Extended NSTR indication bitmaps in case of channel switching mechanisms such as DSO, NPCA or dbe

Abstract

A non-AP MLD computes an NSTR status of its NSTR Indication Bitmaps by comparing a frequency difference between the nearest frequency edges of the operating channels of the two affiliated APs of the concerned links with a minimum frequency gap value specific to the non-AP MLD or between the nearest frequency edge of the channels comprising the initial operating and substitute channels of one affiliated non-AP STA to the frequency edge of the other link with the minimum frequency gap value. The substitute channel is the channel to which the affiliated non-AP STA switches in case a channel switching mechanism such as DSO or NPCA or DBE is activated by the AP MLD. Rather than only encompassing the initial operating channels of the affiliated non-AP STAs, the extended NSTR Indication Bitmaps encompass any substitute channel to which the affiliated non-AP STAs are liable to switch. All NSTR constraints can therefore be taken into account.

Description

[0001] EXTENDED NSTR INDICATION BITMAPS IN CASE OF CHANNEL SWITCHING MECHANISMS SUCH AS DSO, NPCA OR DBE

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to wireless communications and more specifically to Multi-Link (ML) communications.

[0004] BACKGROUND OF THE INVENTION

[0005] Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.

[0006] The 802.11 family of standards adopted by the Institute of Electrical and Electronics Engineers (IEEE - RTM) provides a great number of mechanisms for wireless communications between STAs.

[0007] The 802.11 be or EHT for “Extremely High Throughput” standard (current release Draft P802.11 be / D7.0) introduces the Multi-Link (ML) Operation (MLO). MLO improves data throughput by allowing communications between STAs (stations) over multiple concurrent and noncontiguous communication links.

[0008] A STR (“Simultaneous Transmit and Receive”) or NSTR (non-STR) status is defined per pair of links. A NSTR link pair is a pair of links corresponding to stations (STAs) affiliated with a multi-link device (MLD), usually a non-AP MLD, for which receiver requirements (e.g., as specified in 36.3.21 of P802.11 be / D7.0) to avoid channel / link interference are not met on one of the links when a STA affiliated with the MLD is transmitting on the other link. A STR link pair is a pair of links that is not a NSTR link pair. Therefore, a non-AP MLD does not support or is unable or not allowed to simultaneously transmit and receive over the links of a NSTR link pair.

[0009] The NSTR status for a link pair is conventionally evaluated from the operating channels of the affiliated non-AP STAs corresponding to the links, i.e., the channels agreed on with the AP MLDs upon associating. The NSTR statuses are shared between the non-AP MLD and the AP MLD using so-called NSTR Indication Bitmaps.

[0010] Some communication mechanisms or features have been introduced at single-link STAs to increase network efficiency, wherein the STA switches its operating channel to a substitute channel.

[0011] For example, the HE SST (High Efficiency Subchannel Selective Transmission) mechanism, introduced in IEEE 802.11 ax, allows an 80MHz non-AP STA to operate on the secondary 80MHz channel (hence “substitute channel”) of a 160MHz AP’s operating bandwidth or a 20MHz non-AP STA to operate outside the primary 20MHz channel of a wider AP’s operating bandwidth. In HE SST, the substitute channel does not overlap the initial operating channel.

[0012] The Dynamic Subband Operation (DSO) mechanism, proposed by the IEEE 802.11 bn Task Group, allows, typically, a 320MHz operating bandwidth AP to dynamically indicate to a 160MHz bandwidth non-AP STA that it will be served within a next TXOP on its secondary part (channel) of the 320MHz operating channel (hence “substitute channel”). More generally, the DSO mechanism applies to any AP / non-AP STA operating bandwidth combination where the AP’s operating channel is larger than the non-AP STA’s operating channel. In DSO, the substitute channel does not overlap the initial operating channel.

[0013] The Non-Primary Channel Access (NCPA) mechanism, proposed by the IEEE 802.1 1 bn Task Group, allows an AP and an associated non-AP STA(s), upon detection of a busy primary channel by an Overlapping Basic Service Set (OBSS), to switch to a non-primary / secondary channel (e.g. called anchor channel - hence “substitute channel”) to initiate a data transmission in their own Basic Service Set (BSS) for a TXOP duration corresponding to the basic Network Allocation Vector (NAV) value set based on the detected OBSS interference. In NPCA, the substitute channel does not overlap the initial operating channel.

[0014] The Dynamic Bandwidth Expansion (DBE) mechanism, proposed by the IEEE 802.1 1 bn Task Group, allows an AP to dynamically expand its operating bandwidth / channel to be greater than the basic service set (BSS) bandwidth / channel, for associated ultra-high reliability (UHR) non-AP STAs that support DBE mode. The operating bandwidth / channel of the AP for DBE operation when DBE mode is enabled by the AP is called the DBE bandwidth / channel. The DBE bandwidth / channel is greater than the BSS bandwidth / channel of the AP. The DBE operating channel and the BSS operating channel use the same primary channel. During DBE operation, a non-AP STA performs data frames exchanges with the AP over the expanded DBE channel (hence “substitute channel”). In DBE, the substitute channel overlaps (in particular, includes) the BSS operating channel.

[0015] These mechanisms may be applied on any link of the above MLDs. Due to the changing from the operating channel to the substitute channel on a target link, the NSTR statuses as initially shared between the non-AP MLD and the AP MLD are no longer mirroring the risks of channel / link interference in an MLD. This deteriorates network efficiency.

[0016] SUMMARY OF INVENTION

[0017] It is a broad objective of the present disclosure to overcome some of the foregoing concerns.

[0018] Methods are sought for an AP MLD and / or for a non-AP MLD subject to NSTR constraints to guarantee efficient Multi-Link Operation (MLO) between them when cooperating with mechanisms requiring a switch of operating channel such as the above DSO, NPCA, DBE, HE SST mechanisms. The methods proposed below advantageously allow DSO / NPCA / DBE TXOPs (or HE SST TWT SPs - service periods) to be managed independently on several links that are setup between the AP MLD and the non-AP MLD.

[0019] A first approach of the present disclosure proposes a method in a non-Access Point (non- AP) Multi-Link Device (MLD), comprising: determining a Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup with two respective APs affiliated with an AP MLD, the determining being based on frequency edges of operating channels (or frequency bands) of the two affiliated APs. The operating channel of an affiliated AP may correspond to the BSS operating channel or to the DBE operating channel of that affiliated AP. It is the channel announced by the AP for its BSS (the DBE-compatible STAs for the DBE operating channel), e.g., through beacon frames or probe / association response frames or the like, independently to the links that may be setup with the STAs of the BSS within that channel.

[0020] A second approach of the present disclosure proposes a method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: determining a Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup between two respective non-AP stations (STAs) affiliated with the non-AP MLD and two respective APs affiliated with an AP MLD, the determining being based on a frequency edge of channels comprising an operating channel of a first one of the affiliated non-AP STAs that corresponds to a first link of the link pair and a substitute channel of the first affiliated non-AP STA, and a frequency edge of the other link of the link pair (hence corresponding to the other affiliated non-AP STA). The frequency edge of the other link may be an edge of the set made of the operating channel and the substitute channel, if any, of the other affiliated non-AP STA (corresponding to this other link).

[0021] By substitute channel it may be meant a channel that is distinct from the operating channel without overlapping, e.g., with the DSO, NPCA and HE SST mechanism. With the DBE mechanism, the substitute channel overlaps (in particular entirely includes) the operating channel. A substitute channel may define a channel on which the first affiliated non-AP STA operates in a case where a communication mechanism (e.g., DSO or NPCA or DBE or HE SST) requiring switching from the operating channel of the first affiliated non-AP STA to the substitute channel is activated.

[0022] Rather that determining the NSTR status of the link pairs based on the edges of the non- AP STA’s operating channels, the approaches above base the determination on new frequency edges, namely those of the AP’s operating channels and / or those of the maximum potential usable channel of the non-AP stations, i.e., taking into account the substitute channel itself by considering the set of channels made of the STA’s operating channel and substitute channel.

[0023] The choice of these new frequency edges ensures the substitute channel to which the non-AP STA may be required to switch - hence channel for DSO or NPCA or DBE or HE SST operations - to be encompassed or included in the NSTR declaration, from the very beginning. It results that there is no longer NSTR discrepancy when any of the mechanisms requiring channel switching (below “channel switching mechanisms”) is activated. No interference will occur. Better MLO can therefore be achieved.

[0024] Optional features are defined below with reference to methods, while they can be transposed into device features.

[0025] In some embodiments regarding the first approach, the NSTR status of the link pair is based on the nearest frequency edges of the operating channels of the two affiliated APs.

[0026] In particular embodiments, the NSTR status of the link pair is obtained by comparing a frequency difference between the nearest frequency edges of the operating channels of the two affiliated APs with a minimum frequency gap (or separation) value specific to the non-AP MLD.

[0027] In embodiments, at least one operating channel of the two affiliated APs is an expended operating channel resulting from a Dynamic Bandwidth Expansion (DBE) mechanism, compared to a Basic Service Set (BSS) operating channel implemented by the affiliated AP in absence of DBE mechanism. Alternatively, the conventional BSS operating channel can be taken into account.

[0028] In some embodiments regarding the second approach, the NSTR status of the link pair is based on the nearest frequency edge of the channels comprising the operating and substitute channels of the first affiliated non-AP STA to the frequency edge of the other link. Of course, the frequency edge of the other link may be determined in the same way (nearest edge to the first link); hence, the NSTR status of a link pair may even be determined based on edges of the two substitute channels applicable to the two links of the pair.

[0029] In particular embodiments, the NSTR status of the link pair is obtained by comparing a frequency difference between the nearest frequency edge of the channels comprising the operating and substitute channels of the first affiliated non-AP STA, and the frequency edge of the other link with a minimum frequency gap value specific to the non-AP MLD.

[0030] It is meant by “nearest edge” the edge from amongst the edges of all the channels considered that is the closest (the lowest frequency distance) to a target edge or channel. Also, the (frequency) edges of a channel are meant as the ends of the frequency band forming the channel.

[0031] In some embodiments, the non-AP MLD obtains the operating channels of the affiliated APs from the AP MLD. They may be advertised through broadcast Beacon frames.

[0032] In other embodiments, the non-AP MLD reports (i.e., shares) the NSTR status of the link pair to the AP MLD. In yet other embodiments, the non-AP MLD reports statuses of a plurality of link pairs (e.g. all combinations of links setup with the AP MLD) to the AP MLD. Each status may be determined as defined above, based on either determining approach. The reporting may include one or more NSTR Indication Bitmaps to signal the NSTR status of all (or part) link pairs given the multiple setup links. For example, one or more NSTR Indication Bitmaps may be included in Per-STA Profile subelements of a Basic Multi-Link element in an exchanged frame. In some embodiments regarding the first approach, the method includes reporting the NSTR status during association or re-association of the non-AP MLD with the AP MLD.

[0033] In some embodiments regarding the second approach, the non-AP MLD obtains the substitute channel from the AP MLD and reports the NSTR status of the link pair to the AP MLD, wherein the obtaining and the reporting take place during association or re-association of the non- AP MLD with the AP MLD.

