Operating Conditions for Trigger-Based Uplink Transmission in the Co-Located Station of EMLSR or EMLMR

Abstract

The non-AP MLD operates in multi-link using the UL TID-To-Link mapping. When activating the EML mode, as a function of the UL TID-To-Link mapping, it selects the set of EML links to which the EML mode is applied and sends a notification identifying the selected set of EML links to the AP MLD. Further or alternatively, while the non-AP MLD is operating in the EML mode using the set of EML links, in response to the BSRP TF received from the AP MLD via a first EML link among the set of EML links, as a function of the UL TID-To-Link mapping, it sends a BSR frame reporting buffered traffic to the AP MLD via the first EML link.

Description

Technical Field

[0001] The present invention generally relates to wireless communication, and more specifically to multi-link (ML) communication.

Background Art

[0002] Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, and broadcasting. These wireless networks may be multi-connectivity networks that can support multiple users by sharing available network resources. Examples of such multi-connectivity 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 (registered trademark)) provides a very large number of mechanisms for wireless communication between STAs.

[0004] With the development of latency-sensitive applications such as online games, real-time video streaming, virtual reality, and remote operation of drones and robots, it is necessary to consider requirements and problems of better throughput, low latency, and robustness. Such problems are currently being considered by the IEEE 802.11 working group as the main objective of issuing the next 802.11 major release known as 802.11be or EHT (Extremely High Throughput).

[0005] The IEEE P802.11be / D2.0 version (May 2022, hereinafter referred to as the "D2.0 standard") introduces Multi-Link (ML) Operation (MLO). MLO improves data throughput by enabling communication between STAs via multiple simultaneous and non-contiguous communication links.

[0006] MLO enables a non-AP (Access Point) MLD (ML Device) to register with an AP MLD, that is, to discover, authenticate, associate with, and configure multiple links with the AP MLD. Each link enables channel access and frame exchange between the non-AP MLD and the AP MLD based on the supported capabilities exchanged during the association procedure.

[0007] An MLD is a logical entity that has multiple affiliated stations (STAs) and a single Medium Access Control (MAC) Service Access Point (SAP) for the Logical Link Control (LLC) that includes one MAC data service. Thus, an AP MLD is composed of multiple affiliated APs, while a non-AP MLD is composed of multiple affiliated non-AP STAs. The affiliated STAs of both AP MLD and non-AP MLD can use the 802.11 mechanism to communicate with the affiliated STAs of another MLD via each of the configured multiple communication links.

[0008] With the introduction of the spatial multiplexing capabilities of MLO and MLD, the D2.0 standard introduced a new Operation Mode (OM) called Enhanced Multi-Link Operating Mode (EML-OM), namely the EMLSR (Enhanced Multi-Link Single Radio) mode and the EMLMR (Enhanced Multi-Link Multi-Radio) mode.

[0009] The non-AP MLD declares support for the EML Operation Mode (known as EML Capabilities) to the AP MLD during the association phase. In the operation mode, the enabling (activation) and disabling (deactivation) of the EML Operation Mode are initiated by the non-AP MLD that transmits a specific EHT action frame called "EML OM Notification". The D2.0 standard states that the two modes of EMLSR and EMLMR are mutually exclusive.

[0010] When the EMLMR mode is enabled, the non-AP MLD listens simultaneously to a set of enabled links (so-called EMLMR links, usually composed of two enabled links) to receive the initial frame transmitted by the AP MLD and start frame exchange. Then, it aggregates the physical resources of some of its own different radios used on different links (so-called EMLMR links) to transmit or receive data up to a predefined number of supported Rx / Tx spatial streams, one EMLMR link at a time, usually the link on which the initial frame was received. This number may be more than the number of Rx / Tx spatial streams supported by each radio. The frame exchange sequence initiated by the AP MLD can be either a Trigger Based (TB) Downlink (DL) transmission or a Trigger Based (TB) Uplink (UL) transmission on the link where the initial frame was received.

[0011] When the EMLSR mode is enabled, non-AP MLDs listen simultaneously to a set of enabled links (so-called EMLMR links, usually consisting of two enabled links) in order to receive an initial control frame (e.g., MU-RTS trigger frame, BSRP trigger frame) from the AP MLD to start frame exchange, and then perform data frame exchange with the AP MLD through only one EMLSR link at a time, usually the link on which the initial control frame was received. The frame exchange sequence initiated by the AP MLD can be either a Trigger Based (TB) Downlink (DL) transmission or a Trigger Based (TB) Uplink (UL) transmission on the link on which the initial control frame was received.

[0012] With the introduction of MLO, the D2.0 standard also defines a Traffic IDentifier (TID)-To-Link mapping mechanism. This mechanism enables an AP MLD and non-AP MLDs that have performed or are performing multi-link setup to determine how to allocate UL and DL QoS traffic corresponding to TID values from 0 to 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 procedures that enable TID-To-Link mapping negotiation in the DL and / or UL directions between the initiating MLD and the responding MLD.

[0013] In the EMLMR or EMLSR frame exchange operation initiated by the AP MLD currently defined in IEEE P802.11be / D2.0, the selection of the EMLMR or EMLSR link used in the frame exchange sequence is driven by the AP MLD when transmitting the initial frame or the initial control frame. Currently, the standard does not specify any rules regarding the matching between this selected EMLMR link or EMLSR link and the TID-To-Link mapping used between the AP MLD and the non-AP MLD. In some situations, especially for TB UL traffic, the lack of this rule can lead to mismatches and inefficiencies. For example, in an EMLMR or EMLSR link where the TID is not mapped or the TID currently buffered by the non-AP MLD is not mapped, the TB UL transmission opportunity can be provided by the AP MLD to the non-AP MLD. As a result, the TB UL transmission opportunity is lost. On the other hand, the non-AP MLD in the frame exchange state on that EMLMR or EMLSR link also loses the opportunity to transmit on other EMLMR or EMLSR links.

Summary of the Invention

[0014] It is a broad object of the present invention to harmonize the operation of the EML mode, whether EMLMR or EMLSR, with the Uplink TID-To-Link mapping for Trigger Based (TB) Uplink traffic (UL) transmission.

[0015] In this context, embodiments of the present invention are in a non-access point (non-AP) multi-link device (MLD) operating in multi-link using Uplink (UL) Traffic IDentifier (TID)-To-Link mapping. -Activating the Enhanced Multi-Link (EML) mode, including, as a function of the UL TID-To-Link mapping, selecting a set of EML links of the links to which the EML mode is applied, and sending a notification specifying the selected set of EML links to the AP MLD, and activating the EML mode. -While the non-AP MLD is operating in the EML mode using a set of EML links, in response to a Buffer Status Report Poll (BSRP) trigger frame received from the AP MLD via a first EML link among the set of EML links, sending, via the first EML link, a BSR frame reporting the buffered traffic as a function of the UL TID-To-Link mapping to the AP MLD. Providing a communication method in a wireless network, including at least any one of the above.

[0016] By considering the TID-To-Link mapping in the setup of the set of EML links for the EML mode and / or in the BSR, the present invention can ensure that the EML links used by the AP MLD to trigger frame exchange are appropriate for the TB UL communication for the non-AP MLD. Thereby, the above-mentioned mismatch or inefficiency between the operation of the EML mode and the UL TID-To-Link mapping for TB UL traffic transmission can be avoided or reduced.

[0017] More generally, considering TID-To-Link mapping in link setup can be applied not only in EML mode but also in multi-link mode regardless of the EML mode. Therefore, a more general embodiment of the present invention is that in a non-AP MLD operating in multi-link using UL TID-To-Link mapping, while the non-AP MLD operates in multi-link mode using a set of links, in response to a BSRP trigger frame received from an AP MLD via a first link among the set of links, via the first link, as a function of the UL TID-To-Link mapping, it includes transmitting a BSR frame reporting buffered traffic to the AP MLD, which provides a communication method in a wireless network. In some embodiments according to this more general approach, the BSR frame reports the buffered traffic when there is buffered traffic of at least one UL TID mapped to the first link according to the UL TID-To-Link mapping. In some other embodiments, the BSR frame reports the buffered traffic when there is buffered traffic of only one or more UL TIDs mapped to the first link according to the UL TID-To-Link mapping.

[0018] Optional features of embodiments of the present invention are defined below with reference to the method, but they can be replaced with features of the apparatus.

[0019] In some embodiments, selecting the set of EML links as a function of the UL TID-To-Link mapping includes satisfying the constraint that at least one EML link among the set of EML links must have at least one UL TID mapped according to the UL TID-To-Link mapping.

[0020] With this function, there is a set of EML links where the UL TID is not mapped according to the UL TID-To-Link mapping, and it is possible to avoid the AP MLD triggering the non-AP MLD for UL transmission in the links of this set of EML links. Therefore, such losses in TB UL transmission are avoided. This function (and its constraints) is preferentially applied when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping where the value of the TID-To-Link Mapping Negotiation Supported subfield is equal to 1.

[0021] In some embodiments, selecting the set of EML links as a function of the UL TID-To-Link mapping includes satisfying the constraint that the set of EML links must not be separated from another set of links where all UL TIDs are mapped according to the UL TID-To-Link mapping.

[0022] In other words, in these embodiments, at least one EML link in the set of EML links must be included in each of another set of links where all UL TIDs are mapped according to the UL TID-To-Link mapping. This function also makes it possible to avoid the case where there is no UL TID mapped according to the UL TID-To-Link mapping in the set of EML links and the AP MLD may trigger the non-AP MLD for UL transmission on the links of this set of EML links. This function (and its constraints) is preferentially applied when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping where the value of the TID-To-Link Mapping Negotiation Supported subfield is equal to 2.

[0023] In some embodiments, the BSR frame reports buffered traffic of at least one UL TID mapped to the first EML link according to the UL TID-To-Link mapping, if any.

[0024] This function also enables avoiding the case where a BSR response frame sent by a non-AP MLD reports buffered traffic of TIDs not mapped to the first link where the BSRP TF was received. In fact, in such a case, the trigger of the non-AP MLD for UL transmission by the AP MLD on the first link is wasted and the overall EML operation initiated is inefficient.

[0025] In some embodiments, the BSR frame reports only the buffered traffic if there is buffered traffic of one or more UL TIDs mapped to the first EML link according to the UL TID-To-Link mapping.

[0026] This feature ensures that a non-AP MLD can benefit from TB UL transmissions scheduled by an AP MLD on the first link based on the BSR.

[0027] This function and the previous function (and their respective constraints) are preferentially applied when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value equal to 1.

[0028] In some embodiments, the BSRP trigger frame is an initial frame that triggers a frame exchange sequence via the first EML link, and the method is performed at the non-AP station, - Obtaining the UL resources scheduled within the frame exchange sequence; - Transmitting, within the scheduled UL resources, data having a UL TID mapped to the first EML link according to the UL TID-Link mapping reported in the BSR frame; It further includes.

[0029] Therefore, the non-AP MLD can transmit data without a mismatch between the operation in the EML mode and the Uplink TID-To-Link mapping for TB UL traffic transmission.

[0030] The initial frame that triggers the frame exchange sequence is called the "initial frame" in the EMLMR mode and the "initial control frame" in the EMLSR mode.

[0031] In some embodiments, the method includes, in the non-AP MLD, the following two sub-modes of the EML mode - The first sub-mode of the EML mode including the transmission of the BSR frame reporting the buffered traffic as a function of the UL TID-To-Link mapping, and - In response to a BSRP trigger frame received from the AP MLD via the first EML link, the non-AP MLD transmits, via the first EML link, a BSR frame indicating a selected EML link from among the set of EML links to be used for frame exchange to the AP MLD, the second sub-mode of the EML mode. It further includes transmitting signaling information indicating which of the above should be used to the AP MLD.

[0032] Therefore, the non-AP MLD explicitly signals which of the two sub-modes of the EML mode to use. Hereinafter, the first and second sub-modes of the EML mode are also referred to as the "current EML operation for TB UL traffic" and the "new EML operation for TB UL traffic", respectively.

[0033] Also, an embodiment of the present invention is in a non-access point (non-AP) multi-link device (MLD) that operates in multi-link using an Uplink (UL) Traffic IDentifier (TID)-To-Link mapping and an EML mode applied using a set of EML links, - receiving a Buffer Status Report Poll (BSRP) trigger frame from the AP MLD via a first EML link of the set of the EML links; - receiving a Buffer Status Report Poll (BSRP) trigger frame from the AP MLD via a first EML link of the set of the EML links; - as a function of the UL TID-Link mapping and selecting, from among the set of the EML links, an EML link to be used for frame exchange of the buffered traffic reported in a BSR frame; - transmitting, via the first EML link, the BSR frame indicating the selected EML link to be used for the frame exchange to the AP MLD; and provides a communication method in a wireless network including the above.

[0034] Thus, in non-AP MLD, it relies on the transmission of a BSR frame indicating the selected EML link to be used for frame exchange, and the selected link is selected as a function of the UL TID-To-Link mapping and the buffered traffic reported in the BSR frame. Due to the fact that the UL TID-To-Link mapping is taken into account, this innovative solution makes it possible to avoid or reduce the aforementioned mismatches and inefficiencies between the operation of the EML mode and the UL TID-To-Link mapping in TB UL traffic transmission.

[0035] In some embodiments, the selected EML link is a second EML link among the set of EML links, which is different from the first EML link on which the BSRP trigger frame is received and the BSR frame is transmitted.

[0036] In some embodiments, the method further includes, in the non-AP MLD, after transmitting the BSR frame, switching a first STA belonging to the non-AP MLD and corresponding to the selected EML link from a listening operating state or a frame exchange disabling state to a frame exchange enabling state.

[0037] In some embodiments, the method further includes, in the non-AP MLD, receiving an initial frame that triggers the frame exchange sequence on the second link before receiving a basic trigger frame that schedules UL resources for the non-AP MLD within the frame exchange sequence via the second EML link, which is different from the first EML link on which the BSRP trigger frame is received.

[0038] Therefore, the non-AP MLD can transmit data without a mismatch between the operation of the EML mode and the Uplink TID-To-Link mapping for TB UL traffic transmission.

[0039] In some embodiments, the method further includes, in the non-AP MLD, selecting the set of EML links as a function of the UL TID-To-Link mapping, and sending a notification identifying the selected set of EML links to the AP MLD.

[0040] Thus, in the non-AP MLD, the transmission of a BSR frame indicating the selected EML links to be used for frame exchange can be combined with taking into account the TID-to-Link mapping in the setup of the set of EML links in the EML mode.

[0041] In some embodiments, the method includes, in the non-AP MLD, the following two sub-modes of the EML mode - In response to a BSRP trigger frame received from the AP MLD via a predetermined EML link among the set of EML links, when there is buffered traffic of at least one UL TID mapped to the predetermined EML link according to the UL TID-To-Link mapping in the non-AP MLD, the non-AP MLD transmits, via the predetermined EML link, a BSR frame reporting the buffered traffic to the AP MLD, the first sub-mode of the EML mode; and - the second sub-mode of the EML mode including the transmission of the BSR frame indicating the selected EML links to be used for the frame exchange, and further includes sending, to the AP MLD, signaling information indicating which of the two is to be used.

[0042] Thus, also as already described, the non-AP MLD can signal a selection between the two aforementioned sub-modes of the EML mode.

[0043] In some embodiments, the signaling information is included in a subfield of an EML Control field of an EML Operation Mode (OM) Notification frame transmitted by the non-AP MLD.

[0044] Embodiments of the present invention also relate to an access point multi-link device (AP MLD) configured to perform a frame exchange operation with at least one non-AP MLD operating in multi-link using Uplink (UL) Traffic IDentifier (TID)-To-Link mapping, - sending a Buffer Status Report Poll (BSRP) trigger frame (TF) to the non-AP MLD via a first active link; - receiving, via the first active link, a BSR frame reporting buffered traffic from the non-AP MLD; - scheduling UL resources for the non-AP MLD and transmitting, via the first active link, a basic TF including constraints on data to be transmitted within the scheduled UL resources based on the UL TID-Link mapping to the non-AP MLD; and provides a communication method in a wireless network including the above.

[0045] Therefore, in AP MLD, an innovative solution is proposed that depends on scheduling UL resources and transmitting a basic TF containing constraints based on UL TID-To-Link mapping for the data transmitted within the scheduled UL resources to a non-AP MLD. Therefore, it is also possible to consider UL TID-To-Link mapping to provide suitable TB UL transmission for a non-AP MLD and avoid or reduce the aforementioned mismatch or inefficiency between the multi-link mode operation for TB UL traffic transmission and UL TID-To-Link mapping. This innovative solution is particularly applicable, but not limited to, the case where the multi-link mode operation is the EML mode (EMLSR mode or EMLMR mode), in which case the first active link is also an EML link.

[0046] In some embodiments, the constraint on the data to be transmitted within the scheduled UL resources is indicated by the value of the access category (AC) corresponding to the UL TID mapped to the first active link according to the UL TID-To-Link mapping.

[0047] In some embodiments, the value is indicated in the preferred AC subfield of the Trigger Dependent User Info field of the User Info field corresponding to the scheduled UL resource within the basic TF.

[0048] In some embodiments, the constraint on the data transmitted by the non-AP MLD is applicable when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value equal to 1.

[0049] In some embodiments, at least one UL TID is mapped to the first active link over which the BSRP TF is transmitted according to the UL TID-Link mapping.

[0050] This function (for the link used to transmit the BSRP TF) can also avoid or reduce the aforementioned mismatches or inefficiencies between the multi-link mode operation for TB UL traffic transmission and the UL TID-To-Link mapping, in order to provide TB UL transmissions suitable for non-AP MLDs and also considering the UL TID-To-Link mapping.

[0051] Embodiments of the present invention also relate to at least one non-AP MLD operating on a multi-link using Uplink (UL) Traffic IDentifier (TID)-To-Link mapping, and an Access Point Multi-Link Device (AP MLD) configured to perform a frame exchange operation, transmitting a Buffer Status Report Poll (BSRP) Trigger Frame (TF) to the non-AP MLD via a first active link to which at least one UL TID is mapped according to the UL TID-To-Link mapping, and provides a communication method in a wireless network including the above.

[0052] In other words, the function related to the link used to send the BSRP TF (the link to which at least one UL TID is mapped) can be implemented independently of the previous function (the basic TF including the constraints based on UL TID-Link mapping for the data transmitted within the scheduled UL resources). This innovative solution is applied, although not exclusively, particularly when the multi-link mode operation is in the EML mode (EMLSR mode or EMLMR mode), in which case the first active link described above is also an EML link. In fact, in this case, the BSRP TF is the initial frame, and the frame exchange is performed on the first active link (EML link).

[0053] In some embodiments, the method includes, at the AP MLD, the following two sub-modes of the EML mode - a first sub-mode of the EML mode, including scheduling the UL resources at the non-AP MLD and transmitting the basic TF including the constraints based on the UL TID-To-Link mapping for the data to be transmitted within the scheduled UL resources, - a second sub-mode of the EML mode, in which the AP MLD obtains an indication of the selected EML link to be used for frame exchange from the BSR frame, and transmits, via the selected EML link, a basic TF to the non-AP MLD for triggering uplink frame exchange with the non-AP MLD on the selected EML link, and further includes transmitting, to the non-AP MLD, signaling information indicating which of the above is used.

[0054] Therefore, the AP MLD can signal a selection between the above two sub-modes of the EML mode.

[0055] Embodiments of the present invention also relate to an Access Point Multi-Link Device (AP MLD) configured to perform a frame exchange operation with at least one non-AP MLD operating in multi-link using Uplink (UL) Traffic IDentifier (TID)-To-Link mapping, - receiving, via a first EML link of a set of EML links, from the non-AP MLD, a BSR frame in response to a Buffer Status Report Poll (BSRP) trigger frame (TF) transmitted via the first EML link; - obtaining, from the BSR frame, an indication of a selected EML link to be used for frame exchange among the EML links; - transmitting, via the selected EML link, to the non-AP MLD, a basic TF for triggering an uplink frame exchange with the non-AP MLD on the selected EML link; and providing a communication method in a wireless network including the above.

[0056] Accordingly, an innovative solution in an AP MLD is proposed that relies on obtaining an indication of a selected EML link to be used for frame exchange from a BSR frame transmitted by a non-AP MLD. Thus, UL TID-To-Link mapping is also indirectly considered, making it possible to avoid or reduce the aforementioned mismatches and inefficiencies between the operation of the EML mode for TB UL traffic transmission and UL TID-To-Link mapping.

[0057] According to a function shared by the non-AP MLD and the AP MLD, the selected EML link is implicit with respect to one or more TIDs reported in the BSR frame when the UL TID-To-Link mapping is provided. Thereby, the signaling cost of the frames to be exchanged is saved.

[0058] According to the functions shared by the non-AP MLD and the AP MLD, the reported one or more TIDs are mapped to the second EML link in the set of the EML links and not mapped to the first EML link. Therefore, there is an implicit and explicit signaling that the BSRP / BSR exchange is performed on the first link while the non-AP MLD requests frame exchange on the second link.

