 301 on the first link (e.g., via AC_VO EDCAF on the second link when the AC of the MPDU sent by STA 1 311 to AP 1 301 is AC_VO). For example, the AC-specific channel access procedure of AP 2 303 can end AC_VO before AC_VI and other ACs (e.g., AC_BE and AC_BK). AP 2 303 can obtain AC_VOTXOP on the second link, and AP 2 303 sends feedback frame 350 to STA 2 313 indicating that MPDU #2 330 was not correctly received. In the remaining AC_VO TXOP of AP 2 303, AP 2 303 can send a data frame to STA Y 320.

[0056] Frame errors in the first link can be detected while a frame to be transmitted is being generated in the transmission queue of the second link and a channel access procedure is being performed. A frame for an AC to be transmitted in the second link can be generated, and a channel access procedure (e.g., a backoff procedure) can be performed. Errors can be detected in the MPDU received in the first link before the backoff counter becomes 0. The AC of the MPDU where the error occurred in the first link can be a different AC or the same AC as the AC being backoffed for transmission in the second link. If the channel access procedure is successful in the second link (e.g., if backoff is successful and the counter becomes 0), a TXOP of a certain length is set, which includes the feedback transmission time of the MPDU generated in the first link. That is, the duration included in the MAC header of the feedback frame 350 can be set to include the transmission time of the data frame for the AC to be transmitted. The receiving STAs for the feedback frame 350 and the data frame can be different. The feedback frame 350 can be transmitted first, followed by the data frame. Alternatively, the feedback frame 350 can be transmitted together with the data frame using a downlink Orthogonal Frequency Division Multiple Access (OFDMA) method, which utilizes different sub-channels for simultaneous transmission. Feedback transmission can be restricted only if the AC used to perform the channel access procedure for data to be transmitted in the second link has a lower priority than the AC that failed to transmit the MPDU in the first link. Alternatively, it can be assumed that the feedback of the MPDU that failed to transmit in the first link has higher priority than any AC. Therefore, if channel access for data transmission is successful in the second link, regardless of the AC, the feedback frame 350 can be transmitted together with the data transmission.

[0057] STA MLD 1 can receive feedback frame 350 from AP MLD 1, and STA MLD 1 can know that MPDU #2 330 was not correctly transmitted in the frame sent from STA 1 311 to AP 1 301 on the first link. STA MLD 1 can send or not send a response frame (e.g., an ACK frame) to AP MLD 1's feedback frame 350. STA MLD 1 can retransmit MPDU #2 330 in a frame that is already being transmitted. For example, MPDU #2 330 can be retransmitted after MPDU #3 340 (which is an MPDU following MPDU #2 330). Alternatively, STA MLD 1 can send MPDU #2 330 to AP 1 301 via a separate frame. AP MLD 1 can send the data in the queue to the upper layer when it normally receives the retransmitted MPDU #2 330. If an error occurs again in the retransmitted MPDU #2 330, the retransmission operation for MPDU #2 330 described above can be performed again. As another method to enable STA MLD 1 to perform retransmissions, STA 1 311 of STA MLD 1 can retransmit frames sent after MPDU #2 330 (e.g., MPDU #3 340) together, instead of just retransmitting MPDU #2 330. That is, STA 1 311 can retransmit frames starting from MPDU #2 330.

[0058] In the above implementation, when STA MLD 1 has a conditional NSTR link pair or a conditional STR link pair (e.g., when the first link and the second link are a conditional NSTR link pair), while STA MLD 1 transmits a frame to AP MLD 1 in the first link, AP MLD 1 transmits a frame to STA MLD 1 in the second link using strong transmit power and / or low MCS. In a conditional NSTR link pair or a conditional STR link pair, while a frame is being transmitted in one link, STA MLD can receive a frame in another link that meets specific conditions (e.g.). For example, STA MLD can receive a frame in the second link that meets the condition that the MCS in the first link is less than or equal to a certain value and the receive power is greater than or equal to a certain value. The feedback frame 350 in the above implementation can be a frame of various forms. For example, the feedback frame 350 can be one of a control frame including a block acknowledgment (BlockAck) frame, an action frame, and a QoS frame with a control field (e.g., an HT control field). The feedback frame 350 includes at least one of the following: the serial number (SN) and TID of the MPDU or / and MSDU, or information that can identify the MPDU or MSDU (e.g., time information that can identify the MPDU or MSDU, and MPDU identification by MPDU sequence within A-MPDU).

[0059] Figure 4a A second implementation of the rapid error feedback method is shown. Figure 4b A third implementation of the rapid error feedback method is shown.

[0060] refer to Figure 4a and Figure 4bAP MLD 1 and STA MLD 1 can operate in a wireless LAN. AP MLD 1 operates as AP 1 401 on the first link, and as AP MLD 1 operates as AP 2403 on the second link. That is, AP 1 401 and AP 2 403 can be associated with AP MLD 1. Similarly, STA MLD 1 can operate as STA 1 411 on the first link, and as STA MLD 1 operates as STA 2413 on the second link. That is, STA 1 411 and STA 2 413 can be associated with STA MLD 1. In the second link, STA Y 420 associated with STA MLD X can operate. X can be a natural number. Y can be a natural number. For example, STA MLD X can or cannot be STA MLD 1. STA Y 420 can or cannot be STA 2 413. The first and second links of STA MLD 1 can be links capable of simultaneous transmission and reception (STR link pair). Alternatively, the first and second links of STA MLD 1 can be links that cannot be simultaneously transmitted and received (NSTR link pair), but can be conditional STR link pairs or conditional NSTR link pairs, which can transmit on one link while receiving on the other link when STA MLD 1 receives frames transmitted by the AP using high transmit power and / or low MCS (modulation and encoding scheme).

[0061] STA 1 411 can acquire a TXOP in the first link. TXOP acquisition is achieved when STA 1 411's EDCAF determines to transmit via a channel access procedure (e.g., EDCA backoff operation). STA 1 411 can transmit frames (e.g., PPDU (Physical Layer Protocol Data Unit), MPDU (MAC Layer Protocol Data Unit), A-MPDU (Aggregated MPDU)) within a TXOP. STA 1 411 can send an A-MPDU to AP 1 401, and the A-MPDU comprises multiple MPDUs. Delimiters that distinguish MPDUs can be included between MPDUs. The delimiter can consist of 32 bits and can include at least one of an MPDU length indicator (e.g., 14 bits), a CRC (Cyclic Redundancy Check) (e.g., 8 bits), and a delimiter signature (e.g., 8 bits). When AP 1 401 receives MPDUs transmitted by STA 1 411, it can receive MPDU #1, MPDU #2 430, and MPDU #3 440 sequentially. In the MPDU received by AP1 401, MPDU #2 430 may contain errors (e.g., undecoded, FCS error) and may not be received correctly. Because MPDU #2 430 was not received correctly, AP1 401 may be unable to send the data in the queue to the upper layer. Alternatively, MPDU #2 430 may be a frame that urgently needs to be sent to the upper layer. Because MPDU #2 430 was not received correctly, it was not sent to the upper layer.

