Long packets and fast acknowledgement on sidelink

Abstract

A wireless communication protocol operates with a multi-link device (MLD) having a simultaneous transmit and receive (STR) link pair to allow an initiator to transmit a long MU PPDU on a first link, which is acknowledged (Ack) by a receiver on a second link. The Ack on the second link can be on a single resource unit (RU) that can be shared by multiple stations. The Ack can be received during the MP PPDU on the first link, making it a fast Ack. In many cases, this allows the initiator to perform a retransmission within the same PPDU, which is particularly advantageous for real-time traffic that is sensitive to delay.

Description

[0001] (Cross-reference to related applications)

[0002] This application claims priority and benefit to U.S. Provisional Patent Serial No. 63 / 265712, filed December 20, 2021, which is incorporated herein by reference in its entirety.

[0003] (Statement regarding federally funded research or development)

[0004] not applicable

[0005] (Notice of Copyrighted Material)

[0006] Some of the material in this patent document may be protected by copyright laws in the United States and other countries. The copyright holder does not object to any faxed copying of the patent document or patent disclosure appearing in documents or records published by the U.S. Patent and Trademark Office, but retains all copyright. The copyright holder hereby does not waive any right to maintain the confidentiality of this patent document, including but not limited to its rights under 37.1.14 of the Code of Federal Regulations. Technical Field

[0007] The techniques disclosed herein generally relate to wireless network communications under CSMA / CA and EDCA, and more specifically, to providing fast acknowledgments for long packet traffic. Background Technology

[0008] In the current 802.11 protocol, Ack / BA immediately follows PPDU on the same link, and in addition to being used to confirm the reception status of each MPDU in the PPDU, it is also used by the CSMA / CA protocol to detect collisions. For efficiency, PPDU can contain data from multiple users, and for each user, the data can have multiple priorities. Multiplexing different users and priorities improves efficiency, but may result in excessively long PPDUs, which may increase latency.

[0009] For a low-latency MPDU within a long PPDU, if the receiver indicates a reception failure of the low-latency MPDU after the long PPDU has completed, the duration of the PPDU may be too long for the transmitter to perform a retransmission. In this case, the term "long" refers to the latency requirement relative to the latency-sensitive traffic. A retransmission following the long PPDU indicated above may have already violated the latency limits for latency-sensitive traffic.

[0010] Therefore, there is a need for a protocol that can process RTA traffic with reduced latency while using secondary links. This disclosure meets this need and provides additional benefits. Summary of the Invention

[0011] This description describes wireless communication in IEEE 802.11 networks that can provide fast acknowledgments and accelerated retransmissions. The description primarily addresses the use of multi-link devices (MLDs) with simultaneous transmit and receive (STR) capabilities, operating on networks using Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA), where enhanced distributed channel access (EDCA) is utilized for random channel access on all links.

[0012] The described protocol specifies that the initiating MLD sends a Physical Layer Protocol Data Unit (PPDU) (e.g., a long PPDU) containing one or more Aggregated MAC Protocol Data Units (AMPDUs) on the first link, and receives an Ack frame as a fast acknowledgment (Ack) from the receiving MLD via the second link before the initiator's PPDU transmission is completed on the first link.

[0013] This is particularly beneficial for delay-sensitive MPDUs, such as those related to real-time application (RTA) traffic, which are sent early in the PPDU and can then be acknowledged after the delay-sensitive portion is received, while the rest of the PPDU is still being sent.

[0014] Since retransmissions can be performed on the first and / or second links within the same long PPDU, the disclosed technology also allows for reduced latency.

[0015] This disclosure provides numerous options / modes / configurations for controlling how these fast Ack and retransmissions are performed.

[0016] Other aspects of the technology described herein will be introduced in the following sections of the specification, wherein the purpose of the detailed description is to fully disclose preferred embodiments of the technology without limiting them. Attached Figure Description

[0017] The techniques described herein will be more fully understood by referring to the following figures, which are for illustrative purposes only:

[0018] Figure 1 This is a block diagram of station (STA) hardware according to at least one embodiment of the present disclosure.

[0019] Figure 2 This is a block diagram of multi-link device (MLD) hardware according to at least one embodiment of the present disclosure.

[0020] Figure 3 This is a communication diagram of a PPDU according to at least one embodiment of the present disclosure, which illustrates the use of fast Ack timing or fast Ack link timing in long packet communication.

[0021] Figure 4This is a data field diagram using reserved bits in the MPDU delimiter (non-OMG) for indicating the next fast Ack opportunity, according to at least one embodiment of this disclosure.

[0022] Figure 5 This is the original AMPDU communication diagram for Link 1 without Fast Ack.

[0023] Figure 6 This is a communication diagram of explicit EDCA acknowledgment on L2 and retransmission on L1 according to at least one embodiment of this disclosure.

[0024] Figure 7 This is a communication sequence diagram of multiple Ack attempts during a delay block Ack between an initiating STA and a receiving STA according to at least one embodiment of this disclosure.

[0025] Figure 8 This is a communication diagram of implicit acknowledgment and retransmission according to at least one embodiment of the present disclosure.

[0026] Figure 9 This is a communication diagram of downlink (DL) retransmission on a backup link according to at least one embodiment of the present disclosure.

[0027] Figure 10 This is a communication diagram of fast Ack timing for uplink (UL) data according to at least one embodiment of the present disclosure.

[0028] Figure 11 This is a communication diagram of a shared Ack resource unit (RU) according to at least one embodiment of the present disclosure.

[0029] Figure 12 This is a communication diagram of a second shared Ack RU according to at least one embodiment of the present disclosure.

[0030] Figure 13 This is a communication diagram of a UL area for increasing access opportunities according to at least one embodiment of the present disclosure.

[0031] Figure 14 This is a communication diagram of UL+L1+DL+L2 according to at least one embodiment of the present disclosure.

[0032] Figure 15 It is a communication diagram of AP scheduling using the start and / or end times of transmission on a shared Ack RU using trigger frames (TF) on L2, according to at least one embodiment of the present disclosure.

[0033] Figure 16 and Figure 17 This is a flowchart illustrating the receiver processing of a long PPDU requiring an Ack according to at least one embodiment of this disclosure.

[0034] Figure 18 and Figure 19 This is a flowchart of the initiator processing of a long PPDU requiring an Ack, according to at least one embodiment of this disclosure.

[0035] Figure 20 This is a data field diagram of the fast Ack configuration field according to at least one embodiment of the present disclosure.

[0036] Figure 21 It is a data field diagram of special symbol configuration fields according to at least one embodiment of the present disclosure.

[0037] Figure 22 This is a data field diagram of a fast Ack configuration according to at least one embodiment of the present disclosure.

[0038] Figure 23 It is a data field diagram of shared Ack configuration elements according to at least one embodiment of the present disclosure.

[0039] Figure 24 This is a data field diagram of different shared Ack RU element examples according to at least one embodiment of this disclosure.

[0040] Figure 25 It is a data field diagram of a trigger frame having an additional subfield for fast retransmission allocation within a user information list, according to at least one embodiment of the present disclosure.

[0041] Figure 26 This is a data field diagram of a BA control field according to at least one embodiment of the present disclosure, the BA control field including the Fast Repeatable Subfield (MCS) and Nss subfields in previously reserved bits. Detailed Implementation

[0042] 1. Motivation and Hypothesis

[0043] In November 2022, at IEEE P802.11be TM / D2.3 and IEEE P802.11-REVme, October 2022 TM In / D2.0, find the current state of technology in this field.

[0044] A station (STA) with Real-Time Application (RTA) data can transmit a PPDU containing only short RTA data and request immediate acknowledgment to minimize latency in the event of retransmission. However, for various reasons, an access point (AP) or non-AP station (STA) may consider system efficiency or other access rules and decide not to send a PPDU containing only RTA data. For example, to utilize downlink (DL) multiple-user (MU) multiple-input multiple-output (MIMO) (by using other unused antennas / precoding vectors to send data to multiple users in the same PPDU), the AP may send an MU PPDU, causing the PSDU of the RTA user to be padded to the same length as the PSDUs of other users. In another example, the PPDU is a UL-triggered PPDU (TB-PPDU), and the length of the PPDU is determined by the AP. If the STA includes RTA data in the PSDU, the scheduled PPDU duration does not change, and it needs to include other data or padding to meet the PSDU length required for a TB-PPDU. In these cases where a STA or AP sends a relatively long PPDU containing short RTA data, the station (STA) or AP with real-time application (RTA) data can seek a fast acknowledgment (Ack) so that, if a second link is available to perform the acknowledgment (Ack), it can perform a retry, for example, before the MSDU expires and before the ongoing PPDU ends.

[0045] The transmitter can quickly send short PPDUs and receive block acknowledgments (BAs) on the same link. However, in this case, the transmitter sacrifices the efficiency of multi-user (MU) transmission because it cannot multiplex data to / from other users in the spatial and / or frequency domains.

[0046] There is an opportunity to use a long PPDU on the first link and an Ack on the second link. A long MU PPDU that has already acquired a channel, even if it is a low priority access class (AC), can contain a significant level of padding, which can be used to provide access for high priority traffic from other users, such as for retransmissions.

[0047] The time required to establish (construct) a long AMPDU in response to a trigger frame (TF) is less than 16 microseconds, thus enabling the insertion of a delayed RTA MPDU (after TXOP begins) into an ongoing AMPDU (to the same receiver) instead of aborting the ongoing AMPDU via a lower-priority AC.

[0048] If the transmitter receives a block acknowledgment (BA) before fully receiving the entire AMPDU, this allows for retransmission with the same AMPDU, as well as other retransmission options.

[0049] In these discussions, the multi-link device (MLD) of this disclosure is considered to provide simultaneous transmission and reception (STR) on the link in question. The MLD that sends the data MPDU to be acknowledged is referred to as the "initiator" MLD; while the MLD that sends an acknowledgment in response to receiving the data MPDU is referred to herein as the "receiver" MLD. Traffic identifiers (TIDs) are used to identify Real-Time Application (RTA) traffic, and traffic identified with an RTA TID does not carry non-RTA traffic.

[0050] 2. Example

[0051] 2.1. Communication Station (STA and MLD) Hardware

[0052] Figure 1 Example embodiment 10 of STA hardware configured to execute the protocols of this disclosure is shown. An external I / O connection 14 is preferably coupled to an internal bus 16 of circuitry 12, on which a CPU 18 for executing a program implementing the communication protocol and a memory (e.g., RAM) 20 are connected. The host computer houses at least one modem 22 to support communication coupled to at least one RF module 24, 28, each of which is connected to one or more antennas 29, 26a, 26b, 26c-26n. RF modules having multiple antennas (e.g., an antenna array) allow beamforming to be performed during transmission and reception. In this way, the STA can transmit signals by using multiple sets of beam patterns.

[0053] Bus 14 allows various devices to be connected to the CPU, such as sensors and actuators. Instructions from memory 20 are executed on processor 18 to carry out a program that implements a communication protocol, which allows the STA to perform the functions of an access point (AP) station or a regular station (non-AP STA). It should also be appreciated that the programming is configured to operate in different modes (TXOP holder, TXOP sharing participant, source, intermediate, destination, first AP, other APs, station associated with the first AP, station associated with other APs, coordinator, coordinated device, AP in OBSS and STA in OBSS, etc.) depending on its role in the current communication environment.

[0054] Therefore, the STA HW is shown configured with associated RF circuitry for providing communication in at least one frequency band and at least one modem. It should be understood that this disclosure may configure multiple modems 22, such that each modem is coupled to any number of RF circuits. Generally, using a larger number of RF circuits will result in a wider coverage area in the antenna beam pattern. It should be understood that the number of RF circuits and antennas used is determined by the hardware constraints of the specific device. When the STA determines that it does not need to communicate with neighboring STAs, a portion of the RF circuitry and antennas can be disabled. In at least one embodiment, the RF circuitry includes frequency converters and array antenna controllers, etc., and is connected to multiple antennas that are controlled to perform beamforming for transmission and reception. In this way, the STA can transmit signals by using multiple sets of beam patterns, each beam pattern direction being considered an antenna sector.

[0055] Additionally, it should be noted that, as illustrated in this diagram, multiple instances of station hardware can be combined into a multi-link device (MLD), which typically has processors and memory for coordinating activities. However, it should be understood that since each STA within an MLD does not always require a separate CPU and memory, these resources can be shared.