[0034] By reporting the new NSTR statuses as early as the association - e.g., in an Association Request frame from the non-AP STA -, the use of the DSO, NPCA, DBE, HE SST or the like operations can take place without additional signalling frame and without risks of interference between channels simultaneously used by the non-AP STA (i.e. , risks that a STR pair becomes NSTR during operations).

[0035] In some embodiments regarding either approach, the method includes reporting the NSTR status of the link pair upon the AP MLD activating a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism on one link of the link pair at the non-AP MLD. This activation of such mechanism (or “feature”) may be done by a mere triggering / signalling frame sent by the AP MLD. All the above mechanisms rely on the temporary use of a subpart (referred to as substitute channel) of the operating channel of an affiliated AP, that does not match the initial operating channel of the corresponding (associated) affiliated non-AP STA, and which may even not overlap or include the initial operating channel. Hence, the affiliated non-AP STA has to temporarily switch its operating channel to the substitute channel. The substitute channel may be obtained during association or re-association of the non-AP MLD with the AP MLD.

[0036] In corresponding embodiments, upon the AP MLD deactivating the DSO or NPCA or DBE or HE SST mechanism, the non-AP MLD reports to the AP MLD a NSTR status of the link pair (or of all link pairs) that is based on frequency edges of only operating channels of non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair. This defines a switch back to conventional / legacy NSTR statuses when a channel switching mechanism ends.

[0037] To avoid exchanging NSTR information each time one of the above mechanisms is activated or deactivated, sets of NSTR statuses (e.g., bitmaps) may be defined in advance between the AP MLD and the non-AP STA (e.g., during association). Next, the AP MLD and the non-AP STA may switch between the sets upon activating or deactivating a channel switching mechanism. In this respect, the disclosure proposes a method in a first Multi-Link Device (MLD), comprising: obtaining two sets of Non-Simultaneous Transmit Receive (NSTR) Indication statuses of a pair of links setup between the first MLD and a second MLD - the first MLD may be an AP MLD and the second MLD a non-AP MLD, or the reverse; switching from a first one of the sets to the other set upon a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism being activated (by one of the MLDs, usually the AP MLD) on one of the links setup between the first and second MLDs.

[0038] One set may be computed in a conventional manner, while the other one is computed using any enhanced method as described above to take into account the substitute channel or channels. The MLDs therefore dynamically adjust the NSTR indication between them as the channel use evolves (initial operating channel or substitute one). This avoids any NSTR discrepancy and better MLO can be achieved.

[0039] In some embodiments, the first MLD switches back to the first set upon the DSO or NPCA or DBE or HE SST mechanism being deactivated.

[0040] A third approach of the present disclosure proposes a method in an Access Point (AP) Multi-Link Device (MLD), comprising: receiving, from one or more non-AP MLDs, a minimum frequency gap value for Simultaneous Transmit Receive (STR) operation, selecting, based on the minimum frequency gap value or values received, a non-AP MLD and / or substitute channel parameters to trigger a communication mechanism (e.g., DSO or NPCA or DBE or HE SST) at the non-AP MLD, the communication mechanism requiring switching of a station affiliated with the non-AP MLD from an operating channel to a substitute channel.

[0041] The third approach allows the AP MLD to dynamically manage the DSO or NPCA or DBE or HE SST mechanisms at the non-AP MLDs in an efficient way, in particular to avoid risks that a STR link pair becomes a NSTR link pair through the activation of such mechanism. This is achieved by selecting appropriate non-AP MLDs and parameters based on the minimum frequency gap for STR operation each non-AP MLD can guarantee.

[0042] For example, the AP MLD may choose non-AP MLDs having sufficient minimum frequency gaps for STR operation, given current non-AP MLDs’ operating channels and the substitute channel the AP MLD intends to use.

[0043] The AP MLD may also design a substitute channel (by setting parameters such as the frequency position of the substitute channel, its bandwidth, MCS, and so on.) for a given STA affiliated with a non-AP MLD given its respective minimum frequency gap for STR operation.

[0044] A fourth approach of the present disclosure proposes a method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: sharing, with an AP MLD, a Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup with the AP MLD. Optionally, statuses of pairs can be shared. An NSTR status of a link pair may be based on frequency edges of only operating channels of non-AP STAs affiliated with the non-AP MLD that correspond to the links of the link pair; upon the AP MLD activating or enabling a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism on a link of the link pair, updating the shared NSTR status. In particular, at least one updated NSTR status may be determined based on a frequency edge different from a frequency edge of the operating channels of the affiliated non-AP STAs.

[0045] Furthermore, the updated NSTR status may be shared with the AP MLD.

[0046] Correspondingly, it is proposed a method in an Access Point (non-AP) Multi-Link Device (MLD), comprising: receiving, from at least one non-AP MLD, a Non-Simultaneous Transmit Receive (NSTR) statuses of a pair of links setup between the AP MLD and the non-AP MLD; activating or enabling a Dynamic Subband Operation (DSO) mechanism or a NonPrimary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism on a link of the link pair at the non-AP MLD; responsive to the activation / enablement, receiving an updated NSTR status from the non- AP MLD. The updated NSTR status may be determined based on a frequency edge different from a frequency edge of the operating channels of the affiliated non-AP STAs.

[0047] The DSO or NPCA or DBE or HE SST mechanism is enabled or activated for a specific link setup between the two MLDs, which link has its operating channel that is switched to a substitute channel.

[0048] In embodiments, a DSO TXOP is activated at an affiliated non-AP station following the sending by an affiliated AP of an initial control frame.

[0049] In embodiments, a NPCA TXOP is activated at an affiliated AP and at an affiliated non- AP station after detection of an OBSS on the primary channel.

[0050] In embodiments, DBE may be enabled by an affiliated non-AP station before enablement of the DBE at the affiliated AP.

[0051] The details above of the first and second approach may apply to the updating of the shared NSTR statuses.

[0052] In embodiments, the updated NSTR status of a link pair is determined based on a frequency edge of an operating channel of an affiliated AP of the AP MLD corresponding to the link on which the DSO or NPCA or DBE or HE SST mechanism is enabled or activated. The operating channel of an affiliated AP may correspond to the BSS operating channel or to the DBE operating channel of that affiliated AP.

[0053] In embodiments, the updated NSTR status of a link pair may be determined by comparing a frequency difference between the nearest frequency edges of operating channels of two affiliated APs of the AP MLD corresponding to the links of the link pair with a minimum frequency gap value specific to the non-AP MLD.

[0054] In other embodiments, the updated NSTR status of a link pair is determined based on a frequency edge of a substitute channel to operate DSO or NPCA or DBE or HE SST on the link on which the DSO or NPCA or DBE or HE SST mechanism is enabled or activated. The DSO or NPCA (in case it is enabled / activated) may be operated in an expended operating channel resulting from a Dynamic Bandwidth Expansion (DBE) mechanism enabled by the AP MLD. Alternatively, if no DBE mechanism has been previously enabled / activated, the DSO or NPCA is performed on the conventional BSS operating channel.

[0055] In other embodiments, the updated NSTR status of a link pair may be determined by comparing a frequency difference with a minimum frequency gap value specific to the non-AP MLD, the frequency difference being calculated between the nearest frequency edge of channels comprising an operating channel of an affiliated non-AP STA of the non-AP STA that corresponds to the link on which the DSO or NPCA or DBE or HE SST mechanism is enabled or activated and a substitute channel of the affiliated non-AP STA to operate DSO or NPCA or DBE or HE SST on that link, to a frequency edge of the other link of the link pair.

[0056] In other embodiments, the updated NSTR status of a link pair may be determined by comparing a frequency difference with a minimum frequency gap value specific to the non-AP MLD, the frequency difference being calculated between the nearest frequency edge of a substitute channel of an affiliated non-AP STA of the non-AP STA to operate DSO or NPCA or DBE or HE SST on one of the links to a frequency edge of the other link.

[0057] In some embodiments, the updated NSTR status is an NSTR status for a link pair that includes the link on which the DSO or NPCA or DBE or HE SST mechanism is enabled or activated. The update may be limited to only the link pairs affected by the DSO or NPCA or DBE or HE SST mechanism enabling or activation. Or all the NSTR statuses may be updated (e.g., taking into account the DSO or NPCA or DBE or HE SST mechanisms that are possibly enabled / activated on the respective links, although they are not yet enabled / activated).

[0058] In other embodiments, the non-AP MLD, responsive to receiving, from the AP MLD, a frame to enable or activate the DSO or NPCA or DBE or HE SST mechanism, sends to the AP MLD a frame to acknowledge the enabling or activation, wherein the frame to acknowledge includes a signalling that an update of the shared NSTR statuses by the non-AP STA is needed. A subsequent (hence separate) frame conveying the updated NSTR statuses can be transmitted thereafter.

[0059] In some embodiments, the non-AP MLD receives, from the AP MLD, a frame to enable or activate the DSO or NPCA or DBE or HE SST mechanism, wherein the frame to enable or activate includes time information about when the updated NSTR statuses enter into force. In some embodiments, the time information is a number of Target Beacon Transmission Times (TBTT).

[0060] In some embodiments, upon the AP MLD disabling or deactivating the DSO or NPCA or DBE or HE SST mechanism at the non-AP MLD, the non-AP MLD updates back the shared NSTR statuses based on the frequency edges of only the operating channels of the affiliated non-AP STAs.

[0061] In some embodiments, the non-AP MLD, responsive to receiving, from the AP MLD, a frame to disable or deactivate the DSO or NPCA or DBE or HE SST mechanism, sends to the AP MLD a frame to acknowledge the disabling or deactivation, wherein the frame to acknowledge includes a signalling that an update of the shared NSTR statuses by the non-AP STA is needed. A subsequent (hence separate) frame conveying the updated NSTR statuses can then be transmitted thereafter.

[0062] In some embodiments, the non-AP MLD receives, from the AP MLD, a frame to disable or deactivate the DSO or NPCA or DBE or HE SST mechanism, wherein the frame to disable or deactivate includes time information about when the NSTR statuses updated back enter into force. In some embodiments, the time information is a number of Target Beacon Transmission Times (TBTT).

[0063] In some embodiments, sharing the NSTR statuses takes place during association or reassociation of the non-AP MLD with the AP MLD.

[0064] In further embodiments, an NSTR status of a link pair is based on frequency edges of only operating channels of non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair.

[0065] In some embodiments, at least one updated NSTR status is determined based on a frequency edge different from a frequency edge of the operating channels of the affiliated non- AP STAs.

[0066] In embodiments, the updated NSTR status are exchanged in a frame carrying a Reconfiguration Multi-Link (ML) element. In some embodiments, the frame carrying the Reconfiguration ML element is an UHR Link Reconfiguration frame or a MLO Update Request frame.

[0067] A fifth approach of the present disclosure proposes a method in a non-Access Point (non- AP) Multi-Link Device (MLD), comprising activating a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism over an operating channel of the non-AP MLD, wherein the operating channel is an expended operating channel resulting from a Dynamic Bandwidth Expansion (DBE) mechanism.

[0068] A sixth approach of the present disclosure proposes a method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: sharing, with an AP MLD, at least one Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup with the AP MLD, wherein an NSTR status of a link pair is based on frequency edges of only operating channels of non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair; upon receiving from the AP MLD a frame to activate a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism at the non-AP MLD, deciding to accept or refuse the activation based on whether the activation of the DSO or NPCA or DBE or HE SST mechanism modifies or not at least one NSTR status of the link pair, and sending to the AP MLD a frame to report the decision.

