Operating conditions for trigger-based uplink transmissions in EMLSR or EMLMR common accessory stations

Abstract

The non-AP MLD operates on multiple links using the UL TID to link mapping. When the EML mode is activated, the non-AP MLD selects an EML link set of the EML links to which the EML mode is applied according to the UL TID-to-link mapping, and transmits a notification to the AP MLD specifying the selected EML link set. Further, or as an alternative, when the non-AP MLD is operating in an EML mode having an EML link set, the non-AP MLD transmits a BSR frame to the AP MLD on a first EML link in the EML link set, in response to a BSRP TF received from the AP MLD on the first EML link, reporting buffered traffic according to the UL TID to link mapping.

Description

Technical Field

[0001] The present invention relates generally to wireless communications and, more particularly, to multi-link (ML) communications. Background Art

[0002] Wireless communication networks are widely deployed to provide various communication services, such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple access networks include code division multiple access (CDMA) networks, time division multiple access (TDMA) networks, frequency division multiple access (FDMA) networks, orthogonal FDMA (OFDMA) networks, and single carrier FDMA (SC-FDMA) networks.

[0003] The 802.11 family of standards adopted by the Institute of Electrical and Electronics Engineers (IEEE-RTM) provides a number of mechanisms for wireless communications between STAs.

[0004] With the development of latency-sensitive applications (such as online games, real-time video streaming, virtual reality, remote control of drones or robots), better throughput, low latency and robustness requirements and issues need to be considered. Currently, the IEEE802.11 working group is considering this problematic issue as the main goal of releasing the next major 802.11 version (called 802.11be or "extremely high throughput" EHT).

[0005] IEEE P802.11be / D2.0 version (May 2022, under the "D2.0 standard") introduces multi-link (ML) operation (MLO). MLO improves data throughput by allowing STAs to communicate on multiple concurrent and non-continuous communication links.

[0006] MLO enables non-AP (Access Point) MLDs (ML Devices) to register with AP MLDs, i.e., discover, authenticate, associate, and set up multiple links with AP MLDs. Each link enables channel access and frame exchange between non-AP MLDs and AP MLDs based on the supported capabilities exchanged during the association process.

[0007] MLD is a logical entity with more than one subordinate station (STA) and a single medium access control (MAC) service access point (SAP) for a logical link control (LLC), which includes one MAC data service. Therefore, an AP MLD consists of multiple subordinate APs, while a non-AP MLD consists of multiple subordinate non-AP STAs. The subordinate STAs in both AP MLD and non-AP-MLD can communicate with the subordinate STAs of another MLD through each of the multiple communication links set up using the 802.11 mechanism.

[0008] With the introduction of MLO and the spatial multiplexing capability of MLD, new operation modes (OMs) called enhanced multi-link operation modes (EML OMs) are introduced in the D2.0 standard, namely EMLSR (Enhanced Multi-Link Single Radio) mode and EMLMR (Enhanced Multi-Link Multi-Radio) mode.

[0009] Non-AP MLDs declare their support for the EML mode of operation (called EML capability) to the AP MLD during the association phase. In the operational mode, activation and deactivation of the EML mode of operation is initiated by the non-AP MLD sending a specific EHT action frame called "EML OM Notification". The D2.0 standard states that the two EMLSR and EMLMR modes are mutually exclusive.

[0010] Once the EMLMR mode is activated, it allows non-AP MLDs to simultaneously listen to a set of enabled links (so-called EMLMR links, usually consisting of two enabled links) to receive an initial frame transmitted by the AP MLD to initiate frame exchange, and then aggregate some physical resources of different radios used on different links (so-called EMLMR links) so that data up to a predefined number of supported Rx / Tx spatial streams are transmitted or received on only one EMLMR link (usually the link on which the initial frame is received) at a time. This number can be greater than the number of supported Rx / Tx spatial streams of each radio. The frame exchange sequence initiated by the AP MLD can be a trigger (TB)-based downlink (DL) transmission or a trigger (TB)-based uplink (UL) transmission on the link on which the initial frame is received.

[0011] Once the EMLSR mode is activated, the non-AP MLD is allowed to simultaneously listen to a set of enabled links (so-called EMLSR links, usually consisting of two enabled links) to receive an initial control frame (e.g., MU-RTS trigger frame, BSRP trigger frame) from the AP MLD to initiate frame exchange, and then perform data frame exchange with the AP MLD on only one EMLSR link at a time (usually the link via which the initial control frame is received). The frame exchange sequence initiated by the AP MLD can be a trigger-based (TB) downlink (DL) transmission or a trigger-based (TB) uplink (UL) transmission on the link where the initial control frame is received.

[0012] With the introduction of MLO, the D2.0 standard also defines a traffic identifier (TID) to link mapping mechanism. This mechanism allows the AP MLD and the non-AP MLD that have or are performing multi-link setup to determine how to assign UL and DL QoS traffic corresponding to TID values ​​between 0 and 7 to the setup links of the non-AP MLD. By default, all TIDs are mapped to all setup links for both DL and UL, and all setup links are enabled. The D2.0 standard defines a process that allows TID to link mapping negotiation in the DL and / or UL direction between the initiating MLD and the responding MLD.

[0013] In an EMLMR or EMLSR frame exchange operation initiated by an AP MLD as currently specified in IEEE P802.11be / D2.0, the selection of an EMLMR or EMLSR link for a frame exchange sequence is driven by the AP MLD when sending an initial frame or an initial control frame. Currently, the standard does not specify any rules for matching the selected EMLMR link or EMLSR link with the TID to link mapping used between the AP MLD and the non-AP MLD. In some cases, especially for TB UL traffic, the lack of such rules may lead to some mismatches and inefficiencies. For example, a TB UL transmission opportunity may be provided by the AP MLD to a non-AP MLD on an EMLMR or EMLSR link on which there is no mapped TID or no TID currently buffered by the non-AP MLD. This results in a loss of a TB UL transmission opportunity, while a non-AP MLD in a frame exchange state on the relevant EMLMR or EMLSR link also loses any opportunity to transmit on one or more other EMLMR or EMLSR links. Summary of the invention

[0014] A broad object of the present invention is to coordinate EML mode operation (EMLMR or EMLSR) with uplink TID-to-link mapping for trigger-based (TB) uplink traffic (UL) transmission.

[0015] In this context, an embodiment of the present invention provides a communication method in a wireless network, comprising: at a non-access point (non-AP) multi-link device (MLD) operating on multiple links using uplink (UL) traffic identifier (TID) to link mapping, performing one of the following operations:

[0016] - activating an enhanced multi-link (EML) mode, wherein activating the EML mode comprises: selecting an EML link set of EML links to which the EML mode is applied according to the UL TID-to-link mapping, and transmitting a notification specifying the selected EML link set to the AP MLD; and / or

[0017] -When the non-AP MLD operates in the EML mode with the EML link set, in response to a buffer status report poll (BSRP) trigger frame received from the AP MLD on a first EML link in the EML link set, transmitting a BSR frame to the AP MLD on the first EML link, the BSR frame reporting buffered traffic according to the UL TID-to-link mapping.

[0018] By considering TID to link mapping in the setup of EML links for EML mode and / or in the BSR, the present invention can ensure that the EML link used by the AP MLD to trigger frame exchange is suitable for TB UL communication for non-AP MLD. This allows avoiding or reducing the aforementioned mismatch and inefficiency between EML mode operation and UL TID to link mapping for TB UL traffic transmission.

[0019] More generally, considering TID-to-link mapping in the setup of links can also be applied to multi-link mode, regardless of any EML mode. Therefore, a more general embodiment of the present invention provides a communication method in a wireless network, comprising: at a non-AP MLD operating on multiple links using UL TID-to-link mapping: when the non-AP MLD operates in multi-link mode with a link set, in response to a BSRP trigger frame received from the AP MLD on a first link in the link set, transmitting to the AP MLD on the first link a BSR frame reporting buffered traffic according to the UL TID-to-link mapping. In some embodiments according to the more general method, the BSR frame reports buffered traffic (if any) of at least one UL TID mapped on the first link according to the UL TID-to-link mapping. In some other embodiments, the BSR frame only reports buffered traffic (if any) of one or more UL TIDs mapped on the first link according to the UL TID-to-link mapping.

[0020] Optional features of embodiments of the invention are defined below with reference to methods, whereas these features may be converted into apparatus features.

[0021] In some embodiments, selecting the EML link set according to the UL TID-to-link mapping includes satisfying a constraint that at least one EML link in the EML link set should have at least one UL TID mapped according to the UL TID-to-link mapping.

[0022] This feature avoids having a set of EML links on which no UL TID is mapped according to the UL TID to link mapping and the AP MLD tends to trigger the non-AP MLD on the links in the set of EML links for UL transmission. Thus, the loss of such TB UL transmission is avoided. This feature (and its constraints) is preferably applied when the UL TID to link mapping is a negotiated UL TID to link mapping with the TID to link mapping negotiation support subfield value equal to 1.

[0023] In some embodiments, selecting the EML link set according to the UL TID to link mapping includes satisfying a constraint that the EML link set should not be disjoint from another link set in which all UL TIDs are mapped on respective links according to the UL TID to link mapping.

[0024] In other words, for these embodiments, at least one EML link in the EML link set should be included in another link set on which all UL TIDs are mapped according to the UL TID to link mapping. This feature also allows avoiding the situation where the EML link set has no UL TID mapped thereon according to the UL TID to link mapping and the AP MLD tends to trigger the non-AP MLD on the links in the EML link set for UL transmission. This feature (and its constraints) is preferably applied in the case where the UL TID to link mapping is a negotiated UL TID to link mapping with the TID to link mapping negotiation support subfield value equal to 2.

[0025] In some embodiments, the BSR frame reports buffered traffic (if any) for at least one UL TID mapped on the first EML link according to the UL TID-to-link mapping.

[0026] This feature also allows avoiding the situation where the BSR response frame sent by the non-AP MLD reports all buffered traffic for TIDs that are not mapped on the first link receiving the BSRP TF. In fact, in this case, triggering the non-AP MLD on the first link for UL transmission by the AP MLD is useless and the overall EML operation initiated is inefficient.

[0027] In some embodiments, the BSR frame reports only buffered traffic (if any) for one or more UL TIDs mapped on the first EML link according to the UL TID-to-link mapping.

[0028] This feature ensures that the non-AP MLD can utilize any TB UL transmission scheduled by the AP MLD on the first link based on the BSR.

[0029] In case the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with the TID-to-link mapping negotiation support subfield value equal to 1, this feature and the previous features (and their corresponding constraints) are preferably applied.

[0030] In some embodiments, the BSRP trigger frame is an initial frame that triggers a frame exchange sequence on the first EML link, and the method further comprises at the non-AP station:

[0031] - obtaining scheduled UL resources within the frame exchange sequence; and

[0032] - transmitting within the scheduled UL resources data having a UL TID mapped on the first EML link according to the UL TID to link mapping as reported in the BSR frame.

[0033] Therefore, the non-AP MLD can transmit data without a mismatch between EML mode operation and uplink TID-to-link mapping for TB UL traffic transmission.

[0034] The initial frame that triggers the frame exchange sequence is called an "initial frame" in EMLMR mode and is called an "initial control frame" in EMLSR mode.

[0035] In some embodiments, the method further comprises: transmitting, at the non-AP MLD, to the AP MLD, signaling information indicating which of the following two sub-modes of the EML mode is to be used:

[0036] - a first sub-mode of the EML mode, the first sub-mode comprising the transmission of the BSR frame reporting buffered traffic according to the UL TID to link mapping; and

[0037] - a second sub-mode of the EML mode, in which the non-AP MLD transmits a BSR frame to the AP MLD on the first EML link in response to a BSRP trigger frame received from the AP MLD on the first EML link, the BSR frame indicating a selected EML link in the EML link set to be used for frame exchange.

[0038] Therefore, the non-AP MLD explicitly signals which of the two sub-modes of the EML mode it uses. Hereinafter, the first and second sub-modes of the EML mode are also referred to as "current EML operation for TB UL traffic" and "new EML operation for TB UL traffic", respectively.

[0039] An embodiment of the present invention also provides a communication method in a wireless network, comprising: at a non-access point (non-AP) multi-link device (MLD) operating on multiple links using uplink (UL) traffic identifier (TID) to link mapping,

[0040] - receiving a buffer status report poll (BSRP) trigger frame from the AP MLD on a first EML link in the EML link set to which the EML mode is applied;

[0041] - selecting an EML link to be used for frame exchange in the EML link set according to the UL TID to link mapping and the buffered traffic to be reported in the BSR frame; and

[0042] - transmitting the BSR frame indicating the selected EML link to be used for the frame exchange to the AP MLD over the first EML link.

[0043] Therefore, an innovative solution is proposed in non-AP MLD, which relies on transmitting a BSR frame for indicating the selected EML link to be used for frame exchange, the selected link being selected according to the UL TID to link mapping and the buffered traffic to be reported in the BSR frame. Due to the fact that the UL TID to link mapping is taken into account, the innovative solution allows avoiding or reducing the aforementioned mismatch and inefficiency between EML mode operation and UL TID to link mapping for TB UL traffic transmission.

[0044] In some embodiments, the selected EML link is a second EML link in the set of EML links that is different from the first EML link on which the BSRP trigger frame is received and the BSR frame is transmitted.

[0045] In some embodiments, the method further includes: at the non-AP MLD, after transmission of the BSR frame, switching a first STA attached to the non-AP MLD and corresponding to the selected EML link from a listening operation state or a disabled frame exchange state to an enabled frame exchange state.

[0046] In some embodiments, the method further includes: at the non-AP MLD, on the second EML link different from the first EML link, before receiving a basic trigger frame for scheduling UL resources to the non-AP MLD within a frame exchange sequence, receiving an initial frame for triggering the frame exchange sequence on the second EML link, wherein the BSRP trigger frame is received on the first EML link.

[0047] Therefore, the non-AP MLD can transmit data without a mismatch between EML mode operation and uplink TID-to-link mapping for TB UL traffic transmission.

[0048] In some embodiments, the method further comprises: at the non-AP MLD, selecting the EML link set based on the UL TID-to-link mapping, and transmitting a notification specifying the selected EML link set to the AP MLD.

[0049] Therefore, in non-AP MLD, transmission of a BSR frame for indicating a selected EML link to be used for frame exchange may be combined with consideration of TID-to-link mapping in the setup of the EML link for the EML mode.

[0050] In some embodiments, the method further comprises: transmitting, at the non-AP MLD, to the AP MLD, signaling information indicating which of the following two sub-modes of the EML mode is to be used:

[0051] - a first sub-mode of the EML mode, in which, in response to a BSRP trigger frame received from the AP MLD on a given EML link in the set of EML links, the non-AP MLD transmits a BSR frame to the AP MLD on the given EML link, the BSR frame reporting buffered traffic (if any) of at least one UL TID mapped on the given EML link according to the UL TID-to-link mapping; and

[0052] - a second sub-mode of said EML mode, said second sub-mode comprising said transmission of said BSR frame indicating said selected EML link to be used for said frame exchange.

[0053] Therefore, and as described above, the non-AP MLD may signal its selection between the aforementioned two sub-modes of the EML mode.

[0054] In some embodiments, the signaling information is contained in a subfield of an EML control field of an EML operation mode (OM) notification frame transmitted by the non-AP MLD.

[0055] An embodiment of the present invention also provides a communication method in a wireless network, comprising: at an AP MLD configured to perform a frame exchange operation with at least one non-access point (non-AP) multi-link device (MLD) operating on a multi-link using an uplink (UL) traffic identifier (TID) to link mapping,

[0056] - transmitting a Buffer Status Report Poll (BSRP) Trigger Frame (TF) to the non-AP MLD on a first enabling link;

[0057] - receiving a BSR frame reporting buffered traffic from the non-AP MLD on the first enabling link; and

[0058] - transmitting a basic TF to the non-AP MLD over the first enabling link, the basic TF scheduling UL resources to the non-AP MLD and containing constraints on data to be transmitted within the scheduled UL resources based on the UL TID to link mapping.

[0059] Therefore, an innovative solution is proposed in AP MLD, which relies on the basic TF for scheduling UL resources to non-AP MLD transmissions and contains constraints on the data to be transmitted within the scheduled UL resources based on UL TID to link mapping. Therefore, the UL TID to link mapping is taken into account to provide TB UL transmission suitable for non-AP MLD, thus also allowing to avoid or reduce the aforementioned mismatch and inefficiency between the multi-link operation mode and the UL TID to link mapping for TB UL traffic transmission. When the multi-link operation mode is EML mode (EMLSR mode or EMLMR mode), the innovative solution is particularly but not exclusively applied; in this case, the first enabling link is also an EML link.

[0060] In some embodiments, the constraints on data to be transmitted within the scheduled UL resources are indicated by a value of an access category, AC, corresponding to a UL TID mapped on the first enabling link according to the UL TID to link mapping.

[0061] In some embodiments, the value is indicated in a preferred AC subfield of a trigger-related user information field of a user information field corresponding to the scheduled UL resources within the basic TF.

[0062] In some embodiments, in a case where the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with a TID-to-link mapping negotiation support subfield value equal to 1, constraints on data to be transmitted by the non-AP MLD apply.

[0063] In some embodiments, at least one UL TID is mapped on the first enabled link transmitting the BSRP TF according to the UL TID to link mapping.

[0064] This feature (regarding the link used to transmit BSRP TF) also takes into account UL TID to link mapping to provide TB UL transmission suitable for non-AP MLD, thereby also allowing the aforementioned mismatch and inefficiency between multi-link operation mode and UL TID to link mapping for TB UL traffic transmission to be avoided or reduced.

[0065] The present invention also provides a communication method in a wireless network, comprising: at an AP MLD configured to perform a frame exchange operation with at least one non-access point (non-AP) multi-link device (MLD) operating on a multi-link using an uplink (UL) traffic identifier (TID) to link mapping,

[0066] - transmitting a Buffer Status Report Poll (BSRP) Trigger Frame (TF) to the non-AP MLD on a first enabled link mapped with at least one UL TID according to the UL TID to link mapping.

[0067] In other words, the features regarding the link used to transmit the BSRP TF (the link on which at least one UL TID is mapped) can be implemented independently of the previous features (the basic TF containing the constraints on the data to be transmitted within the scheduled UL resources based on the UL TID to link mapping). The innovative solution is particularly, but not exclusively, applied when the multi-link operation mode is the EML mode (EMLSR mode or EMLMR mode); in this case, the first enabling link is also the EML link. In fact, in this case, the BSRP TF is the initial frame and the frame exchange will occur on the first enabling link (EML link).

[0068] In some embodiments, the method further comprises: transmitting, at the AP MLD, to the non-AP MLD, signaling information indicating which of the following two sub-modes of the EML mode is to be used:

[0069] - a first sub-mode of the EML mode, the first sub-mode comprising the transmission of the basic TF, the basic TF scheduling the UL resources to the non-AP MLD and containing constraints on data to be transmitted within the scheduled UL resources based on the UL TID-to-link mapping; and

[0070] - a second sub-mode of the EML mode, in which the AP MLD retrieves an indication of a selected EML link to be used for frame exchange from the BSR frame, and transmits a basic TF to the non-AP MLD on the selected EML link to trigger an uplink frame exchange with the non-AP MLD on the selected EML link.

[0071] Therefore, the AP MLD may signal the selection between the aforementioned two sub-modes of the EML mode.

[0072] An embodiment of the present invention also provides a communication method in a wireless network, comprising: at an AP MLD configured to perform a frame exchange operation with at least one non-access point (non-AP) multi-link device (MLD) operating on a multi-link using an uplink (UL) traffic identifier (TID) to link mapping,

[0073] - receiving, from the non-AP MLD on a first EML link in a set of EML links, a BSR frame in response to a buffer status report poll (BSRP) trigger frame (TF) transmitted on the first EML link;

[0074] - retrieving from said BSR frame an indication of a selected one of the EML links to be used for frame exchange; and

[0075] - transmitting a basic TF to the non-AP MLD over the selected EML link to trigger an uplink frame exchange with the non-AP MLD over the selected EML link.

[0076] Therefore, an innovative solution is proposed in AP MLD, which relies on retrieving the indication of the selected EML link to be used for frame exchange from the BSR frame sent by the non-AP MLD. Therefore, the UL TID to link mapping is also taken into account indirectly, thus also allowing to avoid or reduce the aforementioned mismatch and inefficiency between EML mode operation and UL TID to link mapping for TB UL traffic transmission.

[0077] According to the features shared by non-AP MLD and AP MLD, the selected EML link is implicit in the TID or TIDs reported in the BSR frame in view of the UL TID to link mapping. This saves signaling cost in exchanging frames.

[0078] According to the characteristics shared by the non-AP MLD and the AP MLD, one or more reported TIDs are mapped on a second EML link in the EML link set instead of the first EML link. Therefore, there is implicit and explicit signaling that the non-AP MLD needs to perform frame exchange on the second link (although the BSRP / BSR exchange is performed on the first link).

[0079] According to a feature shared by non-AP MLD and AP MLD: under negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1, if the reported TID is mapped on the same EML link, the selected EML link to be used for frame exchange is the same EML link.

[0080] This configuration resolves any ambiguity in reporting several TIDs mapped on several EML links.

[0081] According to a feature shared by the non-AP MLD and the AP MLD: under the default TID-to-link mapping or under the negotiated TID-to-link mapping with the TID-to-link mapping negotiation support subfield value = 2, the selected EML link to be used for frame exchange is the first EML link, wherein the BSRP trigger frame and the BSR frame are transmitted or received on the first EML link.

[0082] This also removes any ambiguity when the reported TID does not allow identification of a single EML link.

[0083] Of course, instead of selecting the first link to disambiguate, the second link may be selected.