[0056] Figure 2 Example embodiment 40 illustrates a multi-link device (MLD) hardware configuration. A soft AP MLD consists of one or more auxiliary STAs operating as an AP. The soft AP MLD should support multiple radio operations on 2.4 GHz, 5 GHz, and 6 GHz. Among the multiple radio devices, the basic link set is a pair of links that satisfy the simultaneous transmit and receive (STR) mode, for example, a basic link set (2.4 GHz and 5 GHz) or a basic link set (2.4 GHz and 6 GHz).

[0057] Multiple STAs belong to the MLD, allowing each STA to operate on links at different frequencies. The MLD has external I / O access to applications, which connects to the MLD management entity 48, which has a CPU 62 and memory (e.g., RAM) 64, to allow the execution of programs that implement communication protocols at the MLD level. The MLD can assign tasks to its connected subsidiary stations (STA 1 42, STA 2 44 to STA N 46 in this example) and facilitate information sharing between subsidiary STAs, as well as collect information from them.

[0058] In at least one embodiment, each STA of the MLD has its own CPU 50 and memory (RAM) 52 coupled via bus 58 to at least one modem 54, which is connected to at least one RF circuit 56 having one or more antennas. In this example, such as in an antenna array, the RF circuit has multiple antennas 60a, 60b, 60c to 60n. The modem, combined with the RF circuit and associated antennas, transmits / receives data frames with adjacent STAs. In at least one implementation, the RF module includes a frequency converter, an array antenna controller, and other circuitry for connection to its antennas.

[0059] It should be understood that, since STAs can share resources with each other and / or with the MLD management entity according to a specific MLD implementation, each STA in an MLD does not necessarily need its own processor and memory. It should be understood that the above MLD diagram is given by way of example and not limitation, and this disclosure can operate in a wide range of MLD implementations.

[0060] 3. Use long packets and fast ACKs on secondary links

[0061] 3.1. ACK timing / ACK link indication in long packets

[0062] Figure 3 An example embodiment 90 is shown for transmitting Ack timing or Ack link in long packet communication. The figure depicts a long packet with a preamble followed by an area for special symbols, which are exemplified as service fields and payload information or block Ack requests (BARs) for fast Ack (Advanced BAR) or checks such as cyclic redundancy check (CRC).

[0063] The following description may be, for example, payload information or advanced BAR passed to the receiver in a long packet. (a) One or more time indicators (e.g., symbol numbers) are given to the receiver indicating the time at which an Ack can be performed on another link before the PPDU is completed. For example, the indicated symbol could be the last symbol carrying the RTA MPDU. (b) Recommended or discouraged link IDs for the Ack may also be provided, such as recommending transmission on a link that is currently busy with Clear Channel Assessment (CCA) on the initiator's side and should not be recommended for transmitting the Ack. (c) Payload information may be the MCS / Nss of the retransmitted MPDU. (d) The payload may include the TID that needs to be reported in the fast Ack, the number of octets of the TID prior to the requested Ack time (including the delimiter). The above information may also be pre-configured so that it does not need to be explicitly indicated in the packet, but is represented by pre-configured identifiers. Figure 3Alternatively, the aforementioned information can be implicitly indicated in the preamble of a long PPDU using a preamble field to signal the preconfiguration identifier. As another alternative, ADD Block Acknowledgment (ADDBA) request and response exchanges can be used to signal the preconfiguration.

[0064] like Figure 3 As shown, the above information, represented as special symbols, can be provided in a symbol following the preamble using the following examples: (a) Some of the above information is carried in some bits of the SERVICE field (e.g., the remaining five bits of the SERVICE field before scrambling), and the remaining information bits are carried in the remainder of the special symbol. (b) The special symbol may include a pre-configured lower MCS with a single spatial stream (SS). For example, using a lower modulation and coding scheme (MCS) provides more protection for the above information than using a subsequent MPDU. The SERVICE currently does not have a Cyclic Redundancy Check (CRC), so a CRC and the following bits for indicating the above information can be added to the SERVICE. The SERVICE and the above information can be contained in a low-density parity-check (LDPC) codeword (CW) with a CW length different from the remainder of the PPDU. The number of special symbols or the MCS and CW configuration of the special symbols can be indicated or pre-configured in the preamble. If a single spatial stream (SS) is used to transmit the special symbol, the channel can be the sum of the multi-stream channels estimated based on the multi-stream training fields in the Ultra High Throughput (EHT) preamble from all SSs.

[0065] 3.2. An indication of an RTA MPDU exists in the ongoing AMPDU.

[0066] The previous section described how the initiator identifies (knows) that no RTA MPDU exists in the AMPDU before sending it, thus assuming that if all MPDUs are delay-tolerant, there is no need to send a fast Ack. Therefore, it may be necessary to communicate to the receiver the presence of an inserted RTA MPDU in the ongoing AMPDU. For example, the receiver may not recognize the presence of an RTA MPDU in the AMPDU if the received RTA MPDU is incorrect.

[0067] This can be addressed in several ways. (a) A special short training field (STF) indicating the start and end of the inserted RTA MPDU / symbol can be received. (b) A field in the MPDU delimiter can indicate the presence of an inserted RTA MPDU before the delimiter. For either (a) or (b), the timing and / or periodicity and / or channel of the fast Ack can be pre-configured. By detecting (a) or (b), the receiver can perform a fast Ack on the next pre-configured opportunity.

[0068] Figure 4Example embodiment 110 is shown, which uses a reserved bit in the MPDU delimiter (non-OMG) set to a first state (e.g., 1) to indicate that a fast Ack is required at the next fast Ack opportunity (if an erroneous MPDU exists); otherwise, a fast Ack can be skipped even if all MPDUs are received (e.g., including low-priority MPDUs). Setting the reserved bit to the first state (e.g., "1") indicates that there is an RTA MPDU preceding the delimiter, and the initiator does not have a receiver fast Ack for these RTA MPDUs. The initiator only needs to change some delimiters (not all) after the RTA MPDU to trigger a fast Ack.

[0069] 3.3. Long groups from the initiator

[0070] 3.3.1. Explicitly confirm the fast Ack on L2 with reTx using EDCA on L1.

[0071] The following describes the use of fast Ack on link 2 (L2) with explicit EDCA acknowledgment for retransmission on link 1 (L1).

[0072] Figure 5 Example 130 of the original AMPDU of link 1 132 is shown, which is shown as having RTA MPDU 134, other STA AMPDU 136, other lower priority traffic identifiers (TIDS) 138 and padding 140.

[0073] Figure 6 Example embodiment 170 is shown, which improves EDCA explicit acknowledgment by using retransmission on L2. Figure 5 130. Communication is represented in links 1-172 and 2-174. (and...) Figure 5 Similarly, see RTA MPDU 134, other STA AMPDU 136 and other low-priority TID 138.

[0074] exist Figure 6 In example 170, the receiver MLD can send a fast ACK on link 2 using EDCA 176 by performing CSMA / CA, which requires an ACK for the fast ACK used to detect collisions. Due to the possibility of collisions and BA 178 initiating TXOP, therefore, with Figure 7 Similar to the deprecated legacy 802.11 process shown, the receiver MLD may require acknowledgment. In this legacy 802.11 process, the delayed BA uses an Ack 180 response to BA 178. It should be noted that BA 178 may include MCS / Nss feedback.

[0075] The initiator can explicitly acknowledge the BA on L2. The initiator is free to place the retransmitted data anywhere in the long packet, such as replacing the original padding or replacing the lower-priority MPDU. The receiver aborts (stops) retrying the BA after receiving the ACK.

[0076] in addition, Figure 6 The example depicts a portion of the padding being replaced by a retransmission of the RTA MPDU. Specifically, the beginning of the padding is shown as being replaced by a short or long training field (S / LTF) 182, followed by a retransmission of the RTA MPDU 184, and then any padding still required 186.

[0077] Figure 7 Example embodiment 210 shows multiple Ack attempts 216 in the delayed block Ack between initiator 212 and receiver 214STA. The setup shows an ADDBA request / response and an Ack, followed by an MPDU, then a BAR from the initiator and an Ack from the receiver. After this, the receiver sends a BA and receives an Ack, which then completes 218 of the processing. Then, a teardown (DELBA) with an associated ACK is seen.

[0078] 3.3.2. Fast Ack on L2 and implicit EDCA acknowledgment and reTx on L1

[0079] The following describes the fast Ack on link 2 (L2) and the implicit EDCA acknowledgment and reTX (retransmission) on link 1 (L1).

[0080] Figure 8 An example embodiment 190 of implicit acknowledgment and retransmission is shown. The acknowledgment of the fast Ack sent on L2 can be observed by looking at the retransmitted MPDU on L1. As shown in the previous figure, the communication on link 1 172 and link 2 174 can be seen, and RTA MPDU 134, other STA MPDU 136 and other low-priority TID 138 are depicted.

[0081] As shown in the diagram above, EDCA 176 is followed by BA 178, but in this case, it is followed by a period "T" 191. "T" is a predefined value for an error tolerance of one OFDM symbol. The actual retransmission can begin with the first symbol on L1 after period T, in which case it is pre-configured by example rather than constraint. In the retransmission, S / LTF 192 is shown, followed by RTA MPDU retransmission 194 and several other low-priority TIDs 196 and 198.

[0082] If there is not enough time to retransmit on the same PPDU after time period T, a retransmission can be performed in a separate PPDU.

[0083] 3.3.3 L2 fast Ack and EDCA implicit / explicit acknowledgments on / L1 with reTx

[0084] The following describes how to perform a fast ACK on link 2 (L2) using implicit or explicit EDCA acknowledgments during retransmissions on link 1 (L1).

[0085] The modified Short Training Field (STF) can signal the start of a retransmission (reTx), and the LTF can follow the receiver's re-estimation of the channel. Repetitions within the STF, such as missing tones, indicate that this is not a data symbol. The STF can be modified to the same length as a data OFDM symbol.

[0086] The MCS / Nss of a retransmitted MPDU can be indicated in the BA (determined by the receiver) or in a special symbol (determined by the initiator).

[0087] If sent in a non-HT format, the Ack frame cannot be used for fast Ack. TA information is not present.

[0088] If the receiver does not detect a retransmission of BA or the start of Ack, the receiver may retry BA.

[0089] The number of data retransmissions or the duration of retransmissions can be derived by the receiver. For example, this can be determined based on the number of symbols in the request Ack, MCS / Nss, and the MPDU bytes (and associated delimiters) that are Acked. If the initiator signals the number of octets of the TID, i.e., the retransmission MCS / Nss, before the Ack time, the receiver can derive the symbols required to retransmit the TID.

[0090] The receiver may need to buffer incomplete LDPC CWs that are interrupted due to retransmission.

[0091] If different MCS new / Nss new For retransmissions, the following applies. The retransmission itself can be an AMPDU (which may not be available). This is because the receiver identifies (becomes aware of) the MCS of the retransmitted data. old and Ns old And the number of bytes, so it can export symbols at the end of retransmission. The MCS / Nss in the following symbols can be restored to the MCS. old and Ns old When restoring new data (lower priority data), if the data is restored to Ns... old If so, then: LTF symbols may follow; or data symbols may follow.

[0092] Assuming the receiver has already cached Ns old The original channel estimation of each spatial stream.

[0093] The last symbol used to carry retransmitted data may contain a portion of the new data that follows (or its delimiter).

[0094] 3.3.4 L2 fast Ack and EDCA implicit / explicit acknowledgments on / L2 w / rxTx

[0095] The following describes the implicit or explicit EDCA acknowledgments in the fast Ack of Link 2 (L2) and retransmissions on Link 2 (L1).

[0096] This section describes an alternative for performing retransmissions on L2. Retransmission behavior on L1 or L2 is indicated in the preamble, either pre-configured or signaled in a special symbol. In this case, retransmitted data is sent on L2 in response to a fast Ack in the same TXOP. The following is an example of performing retransmissions on a backup link.

[0097] Figure 9 This illustrates an example embodiment 230 of downlink (DL) retransmission on an alternative link. The upper part of the diagram depicts link 1 232 and... Figure 5 The same basic transmission is shown, with RTA MPDU 134, other STA MPDU 136, other lower priority traffic 138, and padding 140.

[0098] However, the retransmission operation in this example is performed on link 2 234. EDCA 236 is followed by BA 238 from STA1, and NAV is set to 240. During this time, AP retransmits RTA MPDU 242, and STA1 responds to RTA MPDU 242 with BA 244.

[0099] It should be noted that Figure 9 BA(DL) NAV or Figure 10 The UL length in TF(UL) can be determined using the method described in the previous section.