[0069] A seventh approach of the present disclosure proposes a method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: sending, to an AP MLD, a Multi-Link Operation Update Request frame including a Reconfiguration Multi-Link element to report a change of Non-Simultaneous Transmit Receive (NSTR) statuses of pairs of links setup with the AP MLD, wherein to report that all link pairs are STR, an NSTR Indication Bitmap Present subfield in a STA Control field of a Per-STA Profile subelement of a Link Info field of the Reconfiguration Multi-Link element is set to 0, or the NSTR Indication Bitmap Present subfield is set to 1 and an NSTR Indication Bitmap in a STA Info field of a Per-STA Profile subelement of the Link Info field of the Reconfiguration Multi-Link element is set to all Os.

[0070] In embodiments, setting the NSTR Indication Bitmap is set to all Os to report that all link pairs are STR is conditional to a Reconfiguration Operation Type subfield in the STA Control field may be set to 4.

[0071] A corresponding method may regard the AP MLD side that receives such frame.

[0072] Thanks to this signalling not currently authorized in P802.11 be / D7.0, a non-AP MLD becomes able to report a NSTR-to-allSTR change to its AP MLD.

[0073] Correlatively, the invention also provides a wireless communication device comprising at least one microprocessor configured for carrying out any method as described above.

[0074] Another aspect of the invention relates to a non-transitory computer-readable medium storing a program which, when executed by a microprocessor or computer system in a wireless device, causes the wireless device to perform any method as described above.

[0075] At least parts of the methods according to the invention may be computer implemented. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit", "module" or "system". Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer usable program code embodied in the medium.

[0076] Since the present invention can be implemented in software, the present invention can be embodied as computer readable code for provision to a programmable apparatus on any suitable carrier medium. A tangible, non-transitory carrier medium may comprise a storage medium such as a floppy disk, a CD-ROM, a hard disk drive, a magnetic tape device or a solid- state memory device and the like. A transient carrier medium may include a signal such as an electrical signal, an electronic signal, an optical signal, an acoustic signal, a magnetic signal or an electromagnetic signal, e.g. a microwave or RF signal.

[0077] BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Embodiments of the invention will now be described, by way of example only, and with reference to the following drawings in which:

[0079] Figure 1 illustrates a typical 802.11 network environment involving ML transmissions between MLDs in which the present invention may be implemented; Figure 2 schematically illustrates a frequency view of links setup between an AP MLD and a non-AP MLD for the legacy computation of the NSTR status of a link pair.

[0080] Figures 3a and 3c schematically illustrates frequency views of links setup between an AP MLD and a non-AP MLD for the computation of a new NSTR status of a link pair according to embodiments.

[0081] Figures 3b and 3d schematically illustrates frequency views of links setup between an AP MLD and a non-AP MLD for the computation of a new NSTR status of a link pair according to other embodiments.

[0082] Figures 4a illustrates an exemplary format of the UHR Capabilities subfield in the Common Info field of a Basic Multi-Link element according to embodiments.

[0083] Figures 4b illustrates an exemplary format of the DSO / NPCA / DBE Configuration element in a Per STA Profile subelement of Link Info field according to embodiments.

[0084] Figure 4c illustrates the format of the MLD Capabilities And Operations subfield in the Common Info field of a Basic Multi-Link element as defined in P802.11 be / D7.0.

[0085] Figure 4d illustrates the format of a Per-STA Profile according to P802.11 be / D7.0.

[0086] Figure 5 illustrates, using a flowchart, steps at an AP MLD to apply for the usage of the channel switching mechanisms considering NSTR constraints of the non-AP MLDs, according to embodiments.

[0087] Figure 6 illustrates a frame exchange sequence between an AP MLD and a non-AP MLD according to embodiments.

[0088] Figure 7 illustrates, using a flowchart, corresponding steps performed by the AP MLD involved in Figure 6, according to embodiments.

[0089] Figure 8 illustrates, using a flowchart, corresponding steps performed by the non-AP MLD involved in Figure 6, according to embodiments.

[0090] Figure 9a illustrates an exemplary Action field format of the DSO / NPCA Operating Mode notification frame according to embodiments.

[0091] Figure 9b illustrates an exemplary format for the DSO / NPCA Operating Mode Control field of Figure 9a, according to embodiments.

[0092] Figure 10 shows a schematic representation of a wireless communication device in accordance with embodiments.

[0093] DETAILED DESCRIPTION OF EMBODIMENTS

[0094] A non-AP MLD computes an NSTR status of its NSTR Indication Bitmaps by comparing a frequency difference between the nearest frequency edges of the operating channels of the two affiliated APs of the concerned links with a minimum frequency gap value specific to the non-AP MLD or between the nearest frequency edge of the channels comprising the initial operating and substitute channels of one affiliated non-AP STA to the frequency edge of the other link with the minimum frequency gap value. The substitute channel is the channel to which the affiliated non- AP STA switches in case a channel switching mechanism such as DSO or NPCA or DBE is activated by the AP MLD. Rather than only encompassing the initial operating channels of the affiliated non-AP STAs, the extended NSTR Indication Bitmaps encompass any substitute channel to which the affiliated non-AP STAs are liable to switch. All NSTR constraints can therefore be taken into account.

[0095] The extended NSTR Indication Bitmaps may be provided upon associating with the AP MLD. In variants, the legacy NSTR Indication Bitmaps may be provided upon associating with the AP MLD, in which case the extended NSTR Indication Bitmaps may be provided responsive to any channel switching mechanism activation by the AP MLD. Correspondingly, the legacy NSTR Indication Bitmaps may be restored upon deactivating the channel switching mechanism.

[0096] In the present disclosure, “Channel” refers to a specific frequency range within a spectrum or band, i.e., a bandwidth plus a position within the spectrum or band. “Bandwidth” therefore refers to the width of a frequency range. “Bandwidth” may be used instead of “Channel” when the position is implicit.

[0097] The techniques described herein may be used for various broadband wireless communication systems, including communication systems that are based on an orthogonal multiplexing scheme. Examples of such communication systems include Spatial Division Multiple Access (SDMA) system, Time Division Multiple Access (TDMA) system, Orthogonal Frequency Division Multiple Access (OFDMA) system, and Single-Carrier Frequency Division Multiple Access (SC-FDMA) system. A SDMA system may utilize sufficiently different directions to simultaneously transmit data belonging to multiple user terminals, i.e. wireless devices or STAs. A TDMA system may allow multiple user terminals to share the same frequency channel by dividing the transmission signal into different time slots or resource units, each time slot being assigned to different user terminal. An OFDMA system utilizes orthogonal frequency division multiplexing (OFDM), which is a modulation technique that partitions the overall system bandwidth into multiple orthogonal sub-carriers or resource units. These sub-carriers may also be called tones, bins, etc. With OFDM, each sub-carrier may be independently modulated with data. A SC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit on sub-carriers that are distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on a block of adjacent sub-carriers, or enhanced FDMA (EFDMA) to transmit on multiple blocks of adjacent sub-carriers.

[0098] The teachings herein may be incorporated into (e.g., implemented within or performed by) a variety of apparatuses (e.g., STAs). In some aspects, a wireless device or STA implemented in accordance with the teachings herein may comprise an access point (so-called AP) or non access point (so-called non-AP STA or STA).

[0099] While the examples are described in the context of WiFi (RTM) networks, the invention may be used in any type of wireless networks like, for example, mobile phone cellular networks that implement very similar mechanisms.

[0100] An AP may comprise, be implemented as, or known as a Node B, Radio Network Controller (“RNC”), evolved Node B (eNB), 5G Next generation base STA (gNB), Base STA Controller (“BSC”), Base Transceiver STA (“BTS”), Base STA (“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver, Basic Service Set (“BSS”), Extended Service Set (“ESS”), Radio Base STA (“RBS”), or some other terminology.

[0101] A non-AP STA may comprise, be implemented as, or known as a subscriber STA, a subscriber unit, a mobile STA (MS), a remote STA, a remote terminal, a user terminal (UT), a user agent, a user device, user equipment (UE), a user STA, or some other terminology. In some implementations, a STA may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (“SIP”) phone, a wireless local loop (“WLL”) STA, a personal digital assistant (“PDA”), a handheld device having wireless connection capability, or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or smart phone), a computer (e.g., a laptop), a tablet, a portable communication device, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a global positioning system (GPS) device, or any other suitable device that is configured to communicate via a wireless or wired medium. In some aspects, the non-AP STA may be a wireless node. Such wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link.

[0102] An AP manages a set of STAs (registered to it or associated with it) that together organize their accesses to the wireless medium for communication purposes. The STAs (including the AP to which they register) form a service set, here below referred to as basic service set, BSS (although other terminology can be used). A same physical STA acting as an access point may manage two or more BSS (and thus corresponding WLANs): each BSS is thus uniquely identified by a specific basic service set identification, BSSID and managed by a separate virtual AP implemented in the physical AP. Each STA is identified within a BSS thanks to an identifier, AID, assigned to it by the AP upon registration.

[0103] The 802.11 family of standards define various media access control (MAC) mechanisms to drive access to the wireless medium.

[0104] In any frame or element format disclosed herewith, fields may be named, for the sake of convenience, in relation to or corresponding to a specific IEEE802.1 1 standard, such using the letters “UHR” in relation to or corresponding to the IEEE802.11 bn standard. However, a different name may be used. Also, a field related to or corresponding to a specific standard may be comprised of a plurality of fields. For example, a given field may be comprised of two fields, such as A field and B field or may be comprised of equal to or more than three fields.

[0105] Also, the arrangement of the fields in a frame or element format is not limited to the example shown in and described with reference to the proposed examples, and the fields may be arranged in a different order. Also, the format does not need to include all the fields shown in and described with reference to the proposed examples, and the format may include a part of the fields shown in and described with reference to the proposed examples. Also, the format may include a field which is different from the fields shown in and described with reference to the proposed examples.

[0106] The standard 802.11 be introduced the Multi-Link Operation (MLO) when it comes to MAC layer operation. The MLO allows multi-link devices to establish or setup multiple links and operate them simultaneously.

[0107] A Multi-Link Device (MLD) is a logical entity and has more than one affiliated STA (STA) and has a single medium access control (MAC) service access point (SAP) to logical link control (LLC), which includes one MAC data service. An Access Point Multi-Link Device (or AP MLD) then corresponds to an MLD where each STA affiliated with the MLD is an AP, hence referred to as “affiliated AP”. A non-Access Point Multi-Link Device (or non-AP MLD) corresponds to an MLD where each STA affiliated with the MLD is a non-AP STA, referred to as “affiliated non-AP STA”. Multiple affiliated non-AP STAs of a non-AP MLD can then setup communication links with multiple affiliated APs of an AP MLD, hence forming a multi-link channel.

[0108] From architecture point of view, an MLD contains typically several radios in order to implement its affiliated STAs but not necessary a number equal to its number of affiliated STAs. In particular, a non-AP MLD may operate with a number of affiliated STAs greater than its number of radios (which can even be reduced to a single one).