[0059] According to the functions shared by the non-AP MLD and the AP MLD, under the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 1, if the reported TIDs are mapped to the same EML link, the selected EML link to be used for frame exchange is the same EML link.

[0060] This setting eliminates the ambiguity when multiple TIDs mapped to multiple EML links are reported.

[0061] According to the functions shared by the non-AP MLD and the AP MLD, under the default TID-To-Mapping or under the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 2, 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.

[0062] This also removes the ambiguity when the reported TIDs cannot identify a single EML link.

[0063] Naturally, instead of selecting the first link to remove the ambiguity, the second link may be selected.

[0064] According to the functions shared by non-AP MLD and AP MLD, under the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported 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.

[0065] This removes the ambiguity again when the reported TID cannot identify a single EML link. Instead of selecting the first link to remove the ambiguity, the second link may be selected.

[0066] According to the functions shared by non-AP MLD and AP MLD, the selected EML link is explicitly indicated in the BSR frame by the link identifier.

[0067] This can simplify the processing of AP MLD.

[0068] According to the characteristics shared by non-AP MLD and AP MLD, the initial frame includes an invitation to other non-AP MLDs to be triggered in the next UL EML frame exchange of the second EML link.

[0069] This can trigger some of the other EML-active non-AP MLDs in the next UL EML frame exchange on the second EML link. "Other" may mean different from the non-AP MLDs already triggered by the BSRP frame.

[0070] According to the functions shared by non-AP MLD and AP MLD, the initial frame is a Multi User-Request to Send (MU-RTS) frame.

[0071] The MU-RTS / CTS procedure can protect the second EML link before the next UL EML frame exchange because the legacy station uses a basic frame that can be decoded.

[0072] In some embodiments, the method includes, at the AP MLD, the following two sub-modes of the EML mode - The first sub-mode of the EML mode, including scheduling UL resources for the non-AP MLD and transmitting a basic TF including constraints based on the UL TID-To-Link mapping for the data to be transmitted within the scheduled UL resources, - The second sub-mode of the EML mode, in which the AP MLD obtains 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 via the selected EML link to trigger an uplink frame exchange with the non-AP MLD on the selected EML link, and further includes transmitting signaling information to the non-AP MLD indicating which of the above is to be used.

[0073] Therefore, as already described, the AP MLD can signal its selection between the above two sub-modes of the EML mode.

[0074] In some embodiments, the signaling information is included in a sub-field of the Common Info field within the BSRP TF transmitted by the AP MLD, or in a sub-field of the User Info field assigned to the non-AP MLD.

[0075] Also, in the access point (AP) belonging to an AP multi-link device (MLD), operating on a link for exchanging frames with a non-AP station belonging to a non-AP MLD, - A basic trigger frame (TF) that schedules an uplink (UL) resource to the non-AP station to which it belongs via the link, the method including transmitting the basic TF including a preferred AC subfield in a Trigger Dependent User Info field of a User Info field corresponding to the scheduled UL resource within the basic TF. The preferred AC subfield is provided with a communication method in a wireless network in which at least one corresponding TID is set to a value of an AC mapped in UL to the link for the non-AP MLD by a Traffic IDentifier (TID)-To-Link mapping.

[0076] The TID-To-Link Mapping may be negotiated between the AP MLD and the non-AP MLD. Also, the method includes - Transmitting a Buffer Status Report Poll (BSRP) trigger frame (TF) via the link; - Receiving, from the non-AP station to which it belongs, a BSR frame reporting buffered traffic via the link; and may further include.

[0077] Also, an access point (AP) belonging to an AP multi-link device (MLD) adapted to operate on a link of a wireless network to exchange frames with a non-AP station belonging to the non-AP MLD, the belonging AP - A basic trigger frame (TF) for scheduling uplink (UL) resources to the non-AP station to which it belongs via the link, the basic TF including a preferred AC subfield in the Trigger Dependent User Info field of the User Info field corresponding to the scheduled UL resources within the basic TF, and having a transmitter configured to transmit the basic TF. The preferred AC subfield is provided by the access point with the value of the AC in which at least one corresponding TID is mapped in UL to the link for the non-AP MLD by Traffic IDentifier (TID)-To-Link mapping.

[0078] In connection therewith, the present invention also provides a wireless communication device including at least one microprocessor configured to execute any of the methods defined above. The wireless communication device may be either a non-AP MLD or an AP MLD.

[0079] Another aspect of the present invention relates to a non-transitory computer-readable medium storing a program that, when executed by a microprocessor or computer system within a wireless device, causes the wireless device to execute any of the methods as defined above.

[0080] At least a part of the method according to the present invention can be implemented by a computer. Accordingly, the present invention can take the form of a completely hardware embodiment, a completely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects that can all generally be referred to herein as "circuit", "module" or "system". Further, the present invention may take the form of a computer program product embodied in any tangible expression medium having computer-usable program code embodied therein.

[0081] 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 in 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. Transitory carrier media may include signals such as electrical signals, electronic signals, optical signals, acoustic signals, magnetic signals, or electromagnetic signals, such as microwave signals or RF signals.

Brief Description of the Drawings

[0082] Hereinafter, embodiments of the present invention will be described by way of example only with reference to the following drawings.

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Figure 13

MODE FOR CARRYING OUT THE INVENTION

[0083] The technology described in this specification can be used in various broadband wireless communication systems including communication systems based on orthogonal multiplexing schemes. Such communication systems include, for example, a space division multiple access (SDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, and a single carrier frequency division multiple access (SC-FDMA) system. The SDMA system can utilize sufficiently different directions to simultaneously transmit data belonging to a plurality of user terminals, i.e., wireless devices or STAs. The TDMA system can enable a plurality of user terminals to share the same frequency channel by dividing the transmission signal into different time slots or resource units and allocating each time slot to a different user terminal. The OFDMA system utilizes orthogonal frequency division multiplexing (OFDM), and OFDM is a modulation technique that divides the system-wide bandwidth into a plurality of orthogonal subcarriers or resource units. These subcarriers may also be called tones, bins, etc. In OFDM, each subcarrier can be independently modulated with data. The SC-FDMA system can utilize interleaved FDMA (IFDMA) that transmits with subcarriers dispersed over the system bandwidth, localized FDMA (LFDMA) that transmits with a block of adjacent subcarriers, or enhanced FDMA (EFDMA) that transmits with a plurality of blocks of adjacent subcarriers.

[0084] The teachings of this specification can be incorporated into various devices (e.g., STAs), such as being implemented within or executed by an STA. In some aspects, a wireless device or STA implemented in accordance with the teachings of this specification may or may not include an access point (so-called AP) (so-called non-AP STA or STA).

[0085] This example is described in the context of a WiFi (registered trademark) network, but the present invention can be used in any type of wireless network, such as a cellular phone cellular network implementing a very similar mechanism.

[0086] AP includes NodeB, radio network controller ("RNC"), evolved NodeB (eNB), 5G next-generation base station ("gNB"), base station controller ("BSC"), base transceiver station ("BTS"), transceiver function ("TF"), wireless router, wireless transceiver, basic service set ("BSS"), extended service set ("ESS"), radio base station ("RBS"), or other terms, and can be implemented as or known as such.

[0087] The non-AP STA includes, is implemented as, or is known as, a subscriber STA, subscriber unit, mobile STA (MS), remote STA, remote terminal, user terminal (UT), user agent, user device, user equipment (UE), user STA, or other terms. In some implementations, the STA can include a cellular phone, cordless phone, Session Initiation Protocol (SIP) phone, wireless local loop (WLL) STA, personal digital assistant (PDA), handheld device with wireless connectivity, or other suitable processing device connected to a wireless modem. Thus, one or more aspects taught herein can be incorporated into a phone (e.g., a cellular phone or smartphone), computer (e.g., a laptop), tablet, mobile communication device, mobile computing device (e.g., a personal data assistant), 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, the non-AP STA can be a wireless node. Such a wireless node can provide connectivity to or for a network (e.g., a wide area network such as the Internet or a cellular network) via, for example, a wired or wireless communication link.

[0088] The AP manages a set of STAs (registered or associated with the AP) that organize access to the wireless medium for communication purposes. The STAs (including the APs to which they register) form a service set, hereinafter referred to as a Basic Service Set (BSS) (although other terms can also be used). The same physical STA operating as an access point may manage two or more BSSs (and thus the corresponding WLANs): thus, each BSS is uniquely identified by a specific Basic Service Set Identifier (BSSID) and is managed by a separate virtual AP implemented on the physical AP. Each STA is identified within the BSS by an identifier (AID) assigned by the AP at registration.

[0089] The 802.11 family of standards defines various Medium Access Control (MAC) mechanisms for enabling access to the wireless medium.

[0090] As shown in the May 2022 draft IEEE P802.11be / D2.0, in the current discussions of Task Group 802.11be, Multi-Link Operation (MLO) has been introduced with respect to the operation of the MAC layer. MLO enables a multi-link device to establish or configure multiple links and operate them simultaneously.

[0091] A Multi-Link Device (MLD) is a logical entity that has multiple affiliated STAs (STAs) and has a single Medium Access Control (MAC) service access point (SAP) for the Logical Link Control (LLC) that includes one MAC data service. An Access Point Multi-Link Device (or AP MLD) corresponds to an AP called the "affiliated AP" for each STA belonging to the MLD. A Non-Access Point Multi-Link Device (or non-AP MLD) corresponds to an MLD that is a non-AP STA called the "affiliated non-AP STA" for each STA belonging to the MLD. "Multi-Link Device", "ML Device" (MLD), "Multi-Link Logical Entity", "ML Logical Entity" (MLE), "Multi-Link Set" and "ML Set" in the literature are synonyms that designate the same type of ML device. An exemplary architecture of the multi-link device will be described below with reference to FIGS. 1a and 1b.

[0092] Multiple affiliated non-AP STAs of the non-AP MLD can establish communication links with multiple affiliated APs of the AP MLD to form a multi-link channel.

[0093] The links established for the MLD (or "active links") are theoretically independent, meaning that the channel access procedure and communication to the communication medium are executed independently for each link. Thus, 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 via a specific link).

[0094] Thus, a communication link or "link" corresponds to a predetermined channel (e.g., 20 MHz, 40 MHz, etc.) in a predetermined frequency band (e.g., 2.4 GHz, 5 GHz, 6 GHz) between the AP belonging to the AP MLD and the non-AP STA belonging to the non-AP MLD.

[0095] The associated AP and non-AP STAs operate on their respective channels in accordance with one or more of the IEEE 802.11 standards (a / b / g / n / ac / ad / af / ah / aj / ay / ax / be) or other wireless communication standards.

[0096] Thanks to multi-link aggregation, theoretically, the traffic associated with one MLD can be transmitted across multiple parallel communication links, thereby increasing the network capacity and maximizing the utilization of available resources.

[0097] From an architectural perspective, an MLD typically includes several radios for implementing the associated STA, but it does not have to be the same number as the number of associated STAs. In particular, a non-AP MLD can operate with a number of associated STAs greater than the number of radios (it can even be reduced to one).

[0098] In the D2.0 standard, several enhanced multi-link operating modes (EMLOM), namely enhanced multi-link single radio (EMLSR) and enhanced multi-link multi radio (EMLMR), are defined from this physical architecture. In the D2.0 standard, it is stated that the two modes of EMLSR and EMLMR are mutually exclusive.

[0099] In the association phase, non-AP MLD declares support for the EMLSR and / or EMLMR modes to the AP MLD (see so-called EML Capabilities, Figure 5a). In the operation mode, the activation and deactivation of the EMLSR or EMLMR mode are initiated by the non-AP MLD, and the non-AP MLD transmits a specific EHT action frame called "EML OM Notification" (see Figure 5b) indicating a set of valid links (so-called EMLSR or EMLMR links) to which the EMLSR or EMLMR mode to be activated is applied. Usually, the "EMLSR / EMLMR links" set is composed of two links. However, more valid links may be used.

[0100] When activated, the EMLSR mode enables the non-AP MLD to simultaneously listen to the enabled links among the set "EMLSR links" to receive the initial control frames (e.g., MU-RTS trigger frame or BSRP trigger frame) transmitted by the AP MLD, and then enables the non-AP MLD to perform the data frame exchange with the AP MLD on only one link at a time, usually the link on which the initial control frame was received. The frame exchange sequence initiated by the AP MLD can be either a Trigger Based (TB) Downlink (DL) transmission or a Trigger Based (TB) Uplink (UL) transmission on the link where the initial control frame was received. Each non-AP MLD may or may not support the EMLSR operation mode.

[0101] In the EMLMR mode, a non-AP MLD can aggregate a part of multiple radio physical resources unique to multiple active links (so-called EMLMR links) to transmit and receive data of the supported Rx / Tx spatial streams up to a pre-defined number. Since this pre-defined number is larger than the number of Rx / Tx spatial streams supported per radio, throughput improvement and latency reduction are provided. As an example, a multi-radio (MR) non-AP MLD that supports the EMLMR mode on two links (using the relevant radios) communicates on two links using two respective radios when the EMLMR mode is deactivated, for example, in the 2x2 MIMO antenna configuration of each radio. On the other hand, when the EMLMR mode is activated, the MR non-AP MLD aggregates the physical resources (typically antennas) of two radios and communicates via one of the two links using one of the radios, for example, in the 4x4 MIMO antenna configuration. It is not possible to use the other link (the link deprived of the physical antenna) simultaneously.

[0102] When activated, the EMLMR mode listens simultaneously to the activated links of the configured "EMLMR links" for the non-AP MLD to receive the initial frame transmitted by the AP MLD and start frame exchange, and then can perform the data frame exchange with the AP MLD (aggregating radio resources) via only one EMLMR link at a time, usually the link that received the initial frame. The frame exchange sequence initiated by the AP MLD can be either a Trigger Based (TB) Downlink (DL) transmission or a Trigger Based (TB) Uplink (UL) transmission on the link where the initial frame was received.

[0103] With the introduction of MLO, the D2.0 standard also defines a Traffic IDentifier (TID)-To-Link mapping mechanism. This mechanism enables AP MLDs and non-AP MLDs that have executed or are executing a multi-link setup to determine how UL and DL QoS traffic corresponding to TID values from 0 to 7 is assigned to the setup links of the non-AP MLD.

[0104] By default, all TIDs must be mapped to all setup links for both DL and UL, and all setup links are enabled. Non-AP MLDs and AP MLDs that have performed a multi-link setup shall operate in this mode (i.e., the default TID-to-Link mapping) if no negotiation for TID-to-link mapping for different mappings has occurred, has failed, or has been aborted.

[0105] The D2.0 specification defines a procedure that enables TID-To-Link mapping negotiation in DL and / or UL between the initiating MLD and the responding MLD. An MLD can support TID-to-link mapping negotiation. An MLD that supports TID-To-Link mapping negotiation has dot11TIDtoLinkMappingActivated equal to true. In a multi-link (re)setup procedure, a non-AP MLD can initiate TID-to-link mapping negotiation by including a TID-to-link Mapping element in the (Re)Association Request frame. After the multi-link (re)setup, to negotiate a new TID-to-link mapping, the initiating MLD must send an individually addressed TID-to-link Mapping Request frame to the responding MLD. Next, the responding MLD must send an individually addressed TID-to-link Mapping Response frame to the initiating MLD and either accept the request, reject the request, or propose another TID-to-link mapping. If two MLDs have negotiated a TID-to-link mapping, either MLD can tear down the negotiated TID-to-link mapping by sending an individually addressed TID-to-link Mapping Teardown frame.

[0106] For example, in the MLD Capabilities indicated in the Common Info field of the Basic Multi-Link Information Element included in a (Re)Association Request or Response frame, the TID-To-Link mapping Negotiation Supported subfield indicates support for TID-To-Link mapping negotiation, and the explanations corresponding to the values specified for this 2-bit subfield are summarized in the following table: TIFF2025521400000002.tif103161

[0107] An MLD that does not support TID-To-Link mapping negotiation must set dot11TIDtoLinkMappingActivated equal to false and the TID-To-Link Mapping Negotiation Supported subfield to 0. In this case, the default TID-To-Link mapping is applied.

[0108] An MLD that supports TID-to-link mapping negotiation must set dot11TIDtoLinkMappingActivated equal to true and the TID-to-link Mapping Negotiation Supported subfield in the MLD Capabilities and Operations field of the Basic Multi-Link element being transmitted to a non-zero value.

[0109] If the TID-to-link Mapping Negotiation Supported subfield value received from a peer MLD is 1, the MLD that initiates TID-to-link mapping negotiation with the peer MLD must send a TID-to-link Mapping element in which each TID is mapped to the same or different link sets.

[0110] When the value of the TID-to-link Mapping Negotiation Supported subfield received from the peer MLD is 2, the MLD that starts the TID-to-link mapping negotiation with the peer MLD shall send only TID-to-link Mapping elements in which all TIDs are mapped to the same link set (e.g., all setup links (idem Default mapping) or a subset of the setup links).

[0111] In the following description, mainly the EMLSR mode will be described for simplicity. However, similar considerations are also possible for the EMLMR mode.

[0112] FIG. 1 shows a typical 802.11 network environment including ML transmission between EML-compatible MLDs (compatible with EMLSR and EMLMR) in which the present invention is implemented.

[0113] The wireless communication network 100 includes 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-compatible and declare their capabilities corresponding to the AP MLD 110 within the EMLSR-related field and the EMLMR-related field of the EML Capabilities (these fields are hereinafter referred to as EMLSR Capabilities and EMLMR Capabilities, i.e., sub-parts of the EML Capabilities). Of course, other numbers of non-AP MLDs registered with the AP MLD 110 and exchanging frames with the AP MLD 110, or other (more) numbers of EML-compatible non-AP MLDs are also assumed.

[0114] The AP MLD110 has a plurality of subordinate APs, exemplified in FIG. 1 as two subordinate APs 111 and 112 (also referred to as AP1 and AP2 respectively), each of which operates as an 802.11 AP on an operating channel within one frequency band. Known 802.11 frequency bands include the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. Of course, other frequency bands may be used instead of, or in addition to, these three frequency bands.

[0115] The non-AP MLDs 120 and 130 have a plurality of subordinate non-AP STAs that each operate as an 802.11 non-AP STA in a BSS registered (managed by the subordinate AP 111 or 112). In the exemplary FIG. 1, two non-AP STAs 121 and 122 (also referred to as A1 and A2 respectively) belong to the non-AP MLD120, and two non-AP STAs 131 and 132 (also referred to as B1 and B2 respectively) belong to the non-AP MLD130.

[0116] For the purpose of illustration, the non-AP MLDs 120 and 130 are non-AP MLDs of a single radio. For example, AP111 is set to operate on channel 38 corresponding to a 40 MHz channel during operation in the 5 GHz frequency band, and AP112 is set to operate on channel 151 corresponding to another operating 40 MHz channel in the same 5 GHz frequency band. In another example, the subordinate STAs can operate in different frequency bands.

[0117] Each affiliated AP provides a link to the AP MLD110 for the non - AP STA affiliated with the non - AP MLD (120 or 130). Thus, the link of each non - AP MLD can be simply identified using the identifier of its respective affiliated AP. In this context, each affiliated AP111 and 112 can be identified by an identifier called "link ID". The link ID of each affiliated AP is unique and does not change during the lifetime of the AP MLD. The AP MLD can assign a link ID to the affiliated AP by incrementing the ID (for the first affiliated AP) from 0. Of course, in a variant, other expressions such as "AP ID" may be used.

[0118] To perform multi - link communication, each non - AP MLD120, 130 needs to discover, authenticate, associate, and configure multiple links with the AP MLD110, and each link is established between the affiliated AP of the AP MLD110 and the non - AP STA affiliated with the non - AP MLD. Each such link, called an "enabled link", enables individual channel access and frame exchange between the non - AP MLD and the AP MLD based on the supported capabilities exchanged during the association.

[0119] The discovery phase is hereinafter called the ML discovery procedure, and the multi - link setup phase (or association phase) is hereinafter called the ML setup procedure.

[0120] The ML discovery procedure enables a non-AP MLD to discover various links to the wireless communication network 100, i.e., the AP MLD provided by a plurality of subordinate APs. Therefore, the ML discovery procedure attempts to advertise the various subordinate APs of the AP MLD together with their respective network information including, for example, all or part of the capabilities and operating parameters. When the non-AP MLD discovers the wireless communication network 100 through the ML discovery procedure, after the MLD authentication procedure, the ML setup procedure can select a set of setup link candidates between its subordinate non-AP STA and some of the discovered subordinate APs and request the AP MLD 110 to set up these links, and the AP MLD can accept or reject this. If the AP MLD accepts, the non-AP MLD is provided with an Association Identifier (AID) by the AP MLD, and this AID is used by the subordinate non-AP of the non-AP MLD for wireless communication via a plurality of links (communication channels) with the corresponding subordinate AP. During the ML setup procedure, the non-AP MLD declares some or all of its capabilities. For example, the non-AP MLD declares the EMLSR capability. For this purpose, appropriate fields are prepared in the management frame. Specifically, the management frames exchanged during the ML discovery and ML setup procedures include a new information element specific to Multi-Link Operation (MLO) called Basic Multi-Link Element. In fact, in all management frames including the Basic Multi-Link Element except the Authentication frame, a non-AP or AP MLD corresponding to EMLSR (dot11EHTEMLSROptionImplemented is true) or EMLMR (dot11EHTEMLMROptionImplemented is true) sets the EMLSR or EMLMR Support bit to 1 in the EML Capabilities subfield of the Common Info field.