[0100] If the original PPDU requests multiple fast Acks from the same receiver, the retransmitted PPDU in response to the first fast Ack can be padded to protect the next fast Ack in the same TXOP. In this case, a BA or a multi-STA BA (MBA) is used in response to the retransmitted data, and the second fast Ack can be merged into a single BA. This configuration can disable such padding if other STAs are present that can perform fast Acks. The BA used to obtain the TXOP can also be used for a similar purpose to reverse grant (RDG), allowing the AP to control the remainder of the TXOP to poll a second receiver STA.

[0101] Figure 10 Example embodiment 270 illustrates the fast Ack timing of uplink (UL) data. At the top of the diagram, the AP sends a TF 276. The TF can indicate the fast Ack timing of the UL data determined by the AP, or it can be indicated in a special symbol determined by the STA.

[0102] Trigger 276 triggers a UL transmission from the STA. This communication is shown as having a preamble 277, followed by special symbols 278, RTA MPDUs-1280, and RTA MPDU-2 282, which are then followed by transmissions from other low-priority TIDs 284 and 286, for example, one of these low-priority TIDs 284 and 286 being padded with 286.

[0103] The AP can aggregate fast Ack and UL retransmissions from different users and from different users in a single MU TXOP. This is represented by an EDCA 236 with two BA+TF 238a and 238b, in which the STA performs retransmissions of MPDUs-1240a and MPDUs-2240b, which the AP responds to with an MBA 242.

[0104] 3.3.5. If L2 uses EDCA, then the initiator's behavior is with / o Rx fast Ack.

[0105] If EDCA is used for fast Ack on L2, the fast Ack may be delayed due to Clear Channel Assessment (CCA) being busy, and if the receiver does not receive an acknowledgment of the fast Ack, the receiver will retry the fast Ack. An initiator that does not receive a fast Ack after the indicated symbol may assume the fast Ack was lost but will be retransmitted, or the fast Ack was delayed.

[0106] The initiator seems to have no reason to retransmit the complete data before receiving a quick acknowledgment. For example, if the initiator does not receive a quick acknowledgment, it may choose not to take any action. Based on the initiator's behavior described above, the quick acknowledgment could be a negative acknowledgment (NAK), or the receiver may not need to send a quick acknowledgment if no data is lost.

[0107] Alternatively, in some cases, the receiver may need to send a fast Ack even if no data is lost. In this case, the initiator can clear the retransmission buffer after receiving the fast Ack. L1 still requires a BA after AMPDU. Since the delimiter itself may be faulty and not recognized by the receiver, the above NAK behavior may not apply to delimiter-based Ack requests.

[0108] 4. Long packet transmission from the receiver

[0109] 4.1. Shared Ack Resource Unit (RU) — Example 1

[0110] This section discusses the transmission of long PPDUs by the receiver. If the receiver is an AP, it can allocate a shared Ack RU for performing fast Ack. A shared Ack RU can be, for example, a broadcast RU.

[0111] An MPDU within an AMPDU can be acknowledged before the AMPDU ends. For example, for an MPDU completed in symbols n to d, the Ack status can be returned in symbol n.

[0112] The shared Ack RU on L2 can stream the Ack status of the earlier received data d symbols on L1, such as: (a) inserting the least significant bit (LSB) of the sequence number (SN) and then inserting multiple consecutively received MPDUs after the SN; or (b) inserting CRC every few symbols; or (c) the RU can be special because it contains only a few tones.

[0113] When fast acknowledgment is not performed, the shared Ack RU can also be used to indicate the NAV of another link NAV (e.g., L1 NAV). The L1 NAV can also contain the ID of the TXOP holder on L1. The L1 NAV is the NAV duration of the ongoing PPDU on L1 plus the NAV of the PPDU.

[0114] Figure 11 An example embodiment 310 of a shared Ack RU is shown, in which communication between the STA and its AP is shown via link 1 (L1) 312 and link 2 (L2) 314.

[0115] As shown in the figure, the shared Ack RU on L2 (RUs carrying 318, 324, 326, 332, and 334) can stream the Ack status of earlier received data symbols on L1, such as: (a) inserting the least significant bit (LSB) of the sequence number (SN) and then inserting multiple consecutively received MPDUs after the SN; and / or (b) inserting CRC every few symbols; and / or (c) the RU can be special because it only contains a few tones.

[0116] exist Figure 11 In this context, the shared Ack RU (RUs carrying 318, 324, 326, 332, and 334) can also be used to indicate the NAV of another link NAV (e.g., L1 NAV) when fast acknowledgment is not performed. The L1 NAV can also contain the ID of the TXOP holder on L1. The L1 NAV is the NAV duration of the ongoing PPDU on L1 plus the NAV of the PPDU.

[0117] The AP is shown as having a DL transmission with a preamble 317 and an RU pointing to a different STA. Specifically, DL data is sent to different STAs in 320 and 322, and an RU is shown for Ack and NAV. In this example, STA1 and STA2 on L1 are hidden nodes, and STA2 initiates a TXOP on L1 first with PPDU 316. It should be noted that in PPDU 316, STA1 does not receive from STA2 (STA2 could be an OBSS STA, in which case there is no BA2); STA1's MSDU arrival and BO counter count down to zero; however, STA1 delays channel access because it identifies the L1 NAV from the shared Ack RU on L2. The TXOP initiated on L1 during the duration of the shared RU does not require RTS / CTS for hidden node detection. After preamble 317, padding 318 is indicated, followed by L1 NAV 324. The AP sends BA2 326 to STA2.

[0118] STA 1 observes the shared Ack RU and identifies its delay on L1, while STA 2 (as the initiator) receives the fast Ack 326 of its PPDU and can perform a retransmission (reTx) within the same PPDU or in a new PPDU. A delay of EDCA-based channel access 328 is seen before PPDU 330 from STA 1, and L1 NAV 332 is seen in the RU in the TXOP on L2. The AP responds to STA 1 with BA1 334, and STA 1 can also perform a retransmission if sufficient time remains.

[0119] 4.2. Shared Confirmed Resource Unit (RU) — Example 2

[0120] Shared Ack RU also helps with conflict detection, so conflicting parties can terminate and retry immediately.

[0121] Figure 12 An example embodiment 350 of a second shared Ack RU is shown, illustrating communication between a STA and an AP on link 1 (L1) 312 and link 2 (L2) 314. In this example, the shared RU on L2 lacks an L1 NAV indication of a collision following a transmission by either STA1 or STA2; consequently, both STAs back off.

[0122] Specifically, DL data is sent to different STAs on L2 at 320 and 322, while a RU is shown for Ack and NAV. In this example, a 354 collision occurs between STA1 and STA2 on Link 1, while the RU for Ack on L2 has a padding 352, thus not indicating reception from either. Due to the loss of L1 NAV on L2, STA1 and STA2 detect the collision, therefore STA1 and STA2 have premature termination of transmission and start BO.

[0123] Execute backoff (BO) 356, then STA1 acquires TXOP and sends PPDU 358 to AP on L1, causing RU to represent L1 NAV 360 on L2. AP receives with BA1 362 and then responds with more padding 363 as needed.

[0124] STA2 receives the TXOP on L1 after STA1 and sends PPDU 364, causing its L1 NAV 366 to be in the RU on L2. Since the PPDU from STA2 exceeds the duration of the shared Ack RU, the AP sends the first part of the BA from the L2 RU as BA2a 368. Therefore, the first part of the MPDU is Acked by the shared Ack RU (BA2a) 368, and the remaining part (or all MPDUs) is Acked by the regular BA (BA2b) 370 on L1.

[0125] 4.3. UL Areas with Increased Access Opportunities

[0126] Because of the shared Ack RU on L2 used for transmission on L1, the AP can create a UL area on L1 aligned with the long PPDU / TXOP on L2. Within this UL area, the AP only receives data and increases UL access opportunities by accessing secondary L1 channels, without needing to consider alignment with PPDUs on other channels.

[0127] Figure 13An example embodiment 410 of a UL area for increasing access opportunities is shown. The diagram depicts communication via link 1 between a STA and an AP for ch2 (L1.2) 412, for link 1 ch1 (L1.1) 414, and for link 2 (L2) 416.

[0128] As shown in ch2 422 and ch1 424, the AP on L1 publishes UL Area Announcement 420, which covers area 428 on L1 and has a legacy NAV 426. On L2, there is a DL transmission with preamble 418 and DL, and this DL is executed on multiple RUs 432 and 434, such that another RU contains the Ack and NAV of L1.

[0129] In this example, as shown in the previous diagram, STA1 and STA2 on L1 experience a collision 436 with their preamble. Therefore, the AP does not carry the L1.1 NAV on L2, but instead uses AP Pad 430 with a shared ack RU. Because the L1.1 NAV is lost on L2, STA1 and STA2 detect a collision on L1.1. In this case, STA1 and STA2 abort transmission and initiate a BO. After the BO, STA1 obtains a TXOP of PPDU 440 on the primary ch (L1.1) of link 1; and this prevents STA2 from accessing L1. On L2, an L1.1 NAV 444 is seen after padding 430, which also blocks STA2's access on L1 ch1.

[0130] The AP creates a UL region 428 on L1 aligned with the long L2 DL PPDU. The UL region announcement frame sets the NAV 426 for legacy STAs on L1 to prevent them from accessing L1. EHT STAs that recognize the UL region announcement frame do not need to set the NAV and can still perform access, and can perform parallel access on L1 ch2.

[0131] Since the primary channel is occupied, STA2 uses the secondary channel (L1.2) on L1 to perform EDCA access, resulting in L1.2 NAV 446 being shown in the shared Ack RU on L2. Because the UL area announcement sets the NAV on L1.2, no NAV synchronization (synchronization) delay is required. STA1 and STA2 can be hidden nodes, and STA2 uses the L1.1 NAV broadcast on the shared Ack RU on L2 to determine (know) whether the primary channel is busy. The shared Ack RU streams a fast Ack 448 from the AP for the first part of L1.2 and L1.1. As in this example, when UL PPDU 440 is transmitted on the secondary channel (L1.2), the UL PPDU on the primary channel ch (L1.1) extends beyond UL area 428, the shared Ack RU ends, and the final part of Ack (BA1b) 450 for the final part of PPDU 440 is shown as being transmitted on L1.1.

[0132] 5. Long packets sent from both sides

[0133] 5.1. Example of UL weight L1 + DL weight L2

[0134] Figure 14 Example embodiment 510 of UL heavy L1+DL heavy L2 is shown. This example represents two links with long PPDUs. A shared Ack RU on L2 is shown to provide fast Ack and hidden node protection to L1.

[0135] More specifically, the diagram depicts the communication between the AP and STA on Link 1 (L1) 512 and Link 2 (L2) 514. In this example, the AP sends TF 516 on L1, causing the STA to transmit on L1, and the AP performs a transmission on L2, sending DL data and a communication fast Ack on the RU.

[0136] L1 transmission is displayed as having a preamble 518a, followed by special symbols 520, RTA MPDU-1 524, RTA MPDU-2 526, traffic from other low-priority TIDs 534 and 536, retransmissions of RTA MPDU-1 and RTA MPDU-2 536 and 542, and padding 540 as needed.

[0137] On L2 following the preamble 518b, L1 padding 522 is seen in the fast Ack RU on L2, followed by AP sending BA1+BA2 528 for MPDUs 524 and 526. Later, AP is shown sending BA1 538 for the retransmission of RTA MPDU-1 536. Since the retransmission of RTA MPDU-2 occurs at the end of the TXOP, AP sends Ack 544 for this on L1 after the TXOP as BA2+low-priority MBA.

[0138] 5.2. Example of Ack RU in the UL direction

[0139] Shared Ack RUs can be extended in the UL direction. An AP on L2 can schedule multiple shared Ack RUs for multiple DL-scheduled STA MLDs on L1 for fast Ack. An AP on L2 can schedule a single shared Ack RU for multiple DL-scheduled STA MLDs on L1 for fast Ack by using UL MU-MIMO; or TDM can be used for fast Ack.

[0140] Figure 15 Example embodiment 610 illustrates the use of a TF scheduler on L2 to share the start and / or end times of transmissions on the Ack RU. Both MLD1 and MLD2 on L2 transmit triggered (TB)-PPDU preambles for protection within their network neighborhoods. MLD2 interrupts transmission after the preamble and resumes transmission of the S / LTF at a specified time. The transmission resumed from MLD2 uses power and frequency estimated based on information obtained in the TF.