[0109] A communication link or “link” thus corresponds to a given channel and bandwidth (e.g. ch.36, ch.40, ch.38, ...) in a given frequency band (e.g., 2.4 GHz, 5 GHz, 6 GHz) between an AP affiliated with the AP MLD and a non-AP STA affiliated with the non-AP MLD. The maximum operating bandwidth at station level has evolved continuously through the releases of the successive 802.11 amendments. The release 802.11 be extends the maximum operating bandwidth of a WLAN to 320MHz, future releases may extend it even higher. This leads to possible operating bandwidths of 20, 40, 80, 160 or 320MHz. An operating bandwidth of 20, 40, 80, 160 or 320MHz (or even more in the future) is usually made of a primary channel and one or more secondary channels (each channel being 20MHz or a multiple thereof) as agreed between the AP and the non-AP STA (possibly via their MLDs) when associating. The primary channel is especially used for Beacon signalling, for EDCA channel access procedure (i.e. Enhanced Distributed Channel Access - EDCA) for backwards compatibility while the secondary channels are mainly used for sending data at high throughput. The secondary channels are not used neither for Beacon signalling, nor for EDCA channel access procedure.

[0110] An AP affiliated with an AP MLD is uniquely identified with a link ID that is an integer value between 0 and 14. At any given time, no two affiliated APs of the same AP MLD have the same link ID. The link ID associated with an affiliated AP does not change for the lifetime of the BSS set up by that AP. AP MLD may assign the link ID to its affiliated APs by incrementing the IDs from 0 (from the first affiliated AP).

[0111] Multiple affiliated non-AP STAs of a non-AP MLD can then setup communication links with multiple affiliated APs of an AP MLD, hence forming a multi-link channel. The links setup during association procedure are called “setup links”. A setup link becomes an “enabled Link” once at least one Traffic I Dentifier (TID) is mapped to this link.

[0112] The affiliated APs and non-AP STAs operate on their respective links in accordance with one or more of the IEEE 802.11 standards (a / b / g / n / ac / ad / af / ah / aj / ay / ax / be / bn) or other wireless communication standards.

[0113] Depending on the capabilities of the non-AP MLD or affiliated non-AP STAs compared to those of the AP MLD, a given affiliated non-AP STA may agree on (with the AP) and operate only within a sub-band of the AP’s operating bandwidth. The term “link” defines both the sub-band from affiliated non-AP STA perspective and the entire AP’s operating bandwidth from AP perspective.

[0114] The links established (or “enabled links”) for MLDs are theoretically independent, meaning that the channel access procedure (to the communication medium) and the communication are performed independently on each link. Hence, different links may have different data rates (e.g. due to different bandwidths, number of antennas, etc.) and may be used to communicate different types of information (each over a specific link).

[0115] However, some interference between links may exist, usually depending on their channels. A STR (simultaneous transmit and receive) or NSTR (non-STR) status has been defined per link pair. A NSTR link pair is a pair of links corresponding to stations (STAs) affiliated with a multi-link device (MLD) for which receiver requirements (as specified in 36.3.21 of P802.11 be / D7.0) to avoid channel / link interference are not met on one of the links when a STA affiliated with the MLD is transmitting on the other link. A STR link pair is a pair of links that is not a NSTR link pair. NSTR status and STR status are synonymous: they indicate whether the link pair is NSTR or STR.

[0116] The links belonging to a STR link pair can effectively be considered as independent, contrary to the links belonging to a NSTR link pair.

[0117] Indeed, with the introduction of MLO involving MLDs, some new constraints have appeared, such as the NSTR constraint. On an MLD, this constraint is related to interferences between each couple / pair of affiliated STAs when the transmission of a first affiliated STA on a first link causes interferences on the receive chain of a second affiliated STA operating on a second link. Such interferences result from closeness of the operating channels of the links, and prohibit a correct reception operation for the second affiliated STA on the second link.

[0118] The NSTR constraint affects multi-link communications between an AP MLD and a non- AP MLD as follows: the simultaneous transmission on the first link and reception on the second link are not possible for an MLD subject to NSTR constraint between the corresponding couple / pair of affiliated STAs. The constraint applies to opposed transmission directions over the two links. However, the simultaneous transmissions (or receptions) on the first and second links are possible for an MLD subject to NSTR constraint between the corresponding couple / pair of affiliated STAs. The 802.11 be release specifies both the NSTR operation for MLDs subject to NSTR constraints and the STR operation for MLDs not subject to NSTR constraints. The 802.11 be specifications indicate the mandatory support of STR operation on each pair of links (i.e., each pair of affiliated APs) for an AP MLD (that is not a NSTR mobile AP). The 802.11 be specifications indicate the optional support of STR operation and the optional support of NSTR operation for a non-AP MLD.

[0119] A non-AP MLD signals its NSTR constraints to an AP MLD as follows. During the association procedure, when at least one of its link pair (i.e., one couple / pair of its affiliated non- AP STAs) is subject to NSTR constraints, the non-AP MLD signals a NSTR Indication Bitmap in each Per-STA Profile subelement of the Link Info field of the Basic Multi-Link element carried in an Association Request frame sent to the AP MLD. Each NSTR Indication Bitmap in a Per-STA Profile subelement defines the NSTR constraints (hence NSTR link pairs) for the link concerned by the Per-STA Profile subelement (identified in the Link ID subfield).

[0120] The size of the NSTR Indication Bitmap is 1 or 2 Octets.

[0121] The signalling of the NSTR / STR status of a link pair i, j in the NSTR Indication Bitmap is provided using the value (i) of the Link ID subfield provided in the corresponding Per-STA Profile subelement and the positions (j) of each bit provided in the NSTR Indication Bitmap of the same Per-STA profile subelement. Each bit Bj (with j i) in the NSTR Indication Bitmap subfield included in the Per-STA Profile subelement with Link ID subfield equal to i (where 0 < i < 15 ) is set to 1 if the link pair corresponding to Link IDs equal to <i, j> forms an NSTR link pair, where j is the link ID of the link on which another STA (not operating on link i) affiliated with the same MLD is operating on; otherwise (STR link pair), the bit Bj is set to 0. Bit Bi in the NSTR Indication Bitmap subfield included in the Per-STA Profile subelement with Link ID subfield value equal to i is reserved.

[0122] After the association procedure, during operations, a non-AP MLD that has set the NSTR Status Update Support subfield to 1 in the Extended MLD Capabilities And Operation subfield of the Common Info field of the Basic Multi-Link element carried in an Association Request frame can update its NSTR Indication Bitmap. Upon a link addition event, a non-AP MLD can update its NSTR Indication Bitmap in each Per-STA Profile subelement of a Reconfiguration Multi-Link element carried in a Link Reconfiguration Request frame. Upon a BSS operating channel switch event, a non-AP MLD can update its NSTR Indication Bitmap in each Per-STA Profile subelement of a Reconfiguration Multi-Link element carried in a Multi-Link Operation Update Request frame.

[0123] On a given non-AP MLD implementation, the NSTR constraint for a couple / pair of affiliated non-AP STAs operating over a pair of links depends mainly on a minimum frequency separation or gap between the links for STR operation that is specific to the non-AP MLD, but may also depend on some other parameters such as the transmission power, the Modulation and Coding Scheme (MCS), etc., used for each link. It should be noticed that the NSTR constraint dependency against the parameters listed above is specific to a given non-AP MLD implementation. A non-AP MLD computes its NSTR Indication Bitmap knowing these internal and intrinsic parameters.

[0124] To help the AP MLD for future actions within its BSS, a non-AP MLD may signal the minimum frequency gap within a so-called “Frequency Separation For STR” subfield in the MLD Capabilities And Operations subfield of the Common Info field of the Basic Multi-Link element carried in an Association Request frame. This “Frequency Separation For STR” subfield indicates the minimum frequency gap between any two links that is recommended by the non-AP MLD for STR operation.

[0125] Figure 1 illustrates a typical 802.11 network environment involving ML transmissions between MLDs in which embodiments of the present disclosure may be implemented.

[0126] Wireless communication network 100 involves an AP MLD 1 10 and two non-AP MLDs 120 and 130. In the example, the two non-AP MLDs are considered to be NSTR update capable and have declared their corresponding capabilities to the AP MLD 110. Of course, another number of non-AP MLDs registering to the AP MLD 110 and then exchanging frames with it may be contemplated.

[0127] AP MLD 110 has multiple affiliated APs, two affiliated APs 1 11 and 112 (also referenced AP1 , AP2 respectively) in the exemplary Figure 1 , each of which behaves as an 802.11 AP over its 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 in replacement or in addition to these three bands. Also, a higher number of affiliated APs than two may be contemplated in embodiments. An affiliated AP may declare a first operating channel -“BSS operating channel” - when no bandwidth expanding is implemented through the enabling of the DBE mechanism described below. It is the operating channel seen by both the UHR and the legacy non-AP MLD and stations. On the other hand, when the DBE mechanism is enabled, the operating channel is expanded - “DBE operating channel”. The DBE operating channel is only seen by the UHR non-AP MLD and stations. Whatever the scenario, the operating channel offered by an AP is referred below to as “AP’s operating channel”.

[0128] The non-AP MLDs 120, 130 have multiple affiliated non-AP STAs, each of which behaves as an 802.11 non-AP STA in a BSS (managed by an affiliated AP 111 or 112) to which it registers and over an operating channel agreed on with the affiliated AP of the BSS, taking into account any bandwidth capability of the affiliated non-AP STA. In the exemplary Figure 1 , two non-AP STAs 121 and 122 (also referenced A1 and A2 respectively) are affiliated with non-AP MLD 120 and two non-AP STAs 131 and 132 (also referenced B1 and B2 respectively) are affiliated with non-AP MLD 130. Of course, a higher number of affiliated non-AP STAs per non-AP MLD than two may be contemplated in embodiments. The operating channel used by a STA is referred below to as “STA’s operating channel”.

[0129] For illustrative purposes, non-AP MLDs 120 and 130 are multi-radio non-AP MLDs. For example, AP 111 is set to operate on channel 138 corresponding to an 80MHz operating channel in the 5 GHz frequency band and AP 1 12 is set to operate on channel 7 corresponding to an 80MHz operating channel in the 6 GHz frequency band. In another example, the affiliated STAs could operate on different frequency bands and channels.

[0130] Each affiliated AP offers a link towards the AP MLD 110 to the affiliated non-AP STAs of a non-AP MLD (120 or 130). Hence, the links for each non-AP MLD can be merely identified with the identifiers of the respective affiliated APs, referred above to as “link ID”. For example, the affiliated AP 111 is assigned with link ID 0 and the affiliated AP 112 is assigned with link ID 1 .

[0131] To perform multi-link communications, each non-AP MLD 120, 130 has to discover, authenticate, associate and set up multiple links with the AP MLD 110 during the association procedure, each link being established between an affiliated AP of the AP MLD 110 and an affiliated non-AP STA ofthe non-AP MLD. Each of such links, referred to as “enabled link” enables individual channel access and frame exchanges between the non-AP MLD and the AP MLD based on supported capabilities exchanged during association.

[0132] The discovery phase is referred below to as ML discovery procedure, and the multi-link setup phase (or association phase) is referred below to as ML setup procedure.