[0062] refer to Figure 4aAP MLD 1 is sending frames to STA Y 420 on the second link while simultaneously receiving frames from STA 1 411 on the first link. That is, AP MLD 1 is already sending frames on the second link within the TXOP acquired by AP MLD 1. AP 2 403 of AP MLD 1 can stop sending frame 460 to STA Y 420 in order to send a feedback frame 450 to STA 2 413 indicating that MPDU #2 430 was not correctly received. Frame 460 sent to STA Y 420 may include an indicator (e.g., a CS request) indicating that STA Y 420 must perform channel sensing (CS) before sending a response frame (e.g., a BlockAck frame) to AP 2 403 and, as a result of channel sensing, only send a response frame if the channel is idle for a certain period of time. Frame 460 sent to STA Y 420 may include a long or short channel sensing time indicator. A long or short channel listen time indicator may be included only if a channel listen request indicator is included. A long channel listen time indicator indicates that channel listening will be performed during the PIFS time period, while a short channel listen time indicator indicates that channel listening will be performed during the SIFS time period. Alternatively, when a channel listen time indicator is set, it can be interpreted as a long channel listen time indicator, and when no channel listen time indicator is set, it can be interpreted as a short channel listen time indicator. Alternatively, when a channel listen request indicator is included, it can be assumed that a long channel listen time indicator indicating channel listening during the PIFS time period instead of the SIFS time period is included, but a channel time listen time indicator is not included. The channel listen request indicator (CS request) may be included in the MAC header. When a feedback frame 450 is sent after a RIFS time period shorter than the SIFS time period, the channel listen time indicator may not be included; when the channel listen request indicator is included, the receiving STA will only send a response frame after performing channel listening during the SIFS time period and the channel is idle. The transmission of frames from AP 2 403 to STAY 420 can be stopped using an MPDU unit. For example, frames to be transmitted from AP 2 403 to STAY 420 may include MPDU #A, MPDU #B, and MPDU #C, and frame transmission can be stopped after MPDU #A and MPDU #B have been completely transmitted. That is, MPDU #A and MPDU #B were not lost. Alternatively, the transmission of frame 460 from AP 2 403 to STAY 420 can be stopped immediately. For example, frames to be transmitted from AP 2 403 to STAY 420 may include MPDU #A, MPDU #B, and MPDU #C, and frame transmission can be stopped while MPDU #A is being transmitted and MPDU #B is being transmitted.In this scenario, MPDU #A is not lost, but MPDU #B is lost. Stopping transmission can be determined by considering the importance of the MPDU to be transmitted (e.g., AC priority, delay limits). If the AC priority of the frame whose error was detected in the first link is higher than the AC priority of the frame to be transmitted in the second link, transmission can be stopped immediately even if loss occurs. Alternatively, stopping transmission can be determined by considering the delay limits of the frame to be transmitted. Even if the frame to be transmitted in the second link is immediately stopped and retransmitted, transmission can be stopped immediately if the delay limits are met. AP 2 403 stops frame transmission, and after a certain period of time (e.g., SIFS (Short Interframe Spacing) or RIFS (Reduced Interframe Spacing)), AP 2 403 can send a feedback frame 450 to STA 2 413 indicating that MPDU #2 430 was not correctly received. The feedback frame 450 can be transmitted using Orthogonal Frequency Division Multiple Access (OFDMA). For example, OFDMA can be used to transmit a feedback frame 450 (receiver STA 2 413) and a data frame (receiver STA Y 420) together using different sub-channels. When the transmission of a data frame received from AP 2 403 has terminated and the received data frame includes a channel listening request indicator, STA Y 420 performs channel listening and then sends a response frame to AP 2 403. If the channel becomes busy due to AP 2 403 sending a frame (e.g., feedback frame 450) during channel listening, no response frame is sent after a certain period of time (e.g., SIFS or PIFS).

[0063] Because AP 2 403 sends feedback frame 450 to STA 2 413 after a certain period of time (e.g., RIFS or SIFS), STA Y 420 does not send a response frame to AP 2 403. After sending feedback frame 450 to STA 2 413, AP 2403 can send a data frame to STA Y 420 again, and STA Y 420 sends a response frame to AP 2 403. STA MLD 1 can receive feedback frame 450 from AP MLD 1, and STA MLD 1 knows that MPDU #2 430 was not correctly transmitted in the frame sent from STA 1 411 to AP 1 401 on the first link. STA MLD 1 can send or not send a response frame (e.g., an ACK frame) to AP MLD 1's feedback frame 450. STA MLD 1 can retransmit MPDU #2 430 in a frame that is already being transmitted. For example, MPDU #2 430 can be retransmitted after MPDU #3 440 (which is an MPDU following MPDU #2 430). Alternatively, STA MLD 1 can send MPDU #2 430 to AP 1 401 via a separate frame. AP MLD 1 can send the data in its queue to the upper layer upon normal receipt of the retransmitted MPDU #2 430. If an error occurs again in the retransmitted MPDU #2 430, the retransmission operation of MPDU #2 430 can be performed again. As another way to enable STA MLD 1 to perform retransmission, STA 1 411 of STA MLD 1 can retransmit frames sent after MPDU #2 430 (e.g., MPDU #3 440) together, instead of just retransmitting MPDU #2 430. That is, STA 1 411 can retransmit frames starting from MPDU #2 430.

[0064] In the above implementation, when STA MLD 1 has a conditional NSTR link pair or a conditional STR link pair (e.g., when the first link and the second link are a conditional NSTR link pair), while STA MLD 1 is transmitting frames to AP MLD 1 in the first link, AP MLD 1 transmits frames to STA MLD 1 in the second link using high transmit power and / or low MCS. In a conditional NSTR link pair or a conditional STR link pair, while frames are being transmitted in one link, STA MLD can receive frames that meet specific conditions in the other link. For example, STA MLD can receive frames in the second link that meet the conditions that the MCS in the first link is less than or equal to a certain value and the receive power is greater than or equal to a certain value.