[0084] According to a feature shared by the non-AP MLD and the AP MLD: under the negotiated TID-to-link mapping with a TID-to-link mapping negotiation support subfield value=1, if at least two reported TIDs are mapped to at least two different EML links, the selected EML link to be used for frame exchange is the first EML link, wherein the BSRP trigger frame and the BSR frame are transmitted or received on the first EML link.

[0085] This again removes any ambiguity in case the reported TID does not allow identification of a single EML link.Instead of selecting the first link to remove the ambiguity, the second link may be selected.

[0086] According to the characteristics shared by non-AP MLD and AP MLD, the selected EML link is explicitly indicated by the link identifier in the BSR frame.

[0087] This allows simplifying the processing in the AP MLD.

[0088] According to the characteristics shared by non-AP MLDs and AP MLDs, the initial frame contains an invitation to other non-AP MLDs to be triggered in the upcoming UL EML frame exchange on the second EML link.

[0089] This allows triggering some other EML active non-AP MLD in the upcoming UL EML frame exchange on the second EML link. "Other" may mean different from the non-AP MLD that has been triggered by the BSRP frame.

[0090] According to the characteristics shared by non-AP MLD and AP MLD, the initial frame is a multi-user request to send (MU-RTS) frame.

[0091] Since the MU-RTS / CTS procedure uses basic frames that can be decoded by legacy stations, it allows the second EML link to be protected before the upcoming ULEML frame exchange.

[0092] In some embodiments, the method further comprises: transmitting, at the AP MLD, to the non-AP MLD, signaling information indicating which of the following two sub-modes of the EML mode is to be used:

[0093] - a first sub-mode of the EML mode, the first sub-mode comprising transmission of a basic TF, the basic TF scheduling UL resources to the non-AP MLD and containing constraints on data to be transmitted within the scheduled UL resources based on the UL TID-to-link mapping; and

[0094] - A second sub-mode of the EML mode, in which the AP MLD performs the retrieval of an indication of the selected EML link to be used for frame exchange from the BSR frame, and the transmission of a basic TF to the non-AP MLD on the selected EML link for triggering an uplink frame exchange with the non-AP MLD on the selected EML link.

[0095] Therefore, and as described above, the AP MLD may signal its selection between the above two sub-modes of the EML mode.

[0096] In some embodiments, the signaling information is contained in a subfield of a common information field within the BSRP TF transmitted by the AP MLD or in a subfield of a user information field assigned to the non-AP MLD.

[0097] A method of communication in a wireless network is also provided, comprising: at an access point (AP) multi-link device (MLD) attached to an AP and operating on a link to exchange frames with a non-AP station attached to a non-AP MLD,

[0098] - transmitting a basic trigger frame (TF) on the link, the basic TF scheduling uplink (UL) resources to attached non-AP stations and including a preferred AC subfield in a trigger-related user information field of a user information field corresponding to the scheduled UL resources within the basic TF;

[0099] Wherein the preferred AC subfield is set to a value for an AC for which at least one corresponding traffic identifier (TID) is mapped in the UL for the link for the non-AP MLD via TID-to-link mapping.

[0100] The TID to link mapping may be negotiated between the AP MLD and the non-AP MLD. In addition, the method may further include:

[0101] - transmitting a Buffer Status Report Poll (BSRP) Trigger Frame (TF) on said link; and

[0102] - receiving a BSR frame reporting buffered traffic from the attached non-AP station on the link.

[0103] There is also provided an AP (AP) attached to a multi-link device (MLD), the AP being adapted to operate on a link of a wireless network to exchange frames with a non-AP station attached to a non-AP MLD. The attached AP comprises:

[0104] a transmitter configured to transmit a basic trigger frame (TF) on the link, the basic TF scheduling uplink (UL) resources to attached non-AP stations and including a preferred AC subfield in a trigger-related user information field of a user information field corresponding to the scheduled UL resources within the basic TF,

[0105] Wherein the preferred AC subfield is set to a value for an AC for which at least one corresponding traffic identifier (TID) is mapped in the UL for the link for the non-AP MLD via TID-to-link mapping.

[0106] Relatedly, the present invention also provides a wireless communication device comprising at least one microprocessor, wherein the at least one microprocessor is configured to execute any method defined above. The wireless communication device may be any one of a non-AP MLD and an APMLD.

[0107] Another aspect of the invention relates to a non-transitory computer-readable medium storing a program which, when executed by a microprocessor or a computer system in a wireless device, causes the wireless device to perform any method as defined above.

[0108] At least a portion of the method according to the invention may be computer-implemented. Thus, the invention may take the form of a fully hardware embodiment, a fully software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, which may be collectively referred to herein as "circuits," "modules," or "systems." Furthermore, the invention may take the form of a computer program product embodied in any tangible medium of expression having a computer-usable program code embodied in the medium.

[0109] Since the present invention can be implemented in software, the present invention can be embodied as computer readable code for providing to a programmable device on any suitable carrier medium. Tangible, non-transitory carrier media may include storage media such as floppy disks, CD-ROMs, hard disk drives, magnetic tape devices, or solid-state memory devices. Transient carrier media may include signals such as electrical signals, electronic signals, optical signals, acoustic signals, magnetic signals, or electromagnetic signals (e.g., microwave or RF signals). BRIEF DESCRIPTION OF THE DRAWINGS

[0110] Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which:

[0111] Figure 1 A typical 802.11 network environment involving ML transmission between MLDs with EML capability in which the present invention may be implemented is illustrated;

[0112] Figure 1a and Figure 1b An exemplary 802.11be multi-link reference model illustrating MLD for AP MLD or non-AP MLD;

[0113] Figure 2 Schematically illustrating an exemplary frame sequence of the EMLSR mode of operation as specified in the D2.0 standard;

[0114] Figure 3 An example of a MAC data frame including a buffer status report control field (BSR control field) according to 802.11ax is illustrated;

[0115] Figure 4a Illustrate a general format of a multi-link buffer status report (ML-BSR) specific to a multi-link device;

[0116] Figure 4b For example Figure 4a The ML-BSR format shown is based on the BSR control field according to 802.11ax;

[0117] Figure 5a Illustrate the EML Capability subfield in the Common Information Field of the Basic Multilink Element as specified in the IEEE P802.11be / D2.0 standard and extended with a new field according to an embodiment of the present invention;

[0118] Figure 5b exemplifies the format of the EML control field of the EML OM notification frame used to activate or deactivate the EML mode as defined in the IEEE P802.11be / D2.0 standard and extended with a new field according to an embodiment of the present invention;

[0119] Figure 5cIllustrate the format of a trigger frame as defined in the IEEE P802.11be / D2.0 standard and extended with two possible variations of new fields according to an embodiment of the present invention;

[0120] Figure 6 Using a flow chart to illustrate the steps performed by a non-AP MLD with EML capability according to an embodiment of the present invention;

[0121] Figure 7 Using a flow chart to illustrate corresponding steps performed by an EML-capable AP MLD according to some embodiments of the present invention;

[0122] Figure 8 The exemplary sequence of frame exchanges between an EML-capable AP MLD and an EML-active non-AP MLD is schematically illustrated in FIG. Figure 6 and Figure 7 A first possible operation handled in a flowchart of;

[0123] Fig. 9 The exemplary sequence of frame exchanges between an EML-capable AP MLD and an EML-active non-AP MLD is schematically illustrated in FIG. Figure 6 and Figure 7 A second possible operation handled in the flowchart of;

[0124] Fig.10 Schematically illustrated reference Fig. 9 A variation of the second possible operation is shown, in which the case where the EML-active non-AP MLD has specific constraints for the transmission of BSR frames is considered;

[0125] Fig.11 The architecture of the EMLSR capability for MLD used to implement the embodiment of the present invention is schematically illustrated;

[0126] Fig.12 Schematically illustrating an architecture for implementing the EMLMR capability for MLD according to an embodiment of the present invention; and

[0127] Fig.13 A schematic diagram showing a wireless communication device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0128] The technology described herein can be used in various broadband wireless communication systems, including communication systems based on orthogonal multiplexing schemes. Examples of such communication systems include space division multiple access (SDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency division multiple access (SC-FDMA) systems. SDMA systems can use sufficiently different directions to simultaneously transmit data belonging to multiple user terminals (i.e., wireless devices or STAs). TDMA systems can allow multiple user terminals to share the same frequency channel by dividing the transmission signal into different time slots or resource units, and each time slot is assigned to a different user terminal. OFDMA systems use orthogonal frequency division multiplexing (OFDM), which is a modulation technique that divides the entire system bandwidth into multiple orthogonal subcarriers or resource units. These subcarriers can also be referred to as frequency modulation, frequency bands, etc. With OFDM, each subcarrier can be modulated independently using data. An SC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit on subcarriers distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on blocks of adjacent subcarriers, or enhanced FDMA (EFDMA) to transmit on multiple blocks of adjacent subcarriers.

[0129] The teachings herein may be incorporated into (e.g., implemented in or performed by) various devices (e.g., STAs). In some aspects, a wireless device or STA implemented according to the teachings herein may include an access point (so-called AP) or may not include an access point (so-called non-AP STA or STA).

[0130] Although the examples are described in the context of a WiFi (RTM) network, the invention may be used with any type of wireless network, such as a mobile phone cellular network implementing very similar mechanisms.

[0131] An AP may include, be implemented as, or be referred to as a Node B, a radio network controller (“RNC”), an evolved Node B (eNB), a 5G next-generation base STA (gNB), a base STA controller (“BSC”), a base transceiver STA (“BTS”), a base STA (“BS”), a transceiver function (“TF”), a radio router, a radio transceiver, a basic service set (“BSS”), an extended service set (“ESS”), a radio base STA (“RBS”), or some other terminology.

[0132] A non-AP STA may include, be implemented as, or be referred to as a subscriber STA, a subscriber unit, a mobile STA (MS), a remote STA, a remote terminal, a user terminal (UT), a user agent, a user device, a user equipment (UE), a user STA, or some other terminology. In some implementations, a STA may include a cellular phone, a cordless phone, a session initiation protocol ("SIP") phone, a wireless local loop ("WLL") STA, a personal digital assistant ("PDA"), a handheld device with wireless connection capabilities, or some other suitable processing device connected to a wireless modem. Thus, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or a smart phone), a computer (e.g., a laptop computer), a tablet computer, a portable communication device, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a global positioning system (GPS) device, or any other suitable device configured to communicate via a wireless or wired medium. In some aspects, a non-AP STA may be a wireless node. Such a wireless node may provide, for example, connectivity to or from a network (eg, a wide area network such as the Internet or a cellular network) via a wired or wireless communication link.

[0133] The AP manages a collection of STAs (STAs registered to or associated with the AP) that together organize their access to the wireless medium for communication purposes. The STAs (including the APs to which they are registered) form a service set, hereinafter referred to as a basic service set (BSS) (although other terms may be used). The same physical STA used as an access point may manage two or more BSSs (and therefore corresponding WLANs): each BSS is therefore uniquely identified by a specific basic service set identifier (BSSID) and managed by a separate virtual AP implemented in the physical AP. Each STA is identified within the BSS due to an identifier (AID) assigned to the STA by the AP at registration.

[0134] The 802.11 family of standards defines various Medium Access Control (MAC) mechanisms to drive access to the wireless medium.

[0135] Current discussions in task group 802.11be introduce multi-link operation (MLO) when it comes to MAC layer operations, as shown in the draft IEEE P802.11be / D2.0 in May 2022. MLO allows multi-link devices to establish or set up multiple links and operate them simultaneously.

[0136] A multi-link device (MLD) is a logical entity and has more than one subordinate STA (STA) and has a single medium access control (MAC) service access point (SAP) for a logical link control (LLC), which includes one MAC data service. An access point multi-link device (or AP MLD) then corresponds to an MLD in which the individual STAs subordinate to the MLD are APs and are therefore referred to as "subordinate APs." A non-access point multi-link device (or non-AP MLD) corresponds to an MLD in which the individual STAs subordinate to the MLD are non-AP STAs and are therefore referred to as "subordinate non-AP STAs." According to the text, "multi-link device," "ML device" (MLD), "multi-link logical entity," "ML logical entity" (MLE), "multi-link set," and "ML set" are synonyms for the same type of ML device. Reference is made below to Figure 1a and Figure 1b An example architecture of a multi-link device is described below.

[0137] Then, multiple subordinate non-AP STAs of the non-AP MLD may set up communication links with multiple subordinate APs of the AP MLD, thereby forming a multi-link channel.

[0138] The links established for MLD (or enabling links) are theoretically independent, which means that the channel access process (to the communication medium) and the communication are performed independently on each link. Therefore, different links can have different data rates (e.g., due to different bandwidths, number of antennas, etc.) and can be used to communicate different types of information (each through a specific link).

[0139] Thus, a communication link or "link" corresponds to a given channel (eg, 20 MHz, 40 MHz, etc.) in a given frequency band (eg, 2.4 GHz, 5 GHz, 6 GHz) between an AP attached to an AP MLD and a non-AP STA attached to a non-AP MLD.

[0140] The attached APs and non-AP STAs operate on their respective channels according to one or more of the IEEE 802.11 standards (a / b / g / n / ac / ad / af / ah / aj / ay / ax / be) and other wireless communication standards.

[0141] Due to multi-link aggregation, traffic associated with a single MLD can theoretically be transmitted across multiple parallel communication links, thereby increasing network capacity and maximizing the utilization of available resources.

[0142] From an architectural perspective, an MLD typically contains a number of radios to implement its affiliated STAs, but not necessarily a number equal to the number of its affiliated STAs. In particular, a non-AP MLD may operate with a greater number of affiliated STAs than the number of radios (which may even be reduced to a single radio).

[0143] From this physical architecture, the D2.0 standard has defined several enhanced multi-link operation modes (or EML OM for short), namely Enhanced Multi-Link Single Radio (EMLSR) and Enhanced Multi-Link Multi-Radio (EMLMR). The D2.0 standard states that the two EMLSR and EMLMR modes are mutually exclusive.

[0144] Any non-AP MLD declares its support for EMLSR and / or EMLMR modes (in its so-called EML capabilities, see Figure 5a ) is declared to the AP MLD. In operational mode, the activation and deactivation of EMLSR or EMLMR mode is initiated by the non-AP MLD, which sends a specific EHT action frame called "EML OM Notification" to indicate the set of enabled links (so-called EMLSR or EMLMR links) for which the EMLSR or EMLMR mode is to be activated (see Figure 5b ). Typically, the set "EMLSR / EMLMR links" consists of two enabling links. However, a greater number of enabling links may be used.

[0145] Once activated, the EMLSR mode allows non-AP MLDs to simultaneously listen to the enabled links of the set "EMLSR links" to receive the initial control frame (e.g., MU-RTS trigger frame or BSRP trigger frame) transmitted by the AP MLD, and then exchange data frames with the AP MLD on only one link at a time (usually the link via which the initial control frame is received). The frame exchange sequence initiated by the AP MLD can be a trigger-based (TB) downlink (DL) transmission or a trigger-based (TB) uplink (UL) transmission on the link where the initial control frame is received. Individual non-AP MLDs may or may not support the EMLSR capable operating mode.

[0146] In EMLMR mode, a non-AP MLD is able to aggregate some physical resources of multiple radios dedicated to multiple enabled links (so-called EMLMR links) to transmit or receive data up to a predefined number of supported Rx / Tx spatial streams. This predefined number is higher than the number of supported Rx / Tx spatial streams for each radio, thereby providing throughput enhancement and latency reduction. As an example, a multi-radio (MR) non-AP MLD supporting EMLMR mode on two links (with associated radios) uses the two corresponding radios to communicate on the two links when the EMLMR mode is deactivated (e.g., in a 2×2 MIMO antenna configuration of each radio). On the other hand, a MR non-AP MLD uses a radio with aggregated physical resources of two radios (usually antennas) in its radio to communicate on one of the two links when the EMLMR mode is activated (e.g., in a 4×4 MIMO antenna configuration). At the same time, the other link (deprived of a physical antenna) cannot be used.

[0147] Once the EMLMR mode is activated, non-AP MLDs are allowed to simultaneously listen to the enabled links of the set "EMLMR links" to receive the initial frame transmitted by the AP MLD to initiate frame exchange, and then exchange data frames with the AP MLD on only one EMLMR link (of aggregated radio resources) at a time (usually the link via which the initial frame is received). The frame exchange sequence initiated by the AP MLD can be a trigger (TB)-based downlink (DL) transmission or a trigger (TB)-based uplink (UL) transmission on the link where the initial frame is received.

[0148] With the introduction of MLO, the D2.0 standard also defines a traffic identifier (TID) to link mapping mechanism. This mechanism allows the AP MLD and non-AP MLD that have or are setting up multi-links to determine how to assign UL and DL QoS traffic corresponding to TID values ​​between 0 and 7 to the set-up links of the non-AP MLD.

[0149] By default, all TIDs shall be mapped to all setup links for both DL and UL, and all setup links shall be enabled. Non-AP MLD and AP MLD with multi-link setup shall operate in this mode (i.e., default TID to link mapping) if TID to link mapping negotiation for different mappings does not occur or is unsuccessful or torn down.

[0150] The D2.0 standard defines a process that allows TID to link mapping negotiation in the DL and / or UL between an initiating MLD and a responding MLD. MLDs may support TID to link mapping negotiation. MLDs that support TID to link mapping negotiation have dot11TIDtoLinkMappingActivated equal to true. During the multilink (re)setup process, a non-AP MLD may initiate TID to link mapping negotiation by including a TID to link mapping element in a (re)association request frame. After the multilink (re)setup, in order to negotiate a new TID to link mapping, the initiating MLD shall send a separately addressed TID to link mapping request frame to the responding MLD. The responding MLD shall then send a separately addressed TID to link mapping response frame to the initiating MLD to accept the request, reject the request, or suggest another TID to link mapping. When two MLDs have negotiated a TID to link mapping, either MLD may tear down the negotiated TID to link mapping by sending a separately addressed TID to link mapping teardown frame.

[0151] In the MLD capabilities indicated in the common information field of the basic multilink information element, e.g., included in a (re)association request or response frame, the TID to link mapping negotiation support subfield indicates support for TID to link mapping negotiation; the following table collects the values ​​specified for this 2-bit subfield and the corresponding descriptions:

[0152]

[0153] An MLD that does not support TID to link mapping negotiation has dot11TIDtoLinkMappingActivated equal to false and shall set the TID to Link Mapping Negotiation Support subfield to 0. In this case, the default TID to link mapping applies.

[0154] An MLD that supports TID-to-link mapping negotiation has dot11TIDtoLinkMappingActivated equal to true and shall set the TID-to-Link Mapping Negotiation Support subfield in the MLD Capabilities and Operations field of the basic multilink element it transmits to a non-zero value.

[0155] If the TID-to-link mapping negotiation support subfield value received from the peer MLD is equal to 1, then the MLD initiating TID-to-link mapping negotiation to the peer MLD shall send TID-to-link mapping elements with each TID mapped to the same or different link sets.

[0156] If the TID-to-link mapping negotiation support subfield value received from the peer MLD is equal to 2, then the MLD initiating TID-to-link mapping negotiation to the peer MLD shall only send TID-to-link mapping elements where all TIDs are mapped to the same set of links (e.g., the set includes all setup links (idem default mapping) or a subset of setup links).

[0157] For ease of explanation, the following description focuses primarily on the EMLSR mode. However, similar considerations can be made with respect to the EMLMR mode.

[0158] Figure 1 A typical 802.11 network environment involving ML transmission between EML-capable MLDs (EMLSRs and / or EMLMRs) is illustrated in which the present invention may be implemented.

[0159] The wireless communication network 100 involves an AP MLD 110 and two non-AP MLDs 120 and 130. In this example, the two non-AP MLDs are considered to be EML-capable and have declared their respective capabilities to the AP MLD 110 within the EMLSR-related field and the EMLMR-related field of the EML-capability (these fields are referred to below as EMLSR-capability and EMLMR-capability (i.e., sub-parts of the EML-capability)). Of course, another number of non-AP MLDs that register with the AP MLD 110 and then exchange frames with it, as well as another (larger) number of non-AP MLDs that are EML-capable, can be envisioned.

[0160] AP MLD 110 has multiple subordinate APs. Figure 1 There are two attached APs 111 and 112 (also labeled as AP1 and AP2, respectively), each attached AP behaves as an 802.11 AP on its operating channel within a frequency band. Known 802.11 frequency bands include 2.4 GHz band, 5 GHz band and 6 GHz band. Of course, other frequency bands can be used to replace or supplement these three frequency bands.

[0161] The non-AP MLD 120, 130 has multiple subordinate non-AP STAs, each of which appears as an 802.11 non-AP STA in the BSS in which it is registered (managed by the subordinate AP 111 or 112). Figure 1 , two non-AP STAs 121 and 122 (also labeled as A1 and A2, respectively) are attached to the non-AP MLD 120, and two non-AP STAs 131 and 132 (also labeled as B1 and B2, respectively) are attached to the non-AP MLD 130.

[0162] For the purpose of illustration, non-AP MLDs 120 and 130 are single radio non-AP MLDs. For example, AP 111 is set to operate on channel 38 corresponding to a 40 MHz operating channel in the 5 GHz band, and AP 112 is also set to operate on channel 151 corresponding to another 40 MHz operating channel in the 5 GHz band. In another example, the affiliated STAs may operate on different frequency bands.

[0163] Each subordinate AP provides a link toward the AP MLD 110 to the subordinate non-AP STAs of the non-AP MLD (120 or 130). Therefore, the links of each non-AP MLD can be identified only with the identifier of each subordinate AP. In this context, each subordinate AP 111 and 112 can be identified by an identifier called a "link ID". The link ID of each subordinate AP is unique and does not change during the life cycle of the AP MLD. The AP MLD can assign link IDs to its subordinate APs by incrementing the ID from 0 (for the first subordinate AP). Of course, other terms such as "AP ID" and the like can be used in variations.