[0121] For illustration purposes, in a wireless communication network 100, during the ML setup procedure, two candidate setup links are requested by non-AP MLD 120 and accepted by AP MLD 110: a first link 151 between the home AP 111 (AP1) and the home non-AP STA 121 (A1), and a second link 152 between the home AP 112 (AP2) and the home non-AP STA 122 (A2). Similarly, two setup link candidates are requested by multi-radio non-AP MLD 130 and accepted by AP MLD 110: a first link 161 between the home AP 111 (AP1) and the home non-AP STA 131 (B1), and a second link 162 between the home AP 112 (AP2) and the home non-AP STA 132 (B2).

[0122] 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 EMLSR or EMLMR capabilities (a subpart of EML Capabilities) during the ML discovery procedure and the multi-link setup phase.

[0123] As currently defined in the D2.0 standard, EMLSR and EMLMR Capabilities include the following subfields: - An "EMLSR Support" subfield indicating support for EMLSR operation for the MLD. The EMLSR Support subfield is set to 1 if the MLD supports EMLSR operation and 0 otherwise; - A 3-bit subfield, "EMLSR Padding Delay", indicating the minimum MAC padding time of the Padding field of the initial control frame required by a non-AP MLD, as defined in Enhanced multi-link 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 associated station from the listening operation state to the frame exchange enabled / disabled state. This transition period is the sum of this delay and the time duration of the initial control frame response described later. Therefore, this transition period is hereinafter referred to as "EMLSR active switch delay"; - A 3-bit subfield, "EMLSR Transition Delay", indicating the transition delay time required for a non-AP MLD to switch from the so-called frame exchange mode (in one of the enabled links) to the so-called listening operation mode in the enabled link. The table converts the 3-bit value to the 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 from 6 to 7 are reserved; - An "EMLMR Support" subfield indicating support for EMLMR operation for the MLD. The EMLMR Support subfield is set to 1 if the MLD supports EMLMR operation and 0 otherwise; - When operating in EMLMR mode, a 3-bit subfield, "EMLMR Delay", indicating the minimum padding time required for a non-AP MLD for EMLMR link switching. This delay is used to define the transition period required for the MLD to switch the state of the station it belongs to when starting or ending a frame exchange; the transition period for the start of a frame exchange is the sum of this delay and the duration of the initial frame response as described later. Therefore, this start transition period is hereinafter referred to as "EMLMR active switch delay". - A "Transition Timeout" subfield indicating the timeout value for the EML Operating Mode Notification frame exchange in EMLSR (or EMLMR).

[0124] When a non-AP MLD capable of executing EMLSR (respectively EMLMR) attempts to operate in the corresponding mode on a set of active links called EMLSR (respectively EMLMR) links, the STA belonging to that non-AP MLD transmits an EML Operation Mode (OM) Notification frame having the EMLSR (respectively EMLMR) Mode subfield of the EML Control field set to 1 (as defined in the D2.0 standard) to the AP belonging to the AP MLD capable of executing EMLSR (respectively EMLMR) (here, AP MLD110). The EMLSR (respectively EMLMR) links are indicated by setting the bit positions of the EMLSR (respectively EMLMR) Link Bitmap subfield in the EML Control field of the EML OM Notification frame to 1 for each of those EMLSR (respectively EMLMR) links. 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.

[0125] Upon receiving an EML Operation Mode Notification frame from a STA belonging to a non-AP MLD, the AP belonging to the AP MLD shall then, as a confirmation response to the EML Operating Mode Notification frame transmitted by the STA belonging to the non-AP MLD, start from the end of the PPDU transmitted by the AP belonging to the AP MLD and, during the timeout period indicated by the Transition Timeout subfield in the EML Capabilities subfield of the Basic Multi-Link Element, transmit an EML Operation Mode Notification frame to one of the STAs belonging to the non-AP MLD.

[0126] After the successful transmission of an EML Operation Mode Notification frame in one of the EMLSR (EMLMR respectively) links by the STA belonging to the non-AP MLD, the non-AP MLD operates in the EMLSR (EMLMR respectively) mode and is considered EMLSR-active (EMLMR-active respectively).

[0127] When a non-AP MLD capable of executing EMLSR attempts to disable the EMLSR (EMLMR respectively) mode, the STA belonging to the non-AP MLD shall transmit an EML Operation Mode (OM) Notification frame (specified in the D2.0 standard) with the EMLSR (EMLMR respectively) Mode subfield of the EML Control field set to 0 to the AP belonging to the AP MLD. Also in this case, the AP belonging to the AP MLD that has received the EML Operation Mode Notification frame from the STA belonging to the non-AP MLD shall transmit the EML Operation Mode Notification frame as described above as a confirmation response to the EML Operation Mode Notification frame. After the successful transmission of the EML Operation Mode Notification frame in one of the EMLSR (EMLMR respectively) links of the STA belonging to the non-AP MLD, the non-AP MLD shall disable the EMLSR (EMLMR respectively) mode.

[0128] The set of STAs belonging to a non-AP MLD capable of executing EMLSR (EMLMR respectively) operating on the EMLSR (EMLMR respectively) link can be all or part of the STAs belonging to the non-AP MLD. This set of STAs is hereinafter referred to as the "EMLSR co-affiliated STAs" (EMLMR co-affiliated STAs respectively) of the non-AP MLD.

[0129] In the example of FIG. 1, the EMLSR co-affiliated STAs of non-AP MLD120 and non-AP MLD130 operate on the same link (i.e., the same affiliated APs AP1 and AP2).

[0130] FIG. 1a shows an exemplary 802.11be multi-link reference model for an MLD that is either an AP MLD or a non-AP MLD.

[0131] The MLD has a PHY layer 200, a MAC layer 220, a logical link control (LLC) sublayer, and upper layers.

[0132] The upper layers may include an application that generates traffic data or uses the received traffic data.

[0133] The transmission and reception of traffic data are processed by the MAC layer 220 and the PHY layer 200. Such transmission and reception of traffic data may be performed via a plurality of links 20-x, 20-y, 20-z, such as 151, 152, 161, 162 introduced with reference to FIG. 1. Three links, and thus three associated stations, are shown. Of course, other configurations including two associated stations or more than three associated stations are also conceivable.

[0134] Traffic data is provided from the upper layer as a series of data frames, i.e., a "traffic stream". Each traffic stream, i.e., each data frame, is associated with an access category (AC) as defined by the EDCA mechanism (FIG. 1b). This mapping between the stream or data frame and the AC is performed by the classifier 213.

[0135] It is recalled that 802.11 stations (APs and non-AP stations) hold four access categories (ACs), and each AC has one or more corresponding transmission buffers or queues. The four ACs are conventionally defined as follows: - AC1 and AC0 are reserved for best effort and background traffic. These traffics have the second lowest priority and the lowest priority, respectively. - AC3 and AC2 are usually reserved for real-time applications (e.g., voice and video transmission). They have the highest priority and the second highest priority, respectively.

[0136] Data frames, also known as MAC service data units (MSDUs), input from the upper layers of the protocol stack are mapped by classifier 213 to one of the four ACs and thus input to the queue of the mapped AC.

[0137] Figure 1b shows an implementation model with four transmission queues, one for each access category.

[0138] The 802.11be multi-link reference model reflects the fact that the MLD can transmit and receive using multiple links, especially at the levels of the MAC layer 220 and the PHY layer 200.

[0139] The MAC layer 220 includes one Unified Upper-MAC (UMAC) layer 230 and multiple Lower-MAC (LMAC) layers 220-x, 220-y, 220-z combined with their respective PHY layers 200-x, 200-y, 200-z, and each combination corresponds to a link 20-x, 20-y, 20-z.

[0140] The UMAC 230 performs functions common to all links, and each LMAC 220-x, 220-y, 220-z performs functions local to each link 20-x, 20-y, 20-z. And the UMAC layer provides a UMAC interface to the link-specific blocks 220-x, 220-y, 220-z and a UMAC service access point (SAP) to the LLC and upper layers.

[0141] The UMAC 230 is responsible for MAC procedures that are independent of the link, such as authentication, association, security association, sequence number assignment, encryption / decryption of the MAC Protocol Data Unit (MPDU), aggregation / de-aggregation, and acknowledgment scoring procedures.

[0142] Each data unit (MSDU) arriving at the MAC layer 220 from a higher layer (e.g., Link layer) having a traffic type (User Priority (UP), and thus Traffic IDentifier (TID)) priority is mapped to one of the ACs according to the mapping rules in the UMAC layer 230. Then, also in the UMAC layer 230, the next sequence number available for the data unit (MSDU) is provided and stored in the queue corresponding to that TID (or UP) within the mapped AC. It is recalled that an 802.11 station maps TIDs to ACs as follows (TIDx refers to TID = x): - TID1 and TID2 are typically mapped to AC0, which is used for background traffic, - TID0 and TID3 are typically mapped to AC1, which is used for best-effort traffic, - TID4 and TID5 are typically mapped to AC2, which is used for video traffic, - TID6 and TID7 are typically mapped to AC3, which is used for voice traffic.

[0143] Each LMAC 220-x, 220-y, 220-z is responsible for link-specific functions such as channel access. In particular, the Lower MAC of each MLD includes its own contention-based channel access procedure such as EDCA 221-x, 221-y, 221-z. Some functions require joint processing by both the UMAC 230 and the LMAC 220-x, 220-y, 220-z.

[0144] As shown in FIGS. 1a and 1b, each EDCA221-x, 221-y, 221-z per link performs contention for each AC queue per link. In that regard, each AC has a set of its own queue contention parameters (i.e., EDCA access parameters) per link, which are associated with a priority value, and thus define higher or lower priority traffic for MSDUs. In this way, there are multiple traffic queues for providing data traffic at different priorities for a given link. Arbitration Inter-frame space (AIFSn), contention window (CW), and backoff value are known as EDCA access parameters and are specific to each AC of each link 20-x, 20-y, 20-z.

[0145] In the case of MLD, each AC or traffic queue 210 is mapped to one EDCA engine 221 per link. Thus, each backoff entity 211 of the EDCA engine 221 dedicated to a link uses the queue contention parameters to initialize the backoff counter (BC) of its respective queue specialized for each AC and per link, and is associated with each AC queue 210 for drawing the backoff value. In FIG. 1b, the backoff counters BC[x0], BC[x1], BC[x2], BC[x3] are associated with the traffic queues 210 of AC0, AC1, AC2, AC3, respectively, and are used simultaneously for contention for access to link 20-x. Similarly, the backoff counters BC[y0], BC[y1], BC[y2], BC[y3] are associated with the traffic queues 210 of AC0, AC1, AC2, AC3, respectively, and are used simultaneously for contention for access to link 20-y. Similarly, the backoff counters BC[z0], BC[z1], BC[z2], BC[z3] are associated with the traffic queues 210 of AC0, AC1, AC2, AC3, respectively, and are used simultaneously for contention for access to link 20-z.

[0146] The backoff counter is used for contention for access to link 20-x, 20-y, or 20-z in order to transmit the data stored in the AC queue of the AP. In fact, the backoff counter is decremented from the initial value when the medium is idle, and when the backoff counter reaches 0, transmission is permitted (access is permitted) to the corresponding affiliated STA201-x, 201-z.

[0147] When access to the wireless medium is permitted for an AC on a given link, the MSDUs stored in the traffic queue 210 corresponding to that AC are transmitted to the physical (PHY) layers 200-x, 200-y, 200-z for transmission via the given link.

[0148] Figure 2 shows, using a frame sequence, the EMLSR operation mode in the non-AP MLD120 when the AP MLD110 determines to use the EMLSR mode. Of course, here the EMLSR mode is emphasized as an example, but similar considerations are also possible for the EMLMR mode.

[0149] In this sequence, the non-AP MLD operates in the EMLSR mode, which means that an EML Operation Mode Notification frame that activates the EMLSR mode has been successfully transmitted by the associated STA of the non-AP MLD120. In other words, the non-AP MLD has entered the active Enhanced Multi-Link Single Radio (EMLSR) mode applied to a specific set of two or more active links.

[0150] The affiliated STAs 121 and 122 are EMLSR co-affiliated STAs within the non-AP MLD120. Each affiliated STA can be in one of three defined states (listening operation state, frame exchange enabling state, and frame exchange disabling state).

[0151] The non-AP MLD120 can listen in parallel on its EMLSR links by putting the EMLSR co-associated STAs corresponding to those links into the "awake" or "listening operation" state. For example, the associated STAs A1 and A2 are in the listening operation state (see 241, 242). The listening operation includes CCA (Clear Channel Assessment) and the reception of an initial control frame for frame exchange initiated by the AP MLD. Therefore, in the non-AP MLD120, two EMLSR co-associated STAs wait in parallel for the reception of the initial control frame from the AP MLD.

[0152] When the AP MLD110 attempts to start a frame exchange with one or more non-AP MLDs on one of the EMLSR links, it starts the frame exchange by transmitting an initial control frame 245 that explicitly triggers the non-AP MLD. To some extent, the initial control frame schedules the non-AP MLD. The initial control frame for frame exchange is transmitted in the OFDM PPDU or non-HT duplicate PPDU format using a rate of 6 Mbps, 12 Mbps, or 24 Mbps (i.e., the MCS subfield in the frame is set to the maximum value 2). As defined in the D2.0 standard, the initial control frame must be a MU-RTS trigger frame or a BSRP trigger frame as defined in IEEE Std802.11ax TM -2021. Considering the trigger frame format in which such a frame includes one or more User Info fields, this condition means that frame 245 contains a User Info field addressed to the non-AP MLD, i.e., the AID12 field is set to the AID of the non-AP MLD (obtained at registration).

[0153] As shown in this embodiment and by reference "IC(A)", the initial control frame 245 explicitly triggers the non-AP MLD A120. The initial control frame may use a plurality of User Info fields therein to explicitly trigger a plurality of non-AP MLDs.

[0154] The EMLSR co-associated STA of the non-AP MLD explicitly triggered by the initial control frame 245 that received the frame, for example, the associated STA A1 in this example, starts a state change of the EMLSR co-associated STA of the non-AP MLD to be considered, for example, the state changes of the associated STAs A1 and A2 in this example, and transmits an initial control frame response (IC resp) 246 to AP1, which is the AP belonging to the AP MLD110.

[0155] After receiving the initial control frame of frame exchange 245 and transmitting the immediate response frame 246 as a response to the initial control frame, the STA belonging to the non-AP MLD that had been listening on the corresponding link, that is, the receiving-side EMLSR co-owned STA A1 in this example, is configured to be able to transmit or receive frames on the active link where the initial control frame 245 was received, that is, link 151 in this example. For this purpose, the state switching procedure is activated when the frame 245 is received. As a result, the receiving-side EMLSR co-owned STA switches from the listening operation state 241 to the "active frame exchange" or "activation frame exchange" state referred to by 251 in the figure after the EMLSR active switching delay. The receiving-side EMLSR co-owned STA in this new state can receive a PPDU transmitted using a plurality of spatial streams on the link where the initial control frame 245 was received. 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 Padding Delay): the time length of the initial control frame response 246 plus the EMLSR Padding Delay.

[0156] In parallel, other EMLSR co-owned STAs of the same non-AP MLD, that is, STA A2 in this example, are configured not to transmit or receive on other EMLSR links until the frame exchange is completed. For this purpose, the state switching procedure is also activated for the other EMLSR co-owned STAs, and each of these STAs is sequentially switched from the listening operation state 242 to the "blind frame" or "deactivation frame exchange" state referred to by 252 in the figure. In particular, the AP MLD does not transmit data to these other EMLSR co-owned STAs.

[0157] The problem is that all wireless resource chains (see Figure 11 below) are assigned to one of the STAs, and no such chain is assigned to the others. Therefore, the state switching of the STAs co-belonging to the same non-AP MLD in the EMLSR is indivisible and occurs simultaneously. Regarding the EMLMR mode, the physical resources (e.g., antennas) of one wireless resource chain are assigned (aggregated) to other wireless resource chains, so the former is deprived of its transmission and reception capabilities (see Figure 12 below).

[0158] The above shows that when the non-AP MLD operates in the EMLSR mode (more generally, either the EMLSR mode or the EMLMR mode), it is either in the listening operation mode (where its co-belonging STAs are in the listening operation state) or the frame exchange mode (where one of its co-belonging STAs is in the frame exchange enabled state and the other co-belonging STAs are in the frame exchange disabled state).

[0159] It can be seen that only one of the EMLSR co-belonging STAs of the explicitly triggered non-AP MLD can perform a data frame exchange with the AP MLD at a time, which is usually the EMLSR co-belonging STA that has received the initial control frame 245.

[0160] An exemplary frame exchange sequence is shown in the figure, which includes the transmission (therefore downlink transmission) of the A-MPDU frame 255 by the co-belonging AP AP1 to the EMLSR co-belonging STA A1 of the explicitly triggered non-AP MLD A120, followed by the corresponding Block Acknowledgement 256 from the EMLSR co-belonging STA A1 of the non-AP MLD A120.

[0161] In addition to the end of frame exchange operated by the receiving - side EMLSR co - affiliated STA, when the EMLSR Transition Delay specified in the EML capabilities has elapsed, the non - AP MLD120 returns to the EMLSR listening operation state, which means that the receiving - side EMLSR co - affiliated STA A1 switches to the listening operation state 241, similar to the other EMLSR co - affiliated STA A2 (listening operation state 242). Therefore, for each of the EMLSR co - affiliated STAs, the state - switching procedure is initiated.

[0162] When any of the following conditions is met, frame - end exchange can be sensed by the non - AP MLD, here non - AP MLD120.

[0163] (1) The MAC of the STA belonging 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, starting from the end of the PPDU (e.g., acknowledgment 256) transmitted from the STA of the non - AP MLD as a response to the frame (e.g., A - MPDU frame 255) most recently received from the AP belonging to the AP MLD, or at the end of the reception of a PPDU (e.g., something) containing a frame that does not immediately require an acknowledgment from the AP belonging to the AP MLD to the STA. This indicates that the actual exchange with the AP MLD has ended without receiving a subsequent frame from the AP MLD.

[0164] (2) Starting from the end of reception of a PPDU (e.g., acknowledgment 256) transmitted by an STA belonging to a non-AP MLD as a response to a frame (e.g., A-MPDU frame 255) most recently received from an STA belonging to the non-AP MLD, which is received by the MAC of the STA belonging to the non-AP MLD that has received the initial control frame 245, or starting from the end of reception of a PPDU including a frame for which an acknowledgment is not immediately required, including a frame from an AP belonging to an AP MLD addressed to an STA, within the time-out interval of aSIFSTime + aSlotTime + aRxPHYStartDelay, the PHY-RXSTART.indication primitive is received, and the STA belonging to the non-AP MLD does not detect any of the following frames within the PPDU corresponding to the PHY-RXSTART.indication: - An individually addressed frame having an RA equal to the MAC address of the STA belonging to the non-AP MLD, - A trigger frame having one User Info field addressed to the STA belonging to the non-AP MLD, - A CTS-to-self frame having an RA equal to the MAC address of the AP belonging to the AP MLD, - A Multi-STA BlockAck frame having one AID TID Info field addressed to the STA belonging to the non-AP MLD, - An NDP announcement frame having one STA Info field addressed to the STA belonging to the non-AP MLD.

[0165] This corresponds to the case where, after an actual exchange with the AP MLD, the non-AP MLD receives another frame from the AP MLD that is not addressed to itself (i.e., there is no data addressed to itself or no resources are allocated to itself).

[0166] (3) The STA belonging to the non-AP MLD that has received the initial control frame 245 does not respond to a frame (e.g., A-MPDU frame 255) most recently received from an AP belonging to the AP MLD that requires an immediate response after SIFS.

[0167] Here, since non-AP MLD120 is in the EMLSR listening operation mode, AP MLD can start a new frame exchange sequence (with either non-AP MLD120 or 130) by transmitting a new initial control frame.

[0168] In the example of the figure, AP MLD110 decides to start such a new sequence again with non-AP MLD120 using its own EMLSR co-associated STA A2 122. Specifically, AP MLD110 transmits a new initial control frame 265 IC(A) that explicitly triggers non-AP MLD A120 using another associated AP 112, and this frame is received by EMLSR co-associated STA A2 122. The receiving EMLSR co-associated 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 MLD120 switches to the EMLSR frame exchange mode, the receiving EMLSR co-associated STA A2 122 switches from the listening operation state 242 to the frame exchange enabling state 272, and at the same time, the other EMLSR co-associated STA A1 121 switches from the listening operation state 241 to the frame exchange disabling state 271. Frames 275 and 276 are exchanged during the frame exchange sequence until the sequence ends when non-AP MLD120 returns to the EMLSR listening operation mode.