[0141] More specifically, the diagram depicts communication between the AP and MLD1 and MLD2 on link 1 (L1) 612, and communication between MLD1 and MLD2 and other STAs on link 2 (L2) 614. In this example, the AP transmits TF 616 on L2. STAs begin transmitting on L2, and TXOP transmission also includes a fast Ack RU, while the AP begins transmitting on L1.

[0142] Transmissions on L1 are shown with a preamble 618a, followed by special symbols 622 and RTA MPDU-1 626 to MLD1 and RTA MPDU-2 628 to MLD2. There are also communications from other lower priority TIDs 634 and 636 to MLD1 and MLD2, respectively. The TXOP also contains retransmissions 644 and 648 for RTA MPDU-1 and RTA MPDU-2, along with padding as needed.

[0143] Transmission on L2 is shown with a preamble 618b, followed by UL data 620, 621 and activity on the fast Ack RU, representing S / LTF 624, 638 determined based on the information transmitted in TF 616. Additionally, the AP responds to RTA MPDU-1 with BA1 632 and to RTA MPDU-2 with BA2 640. Filling 630, 642 is also shown in this RU.

[0144] 6. Processing Flow Example

[0145] Figure 16 and Figure 17 Example embodiment 650 illustrates the receiver's processing of a long PPDU requiring an acknowledgment (Ack). On the first link, the initiator sends the long PPDU requiring acknowledgment. On the second link, the receiver sends a fast Ack to the initiator.

[0146] More specifically, in block 652, the receiver begins receiving long PPDUs on the first link. Check 654 determines which preamble or special symbol of the PPDU symbol from a number of options: (1) using fast Ack; (2) using a pre-configured fast Ack configuration; or (3) fast Ack is not required.

[0147] If option (1) is determined, then at block 656, the receiver applies the fast Ack configuration from the special symbol and then proceeds to decision 660, which determines whether all configuration MPDUs up to the configuration point in time on the first link have been received. If the condition is met, then at check 662, it is checked whether fast Ack should optionally be performed on the second link. If the condition is not met, execution returns to check 660; otherwise, execution moves to... Figure 17 Block 664 in the middle.

[0148] Returning to check 660, if the condition is not met, execution will also move to... Figure 17 Block 664 in the middle.

[0149] Taking into account the determination of option (2) from block 654, we arrive at block 658, which applies the pre-configured fast Ack configuration, and then at block 660, which was described earlier.

[0150] Considering that option (3) is determined from block 654, then we arrive at Figure 17 The normal Ack / BA is executed on block 672 of the first link, and then the execution is moved back to block 652.

[0151] exist Figure 17At block 664, a fast Ack is executed on the second link, followed by check 666, which determines whether an Ack or retransmission for the fast Ack has been received. If the condition is not met, execution returns to block 664.

[0152] Otherwise, at block 668, based on the configuration, fast retransmission is received on the first or second link, and then check 670 is reached, which determines whether the PPDU on the first link has been completed. If fast Ack is completed, then at block 672, normal Ack / BA is performed on the first link, and execution returns to block 652. If fast Ack is not completed, execution from... Figure 16 Move from check 670 to check 660.

[0153] Figure 18 and Figure 19 Example embodiment 690 illustrates the initiator's handling of a long PPDU requiring an Ack. At block 692, the initiator begins sending a long PPDU on the first link. At decision 694, it is determined which type of preamble or special symbol to use. Option 1 uses a fast Ack configuration with special symbols, option 2 uses a pre-configured fast Ack configuration, and option 3 does not require a fast Ack.

[0154] If option 1 or option 2 is selected, at block 698, after sending the symbol corresponding to the time point configured for the fast Ack, an arrival check 700 is performed to determine whether a fast Ack has been received. If the condition is not met, execution returns to block 698.

[0155] If the conditions are met, execution is transferred to... Figure 19 In check 702, the initiator determines whether the retransmission should use an implicit ACK to perform a fast ACK. If this condition is not met, at block 706, the initiator performs an ACK for a fast ACK on the second link, and the execution reaches block 704.

[0156] Otherwise, if the conditions of check 702 are met, then at block 704, fast retransmission is performed on the first or second link based on the fast Ack configuration. Execution proceeds to check 708, which determines whether the PPDU for the first link has been completed. If the PPDU has not been completed, execution returns to... Figure 18 Block 698. Otherwise, at block 710, the initiator receives a normal Ack / BA on the first link, causing execution to return to... Figure 18 Block 692.

[0157] consider Figure 18 The other options in block 694, if option 3 is selected, will move directly to... Figure 19 Block 710, which has already been described.

[0158] 7. Frame Format Examples

[0159] Figure 20 Example embodiment 730 illustrates the Fast Ack configuration field. This field represents the configuration example described in the previous section. This field can be included in management frames, such as the ADDBA action frame described in the section on indications of Ack timing / Ack links in long packets. If it is in a frame from initiator to receiver, it represents a pre-configuration of Fast Ack. If it is in a frame from receiver to initiator, it can represent a suggested configuration and / or the ability to perform a specific Fast Ack configuration. If it is included as an element, the presence of the element ID, length, and element ID extension fields is implied and not represented.

[0160] This field can be contained within a pre-configured symbol or location in a long PPDU. Subfields are not bound by this particular order, and there may be presence flags preceding the fields to indicate the presence of a particular field. Fields are described by way of example rather than limitation, and actual implementations may differ, such as those utilizing signaling for similar purposes as described below.

[0161] The Link ID bitmap subfield provides an identifier for a possible second link from which the initiator expects to send a fast Ack. The initiator's transmitter uses this field to indicate possible links receiving fast Acks. The receiver's transmitter uses this field to indicate possible links supporting fast Ack transmission. The initiator's receiver uses this field to identify possible links that the receiver supports for fast Ack transmission. If the receiver is the recipient, it uses this field to determine (know) which links allow fast Ack transmission.

[0162] The t0 start subfield describes the first t0 in a long PPDU, where the unit can be, for example, an OFDM symbol number or the time from which the PPDU begins. The initiating transmitter uses this field to indicate the first t0 in a long PPDU. The receiving receiver uses this field to determine the first t0 in order to perform a fast Ack transmission. This subfield can be omitted if it is sent by the receiving party.

[0163] If multiple t0s exist, the t0 periodicity subfield indicates the duration between two consecutive t0s. These units can be represented in OFDM symbols. The initiating transmitter uses this field to indicate the periodicity of a fast Ack being requested. The receiving receiver uses this field to determine (calculate) subsequent t0s of a fast Ack with a t0 start subfield and a t0 count. Multiple instances of a configured t0 can exist within the duration of a long PPDU transmitted on Link 1. Multiple instances of t0 can follow the periodicity provided in this subfield. If this field is transmitted by the receiving end, it can be omitted.

[0164] If multiple t0s exist, the t0 count subfield indicates the number of t0s. The initiating sender uses this field to indicate the number of requested fast ACKs. If this information is provided, the number must be less than or equal to the number of supported ACKs indicated by the receiver. The receiving receiver uses this field to determine the t0s with a t0 start subfield and a t0 periodicity for subsequent fast ACKs. As indicated in this subfield, multiple instances of configured t0s may exist during the duration of a long PPDU transmitted on Link 1. The receiving sender can use this field to indicate the maximum (most) number of t0s supported per PPDU. The initiating receiver can use this subfield to determine the settings of the subfields sent to the receiving receiver.

[0165] The maximum t2~t1 subfield provides the pre-configured duration. In at least one embodiment, the unit is an OFDM symbol. This field can be set to a reserved value to indicate that the mechanism is not being used. The initiating transmitter uses this field to indicate the pre-configured duration. The receiving receiver uses this field to determine the timeout in which implicit Ack to fast Ack should be received. If this field is sent by the receiver, this subfield can be omitted.

[0166] In at least one embodiment, the receiver (Rx) suggested / required MCS / NSS subfield includes a flag indicating whether the initiator expects the receiver to provide a suggested MCS / NSS. If the flag is set to true (first state), the following two fields (reTx-MCS, reTx-Nss) can be retained or omitted. The initiator's transmitter uses this field to indicate whether the receiver should provide a suggested MCS / Nss or require a fast retransmission MCS / Nss. If the initiator does not want the receiver to suggest or require a fast retransmission MCS / Nss, it should set this subfield to false and indicate whether the retransmission (reTx) MCS / Ns (hereinafter subfield) determined by the NAV of the fast retransmission after the fast Ack on the link that sent the fast Ack, or whether the MCS / Nss was not explicitly signaled during or triggered by the fast retransmission. The receiver uses this field to determine whether it should suggest or require an MCS / Nss for the fast retransmission in the fast Ack. If a fast retransmission follows a fast Ack on the link that sent the fast Ack, the receiver can also use the suggested or required MCS / Nss to determine the NAV. The receiver's transmitter uses this field to indicate whether it supports including the suggested / required MCS / Nss in the fast Ack. The initiator's receiver uses this subfield to determine how to set the same subfield from the initiator to the receiver.

[0167] The retransmission (reTx) MCS subfield indicates the MCS for fast retransmission (or the offset to the original transmitted MCS). The initiating transmitter uses this field to indicate the (minimum) MCS used for fast retransmission or the offset to the long PPDU MCS. If this information is not explicitly indicated in the fast retransmission or its trigger, the receiving receiver uses this field to determine the fast retransmission MCS. If the fast retransmission is followed by a fast Ack on the link that sent the fast Ack, the receiving receiver also uses this subfield to determine the NAV. This subfield can be omitted if it is sent by the receiving end.

[0168] The retransmission (reTx) Nss subfield indicates the Nss of the fast retransmission (or the offset to the original transmitted Nss). The initiating transmitter uses this field to indicate the (minimum) Nss for the fast retransmission or the offset to the long PPDU Nss. If this information is not explicitly indicated in the fast retransmission or its trigger, the receiving receiver uses this subfield to determine the Nss in the fast retransmission. If the fast retransmission follows a fast Ack on the link that sent the fast Ack, the receiving receiver also uses this subfield to determine the NAV. If this field is sent by the receiving receiver, it can be omitted.

[0169] The TID bitmap subfield identifies the TIDs that should be reported in the fast Ack. The sender, if initiating, uses this field to indicate which received TIDs should be included in the fast Ack. The receiver, if receiving, uses this field to determine the set of MPDUs assumed to be included in the acknowledgment frame at t0. This subfield can be omitted if it is sent by the receiver. It can also be omitted if the subfield is included in a management frame (such as an ADDBA request frame) whose scope is limited to a specific TID.

[0170] The On-Demand t0 subfield can be implemented as a flag indicating that t0 is determined, allowing the initiator to use training symbols or delimiters to indicate the presence of an inserted RTA MPDU before or after the indication. A pre-configured t0 can be implicitly replaced by a modified delimiter or inserted training symbol, making t0 "on-demand" t0. If this flag indicates true, the t0 start / cycle / count fields can be omitted or retained. The initiator's transmitter uses this field to indicate the t0 determined by the aforementioned mechanism. The receiver's receiver uses this field to identify whether a pre-configured fast Ack should be applied. If set to true, the pre-configured t0 is dynamically replaced with a signaled t0. The receiver's transmitter indicates whether the receiver supports On-Demand t0. The initiator's receiver uses this field to avoid using the mechanism for receivers that do not support this feature.

[0171] The retransmission (reTx) option on the Fast Ack TXOP subfield indicates that a Fast Retransmission follows the Fast Ack on the link that sent the Fast Ack. This instructs the receiver to allocate NAV within the Fast Ack used for Fast Retransmission. The initiating transmitter uses this subfield to indicate that it will perform a Fast Retransmission after the Fast Ack on the link that sent the Fast Ack. The receiving receiver uses this subfield to determine whether it should retain the TXOP in the Fast Ack so that a Fast Retransmission following the Fast Ack can be performed on the link that sent the Fast Ack. The receiving transmitter uses this field to indicate that it supports retaining the TXOP and receiving a Fast Retransmission following the Fast Ack on the link that sent the Fast Ack. The initiating receiver uses this field to determine whether it should set the same subfield to true if the receiver indicates support.

[0172] Figure 21Example embodiment 750 of a special symbol configuration field is shown. This field can be included in a management frame. If the special symbol configuration field is in a frame sent from the initiator to the receiver, it indicates a pre-configuration of special symbols for a long PPDU requiring a fast ACK. If the special symbol configuration field is in a frame from the receiver to the initiator, it can indicate a suggested configuration and / or the ability to perform a specific configuration. If the special symbol configuration field is included in a frame as a feature, the presence of the feature ID, length, and feature ID extension fields is implicit and not displayed. Subfields are not bound by this particular order, and presence flags indicating the presence of specific fields may precede the fields.