[0065] The feedback frame 450 in the above embodiment can be a frame of various forms. For example, the feedback frame 450 can be one of a control frame including a block acknowledgment (BlockAck) frame, an action frame, and a QoS frame with a control field (e.g., an HT control field). The feedback frame 450 includes at least one of the following: the sequence number (SN) and TID of the MPDU and / or MSDU, or information that can identify the MPDU or MSDU (e.g., time information that can identify the MPDU or MSDU, and the MPDU identified by the MPDU sequence within the A-MPDU).

[0066] refer to Figure 4b When AP MLD 1 receives a frame from STA MLD 1 on the first link, AP MLD 1 can send a MU-RTS frame as the first frame of the TXOP on the second link to ensure the successful transmission of feedback frame 450. The MU-RTS frame can indicate the STA with which it will communicate within the TXOP. For example, in the user information field included in the MU-RTS frame, AP MLD 1 can indicate the AID with which it will communicate within the TXOP. (Reference) Figure 4bWhen the communication target STA has MLD 1 and MLD X, the AID included in the MU-RTS frame indicates STA MLD 1 and STA MLD X. Since an AID is assigned to each MLD, the AID of STA MLD X can be the same as the AID of STA Y 420. STA MLD 1 and STA MLD X can receive MU-RTS frames in the second link and simultaneously send CTS frames (e.g., synchronization CTS frames) after a certain period of time (e.g., SIFS time) following the reception of the MU-RTS in the second link. After receiving the CTS frame in the second link, AP MLD 1 sends data frames to STA Y 420 in the second link. AP 2 403 of AP MLD 1 can stop sending frames to STA Y 420 in order to send a feedback frame 450 indicating that MPDU #2 430 was not correctly received by STA 2 413. Frame 460 sent to STAY 420 may include an indicator (e.g., a CS request) indicating that STAY 420 should perform channel sensing (CS) before sending a response frame (e.g., a BlockAck frame) to AP 2 403 and only send the response frame if the channel is idle for a certain period of time based on the result of channel sensing. Frame 460 sent to STAY 420 may include a long or short channel sensing time indicator. A long or short channel sensing time indicator may be included only if a channel sensing request indicator is included. A long channel sensing indicator indicates that channel sensing is performed during the PIFS time, while a short channel sensing indicator indicates that channel sensing is performed during the SIFS time. Alternatively, when a channel sensing time indicator is set, it can be interpreted as a long channel sensing indicator, and when no channel sensing time indicator is set, it can be interpreted as a short channel sensing indicator. Alternatively, when a channel listening request indicator is included, it can be considered to include a long channel listening indicator indicating that channel listening is performed during the PIFS time period instead of the SIFS time period, without including a channel listening time indicator. The channel listening request indicator (CS request) can be included in the MAC header. When a feedback frame 450 is sent after a RIFS time period shorter than the SIFS time, the channel listening time indicator may be omitted; when the channel listening request indicator is included, the STA receiving it will only send a response frame when the channel is idle after performing channel listening during the SIFS time period. The transmission of frame 460 from AP 2 403 to STA Y 420 can be stopped at an MPDU unit. For example, a frame sent from AP 2 403 to STA Y 420 may include MPDU #A, MPDU #B, and MPDU #C, and frame transmission can be stopped after MPDU #A and MPDU #B have been completely transmitted.That is, MPDU #A and MPDU #B were not lost. Alternatively, the transmission of frame 460 from AP 2 403 to STAY 420 can be stopped immediately. For example, the frame to be transmitted from AP 2 403 to STAY 420 may include MPDU #A, MPDU #B, and MPDU #C, and frame transmission can be stopped while MPDU #A is being transmitted and MPDU #B is being transmitted. In this case, MPDU #A is not lost, but MPDU #B is lost. Stopping transmission can be determined by considering the importance of the MPDU to be transmitted (e.g., AC priority, delay limits). If the AC priority of the frame whose error is detected in the first link is higher than the AC priority of the frame to be transmitted in the second link, transmission can be stopped immediately even if loss occurs. Alternatively, stopping transmission can be determined by considering the delay limits of the frame to be transmitted. Even if the frame to be transmitted in the second link is immediately stopped and retransmitted, transmission can be stopped immediately if the delay limits can be met. AP 2 403 stops frame transmission. After a certain period of time (e.g., short interframe space (SIFS) or reduced interframe space (RIFS)), AP 2 403 can send a feedback frame 450 to STA 2 413 indicating that MPDU #2 430 was not correctly received. The feedback frame 450 can be sent using Orthogonal Frequency Division Multiple Access (OFDMA). For example, OFDMA can be used to send the feedback frame 450 (receiver STA 2 413) together with a data frame (receiver STA Y 420). When the data frame received from AP 2 403 has terminated and the received data frame includes a channel listening request indicator, STA Y 420 performs channel listening and then sends a response frame to AP 2403. If the channel becomes busy due to AP 2 403 sending a frame (e.g., feedback frame 450) during channel sensing, no response frame is sent after a certain period of time (e.g., SIFS or PIFS). Because AP 2 403 sends feedback frame 450 to STA 2 413 after a certain period of time (e.g., RIFS or SIFS), STA Y 420 does not send a response frame to AP 2 403. AP 2 403 can send feedback frame 450 to STA 2 413, then send a data frame to STA Y 420, and STA Y 420 sends a response frame to AP 2 403. STA MLD 1 can receive feedback frame 450 from AP MLD 1, and STA MLD 1 can know that MPDU #2 430 was not correctly transmitted in the frame sent from STA 1 411 to AP 1 401 on the first link.STA MLD 1 may or may not send a response frame (e.g., an ACK frame) to the feedback frame 450 of AP MLD 1. STA MLD 1 may retransmit MPDU #2 430 within a frame that is already being transmitted. For example, MPDU #2 430 may be retransmitted after MPDU #3 440 (which is an MPDU following MPDU #2 430). Alternatively, STA MLD 1 may send MPDU #2 430 to AP 1 401 via a separate frame. If AP MLD 1 receives the retransmitted MPDU #2 430 normally, it can send the data in the queue to the upper layer. If an error occurs again in the retransmitted MPDU #2 430, the retransmission operation of MPDU #2 430 can be performed again. As another method to enable STA MLD 1 to perform retransmissions, STA 1 411 of STA MLD 1 can retransmit frames sent after MPDU #2 430 (e.g., MPDU #3440), instead of only retransmitting MPDU #2 430. That is, STA 1 411 can retransmit frames starting from MPDU #2 430.

[0067] In the above implementation, when STA MLD 1 has a conditional NSTR link pair or a conditional STR link pair (e.g., when the first link and the second link are a conditional NSTR link pair), while STA MLD 1 is transmitting frames to AP MLD 1 in the first link, AP MLD 1 transmits frames to STA MLD 1 in the second link using high transmit power and / or low MCS. In a conditional NSTR link pair or a conditional STR link pair, while frames are being transmitted in one link, STA MLD can receive frames that meet specific conditions in the other link. For example, STA MLD can receive frames in the second link that meet the conditions that the MCS in the first link is less than or equal to a certain value and the receive power is greater than or equal to a certain value.