[0169] The A-MPDU 255 / 275 is provided for illustrative purposes only. For example, other types of frames, such as a basic trigger frame for triggering UL transmission, may be transmitted by the AP MLD. FIG. 2 shows a frame exchange composed of a single frame 255 / 275 followed by a confirmation response 256 / 276. However, a simpler frame exchange may be composed of only a single frame transmitted by the AP MLD without a confirmation response. On the other hand, a more complex frame exchange may be composed of multiple exchange sequences, such as a cascade TXOP for UL transmission (triggered by a basic trigger frame) and / or for DL transmission (via an HE MU PPDU).

[0170] 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, thus improving communication performance while suppressing increases in complexity and cost.

[0171] As described above, the foregoing description also applies to the EMLMR mode, especially with the following correspondences: The EMLMR Delay applies to both the EMLSR Padding Delay and the EMLSR Transition Delay; the initial frame of the EMLMR mode corresponds to the initial control frame of the EMLSR mode, and similarly, the initial frame response of the EMLMR mode corresponds to the initial control frame response of the EMLSR mode; although not defined in the D2.0 standard, the EMLMR listening operating state / mode can be defined to correspond to the EMLSR listening operating state / mode in which the co-located STAs are listening to the link before the aggregation of physical radio resources.

[0172] FIG. 3 shows an example of a MAC data frame including a Buffer Status Report Control Field (BSR Control field) according to 802.11ax.

[0173] The illustrated MAC data frame 400 includes a MAC header 410, a frame body 420, and an FCS field 430. The MAC header 410 includes, among other things, a Frame Control header 411, a QoS control field 412, and an HT control field 413. The QoS control field 412 is in the original 802.11e format that can be used by non-AP stations of 802.11 technology to report buffer status. Alternatively, or additionally, non-AP stations starting from the 802.11ax version (including further releases such as 802.11be / EHT) can use the HT control field 413 to do so.

[0174] Therefore, field 413 can be referred to as the HT or HE or EHT control field without distinction according to the generation of 802.11 (802.11ac, 802.11ax, or 802.11be respectively) when provided within the 802.11 MAC data frame 400.

[0175] 802.11 Legacy BSR Format: As illustrated, the QoS control field 412 is composed of 2 bytes and includes the following information items: - Bits B0 to B3 are used to store a traffic identifier (TID) 404 that identifies a traffic stream. The traffic identifier takes on the value of a transmission priority value (User Priority UP, a value between 0 and 7) corresponding to the data carried by the data frame, or takes on the value of a traffic stream identifier (TSID, a value between 8 and 15) for another data stream; - Bit B4 is used by non-AP stations to distinguish the meaning of bits B8 to B15; - Bits B5 and B6 define the ACK policy subfield and specify the acknowledgment policy associated with the data frame. This subfield is used to determine how the data frame must be acknowledged by the receiving station, whether it is a normal ACK, no ACK, or block ACK. - Bit B7 is reserved and not used in the current 802.11 standard. - When bit B4 is set to 1, bits B8 - B15 represent the "queue size" subfield 403 for indicating the amount of buffered traffic for TID404 specified by bits B0 - B3 in the non-AP station transmitting this frame. The queue size value is rounded up to the nearest multiple of 256 octets and represents the total size of all packets buffered for the specified TID in units of 256 octets. The access point can use this information to determine the next TXOP period to grant to the station. A queue size of 0 indicates no traffic buffered for that TID. A queue size of 255 indicates an unspecified or unknown size for that TID404. - When bit B4 is set to 0, instead of "queue size", bits B8 - B15 represent the "TXOP Duration Requested" subfield. This indicates, in units of 32 μs, the time that the transmitting station has determined is required for the next TXOP for the specified TID. Naturally, "TXOP Duration Requested" can provide an equivalent request to "queue size" considering all packets buffered for the TID for which both are specified.

[0176] The following description is in the "queue size" format for buffer status reports because it is the most commonly used (the "TXOP Duration Requested" format is deprecated for multi-user applications). The 802.11e MAC frame format, particularly the QoS Control field 412, is maintained for the new standard version as described here.

[0177] A legacy BSR compliant with 802.11e can handle one TID report per MSDU frame, which is one of the reasons why the extension was later provided by the 802.11ax version.

[0178] 802.11ax BSR Format: The HT-Control field 413 can aggregate multiple (N in the figure) control fields, resulting in a series of one or more control sub-fields 450. The length of the aggregated control field (A-Control field) 413 is equal to 30 bits.

[0179] Each control sub-field 450 includes a Control ID451 sub-field that indicates the type of information carried in the subsequent Control Information sub-field 452. Padding bits are added if necessary to reach 30 bits for the A-Control field.

[0180] Thus, depending on the Control ID451, various types of information can be provided through the A-Control field 413. For example, when the Control ID451 is 1, the operating mode can be indicated in the Control Information sub-field 452. Also, when the Control ID451 is 4, power data can be indicated in the Control Information sub-field 452.

[0181] When the Control ID subfield 451 is 3, the Control Information subfield 452 of the Control subfield 450 includes buffer status information in the format of the BSR control field shown in the figure under the reference number 460.

[0182] Non-AP stations may report buffer status for the priority AC or all AC queues. The buffer status information 460 consists of six subfields: ACI Bitmap 461, Delta TID 462, ACI High 463, Scaling Factor 464, Queue Size High 465, and Queue Size All 466.

[0183] The number N of traffic identifiers for which buffered uplink (UL) traffic exists TID is signaled using the first two subfields of the BSR Control field 460, namely ACI Bitmap 461 and Delta TID 462.

[0184] The ACI Bitmap subfield 461 has 4 bits and indicates the access categories for which 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, and to 0 otherwise.

[0185] An exception is the special case where the buffer status of all eight TIDs is included in the Queue Size All subfield 466. In that case, the ACI Bitmap subfield = 0 is combined with the Delta TID subfield 462 set to 3.

[0186] Together with the value of the ACI Bitmap subfield, the Delta TID subfield 462 indicates the number of TIDs for which the non-AP station is reporting buffer status. The following table shows the relationship between these two subfields and the number of TIDs. This table is cited from Table 9-24e of document 802.11ax, version 8.0. TIFF2025521400000003.tif116161

[0187] The ACI High subfield 463 is used to indicate the ACI (Access Control Identifier) of the priority AC for which the buffered traffic volume is specified by the Queue Size High subfield 465.

[0188] The Scaling Factor subfield 464 indicates the unit SF of the Queue Size High subfield 465 and the Queue Size All subfield 466 in octets.

[0189] The Queue Size High subfield 465 indicates the buffered traffic volume in units of SF octets for the AC identified by the ACI High subfield 463, for the station (usually an AP) identified by the receiving address of the MAC frame 400.

[0190] The Queue Size All subfield 466 indicates the buffered traffic volume in units of SF octets for all the ACs identified by the ACI Bitmap subfield 461, for the station (usually an AP) identified by the receiving address of the MAC frame 400.

[0191] The queue size values set in the Queue Size High subfield 465 and the Queue Size All subfield 466 are the total size of all MSDUs and A-MSDUs buffered in the non-AP station reporting buffer status, rounded up to the next multiple of the SF octet.

[0192] The standardized 802.11ax BSR is dedicated to reporting buffer status from one (or more) of the four queues. This format no longer conforms to TID values greater than 7, whereas the legacy format still does. For example, the upper layer may provide a data frame (MSDU) with an 802.1D User Priority (UP) value taken from the values 8 to 15 reserved for low-latency delivery services (known as TSID).

[0193] The current BSR procedure provides a protocol for the AP to obtain the buffer status of each AC, i.e., each traffic, on the non-AP side so that the AP can send a trigger frame to trigger UL traffic. Therefore, the current BSR approach enables the non-AP MLD to globally provide transmission needs to the AP MLD without considering that the AP MLD can schedule data transmission on a link-by-link basis.

[0194] However, when scheduling on the link, the AP MLD does not have accurate link-related information. For example, the AP MLD may not be aware of a failure on some links. In fact, when selecting a link, the AP MLD does not provide any guarantee regarding the latency, reliability, and jitter of the transmission, which mainly depends on the wireless reception on the non-AP MLD side.

[0195] In fact, since the non-AP MLD is well aware of the wireless environment, if it knows that some wireless links are experiencing interference, the non-AP MLD is in an advantageous position to determine the optimal link for data transmission at a given time.

[0196] Therefore, an AP MLD that only considers competition between stations may sometimes give an uplink transmission opportunity to an inappropriate station on a link.

[0197] Figures 4a and 4b described below propose using a specific buffer status report adapted for a multi-link device, a multi-link buffer status report (ML-BSR), whereby each non-AP MLD can report, for all traffic or for a given traffic (s), the amount of buffered data waiting to be transmitted, along with the link identified by the non-AP MLD and expected to be scheduled to transmit the amount of data reported by the non-AP MLD.

[0198] Upon receiving such an ML-BSR, the AP MLD will have additional information regarding the link that the non-AP considers suitable for subsequent scheduling of UL transmissions in SU or MU mode.

[0199] A general format of the multi-link buffer status report (ML-BSR) dedicated to multi-link devices is shown in Figure 4a.

[0200] The proposed format 500 is intended to be general in the sense that it can be rejected in a new independent format as shown in Figure 4a, or parts of the format can be added to various existing types of reports of 802.11ax buffer status, for example, as shown in Figure 4b.

[0201] In some embodiments, at least a portion of report 500 is carried via the A-Control subfield 413 of the MAC header 410, as shown in FIG. 3. For example, if the Control ID subfield 451 takes the value 7 and the values from 8 to 15 remain reserved, it can be indicated in the Control Information subfield 452 (see FIG. 4a).

[0202] Hereinafter, report 500 is referred to as a multi-link buffer status report (ML-BSR). According to some embodiments, the use of ML-BSR is indicated via a new entry 505 in the Control ID table of the A-Control field (e.g., a Control ID having one value between 7 and 14).

[0203] As can be seen in FIG. 4a, the ML-BSR includes an indication regarding the amount of data waiting to be transmitted, which is associated with a link indication that the non-AP ML expects data transmission.

[0204] Thus, the ML-BSR 500 is composed of a Traffic ID subfield 501, an Amount of data subfield 502, and a Link ID 503.

[0205] The first field 501 includes an indication regarding the type of data to which the ML-BSR is applied.

[0206] The type of data is, for example, the traffic for which the ML-BSR is issued. Depending on the delivery service negotiated between the ML AP and the non-AP ML station that generates the report, the traffic indication may appear to have two forms: a report per class and a report per flow.

[0207] Traffic flows with the same class also share the same traffic queue. Therefore, in the per-class report, that traffic queue is considered within the report: and the indication will be either an AC value indicating the access category or a TID (i.e., User priority) indicating the type of traffic.

[0208] Moreover, format 500 includes an indication related to the amount of data waiting to be sent by a non-AP MLD. Amount of data 502 corresponds to the count of buffered data units related to the current buffer report, i.e., the data units related to the traffic considered in the ML-BSR.

[0209] Furthermore, format 500 consists of indications related to the links that the station expects to be scheduled by the AP MLD. The non-AP MLD that recognizes a failure occurring in that link, i.e., the affiliated station, provides in the ML-BSR an indication of at least one link that is optimal for transmitting the amount of data waiting to be sent. Moreover, when selecting a link, the non-AP MLD may further consider the reported amount of data.

[0210] In Figure 4a, the Link ID subfield 503 indicates the link identifier of the reporting MLD to which the reported amount of data is related. The Link ID subfield is set to 15 when the reported amount of data is global and there is no portion that needs to be transmitted on a given link, or when the reporting device does not have that information.

[0211] Link ID is the current information of the AP and helps to simplify and optimize the scheduling of the next communication slot for the indicated link. Note that the term "AP ID" may be used instead of "Link ID".

[0212] Therefore, such an ML-BSR is a means for the non-AP MLD on the transmitting side to assist the AP MLD on the scheduling side in order to ensure that all waiting data is delivered on the intended link on time.

[0213] The ML-BSR is "live" information or temporary information for subsequent scheduling.

[0214] The ML-BSR is transmitted from the non-AP MLD using any of the enabled links between the non-AP MLD and the AP MLD, regardless of the Link ID shown in the report.

[0215] Receiving such an ML-BSR at the AP helps the AP MLD manage traffic. In fact, the ML-BSR is used by the non-AP MLD and, when using a per-class reporting format considering multiple flows, notifies the AP MLD of the need for instantaneous global transmission on a given link for a given traffic.

[0216] Here, another example of the ML-BSR will be described in relation to FIG. 4b. The non-AP MLD can deliver the ML-BSR in the BSR Control subfield 460 of any frame transmitted to the AP, for example, in response to an ML-BSRP trigger frame.

[0217] 802.11be / EHT stations (AP and non-AP) may set the ML-BSR Support subfield in the EHT Capabilities element they transmit to 1; otherwise, the station may set the MS-BSR Support subfield to 0. Therefore, the ML-BSR Support subfield is used by the non-AP MLD to indicate to the AP MLD whether the non-AP MLD supports the ML-BSR during the association procedure.

[0218] Figure 4B shows the ML-BSR 506 based on the BSR Control field 460 of FIG. 3 according to 802.11ax.

[0219] The ML-BSR 506 has fields, the ACI Bitmap field 461, the Delta TID field 462, the ACI High field 463, the Scaling Factor 464, and the Queue Size High 465, which were described in relation to the 802.11ax format BSR.

[0220] In addition to these known subfields, a Link ID field 603 is added.

[0221] The ML-BSR report format corresponds to the following fields: the ACI High field 463, the Scaling Factor 464, the Queue Size High 465, and the Link ID field 603.

[0222] The ACI High subfield indicates the ACI of the AC shown by the ML-BSR in the Queue Size High subfield.

[0223] 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, in the Queue Size High 465, the AC for which the buffer state is reported, that is, the amount of data waiting to be transmitted for the indicated AC, and corresponds to the field 502 in FIG. 4a.

[0224] Still, the Scaling Factor subfield indicates the unit SF of the Queue Size High subfield in octets.

[0225] The unit used for the reported data amount is specified by the Scaling Factor subfield 464.

[0226] The Queue Size High subfield indicates, in SF octet units, the buffered traffic volume of the AC identified by the ACI High subfield, which is intended to be delivered to the STA identified by the reception address of the frame containing the ML-BSR Control subfield, via the link specified by the Link ID subfield.

[0227] Therefore, the Queue Size High subfield 465 corresponds to the field 502 in Figure 4a.

[0228] ML-BSR further includes an indication related to the link for which the station is expected to be scheduled to transmit the buffered data specified by Queue Size High 465. This indication is configured in the Link ID field 603 and indicates that the buffered data of Queue Size High 465 is intended to be delivered via the link specified by the Link ID subfield.

[0229] The Link ID subfield 603 is 4 bits long and indicates a link identifier for the purpose of the reporting STA to transmit the specified data traffic volume. The STA (e.g., AP MLD) identified by the reception address of the frame containing the ML-BSR Control subfield is expected to schedule the buffered frames at the station that outputs ML-BSR for delivery on the link specified by this Link ID subfield 603.

[0230] The other subfields are not used in the ML-BSR report.

[0231] According to the 802.11ax standard, the ACI Bitmap subfield 461 indicates the access category for which the buffer status is reported, i.e., Queue Size All 466.

[0232] According to some embodiments, Queue Size All466 may not be reported. Thus, the position of the Queue Size All subfield may be used for the Link ID subfield 603. A specific number of bits of the ACI Bitmap subfield 461 set to 0 may indicate that the report is an ML-BSR so that the change of location is correctly interpreted.

[0233] As a result, the receiving station regards the buffer status 506 as an ML-BSR if the ACI Bitmap subfield is 0 and the Delta TID subfield is different from 3 (since this value is already used in 802.11ax in this context where the ACI Bitmap is set to 0).

[0234] According to some embodiments, since the Delta TID subfield is not applicable to 802.11ax, it is set to 0.

[0235] The context of the present invention described above with reference to FIGS. 1, 1a, 1b, 2, 3, 4a, and 4b emphasizes that the new EML operation and the new TID-to-Link mapping mechanism currently defined in IEEE P802.11be / D2.0 may be affected by the lack of rules for their efficient coexistence.

[0236] In the EMLMR or EMLSR frame exchange operation initiated by the AP MLD as currently defined in IEEE P802.11be / D2.0, the selection of the EMLMR or EMLSR link used in the frame exchange sequence is performed by the AP MLD when transmitting the initial frame or the initial control frame. Currently, the rules regarding the matching between this selected EMLMR link or EMLSR link and the TID-To-Link mapping used between the AP MLD and the non-AP MLD are not specified in the standard. In some situations, especially for TB UL traffic, the lack of this rule can lead to some mismatches and inefficiencies.

[0237] As a first example, in the case of a BSRP trigger frame in which the initial frame or the initial control frame is transmitted by the AP MLD under the negotiated uplink TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield set to 1, the BSR response frame transmitted by the non-AP MLD may report the buffered traffic of some TIDs that are not mapped to the link on which the BSRP TF was received. In such a case, the trigger of the non-AP MLD for UL transmission by the AP MLD on this link is wasted, and the entire initiated EML operation is inefficient.

[0238] As a second example, under the Default TID-To-Link mapping or the uplink TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield set to 2, if the initial frame or the initial control frame is a BSRP trigger frame transmitted by the AP MLD, the ML-BSR response frame transmitted by the non-AP MLD may indicate a link for transmitting buffered traffic that is not the link on which the BSRP TF was received. In such a case, the trigger by the non-AP MLD for UL transmission by the AP MLD on this link may fail because the local conditions (such as interference) of the non-AP MLD are not considered. In such a case, again, the entire initiated EML operation becomes inefficient.

[0239] An object of the present invention is to harmonize the operation of the EML mode, whether it is EMLMR or EMLSR, with the uplink TID-To-Link mapping for trigger-based uplink traffic transmission.

[0240] Hereinafter, embodiments of the present invention for achieving this object will be described with reference to FIGS. 5a, 5b, 5c, 6, 7, 8, 9, and 10. These embodiments are as follows: 1. New signaling that enables EMLSR or EMLMR to operate under the currently specified EML operation or under a new EML operation for operation TB UL traffic. 2. New rules for matching the UL TID-To-Link mapping with the currently specified EML operation for operation TB UL traffic. The purpose is to cover the inefficiencies of the current EML operation, and without such rules, the BSR frame response may be wasted. 3. New EML operations for operation TB UL traffic that enable EML link switching based on the content of the BSR frame response.

[0241] In this specification, the above-mentioned 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.

[0242] From the perspective of the non-AP MLD, the signaling information indicates which of the following two sub-modes of the EML mode to use: In response to a BSRP trigger frame received from the AP MLD via a predetermined EML link among a set of EML links, the non-AP MLD transmits, via the predetermined EML link, a BSR frame as a function of UL TID-To-Link mapping for buffered traffic (e.g., if there is buffered traffic for at least one UL TID mapped to the predetermined EML link according to UL TID-To-Link mapping, that buffered traffic) to the AP MLD. The first sub-mode of the EML mode, and In response to a BSRP trigger frame received from the AP MLD via the first EML link, the non-AP MLD transmits, via the first EML link, a BSR frame indicating a selected EML link among a set of EML links to be used for frame exchange to the AP MLD. The second sub-mode of the EML mode.

[0243] From the perspective of the AP MLD, the signaling information indicates which of the following two sub-modes of the EML mode to use: The first sub-mode of the EML mode, including transmission by the AP MLD of a basic TF including constraints based on UL TID-To-Link mapping regarding UL resources scheduled for the non-AP MLD and data to be transmitted within the scheduled UL resources, and The second sub-mode of the EML mode where the AP MLD obtains an indication of the selected EML link to be used for frame exchange from the BSR frame and transmits a basic TF to the non-AP MLD via the selected EML link to trigger uplink frame exchange with the non-AP MLD at the selected EML link.

[0244] Figure 5a shows the EML Capabilities subfield in the Common Info field of the Basic Multi-Link Element, which is defined in the IEEE P802.11be / D2.0 standard and enhanced with new fields according to embodiments of the present invention.

[0245] During the ML setup procedure, the AP MLD and the non-AP MLD declare some or all of their capabilities. For example, they may declare EMLSR capabilities and / or EMLMR capabilities. As will be described later, appropriate fields are provided in management frames such as, for example, ML Association Request / Response frames.