[0164] In order to perform multi-link communication, each non-AP MLD 120, 130 must discover, authenticate, associate and set up multiple links with the AP MLD 110, each link being established between an AP affiliated with the AP MLD 110 and a non-AP STA affiliated with the non-AP MLD. Each such link, referred to as an enabling link, enables respective channel access and frame exchanges between the non-AP MLD and the AP MLD based on the supported capabilities exchanged during association.

[0165] The discovery phase is referred to below as the ML discovery procedure, and the multi-link setup phase (or association phase) is referred to below as the ML setup procedure.

[0166] The ML discovery process allows a non-AP MLD to discover the wireless communication network 100, i.e., various links to the AP MLD provided by multiple subordinate APs. The ML discovery process therefore seeks various subordinate APs advertising the AP MLD and corresponding network information, such as including all or part of the capabilities and operating parameters. Once the non-AP MLD has discovered the wireless communication network 100 through the ML discovery process, and after the MLD authentication process, the ML setup process allows the non-AP MLD to select a set of candidate setup links between its own subordinate non-AP STAs and some of the discovered subordinate APs, and request the AP MLD 110 to establish these links, which may be accepted or rejected by the AP MLD. If the AP MLD accepts, the non-AP MLD is provided with an association identifier (AID) by the AP MLD, which is used by the subordinate non-AP of the non-AP MLD to communicate wirelessly with its corresponding subordinate APs over multiple links (communication channels). During the ML setup process, the non-AP MLD declares some or all of its capabilities. For example, the non-AP MLD can declare its EMLSR capabilities. For this purpose, appropriate fields are provided in the management frame. In particular, some management frames exchanged during the ML discovery and ML setup procedures contain new information elements specific to multilink operation (MLO), referred to as basic multilink elements. In fact, in all management frames including basic multilink elements except authentication frames, a non-AP or AP MLD with EMLSR capability (dot11EHTEMLSROptionImplemented equals true) or EMLMR capability (dot11EHTEMLMROptionImplemented equals true) sets the EMLSR or EMLMR Support bit to 1 in the EML Capability subfield of the Common Information field.

[0167] For the purpose of illustration, in the wireless communication network 100, during the ML setup process, two candidate setup links have been requested by the non-AP MLD 120 and accepted by the AP MLD 110: a first link 151 between the attached AP 111 (AP1) and the attached non-AP STA 121 (A1), and a second link 152 between the attached AP 112 (AP2) and the attached non-AP STA 122 (A2). Similarly, two candidate setup links have been requested by the multi-radio non-AP MLD 130 and accepted by the AP MLD 110: a first link 161 between the attached AP 111 (AP1) and the attached non-AP STA 131 (B1), and a second link 162 between the attached AP 112 (AP2) and the attached non-AP STA 132 (B2).

[0168] AP MLD 110, non-AP MLD 120 and non-AP MLD 130 are considered to be EMLSR capable (dot11EHTEMLSROptionImplemented equals true) or EMLMR capable (dot11EHTEMLMROptionImplemented equals true). They exchange their EMLSR or EMLMR capabilities (sub-part of EML capabilities) during their ML discovery process and multi-link setup phase.

[0169] As currently defined in the D2.0 standard, the EMLSR and EMLMR capabilities include the following subfields:

[0170] - "EMLSR Support" subfield, which indicates support for EMLSR operation of MLD. If MLD supports EMLSR operation, the EMLSR Support subfield is set to 1; otherwise, the subfield is set to 0;

[0171] - "EMLSR Padding Delay" 3-bit subfield, which indicates the minimum MAC padding duration of the padding field of the initial control frame requested by the non-AP MLD (as defined in Enhanced Multilink Single Radio Operation (Section 35.3.17)). The table converts the 3-bit value to the padding delay in μs. This delay is used to define the transition period required for the MLD to switch the state of its subordinate stations from the listening operation state to the enable / disable frame exchange state. As described below, the transition period consists of this delay added to the time length of the initial control frame response. Therefore, this transition period is referred to as "EMLSR active switching delay" in the following;

[0172] - "EMLSR Transition Delay" 3-bit subfield, which indicates the transition delay time required for the non-AP MLD to switch from the so-called frame exchange mode (on one of the enabled links) to the so-called listening mode of operation for the enabled links. The table converts the 3-bit value to a delay in μs. For example, it is set to 0 for 0 μs, 1 for 16 μs, 2 for 32 μs, 3 for 64 μs, 4 for 128 μs, 5 for 256 μs, and the values ​​6 to 7 are reserved;

[0173] - "EMLMR Support" subfield, which indicates support for EMLMR operation for the MLD. If the MLD supports the EMLMR operation, the EMLMR Support subfield is set to 1; otherwise, the field is set to 0;

[0174] - "EMLMR Delay" 3-bit subfield that indicates the minimum padding duration required for EMLMR link switching when a non-AP MLD is operating in EMLMR mode. This delay is used to define the transition period required for the MLD to switch the state of its subordinate stations when starting or ending a frame exchange. As described below, the transition period for the start of a frame exchange consists of this delay added to the time length of the initial control frame response. Therefore, this start transition period is hereinafter referred to as "EMLMR active switching delay".

[0175] - A "Transition Timeout" subfield indicates the timeout value for the exchange of EML operation mode notification frames in the EMLSR (or EMLMR).

[0176] When a non-AP MLD with EMLSR (respectively, EMLMR) capability intends to operate in a corresponding mode on a set of enabled links (referred to as EMLSR (respectively, EMLMR) links), a STA attached to the non-AP MLD transmits an EMLSR (respectively, EMLMR) Mode subfield of the EML Control field to an AP attached to an AP MLD with EMLSR (respectively, EMLMR) capability (here, AP MLD 110) (specified in the D2.0 standard) with an EMLSR (respectively, EMLMR) Mode subfield set to 1. The EMLSR (respectively, EMLMR) links are indicated in the EMLSR (respectively, EMLMR) Link Bitmap subfield of the EML Control field of the EML OM notification frame by setting the bit position of the EMLSR (respectively, EMLMR) Link Bitmap subfield to 1 for each EMLSR (respectively, EMLMR) link. For example, in the EMLSR (respectively, EMLMR) bitmap, bit position i corresponds to the link with link ID equal to i and is set to 1 to indicate that the link is a member of the EMLSR (respectively, EMLMR) links.

[0177] The AP affiliated with the AP MLD that receives the EML operation mode notification frame from the STA affiliated with the non-AP MLD then transmits the EML operation mode notification frame to one of the STAs affiliated with the non-AP MLD within the timeout interval indicated in the transition timeout subfield in the EML capability subfield of the basic multilink element (which starts from the end of the PPDU transmitted by the AP affiliated with the AP MLD) as an acknowledgment of the EML operation mode notification frame transmitted by the STA affiliated with the non-AP MLD.

[0178] After a STA attached to the non-AP MLD successfully transmits an EML operation mode notification frame on one of the EMLSR (respectively, EMLMR) links, the non-AP MLD operates in the EMLSR (respectively, EMLMR) mode, which is considered to be EMLSR active (respectively, EMLMR active).

[0179] When a non-AP MLD with EMLSR capability intends to disable the EMLSR (respectively, EMLMR) mode, the STA attached to the non-AP MLD transmits an EML operation mode (OM) notification frame (specified in the D2.0 standard) with the EMLSR (respectively, EMLMR) mode subfield of the EML control field set to 0 to the AP attached to the AP MLD. Again, the AP attached to the AP MLD, which receives the EML operation mode notification frame from the STA attached to the non-AP MLD, transmits the EML operation mode notification frame as an acknowledgment of the EML operation mode notification frame as described above. After the STA attached to the non-AP MLD successfully transmits the EML operation mode notification frame on one of the EMLSR (respectively, EMLMR) links, the non-AP MLD disables the EMLSR (respectively, EMLMR) mode.

[0180] The set of STAs affiliated to a non-AP MLD with EMLSR (respectively, EMLMR) capability operating on an EMLSR (respectively, EMLMR) link may be all or part of the STAs affiliated to the non-AP MLD. The STAs of this set are hereinafter referred to as "EMLSR co-affiliated STAs" (respectively, EMLMR co-affiliated STAs) of the non-AP MLD.

[0181] exist Figure 1 In the example of FIG. 4 , the EMLSR common affiliated STAs of the non-AP MLD 120 and the non-AP MLD 130 operate on the same link (ie, have the same affiliated AP, AP1 and AP2), which means that these STAs share the same EMLSR link.

[0182] Figure 1a An exemplary 802.11be multi-link reference model illustrating MLD for AP MLD or non-AP MLD.

[0183] The MLD includes a PHY layer 200, a MAC layer 220, a logical link control (LLC) sublayer, and an upper layer.

[0184] The upper layer may include applications that generate traffic data or use received traffic data.

[0185] The transmission and reception of traffic data is handled by the MAC 220 and PHY 200 layers. Such transmission and reception of traffic data may be performed over multiple links 20-x, 20-y, 20-z (see reference Figure 1 The transmission is performed on the incoming links 151, 152, 161, 162). Three links and therefore three auxiliary stations are shown. Of course, other configurations including two auxiliary stations or more than three auxiliary stations can be envisaged.

[0186] Traffic data is provided by upper layers as a sequence of data frames or "traffic flows". Each traffic flow, and therefore each data frame, is associated with an access category (AC) defined in the EDCA mechanism ( Figure 1b ). This mapping between flows or data frames and ACs is performed by classifier 213.

[0187] Recall that 802.11 stations (AP and non-AP stations) maintain four access categories (ACs), each with one or more corresponding transmission buffers or queues. The four ACs are generally defined as follows:

[0188] -AC1 and AC0 are reserved for best effort and background traffic. They have the second-lowest priority and the lowest priority respectively.

[0189] - AC3 and AC2 are usually reserved for real-time applications (eg, voice or video transmission). They have the highest priority and the second-to-last priority, respectively.

[0190] Data frames incoming from the upper layers of the protocol stack, known as MAC Service Data Units (MSDUs), are mapped onto one of the four ACs by the classifier 213 and are thus entered into the queue of the mapped AC.

[0191] Figure 1b An implementation model with four transmit queues (one for each access category) is illustrated.

[0192] The 802.11be multi-link reference model reflects the fact that an MLD may use several links for transmission and reception (particularly at the MAC layer 220 and PHY layer 200 levels).

[0193] The MAC layer 220 includes a unified upper MAC (UMAC) layer 230, and multiple lower MAC (LMAC) layers 220-x, 220-y, 220-z coupled with corresponding PHY layers 200-x, 200-y, 200-z, each coupling corresponding to the links 20-x, 20-y, 20-z.

[0194] The UMAC 230 performs functions that are common across all links, and each LMAC 220-x, 220-y, 220-z performs functions that are local to each link 20-x, 20-y, 20-z. The UMAC layer then provides a UMAC interface with the link-specific blocks 220-x, 220-y, 220-z, and also provides a UMAC Service Access Point (SAP) to the LLC and upper layers.

[0195] The UMAC 230 is responsible for link-agnostic MAC processes such as authentication, association, security association, sequence number assignment, MAC Protocol Data Unit (MPDU) encryption / decryption, aggregation / deaggregation, confirmation score boarding process, and the like.

[0196] Each data unit (MSDU) with a traffic type (user priority (UP), and thus traffic identifier (TID)) priority, arriving at the MAC layer 220 from an upper layer (e.g., link layer) is mapped onto one of the ACs according to a mapping rule at the UMAC layer 230. Then, still at the UMAC layer 230, the data unit (MSDU) is provided with the next available sequence number and is stored in a queue corresponding to its TID (or UP) within the mapped AC. Recall that an 802.11 station maps a TID onto an AC as follows (TIDx refers to TID=x):

[0197] -TID1 and TID2 are mapped to AC0 which is usually used for background traffic,

[0198] - TID0 and TID3 are mapped to AC1 which is usually used for best effort traffic,

[0199] -TID4 and TID5 are mapped to AC2 which is usually used for video traffic,

[0200] -TID6 and TID7 are mapped to AC3 which is usually used for voice traffic.

[0201] Each LMAC 220-x, 220-y, 220-z is responsible for link-specific functions such as channel access. In particular, each MLD MAC includes its own contention-based channel access process, such as EDCA 221-x, 221-y, 221-z. Some functions require joint processing of both the UMAC 230 and the LMAC 220-x, 220-y, 220-z.

[0202] like Figure 1a and Figure 1bAs shown, each EDCA 221-x, 221-y, 221-z of each link competes for each AC queue for each link. In this regard, each AC has its own set of queue competition parameters (i.e., EDCA access parameters) for each link, and is associated with a priority value, thereby defining higher or lower priority traffic for the MSDU. Therefore, for a given link, there are multiple traffic queues for servicing data traffic at different priorities. The arbitration inter-frame space (AIFSn), contention window (CW), and backoff value are known as EDCA access parameters and are specific to each AC on each link 20-x, 20-y, 20-z.

[0203] For MLD, each AC or traffic queue 210 is mapped to one EDCA engine 221 per link. Thus, each backoff entity 211 of the link-specific EDCA engine 221 is associated with the corresponding AC queue 210 for using the queue contention parameters and extracting the backoff value to initialize the corresponding queue backoff counter (BC) specific to each AC and each link. Figure 1b , backoff counters BC[x0], BC[x1], BC[x2], BC[x3] are associated with the traffic queues 210 of AC0, AC1, AC2, AC3, respectively, and will be used simultaneously to contend for access to link 20-x. Similarly, backoff counters BC[y0], BC[y1], BC[y2], BC[y3] are associated with the traffic queues 210 of AC0, AC1, AC2, AC3, respectively, and will be used simultaneously to contend for access to link 20-y. Similarly, backoff counters BC[z0], BC[z1], BC[z2], BC[z3] are associated with the traffic queues 210 of AC0, AC1, AC2, AC3, respectively, and will be used simultaneously to contend for access to link 20-z.

[0204] The backoff counter is used to contend for access to the link 20-x, 20-y or 20-z to transmit data stored in the queue of the AC. In practice, when the medium is idle, the backoff counter is decremented from its initialization value, and when the backoff counter reaches 0, the corresponding subordinate STA 201-x, 201-z is allowed to transmit (grant access).

[0205] When access to the wireless medium is granted for an AC on a given link, the MSDUs stored in the traffic queue 210 corresponding to the AC are transmitted to the physical (PHY) layer 200-x, 200-y, 200-z for transmission on the given link.

[0206] Figure 2The frame sequence is used to illustrate the EMLSR mode of operation in the non-AP MLD 120 when the AP MLD 110 decides to use the EMLSR mode. Of course, although the EMLSR mode is emphasized here by way of example, similar considerations can be made with respect to the EMLMR mode.

[0207] In this sequence, the non-AP MLD operates in the EMLSR mode, which means that an EML operation mode notification frame activating the EMLSR mode has been successfully transmitted by the affiliated STA of the non-AP MLD 120. In other words, the non-AP MLD has entered an active enhanced multi-link single radio (EMLSR) mode applied to a specific set of two or more enabled links.

[0208] The dependent STAs 121 and 122 are EMLSR common dependent STAs within the non-AP MLD 120. Each dependent STA can be in one of three defined states: a listening operation state, a frame exchange enabled state, and a frame exchange disabled state.

[0209] The non-AP MLD 120 is able to simultaneously listen on its EMLSR links by having one or more of its EMLSR co-affiliated STAs correspond to these links in an "awake" or "listening operation" state. For example, the affiliated STAs A1, A2 are in a listening operation state (labeled 241 and 242). The listening operation includes CCA (Clear Channel Assessment) and receiving an initial control frame of a frame exchange initiated by the AP MLD. Therefore, in the non-AP MLD 120, two EMLSR co-affiliated STAs simultaneously listen to receive an initial control frame from the AP MLD.

[0210] When the AP MLD 110 intends to initiate a frame exchange with one or more non-AP MLDs on one of the EMLSR links, the frame exchange is started by transmitting an initial control frame 245 that explicitly triggers the non-AP MLDs. To the extent possible, the initial control frame schedules the non-AP MLDs. The initial control frame for the frame exchange is sent in an OFDM PPDU or non-HT repeated PPDU format using a rate of 6 Mbps, 12 Mbps, or 24 Mbps (i.e., the MCS subfield in the frame is set to a value up to 2). As defined in the D2.0 standard, the initial control frame should be as defined in IEEE Standard 802.11ax. TM -MU-RTS trigger frame or BSRP trigger frame as defined in 2021. Given a trigger frame format, according to which such a frame includes one or more user information fields, this condition means that frame 245 includes a user information field addressed to the non-AP MLD, i.e., wherein the AID12 field is set to the AID of the non-AP MLD (obtained at registration).

[0211] In this example and as indicated by reference numeral "IC(A)", the initial control frame 245 explicitly triggers the non-AP MLDA 120. The initial control frame may explicitly trigger multiple non-AP MLDs using multiple user information fields therein.

[0212] The EMLSR co-affiliated STA of the non-AP MLD (e.g., affiliated STA A1 in the example) explicitly triggered by the initial control frame 245 of the received frame initiates the state change of the EMLSR co-affiliated STA of the non-AP MLD under consideration (e.g., the change of the state of affiliated STAs A1 and A2 in the example), and sends an initial control frame response (IC response) 246 to the AP AP1 affiliated to the AP MLD 110.

[0213] After receiving the initial control frame 245 of the frame exchange and transmitting the immediate response frame 246 as a response to the initial control frame, the STA (i.e., the receiving EMLSR co-affiliated STA A1 in the example) attached to the non-AP MLD that is listening on the corresponding link is configured to be able to transmit or receive frames on the enabled link (i.e., link 151 in the example) that received the initial control frame 245. To this end, a state switching process is called upon receiving the frame 245, which results in switching the receiving EMLSR co-affiliated STA from the listening operation state 241 to the "active frame exchange" or "enabled frame exchange" state (labeled as 251 in the figure) after the EMLSR active switching delay. The receiving EMLSR co-affiliated STA in this new state is able to receive PPDUs sent on the link that received the initial control frame 245 by using more than one spatial stream. The EMLSR active switching delay corresponds to the delay time required for the non-AP MLD to switch from the EMLSR listening operation mode to the EMLSR frame exchange mode. As described above, this is derived from the indication specified in the EML Capabilities exchanged with the AP MLD (via the EMLSR Stuffing Delay): it is the EMLSR Stuffing Delay added to the length of time of the Initial Control Frame Response 246 .

[0214] At the same time, other EMLSR co-affiliated STAs (i.e., STA A2 in the example) of the same non-AP MLD are configured not to transmit or receive on one or more other EMLSR links until the frame exchange is completed. To this end, a state switching process is also called for other EMLSR co-affiliated STAs, which then switch from the listening operation state 242 to a "blindness frame" or "disabled frame exchange" state (marked as 252 in the figure). In particular, the AP MLD does not transmit data intended for these other EMLSR co-affiliated STAs.

[0215] The state switching of all EMLSRs in the same non-AP MLD and the STAs attached to it is inseparable and therefore simultaneous, because this is the state switching of the entire radio resource chain (see below). Fig.11 ) is allocated to one of the STAs while the other STAs are deprived of such a chain. Regarding the EMLMR mode, the physical resources (e.g., antennas) of one radio resource chain are allocated (and aggregated) to another radio resource chain, so the former is deprived of transmission / reception capabilities (see below Fig.12 ).

[0216] The above shows that when the non-AP MLD operates in EMLSR mode (and more generally in either EMLSR and EMLMR modes), it is in a listening operation mode (its co-affiliated STAs are in a listening operation state) or a frame exchange mode (one of its co-affiliated STAs is in an enabled frame exchange state, while the other co-affiliated STAs are in a disabled frame exchange state).

[0217] As a result, only one of the EMLSR co-affiliated STAs that is not the AP MLD that is explicitly triggered can exchange data frames with the AP MLD at a time; this is typically the EMLSR co-affiliated STA that received the initial control frame 245 .

[0218] An exemplary frame exchange sequence is shown in the figure, which comprises the sending of an A-MPDU frame 255 by the subordinate AP AP1 to the explicitly triggered EMLSR co-subordinate STA A1 of the non-APMLD A120 (hence a downlink transmission), followed by a corresponding block acknowledgment 256 from the latter.

[0219] After the frame exchange operated by the receiving EMLSR co-affiliated STA ends plus the EMLSR transition delay specified in the EML capability, the non-AP MLD 120 switches back to the EMLSR listening operation state, which means that the receiving EMLSR co-affiliated STA A1 switches back to the listening operation state 241 and the other EMLSR co-affiliated STA A2 switches back to (listening operation state 242). Therefore, the state switching process is called for each EMLSR co-affiliated STA.

[0220] The non-AP MLD (here, non-AP MLD 120) may sense the end of the frame exchange if one of the following conditions is met:

[0221] (1) The MAC of the STA attached to the non-AP MLD that received the initial control frame 245 does not receive the PHY-RXSTART.indication primitive during the timeout interval of aSIFSTime+aSlotTime+aRxPHYStartDelay, which starts at the end of the PPDU (e.g., ACK 256) transmitted by the STA of the non-AP MLD as a response to the most recently received frame (e.g., A-MPDU frame 255) from the AP attached to the AP MLD, or starts at the end of the reception of the following PPDU, which contains a frame that does not require immediate ACK from the STA of the AP attached to the AP MLD. This indicates the end of the actual exchange with the AP MLD without receiving a subsequent frame from the AP MLD.