[0068] The feedback frame 450 in the above embodiment can be a frame of various forms. For example, the feedback frame 450 can be one of a control frame including a block acknowledgment (BlockAck) frame, an action frame, and a QoS frame with a control field (e.g., an HT control field). The feedback frame 450 includes at least one of the following: the sequence number (SN) and TID of the MPDU and / or MSDU, or information that can identify the MPDU or MSDU (e.g., time information that can identify the MPDU or MSDU, and the MPDU identified by the MPDU sequence within the A-MPDU).

[0069] Figure 5 A fourth implementation of the rapid error feedback method is shown.

[0070] refer to Figure 5 AP MLD 1 and STA MLD 1 can operate in a wireless LAN. AP MLD 1 operates as AP 1 501 in the first link, and as AP MLD 1 operates as AP 2 503 in the second link. That is, AP1 501 and AP 2 503 can be associated with AP MLD 1. Similarly, STA MLD 1 can operate as STA 1 511 in the first link, and as STA MLD 1 operates as STA 2 513 in the second link. That is, STA1 511 and STA 2 513 can be associated with STA MLD 1. In the second link, STA Y 520 associated with STA MLD X can operate. X can be a natural number. Y can be a natural number. For example, STA MLD X can or cannot be STA MLD 1. STA Y 520 can or cannot be STA 2 513. The first and second links of STA MLD 1 can be links capable of simultaneous transmission and reception (STR link pair). Alternatively, the first and second links of STA MLD 1 can be links that cannot be simultaneously transmitted and received (NSTR link pair), but can be conditional STR link pairs or conditional NSTR link pairs, which can transmit on one link while receiving on the other link when STA MLD 1 receives frames transmitted by the AP using high transmit power and / or low MCS (modulation and encoding scheme).

[0071] STA 1 511 can acquire a TXOP in the first link. TXOP acquisition is achieved when the STA 1 511's EDCAF determines to transmit via a channel access procedure (e.g., EDCA backoff operation). STA 1 511 can transmit frames (e.g., Physical Layer Protocol Data Units (PPDUs), MAC Layer Protocol Data Units (MPDUs), and Aggregated MPDUs (A-MPDUs)) within a TXOP. STA 1 511 can send A-MPDUs to AP 1 501, and an A-MPDU comprises multiple MPDUs. Delimiters that distinguish MPDUs can be included between MPDUs. The delimiter can consist of 32 bits and can include at least one of an MPDU length indicator (e.g., 14 bits), a CRC (Cyclic Redundancy Check) (e.g., 8 bits), and a delimiter signature (e.g., 8 bits). When AP 1 501 receives MPDUs transmitted by STA 1 511, it can receive MPDU #1, MPDU #2 530, and MPDU #3 540 sequentially. In the MPDU received by AP1 501, MPDU #2 530 may contain errors (e.g., undecoded, FCS error) and may not be received correctly. Because MPDU #2 530 was not received correctly, AP1 501 may be unable to send the data in the queue to the upper layer. Alternatively, MPDU #2 530 may be a frame that must be urgently sent to the upper layer. Because MPDU #2 530 was not received correctly, it was not sent to the upper layer. AP2 503 did not receive MPDU #2 530 correctly and therefore may not know any information about MPDU #2 530. For example, AP2 503 may not know the TID and SN of MPDU #2 530.

[0072] All MPDUs of a frame sent from STA 1 511 to AP 1 501 can be MPDUs with the same TID. For example, all MPDUs can have TID A. AP MLD 1 can know that MPDU #2 530 was not received in the frame received from STA 1 511 in the first link after decoding MPDU #3 540. After receiving MPDU #3 540, a feedback frame 550 indicating that MPDU #2 530 was not correctly received can be sent. Alternatively, the MPDUs of a frame sent from STA 1 511 to AP 1 501 can be MPDUs with different TIDs. For example, all MPDUs except MPDU #2 530 can have TID A, while MPDU #2 530 can have TID B. MPDU #2 530 can be an MPDU that must be sent urgently and can be sent among MPDUs with different TIDs. Because MPDU #2 530 has a different TID than the other MPDUs, after decoding MPDU #3 540, AP MLD 1 may not know that MPDU #2 530 was not received in the frame received from STA 1 511 in the first link. Alternatively, all MPDUs in the frame sent from STA 1 511 to AP 1 501 can have the same TID, but the SN order of the MPDUs may not be sent in sequence. For example, the SNs of MPDU #1, MPDU #2 530, and MPDU #3 540 could be 1, 3, and 2, respectively. Therefore, if MPDU #2 530 is not received, AP MLD 1 may not know whether MPDU #2 530 should be retransmitted.

[0073] STA 1 511 may include at least one of the following: a sequence number (SN), TID information, and whether fast recovery of the frame sent to AP 1 501 is required for the previous and / or next MPDU in the MAC header and / or A-MPDU delimiter. That is, STA 1 includes information capable of identifying each frame sent to AP 1 and / or the previous and / or next MPDU in the A-MPDU delimiter. In this case, if AP 1 501 correctly receives MPDU #1 but not MPDU #2 530, AP 1 501 can immediately know information about the erroneous MPDU #2 530 (e.g., TID, SN). If STA 1 511 indicates that MPDU #2 530 requires fast recovery, AP 1 501 can request a retransmission of MPDU #2 530.

[0074] To send feedback frame 550 for recovering MPDU #2 530, AP 2 503 may perform a channel access procedure (e.g., EDCA backoff operation) in the second link. The channel access procedure of AP 2 503 may be restarted to send feedback frame 550 for recovering MPDU #2 530. Alternatively, a channel access procedure previously performed by AP 2 503 may be continued instead of restarting the channel access procedure. The channel access procedure of AP 2 503 may succeed (e.g., the EDCA backoff counter reaches 0). AP 2 503 sends feedback frame 550 to STA 2 513 indicating that MPDU #2 530 was not correctly received. The channel access procedure of AP 2 503 may be performed for each AC (access class). The feedback frame 550 may be sent via the channel access procedure of any AC (e.g., via the EDCAF of the AC whose channel access procedure completes fastest). Alternatively, if there exists an EDCAF for any AC that AP 2 503 has successfully performed a channel access procedure (e.g., the EDCA backoff counter reaches 0) and remains at 0, a feedback frame 550 can be sent immediately. Alternatively, the feedback frame 550 can be sent via a channel access procedure associated with the AC of the MPDU of a frame sent from STA 1 511 to AP 1 501 on the first link (e.g., via AC_VO EDCAF on the second link when the AC of the MPDU sent from STA 1 511 to AP 1 501 is AC_VO). For example, the AC-specific channel access procedure of AP 2 503 can terminate AC_VO before AC_VI and other ACs (e.g., AC_BE and AC_BK). AP 2 503 can acquire AC_VO TXOP on the second link, and AP 2 503 can send a feedback frame 550 to STA 2 513 indicating that MPDU #2 530 was not correctly received. In the remaining AC_VO TXOP of AP 2 503, AP 2 503 can send data frames to STAY 520.