[0246] The management frames exchanged during the ML discovery procedure and the ML setup procedure include a new multi-link (ML) information element specific to multi-link operation (MLO), called the Multi-Link element. In particular, the ML Association Request / Response frames exchanged during the setup procedure are Association Request / Response defined in 802.11ax (e.g., IEEE P802.11ax / D8.0 of October 2020) with the addition of the Basic Multi-Link element defined in IEEE P802.11be / D2.0, where the AP MLD and the non-AP MLD can declare EML capabilities among other declarations.

[0247] The EML Capabilities subfield 520 is used to declare the MLD capabilities regarding extended multi-link, particularly EMLSR and EMLMR. This includes the EMLSR Support subfield 521, EMLSR Padding Delay subfield 522, EMLSR Transition Delay subfield 523, EMLMR Support subfield 524, EMLMR Delay subfield 525, Transition Delay subfield 526, and Reserved subfield 227.

[0248] The details of these subfields are described in the IEEE P802.11be / D2.0 standard.

[0249] In Figure 5a, the EML Capabilities subfield 520 is enhanced with a new subfield 528 according to an embodiment of the present invention. This new subfield 528 is used for the AP MLD and non-AP MLD to declare support for the new EML operations described in the present invention.

[0250] When the MLD supports both the current EML operation and the new EML operation for trigger-based uplink EML frame exchange, that is, the EML frame exchange on the link where the BSRP TF is transmitted / received and the EML frame exchange on the link implicitly or explicitly indicated in the BSR frame for trigger-based uplink EML frame exchange respectively, preferably, the Link Indication for UL EML Frame Exchange Mode subfield 528, which is a 1-bit subfield, is set to 1.

[0251] The Link Indication for UL EML Frame Exchange Mode subfield 528, which is preferably a 1-bit subfield, is set to 0 when the MLD supports only the current EML operation for trigger-based uplink EML frame exchange, i.e., supports only EML frame exchange on the link where the BSRP TF was transmitted / received for trigger-based uplink EML frame exchange.

[0252] Figure 5B shows the format of the EML Control field of the EML OM Notification frame used to activate or deactivate the EML mode enhanced with fields according to embodiments of the present invention and defined in the IEEE P802.11be / D2.0 standard.

[0253] The EML Control field 540 of the EML OM Notification frame includes a 1-bit EMLSR Mode subfield 541, a 1-bit EMLMR Mode subfield 542, an EMLSR Link bitmap subfield 543, a reserved subfield 544, an EMLMR Link bitmap subfield 545, an MCS Map count subfield 546, and an EMLMR Support MCS and NSS set subfield 547.

[0254] A non-AP MLD that supports EMLSR operation (as declared in the EML capabilities) sets the EMLSR Mode subfield 541 to 1 to request activation of the EMLSR mode and indicates the relevant EMLSR link in the EMLSR Link bitmap 543. This indicates that the non-AP MLD intends to operate in the EMLSR mode. A non-AP MLD that supports EMLSR (as declared in the EML capabilities) sets the EMLSR Mode subfield 541 to 0 to indicate that it no longer intends to operate in the EMLSR mode.

[0255] Similarly, a non-AP MLD that supports EMLMR operation (as declared in the EML capabilities) sets a 1 in the EMLMR Mode subfield 542 to request activation of the EMLMR mode and indicates the relevant EMLMR link in the EMLMR Link bitmap 545. This indicates that the non-AP MLD is attempting to operate in the EMLMR mode. A non-AP MLD that supports EMLMR operation (as declared in the EML capabilities) sets a 0 in the EMLMR Mode subfield 542 to indicate that it no longer intends to operate in the EMLMR mode.

[0256] In the D2.0 standard, it is stated that the two modes of EMLSR and EMLMR are mutually exclusive.

[0257] Details of these subfields are described in the IEEE P802.11be / D2.0 standard.

[0258] In Figure 5b, the EML Control field 540 is enhanced with a new subfield 548 according to an embodiment of the present invention. This new subfield 548 is used by the non-AP MLD to indicate to the AP MLD the EML operation mode used for the requested activation of EMLSR or EMLMR. In such a case, the EML operation mode is driven by the non-AP MLD, and all trigger-based uplink EML frame exchanges with the AP MLD that occur during the activation of this EMLSR or EMLMR use this same EML operation mode.

[0259] To indicate the use of a new EML operation for trigger-based uplink EML frame exchange, i.e., to indicate that EML frame exchange is performed on the link implicitly or explicitly indicated in the BSR frame for trigger-based uplink EML frame exchange, the Link Indication for UL EML Frame Exchange Mode subfield 548, which is preferably a 1-bit subfield, is set to 1.

[0260] The Link Indication for UL EML Frame Exchange Mode subfield 548, which is preferably a 1-bit subfield, is set to 0 to indicate the use of the current EML operation for trigger-based uplink EML frame exchange, i.e., to indicate that EML frame exchange is performed on the link on which the BSRP TF was transmitted / received for trigger-based uplink EML frame exchange.

[0261] Figure 5c shows the format of a trigger frame enhanced with two possible variations of a new field defined in the IEEE P802.11be / D2.0 standard and according to an embodiment of the present invention.

[0262] It should be understood that these two possible variations constitute a first variation and a second variation with respect to the embodiment described above with reference to Figure 5b.

[0263] The trigger frame 560 is a BSRP trigger frame based on the trigger frame format defined in IEEE802.11ax (HE) with some fields modified as defined in IEEE802.11be / D2.0 (ETH).

[0264] The trigger frame 560 includes a MAC header 561, a Common Info field 562, a User Info List field 563, a Padding field 564, and an FCS field 565.

[0265] The Common Info field 562 is typically an EHT - modified Common Info field with a Trigger Type set to a value 4 corresponding to the BSRP trigger frame.

[0266] The User Info field 563 includes one of a plurality of EHT - modified User Info fields 566.

[0267] The details of these fields are described in IEEE Std802.11ax TM - 2021 and IEEE P802.11be / D2.0 specifications.

[0268] In the first variant of FIG. 5c, the Common Info field 562 is enhanced with a new sub - field 568a according to an embodiment of the present invention. This new sub - field 568a is used by the AP MLD and indicates the EML operation mode for the next trigger - based uplink EML frame exchange for the addressed non - AP MLDs. In such a case, the EML operation mode is driven by the AP MLD for the next trigger - based uplink EML frame exchange for all non - AP MLDs addressed by the BSRP trigger frame 560, meaning that all non - AP MLDs use the same EML operation mode.

[0269] The Link Indication for UL EML Frame Exchange Mode sub - field 568a is typically a 1 - bit sub - field and, as an example, uses one of the EHT reserved bits 56 - 62 available in the EHT - modified Common Info field 562, or, as another example, uses a 1 - bit in the EHT Trigger Dependent Common Info sub - field added to the EHT Common Info field 562.

[0270] The Link Indication for UL EML Frame Exchange Mode sub-field 568a, which is preferably a 1-bit sub-field, is set to 1 to indicate the use of a new EML operation for the following trigger-based uplink EML frame exchange, i.e., to perform the following EML frame exchange in the link implicitly or explicitly indicated in the BSR frame for the following trigger-based uplink EML frame exchange.

[0271] The Link Indication for UL EML Frame Exchange Mode sub-field 568a, which is preferably a 1-bit sub-field, is set to 0 to indicate the use of the current EML operation for the following trigger-based uplink EML frame exchange, i.e., to perform the following EML frame exchange in the link where the BSRP TF was transmitted / received for the following trigger-based uplink EML frame exchange.

[0272] In the second variant of FIG. 5c, the User Info field 566 is enhanced with a new sub-field 568b according to an embodiment of the present invention. This new sub-field 568b is used by the AP MLD to indicate the EML operation mode used for the following trigger-based uplink EML frame exchange for a given addressed non-AP MLD. In such a case, the EML operation mode is driven by the AP MLD independently of other non-AP MLDs addressed by the BSRP trigger frame 560 for the following trigger-based uplink EML frame exchange for the given non-AP MLD addressed by the BSRP trigger frame 560, meaning that other non-AP MLDs may use the same or different EML operation modes.

[0273] The Link Indication for UL EML Frame Exchange Mode subfield 568b is typically a 1-bit subfield and, by way of example, uses one of the reserved bits 25 available in the EHT modified User Info field 566, or, as another example, uses 1 bit of the EHT Trigger Dependent User Info subfield added in the EHT User Info field 566.

[0274] The Link Indication for UL EML Frame Exchange Mode subfield 568b, which is preferably a 1-bit subfield, is set to 1 to indicate the use of a new EML operation for the next trigger-based uplink EML frame exchange, i.e., to perform the next EML frame exchange on the link implicitly or explicitly indicated in the BSR frame for the next trigger-based uplink EML frame exchange.

[0275] The Link Indication for UL EML Frame Exchange Mode 568b, which is preferably a 1-bit subfield, is set to 0 to indicate the use of the current EML operation for the next trigger-based uplink EML frame exchange, i.e., to perform the next EML frame exchange on the link on which the BSRP TF was transmitted / received for the next trigger-based uplink EML frame exchange.

[0276] Referring to FIGS. 5a, 5b and 5b described above, the names "Link Indication for UL EML Frame Exchange Support" and "Link Indication for UL EML Frame Exchange Mode" have been introduced for the new signaling according to embodiments of the present invention. These names are mainly for illustrative purposes and other names may also be expected.

[0277] FIG. 6 is a diagram showing steps performed by an EML - compliant non - AP MLD according to an embodiment of the present invention using a flowchart, and this flowchart processes a frame exchange sequence shown in an embodiment described with reference to FIGS. 8 and 9 to which steps of the flowchart are referred.

[0278] In step 600, the non - AP MLD executes an ML setup with the AP MLD. During this procedure, the non - AP MLD and the AP MLD specifically exchange EML Capabilities according to the present invention, where each MLD can indicate whether it supports new EML operations via a new sub - field Link Indication for UL EML Frame Exchange Support (reference number 528, FIG. 5a).

[0279] In step 605, optionally, the non - AP MLD and the AP MLD initiate a TID - To - Link mapping procedure to negotiate TID - To - Link mapping in DL, UL, or both. This procedure can be initiated during the ML setup or at any timing after the ML setup. As an example, the non - AP MLD and the AP MLD negotiate the TID - To - Link mapping shown in FIG. 8.

[0280] In step 610, the non - AP MLD enters the EML mode (either the EMLMR mode or the EMLSR mode) by successfully exchanging an EML OM Notification in which the EML Mode sub - field (either the EMLMR mode or the EMLSR mode) of the EML Control field is set to 1 with the EML - compliant AP MLD, where the notification also identifies the MLD link (either the MLDMR link or the EMLSR link), and thus the corresponding EML co - affiliated STA.

[0281] According to an embodiment of the present invention, the non - AP MLD identifies the EML link under Rules 1 and 2 specified in the description of FIG. 8.

[0282] In certain embodiments, these rules can be summarized as follows: Activating the EML mode includes, in the non-AP MLD, selecting a set of EML links to which the EML mode is applied as a function of the UL TID-To-Link mapping, and sending a notification specifying the selected set of EML links to the AP MLD. Details and variations are shown below in the description of FIG. 8.

[0283] As new signaling, the non-AP MLD also indicates, via the new subfield Link Indication for UL EML Frame Exchange Mode (reference 548, FIG. 5b) in the EML Control field 540 (see FIG. 5b) according to an embodiment of the present invention, whether to use the current EML mode operation or the new EML operation for the activated EML mode.

[0284] In other words, the non-AP MLD sends signaling information to the AP MLD indicating which of the aforementioned two "current EML mode operations" and "new EML operations" (also called the first submode and the second submode of the EML mode - see above) should be used. In certain embodiments, the signaling information is included in the subfield (548) of the EML Control field (540) of the EML OM Notification frame sent by the non-AP MLD.

[0285] At that time, the non-AP MLD is in the EML listening operation mode, which means that the EML co-associated STAs are in the listening operation state, and at the same time, they are listening to their respective links.

[0286] In step 615, an initial control frame or an initial frame is received by one of the EML co-associated STAs on the receiving link from the AP MLD.

[0287] Here, the received initial control frame or initial frame is a BSRP trigger frame (TF) as described above in FIG. 5c. The BSRP trigger frame is related to the Buffer Status Report Poll (BSRP) procedure introduced in IEEE Std802.11ax TM -2021, which solicits the uplink data requests of solicited STAs (by specifically requesting the amount of buffered uplink data), enabling the AP to schedule resource allocations for synchronous uplink transmissions. In response to the BSRP trigger frame, each solicited / intended STA can send an immediate feedback buffer status report (BSR), which can be regarded as an initial control frame response or an initial frame response.

[0288] The received BSRP TF typically schedules non-AP MLDS with other non-AP MLDS, or more generally, explicitly triggers one or more recipient STAs.

[0289] As a first variation of the new signaling, the AP MLD indicates in the Common Info field 562 of the BSRP TF (more precisely, in the new subfield "Link Indication for UL EML Frame Exchange Mode" referenced at 568a in FIG. 5c) according to a specific embodiment of the present invention, whether the current EML operating mode or the new EML operating mode should be used for the next UL EML frame exchange for all non-AP MLDS scheduled via the new subfield "Link Indication for UL EML Frame Exchange Mode".

[0290] As a second variation of the new signaling, the AP MLD indicates whether the current EML operating mode or the new EML operating mode should be used for the next UL EML frame exchange for the non-AP MLD scheduled via the new subfield "Link Indication for UL EML Frame Exchange Mode" in the User Info field 566 of the BSRP TF for non-AP MLD according to a particular embodiment of the present invention (more precisely, in the new subfield "Link Indication for UL EML Frame Exchange Mode" referenced at 568b in FIG. 5c).

[0291] In other words, in the first variation of the new signaling, the signaling information is included in the subfield (568a) of the Common Info field (562), and in the second variation of the new signaling, it is included in the subfield (568b) of the User Info field (566) assigned to the non-AP MLD within the BSRP TF transmitted by the AP MLD.

[0292] At step 620, the non-AP MLD checks whether the new EML operating mode should be used by testing whether both the new subfields Link Indication for UL EML Frame Exchange Support and Link Indication for UL EML Frame Exchange Mode are set to 1.

[0293] If the test 620 is negative, the next step is 630, which means that the current EML operation with the new rules specified in the embodiments of the present invention is used.

[0294] If the test 620 is positive, the next step is 640, which means that the new EML operation specified in the embodiments of the present invention is used.

[0295] In step 630, the non-AP MLD starts switching from the listening operation state to the EML frame exchange state of its co-EML affiliated STA. More precisely, on the link where the BSRP TF is received, it starts switching from the listening operation state to the frame exchange enabling state of the receiving side's co-EML affiliated STA. In parallel (simultaneously), on the other link, it starts switching from the listening operation state to the frame exchange disabling state of the other co-EML affiliated STA.

[0296] In step 631, the scheduled non-AP MLD's receiving co-EML affiliated STA transmits an initial control frame response or an initial frame response which is a BSR frame.

[0297] According to a specific embodiment of the present invention, the non-AP MLD transmits a BSR frame based on Rule 4 specified in the description of FIG. 8.

[0298] In a specific embodiment, this rule can be summarized as follows: While the non-AP MLD is operating in the EML mode using a set of EML links, in response to a Buffer Status Report Poll (BSRP) trigger frame received from the AP MLD via the first EML link among the set of EML links, it transmits a BSR frame reporting the buffered traffic to the AP MLD via the first EML link as a function of UL TID-To-Link mapping. Details and variations will be described later in the description of FIG. 8.

[0299] Next, in step 632, the non-AP MLD completes the switch from the EML listening operation state to the EML frame exchange state of its EML co-owned STA. More precisely, in step 633, on the link where the BSRP TF is received, it completes the switch from the listening operation state to the frame exchange enabling state of the received EML co-owned STA. In parallel (simultaneously), in step 634, it starts the switch from the listening operation state to the frame exchange disabling state on the other link of the other EML co-owned STA.

[0300] Next, in step 635, the received EML co-owned STA of the non-AP MLD executes a frame exchange sequence with the corresponding co-owned AP of the AP MLD via the received link, i.e., the link where the BSRP TF is received.

[0301] In step 640, the non-AP MLD starts the switch from the listening operation state to the EML frame exchange state of its EML co-owned STA based on the content of the BSR frame being prepared.

[0302] More precisely, if the BSR frame being prepared implicitly or explicitly indicates that the link used for frame exchange is the received link (i.e., the link where the BSRP TF is received), it starts the switch from the listening operation state to the frame exchange enabling state on the link where the BSRP TF is received for the received EML sharing STA. In parallel (simultaneously), it starts the switch from the listening operation state to the frame exchange disabling state on the other link of the other EML co-owned STA.

[0303] If the BSR frame being prepared implicitly or explicitly indicates that the link used for frame exchange is the other link, it starts the switch from the listening operation state to the frame exchange enabling state on the other link of the other EML sharing STA. In parallel with this (simultaneously), the receiving EML sharing STA starts the switch from the listening operation state to the frame exchange disabling state on the receiving link.

[0304] According to a particular embodiment of the present invention, the non-AP MLD identifies the link to be used for EML frame exchange based on the content of the BSR frame being prepared, according to rules 6, 8, and 9 identified in the description of FIG. 9.

[0305] In a particular embodiment, these rules can be summarized by the fact that the non-AP MLD performs the following actions: - Receive the BSRP TF from the AP MLD via the first EML link of a set of EML links, and - Select, as a function of the UL TID-Link mapping and the buffered traffic to be reported in the BSR frame, the EML link to be used for frame exchange from among the set of EML links, and - Transmit, via the first EML link, a BSR frame indicating the selected EML link to be used for frame exchange to the AP MLD. Details and variations are shown below in the description of FIG. 9.

[0306] In step 641, the scheduled non-AP MLD receiving EML co-owned STA transmits an initial control frame response or an initial frame response that is a BSR frame.

[0307] If the transmitted BSR frame implicitly or explicitly indicates that the link to be used for frame exchange is the received link (i.e., the link on which the BSRP TF was received, Link#1), the next step is step 632, which has already been described.

[0308] If the transmitted BSR frame implicitly or explicitly indicates that the link to be used for frame exchange is the other link, the next step is step 642.

[0309] Next, in step 642, the non-AP MLD completes the switching from the EML listening operation state to the EML frame exchange state of its co-owned STA. More precisely, in step 643, it completes the switching from the listening operation state to the frame exchange enabling state in the other link of the other co-owned STA of the EML. In parallel (simultaneously), in step 644, in the receiving link (i.e., the link that received the BSRP TF, Link#1), it starts the switching from the listening operation state of the receiving-side co-owned STA of the EML to the frame exchange disabling state.

[0310] Next, in step 645, the other co-owned STA of the non-AP MLD executes a frame exchange sequence with the corresponding co-owned AP of the AP MLD via the other link.

[0311] The frame exchange in either step 635 or 645 continues via the link used for the frame exchange (either the receiving link of frame exchange 635 or the other link of frame exchange 645) until the end of the frame exchange is detected in step 650.

[0312] When such an end of frame exchange is detected in test 650, the non-AP MLD returns to the EML listening operation state in step 655. For this reason, the receiving-side co-owned STA corresponding to the receiving link returns to the listening operation state in step 656, and in parallel (synchronously), the other co-owned STAs also return to the listening operation state in step 657.

[0313] FIG. 7 is a diagram showing, using a flowchart, the corresponding steps executed by the EML-corresponding AP MLD according to some embodiments of the present invention. This flowchart processes the frame exchange sequence shown in the embodiments described with reference to FIGS. 8 and 9, to which the steps of the flowchart are referred.

[0314] In this flowchart, the exemplary steps performed by the AP MLD are processed with respect to a given non-AP MLD, meaning that the same process is performed for each non-AP MLD entering the EML mode.

[0315] In step 700, the AP MLD performs an ML setup with the non-AP MLD. During this procedure, the AP MLD and the non-AP MLD exchange, in particular, EML Capabilities according to embodiments of the present invention, and each MLD can indicate whether it supports the new EML operation through the new subfield Link Indication for UL EML Frame Exchange Support.

[0316] In step 705, optionally, the AP MLD and the non-AP MLD initiate a TID-To-Link mapping procedure to negotiate the TID-To-Link mapping in DL, UL, or both. This procedure can be initiated during the ML setup or at any timing after the ML setup. As an example, the AP MLD and the non-AP MLD negotiate the TID-To-Link mapping shown in FIG. 8.

[0317] Step 710 corresponds to successfully exchanging an EML OM Notification with the non-AP MLD so that the non-AP MLD can then enter the EML mode. As described above, the EML OM Notification received from the non-AP MLD identifies the EML link and thus the corresponding EML co-associated STA.

[0318] As a new signaling 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 indicates whether to use the current EML mode operation or a new EML operation for the activated EML mode via a new sub-field Link Indication for UL EML Frame Exchange Mode (reference 548, Figure 5b).

[0319] Next, at step 715, the AP MLD stores the EML link in local memory, among other parameters, and stores the non-AP MLD state as an EML listening operation state. For example, the AP MLD can store in local memory a first indication indicating that the first link of the EML link is in the listening operation state and a second indication indicating that the second link of the EML link is also in the listening operation state.