[0222] (2) The MAC of the STA attached to the non-AP MLD that received the initial control frame 245 receives the PHY-RXSTART.indication primitive during the timeout interval of aSIFSTime+aSlotTime+aRxPHYStartDelay, which timeout interval starts from the end of the PPDU (e.g., acknowledgment 256) transmitted by the STA of the non-AP MLD as a response to the most recently received frame (e.g., A-MPDU frame 255) from the AP attached to the AP MLD, or starts from the end of reception of the following PPDU, which contains a frame that does not require immediate acknowledgment from the STA of the AP attached to the AP MLD, and the STA attached to the non-AP MLD does not detect any of the following frames in the PPDU corresponding to the PHY-RXSTART.indication:

[0223] - Individually addressed frames where the RA is equal to the MAC address of the STA attached to the non-AP MLD;

[0224] - a trigger frame having one of the user information fields addressed to a STA attached to a non-AP MLD;

[0225] -CTS-to-self frame, where RA is equal to the MAC address of the AP attached to the AP MLD;

[0226] - A Multi-STA Block Ack frame with one per-AID TID information field addressed to a STA attached to a non-AP MLD;

[0227] - NDP announcement frame, which has one of the STA Information fields addressed to the STAs attached to the non-AP MLD.

[0228] This corresponds to the case where, after the actual exchange with the AP MLD, the non-AP MLD receives from the AP MLD another frame not addressed to the non-AP MLD (ie, no data is addressed to the non-AP MLD or no resources are allocated to the non-AP MLD).

[0229] (3) The STA attached to the non-AP MLD that receives the initial control frame 245 does not respond to the latest received frame (eg, A-MPDU frame 255) from the AP attached to the AP MLD that requires an immediate response after SIFS.

[0230] When the non-AP MLD 120 is now in the EMLSR snooping mode of operation, the AP MLD may initiate any new frame exchange sequence (with either of the non-AP MLDs 120 or 130) by transmitting a new initial control frame.

[0231] In the example of the figure, the AP MLD 110 decides to initiate again such a new sequence with the non-AP MLD 120 using its EMLSR co-affiliated STA A2 122. In detail, the AP MLD 110 transmits a new initial control frame 265IC(A) that explicitly triggers the non-AP MLD A 120 using its other affiliated AP 112, which is now received by the EMLSR co-affiliated STA A2 122. The receiving EMLSR co-affiliated STA A2 122 transmits a response frame 266 to the initial control frame 265. After the EMLSR active switching delay, the explicitly triggered non-AP MLD 120 switches to the EMLSR frame exchange mode, wherein the receiving EMLSR co-affiliated STA A2 122 switches from the listening operation state 242 to the enabled frame exchange state 272, while its other EMLSR co-affiliated STA A1 121 simultaneously switches from the listening operation state 241 to the disabled frame exchange state 271. The frames 275, 276 are then exchanged during the frame exchange sequence until the end of the sequence at which the non-AP MLD 120 switches back to the EMLSR listening mode of operation.

[0232] A-MPDU 255 / 275 is provided only for illustration. AP MLD may send other types of frames, such as basic trigger frames for triggering UL transmissions. Figure 2 A frame exchange consisting of a single frame 255 / 275 followed by an acknowledgment 256 / 276 is shown, but a simpler frame exchange may include only a single frame sent by the AP MLD without an acknowledgment, while a more complex frame exchange may include multiple exchange sequences, such as concatenated TXOPs for UL transmissions (triggered by a basic trigger frame) and / or for DL ​​transmissions (via a HE MU PPDU).

[0233] This illustrative example shows the advantages of the EMLSR mode in terms of throughput and latency: the AP MLD can quickly switch from one link to another, thereby improving communication performance for a limited increase in complexity and cost.

[0234] As described above, the foregoing description also applies to the EMLMR mode, and in particular has the following matches: the EMLMR delay applies to both the EMLSR filling delay and the EMLSR transition delay; the initial frame in the EMLMR mode matches the initial control frame in the EMLSR mode, and similarly, the initial frame response in the EMLMR mode matches the initial control frame response in the EMLSR mode; although not defined in the D2.0 standard, an EMLMR listening operation state / mode that matches the EMLSR listening operation state / mode may be defined (in which co-affiliated STAs listen to their links before physical radio resources are aggregated).

[0235] Figure 3 An example of a MAC data frame including a buffer status report control field (BSR control field) according to 802.11ax is illustrated.

[0236] The MAC data frame 400 shown includes a MAC header 410, a frame body 420, and an FCS field 430. The MAC header 410 includes a frame control header 411, a QoS control field 412, and an HT control field 413, among other fields. The QoS control field 412 is an original 802.11e format that can be used by non-AP stations of any 802.11 technology to report buffer status. Alternatively or possibly in addition, non-AP stations starting with 802.11ax versions (including other versions such as 802.11be / EHT) can use the HT control field 413 to do so.

[0237] Thus, when provided within the 802.11 MAC data frame 400, field 413 may be referred to inconsequentially as the HT or HE or EHT control field, depending on the 802.11 generation under consideration (respectively, 802.11ac, 802.11ax, or 802.11be).

[0238] 802.11 traditional BSR format:

[0239] As shown, the QoS control field 412 consists of two bytes including the following information items:

[0240] - bits B0 to B3 are used to store a traffic identifier (TID) 404 identifying a traffic flow. The traffic identifier takes the value of the transmission priority value (user priority (UP), a value between 0 and 7) corresponding to the data transmitted by the data frame, or for other data flows, takes the value of the traffic stream identifier (TSID) (a value between 8 and 15);

[0241] - Bit B4 is used by non-AP stations to distinguish the meaning of bits B8-B15 and is described in detail below;

[0242] - Bits B5 and B6 define the ACK Policy subfield, which specifies the acknowledgement policy associated with the data frame. This subfield is used to determine how the receiving station must acknowledge the data frame; Normal ACK, No ACK, or Block ACK.

[0243] - Bit B7 is reserved, which means it is not used by the current 802.11 standard; and

[0244] - If bit B4 is set to 1, bits B8-B15 represent the "Queue Size" subfield 403 to indicate the amount of buffered traffic for the TID 404 specified in bits B0-B3 at the non-AP station sending the frame. The queue size value is the total size of all packets buffered for the specified TID (rounded to the nearest multiple of 256 octets and expressed in units of 256 octets). The access point can use this information to determine the next TXOP duration it will grant to the station. A queue size of 0 indicates that there is no buffered traffic for the TID. A queue size of 255 indicates an unspecified or unknown size for the TID 404.

[0245] - As an alternative to the use of "Queue Size", if bit B4 is set to 0, bits B8-B15 represent the "Requested TXOP Duration" subfield. It indicates in units of 32 μs the duration required for the transmitting station to determine its next TXOP for the specified TID. Of course, "Requested TXOP Duration" provides an equivalent request as "Queue Size" because they both take into account all packets buffered for the specified TID.

[0246] The following description is done for buffer status reporting in the "queue size" format, since the "queue size" format is of greatest use (the "requested TXOP duration" format is deprecated for multi-user use). The 802.11e MAC frame format, and more particularly the QoS control field 412, has been retained for later standard releases as now described.

[0247] The legacy BSR according to 802.11e can handle one TID report for each MSDU frame, which is one reason why enhancements were later provided by the 802.11ax version.

[0248] 802.11ax BSR format:

[0249] The HT control field 413 may aggregate multiple (N in the figure) control fields, thereby generating a sequence of one or more control subfields 450. The length of the aggregated control field (A control field) 413 is equal to 30 bits.

[0250] Each control subfield 450 includes a control ID 451 subfield that indicates the type of information carried in the following control information subfield 452. If necessary, padding bits are added to reach a 30-bit A control field.

[0251] Therefore, various types of information may be provided through the A control field 413 according to the control ID 451. For example, when the control ID 451 is 1, the operation mode may be indicated in the control information subfield 452. Also, when the control ID 451 is 4, power data may be indicated in the control information subfield 452.

[0252] If the control ID subfield 451 is 3, the control information subfield 452 of the control subfield 450 contains buffer status information in the BSR control field format shown in the figure under reference numeral 460.

[0253] A non-AP station may report the buffer status for a preferred AC or for all AC queues. Buffer Status Information 460 consists of six subfields: ACI Bitmap 461, Delta TID 462, ACI High 463, Scale Factor 464, Queue Size High 465, and Queue Size All 466.

[0254] The first two subfields in the BSR control field 460, namely the ACI bitmap 461 and the incremental TID 462, are used to signal the number N of traffic identifiers for which there is buffered uplink (UL) traffic. TID .

[0255] The ACI bitmap subfield 461 has four bits and indicates the access category for which the buffer status is reported. Each bit of the ACI bitmap subfield 461 is associated with one of the four ACs and is set to 1 to indicate that the buffer status of the corresponding AC is included in the queue size all subfield 466, otherwise it is set to 0.

[0256] An exception is made for the specific case where the buffer status for all eight TIDs is included in the Queue Size Total subfield 466. In this case, the ACI Bitmap subfield=0 is combined with the Increment TID subfield 462 being set to 3.

[0257] The Incremental TID subfield 462, together with the value of the ACI Bitmap subfield, indicates the number of TIDs for which the non-AP station is reporting buffer status. The following table gives the relationship between these two subfields and the number of TIDs. The table is from Table 9-24e of document 802.11ax, version 8.0.

[0258]

[0259] The ACI high subfield 463 is used to indicate the ACI (Access Control Identifier) ​​of the preferred AC for which the amount of buffered traffic is specified in the queue size high subfield 465 .

[0260] The scaling factor subfield 464 indicates the unit SF (in octets) of the queue size high subfield 465 and the queue size total subfield 466 .

[0261] The Queue Size High subfield 465 indicates, in units of SF octets, the amount of buffered traffic for the AC identified by the ACI High subfield 463 , which is intended for the station (typically the AP) identified by the recipient address of the MAC frame 400 .

[0262] The Queue Size All subfield 466 indicates the amount of buffered traffic in units of SF octets for all ACs identified by the ACI Bitmap subfield 461 , which is intended for the station (typically the AP) identified by the recipient address of the MAC frame 400 .

[0263] The queue size value set in the Queue Size High subfield 465 and the Queue Size Total subfield 466 is the total size (rounded to the nearest multiple of SF octets) of all MSDUs and A-MSDUs buffered at the non-AP station reporting its buffer status.

[0264] The standardized 802.11ax BSR is reserved for reporting buffer status from one (or several) of the four queues. This format is no longer compatible with TID values ​​greater than 7, while the legacy format is still compatible. For example, upper layers may provide a data frame MSDU with an 802.1D user priority (UP) value that takes a reserved value of 8-15 for low-latency delivery services (known as TSID).

[0265] The current BSR process provides the AP with a protocol for obtaining the buffer status of each AC (i.e., each flow) on the non-AP side, so that the AP can send a trigger frame to trigger UL traffic. Therefore, the current BSR method enables the non-AP MLD to provide its transmission requirements globally to the AP MLD without considering that the AP MLD can schedule data transmission based on the link.

[0266] However, when scheduling on links, the AP MLD does not have accurate information about the links and, for example, the APMLD may not be aware of interference on some links. In fact, when selecting a link, the AP MLD does not provide any guarantees about the latency, reliability or jitter of the transmission (which mainly depends on the radio reception on the non-AP MLD side).

[0267] In fact, the non-AP MLD has a good understanding of its radio environment, so that it is better able to determine the best link for data transmission at a given time, knowing that some radio links are experiencing interference.

[0268] Therefore, AP MLD, which only considers contention between stations, may sometimes give stations uplink transmission opportunities on inappropriate links.

[0269] Described below Figure 4a and Figure 4b It is proposed to use a specific buffer status report suitable for multi-link devices, namely a multi-link buffer status report (ML-BSR), so that each non-AP MLD can report the buffered amount of data waiting to be transmitted for all flows or for one or more given flows, and the link identified by the non-AP MLD on which the non-AP MLD expects to be scheduled to transmit the reported amount of data.

[0270] Receiving such an ML-BSR, the AP MLD then has additional information about the link that the non-AP considers more suitable for subsequent scheduling of UL transmissions in SU or MU mode.

[0271] Figure 4a A general format of a multi-link buffer status report (ML-BSR) dedicated to a multi-link device is illustrated in FIG.

[0272] The proposed format 500 is intended to be generic, in the sense that it can be defined in new independent formats, such as Figure 4a As shown, or parts of the format can be added to various existing types of reports (e.g. Figure 4b 802.11ax buffer status shown).

[0273] In some embodiments, Figure 3 As shown, at least a portion of the report 500 will be transmitted via the A control field 413 of the MAC header 410. For example, when the control ID subfield 451 takes the value 7, it can be indicated in the control information subfield 452 that the values ​​8 to 15 are reserved (see Figure 4a ).

[0274] Report 500 is hereinafter referred to as a Multi-Link Buffer Status Report (ML-BSR). According to some embodiments, the use of ML-BSR is indicated by a new entry 505 in the Control ID table for the A Control field (eg, a Control ID having a value between 7 and 14).

[0275] like Figure 4a As can be seen in FIG. 1 , the ML-BSR includes an indication regarding the amount of data waiting to be transmitted associated with the link indication on which the non-AP ML is expected to transmit its data.

[0276] Therefore, the ML-BSR 500 consists of a traffic Id subfield 501 , a quantum field 502 of data, and a link ID 503 .

[0277] The first field 501 includes an indication about the type of data to which the ML-BSR applies.

[0278] The type of data may be, for example, the traffic for which the ML-BSR is issued. Depending on the delivery service negotiated between the ML AP and the non-APML station generating the report, it may appear that the traffic indication may be in two forms: per-class report and per-flow report.

[0279] Traffic flows with the same class also share the same traffic queue. Thus, in case of per-class reporting, the traffic queue is considered in the report: The indication is then either an AC value indicating the access class or a TID indicating the traffic type (ie user priority).

[0280] Furthermore, format 500 includes an indication regarding the amount of data waiting to be transmitted by the non-AP MLD.Amount of data 502 corresponds to a count of buffered data units associated with the current buffer report (ie, data units associated with the traffic considered in the ML-BSR).

[0281] In addition, format 500 includes an indication of the link on which the station is expected to be scheduled by the AP MLD. A non-AP MLD (i.e., an affiliated station) that is aware of the interference occurring on a link provides within the ML-BSR an indication of at least one link that is most suitable for transmitting the amount of data waiting to be transmitted. In addition, the non-AP MLD may further consider the amount of data reported when selecting a link.

[0282] exist Figure 4a , Link ID subfield 503 indicates the link identifier of the reporting MLD associated with the amount of data being reported. If the amount of data being reported is global and no portion must be transmitted on a given link, or if the reporting device does not have this information, the Link ID subfield is set to 15.

[0283] The link ID is the current information of the AP, which facilitates simplicity and efficiency in scheduling the next communication time slot for the indicated link. It should be noted that the term "AP ID" can be used instead of "link ID".

[0284] Therefore, such ML-BSR is a means for the initiator non-AP MLD to assist the scheduling AP MLD in ensuring that all waiting data is delivered on the intended link in a timely manner.

[0285] The ML-BSR is "real-time" information, or temporary information used for subsequent scheduling.

[0286] The ML-BSR is sent by the non-AP MLD using any enabled link between the non-AP MLD and the AP MLD regardless of the link ID indicated in the report.

[0287] Receiving such ML-BSR at the AP helps the AP MLD to manage the traffic. In fact, non-AP MLDs use ML-BSR to inform the AP MLD of the instantaneous global transmission demand for a given traffic on a given link, in case a per-class reporting format is used that considers several flows.

[0288] Now, about Figure 4b Another example of ML-BSR is described. For example, in response to a ML-BSRP trigger frame, a non-AP MLD may convey a ML-BSR in the BSR Control subfield 460 of any frame transmitted to the AP.

[0289] 802.11be / EHT stations (AP and non-AP) may set the ML-BSR Support subfield in the EHT Capability element of their transmissions to 1; otherwise, the station may set the ML-BSR Support subfield to 0. Thus, the ML-BSR Support subfield is therefore used by non-AP MLDs to indicate to the AP MLD during the association process whether the non-AP MLD supports ML-BSR.

[0290] Figure 4b Example based on 802.11ax Figure 3 The BSR control field 460 of the ML-BSR 506.

[0291] ML-BSR 506 includes fields related to the BSR description in 802.11ax format: ACI bitmap field 461 , incremental TID field 462 , ACI high field 463 , scaling factor 464 , and queue size high 465 .

[0292] In addition to these known subfields, a Link ID field 603 is added.

[0293] The ML-BSR report format corresponds to the following fields: ACI High field 463 , Scaling Factor 464 , Queue Size High 465 , and Link ID field 603 .

[0294] The ACI High subfield indicates the ACI of the AC for which the ML-BSR is indicated in the Queue Size High subfield.

[0295] In other words, the ACI high subfield 463 indicates the ACI of the AC for which the ML-BSR is established. Thus, the ACI high indicates the AC for which the buffer status is reported in the queue size high 465, i.e., the amount of data waiting to be sent for the indicated AC (corresponding to Figure 4a field 502).

[0296] In addition, the Scale Factor subfield indicates the unit SF (in octets) of the Queue Size High subfield.

[0297] The units used for the amount of data reported are specified in the scaling factor subfield 464 .

[0298] The Queue Size High subfield indicates the amount of buffered traffic in units of SF octets for the AC identified by the ACI High subfield, which is intended for the STA identified by the Receiver Address of the frame containing the ML-BSR Control subfield and is intended to be delivered via the link specified by the Link ID subfield.

[0299] Therefore, the Queue Size High 465 subfield corresponds to Figure 4a field 502.

[0300] The ML-BSR also includes an indication of the link that the station expects to be scheduled to transmit the buffered data specified in Queue Size High 465. The indication is included in Link ID field 603, indicating that the buffered data of Queue Size High 465 is intended to be delivered via the link specified by the Link ID subfield.

[0301] The Link ID subfield 603 is 4 bits in length and indicates the link identifier on which the reporting STA intends to transmit the specified amount of data traffic. The STA (e.g., AP MLD) identified by the receiver address of the frame containing the ML-BSR Control subfield is expected to schedule the frames buffered at the station that issued the ML-BSR to be delivered on the link specified by the Link ID subfield 603.

[0302] The other subfields are not used for ML-BSR reporting.

[0303] According to the 802.11ax standard, the ACI bitmap subfield 461 indicates the access category for which the buffer status is reported, ie, the queue size all 466 .

[0304] According to some embodiments, Queue Size Total 466 may no longer be reported. Therefore, the location of the Queue Size Total subfield may be used for Link ID subfield 603. A specific number of bits set to 0 in ACI Bitmap subfield 461 may indicate that the report is an ML-BSR so that the change in location is correctly interpreted.

[0305] As a result, in the case where the ACI bitmap subfield is 0 and the incremental TID subfield is different from 3 (because this value is already used in 802.11ax in the context of the ACI bitmap being set to 0), the receiving station will treat the buffer status 506 as an ML-BSR.

[0306] According to some embodiments, the Incremental TID subfield is set to 0 since this value is not applied for 802.11ax.

[0307] Previous references Figure 1 , Figure 1a , Figure 1b , Figure 2 , Figure 3 , Figure 4a and Figure 4b The context of the invention described has highlighted that the new EML operation and the new TID-to-link mapping mechanism currently specified in IEEE P802.11be / D2.0 may lack rules to enable coexistence with each other.

[0308] In an EMLMR or EMLSR frame exchange operation initiated by an AP MLD as currently specified in IEEE P802.11be / D2.0, the selection of an EMLMR or EMLSR link for a frame exchange sequence is driven by the AP MLD when sending an initial frame or initial control frame. Currently, the standard does not specify any rules for matching the selected EMLMR link or EMLSR link with the TID-to-link mapping used between the AP MLD and non-AP MLDs. In some cases, especially for TB UL traffic, the lack of such rules may result in some mismatches and inefficiencies.

[0309] As a first illustration, under negotiated uplink TID-to-link mapping with the TID-to-link mapping negotiation support subfield set to 1, in the case where the initial frame or initial control frame is a BSRP trigger frame sent by the AP MLD, the BSR response frame sent by the non-AP MLD may report buffered traffic for some TIDs that are not mapped on the link where the BSRP TF is received. In this case, triggering of the non-AP MLD by the AP MLD on this link for UL transmission is useless, and the overall EML operation initiated is inefficient.

[0310] As a second example, under the default TID to link mapping or the negotiated uplink TID to link mapping with the TID to link mapping negotiation support subfield set to 2, in the case where the initial frame or initial control frame is a BSRP trigger frame sent by the AP MLD, the ML-BSR response frame sent by the non-AP MLD may indicate a link for transmitting its buffered traffic that is not the link on which the BSRP TF is received. In this case, since the non-AP MLD local conditions (i.e., interference, etc.) are not considered, the triggering of the non-AP MLD for UL transmission on this link by the AP MLD may not be successful. In this case, again, the overall EML operation initiated is inefficient.

[0311] The object of the present invention is to coordinate EML mode operation (EMLMR or EMLSR) with uplink TID-to-link mapping for trigger-based uplink traffic transmission.

[0312] References below Figure 5a , Figure 5b , Figure 5c , Figure 6 , Figure 7 , Figure 8 , Fig. 9 and Fig.10 Embodiments of the invention are described which are intended to achieve this goal. These embodiments specify:

[0313] 1. New signaling to allow operation for TB UL traffic under the currently specified EML operation or under a new EML operation (EMLSR or EMLMR).

[0314] 2. New rules that match the UL TID to link mapping to the currently specified EML operation for TB UL traffic. The purpose is to cover inefficiencies in the current EML operation where BSR frame responses may be useless without these rules.

[0315] 3. New EML operation for TB UL traffic that allows EML link switching based on the content of the BSR frame response.

[0316] In this specification, the above two “current EML operation for TB UL traffic” and “new EML operation for TB UL traffic” are also referred to as the first sub-mode and the second sub-mode of the EML mode.

[0317] From the perspective of non-AP MLD, the signaling information indicates which of the following two sub-modes of EML mode is to be used:

[0318] a first sub-mode of the EML mode, in which, in response to a BSRP trigger frame received from the AP MLD on a given EML link in the EML link set, the non-AP MLD transmits a BSR frame to the AP MLD on the given EML link, the BSR frame reporting buffered traffic according to the UL TID-to-link mapping (e.g., buffered traffic of at least one UL TID mapped on the given EML link according to the UL TID-to-link mapping, if any); and

[0319] A second sub-mode of the EML mode, in which, in response to a BSRP trigger frame received from the AP MLD on the first EML link, the non-AP MLD transmits a BSR frame to the AP MLD on the first EML link, the BSR frame indicating a selected EML link in the EML link set to be used for frame exchange.