[0075] Frame errors in the first link can be detected while a frame to be transmitted is being generated in the transmission queue of the second link and a channel access procedure is being performed. A frame for an AC to be transmitted in the second link can be generated, and a channel access procedure (e.g., a backoff procedure) can be performed. Errors can be detected in the MPDU received in the first link before the backoff counter becomes 0. The AC of the MPDU where the error occurred in the first link can be a different AC or the same AC as the AC that is being backoffed for transmission in the second link. If the channel access procedure in the second link is successful (e.g., if the backoff is successful and the counter becomes 0), a TXOP of a certain length is set, which includes the feedback transmission time of the MPDU generated in the first link. That is, the duration included in the MAC header of the feedback frame 550 can be set to include the transmission time of the data frame for the AC to be transmitted. The receiving STAs for the feedback frame 550 and the data frame can be different. The feedback frame 550 can be transmitted first, followed by the data frame. Alternatively, the feedback frame 550 and the data frame can be transmitted together using a downlink orthogonal frequency division multiple access (OFDMA) method that utilizes different sub-channels to transmit them simultaneously. Feedback transmission can be restricted only if the AC used to perform the channel access procedure for data to be transmitted in the second link has a lower priority than the AC that failed to transmit the MPDU in the first link. Alternatively, it can be assumed that the feedback of the MPDU that failed to be transmitted in the first link has a higher priority than any AC. Therefore, if channel access for data transmission is successful in the second link, regardless of the AC, the feedback frame 550 can be transmitted together with the data transmission.

[0076] STA MLD 1 can receive feedback frame 550 from AP MLD 1, and STA MLD 1 can know that MPDU #2 530 was not correctly transmitted in the frame sent from STA 1 511 to AP 1 501 on the first link. STA MLD 1 can send or not send a response frame (e.g., an ACK frame) to AP MLD 1's feedback frame 550. STA MLD 1 can retransmit MPDU #2 530 in a frame that is already being transmitted. For example, MPDU #2 530 can be retransmitted after MPDU #3 540 (which is an MPDU following MPDU #2 530). Alternatively, STA MLD 1 can send MPDU #2 530 to AP 1 501 via a separate frame. AP MLD 1 can send the data in the queue to the upper layer when it normally receives the retransmitted MPDU #2 530. If an error occurs again in the retransmitted MPDU #2 530, the retransmission operation for MPDU #2 530 described above can be performed again. As another method to enable STA MLD 1 to perform retransmissions, STA 1 511 of STA MLD 1 can retransmit frames sent after MPDU #2 530 (e.g., MPDU #3 540) along with MPDU #2 530, instead of just retransmitting MPDU #2 530. That is, STA 1 511 can retransmit frames starting from MPDU #2 530.

[0077] In the above implementation, when STA MLD 1 has a conditional NSTR link pair or a conditional STR link pair (e.g., when the first link and the second link are a conditional NSTR link pair), while STA MLD 1 transmits frames to AP MLD 1 in the first link, AP MLD 1 transmits frames to STA MLD 1 in the second link using high transmit power and / or low MCS. In a conditional NSTR link pair or a conditional STR link pair, while frames are being transmitted in one link, STA MLD can receive frames that meet specific conditions in another link. For example, STA MLD can receive frames in the second link that meet the conditions that the MCS in the first link is less than or equal to a certain value and the receive power is greater than or equal to a certain value.

[0078] The feedback frame 550 in the above implementation scheme can be a frame of various forms. For example, the feedback frame 550 can be one of a control frame including a block acknowledgment (BlockAck) frame, an action frame, and a QoS frame with a control field (e.g., an HT control field). The feedback frame 550 includes at least one of the following: the sequence number (SN) and TID of the MPDU and / or MSDU, or information that can identify the MPDU or MSDU (e.g., time information that can identify the MPDU or MSDU, and the MPDU identified by the MPDU sequence within the A-MPDU).

[0079] Figure 6 A fifth implementation of the rapid error feedback method is shown.

[0080] refer to Figure 6 AP MLD 1 and STA MLD 1 can operate in a wireless LAN. AP MLD 1 operates on the first link with AP 1 601, and AP MLD 1 operates on the second link with AP 2 603. That is, AP1 601 and AP 2 603 can be associated with AP MLD 1. Similarly, STA MLD 1 operates on the first link with STA 1 611, and STA MLD 1 operates on the second link with STA 2 613. That is, STA 1 611 and STA 2 613 can be associated with STA MLD 1. In the second link, STA Y associated with STA MLD X can operate. X can be a natural number. Y can be a natural number. For example, STA MLD X can or cannot be STA MLD 1. STA Y can or cannot be STA 2 613. The first and second links of STA MLD 1 can be links capable of simultaneous transmission and reception (STR link pair). Alternatively, the first and second links of STA MLD 1 can be links that cannot transmit and receive simultaneously (NSTR link pair), but can be conditional STR link pair or conditional NSTR link pair, which can transmit in one link while receiving in the other link when STA MLD 1 receives frames transmitted by the AP using strong transmit power and / or low MCS (modulation and coding scheme).

[0081] STA 1 611 can acquire a TXOP in the first link. TXOP acquisition is achieved when the STA 1 611's EDCAF determines to transmit via a channel access procedure (e.g., EDCA backoff operation). STA 1 611 can transmit frames (e.g., PPDU (Physical Layer Protocol Data Unit), MPDU (MAC Layer Protocol Data Unit), A-MPDU (Aggregated MPDU)) within a TXOP. STA 1 611 can send an A-MPDU to AP 1 601, and the A-MPDU comprises multiple MPDUs. Delimiters that distinguish MPDUs can be included between MPDUs. The delimiter can consist of 32 bits and can include at least one of an MPDU length indicator (e.g., 14 bits), a CRC (Cyclic Redundancy Check) (e.g., 8 bits), and a delimiter signature (e.g., 8 bits). When AP 1 601 receives MPDUs transmitted by STA 1 611, it can receive MPDU #1, MPDU #2 630, and MPDU #3 640 sequentially. In the MPDU received by AP1 601, MPDU #2 630 may contain errors (e.g., undecoded, FCS error) and may not be received correctly. Because MPDU #2 630 was not received correctly, AP1 601 may be unable to send data in the queue to the upper layer. Alternatively, MPDU #2 630 may be a frame that must be urgently sent to the upper layer. Because MPDU #2 630 was not received correctly, it was not sent to the upper layer. AP2 603 did not receive MPDU #2 630 correctly and therefore may not know any information about it. For example, AP2 603 may not know the TID and SN of MPDU #2 630.