[0173] Because this disclosure considers other configurations, the exemplary special symbol configuration fields are presented by way of example rather than limitation. These configurations may differ, but still provide signaling for a similar purpose to that described below.

[0174] The Special Symbol MCS subfield indicates the MCS of the special OFDM symbol. If the transmitter is the initiator, it sets this field to indicate the MCS used in the special symbol. If the receiver is the receiver, it uses the MCS value indicated in this field to receive the special symbol. If the transmitter is the receiver, it sets this field to indicate the suggested MCS value for the special symbol and / or whether it is capable of receiving a mixed MCS of symbols spanned by a codeword. If the receiver is the initiator, it uses an additional field to determine whether the special symbol can be enabled if supported by the receiver.

[0175] The Special Symbol Nss subfield indicates the Nss of the special OFDM symbol. If the transmitter is the initiator, it sets this field to indicate the Nss used in the special symbol. If the receiver is the receiver, it uses the Nss value indicated in this field to receive the special symbol. If the transmitter is the receiver, it sets this field to indicate a proposed Nss value for the special symbol, and / or it is able to receive a mixed Nss for symbols spanned by a codeword, and / or it is able to use a training field for non-special symbols to estimate the channel for receiving the special symbol. If the receiver is the initiator, it uses this field to determine whether the special symbol can be enabled if supported by the receiver.

[0176] The Special Symbol Duration subfield indicates the duration of a special symbol. In at least one embodiment, the unit value is an OFDM symbol, or the time from the start of the PPDU. Specific values ​​(e.g., 0) are used to indicate that no special symbols are configured or supported. If the transmitter is the initiator, this field is set to indicate the duration of a special symbol in a fixed-size RU / subchannel. The actual duration is scaled inversely by a factor determined by the ratio of the actual bandwidth to the resource unit (BW / RU) size and the fixed size. If the receiver is the receiver, this field is used to determine the duration of the special symbol scaled as described above. If the transmitter is the receiver, it indicates the proposed duration of the special symbol and / or support for the special symbol. If the receiver is the initiator, this field is used to determine the receiver's support for the special symbol and whether the special symbol is enabled.

[0177] Figure 22 Example embodiment 770 shows a fast Ack configuration in a special symbol with the following subfields.

[0178] The Pre-config Override subfield indicates the subsequent presence of a Fast Ack configuration field and a CRC field. It indicates whether a Fast Ack based on a pre-configured one from a previous management frame is missing, or whether a Fast Ack based on the configuration carried in a special symbol used with the PPDU is missing. This field can be a field in the preamble, rather than a field in the special symbol. The sender / initiator uses this field to indicate whether a Fast Ack based on a pre-configured one from a previous management frame is missing, or whether a Fast Ack based on the configuration carried in a special symbol used with the PPDU is missing.

[0179] The receiver / receiver uses this field to determine the presence of the following Fast Ack configuration fields, and the configuration / enabling of Fast Ack.

[0180] The CRC field is determined (calculated) based on the contents of the Fast Ack Configuration field (which may be along with the contents of the Service field). The sender uses this field to transmit the contents of the Fast Ack Configuration field (which may be along with the contents of the Service field). The receiver uses this field to check the contents of the Fast Ack Configuration field (which may be along with the contents of the Service field). If incorrect, the receiver may not perform a Fast Ack, or may perform a Fast Ack indicating that no MPDU was received, or may perform a Fast Ack based on a pre-configured configuration instead of the configuration indicated in the Fast Ack Configuration field.

[0181] Figure 23Example embodiment 790 of a shared Ack configuration element that can be included in a management frame is shown. If it is in a frame from initiator to receiver, it represents the pre-configuration of a shared Ack RU from the AP on the second link in a DL long PPDU. If it is in a frame from receiver to initiator, it can represent a proposed configuration and / or the ability to perform a specific configuration. If included as an element, the presence of the element ID, length, and element ID extension fields is implied and not indicated. Subfields are not restricted to this particular order, and presence flags indicating the presence of specific fields may precede the fields. The fields of this disclosure envision different but still provide similar purposes as described below. The shared Ack configuration field includes the following subfields.

[0182] The Shared Ack AID subfield is used to deduce the STA-ID of the RU that will be used as the Shared Ack RU. The transmitter / AP uses this field to indicate the STA-ID that will be used to allocate the Shared Ack RU in a long PPDU carrying the Shared Ack RU. If the long PPDU is a DL, allocation can be performed via the preamble of the long PPDU. If the long PPDU is a TB-PPDU, allocation can be performed by using a trigger frame. The receiver uses this field to determine the STA-ID, which is used for the Shared Ack RU it should listen for if the RU is in a DL PPDU, or for the Shared Ack RU it should send a fast Ack to if the RU is in a TB-PPDU.

[0183] The Delimiter Modulo subfield (if equal to the value x) indicates the modulus of the delimiter signature for every x octets in the shared Ack RU. The transmitter sets this field to indicate that only sets of octets whose modulus of the value represented by this field is equal to 0 can be used as the starting octets of the delimiter signature. The receiver uses this field to identify that only sets of octets whose modulus of the value represented by this field is equal to 0 can be used as the starting octets of the delimiter signature.

[0184] Figure 24 Example embodiments 810, 830, and 850 of the shared Ack RU element are shown. Three examples of configurations of the octet carried in the shared Ack RU between a delimiter signature field and the next signature field (not shown) are described below: padding 810, fast Ack 830, or LNAV 850. Subfields are not limited to this particular order, and presence flags indicating the presence of a particular field may precede the field. This field is described by way of example and not limitation, and thus this disclosure includes different but still similar embodiments for the purposes described below. These embodiments have the following subfields.

[0185] The delimiter signature subfield contains a special bit pattern indicating that the next field is a length field. The field can only be located at certain octets satisfying the octet modulus described on the previous page.

[0186] The length subfield indicates the length of the field following the length field until the next delimiter signature. The sender uses this field to indicate the number of octets, excluding padding, until the next delimiter signature or the end of transmission. The receiver uses this field to determine the start of padding before the next delimiter signature / end of transmission.

[0187] In the populated shared Ack RU 810, one or more shared Ack link IDs are provided, while the remaining examples 830 and 850 have a link ID subfield and additional subfields.

[0188] The Link ID subfield indicates the identity of the link to which the following LNAV or Fast Ack is applied. If the Link ID is the same as the ID of the link carrying the shared Ack RU, then eight bits up to the next delimiter signature are used as padding. The transmitter uses this field to indicate the Link ID received in the PPDU corresponding to the Fast Ack response, or the Link ID associated with the Link NAV. The receiver uses this field to determine the identity of the Link Fast Ack it is responding to, or the identity of the Link NAV it is associated with.

[0189] The Sub-ch field contains the identity of the 20 / 40 / 80 / 160MHz sub-channel of the Link ID, or the identity of the RU of the Link ID to which the following LNAV or Fast Ack applies. The transmitter sets this field to the identity of the 20 / 40 / 80 / 160MHz sub-channel of the Link ID previously signaled, or the identity of the RU of the Link ID to which the following LNAV or Fast Ack applies. The receiver uses this field to identify the 20 / 40 / 80 / 160MHz sub-channel of the Link ID previously signaled, or the identity of the RU of the Link ID to which the following LNAV or Fast Ack applies.

[0190] The subfield including CRC indicates whether the CRC field exists before the next delimiter signature. The transmitter uses this field to indicate the presence of the CRC field before the next delimiter signature. The receiver uses this field to determine the presence of the CRC field before the next delimiter signature.

[0191] The LNAV / Ack subfield indicates whether the following subfield, preceding the next delimiter signature, is used for either Fast Ack or LNAV. The transmitter uses this subfield to indicate whether the following fields, preceding the next delimiter signature, are used for Fast Ack or LNAV. The receiver uses this field to determine whether the following fields, preceding the next delimiter signature, are used for Fast Ack or LNAV.

[0192] The shared ACK RU for quick Ack configuration in Example 2 also has the following subfields.

[0193] The TID subfield indicates the TID in which the fast Ack is responding. The transmitter uses this field to indicate the TID, as well as the link ID and subchannel ID in which the fast Ack is responding. The receiver uses this field to determine the TID in which the fast Ack is responding, as well as the link ID and subchannel ID.

[0194] The SSN subfield indicates the starting sequence number of the following bitmap of the TID. The transmitter uses this subfield to indicate the starting sequence number of the following bitmap of the TID indicated in the previous subfield. The transmitter uses this subfield to indicate the starting sequence number of the following bitmap of the TID indicated in the previous subfield.

[0195] The bitmap subfield provides a fast Ack bitmap for the TID in the link signaled in the Link ID field and the sub-channel / RU signaled in the Sub-channel subfield. The transmitter uses this field to indicate the fast Ack bitmap for the TID in the link signaled in the Link ID field and the sub-channel / RU signaled in the Sub-channel subfield. The receiver uses this subfield to determine the fast Ack status for the SN represented by the bitmap of the TID in the link signaled in the Link ID field and the sub-channel / RU signaled in the Sub-channel subfield.

[0196] As shown in the figure, the shared ACK RU of the link NAV configuration in Example 3 has the following subfields.

[0197] The AID LSB subfield indicates the AID of the TXOP holder in the link signaled in the Link ID field and the subchannel / RU signaled in the Subchannel subfield. The transmitter uses this field to indicate the AID (or LSB of the AID) of the TXOP holder in the link signaled in the Link ID field and the subchannel / RU signaled in the Subchannel subfield. The receiver uses this field to indicate the AID (or LSB of the AID) of the TXOP holder in the link signaled in the Link ID field and the subchannel / RU signaled in the Subchannel subfield. The receiver can use this information to determine the presence of a hidden node. When the receiver cannot detect its own AID in this field, the receiver can determine whether a PPDU transmission collision has occurred. In response to this detected collision, it can prematurely terminate its transmission on the first link.

[0198] The "Remaining PPDU Duration + NAV" subfield indicates the duration of the remaining PPDU plus the NAV signaled in the PPDU, possibly starting from the previous delimiter. The transmitter uses this subfield to indicate the duration of the remaining PPDU plus the NAV signaled in the PPDU, possibly starting from the previous delimiter. The receiver uses this subfield to determine the duration of the remaining PPDU plus the NAV signaled in the PPDU, possibly starting from the previous delimiter. The receiver can use this subfield to determine the presence of a hidden node.

[0199] Each of these examples may include padding, and examples 2 and 3 may include a CRC subfield.

[0200] The CRC subfield provides the cyclic redundancy check (CRC) for the eight bytes following the CRC field of the last delimiter signature, for which the corresponding included CRC is set to true. The described CRC calculation can exclude any delimiter signature and length field. The transmitter uses this field to indicate the CRC value of the eight bytes following the CRC field of the last delimiter signature with the corresponding included CRC set to true. The receiver uses this field to indicate the CRC value of the eight bytes following the CRC field of the last delimiter signature where the corresponding included CRC is set to true.

[0201] Figure 25 Example embodiment 870 of the trigger frame is shown, which has an additional subfield for fast retransmission allocation within the user information list. The transmitter uses other user information fields of the fast retransmission allocation subfield to indicate the resource allocation for fast retransmission in the requested TB-PPDU. The subfields of this user information list field, including the previous AID12 subfield, may be the same as the HE or EHT variant user information field used for resource allocation immediately following the TB-PPDU. The receiver uses this field to determine the resource allocation for fast retransmission in the requested TB-PPDU. The subfields of this field (including the previous AID12 subfield) may be the same as the HE or EHT variant user information field. The receiver may not find a user information field corresponding to its own AID; in this case, it does not have a fast Ack and does not perform fast retransmission.

[0202] The TID / SSN / Bitmap subfield is the same as the subfield described in the shared Ack RU. The transmitter can indicate the same AID12 as the preceding user information field as the current user information field for carrying a fast Ack (i.e., TID / SSN / Bitmap) corresponding to the non-AP. The receiver can use the same AID12 as the preceding user information field as the current user information field for carrying a fast Ack (i.e., TID / SSN / Bitmap) corresponding to the non-AP.

[0203] Figure 26 Example embodiment 890 of the BA control field is shown, which includes the Fast Retransmit MCS and Nss subfields in previously reserved bits.

[0204] If the Rx suggested / required MCS / NSS flag is set to true from the sender to the receiver, the sender uses this field to indicate the MCS and NSS used for fast retransmission (or the offset to the original MCS / NSS). This field can also indicate whether the indicated retransmission configuration is a requirement or a suggestion from the receiver.