[0320] From the AP MLD perspective, the signaling information indicates which of the following two sub-modes of the EML mode is to be used:

[0321] a first sub-mode of the EML mode, the first sub-mode comprising transmitting, by the AP MLD to the non-AP MLD, a basic TF that schedules UL resources to the non-AP MLD and includes constraints on data to be transmitted within the scheduled UL resources based on a UL TID-to-link mapping; and

[0322] A second sub-mode of the EML mode, in which the AP MLD retrieves an indication of a selected EML link to be used for frame exchange from a BSR frame, and transmits a basic TF to the non-AP MLD on the selected EML link to trigger an uplink frame exchange with the non-AP MLD on the selected EML link.

[0323] Figure 5a The EML Capability subfield in the Common Information Field of the Basic Multilink Element as specified in the IEEE P802.11be / D2.0 standard and extended with a new field according to an embodiment of the present invention is illustrated.

[0324] During the ML setup process, the AP MLD and non-AP MLD declare some or all of their capabilities. For example, the AP MLD and non-AP MLD may declare their EMLSR capabilities and / or EMLMR capabilities. As described below, appropriate fields are provided in management frames, such as in ML association request / response frames.

[0325] The management frames exchanged during the ML discovery and ML setup procedures contain new multilink (ML) information elements (referred to as multilink elements) specific to multilink operation (MLO). In particular, the ML association request / response frames exchanged during the setup procedure are association request / response frames as defined in 802.11ax (e.g., IEEE P802.11ax / D8.0, October 2020) enhanced with the basic multilink elements defined in IEEE P802.11be / D2.0, in which AP MLDs and non-AP MLDs can declare their EML capabilities, among other declarations.

[0326] The EML capability subfield 520 is used to declare the capability of the MLD in terms of enhanced multilink (especially regarding EMLSR and EMLMR). This subfield includes an EMLSR support subfield 521, an EMLSR fill delay subfield 522, an EMLSR transition delay subfield 523, an EMLMR support subfield 524, an EMLMR delay subfield 525, a transition timeout subfield 526, and a reserved subfield 227.

[0327] More details about these subfields can be found in the IEEE P802.11be / D2.0 standard.

[0328] exist Figure 5a In the embodiment of the present invention, the EML capability subfield 520 is extended with a new subfield 528 according to an embodiment of the present invention. The AP MLD and non-AP MLD use the new subfield 528 to declare their support for the new EML operations described in the present invention.

[0329] If the MLD supports both the current EML operation and the new EML operation for triggered uplink EML frame exchange, that is, supports both EML frame exchange on the link transmitting / receiving BSRP TF and EML frame exchange on the link implicitly or explicitly indicated in the BSR frame for triggered uplink EML frame exchange, then the link indication subfield 528 (preferably, a one-bit subfield) supported for UL EML frame exchange is set to 1.

[0330] If the MLD only supports the current EML operation for triggered uplink EML frame exchange, that is, only supports EML frame exchange on the link that transmits / receives BSRP TF for triggered uplink EML frame exchange, then the link indication subfield 528 (preferably, a one-bit subfield) supported for ULEML frame exchange is set to 0.

[0331] Figure 5bThe format of the EML Control field of the EML OM Notification frame for activating or deactivating the EML mode as defined in the IEEE P802.11be / D2.0 standard and extended with the field according to an embodiment of the present invention is illustrated.

[0332] The EML control field 540 of the EML OM notification frame includes a one-bit EMLSR mode subfield 541, a one-bit EMLMR mode subfield 542, an EMLSR link bitmap subfield 543, a reserved subfield 544, an EMLMR link bitmap subfield 545, an MCS mapping count subfield 546, and an EMLMR supported MCS and NSS set subfield 547.

[0333] A non-AP MLD that supports EMLSR operation (as declared in its EML capabilities) sets the EMLSR Mode subfield 541 to 1 to request activation of EMLSR mode, and indicates the EMLSR link involved in the EMLSR Link Bitmap 543. This indicates that the non-AP MLD will operate in EMLSR mode. A non-AP MLD that supports EMLSR operation (as declared in its EML capabilities) sets the EMLSR Mode subfield 541 to 0 to indicate that it no longer intends to operate in EMLSR mode.

[0334] Similarly, a non-AP MLD that supports EMLMR operation (as declared in its EML capabilities) sets the EMLMR Mode subfield 542 to 1 to request activation of the EMLMR mode, and indicates the EMLMR link involved in the EMLMR link bitmap 545. This indicates that the non-AP MLD will operate in the EMLMR mode. A non-AP MLD that supports EMLMR operation (as declared in its EML capabilities) sets the EMLMR Mode subfield 542 to 0 to indicate that it no longer intends to operate in the EMLMR mode.

[0335] The D2.0 standard states that the two modes EMLSR and EMLMR are mutually exclusive.

[0336] More details about these subfields can be found in the IEEE P802.11be / D2.0 standard.

[0337] exist Figure 5bIn the embodiment of the present invention, the EML control field 540 is expanded with a new subfield 548 according to an embodiment of the present invention. The new subfield 548 is used by the non-AP MLD to indicate to the AP MLD that the EML operation mode is to be used for the requested EMLSR or EMLMR activation. In this case, the EML operation mode is driven by the non-AP MLD, and all triggered uplink EML frame exchanges of the non-AP MLD with the AP MLD that occur within the EMLSR or EMLMR activation will use the same EML operation mode.

[0338] The link indication subfield 548 (preferably, a one-bit subfield) for the UL EML frame exchange mode is set to 1 to indicate the use of the new EML operation for the triggered uplink EML frame exchange, i.e., to indicate that the EML frame exchange is performed on the link implicitly or explicitly indicated in the BSR frame for the triggered uplink EML frame exchange.

[0339] The link indication subfield 548 (preferably, a one-bit subfield) for UL EML frame exchange mode is set to 0 to indicate that the current EML operation is used for triggered uplink EML frame exchange, i.e., to indicate that EML frame exchange is performed on the link that transmits / receives BSRP TF for triggered uplink EML frame exchange.

[0340] Figure 5c The format of a trigger frame as defined in the IEEE P802.11be / D2.0 standard and augmented with two possible variations of new fields according to embodiments of the present invention is illustrated.

[0341] It should be understood that these two possible variations constitute the previous reference Figure 5b A first and a second variation of the embodiment are described.

[0342] The trigger frame 560 is a BSRP trigger frame based on the trigger frame format as defined in IEEE 802.11ax (HE) with some modified fields as defined in IEEE 802.11be / D2.0 (EHT).

[0343] The trigger frame 560 includes a MAC header 561 , a common information field 562 , a user information list field 563 , a padding field 564 , and an FCS field 565 .

[0344] The common information field 562 is typically an EHT variant common information field with the trigger type set to a value of 4 corresponding to a BSRP trigger frame.

[0345] The user information field 563 includes one of several EHT variant user information fields 566 .

[0346] More details about these fields can be found in the IEEE standard 802.11ax TM -2021 and IEEE P802.11be / D2.0 standards.

[0347] exist Figure 5c In the first variation of the BSRP trigger frame 560, the common information field 562 is augmented with a new subfield 568a according to an embodiment of the present invention. The new subfield 568a is used by the AP MLD to indicate to the addressed non-AP MLDs the EML operation mode to be used for the next trigger-based uplink EML frame exchange. In this case, for all non-AP MLDs addressed by the BSRP trigger frame 560 for the next trigger-based uplink EML frame exchange, the EML operation mode is driven by the AP MLD, which means that all non-AP MLDs will use the same EML operation mode.

[0348] The link indication subfield 568a for the UL EML frame exchange mode is typically a one-bit subfield, which uses one of the EHT reserved bits 56-62 available in the EHT variant common information field 562 as an example, or uses one bit in the EHT trigger-related common information subfield added in the EHT common information field 562 as another example.

[0349] The link indication subfield 568a (preferably, a one-bit subfield) for the UL EML frame exchange mode is set to 1 to indicate the use of the new EML operation for the next triggered uplink EML frame exchange, i.e., to indicate that the next EML frame exchange is performed on the link implicitly or explicitly indicated in the BSR frame for the next triggered uplink EML frame exchange.

[0350] The link indication subfield 568a (preferably, a one-bit subfield) for the UL EML frame exchange mode is set to 0 to indicate that the current EML operation is used for the next triggered uplink EML frame exchange, i.e., to indicate that the next EML frame exchange is performed on the link that transmits / receives the BSRP TF for the next triggered uplink EML frame exchange.

[0351] exist Figure 5cIn the second variation of the present invention, the user information field 566 is augmented with a new subfield 568b according to an embodiment of the present invention. The new subfield 568b is used by the AP MLD to indicate to a given addressed non-AP MLD that the EML operation mode is to be used for the next triggered uplink EML frame exchange. In this case, the EML operation mode is driven by the AP MLD for the next triggered uplink EML frame exchange of the given non-AP MLD addressed by the BSRP trigger frame 560, independently of the other non-AP MLDs addressed by the BSRP trigger frame 560, which means that the other non-AP MLDs can use the same or different EML operation modes.

[0352] The link indication subfield 568b for the UL EML frame exchange mode is typically a one-bit subfield, which, as an example, uses one of the reserved bits 25 available in the EHT variant user information field 566, or, as another example, uses one bit in the EHT trigger-related user information subfield added in the EHT user information field 566.

[0353] The link indication subfield 568b (preferably, a one-bit subfield) for the UL EML frame exchange mode is set to 1 to indicate the use of the new EML operation for the next triggered uplink EML frame exchange, i.e., to indicate that the next EML frame exchange is performed on the link implicitly or explicitly indicated in the BSR frame for the next triggered uplink EML frame exchange.

[0354] The link indication subfield 568b (preferably, a one-bit subfield) for the UL EML frame exchange mode is set to 0 to indicate that the current EML operation is used for the next triggered uplink EML frame exchange, i.e., to indicate that the next EML frame exchange is performed on the link on which the BSRP TF is transmitted / received for the next triggered uplink EML frame exchange.

[0355] Refer to the previously described Figure 5a , Figure 5b and Figure 5c According to an embodiment of the present invention, the names "Link indication for UL EML frame exchange support" and "Link indication for UL EML frame exchange mode" are introduced for new signaling. These names are mainly used for illustrative purposes, and other names may be considered.

[0356] Figure 6 The steps performed by a non-AP MLD with EML capability according to an embodiment of the present invention are illustrated using a flowchart; the flowchart handles reference Figure 8 and Fig. 9 The frame exchange sequence shown in the embodiment described (with reference to the flowchart steps) is shown.

[0357] At step 600, the non-AP MLD performs ML setup with the AP MLD. During this process, according to the present invention, the non-AP MLD and the AP MLD significantly exchange their EML capabilities, wherein each MLD can exchange supported link indications for UL EML frames through a new subfield (reference numeral 528, Figure 5a ) to indicate whether it supports new EML operations.

[0358] At step 605, the non-AP MLD and the AP MLD optionally initiate a TID to link mapping process to negotiate TID to link mapping in DL, UL, or both. This process may be initiated at any time during or after ML setup. As an example, the non-AP MLD and the AP MLD negotiate Figure 8 The TID to link mapping described in .

[0359] In step 610, the non-AP MLD enters the EML mode (EMLMR or EMLSR mode), typically by successfully exchanging an EML OM notification with the EML mode subfield (EMLMR mode or EMLSR mode) of the EML control field set to 1 with an EML-capable AP MLD, which also specifies the EML link (EMLMR link or EMLSR link), thereby specifying the corresponding EML co-affiliated STA.

[0360] According to an embodiment of the present invention, the non-AP MLD Figure 8 The description specifies the EML link under rules 1 and 2.

[0361] In a specific embodiment, these rules can be summarized as follows: Activating EML mode includes, at the non-AP MLD, selecting an EML link set of links to which EML mode is applied based on the UL TID to link mapping, and transmitting a notification specifying the selected EML link set to the AP MLD. Figure 8 More details and variations are presented in the description of FIG.

[0362] As a new signal notification, the non-AP MLD also configures the EML control field 540 (see Figure 5b ) through a new subfield "Link indication for UL EML frame exchange mode" (reference numeral 548, Figure 5b ) to indicate whether to use the current EML mode operation or the new EML operation for the active EML mode.

[0363] In other words, the non-AP MLD transmits to the AP MLD signaling information indicating which of the two aforementioned "current EML mode operation" and "new EML operation" (also referred to as the first sub-mode and the second sub-mode of the EML mode (see above)). In a specific embodiment, the signaling information is included in a subfield (548) of the EML control field (540) of the EML OM notification frame transmitted by the non-AP MLD.

[0364] The non-AP MLD is in the EML listening operation mode at this time, which means that its EML co-affiliated STAs are in the listening operation state, and thus listen to their respective links at the same time.

[0365] In step 615, an initial control frame or an initial frame is received by one of the EML co-affiliated STAs from the AP MLD on a receive link.

[0366] Here, the received initial control frame or initial frame is as previously described in Figure 5c The BSRP Trigger Frame (TF) is described in IEEE Standard 802.11ax. TM -The Buffer Status Report Poll (BSRP) procedure introduced in 2021 to solicit the uplink data requirements of the solicited STAs (particularly by requesting their buffered uplink data amount) and allow the AP to schedule resource allocations for synchronous uplink transmissions. In response to the BSRP trigger frame, each soliciting / intending STA may send an immediate feedback Buffer Status Report (BSR), which may therefore be considered an Initial Control Frame Response or Initial Frame Response.

[0367] The received BSRP TF typically schedules non-AP MLDs and other non-AP MLDs, or more generally explicitly triggers one or more receiving STAs.

[0368] As a first variant of the new signaling, the AP MLD is in the common information field 562 of the BSRP TF according to a particular embodiment of the present invention (and more precisely, in the new subfield "Link Indication for UL EML Frame Exchange Mode" ( Figure 5c In the reference numeral 568a), a new subfield "Link indication for UL EML frame exchange mode" is used to indicate whether the next upcoming UL EML frame exchange for all scheduled non-AP MLDs will use the current EML operation mode or the new EML operation mode.

[0369] As a second variant of the new signaling, the AP MLD is in the user information field 566 of the non-APMLD of the BSRP TF according to a specific embodiment of the present invention (and more precisely, in the new subfield "Link Indication for UL EML Frame Exchange Mode" ( Figure 5c In the figure mark in), the new subfield "Link indication for UL EML frame exchange mode" is used to indicate whether the next upcoming UL EML frame exchange for the scheduled non-AP MLD will use the current EML operation mode or the new EML operation mode.

[0370] In other words, in the first variant of the new signal notification, the signal notification information is contained in a subfield (568a) of the common information field (562), and in the second variant of the new signal notification, the signal notification information is in a subfield (568b) of the user information field (566) assigned to the non-AP MLD within the BSRP TF transmitted by the AP MLD.

[0371] At step 620, the non-AP MLD checks whether the new EML operation mode is to be used by testing whether both the Link Indication for UL EML Frame Exchange Support and the Link Indication for UL EML Frame Exchange Mode subfields are set to 1.

[0372] When test 620 is negative, the next step is 630, which means that the current EML operation using the new rules specified in the embodiment of the present invention will be used.

[0373] When the test 620 is positive, the next step is 640, which means that the new EML operation specified in the embodiment of the present invention will be used.

[0374] In step 630, the non-AP MLD initiates the switching of its EML co-affiliated STA from the listening operation state to the EML frame exchange state. More precisely, the non-AP MLD initiates the switching of its receiving EML co-affiliated STA from the listening operation state to the enabled frame exchange state on the link receiving the BSRP TF. In parallel (simultaneously), the non-AP MLD initiates the switching of its other EML co-affiliated STA from the listening operation state to the disabled frame exchange state on another link.

[0375] In step 631, the receiving EML co-affiliated STA of the scheduled non-AP MLD transmits an initial control frame response or an initial frame response as a BSR frame.

[0376] According to a specific embodiment of the present invention, the non-AP MLD Figure 8 The BSR frame is transmitted under the rule 4 specified in the description.

[0377] In a specific embodiment, the rules can be summarized as follows: When the non-AP MLD operates in the EML mode with the EML link set, the non-AP MLD transmits a BSR frame reporting buffered traffic according to the UL TID-to-link mapping to the AP MLD on the first EML link in response to a buffer status report poll (BSRP) trigger frame received from the AP MLD on the first EML link in the EML link set. Figure 8 More details and variations are presented in the description of FIG.

[0378] Next, in step 632, if the EML co-affiliated STA of the non-AP MLD changes from the EML listening operation state to the EML frame exchange state, the non-AP MLD completes the switching. More precisely, the non-AP MLD completes the switching of its receiving EML co-affiliated STA from the listening operation state to the enabled frame exchange state on the link receiving the BSRP TF in step 633. In parallel (simultaneously), in step 634, the non-AP MLD initiates the switching of its other EML co-affiliated STA from the listening operation state to the disabled frame exchange state on another link.

[0379] Next, at step 635, the receiving EML co-affiliated STA of the non-AP MLD performs a frame exchange sequence with the corresponding affiliated AP of the AP MLD on the receiving link (ie, the link where the BSRPTF is received).

[0380] At step 640, the non-AP MLD initiates the switching of its EML co-affiliated STAs from the listening operation state to the EML frame exchange state based on the content of the BSR frame being prepared.

[0381] More precisely, if the BSR frame being prepared implicitly or explicitly indicates that the link to be used for frame exchange is a receiving link (i.e., a link that has received the BSRP TF), the non-AP MLD initiates the switching of its receiving EML co-affiliated STA from the listening operation state to the enabling frame exchange state on the link that has received the BSRP TF. In parallel (simultaneously), the non-AP MLD initiates the switching of its other EML co-affiliated STA from the listening operation state to the disabling frame exchange state on another link.

[0382] If the BSR frame being prepared implicitly or explicitly indicates that the link to be used for frame exchange is another link, the non-AP MLD initiates the switching of its other EML co-affiliated STA from the listening operation state to the frame exchange enabled state on the other link. In parallel (simultaneously), the non-AP MLD initiates the switching of its receiving EML co-affiliated STA from the listening operation state to the frame exchange disabled state on the receiving link.

[0383] According to a specific embodiment of the present invention, non-AP MLD is based on Fig. 9 Rules 6, 8, and 9 specified in the description of identify the link to be used for EML frame exchange based on the content of the BSR frame being prepared.

[0384] In a particular embodiment, these rules can be summarized by the fact that the non-AP MLD performs the following actions:

[0385] - receiving a BSRP TF from the AP MLD on a first EML link in the EML link set;

[0386] -selecting an EML link to be used for frame exchange in the EML link set based on the UL TID to link mapping and the buffered traffic to be reported in the BSR frame; and

[0387] - Transmitting a BSR frame indicating the selected EML link to be used for frame exchange to the AP MLD on the first EML link. Fig. 9 More details and variations are presented in the description of FIG.

[0388] In step 641, the receiving EML co-affiliated STA of the scheduled non-AP MLD transmits an initial control frame response or an initial frame response as a BSR frame.

[0389] If the transmitted BSR frame implicitly or explicitly indicates that the link to be used for frame exchange is the receiving link (ie, the link (link #1) that received the BSRP TF), the next step is step 632 which has been described.

[0390] If the transmitted BSR frame implicitly or explicitly indicates that the link to be used for frame exchange is another link, the next step is step 642 .

[0391] Next, in step 642, if the EML co-affiliated STA of the non-AP MLD changes from the EML listening operation state to the EML frame exchange state, the non-AP MLD completes the switching. More precisely, in step 643, the non-AP MLD completes the switching of its other EML co-affiliated STA on another link from the listening operation state to the enabled frame exchange state. In parallel (simultaneously), in step 644, the non-AP MLD initiates the switching of its receiving EML co-affiliated STA from the listening operation state to the disabled frame exchange state on the receiving link (i.e., the link (link #1) that received the BSRP TF).

[0392] Next, in step 645, the other EML co-affiliated STA of non-AP MLD performs a frame exchange sequence with the corresponding affiliated AP of APMLD on the other link.

[0393] As long as the end of the frame exchange on the link for frame exchange (the receiving link for frame exchange 635 or the other link for frame exchange 645) is not detected in step 650, the frame exchange of step 635 or 645 continues.

[0394] When such an end of the frame exchange is detected in the test 650, the non-AP MLD switches back to the EML listening operation state in step 655. To this end, the receiving EML co-affiliated STA corresponding to the receiving link switches back to the listening operation state in step 656, while in parallel (synchronously), the other EML co-affiliated STA also switches back to the listening operation state in step 657.

[0395] Figure 7 The flowchart is used to illustrate the corresponding steps performed by the AP MLD with EML capability according to some embodiments of the present invention; the flowchart handles the reference Figure 8 and Fig. 9 The frame exchange sequence shown in the embodiment described (with reference to the flowchart steps) is shown.

[0396] In this flow chart, exemplary steps performed by an AP MLD are processed for a given non-AP MLD, which means that the same processing is performed for each non-AP MLD that enters the EML mode.

[0397] The AP MLD performs ML setup with the non-AP MLD in step 700. During this process, the APMLD and the non-AP MLD significantly exchange their EML capabilities according to an embodiment of the present invention, wherein each MLD can indicate whether it supports the new EML operation through a new subfield "Exchange Supported Link Indication for UL EML Frame".

[0398] In step 705, the AP MLD and the non-AP MLD optionally initiate a TID to link mapping process to negotiate TID to link mapping in DL, UL, or both. This process can be initiated at any time during or after ML setup. As an example, the AP MLD and the non-AP MLD negotiate Figure 8 The TID to link mapping described in .