[0133] The ML discovery procedure allows the non-AP MLD to discover the wireless communication network 100, i.e. , the various links to the AP MLD offered by the multiple affiliated APs. The ML discovery procedure thus seeks to advertise the various affiliated APs of the AP MLD, together with the respective network information, e.g. including all or part of capabilities and operation parameters such as the BSS operating channel and the DBE operating channel in case the AP MLD supports the DBE mode. Once a non-AP MLD has discovered the wireless communication network 100 through the ML discovery procedure and after an MLD authentication procedure, the ML setup procedure allows it to select a set of candidate setup links between its own affiliated non-AP STAs and some of the discovered affiliated APs, and to request the AP MLD 110 to set up these links with dedicated operating channels, which may be accepted or refused by the AP MLD. If the AP MLD accepts, the non-AP MLD is provided with an Association Identifier (AID) by the AP MLD, which AID is used by the affiliated non-APs of the non-AP MLD to wirelessly communicate over the multiple links (communication channels) with their corresponding affiliated APs.

[0134] For illustrative purpose, in wireless communication network 100, during the ML setup procedures, two candidate setup links have been requested by non-AP MLD 120 and accepted by AP MLD 110: a first link 151 between affiliated AP 1 11 (AP1) and affiliated non-AP STA 121 (A1) with an agreed operating channel for non-AP STA 121 , a second link 152 between affiliated AP 112 (AP2) and affiliated non-AP STA 122 (A2) with an agreed operating channel for non-AP STA 122. Similarly, two candidate setup links have been requested by multi-radio non-AP MLD 130 and accepted by AP MLD 110: a first link 161 between affiliated AP 111 (AP1) and affiliated non-AP STA 131 (B1) with an agreed operating channel for non-AP STA 131 , a second link 162 between affiliated AP 112 (AP2) and affiliated non-AP STA 132 (B2) with an agreed operating channel for non-AP STA 132. During the ML setup procedure, the non-AP MLDs declare part or all of their capabilities to the AP MLD. For this, appropriate fields are provided in the management frames. In particular, some of the management frames exchanged during the ML discovery and ML setup procedures contains an Information Elements specific to the Multi-Link Operation (MLO), referred to as Basic Multi-Link element in P802.1 1 be / D7.0. De facto, in all Management frames that include a Basic Multi-Link element except the Authentication frames, a multi-radio non-AP MLD is able to indicate its NSTR Indication Bitmap, its Frequency Separation For STR capability and its NSTR Status Update Support capability.

[0135] Figure 2 schematically illustrates a frequency view 200 of links setup between an AP MLD and a non-AP MLD. The view shows the frequency edges used as reference for the computation of the NSTR status of a link pair in the process of filling in the NSTR Indication Bitmap.

[0136] As explained above, a non-AP MLD computes its NSTR Indication Bitmap knowing its internal and intrinsic parameters such as the minimum frequency gap between links for STR operation, the transmission power, the MCS, and so on. A non-AP MLD may provide the value of its minimum frequency gap to the AP MLD through the “Frequency Separation For STR” subfield in the MLD Capabilities And Operations subfield of the Common Info field of the Basic Multi-Link element carried in an Association Request frame. The frequency gap is specified as the difference between the nearest frequency edges of the two links (hence operating channels) considered.

[0137] When computing the NSTR status of a link pair, the non-AP MLD ensures that the minimum frequency separation indicated in the Frequency Separation For STR subfield starts from the frequency edge of the maximum supported bandwidth indicated by the Supported Channel Width Set subfield in the HE Capabilities element and the Support For 320MHz in 6GHz subfield in the EHT Capabilities element of each link. Hence, it is computed from the frequency edges of the operating channels of the affiliated non-AP STAs for the links concerned.

[0138] Figure 2 schematically illustrates the frequency view of Link#0 and Link#1 setup respectively between affiliated AP1 111 and affiliated non-AP STA A1 121 and between affiliated AP2 112 and affiliated non-AP STA A2 122, as described previously in reference to Figure 1.

[0139] The AP’s operating channel 211 of affiliated AP1 1 11 is 80MHz in channel 138 of the 5GHz frequency band. It is made of one primary 20MHz channel (‘P’ in the Figure) and three secondary 20MHz channels. The lower and higher frequency edges - i.e., ends of the range - of BSS operating channel 21 1 are 5.65GHz and 5.73GHz, respectively.

[0140] However, the STA’s operating channel 221 of affiliated non-AP STA A1 121 associated with AP1 111 is 40MHz as agreed with AP1. In the scenario of the Figure, it is mapped with the lower 40MHz part of AP’s operating channel 211 of affiliated AP1 111 (i.e., the part including the primary 20MHz channel). The lower frequency edge of STA’s operating channel 221 is 5.65GHz and the higher frequency edge 231 of STA’s operating channel 221 is 5.69GHz.

[0141] The AP’s operating channel 212 of affiliated AP2 112 is 80MHz in channel 7 of the 6GHz frequency band. It is made of one primary 20MHz channel and three secondary 20MHz channels. The lower and higher frequency edges of AP’s operating channel 212 are 5.945GHz and 6.025GHz, respectively.

[0142] However, the STA’s operating channel 222 of affiliated non-AP STA A2 122 is 80MHz as agreed with affiliated AP2 112; it is exactly mapped (edge to edge) with the entire AP’s operating channel 212 of AP2. The lower frequency edge 232 of STA’s operating channel 222 is 5.945GHz and the higher frequency edge of STA’s operating channel 222 is 6.025GHz.

[0143] In 802.1 1 , an AP MLD and a non-AP MLD exchange their bandwidth capabilities through Capabilities elements for all their affiliated STAs and the AP MLD indicates the current AP’s operating channel through Operation elements for all its affiliated APs. Then, during operation, each affiliated non-AP STA operates within the signalled AP’s operating bandwidth. Depending on its bandwidth capabilities, the affiliated non-AP STA is expected to operate within the entire AP’s operating bandwidth (like affiliated non-AP STA A2 122) or within a sub-band thereof covering the primary channel of the AP’s operating channel (like affiliated non-AP STA A1 121).

[0144] The frequency edges 231 and 232 corresponding respectively to the higher frequency edge of STA’s operating channel 221 of affiliated non-AP STA A1 121 and to the lower frequency edge of STA’s operating channel 222 of affiliated non-AP STA A2 122 are taken as references to compute the current frequency gap 230 observed currently within the BSSs. This is because they are the nearest / closest frequency edges between STA’s operating channels 221 and 222.

[0145] To determine the NSTR or STR status of the link pair <0,1 > (in order to fill in the NSTR Indication Bitmaps), the non-AP MLD 120 compares its internal and intrinsic minimum frequency gap for STR operation (Frequency Separation For STR) to the current frequency gap 230.

[0146] In the scenario of the Figure, the current frequency gap 230 is 255MHz (= FScurrent) .

[0147] As an example, if Frequency Separation For STR of non-AP MLD 120 is 230MHz (=FSinternai), non-AP MLD 120 identifies the link pair <0,1 > as STR (FScurrent > FSinternai) . The bit B0 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 0, and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 0.

[0148] On the other hand, if Frequency Separation For STR of non-AP MLD 120 is 300MHz (= FSinternai) , non-AP MLD 120 identifies the link pair <0,1 > as NSTR (FScurrent < FSinternai) . The bit B0 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 1 , and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 1 .

[0149] The NSTR Indication Bitmap for each link setup with the AP MLD 110 can be built accordingly. Such NSTR Indication Bitmap built based on the nearest frequency edges of the non-AP STA’s operating channels is referred below to as “legacy” NSTR Indication Bitmap. Each corresponding individual NSTR status (for a link pair) may also be referred below to as “legacy” NSTR status.

[0150] However, multiple 802.11 features or mechanisms exist that involve, for a non-AP STA, to switch from its STA’s operating channel to another channel - which may or may not overlap its initial STA’s operating channel depending on the mechanism - referred below to as “substitute” channel. These mechanisms or “channel switching mechanisms” tend to optimize spectrum’s usage, hence to improve network efficiency, by allowing such non-AP STA to communicate - usually with its AP - at an improved data rate or despite unavailability of its STA’s operating channel. The substitute channel may be a subpart of the AP’s operating channel (which is thus larger / wider than the STA’s operating channel of part or all of its associated STAs). In embodiments, the substitute channel is outside the AP’s operating channel, and can be referred to as “off-channel”. Alternatively, the substitute channel may be wider than - and includes - the AP’s operating channel, e.g., when a mechanism that expands the AP’s operating channel is implemented.

[0151] Exemplary mechanisms include the Dynamic Subband Operation (DSO), the NonPrimary Channel Access (NPCA), the Dynamic Bandwidth Expansion (DBE) and the High Efficiency Subchannel Selective Transmission (HE SST). Below, DSO or NPCA or DBE or HE SST mechanism and DSO or NPCA or DBE or HE SST mode, or simply DSO, NPCA, DBE or HE SST, refer to the same feature.

[0152] The DSO mechanism addresses the problem of bandwidth wastage occurring when the operating bandwidth capabilities between an AP and its non-AP STAs differ, typically when a 320MHz capable AP is associated with smaller-bandwidth capable non-AP STAs. The principle of the DSO mechanism is to allow, typically, a 320MHz-operating-bandwidth AP to dynamically indicate to a 160MHz-operating-bandwidth non-AP STA that it will be served on its secondary 160MHz channel during a next TXOP. The DSO mechanism may be extended to any AP / non-AP STA operating bandwidth combination where the AP’s operating channel is larger than the STA’s operating channel. Through the DSO mechanism, at the beginning of a 320MHz TXOP, the AP can typically decide to allocate resources to some non-AP STAs on the primary 160MHz channel (i.e., the 160MHz sub-band including the 20MHz primary channel) and resources to some DSO capable non-AP STAs on the secondary 160MHz channel (i.e., the 160MHz sub-band not including the 20MHz primary channel). This allows the entire 320MHz of the AP’s operating channel to be used, thus resulting in better resource utilization. The AP’s operating channel to be considered for DSO operation can be either the BSS operating channel or the DBE operating channel.

[0153] In other words, DSO is a mechanism where a DSO non-AP STA that has an operating bandwidth narrower than the DSO AP can dynamically be allocated frequency resources outside of its current operating bandwidth within the DSO AP’s BSS bandwidth or within the DSO AP’s DBE bandwidth, on a per-TXOP basis.

[0154] In yet other words, DSO is a mechanism where a DSO non-AP STA that has an operating bandwidth narrower than the DSO AP can dynamically be allocated frequency resources outside of its current operating bandwidth within the DSO AP’s operating bandwidth, on a per-TXOP basis. The DSO AP’s operating bandwidth is either the BSS operating bandwidth or the DBE operating bandwidth. The NPCA mechanism addresses the problem of bandwidth wastage occurring when only the primary channel of the AP’s operating channel is busy due to a neighbouring WLAN. This is due to the fact that, in an 802.11 WLAN, if the primary channel is sensed as busy, the AP and non-APs STAs are not allowed to send any frame in any channels of the AP’s operating channel, even if the secondary channels are idle. This means that, if only the primary channel of the AP’s operating channel is busy, the secondary channels in the rest of the AP’s operating channel - even if they are idle - cannot be used during the occupancy time where the primary channel is busy. The principle of NPCA is, upon detection of a busy primary channel due to an Overlapping Basic Service Set (OBSS), an AP and associated non-AP STA(s) switch to a non-primary / secondary channel (e.g. called anchor channel or NPCA primary channel or “substitute” channel) to run an EDCA backoff procedure and initiate a data transmission in their own Basic Service Set (BSS). The data transmission may be conducted for at most a TXOP duration corresponding to the basic Network Allocation Vector (NAV) value set based on the detected OBSS interference. The anchor channel or NPCA primary channel or “substitute” channel belongs to the AP’s operating channel to allow the AP to use it, even if the anchor channel or NPCA primary channel is outside the STA’s operating channel. As a consequence, the frame exchange takes place on a subset of the AP’s operating channel. Upon completion of the frame exchange, the AP and non- AP STA(s) switch back to the primary channel (if idle). The AP’s operating channel to be considered for NPCA operation is either the BSS operating channel or the DBE operating channel.