[0205] If fast retransmission is performed within the original Link 1 long PPDU, the receiver establishes its signaled MCS / Nss and the BW / RU size of the long PPDU on Link 1. Alternatively, if fast retransmission is performed after a fast Ack on the same link as the fast Ack, then it is performed on the BW of the fast Ack. If MCS / Nss is required, the initiator must use the indicated MCS / Ns for fast retransmission. If an MCS / Nss is recommended, the initiator can use a different MCS / Vss than the one indicated for fast retransmission, such as a higher MCS / Nss.

[0206] 8. Summary of Invention Elements

[0207] The following is an overview of the features and elements of this disclosure, including various cross-references to interdependencies that refer back to / forward to other elements in this summary (e.g., "x" or "xy", or "xyz"). This summary is not intended to limit the scope of this disclosure, but rather to provide an overview of the elements and relationships.

[0208] 1. The initiating MLD may transmit a long PPDU on the first link. The long PPDU may include one or more AMPDUs sent to one or more receiving MLDs or STAs. In this disclosure, the first link initiator and receiver MLD are abbreviated as initiator or receiver.

[0209] 2. The receiver MLD can perform an ACK by sending an acknowledgment frame on the second link before the transmission of a long PPDU on the first link is complete. This is called a fast ACK. Assume that the first and second links are simultaneous transmit and receive (STR) link pairs for the receiver MLD;

[0210] (a) There may be a time instance t0 associated with a fast ack agreed upon by the initiator and receiver MLD, which corresponds to the set of MPDU X whose reception state is considered to be included in the acknowledgment frame;

[0211] (b) For example, the set X can be restricted to all MPDUs that have been fully sent by the TID group before time t0;

[0212] (c) For example, set X could be all MPDUs that have been fully transmitted before time t0′; and

[0213] (d) The acknowledgment frame can be a BA frame or a multi-STA BA frame.

[0214] 3. The initiating party MLD can execute an ACK on the acknowledgment frame sent on the second link at time t1:

[0215] (a) The receiving MLD can use the lost ack of the acknowledgment to determine whether there is a collision or error in the acknowledgment on the second link;

[0216] (b) An ACK can be sent on the second link as an immediate response to the ACK; and

[0217] (c) t1>t0; due to the channel access delay on the second link, the difference between t1 and t0 may be uncertain; t1 is less than the end time of the long PPDU transmitted on the first link.

[0218] 4. The initiator may, while transmitting a long PPDU as described in Element 1, perform retransmission of lost MPDUs in the MPDU X set described in Element 2.a; this is referred to as fast retransmission:

[0219] (a) If the acknowledgment frame is received by the receiving MLD, the MPDU in the set X that was not reported as successfully received by the receiving MLD in the acknowledgment frame may be retransmitted.

[0220] (b) If the initiator does not receive the acknowledgment frame in element 2, then retransmission may not be performed, or;

[0221] (c) If the initiator does not receive an acknowledgment frame in element 2, and the frame is assumed to have been sent by the receiver using EDCA, then no retransmission may be performed.

[0222] 5. The fast retransmission of the initiating MLD in element 4 can be performed within the same PPDU that it has not yet completed on the first link.

[0223] 6. Fast retransmission in element 4 by the initiator's MLD can occur on a second link (on which the initiator receives acknowledgment frames) or on a third link supported by the receiver's MLD:

[0224] (a) The second or third link is the link to which the TID of the MPDU in set X is mapped;

[0225] (b) The receiver can use the octets of set X and (e.g., subtract) the total number of octets of MPDUs received within set X and the BW / MCS / Nss of fast retransmissions to derive the NAV of the acknowledgment frame transmitted on the second link, which is immediately followed by fast retransmissions on the second link; and

[0226] (c) For example, as an immediate response to a fast ack, a fast retransmission can be performed in the same TXOP as a fast ack in the second link.

[0227] 7. The retransmission in element 5 can begin at time t2, and t2 - t1 <= the pre-configured duration:

[0228] (a) Describe t1 in element 3;

[0229] (b) The initiator may not need to perform an ACK for the acknowledgment frame described in element 3; and

[0230] (c) The receiver MLD uses the retransmission start on the first link as an ack for the acknowledgment frame sent on the second link.

[0231] 8. The retransmission in element 5 can begin at time t2, which is unrelated to t1:

[0232] (a) For example, retransmission may take up time to fill the original long PPDU, which may be a MUPPDU;

[0233] (b) For example, retransmission can begin at time t2, so that the receiver MLD does not need to buffer the interrupted LDPC codeword when receiving the retransmission.

[0234] (c) For example, retransmission can begin at time t2, so that the receiver MLD does not need to buffer the interrupted MPDU when receiving the retransmission; and

[0235] (d) The interruptions in elements 8.b and 8.c are caused by retransmission.

[0236] 9. Retransmissions in element 5 can begin with one or more training symbols:

[0237] (a) At least one training symbol has a pattern that can be distinguished from regular data symbols; and

[0238] (b) Some training symbols can be used by the receiver MLD for new channel estimation.

[0239] 10. Retransmissions in elements 5 and 6 may have different MCS and Nss than the original long PPDU in element 1.

[0240] 11. As an immediate response to the long PPDU in element 1, the receiving MLD may still need to send a BA on the first link.

[0241] 12. If the set of MPDU X described in element 2 is received correctly, the receiving MLD may not send an acknowledgment frame on the secondary link; this is because the initiating MLD behavior described in element 4b or element 4c effectively treats the acknowledgment frame on the secondary link as NAK.

[0242] 13. If the set of MPDU X described in Element 2 is received correctly, the receiving MLD may send an acknowledgment frame on the secondary link; this can help the initiating MLD remove successful MPDUs from its (re)transmission buffer / early transmission window earlier than the positive acknowledgment described in Element 11.

[0243] 14. Fast ACK configuration information can be provided to the receiver before fast ACK; this configuration may include:

[0244] (a) the minimum configuration of fast retransmission (e.g., MCS / Nss / BW) described in element 2 (t0), the identity of the fast ack and fast retransmission link, the TID that the receive state must include in the fast ack, and the pre-configured duration described in element 7; and

[0245] (b) During the duration of a long PPDU sent on link 1, there may be multiple instances of configured t0; multiple instances of t0 may follow the periodicity also provided in the fast ack configuration.

[0246] 15. All or part of the quick ack configuration information can be pre-configured:

[0247] (a) The above pre-configuration can be turned on or off based on the fields in the preamble, or on the first few symbols in the data fields of the long PPDU in Feature 1;

[0248] (b) Prior to data exchange, the ACK configuration can be quickly notified via signaling through the ADDBA request / response mechanism or other management frames; and

[0249] (c) The fast ack configuration may contain differences from the original MCS / Nss / BW.

[0250] 16. All or part of the quick ACK configuration information can be sent using signals within a long PPDU in element 1:

[0251] (a) Signaling can be in the preamble of a long PPDU;

[0252] (b) Signaling may be in the first few symbols of the data field of the AMPDU in the long PPDU, which are represented as special symbols: (1) the special symbols may have a reduced MCS or Nss compared to the rest of the data symbols; (2) the configuration of the special symbols may be signaled via the ADDBA request / response mechanism or other management frames before data exchange.

[0253] 17. Fast retransmit (recommended / required) configurations can be included in the fast ACK; the configurations can include (minimum / maximum) MCS or (minimum / maximum) Nss for fast retransmit; the initiating MLD may not use the recommended configuration for fast retransmit; and the initiating MLD may be required to use the required configuration for fast retransmit.

[0254] 18. The enabling of the fast Ack configuration may not be determined at the start of a long PPDU:

[0255] (a) For example, the MSDU of TID i that requires (pre-configured for) fast ack has not yet reached the MAC layer at the start of the long PPDU; the initiator will not know that fast ack is requested at the beginning of the long PPDU, for example, that fast ack is not enabled in the preamble in element 15.

[0256] (b) The initiator may change the contents of the portion of the AMPDU that has not yet been sent to include the newly arrived MPDU pre-configured for fast Ack with TID i.

[0257] (c) The initiator may set the reserved bit of the delimiter inserted after the MPDU of the newly arrived TID i to "1" to indicate a modified delimiter; (1) the MPDU length field of the delimiter with the reserved bit set to 1 may indicate the total length of the TID (e.g., TIDi) pre-configured for fast ack and sent before the delimiter; (2) more than one such modified delimiter may be inserted after the MPDU of the inserted TIDi to avoid erroneous reception of some delimiters; (3) the appearance of the modified delimiter in the received AMPDU indicates the activation of the pre-configured fast ack configuration; the time of sending the modified delimiter may implicitly replace t0 in the pre-configuration; and (4) the information in (a) may be used to set the NAV of the acknowledgment frame in element 6, which is immediately followed by fast transmission on the second link; the receiver may use the length of the signal notification in element 18.a and (e.g., minus) the length of the corrected received MPDU pre-configured for fast ack and fast retransmission MCS / Nss / BW to determine the NAV; and

[0258] (d) The initiator may insert one or more training symbols as described in element 9 before and / or after the MPDU of the newly arrived TID i; this signals that a fast ack has been enabled: (1) the time when the training symbol is sent may implicitly replace t0 in the pre-configuration; and (2) the number of symbols between the preceding and following training symbols may be used to set the NAV of the acknowledgment frame in element 6 as in element 18.c.(4).

[0259] 19. The receiver sends an acknowledgment on the second link as an immediate response to fast retransmission, as described in element 6c:

[0260] (a) Acknowledgment not only reports the status of retransmissions but can also be used as a second fast ack for a long PPDU in progress on the first link; in this case, the first fast ack, the first fast retransmission, and the second fast ack (plus the ack for the first fast retransmission) are in the same TXOP on the second link; and

[0261] (b) The receiver may delay the transmission of the first fast ack (e.g., wait at EDCA counter 0), or the initiator may fill in fast retransmissions in order to transmit the second fast ack in the same TXOP that satisfies the corresponding t0 requirement in element 14b.

[0262] 20. In element 6c, if the receiver is an AP MLD, then fast ACK can be aggregated / integrated into the trigger frame:

[0263] (a) If the long PPDU on the first link is a TB-PPDU, then the AP can multiplex the fast ack into several non-AP MLDs in the DL OFDMAPPDU, and the PSDU can multiplex the AMPDU containing the fast ack and trigger frame into each non-AP MLD; and

[0264] (b) Fast ACK can be integrated into a trigger frame sent to one or more non-AP STAs and also allocate resources for fast retransmission; (1) ACK bitmap, TID and start sequence number can be in a separate user information field with a special AID or the same AID as the user's AID; the user information field carrying fast ACK can follow the user information field allocated for fast retransmission for non-AP MLDs.

[0265] 21. The preceding bullet points describe a scenario where the initiator sends a long PPDU on the first link, while the fast Ack is sent by the receiver on the second link, and the receiver can be the TXOP holder on the second link.

[0266] Section 22, Motivation and Assumptions, describes a scenario where the initiator sends a PPDU on the first link while a long PPDU is being sent by the receiver on the second link.

[0267] 23. If the receiver is an AP MLD, it can allocate a RU called a shared ack RU in the long PPDU sent by the AP MLD on the second link.

[0268] 24. The fast ACK for the PPDU transmitted in the first link is transmitted in the shared ACK RU; additionally, after successfully receiving the preamble on the first link (when the AP-MLD has not yet received another PPDU on the first link on the same frequency resource), the AP MLD can broadcast the first link NAV (remaining PPDU duration on the first link + PPDU NAV) and the identity of the transmitter of the PPDU transmitted on the first link; and

[0269] (a) Addressing of a shared ack RU can be based on a broadcast AID or on a special AID that is not a non-APMLD and is signaled to the initiator in advance.

[0270] 25. The fast ack information sent in the shared ack RU may be a start sequence number (e.g., LSB only) and may be followed by a bitmap (or the number of consecutively received MPDUs following the start sequence number) and padding, and the pattern may be repeated for the next set of received MPDUs; CRC and / or tail portions may be present with pre-configured periodic insertion.

[0271] (a) The encoding can be BCC, so when the MPDU is received, the state can be encoded and sent immediately on the shared ack RU without codeword delay;

[0272] (b) The MPDU’s fast Ack message can be sent before the MPDU completes its transmission on the first link;

[0273] (c) If all receive states of the PPDU have already been transmitted in the shared ack RU as a fast ack, the AP MLD may not transmit a BA / ack as an immediate response to a PPDU transmitted by a non-AP MLD supporting the shared ack RU; and

[0274] (d) The ack status carried in a fast ack is called a fast ack message.