[0399] Step 710 corresponds to successfully exchanging an EML OM notification with the non-AP MLD to cause the non-AP MLD to enter the EML mode. As described above, the EML OM notification received from the non-AP MLD specifies the EML link and thus the corresponding EML co-affiliated STA.

[0400] As a new signal notification according to a specific embodiment of the present invention, the EML control field 540 of the EML OM notification received from the non-AP MLD is notified by a new subfield “Link Indication for UL EML Frame Exchange Mode” (reference numeral 548, Figure 5b ) to indicate whether the current EML mode operation or the new EML operation is to be used for the activated EML mode.

[0401] Next, in step 715, the AP MLD stores the EML links in a local memory, in addition to several other parameters, and stores the non-AP MLD state as an EML listening operational state. For example, the AP MLD may store in the local memory a first indication that a first link in the EML links is in a listening operational state and a second indication that a second link in the EML links is also in a listening operational state.

[0402] Next, at step 720, the AP MLD checks whether the non-AP MLD is in the EML listening operation mode.

[0403] In the negative, processing loops back to step 720.

[0404] In the affirmative, processing proceeds to step 725.

[0405] At step 725, the AP MLD checks whether it needs to initiate a frame exchange sequence with one or more non-AP MLDs. Various criteria may be used for each non-AP MLD. For example, the AP MLD may have data in a local buffer to send to the non-AP MLD. As another example, the AP MLD may know that the non-AP MLD needs uplink resources. As yet another example, the APMLD may poll the non-AP MLD to know its buffer status report (BSR).

[0406] In the negative, processing loops back to step 725.

[0407] In the affirmative, the AP MLD starts constructing the content of the initial control frame or initial frame (here BSRP TF), and the process goes to step 730 .

[0408] As a first variation of the new signal notification, the AP MLD uses a new subfield “Link Indication for UL EML Frame Exchange Mode” (reference numeral 568a, Figure 5c ) indicates whether the next upcoming UL EML frame exchange for all scheduled non-AP MLDs is to use the current EML operation mode or the new EML operation mode to construct the BSRP TF.

[0409] As a second variation of the new signal notification, the AP MLD uses a new subfield “Link Indication for UL EML Frame Exchange Mode” (reference numeral 568b, Figure 5c ) indicates whether the next upcoming UL EML frame exchange for the scheduled non-AP MLD is to use the current EML operation mode or the new EML operation mode to construct the BSRP TF.

[0410] Then, at step 730, the AP MLD checks whether the new EML operation mode is to be used by testing whether both the Link Indication for UL EML Frame Exchange Support and the Link Indication for ULEML Frame Exchange Mode subfields are set to 1.

[0411] When test 730 is negative, the next step is 740, which means that the current EML operation with the new rules specified in the embodiment of the present invention is to be used.

[0412] When test 730 is positive, the next step is 750, which means that the new EML operation specified in the embodiment of the present invention is to be used.

[0413] At step 740, the AP MLD transmits a BSRP TF scheduling one or more non-AP MLDs on a shared link (referred to as link #1 for simplicity) among its EML links.

[0414] As described above, in the first variant or the second variant of the new signaling, the AP MLD transmits the BSRPTF by setting the new subfield "Link indication for UL EML frame exchange mode" to 0 (ie, indicating that the current EML operation mode is to be used).

[0415] According to a specific embodiment of the present invention, the AP MLD Figure 8 Prepare and transmit BSRPTF frames according to the rules specified in the description 3.

[0416] In step 741, the AP MLD checks whether a BSR frame is received from one or more non-AP MLDs on link #1 at the appropriate time.

[0417] In the negative, processing loops back to step 720.

[0418] In the affirmative, the AP MLD considers that the non-AP MLD has completed its switch to the EML frame exchange state. Therefore, in step 742, the AP MLD stores such a state in a local memory for each scheduled non-AP MLD. For example, the AP MLD may set the first indication of link #1 to the enabled frame exchange state, and set the second indication of another EML link to the disabled frame exchange state.

[0419] In step 743, the AP MLD prepares and sends a basic TF that triggers the non-AP MLD for MU UL OFDMA transmission on link #1.

[0420] According to a specific embodiment of the present invention, the AP MLD Figure 8 Prepare and transmit basic TF frames according to the rules specified in the description 5.

[0421] In a specific embodiment, this rule can be summarized by the fact that the AP MLD performs the following actions:

[0422] - transmitting the BSRP TF to the non-AP MLD on a first EML link in the EML link set;

[0423] - receiving a BSR frame reporting buffered traffic from a non-AP MLD on the first EML link; and

[0424] - Transmitting a basic TF to the non-AP MLD over the first EML link, the basic TF scheduling UL resources to the non-AP MLD and containing constraints on data to be transmitted within the scheduled UL resources based on UL TID to link mapping.

[0425] Below Figure 8 More details and variations are presented in the description of FIG.

[0426] Next, at step 744, the receiving EML co-affiliated STA of the non-AP MLD and the corresponding affiliated AP of the AP MLD perform a frame exchange sequence on link #1 (ie, the receiving link, ie, the link that transmits the BSRP frame).

[0427] At step 750, the AP MLD transmits a BSRP TF scheduling one or more non-AP MLDs on one of the shared links (referred to as link #1 for simplicity) among its EML links.

[0428] As described above, in the first variant or the second variant of the new signaling, the AP MLD transmits the BSRP TF by setting the new subfield "Link indication for UL EML frame exchange mode" to 1 (ie, indicating that the new EML operation mode is to be used).

[0429] In step 751, the AP MLD checks whether a BSR frame is received from one or more non-AP MLDs on link #1 at the appropriate time.

[0430] In the negative, processing loops back to step 720.

[0431] When affirmative, processing proceeds to step 752.

[0432] At step 752, the AP MLD decodes the BSR frame and determines a link to be used for the next EML frame exchange with the non-AP MLD.

[0433] More precisely, if the received BSR frame implicitly or explicitly indicates that the link to be used for frame exchange is the receiving link (ie, the link that received the BSRP TF, ie, link #1), the process proceeds to step 742, which has been described.

[0434] If the received BSR frame implicitly or explicitly indicates that the link to be used for frame exchange is another link, the process proceeds to step 753 .

[0435] According to a specific embodiment of the present invention, the AP MLD Fig. 9 Under rules 7, 8, and 9 specified in the description of , a link to be used for EML frame exchange is identified based on the content of the received BSR frame.

[0436] In a particular embodiment, these rules can be summarized by the fact that the AP MLD performs the following actions:

[0437] - receiving a BSR frame from a non-AP MLD on a first EML link in response to a BSRP TF transmitted on the first EML link in the set of EML links;

[0438] - retrieving from the BSR frame an indication of a selected one of the EML links to be used for frame exchange; and

[0439] - Transmitting a basic TF to the non-AP MLD on the selected EML link to trigger an uplink frame exchange with the non-AP MLD on the selected EML link.

[0440] Below Fig. 9 More details and variations are presented in the description of FIG.

[0441] At step 753, the AP MLD considers that the non-AP MLD has completed its switch to the EML frame exchange state. Therefore, the AP MLD stores such a state in the local memory for each scheduled non-AP MLD at step 753. For example, the AP MLD may set the first indication for another link to the enabled frame exchange state, and set the second indication for link #1 to the disabled frame exchange state.

[0442] At step 754, the AP MLD prepares and sends a basic TF for triggering the non-AP MLD to perform MU ULOFDMA transmission on another link.

[0443] According to a specific embodiment of the present invention, the AP MLD Figure 8 Prepare and transmit basic TF frames according to the rules specified in the description 5.

[0444] Next, at step 755, the other EML co-affiliated STA of non-AP MLD and the corresponding affiliated AP of AP MLD perform a frame exchange sequence on the other link.

[0445] As long as the end of the frame exchange is not detected at step 745 or 756, respectively, on the corresponding link for frame exchange (receive link (link #1) 745 for frame exchange or another link 755 for frame exchange), the frame exchange of step 744 or 755 continues.

[0446] When the end of the frame exchange is detected at step 745 or 756 , processing loops back to step 720 .

[0447] Figure 8 The exemplary sequence of frame exchanges between an EML-capable AP MLD and an EML-capable non-AP MLD is schematically illustrated. Figure 6 and Figure 7 The first possible operation handled in the flowchart of .

[0448] In this Figure 8 In the context of MU UL OFDMA transmission, the initial control frame or initial frame is a BSRP trigger frame, and the initial control frame response or initial frame response is a BSR frame.

[0449] and Figure 2 Like reference numerals correspond to like frames / states, etc.

[0450] Again, the AP MLD 110 includes two subordinate APs 111 and 112 , the non-AP MLD 120 includes two subordinate STAs 121 and 122 , and the non-AP MLD 130 includes two subordinate STAs 131 and 132 .

[0451] In this Figure 8 , it is assumed that two subordinate STAs 121 and 122 of the non-AP MLD 120 and two subordinate STAs 131 and 132 of the non-AP MLD 130 are able to transmit a BSR frame while being in a listening operation state.

[0452] In this Figure 8In the embodiments, and in the reference Fig. 9 and Fig.10 In the next described embodiment, unless explicitly indicated otherwise, the TID-to-link mappings shown in the following table are assumed to have been negotiated first between the AP MLD 110 and the non-AP MLD 120 and secondly between the AP MLD 110 and the non-AP MLD 130 (steps 605, 705):

[0453]

[0454] In summary, the same downlink TID-to-link mapping has been negotiated between AP MLD 110 and non-AP MLD 120, and between AP MLD 110 and non-AP MLD 130. Under this DL negotiated TID-to-link mapping, all TIDs are mapped to the link set [Link AP1, Link AP2].

[0455] The same uplink TID-to-link mapping has been negotiated between AP MLD 110 and non-AP MLD 120, and between AP MLD 110 and non-AP MLD 130. Under this negotiated UL TID-to-link mapping, TIDs 0,3 and 1,2 are mapped to link AP1, and TIDs 4,5 and 6,7 are mapped to link AP2.

[0456] exist Figure 8 , both the non-AP MLDs 120 and 130 are EML active (i.e., EMLSR active or EMLMR active), wherein the EML links (i.e., EMLSR links or EMLMR links) correspond to the EML co-affiliated STAs 121 and 122 for the non-AP MLD 120, and the EML links (i.e., EMLSR links or EMLMR links) correspond to the EML co-affiliated STAs 131 and 132 for the non-AP MLD 130. The non-AP MLDs 120 and 130 have activated the EML mode and have indicated the EML links by sending an EML OM notification frame to the AP MLD 110 (steps 610, 710).

[0457] With respect to the EML links involved in the activated EML mode, both non-AP MLDs 120 and 130 apply the following rules specified by a particular embodiment of the present invention:

[0458] Rule 1: (Non-AP MLD) Under negotiated UL TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1, at least one of the EML links indicated in the EML link bitmap shall have at least one UL TID mapped.

[0459] Rule 2: (Non-AP MLD) Under negotiated UL TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 2, the EML link set indicated in the EML link bitmap shall not be disjoint from the link set to which all UL TIDs are mapped.

[0460] A variation (second formula) of Rule 1 is as follows: "Selecting the EML link set according to the UL TID-to-link mapping includes: satisfying a constraint that at least one EML link in the EML link set should have at least one UL TID mapped according to the UL TID-to-link mapping". According to this variation, the constraint (at least one EML link in the EML link set should have at least one UL TID mapped) is applied regardless of the UL TID-to-link mapping. Therefore, the first formula of Rule 1 (the case where the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with a TID-to-link mapping negotiation support subfield value equal to 1) is a special case of this variation.

[0461] A variation (second formula) of Rule 2 is as follows: "Selecting the EML link set according to the UL TID-to-link mapping includes: satisfying a constraint that the EML link set should not be disjoint with another link set, wherein all UL TIDs are mapped to respective links in the another link set according to the UL TID-to-link mapping". According to this variation, the constraint (the EML link set should not be disjoint with the another link set) is applied regardless of the UL TID-to-link mapping. Therefore, the first formula of Rule 2 (the case where the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with a TID-to-link mapping negotiation support subfield value equal to 1) is a special case of this variation.

[0462] In this Figure 8 In the present embodiment, the AP MLD 110, the non-AP MLD 120 and the non-AP MLD 130 are considered to be operating under "current EML operation" using the new rules specified above (steps 630-635, 740-745). This means that some MLDs have set the Link Indication subfield for UL EML frame exchange support to 0 during ML setup (steps 600, 700), or set the Link Indication subfield for UL EML frame exchange mode to 0 when activating EML mode (step 610) or when initiating UL EML frame exchange (step 740).

[0463] At the start of the sequence, both non-AP MLDs 120 and 130 are in the EML listening operation state, which means that the EML co-affiliated STAs 121 and 122 of the non-AP MLD 120 are both in the listening operation states 241 and 242, and the EML co-affiliated STAs 131 and 132 of the non-AP MLD 130 are both in the listening operation states 243 and 244.

[0464] When the AP MLD 110 desires to initiate a frame exchange sequence with the non-AP MLDs A 120 and B 130 to know their BSRs, the AP MLD 110 transmits a BSRP trigger frame 845 (step 740) through its subordinate AP AP1 111 as an initial control frame or initial frame received by the EML co-affiliated STA A1 121 of the non-AP MLD 120 and the EML co-affiliated STA B1 131 of the non-AP MLD 130. The BSRP trigger frame 845 schedules both the non-AP MLD A 120 and the non-AP MLD B 130.

[0465] With respect to the transmitted BSRP frame 845, AP MLD 110 has applied the following rules specified by a particular embodiment of the present invention:

[0466] Rule 3: (AP MLD) Under negotiated UL TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1, BSRP TF shall be transmitted on the EML link with at least one UL TID mapped.

[0467] A variation (second formula) of Rule 3 is as follows: "Transmit a buffer status report poll (BSRP) trigger frame (TF) to a non-AP MLD on a first enabling link (e.g., a first EML link) to which at least one UL TID is mapped according to the UL TID-to-link mapping". This variation is applied regardless of the UL TID-to-link mapping. Therefore, the first formula of Rule 3 (the case where the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with a TID-to-link mapping negotiation support subfield value equal to 1) is a special case of this variation.

[0468] In both non-AP MLDs 120 and 130, the reception of the BSRP trigger frame 845 initiates an EML switch 270 (step 630) (corresponding to the EMLSR active switch delay or the EMLMR active switch delay as described above). Operating under the current EML operation, both non-AP MLDs 120 and 130 initiate the switch of their received EML co-affiliated STA A1 121 and STA B1 131 to the enabled frame exchange state on the link receiving the BSRP TF; in parallel (synchronously), both non-AP MLDs 120 and 130 initiate the switch of their other EML co-affiliated STA A2 122 and STA B2 132 to the disabled frame exchange state on another link.

[0469] On the other hand, in response to the BSRP TF 845, the receiving EML co-affiliated STA A1121 of the scheduled non-AP MLD A120 transmits a BSR 846 for indicating the amount of buffered uplink data of the scheduled non-AP MLD A 120 (step 631), and the receiving EML co-affiliated STA B1131 of the scheduled non-AP MLD B 130 transmits a BSR 847 for indicating the amount of buffered uplink data of the scheduled non-AP MLDB 130.

[0470] With respect to transmitted BSR frames 846 and 847, both non-AP MLDs 120 and 130 apply the following rules specified by a particular embodiment of the present invention:

[0471] Rule 4: (Non-AP MLD) Under negotiated UL TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1, the response to the BSRP TF shall report the buffered traffic (if any) for at least one TID mapped on the EML link where the BSRP TF was received.

[0472] A variation (second formula) of Rule 4 is as follows: "The BSR frame reports buffered traffic (if any) for at least one UL TID mapped on the first EML link according to the UL TID-to-link mapping". This variation applies regardless of the UL TID-to-link mapping. Therefore, the first formula of Rule 4 (the case where the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with the TID-to-link mapping negotiation support subfield value equal to 1) is a special case of this variation.

[0473] Another variation of Rule 4 (the third formula) is as follows: "The BSR frame reports only the buffered traffic (if any) of one or more UL TIDs mapped on the first EML link according to the UL TID-to-link mapping". This another variation is applied regardless of the UL TID-to-link mapping. However, in a specific implementation of this another variation, the condition for application is that the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with the TID-to-link mapping negotiation support subfield value equal to 1.

[0474] According to this rule, the BSR 846 transmitted by the non-AP MLD 120 on the link AP1 that received the BSRP TF 845 indicates the amount of buffered uplink data for TIDs 0, 3. Similarly, according to this rule, the BSR 847 transmitted by the non-AP MLD 130 on the link AP1 that received the BSRP TF 845 indicates the amount of buffered uplink data for TIDs 1, 2.

[0475] Refer to the previously described Figure 3 , as an example, BSR 846 and 847 may use 802.11ax BSR format 460:

[0476] - For BSR 846, the ACI Bitmap subfield 461 is set to a value of "0100" to indicate buffered data for AC1, the Incremental TID subfield 462 is set to a value of "01" to indicate buffered data for 2 TIDs, and the Queue Size Total subfield 466 is set to a value corresponding to the total amount of buffered data for these 2 TIDs (i.e., TID 0, 3).

[0477] - For BSR 847, the ACI Bitmap subfield 461 is set to a value of "1000" to indicate buffered data for AC0, the Incremental TID subfield 462 is set to a value of "01" to indicate buffered data for 2 TIDs, and the Queue Size Total subfield 466 is set to a value corresponding to the total amount of buffered data for these 2 TIDs (i.e., TID 1, 2).

[0478] After the EML switching delay 270, both the scheduled non-AP MLD 120 and the non-AP MLD 130 have completed their switching from the EML listening operation mode to the EML frame exchange mode (step 632), which means that the receiving EML co-affiliated STAs A1 121 and B1 131 have switched from the listening operation states 241, 243 to the enabled frame exchange states 251, 253 on link AP1, respectively (step 633), while the other EML co-affiliated STAs A2 122 and B2 132 have switched from the listening operation states 242, 244 to the disabled frame exchange states 252, 254 on link AP2, respectively (634).

[0479] Frames 855 may then be exchanged with the subordinate AP AP1 111 within the initiated frame exchange sequence, i.e., on link AP1 (link #1) (steps 635, 743-744). Various types of frames 855 may be used (e.g., downlink HE MU PPDU or basic TF frame triggering MU UL OFDMA communication).

[0480] With respect to the basic trigger frame 855, the AP MLD 110 has applied the following rules specified by a particular embodiment of the present invention:

[0481] Rule 5: (AP MLD) Under negotiated UL TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1, the basic TF shall indicate the value of the AC corresponding to the UL TID mapped on the link transmitting / receiving the basic TF in the preferred AC subfield of its trigger-related user information subfield.

[0482] A variation (second formula) of Rule 5 is as follows: "The base TF schedules UL resources to the non-AP MLD and includes constraints on data to be transmitted within the scheduled UL resources based on the UL TID-to-link mapping". This variation is referenced regardless of the UL TID-to-link mapping. Therefore, the first formula of Rule 5 (the case where the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with the TID-to-link mapping negotiation support subfield value equal to 1) is a special case of this variation.

[0483] In a specific implementation of this variant, the constraints on data to be transmitted within the scheduled UL resources are indicated by a value of an access category (AC), the access category AC corresponding to the UL TID mapped on the first enabling link (e.g., the first EML link) according to the UL TID to link mapping. Preferably, the value is indicated in the preferred AC subfield of the trigger-related user information field of the user information field corresponding to the scheduled UL resources within the basic TF. Also preferably, if the UL TID to link mapping is a negotiated UL TID to link mapping with the TID to link mapping negotiation support subfield value equal to 1, the constraints on data to be transmitted by the non-AP MLD are applied.

[0484] AP MLD 110 transmits a basic TF 855 containing RU allocation information indicating that resource units are assigned to scheduled non-AP MLD A 120 and non-AP MLD B 130 through subordinate AP 111:

[0485] - Thus, non-AP MLD A 120 is scheduled (more generally, explicitly triggered) by frame 855 and may then proceed with a ULEML frame exchange by providing a response (here an EHT TB PPDU 856 collecting UL buffered data for the TID reported in the BSR 846).

[0486] - Thus, the non-AP MLD A130 is scheduled (more generally, explicitly triggered) by frame 855 and can then proceed with the ULEML frame exchange by providing a response (here an EHT TB PPDU 857 collecting UL buffered data for the TID reported in the BSR 847).

[0487] In other words, the BSRP trigger frame 845 is an initial frame that triggers a frame exchange sequence on the first EML link, and the method includes, at the non-AP station:

[0488] - obtaining scheduled UL resources within a frame exchange sequence; and

[0489] - Transmitting data within the scheduled UL resources with a UL TID mapped on the first EML link according to the UL TID to link mapping as reported in the BSR frame.

[0490] Then, the AP MLD 110 transmits a block acknowledgement frame 858 through the subordinate AP 111 for knowing that the EHT TB PPDUs 856 and 857 are received.

[0491] Upon detecting the end of the frame exchange, e.g. after block confirmation 858 (steps 650, 745), non-AP MLD A 120 and non-AP MLD B 130 initiate an EML switch back 271 to the EML listening operation mode (step 655): the receiving EML co-affiliated STAs A1 121 and B1 131 switch from the enabled frame exchange states 251, 253 back to the listening operation states 241, 243; the other EML co-affiliated STAs A2 122 and B2 132 switch from the disabled frame exchange states 252, 254 back to the listening operation states 242, 244.

[0492] As described above, the EML switch back 271 corresponds to an EMLSR transition delay or an EMLMR delay.

[0493] Fig. 9 The exemplary sequence of frame exchanges between an EML-capable AP MLD and an EML-capable non-AP MLD is schematically illustrated. Figure 6 and Figure 7 The flowchart of FIG. 1 handles a second possible operation.

[0494] In this Fig. 9 In the context of MU UL OFDMA transmission, the initial control frame or initial frame is a BSRP trigger frame, and the initial control frame response or initial frame response is a BSR frame.