[0082] All MPDUs of a frame sent from STA 1 611 to AP 1 601 can be MPDUs with the same TID. For example, all MPDUs can have TID A. AP MLD 1 can know that MPDU #2 630 was not received in the frame received from STA 1 611 in the first link after decoding MPDU #3 640. After receiving MPDU #3 640, a feedback frame 650 indicating that MPDU #2 630 was not correctly received can be sent. Alternatively, the MPDUs of a frame sent from STA 1 611 to AP 1 601 can be MPDUs with different TIDs. For example, all MPDUs except MPDU #2 630 can have TID A, while MPDU #2 630 can have TID B. MPDU #2 630 can be an MPDU that must be sent urgently and can be sent among MPDUs with different TIDs. Because MPDU #2 630 has a different TID than the other MPDUs, after decoding MPDU #3 640, AP MLD 1 may not know that MPDU #2 630 was not received in the frame received from STA 1 611 in the first link. Alternatively, all MPDUs in the frame sent from STA 1 611 to AP 1 601 can have the same TID, but the SN order of the MPDUs may not be consistent. For example, the SNs of MPDU #1, MPDU #2 630, and MPDU #3 640 could be 1, 3, and 2, respectively. Therefore, if MPDU #2 630 is not received, AP MLD 1 may not know whether MPDU #2 630 should be retransmitted.

[0083] AP 2 603 may not be aware of the information in MPDU #2 630, but it can know when an error occurred. An error can be known when, after successfully receiving the delimiter of MPDU #1 or MPDU #2 630, only energy is detected without decoding, and then a delimiter sent before sending MPDU #3 640 is received. To send a feedback frame 650 to recover MPDU #2 630, AP 2 603 can perform a channel access procedure (e.g., EDCA backoff operation) in a second link. AP 2 603's channel access procedure can be restarted to send the feedback frame 650 to recover MPDU #2 630. Alternatively, the channel access procedure previously performed by AP 2 603 can be continued instead of restarting the channel access procedure. AP 2 603's channel access procedure can succeed (e.g., the EDCA backoff counter reaches 0). AP 2 603 sends a feedback frame 650 to STA 2 613 indicating that MPDU #2 630 was not correctly received. The channel access procedure of AP 2 603 can be performed for each AC (access class). The feedback frame 650 can be sent via the channel access procedure of any AC (e.g., via the EDCAF of the AC whose channel access procedure is completed fastest). Alternatively, the feedback frame 650 can be sent immediately if there is an EDCAF of any type of AC where AP 2 603 has successfully performed the channel access procedure (e.g., the EDCA backoff counter reaches 0) and remains 0. Alternatively, the feedback frame 650 can be sent via the channel access procedure associated with the AC of the MPDU of the frame sent from STA 1 611 to AP 1 601 on the first link (e.g., via the AC_VO EDCAF of the second link when the AC of the MPDU sent from STA 1 611 to AP 1 601 is AC_VO). For example, the AC-specific channel access procedure of AP 2 603 can terminate AC_VO before AC_VI and other ACs (e.g., AC_BE and AC_BK). AP 2 603 can acquire AC_VO TXOP in the second link, and AP 2 603 sends a feedback frame 650 to STA 2 613 indicating that MPDU #2 630 was not received correctly. In the remaining AC_VO TXOP of AP 2 603, AP 2 603 can send data frames to STA Y.

[0084] Frame errors in the first link can be detected while a frame to be transmitted is being generated in the transmission queue of the second link and a channel access procedure is being performed. A frame for an AC to be transmitted in the second link can be generated, and a channel access procedure (e.g., a backoff procedure) can be performed. Errors can be detected in MPDUs received in the first link before the backoff counter becomes 0. The AC of the MPDU where the error occurred in the first link can be a different AC or the same AC as the AC being backoffed for transmission in the second link. If the channel access procedure in the second link is successful (e.g., if backoff is successful and the counter becomes 0), a TXOP of a certain length is set, which includes the feedback transmission time of the MPDU generated in the first link. That is, the duration included in the MAC header of feedback frame 650 can be set to include the transmission time of the data frame for the AC to be transmitted. The receiving STAs for feedback frame 650 and the data frame can be different. Feedback frame 650 can be transmitted first, followed by the data frame. Alternatively, feedback frame 650 and the data frame can be transmitted together using a downlink orthogonal frequency division multiple access (OFDMA) method that utilizes different sub-channels for simultaneous transmission. Feedback transmission can be restricted only if the AC used to perform the channel access procedure for data to be transmitted in the second link has a lower priority than the AC that failed to transmit the MPDU in the first link. Alternatively, it can be assumed that the feedback of the MPDU that failed to be transmitted in the first link has a higher priority than any AC. Therefore, if channel access for data transmission is successful in the second link, regardless of the AC, the feedback frame 650 can be transmitted together with the data transmission.