[0155] For example, the anchor channel or NPCA primary channel or “substitute” channel can be signaling in an NPCA Primary Channel subfield (not shown) in the NPCA Configuration Parameters field 426 (described hereafter in reference with Figure 4b). This NPCA Primary Channel subfield (not shown) indicates the channel number of a channel within the BSS bandwidth or within the DBE bandwidth that corresponds to the channel that the NPCA AP and its associated NPCA non-AP STAs switch to in order to perform NPCA operation. In other words, this NPCA Primary Channel field (not shown) indicates the channel number of a channel within the AP’s operating channel that corresponds to the channel that the NPCA AP and its associated NPCA non-AP STAs switch to in order to perform NPCA operation. The AP’s operating channel is either the BSS operating channel or the DBE operating channel.

[0156] In other words, NPCA allows STAs within a BSS to switch to an alternate channel during a period of time when OBSS activity is detected on part of the BSS operating channel or on part of the DBE operating channel.

[0157] The DBE mechanism addresses the problem of bandwidth wastage occurring typically in an enterprise deployment when some APs are experiencing low traffic load while some other APs are experiencing high traffic load. In such cases, the bandwidth of APs experiencing low traffic load is almost unused; it can be considered as wasted. In enterprise deployments, it is observed that neighbouring APs use different primary channels and non-overlapping bandwidths. Typical deployments use 20MHz or 40MHz AP’s operating bandwidth in 5GHz band and 40MHz or 80MHz AP’s operating bandwidth in 6GHz band. As a result, current enterprise deployments do not have an easy way to take profit of wider 160MHz or 320 MHz bandwidths to reach high throughput gains.

[0158] The DBE mechanism is introduced by the 802.11 bn TG, together with the Multi-AP Coordination (MAPC) scheme which is advantageously used to identify time periods when some APs are experiencing high traffic load while some other neighbouring APs are experiencing low traffic load. The APs may exchange information about their traffic load. Thanks to an identified time period, an AP experiencing high traffic load can enable the DBE mode in its BSS in order to perform data frame exchanges on an expanded bandwidth (compared to the BSS bandwidth) with its associated non-AP STAs also supporting the DBE mode. The legacy non-AP STAs not supporting the DBE mode remain operating on the BSS bandwidth only.

[0159] In other words, the DBE mechanism allows an AP to dynamically expand its AP’s operating bandwidth (or channel) to be greater than the basic service set (BSS) bandwidth (or channel), for associated ultra-high reliability (UHR) non-AP STAs that support DBE mode. The AP’s operating bandwidth (or channel) of the AP for DBE operation when DBE mode is enabled by the AP is called the DBE bandwidth (or channel). The DBE bandwidth (or channel) is greater than the BSS bandwidth (or channel) of the AP. The DBE operating channel and the BSS operating channel use the same primary channel. During DBE operation, a non-AP STA performs data frames exchanges with the AP over the expanded DBE channel (hence “substitute channel”).

[0160] Contrary to some legacy mechanisms such as Operating Mode Indication (OMI), the DBE mode is not visible to legacy non-AP STAs and it is designed for frequent and dynamic bandwidth expansions.

[0161] The DBE mode is a self-sufficient channel switching mechanism. However, it should be noticed that the DBE mode can be used as a companion for DSO, NPCA and HE SST modes. Advantageously, operating on the expanded bandwidth (i.e. , DBE Bandwidth) can allow an AP to enable the DSO or NPCA or HE SST mode which enablement is prohibited on the non-expanded bandwidth (i.e., BSS bandwidth).

[0162] The HE SST mechanism was introduced in the IEEE 802.1 1 ax standard. The HE SST mechanism allows an 80MHz non-AP STA to operate on the secondary 80MHz channel of a 160MHz AP’s operating channel or a 20MHz non-AP STA to operate outside the primary 20MHz channel of a wider AP’s operating channel. The HE SST operation is performed during prenegotiated Target Wake Time (TWT) Service Periods (SPs) of an individual TWT agreement. In this respect, the HE SST mechanism sounds to be a starting point of the DSO mechanism.

[0163] These various channel switching mechanisms have been introduced and designed in a single-link context only. They are not fully adapted to a multi-link context and may impact MLO efficiency. For example, for the duration of the TXOP during which an affiliated non-AP STA operates on the substitute channel, the legacy NSTR Indication Bitmap signalled during the association procedure may not be up-to-date because the operating channel(s) of the affiliated non-AP STA is modified to the substitute channel. This may lead to inefficient Multi Link Operation (MLO) between the affiliated AP and affiliated non-AP STA during this TXOP, especially for the case where a STR link pair becomes a NSTR link pair during the TXOP due to the channel switch. This downside is further exacerbated when the usage of the channel switching mechanisms is considered in parallel on several links setup between the AP MLD and the non-AP MLD.

[0164] On the other hand, the NSTR Indication Bitmap update procedure specified in P802.11 be / D7.0 (e.g., upon a link addition event or a BSS operating channel switch event) is not adapted to the timing of these channel switching mechanisms, which is quite shorter than the timings of these events addressed in P802.1 1 be / D7.0.

[0165] New handlings of the NSTR Indication Bitmaps are now proposed.

[0166] Embodiments provide that the Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup with two respective APs affiliated with an AP MLD be determined based on the frequency edges of the AP’s operating channels of the two affiliated APs, rather than the frequency edges of the operating channels of the two affiliated non-AP STAs. The AP’s operating channel of an affiliated AP may correspond to the BSS operating channel or to the DBE operating channel.

[0167] Taking into account the AP’s operating channels of the affiliated APs advantageously ensures that any (all) substitute channel(s) for the channel switching mechanisms are liable to be encompassed, hence they are taken into account when computing the NSTR statuses.

[0168] A NSTR Indication Bitmap built with such statuses (computed from the edges of the AP’s operating channels) is referred below to as “universal” NSTR Indication Bitmap for ease of explanation. A corresponding NSTR status may also be referred to as “universal” NSTR status. As one can easily understand, despite the activation / enabling of the above channel switching mechanisms (e.g., DSO, NPCA, DBE and HE SST), the universal NSTR Indication Bitmap does not change, contrary to the legacy NSTR Indication Bitmap.

[0169] Figures 3a and 3c schematically illustrate frequency views 300a and 300c, respectively, of links setup between an AP MLD and a non-AP MLD for the computation of a universal NSTR status according to these embodiments.

[0170] The explanations above with reference to Figure 2 apply here, with the exception that the frequency edges taken into account for the NSTR status computation are determined in a different way. In particular, each non-AP MLD has its own internal and intrinsic parameters, such as the minimum frequency gap between links for STR operation, the transmission power, the MCS, to perform such computation.

[0171] In Figure 3a, channel 321 a’ is a substitute channel to be used by affiliated non-AP STA A1 121 in case one channel switching mechanism is activated (e.g., DSO, NPCA), usually for the duration of the TXOP on STA’s operating channel 321 a’. Substitute channel 321 a’ can be viewed as a translation of initial STA’s operating channel 321 a. Substitute channel 321 a’ of affiliated non- AP STA A1 121 is 40MHz in the present scenario, and it is mapped with the higher part of AP’s operating channel 311 a of corresponding affiliated AP1 111 (i.e., the part including upper secondary 20MHz channels). The lower frequency edge of substitute channel 321 a’ is 5.69GHz whereas the higher frequency edge 331 a of substitute channel 321 a’ is 5.73GHz. No substitute channel is defined for affiliated non-AP STA A2 122 as its STA’s operating channel 322a perfectly matches AP’s operating channel 312a of corresponding affiliated AP AP2 112. Of course, this may not be the case in every scenario, and a substitute channel may be defined for affiliated non-AP STA A2 122 as a subpart of AP’s operating channel 312a that is not included in the initial STA’s operating channel 322a of affiliated non-AP STA A2 122.

[0172] As described here above, through the use of one channel switching mechanism, the STA’s operating channel 321 a of affiliated non-AP STA A1 121 agreed with affiliated AP1 111 during the association procedure is moved to the substitute channel 321 a’ during the channel switching mechanism (DSO, NPCA, HE SST) operations (during the TXOP). As a result, the frequency edges 231 , 232 used as references for the computation of the current frequency gap 230 (see Figure 2) are no longer valid. This means that the computed legacy NSTR status for link pair <0,1 > (hence the legacy NSTR Indication Bitmap) may also not be valid during the channel switching mechanism operations.

[0173] As shown in Figure 3a, the NSTR status of the link pair is computed based on the nearest frequency edges of the AP’s operating channels of the two affiliated APs concerned.

[0174] These new frequency edges are used as references for the computation of the current frequency gap 330a observed currently within the BSSs. The frequency edges 331 a and 332a corresponding respectively to the higher frequency edge of AP’s operating channel 311 a of affiliated AP1 111 and to the lower frequency edge of AP’s operating channel 312a of affiliated AP2 112 are now taken into account for the computation of the current frequency gap 330a observed currently within the BSSs.

[0175] In order to identify the universal NSTR status of link pair <0,1 > and to compute its universal NSTR Indication Bitmap, the non-AP MLD 120 compares its internal and intrinsic minimum frequency gap for STR parameter to the current frequency separation 330a observed currently within BSSs. In other words, the NSTR status of the link pair is obtained by comparing a frequency difference (gap 330a) between the nearest frequency edges 331 a, 332a of the AP’s operating channels of the two affiliated APs AP1 111 , AP2 112 with the minimum frequency gap (Frequency Separation For STR) value specific to the non-AP MLD 120.

[0176] In the scenario of Figure 3a, the current frequency gap 330a between frequency edges 331 a and 332a is 215MHz (=FScurrent) .

[0177] If Frequency Separation For STR of non-AP MLD 120 is 200MHz (=FSintemai), non-AP MLD 120 identifies the link pair <0,1 > as STR (FScurrent > FSinternai) . The bit B0 (NSTR status) in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 0, and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 0.

[0178] On the other hand, if Frequency Separation For STR of non-AP MLD 120 is 300MHz (= FSinternai) , non-AP MLD 120 identifies the link pair <0,1 > as NSTR (FScurrent < FSinternai) . The bit B0 (NSTR status) in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 1 , and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 1 .

[0179] In Figure 3c, channel 321 c’ is a substitute channel to be used by affiliated non-AP STA A1 121 in case one channel switching mechanism is activated (e.g., DBE), usually forthe duration of a TXOP. Substitute channel 321 c’ can be viewed as an expansion of initial STA’s operating channel 321 c. Substitute channel 321 c’ overlaps initial STA’s operating channel 321 c.