[0495] and Figure 2 and Figure 8 Like reference numerals correspond to like frames / states, etc.

[0496] Again, the AP MLD 110 includes two subordinate APs 111 and 112 , the non-AP MLD 120 includes two subordinate STAs 121 and 122 , and the non-AP MLD 130 includes two subordinate STAs 131 and 132 .

[0497] In this Fig. 9 , it is assumed that two subordinate STAs 121 and 122 of the non-AP MLD 120 and two subordinate STAs 131 and 132 of the non-AP MLD 130 are able to transmit a BSR frame while being in a listening operation state.

[0498] In this Fig. 9 In the embodiment of FIG. 1 , unless explicitly indicated, the negotiated TID-to-link mappings assumed to be first between the AP MLD 110 and the non-AP MLD 120 and secondly between the AP MLD 110 and the non-AP MLD 130 are those previously referenced. Figure 8 Descriptive.

[0499] exist Fig. 9In the embodiment, both the non-AP MLDs 120 and 130 are EML active (i.e., EMLSR active or EMLMR active), wherein the EML links (i.e., EMLSR links or EMLMR links) correspond to the EML co-affiliated STAs 121 and 122 of the non-AP MLD 120, and the EML links (i.e., EMLSR links or EMLMR links) correspond to the EML co-affiliated STAs 131 and 132 of the non-AP MLD 130. The non-AP MLDs 120 and 130 have activated the EML mode and indicate the EML links by sending an EMLOM notification frame to the AP MLD 110 (steps 610, 710).

[0500] In this Fig. 9 In the above, the AP MLD 110, the non-AP MLD 120 and the non-AP MLD 130 are considered to operate under the "new EML operation" as defined above (steps 640-645, 750-756). This means that the MLD has set the Link Indication subfield for UL EML frame exchange support to 1 during ML setup (steps 600, 700), and set the Link Indication subfield for UL EML frame exchange mode to 1 when activating EML mode (step 610) or when initiating UL EML frame exchange (step 750).

[0501] At the start of the sequence, both non-AP MLDs 120 and 130 are in the EML listening operation state, which means that the EML co-affiliated STAs 121 and 122 of the non-AP MLD 120 are both in the listening operation states 241 and 242, and the EML co-affiliated STAs 131 and 132 of the non-AP MLD 130 are both in the listening operation states 243 and 244.

[0502] When the AP MLD 110 desires to initiate a frame exchange sequence with the non-AP MLDs A 120 and B 130 to know their BSRs, the AP MLD 110 transmits a BSRP trigger frame 945 (step 750) through its subordinate AP AP1 111 as an initial control frame or initial frame received by the EML co-affiliated STA A1 121 of the non-AP MLD 120 and the EML co-affiliated STA B1 131 of the non-AP MLD 130. The BSRP trigger frame 945 schedules both the non-AP MLD A 120 and the non-AP MLD B 130.

[0503] In both non-AP MLDs 120 and 130, the reception of the BSRP trigger frame 945 initiates an EML handover 270 (step 640) (corresponding to the EMLSR active handover delay or EMLMR active handover delay as previously described). Operating under the new EML operation, both non-AP MLDs 120 and 130, in response to the BSRP trigger frame 945, initiate handover of their respective EML co-affiliated STA A1 121, 122 and STA B1 131, 132 based on the contents of their respective BSR frames 946, 947 in preparation prior to transmission:

[0504] - The BSR 946 being prepared by the non-AP MLD 120 indicates the amount of buffered uplink data mapped to TID 0, 3 of link AP1, and the non-AP MLD 120 initiates the switching of its receiving EML co-affiliated STA A1 121 from the listening operation state to the enabled frame exchange state on link AP1. In parallel (synchronously), the non-AP MLD 120 initiates the switching of its other EML co-affiliated STA A2 122 from the listening operation state to the disabled frame exchange state on another link.

[0505] - The BSR 947 being prepared by the non-AP MLD 130 indicates the amount of buffered uplink data mapped to TID 4, 5 of link AP2, and the non-AP MLD 130 initiates the switching of its other EML co-affiliated STA B2 132 from the listening operation state to the enabled frame exchange state on link AP2. In other words, the selected EML link (link AP2) is a second EML link in the EML link set that is different from the first EML link (link AP1), where the BSRP trigger frame is received and the BSR frame is transmitted on the first EML link (link AP1), and the non-AP switches the first STA (STAB2) affiliated to the non-AP MLD and corresponding to the selected EML link (link AP2) from the listening operation state to the enabled frame exchange state. In parallel (synchronously), the non-AP MLD 130 initiates the switching of its receiving EML co-affiliated STA B1 131 from the listening operation state to the disabled frame exchange state on another link.

[0506] Now considering another TID-to-mapping, such as the default TID-to-link mapping or a negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 2, the prepared BSRs 946 and 947 may indicate the link to be used for EML frame exchange (i.e., the preferred link) as follows:

[0507] - The BSR 946 prepared by the non-AP MLD 120 is as previously referenced Figure 4a or Figure 4bThe format of the ML-BSR described in the foregoing description. The ML-BSR indicates the amount of buffered uplink data mapped to TIDs 0, 3 of both link AP1 and link AP2, and indicates link AP1. Then, the non-AP MLD 120 initiates a switch of its receiving EML co-affiliated STA A1 121 from the listening operation state to the enabled frame exchange state on link AP1. In parallel (synchronously), the non-AP MLD 120 initiates a switch of its other EML co-affiliated STA A2 122 from the listening operation state to the disabled frame exchange state on another link.

[0508] - The BSR 947 prepared by the non-AP MLD 130 is as previously referenced Figure 4a or Figure 4b The format of the ML-BSR described in the foregoing description. The ML-BSR indicates the amount of buffered uplink data mapped to TIDs 4, 5 of both link AP1 and link AP2, and indicates link AP2. Then, the non-AP MLD 130 initiates a switch of its other EML co-affiliated STA B2 132 from the listening operation state to the enabled frame exchange state on link AP2. In parallel (synchronously), the non-AP MLD 130 initiates a switch of its receiving EML co-affiliated STA B1 131 from the listening operation state to the disabled frame exchange state on another link.

[0509] Under this new EML operation, the link to be used for EML frame exchange for a given non-AP MLD is based on the contents of the BSR frame:

[0510] - The link to be used for frame exchange may be implicitly indicated by the TID reported in the BSR and the knowledge of the uplink TID-to-link mapping. This implicit indication may be particularly relevant in case of a negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1.

[0511] - The link to be used for frame exchange may be explicitly indicated by the link ID indicated in the BSR, which is an ML-BSR. This explicit indication is particularly relevant under the default TID-to-link mapping or under a negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 2.

[0512] Once the preparation of BSRs 946, 947 is completed in response to the BSRP TF 945, the receiving EML co-affiliated STA A1 121 of the scheduled non-AP MLD A 120 transmits a BSR 946 indicating the amount of buffered uplink data of the scheduled non-AP MLD A 120 (step 641), and the receiving EML co-affiliated STA B1 131 of the scheduled non-AP MLD B 130 transmits a BSR 947 indicating the amount of buffered uplink data of the scheduled non-AP MLD B 130 (step 641).

[0513] With respect to the transmitted BSR frames 946 and 947, both the AP MLD 110 and the non-AP MLDs 120 and 130 have applied the following rules specified by a particular embodiment of the present invention:

[0514] Rule 6: (Non-AP MLD) After receiving the BSRP TF that initiated the UL EML frame exchange and transmitting a BSR frame as a response to the BSRP TF, the non-AP MLD shall be able to transmit or receive frames on the EML links implicitly or explicitly indicated in the BSR frame, and shall not transmit or receive on one or more other EML links until the end of the frame exchange.

[0515] Rule 7: (AP MLD) After sending a BSRP TF for initiating UL EML frame exchange with at least one non-AP MLD and receiving a BSR frame as a response to the BSRP TF, the AP MLD shall be able to trigger uplink frame exchange with the non-AP MLD on the EML link implicitly or explicitly indicated in the BSR frame.

[0516] Rule 8: (MLD, i.e., non-AP MLD and AP MLD) In ​​case of implicit EML link indication in the BSR, the MLD identifies the EML link to be used for frame exchange by knowledge of the one or more TIDs reported in the BSR and the TID-to-link mapping. In other words, the selected EML link is implicit in the one or more TIDs reported in the BSR frame in view of the UL TID-to-link mapping. In a specific embodiment, the reported one or more TIDs are mapped on the second EML link in the EML link set instead of being mapped on the first EML link.

[0517] For Rule 8, the following applies:

[0518] * The TID reported in the BSR frame should preferably be mapped to the same EML link:

[0519] (No ambiguity, several TIDs reported) Under negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1, if the reported TIDs are mapped to the same EML link, the EML link to be used for frame exchange is the same EML link (i.e., the receiving EML link or another link).

[0520] * Otherwise, the following applies:

[0521] (Ambiguous, since all reported TIDs are mapped to all EML links) Under the default TID-to-mapping or under negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 2, the EML link to be used for frame exchange is the receiving EML link (i.e., BSRP TF is received).

[0522] (Ambiguous, since at least two reported TIDs are mapped to at least two different EML links) Under the negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1, if at least two reported TIDs are mapped to at least two different EML links, the EML link to be used for frame exchange is the receiving EML link (i.e., the BSRP TF is received).

[0523] Rule 9: (MLD) In ​​case of explicit EML link indication in BSR, MLD identifies the EML link to be used for frame exchange by the link ID indicated in BSR (ML-BSR). In other words, the selected EML link is explicitly indicated by the link identifier (link ID) in the BSR frame.

[0524] Refer to the previously described Figure 3 , as an example, BSR 946 and 947 may use 802.11ax BSR format 460:

[0525] -For BSR 946, the ACI Bitmap subfield 461 is set to a value of "0100" to indicate buffered data for AC1, the Incremental TID subfield 462 is set to a value of "01" to indicate buffered data for 2 TIDs, and the Queue Size Total subfield 466 is set to a value corresponding to the total amount of buffered data for these 2 TIDs (i.e., TIDs 0, 3 mapped to link AP1).

[0526] -For BSR 947, the ACI Bitmap subfield 461 is set to a value of "0010" to indicate buffered data for AC2, the Incremental TID subfield 462 is set to a value of "01" to indicate buffered data for 2 TIDs, and the Queue Size Total subfield 466 is set to a value corresponding to the total amount of buffered data for these 2 TIDs (i.e., TIDs 4, 5 mapped to link AP2).

[0527] In this case, using the 802.11ax BSR format, AP MLD 110 and non-AP MLD 120 use the TID reported in BSR946 and the previously referenced Figure 8 Similarly, using the 802.11ax BSR format, AP MLD 110 and non-AP MLD 130 use the TID reported in BSR947 and the previously referenced Figure 8 The knowledge of the uplink TID to link mapping described is used to identify the EML link AP2 to be used for frame exchange.

[0528] After the EML switching delay 270, both the scheduled non-AP MLD 120 and the non-AP MLD 130 have completed their switching from the EML listening operation mode to the EML frame exchange mode (step 642), which means that the receiving EML co-affiliated STA A1 121 and the other EML co-affiliated STA B2 132 have respectively switched from the listening operation state 241, 244 to the enabled frame exchange state 251, 953 on link AP1 and link AP2 (steps 643, 644), while the receiving EML co-affiliated STA B1 131 and the other EML co-affiliated STA A2 122 have respectively switched from the listening operation state 243, 242 to the disabled frame exchange state 954, 253 on link AP1 and link AP2 (steps 643, 644).

[0529] Frames 955 may then be exchanged with the subordinate AP AP1 111 within the initiated frame exchange sequence, i.e., on link AP1 (link #1) (steps 645, 743-745). Various types of frames 955 may be used (e.g., downlink HE MU PPDU or basic TF frame triggering MU UL OFDMA communication).

[0530] Similarly, frames 955' may then be exchanged with the attached AP AP2 112 on link AP1 (another link) within the initiated frame exchange sequence (steps 645, 754-755). Various types of frames 955' may be used (e.g., downlink HEMU PPDU or basic TF frames to trigger MU UL OFDMA communications).

[0531] The AP MLD 110 transmits a basic TF 955 containing RU allocation information indicating that resource units are assigned to the scheduled non-APMLD 120 through the subordinate AP AP1 111:

[0532] - Thus, non-AP MLD A 120 is scheduled (more generally, explicitly triggered) by frame 955 and may then proceed with a ULEML frame exchange by providing a response (here an EHT TB PPDU 956 collecting UL buffered data for the TID reported in the BSR 946).

[0533] Then, the AP MLD 110 transmits a block acknowledgement frame 958 through the subordinate AP AP1 111 for knowing that the EHT TB PPDU 956 is received.

[0534] Upon detecting the end of the frame exchange, e.g., after block confirmation 958 (steps 650, 745), non-AP MLD A120 initiates an EML switch back to 271 the EML listening operation state (step 655): the receiving EML co-affiliated STA A1 121 switches from the enabled frame exchange state 251 back to the listening operation state 241; the other EML co-affiliated STA A2 122 switches from the disabled frame exchange state 252 back to the listening operation state 242.

[0535] As described above, the EML switch back 271 corresponds to an EMLSR transition delay or an EMLMR delay.

[0536] In parallel, AP MLD 110 transmits a basic TF 955' containing RU allocation information indicating that resource units are assigned to the scheduled non-AP MLD A 130 through the subordinate AP AP2 112:

[0537] - Thus, non-AP MLD A 130 is scheduled (more generally, explicitly triggered) by frame 955' and may then proceed with UL EML frame exchange by providing a response (here an EHT TB PPDU 956' collecting UL buffered data for the TID reported in BSR 947).

[0538] Variant “MU-RTS / CTS”: Here, in a variant, prior to the transmission of the basic TF 955′, the AP MLD 110 transmits a MU-RTS TF 960 via the attached AP AP2 112, and the non-AP MLD 130 responds with a CTS frame 961 via the attached non-AP MLD 132. This relates to the IEEE standard 802.11ax. TM-The so-called MU-RTS / CTS procedure introduced in UE-2021 and corresponds to an extension of the RTS / CTS handshake mechanism for reserving channels in multi-user UL / DL scenarios. An AP is allowed to reserve a TXOP for multi-user transmission by sending a multi-user request control frame (referred to as a MU-RTS frame) to request reservation of one or more 20MHz communication channels. In response to the MU-RTS frame, the solicited / intended STA sends a CTS frame. In this variant, the MU-RTS frame 960 may constitute an initial control frame or initial frame on link AP2, thereby permitting some other EML active non-AP MLDs to be triggered in an upcoming UL EML frame exchange on link AP2. The MU-RTS / CTS procedure may also permit NAV protection of link AP2 (i.e., neighboring stations set their network allocation vectors (NAVs) to prevent them from initiating any transmission opportunities) before the upcoming UL EML frame exchange by using a basic frame that can be decoded by legacy stations.

[0539] This variant "MU-RTS / CTS" (the initial frame is a MU-RTS frame) can be summarized as follows:

[0540] - at the non-AP MLD: on a second link (link AP2) different from the first EML link (link AP1) on which the BSRP trigger frame (945) is received, before receiving a basic trigger frame (955') for scheduling UL resources to the non-AP MLD within the frame exchange sequence, receiving an initial frame (960) triggering the frame exchange sequence on the second link;

[0541] - At AP MLD: on a second EML link (link AP2) different from the first EML link (link AP1) on which the BSRP trigger frame (945) is transmitted, before transmitting a basic trigger frame (955') that schedules UL resources to the non-AP MLD within the frame exchange sequence, transmitting an initial frame (960) that triggers the frame exchange sequence on the second link.

[0542] In a specific embodiment (variant "MU-RTS / CTS" or generalization thereof), the initial frame contains an invitation to other non-AP MLDs to be triggered in an incoming UL EML frame exchange on the second EML link.

[0543] Then (return Fig. 9 ), the AP MLD 110 transmits a block ACK frame 958' through the subordinate AP AP2 112 to acknowledge receipt of the EHT TBPPDU 956'.

[0544] Upon detecting the end of the frame exchange, e.g., after the block confirmation 958′ (steps 650, 756), the non-AP MLD B130 initiates an EML switch back to the 271 EML listening operation state (step 655): the receiving EML co-affiliated STA B1 131 switches from the disabled frame exchange state 954 back to the listening operation state 243; the other EML co-affiliated STA B2 132 switches from the enabled frame exchange state 953 back to the listening operation state 244.

[0545] As described above, the EML switch back 271 corresponds to an EMLSR transition delay or an EMLMR delay.

[0546] Fig.10 Considering the case of an EML active non-AP MLD with certain constraints on the transmission of BSR frames, the reference Fig. 9 A variation of the second possible operation is shown.

[0547] and Figure 2 and Fig. 9 Like reference numerals correspond to like frames / states, etc.

[0548] Again, the AP MLD 110 includes two subordinate APs 111 and 112 , the non-AP MLD 120 includes two subordinate STAs 121 and 122 , and the non-AP MLD 130 includes two subordinate STAs 131 and 132 .

[0549] In this Fig.10 In contrast to the previously described Figure 8 and Fig. 9 In contrast, it is assumed that the two subordinate STAs 121 and 122 of the non-AP MLD 120 and the two subordinate STAs 131 and 132 of the non-AP MLD 130 cannot send BSR frames when in the listening operation state; it is assumed that these STAs need to have completed their EML switching 1070 and are in the frame exchange enabled state to be able to send BSR frames.

[0550] This variation may reflect some constraints related to the hardware implementation of non-AP MLDs 120 and 130 .

[0551] In this Fig.10 The concept of the new EML operation mode of the embodiment of the present invention is similar to that of the previous reference Fig. 9 The concepts described are the same. Therefore, they will not be described in detail here, but only the implications related to the new assumptions for BSR transmission will be described.

[0552] When the AP MLD 110 desires to initiate a frame exchange sequence with the non-AP MLDs A 120 and B 130 to know their BSRs, the AP MLD 110 transmits a BSRP trigger frame 945 as an initial control frame or initial frame through its subordinate AP AP1 111, which is received by the EML co-affiliated STA A1 121 of the non-AP MLD 120 and the EML co-affiliated STA B1 131 of the non-AP MLD 130. The BSRP trigger frame 945 schedules both the non-AP MLD A 120 and the non-AP MLD B 130.

[0553] In both non-AP MLDs 120 and 130, the reception of the BSRP trigger frame 945 initiates an EML switch 1070 (corresponding to the EMLSR stuffing delay or EMLMR delay as previously described). Operating under the new EML operation, but constrained to send BSR frames when in the enabled frame exchange state, both non-AP MLDs 120 and 130 initiate a switch of their respective receive EML co-affiliated STA A1 121 and STA B1 131 from their listening operation states 241, 243 to their enabled frame exchange states 251, 1053 on the link (i.e., link AP1) where the BSRP TF 945 was received, while both non-AP MLDs 120 and 130 initiate a switch of their respective other EML co-affiliated STA A2 122 and STA B2 132 from their listening operation states 242, 244 to their disabled frame exchange states 252, 1054 on the other link (i.e., link AP2).

[0554] After the EML switching delay 1070, both the scheduled non-AP MLD 120 and the non-AP MLD 130 have completed their switching. Then, in response to the BSRP TF 945, the receiving EML co-affiliated STA A1121 of the scheduled non-AP MLD A 120 transmits a BSR 946 for indicating the amount of buffered uplink data of the scheduled non-AP MLD A 120, and the receiving EML co-affiliated STA B1131 of the scheduled non-AP MLD B 130 transmits a BSR 947 for indicating the amount of buffered uplink data of the scheduled non-AP MLD B 130.

[0555] Both non-AP MLDs 120 and 130 may then initiate or not initiate subsequent handover of their respective EML co-affiliated STAs A1 121, A2 122 and STAs B1 131, B2 132 based on the content of their respective BSR frames 946, 947 transmitted on the link (i.e., link AP1) where the BSRP TF was received:

[0556] - The BSR 946 transmitted by the non-AP MLD 120 indicates that the amount of buffered uplink data for TIDs 0,3 is mapped to link AP1, the non-AP MLD 120 remains in the same state and does not need to initiate subsequent handover of its EML co-affiliated STA A1 121 and STA A2 122.

[0557] - The BSR 947 transmitted by the non-AP MLD 130 indicates that the amount of buffered uplink data for TIDs 4, 5 is mapped to link AP2, and the non-AP MLD 130 needs to initiate a subsequent switch of its EML co-affiliated STAs B1 131 and B2 132. The non-AP MLD 130 then initiates a subsequent EML switch 1070' to switch its other EML co-affiliated STA B2 132 from the disabled operation state 1054 to the enabled frame exchange state 953 on link AP2. In parallel (synchronously), the non-AP MLD 130 initiates a subsequent switch of its receiving EML co-affiliated STA B1 131 from the enabled frame exchange state 1053 to the disabled frame exchange state 954 on link AP1.

[0558] The remainder of the frame exchange sequence is consistent with the previous reference Fig. 9 The description is the same, so it will not be described here again.

[0559] It should be pointed out that as Fig. 9 variant Fig.10 Not Figure 6 and Figure 7 However, if necessary, those skilled in the art will be able to adapt these flow charts for complete treatment of this variant.

[0560] Fig.11 The architecture of the EMLSR capability for MLD is schematically illustrated. The figure takes an example of two affiliated non-AP STAs sharing the hardware resources of their non-AP MLD when the EMLSR mode is activated. The EMLSR capability architecture for MLD presented in this figure is for illustration purposes only, and other alternative architectures can be envisioned.

[0561] The architecture includes two radio stacks, a light radio stack and a full radio stack.

[0562] The full radio stack includes a full 802.11be MAC module 800a (exchanging data with higher layers), a full 802.11be PHY module 805a connected to the full MAC module, a full RF chain 815a connected to the full PHY module, and an antenna 820a connected to the full RF chain through an EMLSR switch 810.