[0275] 26. There may be a maximum configured delay between the time it takes for the initiator to send the MPDU on the first link and the time it must send the receive status on the shared ack RU if the MPDU is received.

[0276] 27. The NAV and identity information shared on the ack RU can signal to other non-AP MLDs operating on the first link that the first link NAV is busy, in order to avoid any hidden terminal issues on the first link.

[0277] (a) MLDs supporting fast ack in a shared ack RU may not require RTS / CTS; and

[0278] (b) A non-AP MLD can observe that there is no broadcast NAV on the first link in the shared ack RU, inferring that its transmission to the AP on the first link has a collision.

[0279] 28. When a PPDU1 sent from a non-AP MLD on Link 1 overlaps in time with two or more DL PPDUs on a second link in the same TXOP, the shared ack RU on more than one DL PPDU in the second link can carry fast ack information for different MPDUs of PPDU1.

[0280] 29. The AP MLD can transmit one or more long PPDUs on the second link in the same TXOP, each PPDU having a shared ack RU; the AP MLD can transmit control frames UL area announcements in old-fashioned copy format on the channel of the first link; the NAV of the UL area announcement frame overlaps with the duration of one or more long PPDUs in the same TXOP on the second link.

[0281] 30. UL area announcements prevent legacy STAs from accessing the first link during the NAV duration, while non-AP MLDs supporting shared ack RUs on the second link do not set NAVs; in addition to media contention / EDCA on the primary channel of the first link, non-AP MLDs supporting shared ack RUs on the second link can initiate independent media contention / EDCA on the secondary channel of the first link; repeated UL area announcement frames on the secondary channel can allow NAV synchronization without the media synchronization delay for the independent EDCA process on the secondary link;

[0282] (a) By performing multiple EDCA accesses on different channels of the same link, the situation where low-priority users occupying the main channel prevents other high-priority users from accessing the main channel is avoided.

[0283] (b) The AP may require the first link access to not occupy the secondary channel on a certain BW of the PIFS sensing process on the secondary channel during the NAV duration announced in the UL area; for example, within the UL area, the AP may only allow PIFS sensing on the secondary 20MHz channel of the PPDUBW up to 40MHz; the 80MHz BSS bandwidth on the first link may be used as two 40MHz channels with independent access.

[0284] (c) Since the AP always receives on the primary and secondary channels of the first link during the duration of the UL area announcement NAV on the first link, the non-AP MLD that supports shared ack RU on the second link does not need to consider the AP's activity on the other channel of the first link when accessing one channel of the first link.

[0285] 31. On each long PPDU of the same number of independent accesses on the second link used for fast ack or on the first link NAV corresponding to the first link within the UL area, there may be several shared ack RUs.

[0286] (a) There may be a single shared ack RU on the second link, and the shared ack RU multiplexes multiple fast ack / first link NAV corresponding to the number of independent accesses on the first link within the UL area.

[0287] 32. After the UL area ends, the STA on the first link resumes monitoring only for the channel access monitoring main link:

[0288] (a) A PPDU that occupies the primary channel on the first link that begins within the UL area may terminate outside the UL area; a PPDU that does not occupy the primary channel on the first link that begins within the UL area may need to terminate within the UL area.

[0289] 33. The preceding elements describe the following scenarios: (1) a long PPDU is sent from the initiator on the first link while a fast ACK is performed on the second link, or (2) a long PPDU is sent from the AP MLD receiver on the second link, which includes a fast ACK for the PPDU on the first link; in the following elements, long PPDUs sent by the initiator on the first link and long PPDUs sent by the receiver on the second link including a fast ACK are discussed.

[0290] 34. When the initiator is a non-AP MLD on the first link and the receiver is an AP MLD on the second link, the shared ack RU in the front part of the element can also be used for fast ack and first link NAV:

[0291] (a) If the long PPDU on the first link is a TB-PPDU, then similar to element 31, there may be multiple shared ack RUs on the first link for each user, or similar to element 31a, there may be a single shared ack RU on the first link that multiplexes fast acks for multiple users.

[0292] 35. When the initiator is the AP MLD on the first link, rather than the AP MLD, sending a TB-PPDU on the second link:

[0293] (a) For each non-AP MLD addressed by a PPDU on the first link, there may be a corresponding ack RU allocated in the second link for fast acknowledgment of the PPDU on the first link, such as fast acknowledgment being FDM on the second link; the user may be notified by signaling in the preamble of the PPDU on the first link or in the trigger frame preceding the TB-PPDU on the second link of the mapping on the first link and the corresponding ack RU.

[0294] (b) For non-AP MLDs addressed by PPDU on the first link, they can use the same shared ack RU for fast acknowledgment on the second link, such as fast Ack as TDM on the second link; (1) the trigger frame for allocating the shared ack RU before the TB-PPDU can provide the start time, transmission duration, and periodicity corresponding to each user in the DL PPDU on the first link; (2) all non-AP MLDs transmitted on the shared ack RU at different times can transmit a preamble of the TB-PPDU for protection; (3) for non-AP MLDs transmitted on the shared ack RU at different times, it can use the trigger frame to determine the correction of transmission power and center frequency; each user can have an EHT-STF or EHT-LTF from the user before fast ack transmission in the shared ack RU; and

[0295] (c) The trigger frame on the second link may not be sent before the DL PPDU on the first link; if the second link has an EDCA access opportunity earlier than the first link, the DL PPDU may be sent on the second link, while the trigger frame and the TB-PPDU containing the ack RU may be sent on the first link.

[0296] 9. General Scope of the Embodiments

[0297] Here, embodiments of the present technology may be described with reference to flowchart illustrations and / or processes, algorithms, steps, operations, formulas, or other calculation descriptions of methods and systems according to embodiments of the present technology, which may also be implemented as computer program products. In this regard, the blocks or steps of a flowchart and combinations of blocks (and / or steps) in a flowchart, as well as any process, algorithm, step, operation, formula, or calculation description, can be implemented by various means, such as hardware, firmware, and / or software, including one or more computer program instructions embodied in computer-readable program code. It is understood that any such computer program instructions can be executed by one or more computer processors, including but not limited to general-purpose computers or special-purpose computers, or other programmable processing means for production machines, such that the computer program instructions executing on the computer processor or other programmable processing means create means for implementing a specified function.

[0298] Therefore, the blocks of the flowcharts described herein, as well as the descriptions of processes, algorithms, steps, operations, formulas, or calculations, support combinations of means for performing a specified function, combinations of steps for performing a specified function, and computer program instructions, such as those embodied in computer-readable program code logic, for performing a specified function. It should also be understood that the blocks of the flowcharts described herein, as well as any descriptions of processes, algorithms, steps, operations, formulas, or calculations, and combinations thereof, can be implemented by a dedicated hardware-based computer system or a combination of dedicated hardware and computer-readable program code that performs the specified function or steps.

[0299] Furthermore, computer program instructions, such as those embodied in computer-readable program code, may also be stored in one or more computer-readable storage media or memory devices. This computer-readable program code can instruct a computer processor or other programmable processing apparatus to operate in a particular manner, causing the instructions stored in the computer-readable storage media or memory devices to produce an article of manufacture including instruction means that implement the functions specified in the blocks of the flowchart. The computer program instructions may also be executed by a computer processor or other programmable processing apparatus to cause a series of operational steps to be performed on the computer processor or other programmable processing apparatus to produce a computer-implemented process, such that the instructions executing on the computer processor or other programmable processing apparatus provide steps for implementing the functions specified in the blocks, processes, algorithms, steps, operations, formulas, or calculation descriptions of the flowchart.

[0300] It should also be understood that the terms "programming" or "executable program" as used herein refer to one or more instructions that can be executed by one or more computer processors to perform one or more functions described herein. Instructions may be embodied in software, firmware, or a combination of both. Instructions may be stored on non-transitory media local to the device, or may be stored remotely, such as on a server, or all or part of the instructions may be stored both locally and remotely. Remotely stored instructions may be downloaded (pushed) to the device at the user's request, or automatically downloaded based on one or more factors.

[0301] It should also be understood that, as used herein, the terms processor, hardware processor, computer processor, central processing unit (CPU), and computer are used synonymously to refer to a device capable of executing instructions and communicating with input / output interfaces and / or peripheral devices, and the terms processor, hardware processor, computer processor, CPU, and computer are intended to include single or multiple devices, single-core and multi-core devices, and variations thereof.

[0302] As can be understood from the description herein, this disclosure includes various implementations of the technology, including but not limited to the following aspects:

[0303] An apparatus for wireless communication in a network, the apparatus comprising: (a) a wireless communication circuit, acting as a radio station (STA) in a multi-link device (MLD) and as an access point (AP) STA or a non-AP. (a) STA operation for wireless communication with other STAs using a Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) mechanism on a Wireless Local Area Network (WLAN), in which Enhanced Distributed Channel Access (EDCA) is used for random channel access on all links; (b) a processor coupled to the wireless communication circuit for operation on the WLAN; (c) a non-transitory memory storing instructions executable by the processor for communicating with other STAs; and (d) wherein, when executed by the processor, the instructions perform steps of a wireless communication protocol for the wireless communication circuit, including: (d)(i) wherein, on a first link initiating the MLD, a Physical Layer Protocol Data Unit (PPDU) comprising one or more Aggregated MAC Protocol Data Units (AMPDUs) is transmitted; (d)(ii) wherein, before the transmission of the PPDU by the initiator on the first link is completed, the initiator receives an Ack frame as a Fast Acknowledgment (Ack) from the receiving MLD on a second link; and (d)(iii) wherein the first and second links for the initiating MLD and the receiving MLD are a Simultaneous Transmit and Receive (STR) link pair.

[0304] An apparatus for wireless communication in a network, the apparatus comprising: (a) a wireless communication circuit, operating as a radio station (STA) in a multi-link device (MLD) and as an access point (AP) STA or a non-AP STA, for wirelessly communicating with other radio stations (STAs) over a wireless local area network (WLAN) using a carrier sense multiple access / collision avoidance (CSMA / CA) mechanism, wherein enhanced distributed channel access (EDCA) is utilized for random channel access on all links in the WLAN; (b) a processor coupled to the wireless communication circuit for operating on the WLAN; (c) a non-transitory memory storing instructions executable by the processor for communicating with other STAs; and (d) wherein, when executed by the processor, the instructions perform steps of a wireless communication protocol for the wireless communication circuit, including: (d)(i) wherein, on a first link initiating the MLD, transmitting a protocol including one or more aggregated MAC protocols. (d)(ii) wherein, before the initiator has completed the transmission of the long PPDU on the first link, the initiator receives an Ack frame as a fast acknowledgment (Ack) from the receiver MLD on the second link; and (d)(iii) wherein the first and second links for the initiating MLD and the receiver MLD are simultaneous transmit and receive (STR) link pairs; and (d)(iv) wherein the initiating MLD and the receiver MLD agree on a time instance t0 associated with a fast Ack agreed upon by the initiator and the receiver MLD, the fast Ack corresponding to a set X of MPDUs whose reception status is contained in the acknowledgment frame.

[0305] A method for performing wireless communication in a network includes: (a) performing wireless communication in a radio station (STA) of a multi-link device (MLD), wherein the STA operates as an access point (AP) STA or a non-AP STA for wireless communication with other radio stations (STAs) on a wireless local area network (WLAN) using a carrier sense multiple access / collision avoidance (CSMA / CA) mechanism, wherein enhanced distributed channel access (EDCA) is utilized for random channel access on all links in the WLAN; (b) wherein, on a first link initiating the MLD, a long physical layer protocol data unit (PPDU) comprising one or more aggregated MAC protocol data units (AMPDUs) is transmitted; (c) wherein, before the transmission of the long PPDU by the initiator on the first link is completed, the initiator receives an Ack frame as a fast acknowledgment (Ack) from the receiving MLD on a second link; and (d) wherein the first and second links for the initiating MLD and the receiving MLD are simultaneous transmit and receive (STR) link pairs.

[0306] Any of the aforementioned implementations of the apparatus or method, wherein the initiating MLD and the receiving MLD agree on a time instance t0 associated with a fast Ack agreed upon by the initiating and receiving MLDs, the fast Ack corresponding to a set X of MPDUs whose reception status is contained in the acknowledgment frame.

[0307] Any of the aforementioned implementations of the apparatus or method, wherein the set X is limited to all MPDUs that have been fully transmitted for the flow identifier (TID) group before time t0.

[0308] Any apparatus or method implementing the foregoing, wherein the set X is limited to all MPDUs that have been fully transmitted before time t0.