[0085] Information indicating that MPDU #2 630 was not correctly received can be indicated as time information. For example, time information may include at least one of "TSF (Time Synchronization Function) information," "TSF information and offset," "time interval utilizing multiple TSF information," or "frame duration." When time information is indicated as "TSF information," it may indicate the start or end time of the last correctly received MPDU, the start or end time of the erroneous MPDU, or the duration of transmission of the erroneous MPDU. Alternatively, time information may be indicated as TSF information capable of identifying an error in MPDU #2 630. The TSF information indicated by AP MLD 1 may be based on the TSF of a first link or a second link. The TSF information indicated by AP MLD 1 may utilize some bits (e.g., some LSBs) of the TSF managed by AP MLD 1. When time information is indicated as "TSF information and offset," it may indicate at least one of "transmission period of the last correctly received MPDU" and "transmission period of the erroneous MPDU." Alternatively, the time information can be indicated as TSF information capable of identifying errors and offsets in MPDU #2 630. Offset information is time information indicating the time before or after the time indicated by the TSF information. For example, offset information can be indicated in TU units (1 TU = 1024 µs) or can be indicated using some LSBs of the TSF. Alternatively, the offset information can indicate the duration in the same or similar manner as the duration field included in the MAC header of the MPDU. The TSF information indicated by AP MLD 1 can be based on the TSF of the first link or the second link. When the time information is indicated as "time interval utilizing multiple TSF information," the time information can indicate at least one of "the transmission period of the last correctly received MPDU" or "the transmission period of the MPDU in which the error occurred." Alternatively, the time information can be indicated by multiple TSF information capable of identifying errors in MPDU #2 630. The multiple TSF information indicated by AP MLD 1 can be based on the TSF of the first link or the second link. Some or all of the multiple TSF information indicated by APMLD 1 can be indicated using some bits (e.g., some LSBs) of the TSF managed by AP MLD 1. When the time information is indicated as "frame duration", the time information can indicate at least one of "the transmission length of the last correctly received MPDU" or "the transmission length of the MPDU in which the error occurred". Alternatively, the time information can be indicated by duration information that can identify an error in MPDU #2 630. The duration of a frame can indicate the length of time in the same or similar manner as the duration field included in the MAC header of the MPDU.STA MLD 1 must record time information (e.g., TSF information when transmitting each MPDU, duration information for each MPDU) during the transmission period in order to correctly recover from a corrupted MPDU (e.g., MPDU #2 630). AP MLD 1 must record time information (e.g., TSF information when receiving each MPDU, duration information for each MPDU) during the reception period in order to correctly recover from a corrupted MPDU (e.g., MPDU #2 630).

[0086] STA MLD 1 can receive feedback frame 650 from AP MLD 1, and STA MLD 1 can use the timing information of AP MLD 1's feedback frame 650 to identify that MPDU #2 630 was not transmitted correctly. STA MLD 1 may or may not send a response frame (e.g., an ACK frame) to AP MLD 1's feedback frame 650. STA MLD 1 can retransmit MPDU #2 630 as the MPDU that caused the error within a frame that is already being transmitted. For example, MPDU #2 630 can be retransmitted after MPDU #3 640 (which is an MPDU following MPDU #2 630). Alternatively, STA MLD 1 can send MPDU #2 630 to AP 1601 via a separate frame. If AP MLD 1 receives the retransmitted MPDU #2 630 without an error, it can send the data in the queue to the upper layer. If an error occurs again in the retransmitted MPDU #2 630, the retransmission operation for MPDU #2 630 described above can be performed again. As another method to enable STA MLD 1 to perform retransmissions, STA 1 611 of STA MLD 1 can retransmit frames sent after MPDU #2 630 (e.g., MPDU #3640), instead of only retransmitting MPDU #2 630. That is, STA 1 611 can retransmit frames starting from MPDU #2 630.

[0087] In the above implementation, when STA MLD 1 has a conditional NSTR link pair or a conditional STR link pair (e.g., when the first link and the second link are a conditional NSTR link pair), while STA MLD 1 transmits frames to AP MLD 1 in the first link, AP MLD 1 transmits frames to STA MLD 1 in the second link using high transmit power and / or low MCS. In a conditional NSTR link pair or a conditional STR link pair, while frames are being transmitted in one link, STA MLD can receive frames that meet specific conditions in another link. For example, STA MLD can receive frames in the second link that meet the conditions that the MCS in the first link is less than or equal to a certain value and the receive power is greater than or equal to a certain value.

[0088] The feedback frame 650 in the above embodiment can be a frame of various forms. For example, the feedback frame 650 can be one of a control frame including a block acknowledgment (BlockAck) frame, an action frame, and a QoS frame with a control field (e.g., an HT control field). The feedback frame 650 includes at least one of the following: the sequence number (SN) and TID of the MPDU and / or MSDU, or information that can identify the MPDU or MSDU (e.g., time information that can identify the MPDU or MSDU, and MPDU identified by the MPDU sequence within the A-MPDU).

[0089] The procedure for detecting transmission errors will be described below. This procedure is performed by the first STA and the AP. The first STA and the AP can be connected using a first link and a second link. The first link and the second link can be an STR link pair. The AP can connect to the second STA using the second link. That is, the first STA, the second STA, and the AP can be a multi-link device (MLD).

[0090] Figure 7 A flowchart of an error recovery process according to an embodiment of the present invention is shown. Figure 7 The process performed by the first STA is shown. The first STA (e.g., Figure 3 STA MLD 1) connects to the AP using the first and second links (e.g., Figure 3 AP MLD 1).

[0091] refer to Figure 7 In step S701, the first STA transmits multiple frames in the first link (e.g., Figure 3(MPDU #2330 and MPDU #3340). Multiple frames may include at least one MPDU. Each frame may include a delimiter for distinguishing frames. The delimiter may include at least one of an MPDU length indicator, a CRC, or a delimiter signature. For example, the size of the delimiter may be 32 bits. In addition, the delimiter includes at least one of the following for receiver error detection: the sequence number (SN) of the MPDU including the delimiter or the next MPDU to be transmitted, TID information, or whether fast recovery is required.

[0092] In step S703, the first STA receives an error report in the second link. The error report includes a message sent from the AP when an error is detected in the frame transmitted in step S701. The error report may include information for reporting the error and requesting a retransmission. The error report may be included in the feedback frame (e.g., Figure 3 The error report may include information about the error. This information may directly indicate the frame in which the error was detected. Alternatively, the information may indirectly indicate the frame in which the error was detected. Indirect information may include time information. Time information includes at least one of the following: time synchronization function (TSF) information, TSF information and offset, time intervals using multiple TSF information, or the duration of the frame. The first STA may identify an error that has occurred during frame transmission based on the information about the error. For example, the first STA may identify the frame in which the error was detected by identifying the transmission time, transmission time interval, or transmission duration of the frame in which the error was detected based on the time information.

[0093] In step S705, the first STA sends a retransmission frame in the first link (e.g., Figure 3 MPDU #2 330). Here, retransmitting a frame may include a frame in which an error was detected. For example, a retransmitted frame may include at least one of the following: a frame in which an error was detected, or a frame transmitted after a frame in which an error was detected (e.g., Figure 3 (MPDU #3 340). A frame can be retransmitted after the transmission of a frame currently being transmitted in the first link is completed. Alternatively, a frame can be retransmitted after the transmission of a frame currently being transmitted in the first link is stopped.

[0094] Figure 8 A flowchart of an error recovery process according to an embodiment of the present invention is shown. Figure 8 The process performed by the AP is shown. The AP (e.g., Figure 3 AP MLD 1) connects to the first STA using the first link and the second link (e.g., Figure 3STAMLD 1) or second STA (e.g., Figure 3 At least one of the STA MLD X).