[0320] Next, at step 720, the AP MLD checks whether the non-AP MLD is in the EML listening operation mode.

[0321] If negative, the process loops back to step 720.

[0322] If positive, the process proceeds to step 725.

[0323] At step 725, the AP MLD checks whether it is necessary to start a frame exchange sequence with one or more non-AP MLDs. Various criteria can be used for each non-AP MLD. For example, the AP MLD may have data in the local buffer to send to the non-AP MLD. As another example, the AP MLD may recognize that the non-AP MLD needs uplink resources. As yet another example, the AP MLD may poll the non-AP MLD to know its buffer status report (BSR).

[0324] If it is negative, the process loops to step 725.

[0325] If it is positive, the AP MLD starts constructing the content of the initial control frame or the initial frame (here the BSRP TF), and the process proceeds to step 730.

[0326] As a first variation of the new signaling, the AP MLD constructs the BSRP TF by indicating in the Common Info field 562, according to a particular embodiment of the present invention, which of the current EML operation mode or the new EML operation mode should be used for the next UL EML frame exchange for all scheduled non - AP MLDs via the new sub - field Link Indication for UL EML Frame Exchange Mode (see 568a, Figure 5c).

[0327] As a second variation of the new signaling, the AP MLD constructs the BSRP TF by indicating in the User Info field 566 of the non - AP MLD, according to a particular embodiment of the present invention, which of the current EML operation mode or the new EML operation mode should be used for the next UL EML frame exchange of the scheduled non - AP MLDs via the new sub - field Link Indication for UL EML Frame Exchange Mode (see 568b, Figure 5c).

[0328] Next, at step 730, the AP MLD checks whether the new EML operation mode should be used by testing whether both the new sub - fields Link Indication for UL EML Frame Exchange Support and Link Indication for UL EML Frame Exchange Mode are set to 1.

[0329] If test 730 is negative, the next step is 740, which means that the current EML operation with the new rules specified in the embodiments of the present invention is used.

[0330] If test 730 is positive, the next step is 750, which means that the new EML operation defined in the embodiments of the present invention is used.

[0331] In step 740, the AP MLD sends a BSRP TF for scheduling one or more non-AP MLDs via a shared link of one of the EML links, called Link#1 for simplicity.

[0332] As described above, in the first or second variation of the new signaling, the AP MLD sends the BSRP TF by setting the new subfield Link Indication for UL EML Frame Exchange Mode to 0, that is, by indicating that the current EML operation mode is used.

[0333] According to a specific embodiment of the present invention, the AP MLD prepares and transmits a BSRP TF frame under rule 3 specified in the description of FIG. 8.

[0334] In step 741, the AP MLD checks whether a BSR frame has been received in time from one or more non-AP MLDs on Link#1.

[0335] If negative, the process loops back to step 720.

[0336] If affirmative, the AP MLD takes into account that the non-AP MLD has completed the switch to the EML frame exchange state. Thus, in step 742, the AP MLD stores such a state in local memory for each of the scheduled non-AP MLDs. For example, the AP MLD may set the first indication for link#1 as the frame exchange enabled state and set the second indication for other EML links as the frame exchange disabled state.

[0337] In step 743, the AP MLD prepares and transmits a basic TF that triggers the non-AP MLD for MU UL OFDMA transmission on Link#1.

[0338] According to a particular embodiment of the present invention, the AP MLD prepares and transmits a basic TF frame under rule 5 specified in the description of FIG. 8.

[0339] In a particular embodiment, this rule can be summarized by the fact that the AP MLD performs the following actions: - Transmit a BSRP TF to the non-AP MLD via the first EML link of a set of EML links; - Receive a BSR frame reporting buffered traffic from the non-AP MLD via the first EML link; - Schedule UL resources for the non-AP MLD via the first EML link and transmit a basic TF including constraints based on UL TID-To-Link mapping for data to be transmitted within the scheduled UL resources.

[0340] Details and variations will be described later in the description of FIG. 8.

[0341] Next, in step 744, the co - belonging AP of the receiving EML of the non - AP MLD and the corresponding co - belonging AP of the AP MLD execute a frame exchange sequence on Link#1 (i.e., the receiving link, i.e., the link on which the BSRP frame was transmitted).

[0342] In step 750, the AP MLD transmits the BSRP TF for scheduling one or more non - AP MLDs via one shared link of the EML link, called Link#1 for simplicity.

[0343] As described above, in the first or second variation of the new signaling, the AP MLD transmits the BSRP TF by setting the new sub - field Link Indication for UL EML Frame Exchange Mode to 1, i.e., by indicating that the new EML operation mode is used.

[0344] In step 751, the AP MLD checks whether a BSR frame has been received in time from one or more non - AP MLDs on Link#1.

[0345] If the answer is negative, the process loops back to step 720.

[0346] If the answer is positive, the process proceeds to step 752.

[0347] In step 752, the AP MLD decodes the BSR frame and determines the link to be used for the next EML frame exchange with the non - AP MLD.

[0348] More precisely, if the received BSR frame implicitly or explicitly indicates that the link to be used for frame exchange is the receiving link (i.e., the link on which the BSRP TF was received, i.e., Link#1), the process proceeds to step 742, which has already been described.

[0349] If the received BSR frame implicitly or explicitly indicates that the link to be used for frame exchange is the other link, the process proceeds to step 753.

[0350] According to a specific embodiment of the present invention, the AP MLD identifies the link to be used for EML frame exchange based on the content of the received BSR frame under rules 7, 8, and 9 specified in the description of FIG. 9.

[0351] In a specific embodiment, these rules can be summarized by the fact that the AP MLD performs the following actions: - Receive from the non-AP MLD a BSR frame in response to a BSRP TF transmitted via the first EML link out of a set of EML links; - Obtain from the BSR frame an indication of the selected EML link to be used for frame exchange among the EML links; - Transmit via the selected EML link to the non-AP MLD a basic TF for triggering an uplink frame exchange with the non-AP MLD at the selected EML link.

[0352] Details and variations will be described later in the description of FIG. 9.

[0353] In step 753, the AP MLD takes into account that the non-AP MLD has completed the switch to the EML frame exchange state. Thus, in step 753, the AP MLD stores such a state in the local memory for each of the scheduled non-AP MLDS. For example, the AP MLD may set the first indication for the other Link as the frame exchange enabled state and set the second indication for Link #1 as the frame exchange disabled state.

[0354] In step 754, the AP MLD prepares and transmits a basic TF that triggers the non-AP MLD for MU UL OFDMA transmission on other links.

[0355] According to a specific embodiment of the present invention, the AP MLD prepares and transmits a basic TF frame under Rule 5 specified in the description of FIG. 8.

[0356] Next, in step 755, the other EML co - affiliated STA of the non-AP MLD and the corresponding co - affiliated AP of the AP MLD execute a frame exchange sequence via the other link.

[0357] The frame exchange in either step 744 or 755 continues via the respective link used for the frame exchange (the receiving link (Link#1) for frame exchange 745 or the other link for frame exchange 755) until the end of the frame exchange is not detected in step 745 or 756, respectively.

[0358] When the end of the frame exchange is detected in step 745 or 756, the process loops back to step 720.

[0359] FIG. 8 schematically shows a first possible operation handled in the flowcharts of FIGS. 6 and 7 using an exemplary sequence of frame exchanges between an EML - corresponding AP MLD and an EML - corresponding non - AP MLD.

[0360] In this FIG. 8, the initial control frame or the initial frame is a BSRP trigger frame, and the initial control frame response or the initial frame response is a BSR frame.

[0361] The same reference as in FIG. 2 corresponds to the same frame / state, etc.

[0362] Here too, AP MLD110 includes two subordinate APs 111 and 112, non-AP MLD120 includes two subordinate STAs 121 and 122, and non-AP MLD130 includes two subordinate STAs 131 and 132.

[0363] In this Figure 8, it is assumed that the two subordinate STAs 121 and 122 of non-AP MLD120, and the two subordinate STAs 131 and 132 of non-AP MLD130 can send BSR frames while in the listening operation state.

[0364] In the embodiment of this Figure 8, and also in the following embodiments described with reference to Figures 9 and 10, unless explicitly shown otherwise, the TID-To-Link mapping shown in the following table is considered to be negotiated first between AP MLD110 and non-AP MLD120, and second between AP MLD110 and non-AP MLD130 (Steps 605, 705): TIFF2025521400000004.tif47161

[0365] In summary, the same Downlink TID-To-Link mapping is negotiated between AP MLD110 and non-AP MLD120, and between AP MLD110 and non-AP MLD130. Under this negotiated DL TID-To-Link mapping, all TIDs are mapped to the link set [Link AP1, Link AP2].

[0366] The same Uplink TID-To-Link mapping is negotiated between AP MLD110 and non-AP MLD120, and between AP MLD110 and non-AP MLD130. In this negotiated UL TID-To-Link mapping, TID0, 3, and 1, 2 are mapped to Link AP1, and TID4, 5 and 6, 7 are mapped to Link AP2.

[0367] In FIG. 8, both non-AP MLDs 120 and 130 are EML active (i.e., either EMLSR active or EMLMR active) using an EML link (i.e., either an EMLSR link or an EMLMR link) corresponding to the EML co-owned STAs 121 and 122 of non-AP MLD 120 and an EML link (i.e., either an EMLSR link or an EMLMR link) corresponding to the EML co-owned STAs 131 and 132 of non-AP MLD 130. Non-AP MLDs 120 and 130 activate the EML mode and indicate the EML link by transmitting an EML OM Notification frame to AP MLD 110 (steps 610, 710).

[0368] Regarding 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.

[0369] Rule 1 : Under the negotiated UL TID-To-Link mapping having the (non-AP MLD) TID-To-Link Mapping Negotiation Supported subfield value = 1, at least one of the EML links indicated in the EML Link Bitmap must have at least one mapped UL TID.

[0370] Rule 2 : Under the negotiated UL TID-To-Link mapping having the (non-AP MLD) TID-To-Link Mapping Negotiation Supported subfield value = 2, the set of EML links indicated in the EML Link Bitmap must not be discontinuous with the set of links to which all UL TIDs are mapped.

[0371] The variation of Rule 1 (the second formulation) is as follows: "Selecting a set of EML links as a function of UL TID-To-Link mapping includes satisfying the constraint that at least one EML link in the set of EML links must have at least one UL TID mapped according to the UL TID-To-Link mapping." According to this variation, the constraint (that at least one EML link in the set of EML links must have at least one mapped UL TID) applies regardless of what the UL TID-To-Link mapping is. Therefore, the first formulation of Rule 1 (when the UL TID-To-Link mapping is the negotiated UL TID-To-Link mapping where the TID-To-Link Mapping Negotiation Supported subfield value is equal to 1) is a specific case of this variation.

[0372] The variation of Rule 2 (the second formulation) is read as follows: "Selecting a set of EML links as a function of UL TID-To-Link mapping includes satisfying the constraint that the set of EML links must not be away from another set of links where all UL TIDs are mapped according to the UL TID-To-Link mapping." According to this variation, the constraint (that the set of EML links must not be discontinuous from the other set of links) applies regardless of what the UL TID-To-Link mapping is. Therefore, the first formulation of Rule 2 (when the UL TID-To-Link mapping is the negotiated UL TID-To-Link mapping where the TID-To-Link Mapping Negotiation Supported subfield value is equal to 1) is a specific case of this variation example.

[0373] In Figure 8, it is considered that AP MLD110, non-AP MLD120, and non-AP MLD130 are operating under the "current EML operation" using the new rules (steps 630 - 635, 740 - 745) identified above. This means that some MLDs set Link Indication for UL EML Frame Exchange Support to 0 during ML setup (steps 600, 700), or set Link Indication for UL EML Frame Exchange Support to 0 when enabling the EML mode (step 610) or when starting UL EML frame exchange (step 740).

[0374] At the beginning of the sequence, both non-AP MLD120 and 130 are in the EML listening operation state, which means that both EML co-associated STAs 121 and 122 of non-AP MLD120 are in the listening operation states 241 and 242, and both EML co-associated STAs 131 and 132 of non-AP MLD130 are in the listening operation states 243 and 244.

[0375] If AP MLD110 wants to start a frame exchange sequence with non-AP MLD A120 and non-AP MLD B130 to know their BSRs, it transmits the BSRP trigger frame 845 (step 740) as an initial control frame or an initial frame received by EML co-associated STA A1 121 of non-AP MLD120 and EML co-associated STA B1 131 of non-AP MLD130 via its affiliated AP, AP1 111. The BSRP trigger frame 845 schedules both non-AP MLD A120 and non-AP MLD B130.

[0376] Regarding the transmitted BSRP frame 845, AP MLD110 applies the following rules defined by a specific embodiment of the present invention.

[0377] Rule 3 :(AP MLD) Under the negotiated UL TID-To-Link mapping with the (AP MLD)TID-To-Link Mapping Negotiation Supported subfield value = 1, the BSRP TF should be transmitted on at least one EML link to which at least one UL TID is mapped.

[0378] The variation of Rule 3 (second formulation) is read as follows: "Transmit a Buffer Status Report Poll (BSRP) trigger frame (TF) to a non-AP MLD via a first active link (e.g., the first EML link) to which at least one UL TID is mapped according to the UL TID-To-Link mapping." This variation applies regardless of what the UL TID-To-Link mapping is. Thus, the first formulation of Rule 3 (when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value equal to 1) is a particular case of this variation.

[0379] In both non-AP MLDs 120 and 130, the reception of the BSRP trigger frame 845 starts an EML switch 270 corresponding to either the aforementioned EMLSR active switch delay or the EMLMR active switch delay (step 630). Both non-AP MLDs 120 and 130 operating under the current EML operation start switching their respective received EML co-owned STAs A1 121 and STA B1 131 on the link where the BSRP TF is received to the frame exchange enabled state, and in parallel (synchronously), both non-AP MLDs 120 and 130 start switching their respective other EML co-owned STAs A2 122 and STA B2 132 on the other link to the frame exchange disabled state.

[0380] On one hand, in response to the BSRP TF845, the EML co - belonging STA A1 121 on the receiving side of the scheduled non - AP MLD A120 transmits a BSR846 indicating the amount of buffered uplink data of the scheduled non - AP MLD A120 (step 631), and the EML co - belonging STA B1 131 on the receiving side of the scheduled non - AP MLD B130 transmits a BSR847 indicating the amount of buffered uplink data of the scheduled non - AP MLD B130.

[0381] Regarding the 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.

[0382] Rule 4 : Under the negotiated UL TID - To - Link mapping with the (non - AP MLD) TID - To - Link Mapping Negotiation Supported sub - field value = 1, in response to the BSRP TF, if there is buffered traffic for at least one TID mapped to the EML link on which the BSRP TF was received, that traffic must be reported.

[0383] The variation of Rule 4 (the second formulation) is read as follows: "The BSR frame reports, if it exists, the buffered traffic for at least one UL TID mapped to the first EML link according to the UL TID - To - Link mapping." This variation applies regardless of what the UL TID - To - Link mapping is. Thus, the first formulation of Rule 4 (when the UL TID - To - Link mapping is a negotiated UL TID - To - Link mapping where the TID - To - Link Mapping Negotiation Supported sub - field value is equal to 1) is a particular case of this variation.

[0384] Another variation of Rule 4 (the third formulation) is read as follows: "The BSR frame reports only the buffered traffic of one or more UL TIDs that are mapped to the first EML link according to the UL TID-To-Link mapping when there is buffered traffic of those UL TIDs." This other variation applies regardless of what the UL TID-To-Link mapping is. However, in a specific implementation of this other variation example, the condition for application is that the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping where the TID-To-Link Mapping Negotiation Supported subfield value is equal to 1.

[0385] According to this rule, the BSR846 transmitted by the non-AP MLD120 at the link AP1 where the BSRP TF845 is received indicates the amount of buffered uplink data with TIDs 0 and 3. Similarly, according to this rule, the BSR847 transmitted by the non-AP MLD130 at the link AP1 where the BSRP TF845 is received indicates the amount of buffered uplink data with TIDs 1 and 2.

[0386] Referring to FIG. 3 above, as an example, BSRs 846 and 847 may use the 802.11ax BSR format 460: - For BSR846, the ACI Bitmap subfield 461 is set to the value "0100" to indicate the buffer data of AC1, the Delta TID subfield 462 is set to the value "01" to indicate the buffered data for two TIDs, and the Queue Size All subfield 466 is set to a value corresponding to the total amount of buffered data for these two TIDs, i.e., TIDs 0 and 3. - For -BSR847, the ACI Bitmap subfield 461 is set to the value "1000" to indicate the buffer data of AC0, the Delta TID subfield 462 is set to the value "01" to indicate the buffered data of two TIDs, and the Queue Size All subfield 466 is set to a value corresponding to the total amount of the buffered data of these two TIDs, i.e., TIDs 1 and 2.

[0387] After the EML switching delay 270, both the scheduled non - AP MLD120 and non - AP MLD130 have completed the switching from the EML listening operation mode to the EML frame exchange mode (step 632). This means that the receiving - side EML co - affiliated STAs A1 121 and B1 131 have respectively switched from the listening operation states 241, 243 to the frame exchange enabling states 251, 253 at link AP1 (step 633), and the other EML co - affiliated STAs A2 122 and B2 132 have respectively switched from the listening operation states 242, 244 to the frame exchange disabling states 252, 254 at link AP2 (634).

[0388] After that, within the started frame exchange sequence (steps 635, 743 - 744), that is, via link AP1 (Link#1), the frame 855 can be exchanged between the belonging AP, AP1 111, and the frame 855. Various types of frames 855 can be used, for example, a downlink HE MU PPDU or a basic TF frame for triggering MU UL OFDMA communication.

[0389] Regarding the basic trigger frame 855, the AP MLD110 applies the following rules specified by a particular embodiment of the present invention.

[0390] Rule 5:(AP MLD) Under the negotiated UL TID-To-Link mapping with the (AP MLD)TID-To-Link Mapping Negotiation Supported subfield value = 1, the Basic TF shall indicate, in the Preferred AC subfield of its Trigger Dependent User Info subfield, the value of the AC corresponding to the UL TID mapped to the link on which the Basic TF is transmitted and received.

[0391] The variation of Rule 5 (second formulation) is read as follows: "Schedule UL resources for non-AP MLDs and, for the data to be transmitted within the scheduled UL resources, the Basic TF including the constraints based on the UL TID-To-Link mapping". This variation applies whatever the UL TID-To-Link mapping is. Thus, the first formulation of Rule 5 (when the UL TID-To-Link mapping is the negotiated UL TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value equal to 1) is a particular case of this variation.

[0392] In a particular implementation of this variant, the constraints on the data transmitted within the scheduled UL resources are indicated by the value of the access category (AC) corresponding to the UL TID that is mapped to the first active 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 Dependent User Info field of the User Info field corresponding to the scheduled UL resources within the basic TF. Also preferably, the constraints on the data transmitted by the non-AP MLD apply when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value equal to 1.

[0393] The AP MLD 110 transmits a basic TF 855 including RU allocation information indicating that resource units are allocated to the scheduled non-AP MLD A 120 and non-AP MLD B 130 via the affiliated AP 111: - Thus, the non-AP MLD A 120 can perform UL EML frame exchange by being scheduled (more generally, explicitly triggered) by the frame 855 and then providing an EHT TB PPDU 856 that collects the buffered data of the UL of the TID reported here by the BSR 846 in response. - Thus, the non-AP MLD B 130 can perform UL EML frame exchange by being scheduled (more generally, explicitly triggered) by the frame 855 and then providing an EHT TB PPDU 857 that collects the buffered data of the UL of the TID reported here by the BSR 847 in response.

[0394] In other words, the BSRP trigger frame 845 is the initial frame that triggers the frame exchange sequence via the first EML link. In a non-AP station, the method includes the following: - Obtaining UL resources scheduled within the frame exchange sequence, and - Transmitting data having a UL TID mapped to the first EML link according to the UL TID-Link mapping reported in the BSR frame within the scheduled UL resources.

[0395] Next, the AP MLD 110 transmits a Block Acknowledgement frame 858 via the affiliated AP 111 to confirm the reception of the EHT TB PPDUs 856 and 857.

[0396] In response to detecting the end of the frame exchange, for example, after the Block Acknowledgement 858 (steps 650, 745), the non-AP MLD A 120 and the non-AP MLD B 130 start an EML switchback 271 to the EML listening operation mode (step 655): the receiving-side EML co-affiliated STAs A1 121 and B1 131 switch back from the frame exchange enabled states 251, 253 to the listening operation states 241, 243, and the other EML co-affiliated STAs A2 122 and B2 132 switch back from the frame exchange disabled states 252, 254 to the listening operation states 242, 244.

[0397] The EML switchback 271 corresponds to either the aforementioned EMLSR Transition Delay or the EMLMR delay.

[0398] FIG. 9 schematically shows a second possible operation addressed in the flowcharts of FIGS. 6 and 7 using an exemplary sequence of frame exchange between an EML-capable AP MLD and an EML-capable non-AP MLD.