[0563] The light radio stack includes a light 802.11be MAC module 800b (exchanging data with higher layers), a light 802.11be PHY module 805b connected to the light MAC module, a light RF chain 815b connected to the light PHY module, and an antenna 820b connected to the light RF chain through an EMLSR switch 810.

[0564] The EMLSR switch 810 is shared by both radio stacks and is configured to switch the EMLSR co-affiliated STAs from a listening operation state to an enabled or disabled frame exchange state / from an enabled or disabled frame exchange state to a listening operation state when the EMLSR mode is activated.

[0565] Radio chain 800a / 805a / 815a is a full radio resource that allows reception and transmission of any IEEE802.11 frame. In particular, radio chain 800a / 805a / 815a includes a coding and decoding module that encodes and decodes any IEEE802.11 frame. On the other hand, radio chain 800b / 805b / 815b is a reduced-function (or "light") radio resource that only allows reception and transmission of specific IEEE802.11 frames. In particular, radio chain 800b / 805b / 815b only includes a coding and decoding module that encodes and decodes specific frames using a rate of 6Mbps, 12Mbps or 24Mbps.

[0566] The lower left figure illustrates the function of the MLD when the non-AP MLD is in the EMLSR listening mode of operation: the common EMLSR switch 810 connects the individual radio chains 800a / 805a / 815a and 800b / 805b / 815b to antennas 820a and 820b, respectively. Therefore, the individual radio stacks can be used to listen to the corresponding links simultaneously. As shown, two links are available. The full radio chain 800a / 805a / 815a and antenna 820a are configured to operate on link 1, and the light radio chain 800b / 805b / 815b and antenna 820b are configured to operate on link 2.

[0567] The bottom center diagram illustrates the function of MLD when non-AP MLD switches to the first EMLSR frame exchange mode. The EMLSR common subsidiary STA corresponding to link 1 is in the enabled frame exchange state, and the other EMLSR common subsidiary STA corresponding to link 2 is in the disabled frame exchange state. In this case, the common EMLSR switch 810 connects the full radio chain 800a / 805a / 815a to both antennas 820a and 820b, and the full radio chain 800a / 805a / 815a and antenna 820a / 820b are configured to operate on link 1. Here, since the full radio chain reservation is configured to operate on link 1, the EMLSR switching duration from the listening operation state to the enabled frame exchange state can be considered to be short. In fact, in this case, the switch only involves antenna switching. On the other hand, the common EMLSR switch 810 disconnects the light radio chain 800b / 805b / 815b from the antenna 820b. In this configuration, the light radio chain 800b / 805b / 815b cannot receive or transmit any frames on link 2. Then, only link 1 is available.

[0568] The figure at the lower right illustrates the function of MLD when non-AP MLD switches to the second EMLSR frame exchange mode. The EMLSR common subsidiary STA corresponding to link 2 is in the enabled frame exchange state, and the other EMLSR common subsidiary STA corresponding to link 1 is in the disabled frame exchange state. In this case, the common EMLSR switch 810 connects the full radio chain 800a / 805a / 815a to both antennas 820a and 820b, and the full radio chain 800a / 805a / 815a and antenna 820a / 820b are configured to operate on link 2. Here, since the full radio chain is switched to operate on link 2, the EMLSR switching duration from the listening operation state to the enabled frame exchange state can be considered to be long. In fact, in this case, the switching involves both antenna switching and full radio chain configuration switching. On the other hand, the common EMLSR switch 810 disconnects the light radio chain 800b / 805b / 815b from the antenna 820b. In this configuration, the light radio chain 800b / 805b / 815b cannot receive or transmit any frames on link 1. Then, only link 2 is available.

[0569] The functionality of the common EMLSR switch 810 clearly shows that the state changes of two EMLSR common affiliated STAs in the same MLD are necessarily simultaneous, since antenna resources are connected to either one of the STAs or the other, but never remain available for both STAs at the same time.

[0570] Fig.12The EMLMR capability architecture for MLD is schematically illustrated. The figure takes an example where two affiliated non-AP STAs share their antenna resources when the EMLMR mode is activated.

[0571] The architecture includes two radio stacks, one for each non-AP STA.

[0572] The radio stack includes a full 802.11be MAC module 900a or 900b (exchanging data with higher layers), a full 802.11be PHY module 905a or 905b connected to the MAC module, a radio frequency chain 915a or 915b connected to the PHY module, an EMLMR switch 910 shared by the two radio stacks and configured to aggregate antenna resources when the EMLMR mode is activated, and an antenna array 920a or 920b.

[0573] The lower left diagram illustrates the functionality when a non-AP MLD is listening to an initial frame: a common EMLMR switch 910 connects each antenna array to its RF chain. Thus, each radio stack is complete and can serve the corresponding link using, for example, a 2×2 MIMO antenna configuration. As shown, two links are available.

[0574] The bottom center figure illustrates the functionality of the MLD when the non-AP MLD switches to the first EMLMR frame exchange mode. The EMLMR co-affiliated STA corresponding to link 2 is in an enabled frame exchange state, while the other EMLMR co-affiliated STA corresponding to link 1 is in a disabled frame exchange state. The common EMLMR switch 910 aggregates antenna resources to link 2. To this end, the common EMLMR switch 910 connects the antenna array 920a of the second radio stack to the RF chain 915b of the first radio stack. Therefore, the first radio stack can operate in a 4×4 MIMO antenna configuration to improve the throughput on link 2. On the other hand, link 1 can no longer be used because its antenna array 920a is no longer available for the second radio stack.

[0575] The lower right figure illustrates the function of the MLD when the non-AP MLD switches to the second EMLMR frame exchange mode. The EMLMR co-affiliated STA corresponding to link 1 is in an enabled frame exchange state, while the other EMLMR co-affiliated STA corresponding to link 2 is in a disabled frame exchange state. The common EMLMR switch 910 aggregates antenna resources to link 1. To this end, the common EMLMR switch 910 connects the antenna array 920b of the first radio stack to the RF chain 915a of the second radio stack. Therefore, the second radio stack can operate in a 4×4 MIMO antenna configuration to improve the throughput on link 1. On the other hand, link 2 can no longer be used because its antenna array 920b is no longer available for the first radio stack.

[0576] The functionality of the common EMLMR switch 910 clearly shows that the state changes of two EMLMR common affiliated STAs in the same MLD are necessarily simultaneous, since antenna resources are connected to either one of the STAs or the other, but never remain available for both STAs at the same time.

[0577] Fig.13 A communication device 1000 (typically any of the MLDs discussed above) configured to implement a wireless network of at least one embodiment of the present invention is schematically illustrated. The communication device 1000 may preferably be a device such as a microcomputer, a workstation, or a light portable device. The communication device 1000 includes a communication bus 1013, which is preferably connected to:

[0578] A central processing unit 1001 denoted as CPU, such as a processor;

[0579] Memory 1003, used to store executable codes of methods or method steps according to embodiments of the present invention, and registers suitable for recording variables and parameters required to implement these methods; and

[0580] At least two communication interfaces 1002 and 1002', which are connected to a wireless communication network (eg a communication network according to one of the IEEE 802.11 family of standards) via transmit and receive antennas 1004 and 1004', respectively.

[0581] Preferably, the communication bus 1013 provides communication and interoperability between the various elements included in or connected to the communication device 1000. The representation of a bus is not limiting, and in particular, the central processing unit is operable to communicate instructions to any element of the communication device 1000, either directly or through other elements of the communication device 1000.

[0582] The executable code may be stored in a memory (which may be a read-only hard disk) or on a removable digital medium (such as a disk). According to an optional variation, the executable code of the program may be received via interfaces 1002 and 1002' via a communication network to store the executable code in the memory of the communication device 1000 before execution.

[0583] In an embodiment, the apparatus is a programmable device that implements embodiments of the invention using software.Alternatively, however, embodiments of the invention may be implemented in whole or in part in hardware (eg in the form of an application specific integrated circuit or ASIC).

[0584] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the specific embodiments, and modifications within the scope of the present invention will be apparent to those skilled in the art.

[0585] When referring to the foregoing illustrative embodiments, those skilled in the art will appreciate many further modifications and variations, which are given by way of example only and are not intended to limit the scope of the invention, which is determined solely by the appended claims. In particular, different features from different embodiments may be interchangeable where appropriate.

[0586] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

Claims

1. A communication method in a wireless network, comprising: At a non-access point multi-link device (non-AP MLD) operating on a multi-link utilizing an uplink traffic identifier to link mapping (ULTID to link mapping), Activating an enhanced multi-link mode, namely, an EML mode, wherein activating the EML mode comprises: selecting an EML link set of EML links to which the EML mode is applied according to the UL TID-to-link mapping, and transmitting a notification specifying the selected EML link set to an AP MLD; and / or when the non-AP MLD operates in the EML mode with the EML link set, in response to a buffer status report polling trigger frame, namely, a BSRP trigger frame received from the AP MLD on a first EML link in the EML link set, transmitting a BSR frame to the AP MLD on the first EML link, wherein the BSR frame reports buffered traffic according to the UL TID-to-link mapping.

2. The method according to claim 1, wherein: Selecting the EML link set according to the UL TID-to-link mapping includes satisfying a constraint that at least one EML link in the EML link set should have at least one UL TID mapped according to the UL TID-to-link mapping.

3. The method according to claim 2, wherein: If the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with a TID-to-link mapping negotiation support subfield value equal to 1, a constraint is applied that at least one EML link in the EML link set should have at least one UL TID mapped.

4. The method according to claim 1, wherein: Selecting the EML link set according to the UL TID-to-link mapping includes satisfying a constraint that the EML link set should not be disjoint from another link set in which all UL TIDs are mapped on respective links according to the UL TID-to-link mapping.

5. The method according to claim 4, wherein: If the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with a TID-to-link mapping negotiation support subfield value equal to 2, a constraint is applied that EML links in the EML link set should not be disjoint with the another link set.

6. The method according to claim 1, wherein: If there is buffered traffic for at least one UL TID mapped on the first EML link according to the UL TID-to-link mapping, the BSR frame reports the buffered traffic.

7. The method according to claim 1, wherein: If there is buffered traffic for one or more UL TIDs mapped on the first EML link according to the UL TID-to-link mapping, the BSR frame only reports the buffered traffic.

8. The method according to claim 6 or 7, wherein: In case the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with a TID-to-link mapping negotiation support subfield value equal to 1, the following constraint applies: if there is buffered traffic for at least one UL TID mapped on the first EML link according to the UL TID-to-link mapping, the BSR frame reports the buffered traffic, or if there is buffered traffic for one or more UL TIDs mapped on the first EML link according to the UL TID-to-link mapping, the BSR frame only reports the buffered traffic.

9. The method according to claim 1, wherein: The BSRP trigger frame is an initial frame that triggers a frame exchange sequence on the first EML link, and the method further comprises, at the non-AP station: obtaining scheduled UL resources within the frame exchange sequence; and Data having a UL TID mapped on the first EML link according to the UL TID-to-link mapping as reported in the BSR frame is transmitted within the scheduled UL resources.

10. The method according to claim 1, further comprising: At the non-AP MLD, signaling information for indicating which of the following two sub-modes of the EML mode is to be used is transmitted to the AP MLD: a first sub-mode of the EML mode, the first sub-mode comprising the transmission of the BSR frame reporting buffered traffic according to the UL TID-to-link mapping; and A second sub-mode of the EML mode, in which the non-AP MLD transmits a BSR frame to the AP MLD on the first EML link in response to a BSRP trigger frame received from the AP MLD on the first EML link, the BSR frame indicating a selected EML link in the EML link set to be used for frame exchange.

11. A communication method in a wireless network, comprising: At a non-access point multi-link device (non-AP MLD) operating on a multi-link utilizing an uplink traffic identifier to link mapping (ULTID to link mapping), Receiving a buffer status report polling trigger frame (BSRP trigger frame) from the AP MLD on a first EML link in the EML link set to which the EML mode is applied; selecting, in the EML link set, an EML link to be used for frame exchange according to the UL TID-to-link mapping and the buffered traffic to be reported in the BSR frame; as well as The BSR frame indicating the selected EML link to be used for the frame exchange is transmitted to the AP MLD over the first EML link.

12. The method according to claim 11, wherein: The selected EML link is a second EML link in the set of EML links that is different from the first EML link, wherein the BSRP trigger frame is received and the BSR frame is transmitted on the first EML link.

13. The method according to claim 12, further comprising: At the non-AP MLD, after the transmission of the BSR frame, a first STA attached to the non-AP MLD and corresponding to the selected EML link is switched from a listening operation state or a frame exchange disabled state to a frame exchange enabled state.

14. The method according to claim 12, further comprising: At the non-AP MLD, on the second EML link different from the first EML link, before receiving a basic trigger frame for scheduling UL resources to the non-AP MLD within a frame exchange sequence, receiving an initial frame for triggering the frame exchange sequence on the second EML link, wherein the BSRP trigger frame is received on the first EML link.

15. The method according to claim 11, further comprising: At the non-AP MLD, the EML link set is selected according to the UL TID-to-link mapping, and a notification specifying the selected EML link set is transmitted to the AP MLD.

16. The method according to claim 11, further comprising: At the non-AP MLD, signaling information for indicating which of the following two sub-modes of the EML mode is to be used is transmitted to the AP MLD: a first sub-mode of the EML mode, in which, in response to a BSRP trigger frame received from the AP MLD on a given EML link in the set of EML links, the non-AP MLD transmits a BSR frame to the AP MLD on the given EML link, wherein if there is buffered traffic for at least one UL TID mapped on the given EML link according to the UL TID-to-link mapping, the BSR frame reports the buffered traffic; as well as A second sub-mode of the EML mode, the second sub-mode comprising the transmission of the BSR frame, the BSR frame indicating the selected EML link to be used for the frame exchange.

17. The method according to claim 10 or 16, wherein: The signaling information is contained in a subfield of an EML control field of an EML operation mode notification frame, ie, an EML OM notification frame, transmitted by the non-APMLD.

18. A communication method in a wireless network, comprising: At an AP MLD configured to perform a frame exchange operation with at least one non-access point multi-link device (i.e., at least one non-AP MLD) operating on a multi-link utilizing an uplink traffic identifier to link mapping (i.e., a UL TID to link mapping), Transmitting a buffer status report polling trigger frame (BSRP TF) to the non-AP MLD on the first enabling link; receiving a BSR frame reporting buffered traffic from the non-AP MLD on the first enabling link; as well as A basic TF is transmitted to the non-AP MLD over the first enabling link, the basic TF scheduling UL resources to the non-AP MLD and including constraints on data to be transmitted within the scheduled UL resources based on the UL TID-to-link mapping.

19. The method according to claim 18, wherein: The constraints on data to be transmitted within the scheduled UL resources are indicated by a value of an access category, ie, AC, corresponding to a UL TID mapped on the first enabling link according to the UL TID-to-link mapping.

20. The method according to claim 19, wherein: The value is indicated in a preferred AC subfield of a trigger-related user information field of a user information field corresponding to the scheduled UL resources within the basic TF.

21. The method according to claim 19, wherein: If the UL TID-to-link mapping is a negotiated UL TID-to-link mapping with a TID-to-link mapping negotiation support subfield value equal to 1, then constraints on data to be transmitted by the non-AP MLD apply.

22. The method according to claim 18, wherein: According to the UL TID to link mapping, at least one UL TID is mapped on the first enabled link for transmitting the BSRP TF.

23. A communication method in a wireless network, comprising: At an AP MLD configured to perform a frame exchange operation with at least one non-access point multi-link device (i.e., at least one non-AP MLD) operating on a multi-link utilizing an uplink traffic identifier to link mapping (i.e., a UL TID to link mapping), A buffer status report polling trigger frame (BSRP TF) is transmitted to the non-APMLD on a first enabled link mapped with at least one UL TID according to the UL TID to link mapping.

24. The method according to claim 18 or 23, further comprising: At the AP MLD, signaling information for indicating which of the following two sub-modes of the EML mode is to be used is transmitted to the non-AP MLD: a first sub-mode of the EML mode, the first sub-mode comprising the transmission of the basic TF, the basic TF scheduling the UL resources to the non-AP MLD and including constraints on data to be transmitted within the scheduled UL resources based on the UL TID-to-link mapping; and a second sub-mode of the EML mode, in which the AP MLD retrieves an indication of a selected EML link to be used for frame exchange from the BSR frame, and transmits a basic TF to the non-AP MLD on the selected EML link to trigger an uplink frame exchange with the non-AP MLD on the selected EML link.

25. A communication method in a wireless network, comprising: At an AP MLD configured to perform a frame exchange operation with at least one non-access point multi-link device (i.e., at least one non-AP MLD) operating on a multi-link utilizing an uplink traffic identifier to link mapping (i.e., a UL TID to link mapping), receiving, from the non-AP MLD on a first EML link in the EML link set, a BSR frame in response to a buffer status report polling trigger frame (BSRP TF) transmitted on the first EML link; retrieving from the BSR frame an indication of a selected one of the EML links to be used for frame exchange; as well as A basic TF is transmitted to the non-AP MLD over the selected EML link to trigger an uplink frame exchange with the non-AP MLD over the selected EML link.

26. The method according to claim 11 or 25, wherein: In view of the UL TID to link mapping, the selected EML link is implicit in the TID or TIDs reported in the BSR frame.

27. The method according to claim 11 or 25, wherein: One or more reported TIDs are mapped on a second EML link in the set of EML links instead of the first EML link.

28. The method of claim 11 or 25, wherein: Under a negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 1, if the reported TID is mapped on the same EML link, then the selected EML link to be used for frame exchange is the same EML link.

29. The method according to claim 11 or 25, wherein: Under the default TID-to-link mapping or under the negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value = 2, the selected EML link to be used for frame exchange is the first EML link, wherein the BSRP trigger frame and the BSR frame are transmitted or received on the first EML link.

30. The method of claim 11 or 25, wherein: Under the negotiated TID-to-link mapping with TID-to-link mapping negotiation support subfield value=1, if at least two reported TIDs are mapped to at least two different EML links, the selected EML link to be used for frame exchange is the first EML link on which the BSRP trigger frame and the BSR frame are transmitted or received.

31. The method according to claim 11 or 25, wherein: The selected EML link is explicitly indicated in the BSR frame by a link identifier.

32. The method of claim 25, wherein: The selected EML link is a second EML link in the EML link set that is different from the first EML link, wherein the BSRP trigger frame is transmitted and the BSR frame is received on the first EML link.

33. The method of claim 32, further comprising: At the AP MLD, on the second EML link different from the first EML link, before transmitting a basic trigger frame for scheduling UL resources to the non-AP MLD within a frame exchange sequence, an initial frame for triggering the frame exchange sequence on the second EML link is transmitted, wherein the BSRP trigger frame is transmitted on the first EML link.

34. The method according to claim 14 or 33, wherein: The initial frame contains an invitation to other non-AP MLDs to be triggered in an incoming UL EML frame exchange on the second EML link.

35. The method of claim 14, 33 or 34, wherein: The initial frame is a multi-user request to send frame, namely, a MU-RTS frame.

36. The method of claim 25, further comprising: At the AP MLD, signaling information for indicating which of the following two sub-modes of the EML mode is to be used is transmitted to the non-AP MLD: a first sub-mode of the EML mode, the first sub-mode comprising transmission of a basic TF, the basic TF scheduling UL resources to the non-AP MLD and including constraints on data to be transmitted within the scheduled UL resources based on the UL TID-to-link mapping; and A second sub-mode of the EML mode, in which the AP MLD performs the retrieval of an indication of the selected EML link to be used for frame exchange from the BSR frame, and the transmission of a basic TF to the non-AP MLD on the selected EML link for triggering uplink frame exchange with the non-AP MLD on the selected EML link.

37. The method according to claim 24 or 36, wherein: The signaling information is contained in a subfield of a common information field within the BSRP TF transmitted by the AP MLD or in a subfield of a user information field assigned to the non-AP MLD.

38. A wireless communication device comprising at least one microprocessor configured to perform the method of claim 1, 11, 18, 23 or 25.

39. A non-transitory computer readable medium storing a program which, when executed by a microprocessor or a computer system in a wireless device, causes the wireless device to perform the method of claim 1, 11, 18, 23 or 25.

40. A communication method in a wireless network, comprising: At an AP attached to an access point multi-link device, i.e., an AP MLD, and operating on a link to exchange frames with a non-AP station attached to a non-AP MLD, A basic trigger frame (i.e., a basic TF) is transmitted on the link, wherein the basic TF schedules uplink resources (i.e., UL resources) to the attached non-AP station and includes a preferred AC subfield in a trigger-related user information field of a user information field corresponding to the scheduled UL resources in the basic TF, Therein, the preferred AC subfield is set to a value for the AC for which at least one corresponding traffic identifier, ie, TID, is mapped in the UL for the link for the non-AP MLD via TID-to-link mapping.

41. The method of claim 40, wherein: The TID-to-link mapping is negotiated between the AP MLD and the non-AP MLD.

42. The method of claim 40, further comprising: Transmitting a buffer status report polling trigger frame (BSRP TF) on the link; as well as A BSR frame reporting buffered flow is received from the attached non-AP station on the link.

43. An AP attached to an access point multi-link device (AP MLD), the AP being adapted to operate on a link of a wireless network to exchange frames with a non-AP station attached to a non-AP MLD, the attached AP comprising: a transmitter configured to transmit a basic trigger frame (basic TF) on the link, wherein the basic TF schedules uplink resources (UL resources) to attached non-AP stations and includes a preferred AC subfield in a trigger-related user information field of a user information field corresponding to the scheduled UL resources in the basic TF, Therein, the preferred AC subfield is set to a value for the AC for which at least one corresponding traffic identifier, ie, TID, is mapped in the UL for the link for the non-AP MLD via TID-to-link mapping.

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