[0095] refer to Figure 8 In step S801, the AP receives multiple frames in the first link (e.g., Figure 3 (MPDU #2 330 and MPDU #3 340). Multiple frames can be frames used to transmit data. Multiple frames can include MPDUs. Multiple frames can be frames with the same TID. Alternatively, multiple frames can be frames with different TIDs. Each frame can include a delimiter. The delimiter can include at least one of an MPDU length indicator, a CRC, or a delimiter signature. For example, the size of the delimiter can be 32 bits. In addition, the delimiter includes at least one of the following for receiver error detection: the sequence number (SN) of the MPDU including the delimiter or the next MPDU to be transmitted, TID information, or whether fast recovery is required.

[0096] In step S803, the AP detects errors in multiple frames. At least one frame may be undecodeable, or an FCS error may occur in at least one frame. If the frames have the same TID, the AP can detect an error in one of these frames based on the SN. If the frames have different TIDs, or if the TIDs are the same but the frames were not sent in SN order, the AP can determine the time of error based on the delimiter. For example, after the AP receives a frame including the delimiter, if it detects power but cannot decode it, it can detect an error in the frame transmission.

[0097] In step S805, the AP sends an error report in the second link. The error report is sent to the first STA. The error report may be included in the feedback frame (e.g., Figure 3 In the feedback frame 350. To send an error report, the AP may stop sending frames that are being transmitted to the second STA in the second link. Alternatively, the AP may send an error report after completing the transmission of the frames that are being transmitted. The error report may include information about the error. The information about the error may be information about the frame that directly indicates that an error was detected. Alternatively, the information about the error may be information about the frame that indirectly indicates that an error was detected. The indirect indication information may include time information. The time information includes at least one of the following: time synchronization function (TSF) information, TSF information and offset, time intervals using multiple TSF information, or the duration of the frame.

[0098] In step S807, the AP receives a retransmitted frame in the first link (e.g., Figure 3MPDU #2 330). Retransmitted frames may include frames for which errors were detected. For example, retransmitted frames may include at least one of the following: frames for which errors were detected, or frames transmitted after frames for which errors were detected (e.g., ...). Figure 3 (MPDU #3 340). A frame can be retransmitted after the transmission of a frame currently being transmitted in the first link is completed. Alternatively, a frame can be retransmitted after the transmission of a frame currently being transmitted in the first link is stopped.

[0099] The first STA or AP acquires the TXOP to transmit a frame. To acquire the TXOP, the first STA or AP performs a channel access procedure. This procedure can be performed for each AC. The frame transmitted by the first STA and the error report transmitted by the AP can be transmitted based on the same AC. Alternatively, the frame transmitted by the first STA and the error report transmitted by the AP can be transmitted based on a different AC. The AP can stop transmitting frames to the second STA based on the AC that detected the erroneous frame, or send an error report after completing the transmission of the frame currently being transmitted. Alternatively, the frame or error report that detected the erroneous frame can be transmitted with a higher priority than the AC.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] Industrial availability This disclosure can be used in devices and recording media in wireless local area network systems.

Claims

1. A method for use as a station operator (STA) in a wireless local area network system, the method comprising: Multiple frames are sent in the first link; Error reports are received from multiple frames in the second link where errors are detected in the frames. as well as Based on error reports, retransmission frames are sent, including frames where errors were detected. Each of the multiple frames includes a delimiter, and The delimiter includes information for distinguishing each of the multiple frames.

2. The method according to claim 1, wherein, The error report includes information that directly indicates a frame where an error was detected or information that indirectly indicates a frame where an error was detected.

3. The method according to claim 2, wherein, Indirect indication information includes at least one of the following: TSF information, TSF information offset, time interval based on multiple TSFs, or frame duration.

4. The method according to claim 2, wherein, Direct indication information includes at least one of the following: the TID of the frame in which the error was detected, the sequence number (SN), or time information that can identify the frame in which the error was detected.

5. The method according to claim 1, wherein, The retransmission of a frame includes at least one of the following: a frame in which an error was detected, or a frame transmitted after an error was detected.

6. The method according to claim 1, wherein, Information used to distinguish each frame includes at least one of the following: a traffic identifier (TID) for each of the multiple frames, a sequence number (SN), or information indicating whether fast recovery is required.

7. The method according to claim 1, wherein, The multiple frames include frames with the same TID.

8. A method for operating an access point (AP) in a wireless local area network system, the method comprising: Receive multiple frames in the first link; Detect errors in at least one frame out of a set of multiple frames; Send an error report based on the frame in which the error was detected; as well as Receive retransmission frames sent based on error reports. Each of the multiple frames includes a delimiter, and The delimiter includes information for distinguishing each of the multiple frames.

9. The method according to claim 8, wherein, The error report includes information that directly indicates a frame where an error was detected or information that indirectly indicates a frame where an error was detected.

10. The method according to claim 9, wherein, Indirect indication information includes at least one of the following: TSF information, TSF information offset, time interval based on multiple TSFs, or frame duration.

11. The method according to claim 9, wherein, Direct indication information includes at least one of the following: the TID of the frame in which the error was detected, the sequence number (SN), or time information that can identify the frame in which the error was detected.

12. The method according to claim 8, wherein, Information used to distinguish each frame includes at least one of the following: a traffic identifier (TID) for each of the multiple frames, a sequence number (SN), or information indicating whether fast recovery is required.

13. The method according to claim 12, wherein, Error detection further includes detecting errors based on the TID or SN included in the delimiter.

14. The method according to claim 8, wherein, The retransmission of a frame includes at least one of the following: a frame in which an error was detected, or a frame transmitted after an error was detected.

15. The method according to claim 8, wherein, Error detection further includes detecting errors based on the time interval between receiving a frame containing a delimiter and receiving the next delimiter.

16. The method according to claim 8, wherein, Sending error reports includes: The decision to stop transmitting frames on the second link is based on the Access Class (AC) of the detected erroneous frame; and Error reports are sent based on whether to stop sending.

17. A station (STA) in a wireless local area network system, comprising: transceiver; as well as The processor, which is connected to the transceiver, The processor is configured as follows: Multiple frames are sent in the first link; Error reports of frames in which errors are detected among multiple frames received in the second link; and Based on error reports, retransmission frames are sent, including frames where errors were detected. Each of the multiple frames includes a delimiter, and The delimiter includes information for distinguishing each of the multiple frames.

18. An access point (AP) in a wireless local area network system, comprising: transceiver; as well as The processor, which is connected to the transceiver, The processor is configured as follows: Receive multiple frames in the first link; Detect errors in at least one frame out of a set of multiple frames; Send error reports based on frames where errors are detected; and Receive retransmission frames sent based on error reports. Each of the multiple frames includes a delimiter, and The delimiter includes information for distinguishing each of the multiple frames.

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