[0399] In FIG. 9, the initial control frame or the initial frame is a BSRP trigger frame, and the initial control frame response or the initial frame response is a BSR frame in the context of MU UL OFDMA transmission.

[0400] The same references in FIGS. 2 and 8 correspond to the same frame / state, etc.

[0401] Here too, AP MLD110 includes two subordinate APs 111 and 112, non-AP MLD120 includes two subordinate STAs 121 and 122, and non-AP MLD130 includes two subordinate STAs 131 and 132.

[0402] In FIG. 9, it is assumed that the two subordinate STAs 121 and 122 of non-AP MLD120, and the two subordinate STAs 131 and 132 of non-AP MLD130 can transmit BSR frames while in the listening operation state.

[0403] In the embodiment of FIG. 9, unless otherwise clearly shown, the negotiated TID-To-Link mapping considered first between AP MLD110 and non-AP MLD120, and second between AP MLD110 and non-AP MLD130 is the one described above with reference to FIG. 8.

[0404] In FIG. 9, both non-AP MLD120 and 130 are EML active (i.e., either EMLSR active or EMLMR active) with an EML link corresponding to the EML co-subordinate STAs 121 and 122 of non-AP MLD120 (i.e., either an EMLSR link or an EMLMR link), and an EML link corresponding to the EML co-subordinate STAs 131 and 132 of non-AP MLD130 (i.e., either an EMLSR link or an EMLMR link). Non-AP MLD120 and 130 activate the EML mode and indicate the EML link by transmitting an EML OM Notification frame to AP MLD110 (steps 610, 710).

[0405] In this Figure 9, it is considered that the AP MLD110, the non-AP MLD120, and the non-AP MLD130 are operating under the "new EML operation" defined above (Steps 640 - 645, 750 - 756). This means that the MLD set the Link Indication for UL EML Frame Exchange Support subfield to 1 during the setup of the ML (Steps 600, 700), and set the Link Indication for UL EML Frame Exchange Support subfield to 1 at the start of the EML mode (Step 610) or at the start of the UL EML frame exchange (Step 750).

[0406] At the beginning of the sequence, both the non-AP MLD120 and 130 are in the EML listening operation state, which means that both the EML co-associated STAs 121 and 122 of the non-AP MLD120 are in the listening operation states 241 and 242, and both the EML co-associated STAs 131 and 132 of the non-AP MLD130 are in the listening operation states 243 and 244.

[0407] If the AP MLD110 wants to start a frame exchange sequence with the non-AP MLD A120 and the non-AP MLD B130 to know their BSRs, it transmits the BSRP trigger frame 945 via the AP1 111 which is the home AP, as the initial control frame or the initial frame received by the EML co-associated STA A1 121 of the non-AP MLD120 and the EML co-associated STA B1 131 of the non-AP MLD130 (Step 750). The BSRP trigger frame 945 schedules both the non-AP MLD A120 and the non-AP MLD B130.

[0408] In both non-AP MLD120 and 130, the reception of the BSRP trigger frame 945 starts the EML switch 270 (step 640) corresponding to either the aforementioned EMLSR active switching delay or the EMLMR active switching delay. Both non-AP MLD120 and 130 operating under the new EML operation start the switching of their respective EML co-associated STAs A1 121, 122 and STAs B1, 132 based on the content of their respective BSR frames 946, 947 being prepared before transmission in response to the BSRP trigger frame 945: - The BSR 946 indicating the amount of buffered uplink data with TIDs 0, 3 mapped to link AP1 being prepared by non-AP MLD120, non-AP MLD120 starts the switching of its receiving-side EML co-associated STA A1 121 from the listening operating state in link AP1 to the frame exchange enabled state. In parallel (synchronously), non-AP MLD120 starts the switching of the other EML co-associated STA A2 122 from the listening operating state in the other link to the frame exchange disabled state. - The BSR 947 indicating the amount of buffered uplink data with TIDs 4, 5 mapped to link AP2 being prepared by non-AP MLD130, non-AP MLD130 starts the switching of its receiving-side EML co-associated STA B2 131 from the listening operating state in link AP2 to the frame exchange enabled state. In other words, the selected EML link (link AP2) is the second EML link among a different set of EML links from the first EML link (link AP1) that received the BSRP trigger frame and transmitted the BSR frame, and the non-AP belongs to the non-AP MLD and switches the first STA (STA B2) corresponding to the selected EML link (link AP2) from the listening operating state to the frame exchange enabled state. In parallel (synchronously) with this, non-AP MLD130 starts the switching of its receiving-side EML co-associated STA B1 131 from the listening operating state in the other link to the frame exchange disabled state.

[0409] Here, considering another TID-To-Mapping, e.g., the default TID-To-Link mapping, or the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 2, the BSRs 946 and 947 being prepared can indicate the links (i.e., the priority links) to be used for EML frame exchange as follows: - The BSR 946 being prepared by the non-AP MLD120 is in the format of the ML-BSR as previously described with reference to FIGS. 4a or 4b. This ML-BSR indicates the amount of buffered uplink data with TID = 0, 3 mapped to both Link AP1 and Link AP2, and indicates Link AP1. Next, the non-AP MLD120 starts the switching of its receiving-side EML co-associated STA A1 121 from the standby operating state on Link AP1 to the frame-exchangeable state. In parallel (synchronously), the non-AP MLD120 starts the switching of the other EML co-associated STA A2 122 from the listening operating state on the other link to the frame-exchange-disabled state. - The BSR 947 being prepared by the non-AP MLD130 is in the format of the ML-BSR as previously described with reference to FIGS. 4a or 4b. This ML-BSR indicates the amount of buffered uplink data with TID = 4, 5 mapped to both Link AP1 and Link AP2, and indicates Link AP2. Next, the non-AP MLD130 starts the switching of the other EML co-associated STA B2 132 from the standby operating state on Link AP2 to the frame-exchange-enabled state. In parallel with this (synchronously), the non-AP MLD130 starts the switching of its receiving-side EML co-associated STA B1 131 from the standby operating state on the other link to the frame-exchange-disabled state.

[0410] Under this new EML operation, the link to be used for EML frame exchange by a given non-AP MLD is based on the content of the BSR frame: - The link to be used for frame exchange can be implicitly indicated by the TID reported in the BSR and the knowledge of uplink TID-To-Link mapping. This implicit indication can be particularly relevant to the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 1. - The link to be used for frame exchange can be explicitly indicated by the Link ID shown in the BSR which is the ML-BSR. This explicit indication can be particularly relevant under the default TID-To-Mapping or under the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 2.

[0411] When the preparations for BSRs 946 and 947 are completed, in response to BSRP TF945, the receiving-side EML co-located STA A1 121 of the scheduled non-AP MLD A120 transmits a BSR946 indicating the amount of buffered uplink data of the scheduled non-AP MLD A120 (step 641), and the receiving-side EML co-located STA B1 131 of the scheduled non-AP MLD B130 transmits a BSR947 indicating the amount of buffered uplink data of the scheduled non-AP MLD B130 (step 641).

[0412] Regarding the transmitted BSR frames 946 and 947, both the AP MLD110 and the 7 non-AP MLDs120 and 130 apply the following rules specified by a particular embodiment of the present invention.

[0413] Rule 6:(Non - AP MLD) After receiving a BSRP TF that starts UL EML frame exchange and transmitting a BSR frame as a response to the BSRP TF, the non - AP MLD is assumed to be able to transmit or receive frames on the EML link implicitly or explicitly indicated in the BSR frame, and shall not transmit or receive on other EML links until the frame exchange is completed.

[0414] Rule 7 :(AP MLD) After transmitting a BSRP TF that starts 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.

[0415] Rule 8 :(MLD, i.e., non - AP MLD and AP MLD) In the case of implicit EML link indication in the BSR, the MLD identifies the EML link to be used for frame exchange based on the knowledge of the TID reported in the BSR and the TID - To - Link mapping. In other words, the selected EML link is implicit for one or more TIDs reported in the BSR frame when the UL TID - To - Link mapping is provided. In certain embodiments, the one or more reported TIDs are mapped to a second EML link of a set of EML links and not to the first EML link.

[0416] In Rule 8, the following applies: * The TIDs reported in the BSR frame should preferably be mapped to the same EML link: ·(For some reported TIDs with no ambiguity) Under the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 1, if multiple reported TIDs are mapped to the same EML link, the EML link to be used for frame exchange shall be this same EML link (i.e., the received EML link or another link). *Otherwise, as follows: ·(There is ambiguity because all reported TIDs are mapped to all EML links) Under the default TID-To-Mapping or the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 2, the EML link to be used for frame exchange shall be the received EML link (i.e., the link on which the BSRP TF was received). ·(There is ambiguity because at least two reported TIDs are mapped to at least two different EML links) Under the negotiated TID-To-Link mapping with the TID-To-Link Mapping Negotiation Supported 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 shall be the received EML link (i.e., the link on which the BSRP TF was received).

[0417] Rule 9 :(MLD) In the case of an explicit indication of the EML link in the BSR, the MLD shall identify the EML link to be used for frame exchange by the Link ID shown in the BSR (ML-BSR). In other words, the selected EML link is explicitly indicated in the BSR frame by the Link ID.

[0418] Referring to FIG. 3 above, as an example, BSRs 946 and 947 may use the 802.11ax BSR format 460: - For BSR 946, the ACI Bitmap subfield 461 is set to the value "0100" to indicate buffer data for AC1, the Delta TID subfield 462 is set to the value "01" to indicate buffered data for two TIDs, and the Queue Size All subfield 466 is set to a value corresponding to the total amount of buffered data for these two TIDs, i.e., TID = 0, 3, mapped to the link AP1. - For BSR 947, the ACI Bitmap subfield 461 is set to the value "0010" to indicate buffer data for AC2, the Delta TID subfield 462 is set to the value "01" to indicate buffered data for two TIDs, and the Queue Size All subfield 466 is set to a value corresponding to the total amount of buffered data for these two TIDs, i.e., TID = 4, 5, mapped to the link AP2.

[0419] In this case, using the 802.11ax BSR format, the AP MLD 110 and the non-AP MLD 120 identify the EML link AP1 to be used for frame exchange using the TIDs reported in BSR 946 and the knowledge of the uplink TID-To-Link mapping described above with reference to FIG. 8. Similarly, using the 802.11ax BSR format, the AP MLD 110 and the non-AP MLD 130 identify the EML link AP2 to be used for frame exchange using the TIDs reported in BSR 947 and the knowledge of the uplink TID-To-Link mapping described above with reference to FIG. 8.

[0420] After the EML switching delay 270, both the scheduled non-AP MLD120 and non-AP MLD130 complete the switch from the EML listening operation mode to the EML frame exchange mode (step 642), which means that the receiving-side EML co-associated STA A1 121 and the other EML co-associated STA B2 132 switch from the listening operation state 241 to the frame exchange enabled states 251 and 953 respectively, while the receiving-side EML co-associated STA B1 131 and the other EML co-associated STA A2 122 switch from the listening operation states 243 and 242 to the frame exchange disabled states 954 and 253 respectively in link AP1 and link AP2 (steps 643, 644).

[0421] Frame 955 can then be exchanged within the started frame exchange sequence (steps 645, 743 - 745), i.e., using the belonging AP AP1 111 via link AP1 (Link#1). Various types of frames 955, such as a downlink HE MU PPDU or a basic TF frame for triggering MU UL OFDMA communication, can be used.

[0422] Similarly, frame 955’ can then be exchanged within the started frame exchange sequence (steps 645, 754 - 755), i.e., using the belonging AP AP2 112 via link AP1 (the other link). Various types of frames 955’, such as a downlink HE MU PPDU or a basic TF frame for triggering MU UL OFDMA communication, can be used.

[0423] AP MLD110 transmits a basic TF 955 containing RU allocation information indicating that resource units have been allocated to the scheduled non-AP MLD A120 via the belonging AP AP1 111: - Thus, the non-AP MLD A120 can perform UL EML frame exchange by being scheduled (more generally, explicitly triggered) by frame 955 and then providing a response, here an EHT TB PPDU 956 that collects the buffered data of the UL of the TID reported in BSR 946.

[0424] Next, the AP MLD 110 transmits a Block Acknowledgement frame 958 via the AP 1 111 which is its home AP to confirm receipt of the EHT TB PPDU 956.

[0425] In response to detecting the end of the frame exchange, for example after Block Acknowledgement 958 (steps 650, 745), the non-AP MLD A120 starts an EML switchback 271 to the EML listening operating state (step 655): the receiving-side EML co-located STA A1 121 switches back from the frame exchange enabling state 251 to the listening operating state 241, while the other EML co-located STA A2 122 switches back from the frame exchange disabling state 252 to the listening operating state 242.

[0426] The EML switchback 271 corresponds to either the aforementioned EML SR Transition Delay or EML MR delay.

[0427] In parallel, the AP MLD 110 transmits a Basic TF 955' containing RU allocation information indicating that resource units have been allocated to the scheduled non-AP MLD A130 via the AP 2 112 which is its home AP: - Thus, the non-AP MLD A130 can perform UL EML frame exchange by being scheduled (more generally, explicitly triggered) by frame 955' and then providing a response that collects the buffered data of the UL of the TID reported in BSR 947, here an EHT TB PPDU 956'.

[0428] Variant "MU-RTS / CTS" : Here, in the modification example, before transmitting the basic TF955’, the AP MLD110 transmits the MU-RTS TF960 via the AP2 112 which is the affiliated AP, and the non-AP MLD130 replies with a CTS frame 961 via the affiliated non-AP MLD132. This is related to the so-called MU-RTS / CTS procedure introduced in IEEE Std802.11ax TM -2021 and corresponds to an extension of the RTS / CTS handshake mechanism used to reserve channels in a multi-user UL / DL scenario. This enables the AP to reserve a TXOP for multi-user transmission by transmitting a multi-user request control frame (denoted as the MU-RTS frame) to request the reservation of one or more 20MHz communication channels. In response to the MU-RTS frame, the solicited / intended STA transmits a CTS frame. In this modification example, the MU-RTS frame 960 can constitute an initial control frame or an initial frame at the link AP2, and thus permits several other EML active non-AP MLDs to be triggered in the next UL EML frame exchange at the link AP2. This MU-RTS / CTS procedure also permits protecting the link AP2 with a NAV (i.e., setting a Network Allocation Vector to prevent adjacent stations from starting a transmission opportunity) before the next UL EML frame exchange using a basic frame that can be decoded by legacy stations.

[0429] This modified “MU-RTS / CTS” (where the initial frame is the MU-RTS frame) can be generalized as follows: - In non-AP MLD: Before receiving the basic trigger frame (955’) that schedules UL resources for the non-AP MLD within the frame exchange sequence via a second EML link (link AP2) different from the first EML link (link AP1) that received the BSRP trigger frame (945), receive an initial frame (960) that triggers the frame exchange sequence on the second link; - In AP MLD: Before transmitting the basic trigger frame (955’) that schedules UL resources for the non-AP MLD within the frame exchange sequence via a second EML link (link AP2) different from the first EML link (link AP1) on which the BSRP trigger frame (945) was transmitted, transmit an initial frame (960) that triggers the frame exchange sequence on the second link.

[0430] In a particular embodiment (of the variant “MU-RTS / CTS” or its generalization), the initial frame includes an invitation to other non-AP MLDs triggered in the incoming UL EML frame exchange on the second EML link.

[0431] Next (returning to FIG. 9), the AP MLD 110 transmits a Block Acknowledgement frame 958’ to confirm the reception of the EHT TB PPDU 956’ via the AP 2 112 which is its home AP.

[0432] In response to detecting the end of the frame exchange, for example, after the Block Acknowledgement 958’ (steps 650, 756), the non-AP MLD B130 starts an EML switchback 271 to the EML listening operating state (step 655): The receiving-side EML co-associated STA B1 131 switches back from the frame exchange invalidation state 954 to the listening operating state 243, and the other EML co-associated STA B2 132 switches back from the frame exchange validation state 953 to the listening operating state 244.

[0433] The EML switchback 271 corresponds to either the aforementioned EML SR Transition Delay or EML MR delay.

[0434] FIG. 10 schematically shows a modified example of the second possible operation described with reference to FIG. 9, considering the case of a non-AP MLD of an EML active having specific constraints on the transmission of BSR frames.

[0435] The same references as in FIGS. 2 and 9 correspond to the same frames / states, etc.

[0436] Here too, the AP MLD 110 includes two affiliated APs 111 and 112, the non-AP MLD 120 includes two affiliated STAs 121 and 122, and the non-AP MLD 130 includes two affiliated STAs 131 and 132.

[0437] In FIG. 10, contrary to FIGS. 8 and 9 described above, it is assumed that the two affiliated STAs 121 and 122 of the non-AP MLD 120 and the two affiliated STAs 131 and 132 of the non-AP MLD 130 cannot transmit BSR frames while in the listening operation state, and that they complete the EML switch 1070 and enter the frame exchange enabling state so that they can transmit BSR frames.

[0438] This modification may reflect some constraints related to the hardware implementation of the non-AP MLDs 120 and 130.

[0439] In FIG. 10, the concept of the new EML operation mode of the embodiment of the present invention is the same as that described above with reference to FIG. 9. Therefore, the detailed description thereof will not be repeated here, and only the meaning related to the new assumptions for BSR transmission will be described.

[0440] When the AP MLD110 wants to start a frame exchange sequence with the non-AP MLDs A120 and B130 to know their BSRs, it transmits the BSRP trigger frame 945 as an initial control frame or an initial frame via the home AP, i.e., AP1 111. The BSRP trigger frame 945 is received by the EML co-associated STA A1 121 of the non-AP MLD120 and the EML co-associated STA B131 of the non-AP MLD130. The BSRP trigger frame 945 schedules both the non-AP MLD A120 and the non-AP MLD B130.

[0441] In both the non-AP MLDs 120 and 130, the reception of the BSRP trigger frame 945 starts the EML switch 1070 corresponding to either the EMLSR Padding Delay or the EMLMR Delay as described above. While operating under the new EML operation, since there is a constraint on transmitting the BSR frame while in the frame exchange enabled state, both the non-AP MLDs 120 and 130 start switching from the listening operation states 241, 243 of their respective receiving-side EML co-associated STAs A1 121 and STA B131 to the frame exchange enabled states 251, 1053 on the link where the BSRP TF945 is received, i.e., link AP1, while starting to switch from the listening operation states 242, 244 of their respective other EML co-associated STAs A2 122 and STA B2 132 to the frame exchange disabled states 252, 1054 on the other link, i.e., link AP2.

[0442] After the EML switching delay 1070, both the scheduled non-AP MLDs 120 and 130 complete the switching. Next, in response to the BSRP TF 945, the receiving-side EML co-owned STA A1 121 of the scheduled non-AP MLD A120 transmits a BSR 946 indicating the amount of buffered uplink data of the scheduled non-AP MLD A120, and the receiving-side EML co-owned STA B1 131 of the scheduled non-AP MLD B130 transmits a BSR 947 indicating the amount of buffered uplink data of the scheduled non-AP MLD B130.

[0443] And both non-AP MLDs 120 and 130 may or may not start the subsequent switching of their respective EML co-owned 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 where the BSRP TF was received, i.e., link AP1: - The BSR 946 indicating the amount of buffered uplink data of TID = 0, 3 mapped to link AP1 and transmitted by non-AP MLD120, non-AP MLD120 remains in the same state and there is no need to start the subsequent switching of its EML co-owned STAs A1 121 and STA A2 122. - The BSR947 indicating the amount of buffered uplink data with TIDs = 4 and 5 mapped to the link AP2 and sent by the non-AP MLD130, the non-AP MLD130 needs to start the subsequent switching of its co-EML STAs B1 131 and B2 132. Then, the non-AP MLD130 starts the subsequent EML switching 1070’ at the link AP2 to switch the other co-EML STA B2 132 from the operation disabled state 1054 to the frame exchange enabled state 953. In parallel (synchronously), the non-AP MLD130 starts the subsequent switching of its receiving co-EML STA B1 131 to switch from the frame exchange enabled state 1053 on the link AP1 to the frame exchange disabled state 954.

[0444] Since the remaining part of the frame exchange sequence is the same as that described above with reference to FIG. 9, the repeated description here is omitted.

[0445] It should be noted that this FIG. 10, which is a modification of FIG. 9, cannot be fully handled in the flowcharts of FIGS. 6 and 7. However, those skilled in the art will be able to adapt these flowcharts to the complete handling of this modification as needed.

[0446] FIG. 11 schematically shows the EMLSR corresponding architecture of the MLD. This figure shows an example where two affiliated non-AP STAs share the hardware resources of the non-AP MLD when the EMLSR mode is enabled. The EMLSR-capable architecture of the MLD shown in this figure is for illustrative purposes, and other alternative architectures are also conceivable.

[0447] This architecture includes two radio stacks, a light radio stack and a full radio stack.