[0309] Any of the aforementioned implementations of the apparatus or method, wherein the acknowledgment frame includes a block acknowledgment (BA) frame or a multi-STA (MU) BA frame.

[0310] As used herein, the term “implementation” is intended to include, but is not limited to, embodiments, examples or other forms of practicing the techniques described herein.

[0311] As used herein, unless the context clearly indicates otherwise, the singular terms “a,” “an,” and “the” may include plural references. Unless explicitly stated otherwise, the singular form of an object referred to does not mean “one and only one,” but rather “one or more.”

[0312] The phrase structures in this disclosure, such as “A, B and / or C”, describe the presence of any A, B, or C, or any combination of items A, B, and C. Phrases listing a set of elements, such as “at least one”, indicate the presence of at least one of these sets of elements, which, where applicable, includes any possible combination of the listed elements.

[0313] References to the terms "embodiment," "at least one embodiment," or similar embodiments in this disclosure indicate that at least one specific embodiment of this disclosure includes a particular feature, structure, or characteristic described in connection with the embodiment. Therefore, these various embodiment phrases do not necessarily refer to the same embodiment or a particular embodiment that differs from all other embodiments being described. The term "embodiment" should be interpreted as meaning that a particular feature, structure, or characteristic of a given embodiment can be combined in any suitable manner in one or more embodiments of the disclosed apparatus, system, or method.

[0314] As used herein, the term "set" refers to a collection of one or more objects. Thus, for example, a set of objects may include a single object or multiple objects.

[0315] Relational terms, such as first and second, top and bottom, upper and lower, and left and right, may be used only to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions.

[0316] The terms “comprising,” “including,” “containing,” “having,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes, contains, or has a list of elements may include not only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, elements beginning with “comprising…,” “including…,” “containing,” or “having…” do not exclude the presence of additional identical elements in a process, method, article, or apparatus that includes, contains, or has elements.

[0317] As used herein, the terms “approximately,” “about,” “substantially,” “essentially,” and “about,” or any other version thereof, are used to describe and indicate minute variations. When used in conjunction with an event or situation, these terms can refer to instances where the event or situation occurred precisely or instances where the event or situation was close to occurring. When used with a numerical value, these terms can refer to a range of variation less than or equal to ±10% of that value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, “substantially” alignment can refer to a range of angular variation less than or equal to ±10°, such as less than or equal to ±5°, less than or equal to ±4°, less than or equal to ±3°, less than or equal to ±2°, less than or equal to ±1°, less than or equal to ±0.5°, less than or equal to ±0.1°, or less than or equal to ±0.05°.

[0318] In addition, quantities, ratios, and other numerical values ​​may sometimes be expressed in range format. It should be understood that such range format is used for convenience and brevity, and should be flexibly interpreted to include values ​​that are explicitly specified as the limits of the range, but also to include all individual values ​​or subranges included within that range, as if each value and subrange were explicitly specified. For example, ratios in the range of approximately 1 to approximately 200 should be understood to include the explicitly stated limits of approximately 1 and approximately 200, but also to include individual ratios such as approximately 2, approximately 3, and approximately 4, and subranges such as approximately 10 to approximately 50 and approximately 20 to approximately 100, etc.

[0319] The term "coupling" as used here is defined as a connection, although it is not necessarily a direct connection or a mechanical connection. A device or structure that is "configured" in a certain way is configured at least in this way, but may also be configured in ways not listed.

[0320] Benefits, advantages, solutions to problems, and any elements that may lead to or make any benefit, advantage, or solution more apparent shall not be construed as key, essential, or fundamental features or elements of the technology described herein or in any or all claims.

[0321] Furthermore, in the foregoing disclosure, various features may be grouped together in various embodiments to streamline the disclosure. The approach of this disclosure should not be construed as reflecting an intention that the claimed embodiments require more features than are expressly stated in the claims. The subject matter of the invention may reside in fewer than all features of a single disclosed embodiment.

[0322] An abstract of this disclosure is provided to allow the reader to quickly determine the nature of the technical disclosure. It should be understood that its submission is not intended to interpret or limit the scope or meaning of the claims.

[0323] It should be understood that some jurisdictional practices may require the removal of one or more portions of the disclosure after the application has been filed. Therefore, readers should consult the application filed for the original content of this disclosure. Any removal of the disclosure should not be construed as a disclaimer, forfeiture, or dedication to the public of any subject matter of the originally filed application.

[0324] The following claims are incorporated herein by reference, such that each claim is independently claimed as a subject matter.

[0325] Although the description herein contains many details, these details should not be construed as limiting the scope of this disclosure, but rather as providing only an illustration of some of the presently preferred embodiments. Therefore, it should be understood that the scope of this disclosure fully encompasses other embodiments that may become apparent to those skilled in the art.

[0326] All structural and functional equivalents of the elements of the disclosed embodiments known to those skilled in the art are expressly incorporated herein by reference and are intended to be covered by the claims. Furthermore, no element, component, or method step in this disclosure is intended for public use, regardless of whether it is expressly stated in the claims. No element should be construed as a "means plus function" element unless expressly stated herein by the phrase "means for…". No element should be construed as a "step plus function" element unless expressly stated herein by the phrase "step for…".

Claims

1. An apparatus for wireless communication in a network, the apparatus comprising: (a) A wireless communication circuit, operating as a radio station (STA) in a multi-link device (MLD) and as an access point (AP) STA or a non-AP STA, for wireless communication with other radio stations (STAs) on a wireless local area network (WLAN) using a carrier sense multiple access / collision avoidance (CSMA / CA) mechanism, in which enhanced distributed channel access (EDCA) is used for random channel access on all links. (b) A processor, coupled to the wireless communication circuit, for operation on a WLAN; (c) Non-transitory memory, storing instructions that can be executed by the processor for communicating with other STAs; as well as (d) wherein the instructions, when executed by the processor, perform the steps of a wireless communication protocol for the wireless communication circuit, including: (i) Wherein, on the first link initiating the MLD, a physical layer protocol data unit (PPDU) including one or more aggregated MAC protocol data units (AMPDU) is sent; (ii) wherein, prior to the completion of the initiator's PPDU transmission on the first link, the initiator receives an Ack frame as a fast acknowledgment (Ack) from the receiver's MLD on the second link; and (iii) wherein the first link and the second link used for the initiating MLD and the receiving MLD are simultaneous transmit and receive (STR) link pairs.

2. The apparatus according to claim 1, wherein, The initiator MLD and the receiver MLD agree on a time instance t0 associated with a fast Ack agreed upon by the initiator and the receiver MLD, which corresponds to a set X of MPDUs whose reception status is contained in the acknowledgment frame.

3. The apparatus according to claim 2, wherein, The set X is restricted to all MPDUs that have been fully sent for the Traffic Identifier (TID) group before time t0.

4. The apparatus according to claim 2, wherein, The set X is restricted to all MPDUs that have been fully sent before time t0.

5. The apparatus according to claim 2, wherein, The acknowledgment frame includes a block acknowledgment (BA) frame or a multi-STA BA (MBA) frame.

6. The apparatus according to claim 1, wherein, The long PPDU is sent by the initiator on the first link, while the fast Ack is sent by the receiver on the second link, and the receiver can be the TXOP holder on the second link.

7. The apparatus according to claim 1, wherein, When there is an ongoing long PPDU being sent by the receiver on the second link, the initiator sends the PPDU on the first link.

8. The apparatus according to claim 7, wherein, If the receiver is an AP MLD, then a resource unit (RU) is allocated as a shared Ack RU in the long PPDU sent by the AP MLD on the second link.

9. The apparatus according to claim 1: in, For PPDUs sent in the first link, fast acks are sent in the shared Ack resource unit (RU); Specifically, after successfully receiving the preamble on the first link, if the AP-MLD has not yet received another PPDU on the same frequency resource on the first link, the AP-MLD broadcasts the first link NAV of the remaining PPDU duration plus the PPDU's NAV, and the PPDU transmitter's identity is transmitted on the first link; and Among them, the addressing of the shared Ack RU can be based on the broadcast AID or on a special AID that is not an APMLD and is notified in advance by signaling.

10. The apparatus according to claim 9: (a) where, The shared NAV and identity information on the Ack RU are used to signal other non-AP MLDs operating on the first link that the first link NAV is busy, in order to avoid any hidden terminal issues on the first link; (b) Wherein, for MLDs supporting fast Ack in a shared Ack RU, RTS / CTS is not required on the first link; and (c) Wherein, the non-AP MLD that transmits on the first link can observe whether there is no first link NAV broadcast in the shared Ack RU, which indicates that its transmission to the AP on the first link has been conflicted.

11. The apparatus according to claim 1: (a) where, AP MLD sends a long PPDU on the second link in the same TXOP, and each long PPDU has a shared Ack resource unit (RU); (b) wherein the AP MLD transmits control frames UL area announcements in the old-fashioned repetitive format on the channel of the first link; and (c) Wherein, the duration of the NAV of the UL area announcement frame overlaps with the duration of the DL-length PPDU in the same TXOP on the second link.

12. The apparatus according to claim 11: (a) where, UL area announcements prevent legacy STAs from accessing the first link during the NAV duration, while non-AP MLDs supporting shared Ack RUs on the second link do not set NAV; (b) In addition to the medium contention / EDCA on the primary channel of the first link, the non-AP MLD that supports shared AckRU on the second link also initiates independent medium contention / EDCA on the secondary channel of the first link. (c) Wherein, by performing multiple EDCA accesses on different channels of the same link, the situation where low-priority users occupying the main channel prevents other high-priority users from accessing the channel is avoided. (d) Wherein, since the AP always receives on the primary and secondary channels of the first link during the duration of the UL area announcement NAV of the first link, the non-AP MLD that supports shared Ack RU does not need to consider the AP's activity on the other channel of the first link when accessing on one channel of the first link.

13. An apparatus for wireless communication in a network, the apparatus comprising: (a) A wireless communication circuit, operating as a radio station (STA) in a multi-link device (MLD) and as an access point (AP) STA or a non-AP STA, for wireless communication with other radio stations (STAs) on a wireless local area network (WLAN) using a carrier sense multiple access / collision avoidance (CSMA / CA) mechanism, in which enhanced distributed channel access (EDCA) is used for random channel access on all links. (b) A processor, coupled to the wireless communication circuit, for operation on a WLAN; (c) Non-transitory memory, storing instructions that can be executed by the processor for communicating with other STAs; as well as (d) wherein the instructions, when executed by the processor, perform the steps of a wireless communication protocol for the wireless communication circuit, including: (i) Wherein, on the first link initiating the MLD, a long physical layer protocol data unit (PPDU) including one or more aggregated MAC protocol data units (AMPDU) is sent; (ii) wherein, prior to the completion of the transmission of the long PPDU by the initiator on the first link, the initiator receives an Ack frame as a fast acknowledgment (Ack) from the receiver's MLD on the second link; and (iii) wherein the first and second links used for the initiating MLD and the receiving MLD are simultaneous transmit and receive (STR) link pairs; and (iv) wherein the initiator MLD and the receiver MLD agree on a time instance t0 associated with a fast Ack agreed upon by the initiator and the receiver MLD, the fast Ack corresponding to a set X of MPDUs in which the reception status is contained in the acknowledgment frame.

14. The apparatus according to claim 13, wherein, The set X is restricted to all MPDUs that have been fully sent for the Traffic Identifier (TID) group before time t0.

15. The apparatus according to claim 13, wherein, The set X is restricted to all MPDUs that have been fully sent before time t0.

16. The apparatus according to claim 13, wherein, The acknowledgment frame includes a block acknowledgment (BA) frame or a multi-STA (MU) BA frame.

17. A method for performing wireless communication in a network, comprising: (a) Performing wireless communication in a radio station (STA) of a multi-link device (MLD), wherein the STA operates as an access point (AP) STA or a non-AP STA for wireless communication with other radio stations (STAs) on a wireless local area network (WLAN) using a carrier sense multiple access / collision avoidance (CSMA / CA) mechanism, wherein enhanced distributed channel access (EDCA) is used for random channel access on all links. (b) Wherein, on the first link initiating the MLD, a long physical layer protocol data unit (PPDU) including one or more aggregated MAC protocol data units (AMPDU) is sent; (c) Wherein, before the initiator has completed sending the long PPDU on the first link, the initiator receives an Ack frame as a fast acknowledgment (Ack) from the receiver MLD on the second link; and (d) Wherein, the first link and the second link used for the initiating MLD and the receiving MLD are simultaneous transmit and receive (STR) link pairs.

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