[0180] Such channel switching mechanism (e.g., DBE) is typically activated by the AP, here affiliated AP1 111. During the activation of the mechanism, affiliated AP1 111 also expands its AP’s operating bandwidth from initial operating channel 311 c (40MHz) to the expanded operating channel 311 c’ (80MHz). Typically, in case of DBE mode, initial operating channel 311 c corresponds to the BSS operating channel and expanded operating channel 31 1 c’ corresponds to the DBE operating channel.

[0181] Substitute channel 321 c’ of affiliated non-AP STA A1 121 is 80MHz in the present scenario, and it perfectly matches the AP’s operating channel 311 c’ of corresponding affiliated AP1 111. The lower frequency edge of substitute channel 321 c’ is 5.65GHz whereas the higher frequency edge 331 c of substitute channel 321 c’ is 5.73GHz.

[0182] No substitute channel is defined for affiliated non-AP STA A2 122 as its STA’s operating channel 322c perfectly matches AP’s operating channel 312c of corresponding affiliated AP AP2 112. Of course, this may not be the case in every scenario, and a substitute channel may also be defined for affiliated non-AP STA A2 122.

[0183] As described here above, through the use of one channel switching mechanism (e.g., DBE), initial STA’s operating channel 321 c of affiliated non-AP STA A1 121 agreed with affiliated AP1 111 during the association procedure is moved to substitute channel 321 c’ during the channel switching mechanism (DBE) operations (during the TXOP). As a result, the frequency edges 231 , 232 used as references for the computation of the current frequency gap 230 (see Figure 2) are no longer valid. This means that the computed legacy NSTR status for link pair <0,1 > (hence the legacy NSTR Indication Bitmap) may also not be valid during the channel switching mechanism operations.

[0184] As shown in Figure 3c, the NSTR status of the link pair is computed based on the nearest frequency edges of the AP’s operating channels of the two affiliated APs.

[0185] These new frequency edges are used as references for the computation of the current frequency gap 330c observed currently within the BSSs. The frequency edges 331 c and 332c corresponding respectively to the higher frequency edge of AP’s operating channel 311 c’ of affiliated AP1 111 and to the lower frequency edge of AP’s operating channel 312c of affiliated AP2 112 are now taken into account for the computation of the current frequency gap 330c observed currently within the BSSs.

[0186] In order to identify the universal NSTR status of link pair <0,1 > and to compute its universal NSTR Indication Bitmap, the non-AP MLD 120 compares its internal and intrinsic minimum frequency gap for STR parameter to the current frequency separation 330c observed currently within BSSs. In other words, the NSTR status of the link pair is obtained by comparing a frequency difference (gap 330c) between the nearest frequency edges 331 c, 332c of the AP’s operating channels of the two affiliated APs AP1 111 , AP2 112 with the minimum frequency gap (Frequency Separation For STR) value specific to the non-AP MLD 120.

[0187] In the scenario of Figure 3c, the current frequency gap 330c between frequency edges 331 c and 332c is 215MHz (=FScurrent) .

[0188] If Frequency Separation For STR of non-AP MLD 120 is 200MHz (= FSinternai), non-AP MLD 120 identifies the link pair <0,1 > as STR (FScurrent > FSinternai) . The bit B0 (NSTR status) in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 0, and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 0.

[0189] On the other hand, if Frequency Separation For STR of non-AP MLD 120 is 300MHz (= FSinternai) , non-AP MLD 120 identifies the link pair <0,1 > as NSTR (FScurrent < FSinternai) . The bit B0 (NSTR status) in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 1 , and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 1 .

[0190] To perform the NSTR status computation, the non-AP MLD obtains the AP’s operating channels of the affiliated APs from the AP MLD, usually during the association procedure with the AP MLD.

[0191] The non-AP MLD may report the NSTR statuses (i.e., the universal NSTR Indication Bitmaps) during association or re-association of the non-AP MLD with the AP MLD. It means that the universal NSTR Indication Bitmap is computed by the non-AP MLD during the association procedure with an AP MLD and may be used afterward during MLO operations.

[0192] For example, the non-AP MLD decides to compute and use the universal NSTR Indication Bitmap during the association procedure when it identifies that both non-AP MLD and AP MLD support DSO and / or NPCA and / or DBE and / or HE SST modes through the exchange of corresponding Capabilities (e.g., UHR Capabilities subfield 400 described below with reference to Figure 4a) in the Common Info field of Basic Multi-Link element carried Association Request / Response frames during the association procedure.

[0193] By reporting the new NSTR statuses as early as the association, the use of the DSO, NPCA, DBE, HE SST or the like mechanism can take place without additional signalling frame and without risks of interference between channels simultaneously used by the non-AP STA (i.e., risks that a STR pair becomes NSTR).

[0194] In a variant, the non-AP MLD may decide to compute and use the universal NSTR Indication Bitmap during ML operation, in particular upon the AP MLD activating a Dynamic Subband Operation (DSO) or a Non-Primary Channel Access (NPCA) or Dynamic Bandwidth Expansion (DBE) or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism on one link of the link pair at the non-AP MLD. The activation (or enabling) of the channel switching mechanism can be initiated by the AP MLD through the exchange of an Operation Mode notification frame (described below with reference to Figure 9a, 9b).

[0195] If the universal NSTR Indication Bitmap is reported only during ML operation under a channel switching mechanism, it may be envisioned to switch back to the legacy NSTR Indication Bitmap when the channel switching mechanism is no longer operating. In that case, upon the AP MLD deactivating the DSO or NPCA or DBE or HE SST, the non-AP MLD may report to the AP MLD a NSTR status of the link pair (or of all link pairs) that is based on frequency edges of only STA’s operating channels of the non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair, i.e. , a legacy NSTR status.

[0196] In the scenarios of Figures 3a and 3c, a non-AP MLD should compute the Universal NSTR indication bitmap by comparing its internal and intrinsic minimum frequency gap for STR operation requirement to the current frequency gap observed within the BSSs it is operating in. The current frequency gap is computed using as references the nearest frequency edges of the AP’s operating channels of the APs affiliated with the AP MLD the non-AP MLD is associated with. The AP’s operating channel of an affiliated AP may correspond to the BSS operating channel or to the DBE operating channel when the DBE mechanism is enabled.

[0197] Regarding the subfield “Frequency Separation For STR / AP MLD Type Indication” of the MLD Capabilities And Operations subfield as referred in Table 9-417n of P802.1 1 be / D7.0, when transmitted by a non-AP STA affiliated with a non-AP MLD, the subfield is the Frequency Separation For STR subfield and it indicates the minimum frequency gap between the AP’s operating channel of any APs affiliated with the AP MLD it is associated with that is recommended by the non-AP MLD for STR operation. The frequency gap is specified as the difference between the nearest frequency edges of the AP’s operating channels of any two affiliated APs. The AP’s operating channel of an affiliated AP may correspond to the BSS operating channel or to the DBE operating channel.

[0198] Regarding the MLD capability and operation signalling, the non-AP MLD ensures that the minimum frequency gap indicated in the Frequency Separation For STR subfield starts from the nearest frequency edges of the AP’s operating channel indicated in the UHR / EHT / HEA / HT / HT Operation element(s) of any two APs affiliated with the AP MLD it is associated with.

[0199] Also, a non-AP MLD may set the Frequency Separation For STR subfield in the Common Info field of the Basic Multi-Link element to a nonzero value if it intends to indicate the minimum frequency gap that is recommended between the nearest frequency edges of the AP’s operating channels of any two APs affiliated with the AP MLD it is associated with for the non-AP MLD for STR operation; otherwise, the non-AP MLD sets the Frequency Separation For STR subfield to 0.

[0200] Other embodiments provide that the Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup between two respective non-AP stations (STAs) affiliated with the non-AP MLD and two respective APs affiliated with an AP MLD be determined based on a frequency edge of channels comprising a STA’s operating channel of a first one of the affiliated non-AP STAs that corresponds to a first link of the link pair and a (or more if multiple) substitute channel of the first affiliated non-AP STA, and a frequency edge of the other link of the link pair, i.e., corresponding to the other affiliated non-AP STA, rather than a frequency edge of the STA’s operating channels of the two affiliated non-AP STAs only. Note that the frequency edge of the other link may be determined in the same way as the first link, i.e., be an edge of the set made of the STA’s operating channel and the substitute channel, if any, of the other affiliated non-AP STA (corresponding to this other link).

[0201] Considering all possible positions of the STA’s operating channels (initial operating channel and one or more possible substitute channels) advantageously ensures that any (all) substitute channel(s) for the channel switching mechanisms are encompassed, hence they are taken into account when computing the NSTR status.

[0202] The obtained NSTR status (more generally NSTR Indication Bitmap) is also referred below to as a “universal” NSTR status (resp. universal NSTR Indication Bitmap), despite the fact it is a variant of the embodiments above.

[0203] Figures 3b and 3d schematically illustrate frequency views 300b and 300d, respectively, of links setup between an AP MLD and a non-AP MLD for the computation of a universal NSTR status according to these other embodiments.

[0204] The explanations above with reference to Figure 2 apply here, with the exception that the frequency edges taken into account for the NSTR status computation are determined in a different way. In particular, each non-AP MLD has its own internal and intrinsic parameters, such as the minimum frequency gap between links for STR operation, the transmission power, the MCS, to perform such computation.

[0205] In Figure 3b, channel 321 b’ is a substitute channel to be used by affiliated non-AP STA A1 121 in case one channel switching mechanism is activated (e.g. DSO, NPCA), usually for the duration of the TXOP on STA’s operating channel 321 b’. Substitute channel 321 b’ can be viewed as a translation of initial STA’s operating bandwidth 321 b. Substitute channel 321 b’ of affiliated non-AP STA A1 121 is 20MHz in the present scenario, and it is mapped with a secondary 20MHz channel in the higher half of AP’s operating bandwidth 311 b of affiliated AP1 111. The lower frequency edge of substitute channel 321 b’ is 5.69GHz whereas the higher frequency edge 331 b of substitute channel 321 b’ is 5.71 GHz.

[0206] No substitute channel is defined for affiliated non-AP STA A2 122 as its STA’s operating channel 322b perfectly matches AP’s operating channel 312b of corresponding affiliated AP AP2 112. Of course, this may not be the case in every scenario, and a substitute channel may be defined for affiliated non-AP STA A2 122 as a subpart of AP’s operating channel 312b that is not included in the initial STA’s operating channel 322b of affiliated non-AP STA A2 122.

[0207] As described here above, through the use of one channel switching mechanism, the STA’s operating bandwidth 321 b of affiliated non-AP STA A1 121 agreed with affiliated AP1 111 during the association procedure is moved to the substitute channel 321 b’ during the channel switching mechanism (DSO, NPCA, HE SST) operations (during the TXOP). As a result, the frequency edges 231 , 232 used as references for the computation of the current frequency gap 230 (see Figure 2) are no longer valid. This means that the computed legacy NSTR status for link pair <0,1 > (hence the legacy NSTR Indication Bitmap) may also not be valid during the channel switching mechanism operations.

[0208] As shown in Figure 3b, the NSTR status of the link pair is based on the nearest frequency edge of the channels comprising the STA’s operating and substitute channels of the first affiliated non-AP STA to a frequency edge of the other link.