[0448] The full radio stack has a full (complete) 802.11be MAC module 800a that exchanges data with the upper layer, a full 802.11be PHY module 805a connected to the full MAC module, a full radio frequency chain 815a connected to the full PHY module, and an antenna 820a connected to the full RF chain via an EMLSR switch 810.

[0449] The light radio stack has a lightweight 802.11be MAC module 800b that exchanges data with the upper layer, a lightweight 802.11be PHY module 805b connected to the lightweight MAC module, a lightweight radio frequency chain 815b connected to the lightweight PHY module, and an antenna 820b connected to the lightweight RF chain via an EMLSR switch 810.

[0450] The EMLSR switch 810 is shared by two radio stacks and is configured to switch the EMLSR co - affiliated STAs from the listening operation state to the frame - exchange enabled state or the frame - exchange disabled state when the EMLSR mode is enabled.

[0451] The radio chain 800a / 805a / 815a is a full (complete) radio resource that enables the reception and transmission of any IEEE802.11 frame. In particular, it includes an encoding module and a decoding module for encoding and decoding any IEEE802.11 frame. On the other hand, the radio chain 800b / 805b / 815b is a function - reduced (or "lightweight") radio resource that enables only the reception and transmission of specific IEEE802.11 frames. In particular, it includes only an encoding module and a decoding module for encoding and decoding specific frames using rates of 6Mbps, 12Mbps, or 24Mbps.

[0452] The figure on the lower left shows the MLD function when the non-AP MLD is in the EMLSR listening operation mode: The common EMLSR switch 810 connects each radio chain 800a / 805a / 815a and 800b / 805b / 815b to the antennas 820a and 820b respectively. Therefore, each radio stack can be used to listen to each link simultaneously. As shown in the figure, two links are available. The full radio chain 800a / 805a / 815a and the antenna 820a are configured to operate on Link 1, and the lightweight radio chain 800b / 805b / 815b and the antenna 820b are configured to operate on Link 2.

[0453] The figure in the center lower shows the MLD function when the non-AP MLD switches to the first EMLSR frame exchange mode. The EMLSR co-associated STAs corresponding to Link 1 are in the frame exchange enabled state, and the other EMLSR co-associated STAs corresponding to Link 2 are in the frame exchange disabled state. In that 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 the antennas 820a / 820b are configured to operate on Link 1. Here, since the full radio chain remains configured to operate on Link 1, the switching time from the EMLSR listening operation state to the frame exchange enabled state can be considered short. In fact, in this case, the switch only includes antenna switching. On the other hand, the common EMLSR switch 810 disconnects the lightweight radio chain 800b / 805b / 815b from the antenna 820b. In this configuration, the lightweight radio chain 800b / 805b / 815b cannot receive or transmit frames on Link 2. And only Link 1 is available.

[0454] The figure on the lower right shows the MLD function when the non-AP MLD switches to the second EMLSR frame exchange mode. The EMLSR co-associated STAs corresponding to Link 2 are in the frame exchange enabled state, and the other EMLSR co-associated STAs corresponding to Link 1 are in the frame exchange disabled state. In that case, the common EMLSR switch 810 connects the full wireless chain 800a / 805a / 815a to both antennas 820a / 820b, and the full wireless chain 800a / 805a / 815a and the antennas 820a / 820b are configured to operate on Link 2. Here, since the full wireless chain switches to operate on Link 2, the switching time from the EMLSR listening operation state to the frame exchange enabled state may be considered long. In fact, in this case, the switching includes both antenna switching and full wireless chain configuration switching. On the other hand, the common EMLSR switch 810 disconnects the lightweight wireless chain 800b / 805b / 815b from the antenna 820b. In this configuration, the lightweight wireless chain 800b / 805b / 815b cannot receive or transmit frames on Link 1. And only Link 2 becomes available.

[0455] The function of the common EMLSR switch 810 clearly shows that since the antenna resources are connected to either one or the other of the STAs and cannot remain available to both STAs simultaneously, the state changes of two EMLSR co-associated STAs within the same MLD are necessarily simultaneous.

[0456] Figure 12 schematically shows the EMLMR corresponding architecture of the MLD. In this figure, when the EMLMR mode is enabled, it takes as an example the case where two affiliated non-AP STAs share antenna resources.

[0457] This architecture includes two wireless stacks, one for each non-AP STA.

[0458] The wireless stack has a full 802.11be MAC module 900a or 900b (exchanging data with the upper layer), 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 two wireless stacks and configured to perform antenna resource aggregation when the EMLMR mode is enabled, and an antenna array 920a or 920b.

[0459] The figure at the lower left shows the function when the non-AP MLD is listening to the initial frame: The common EMLMR switch 910 connects each antenna array to the RF chain. Thus, each wireless stack is full and can, for example, use a 2x2 MIMO antenna configuration to handle each link. As shown in the figure, two links are available.

[0460] The figure in the center lower shows the function of the MLD when the non-AP MLD switches in the first EMLMR frame exchange mode. The EMLMR co-associated STA corresponding to Link 2 is in the frame exchange enabled state, and the other EMLMR co-associated STA corresponding to Link 1 is in the frame exchange disabled state. The common EMLMR switch 910 aggregates the antenna resources to Link 2. To do so, the antenna array 920a of the second wireless stack is connected to the RF chain 915b of the first wireless stack. Thus, the first wireless stack operates in a 4x4 MIMO antenna configuration and can improve the throughput for Link 2. On the other hand, Link 1 becomes unavailable because its antenna array 920a is no longer available for use by the second wireless stack.

[0461] The figure on the lower right shows the function of the MLD when the non-AP MLD switches to the second EMLMR frame exchange mode. The EMLMR co-associated STAs corresponding to Link 1 are in the frame exchange enabled state, and the other EMLMR co-associated STAs corresponding to Link 2 are in the frame exchange disabled state. The common EMLMR switch 910 aggregates the antenna resources to Link 1. To do so, the antenna array 920b of the first radio stack is connected to the RF chain 915a of the second radio stack. Therefore, the second radio stack operates in a 4x4 MIMO antenna configuration and can improve the throughput for Link 1. On the other hand, Link 2 becomes unavailable because its antenna array 920b becomes unavailable for use in the first radio stack.

[0462] The function of the common EMLMR switch 910 clearly shows that the state changes of two EMLMR co-associated STAs within the same MLD are necessarily simultaneous because the antenna resources are connected to either one STA or the other STA, and not available to both STAs simultaneously.

[0463] FIG. 13 schematically shows a communication device 1000 of a wireless network, typically one of the MLDs described above, configured to implement at least one embodiment of the present invention. The communication device 1000 can preferably be a device such as a microcomputer, a workstation, or a lightweight portable device. The communication device 1000 preferably includes a communication bus 1013 and a central processing unit 1001, such as a processor denoted as CPU, connected thereto, and a memory 1003 for storing registers adapted to record executable code of a method according to an embodiment of the present invention or executable code of steps of a method, and variables and parameters necessary for the execution of the method. At least two communication interfaces 1002 and 1002' are each connected via a transmission and reception antenna 1004 and 1004' to a wireless communication network, for example, a communication network according to one of the standards of the IEEE802.11 family. have

[0464] Preferably, the communication bus 1013 provides communication and interoperability between various elements included in or connected to the communication device 1000. The expression of the bus is not limiting. In particular, the central processing unit is operable to communicate instructions directly to any element of the communication device 1000 or through another element of the communication device 1000.

[0465] The executable code can be stored in the memory of a read-only, hard disk, or removable digital medium such as a disk. According to an optional variant, the executable code of the program may be received by the communication network via interface 1002 or 1002' so as to be stored in the memory of the communication device 1000 before being executed.

[0466] In one embodiment, the device is a programmable device that uses software to implement the embodiments of the present invention. However, alternatively, the embodiments of the present invention may be implemented in whole or in part in hardware (for example, in the form of an application-specific integrated circuit (ASIC)).

[0467] As described above, the present invention has been described with reference to specific embodiments. However, the present invention is not limited to specific embodiments, and modifications within the scope of the present invention will be apparent to those skilled in the art.

[0468] Referring to the foregoing exemplary embodiments, many further modifications and variations will be suggested to those skilled in the art, but these embodiments are given by way of example only and are not intended to limit the scope of the invention, which is determined only by the appended claims. In particular, different features from different embodiments may be interchanged where appropriate.

[0469] 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 advantageously used.

Claims

1. In a non-access point (non-AP) multi-link device (MLD) operating in multi-link using Uplink (UL) Traffic Identifier (TID)-To-Link mapping, - activating an Enhanced Multi-Link (EML) mode, which includes, as a function of the UL TID-To-Link mapping, selecting a set of EML links of the links to which the EML mode is applied, and sending a notification identifying the selected set of EML links to an AP MLD, and / or - while the non-AP MLD is operating in EML mode using a set of EML links, in response to a Buffer Status Report Poll (BSRP) trigger frame received from the AP MLD via a first EML link of the set of EML links, sending, via the first EML link, a BSR frame reporting the traffic buffered as a function of the UL TID-To-Link mapping to the AP MLD, A communication method in a wireless network comprising the above.

2. Selecting the set of EML links as a function of the UL TID-To-Link mapping includes satisfying the constraint that at least one EML link of the set of EML links must have at least one UL TID mapped according to the UL TID-To-Link mapping. The communication method according to claim 1.

3. The constraint that at least one EML link of the set of EML links must have at least one UL TID mapped is applicable when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping with a TID-To-Link Mapping Negotiation Supported subfield value equal to 1. The communication method according to claim 2.

4. Selecting the set of EML links as a function of the UL TID-To-Link mapping includes satisfying the constraint that the set of EML links must not deviate from other sets of links in which all UL TIDs are mapped according to the UL TID-To-Link mapping. The communication method according to claim 1.

5. The communication method according to claim 4, wherein when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping with a TID-To-Link Mapping Negotiation Supported subfield value equal to 2, the constraint that the EML link among the set of EML links must not deviate from the other set of links is applicable.

6. The communication method according to claim 1, wherein the BSR frame reports the buffered traffic when there is buffered traffic of at least one UL TID mapped to the first EML link according to the UL TID-To-Link mapping.

7. The communication method according to claim 1, wherein the BSR frame reports only the buffered traffic when there is buffered traffic of one or more UL TIDs mapped to the first EML link according to the UL TID-To-Link mapping.

8. The constraint that the BSR frame reports at least one of the UL TIDs mapped on the first EML link according to the UL TID-To-Link mapping, or only the buffered traffic of one or more mapped UL TIDs, when present, applies when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping with a TID-To-Link Mapping Negotiation Supported subfield value equal to 1. The communication method according to claim 6 or 7.

9. The BSRP trigger frame is an initial frame that triggers a frame exchange sequence via the first EML link, and the communication method is, in the non-AP station, - obtaining UL resources scheduled within the frame exchange sequence; - transmitting data having a UL TID mapped to the first EML link according to the UL TID-Link mapping reported in the BSR frame within the scheduled UL resources; The communication method according to claim 1, further comprising.

10. In the non-AP MLD, the following two sub-modes of the EML mode - The first sub-mode of the EML mode including the transmission of the BSR frame reporting traffic buffered as a function of the UL TID-To-Link mapping, and - In response to a BSRP trigger frame received from the AP MLD via the first EML link, the non-AP MLD transmits, via the first EML link, a BSR frame indicating a selected EML link from among a set of EML links to be used for a frame to the AP MLD. The second sub-mode of the EML mode The communication method according to claim 1, further comprising transmitting signaling information indicating which of the above should be used to the AP MLD.

11. In a non-access point (non-AP) multi-link device (MLD) operating in multi-link using a UL Traffic Identifier (TID)-To-Link mapping and an EML mode applied using a set of EML links, - receiving a Buffer Status Report Poll (BSRP) trigger frame from an AP MLD via a first EML link among the set of EML links; - selecting, from among the set of EML links, an EML link to be used for frame exchange as a function of the UL TID-Link mapping and the buffered traffic reported in the BSR frame; - Transmitting, via the first EML link, the BSR frame indicating the selected EML link to be used for frame exchange to the AP MLD; A communication method in a wireless network including the above.

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

13. The communication method according to claim 12, further including, in the non-AP MLD, after transmitting the BSR frame, switching a first STA belonging to the non-AP MLD and corresponding to the selected EML link from a listening operation state or a frame exchange invalidation state to a frame exchange validation state.

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

15. The communication method according to claim 11, further including, in the non-AP MLD, selecting the set of EML links as a function of the UL ID-To-Link mapping, and transmitting a notification for identifying the selected set of EML links to the AP MLD.

16. In the non-AP MLD, the following two sub-modes of the EML mode - In response to a BSRP trigger frame received from the AP MLD via a predetermined EML link among the set of EML links, when there is buffered traffic of at least one UL ID mapped to the predetermined EML link according to the UL ID-To-Link mapping in the non-AP MLD, transmitting a BSR frame reporting the buffered traffic via the predetermined EML link to the AP MLD, the first sub-mode of the EML mode; - the second sub-mode of the EML mode including the transmission of the BSR frame indicating the selected EML link to be used for the frame exchange, The communication method according to claim 11, further comprising transmitting, to the AP MLD, signaling information indicating which of the above is used. **Claim 17** The communication method according to claim 10 or 16, wherein the signaling information is included in a sub-field of the EML Control field of an EML Operation Mode (OM) Notification frame transmitted by the non-AP MLD. **Claim 18** In an access point multi-link device (AP MLD) configured to perform a frame exchange operation with at least one non-AP MLD operating in multi-link using an Uplink (UL) Traffic Identifier (TID)-To-Link mapping, - transmitting, to the non-AP MLD, a Buffer Status Report Poll (BSRP) trigger frame (TF) via a first active link; - receiving, from the non-AP MLD via the first active link, a BSR frame reporting buffered traffic; - scheduling UL resources for the non-AP MLD and transmitting, via the first active link, a basic TF including constraints on data to be transmitted within the scheduled UL resources based on the UL TID-Link mapping to the non-AP MLD; A communication method in a wireless network including the above. **Claim 19** The communication method according to claim 18, wherein the constraint on the data to be transmitted within the scheduled UL resources is indicated by a value of an access category (AC) corresponding to a UL TID mapped to the first active link according to the UL TID-To-Link mapping. **Claim 20** The communication method according to claim 19, wherein the value is indicated in a preferred AC sub-field of a Trigger Dependent User Info field of a User Info field corresponding to the scheduled UL resources in the basic TF. **Claim 21** The constraint on the data transmitted by the non-AP MLD is applicable when the UL TID-To-Link mapping is a negotiated UL TID-To-Link mapping with the value of the TID-To-Link Mapping Negotiation Supported subfield equal to 1, according to the communication method of claim 19.

22. The communication method according to claim 18, wherein at least one UL TID is mapped to the first active link on which the BSRP TF is transmitted according to the UL TID-Link mapping.

23. In at least one non-AP MLD operating on a multi-link using Uplink (UL) Traffic Identifier (TID)-To-Link mapping and an Access Point Multi-Link Device (AP MLD) configured to perform a frame exchange operation, Transmitting a Buffer Status Report Poll (BSRP) trigger frame (TF) to the non-AP MLD via a first active link to which at least one UL TID is mapped according to the UL TID-To-Link mapping. A communication method in a wireless network including the above.

24. In the AP MLD, the following two sub-modes of the EML mode - A first sub-mode of the EML mode including scheduling the UL resource for the non-AP MLD and transmitting the basic TF including the constraint based on the UL TID-To-Link mapping regarding the data to be transmitted within the scheduled UL resource. - A second sub-mode of the EML mode, wherein the AP MLD obtains an indication of a selected EML link to be used for frame exchange from the BSR frame and transmits a basic TF for triggering an uplink frame exchange with the non-AP MLD on the selected EML link to the non-AP MLD via the selected EML link. The communication method according to claim 18 or 23, further including transmitting signaling information indicating which of the above is used to the non-AP MLD.

25. In an access point multi-link device (AP MLD) configured to perform a frame exchange operation with at least one non-AP MLD operating in multi-link using an Uplink (UL) Traffic Identifier (TID)-To-Link mapping, - Receiving, via a first EML link of a set of EML links, from the non-AP MLD, a Buffer Status Report Poll (BSRP) frame in response to a BSRP trigger frame (TF) transmitted via the first EML link; - Obtaining, from the BSR frame, an indication of a selected EML link to be used for frame exchange among the EML links; - Transmitting, via the selected EML link, to the non-AP MLD, a basic TF for triggering an uplink frame exchange with the non-AP MLD on the selected EML link; A communication method in a wireless network, comprising.

26. The communication method according to claim 11 or 25, wherein the selected EML link is implicit with respect to one or more TIDs reported in the BSR frame when the UL TID-To-Link mapping is provided.

27. The communication method according to claim 11 or 25, wherein the reported one or more TIDs are mapped to a second EML link of the set of EML links and not mapped to the first EML link.

28. Under a negotiated TID-To-Link mapping with a TID-To-Link Mapping Negotiation Supported subfield value = 1, when the reported TIDs are mapped to the same EML link, the selected EML link to be used for frame exchange is the same EML link, the communication method according to claim 11 or 25.

29. Under the default TID-To-Mapping, or under the negotiated TID-To-Link Mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 2, the selected EML link to be used for frame exchange is the first EML link through which the BSRP trigger frame and the BSR frame are transmitted or received, according to the communication method of claim 11 or 25.

30. Under the negotiated TID-To-Link Mapping with the TID-To-Link Mapping Negotiation Supported subfield value = 1, when 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 through which the BSRP trigger frame and the BSR frame are transmitted or received, according to the communication method of claim 11 or 25.

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

32. The selected EML link is a second EML link in the set of EML links, different from the first EML link through which the BSRP trigger frame is transmitted and the BSR frame is received, according to the communication method of claim 25.

33. In the AP MLD, before transmitting a basic trigger frame that schedules UL resources to the non-AP MLD within a frame exchange sequence via a second EML link different from the first EML link through which the BSRP trigger frame is transmitted, further including transmitting an initial frame that triggers the frame exchange sequence on the second link, according to the communication method of claim 32.

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

35. The communication method according to any one of claims 14, 33, or 34, wherein the initial frame is a Multi User-Request to Send (MU-RTS) frame.

36. In the AP MLD, the following two sub-modes of the EML mode - The first sub-mode of the EML mode, including scheduling UL resources for the non-AP MLD and transmitting a basic TF including constraints regarding the data to be transmitted within the scheduled UL resources based on the UL TID-To-Link mapping. - The second sub-mode of the EML mode, in which the AP MLD obtains an indication of a selected EML link to be used for frame exchange from the BSR frame and transmits a basic TF for triggering an uplink frame exchange with the non-AP MLD at the selected EML link to the non-AP MLD via the selected EML link. The communication method according to claim 25, further including transmitting signaling information indicating which of the above is to be used to the non-AP MLD.

37. The communication method according to claim 24 or 36, wherein the signaling information is included in a sub-field of the Common Info field within the BSRP TF transmitted by the AP MLD or a sub-field of the User Info field assigned to the non-AP MLD.

38. A wireless communication device having at least one microprocessor configured to execute the communication method according to any one of claims 1, 11, 18, 23, or 25.

39. A non-transitory computer-readable medium storing a program that, when executed by a microprocessor or computer system within the wireless device, causes the wireless device to execute the communication method according to any one of claims 1, 11, 18, 23, or 25.

40. An access point (AP) belonging to an AP multi-link device (MLD), the AP operating on a link for exchanging frames with a non-AP station belonging to a non-AP MLD. - Transmitting, via the link, a basic trigger frame (TF) that schedules uplink (UL) resources to the non-AP station to which it belongs and includes a preferred AC sub-field in a Trigger Dependent User Info field of a User Info field corresponding to the scheduled UL resources within the basic TF. The preferred AC sub-field is set to a value of an AC whose at least one corresponding TID is mapped in UL to the link for the non-AP MLD by Traffic Identifier (TID)-To-Link mapping, a communication method in a wireless network. **Claim 41** The TID-To-Link Mapping is negotiated between the AP MLD and the non-AP MLD, the communication method according to claim 40. **Claim 42** - Transmitting, via the link, a Buffer Status Report Poll (BSRP) trigger frame (TF); - Receiving, via the link, a BSR frame reporting buffered traffic from the non-AP station to which it belongs; The communication method according to claim 40, further comprising. **Claim 43** An access point (AP) belonging to an AP multi-link device (MLD) adapted to operate on a link of a wireless network to exchange frames with a non-AP station belonging to a non-AP MLD, the belonging AP having - A transmitter configured to transmit, via the link, a basic trigger frame (TF) that schedules uplink (UL) resources to the non-AP station to which it belongs and includes a preferred AC sub-field in a Trigger Dependent User Info field of a User Info field corresponding to the scheduled UL resources within the basic TF. The preferred AC subfield is set to a value of the AC for which at least one corresponding TID is mapped in UL to the link for the non-AP MLD by Traffic Identifier (TID)-to-Link mapping, at an access point.

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