[0209] These new frequency edges are used as references for the computation of the current frequency gap 330b observed currently within the BSSs. The frequency edges 331 b and 332b corresponding respectively to the higher frequency edge of the group made of STA’s operating channel 321 b and substitute channel 321 b’ of affiliated non-AP STA A1 121 (here the higher frequency edge is the one of substitute channel 321 b’) and to the lower frequency edge of STA’s operating channel 322b (since there is no substitute channel for non-AP STA A2 122) of affiliated non-AP STA A2 122 are now taken into account for the computation of the current frequency gap 330b observed currently within the BSSs.

[0210] In order to identify the universal NSTR status of link pair <0,1 > and to compute its universal NSTR Indication Bitmap, the non-AP MLD 120 compares its internal and intrinsic minimum frequency gap for STR Operation parameter to the current frequency gap 330b observed currently within BSSs. In other words, the NSTR status of the link pair is obtained by comparing a frequency difference (gap 330b) between the nearest frequency edge of one link (here edge 331 b) to a frequency edge (here edge 332b) of the other link with a minimum frequency gap value specific to the non-AP MLD.

[0211] In the scenario of Figure 3b, the current frequency gap 330b between frequency edges 331 b and 332b is 235MHz (= FScurrent) .

[0212] If Frequency Separation For STR of non-AP MLD 120 is 230MHz (=FSintemai), non-AP MLD 120 identifies the link pair <0,1 > as STR (FScurrent > FSinternai) . The bit B0 (NSTR status) in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 0, and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 0.

[0213] If Frequency Separation For STR of non-AP MLD 120 is 300MHz (= FSinternai) , non-AP MLD 120 identifies the link pair <0,1 > as NSTR (FScurrent < FSinternai) . The bit B0 (NSTR status) in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 1 , and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 1 .

[0214] In Figure 3d, channel 321 d’ is a substitute channel to be used by affiliated non-AP STA A1 121 in case one channel switching mechanism is activated (e.g. DBE), usually for the duration of a TXOP. Substitute channel 321 d’ can be viewed as an expansion of initial STA’s operating channel 321 d. Substitute channel 321 d’ overlaps initial STA’s operating channel 321 d. Such channel switching mechanism (e.g. DBE) is typically activated by the AP, here affiliated AP1 111. During the activation of the mechanism, affiliated AP1 111 also expands its AP’s operating bandwidth from initial operating channel 311d (20MHz) to the expanded operating channel 311 d’ (80MHz). Typically, in case of DBE mode, initial operating channel 311d corresponds to the BSS operating channel and expanded operating channel 31 1d’ corresponds to the DBE operating channel.

[0215] Substitute channel 321 d’ of affiliated non-AP STA A1 121 is 40MHz in the present scenario, and it is mapped with the primary 40MHz channel in the lower half of AP’s operating bandwidth 311d’ of affiliated AP1 11 1. The lower frequency edge of substitute channel 321d’ is 5.65GHz whereas the higher frequency edge 331 d’ of substitute channel 321 d’ is 5.69GHz.

[0216] No substitute channel is defined for affiliated non-AP STA A2 122 as its STA’s operating channel 322d perfectly matches AP’s operating channel 312d of corresponding affiliated AP AP2 112. Of course, this may not be the case in every scenario, and a substitute channel may also be defined for affiliated non-AP STA A2 122.

[0217] As described here above, through the use of one channel switching mechanism (e.g. DBE), initial STA’s operating bandwidth 321 d of affiliated non-AP STA A1 121 agreed with affiliated AP1 1 11 during the association procedure is moved to substitute channel 321 d’ during the channel switching mechanism (DBE) operations (during the TXOP). As a result, the frequency edges 331d, 332d commonly used as references for the computation of the current frequency gap 330d during the association procedure are no longer valid. This means that the computed legacy NSTR status for link pair <0,1 > (hence the legacy NSTR Indication Bitmap) may also not be valid during the channel switching mechanism operations.

[0218] As shown in Figure 3d, the NSTR status of the link pair is based on the nearest frequency edge of the channels comprising the STA’s operating and substitute channels of the first affiliated non-AP STA to a frequency edge of the other link.

[0219] These new frequency edges are used as references for the computation of the current frequency gap 330d’ observed currently within the BSSs. The frequency edges 331 d’ and 332d corresponding respectively to the higher frequency edge of the group made of STA’s operating channel 321 d and substitute channel 321 d’ of affiliated non-AP STA A1 121 (here the higher frequency edge is the one of substitute channel 321 d’) and to the lower frequency edge of STA’s operating channel 322d (since there is no substitute channel for non-AP STA A2 122) of affiliated non-AP STA A2 122 are now taken into account for the computation of the current frequency gap 330d’ observed currently within the BSSs.

[0220] In order to identify the universal NSTR status of link pair <0,1 > and to compute its universal NSTR Indication Bitmap, the non-AP MLD 120 compares its internal and intrinsic minimum frequency gap for STR Operation parameter to the current frequency gap 330d’ observed currently within BSSs. In other words, the NSTR status of the link pair is obtained by comparing a frequency difference (gap 330d’) between the nearest frequency edge of one link (here edge 331 d’) to a frequency edge (here edge 332d) of the other link with a minimum frequency gap value specific to the non-AP MLD.

[0221] In the scenario of Figure 3d, the current frequency gap 330d’ between frequency edges 331 d’ and 332d is 255MHz (=FScurrent) .

[0222] If Frequency Separation For STR of non-AP MLD 120 is 230MHz (= FSinternai), non-AP MLD 120 identifies the link pair <0,1 > as STR (FScurrent > FSinternai) . The bit BO (NSTR status) in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 0, and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 0.

[0223] If Frequency Separation For STR of non-AP MLD 120 is 300MHz (= FSinternai) , non-AP MLD 120 identifies the link pair <0,1 > as NSTR (FScurrent < FSinternai) . The bit B0 (NSTR status) in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 1 can be set to 1 , and the bit B1 in NSTR Indication Bitmap of the Per-STA Profile subelement with Link ID subfield equal to 0 can be set to 1 .

[0224] This variant of the universal NSTR status is more optimal than the first embodiments because the effective positions of the STA’s operating channels of the affiliated non-AP STAs are taken into account rather than the AP’s operating channels of the affiliated APs.

[0225] To perform the NSTR status computation, the non-AP MLD obtains the substitute channel(s) from the AP MLD, usually during the association procedure with the AP MLD. For example, information about the substitute channel(s) may be provided through a Configuration element (e.g., DSO / NPCA / DBE Configuration element 420 described below with reference to Figure 4b). The element may carry parameters such as DSC channels positions, NPCA anchor channel position, DBE bandwidth, Maximum Supported DBE bandwidth, HE SST secondary channel position that permits to the non-AP MLD to know the positions of the (substitute) channels to be used by its affiliated non-AP STAs for the channel switching mechanism.

[0226] The non-AP MLD may compute and report the NSTR status of the link pair to the AP MLD during association or re-association of the non-AP MLD with the AP MLD. It means that the universal NSTR Indication Bitmap described in this variant is computed by the non-AP MLD during the association procedure with an AP MLD and may be used afterward during operation.

[0227] For example, the non-AP MLD decides to compute and use this variant universal NSTR Indication Bitmap during the association procedure when it identifies that both non-AP MLD and AP MLD support DSO and / or NPCA and / or DBE and / or HE SST modes through the exchange of corresponding Capabilities, as already mentioned above.

[0228] By reporting the new NSTR statuses as early as the association, the use of the DSO, NPCA, DBE, HE SST or the like mechanism can take place without additional signalling frame and without risks of interference between channels simultaneously used by the non-AP STA (i.e., risks that a STR pair becomes NSTR).

[0229] In a variant, the non-AP MLD may decide to compute and use this variant Universal NSTR Indication Bitmap during ML operation, in particular upon the AP MLD activating a Dynamic Subband Operation (DSO) or a Non-Primary Channel Access (NPCA) or a Dynamic Bandwidth Expansion or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism on one link of the link pair at the non-AP MLD (already described above with reference to Figure 3a). In that case, a switch back to the legacy NSTR Indication Bitmap may also be envisioned as already described above with reference to Figure 3a.

[0230] In the scenarios of Figure 3b and 3c, a non-AP MLD computes the variant Universal NSTR indication bitmap by comparing its internal and intrinsic minimum frequency gap for STR operation requirement to the current frequency gap observed within the BSSs it is operating in. The current frequency gap is computed using as references the nearest frequency edges of the maximum STA’s operating channels of any two affiliated non-AP STAs considering all the possible positions of the STA’s (initial or substitute) operating channel of an affiliated non-AP STA that may be reached through the use of Legacy and DSO / NPCA / DBE modes (and HE SST mode).

[0231] Regarding the subfield “Frequency Separation For STR / AP MLD Type Indication” of the MLD Capabilities And Operations subfield as referred in Table 9-417n of P802.1 1 be / D7.0, when transmitted by a non-AP STA affiliated with a non-AP MLD, the subfield is the Frequency Separation For STR subfield and it indicates the minimum frequency gap between the maximum STA’s operating channels of any two non-AP STAs affiliated with the non-AP MLD that is recommended by the non-AP MLD for STR operation. The frequency gap is specified as the difference between the nearest frequency edges of the maximum STA’s operating channels of any two affiliated non-AP STAs considering all the possible positions of the STA’s operating channel of an affiliated non-AP STA that may be reached through the use of Legacy and DSO / NPCA / DBE modes (and HE SST mode).

[0232] Regarding the MLD capability and operation signalling, the non-AP MLD ensures that the minimum frequency gap indicated in the Frequency Separation For STR subfield starts from the nearest frequency edges of the maximum supported channel indicated by the Supported Channel Width Set subfield in the UHR / HE Capabilities element and the Support For 320MHz in 6GHz subfield in the EHT Capabilities element and the Maximum Supported DBE Bandwidth in the UHR Operation element of any two affiliated non-AP STAs considering all the possible positions of STA’s (initial or substitute) operating channel of an affiliated non-AP STA that may be reached through the use of Legacy and DSO / NPCA / DBE modes (and HE SST mode).

[0233] Also, a non-AP MLD may set the Frequency Separation For STR subfield in the Common Info field of the Basic Multi-Link element to a nonzero value if it intends to indicate the minimum frequency gap that is recommended between the nearest frequency edges of the maximum STA’s operating channels of any two affiliated non-AP STAs considering all the possible positions of STA’s operating channel of an affiliated non-AP STA that may be reached through the use of Legacy and DSO / NPCA / DBE modes (and HE SST mode) for the non-AP MLD for STR operation; otherwise, the non-AP MLD may set the Frequency Separation For STR subfield to 0. Yet other embodiments of the present disclosure rely on information shared between the AP MLD and the non-AP MLD, in order to dynamically adjust the operations (with or without the channel switching mechanisms).

[0234] Information may be shared during the association procedure using the UHR Capabilities subfield 400 of Figure 4a and / or the DSO / NPCA / DBE Configuration element 420 of Figure 4b.

[0235] Figure 4a illustrates an exemplary format of the UHR Capabilities subfield 400 in the Common Info field of a Basic Multi-Link element according to embodiments.

[0236] The Basic Multi-Link element may be carried in a (Re)Association Request frame, a (Re)Association Response frame or a Probe Response frame during the association procedure. UHR Capabilities subfield 400 contains a number of subfields that are used to advertise UHR capabilities of the MLD described in a Basic Multi-Link element.

[0237] DSC Support subfield 401 indicates whether the MLD described in the Basic Multi-Link element supports Dynamic Subband Operation (DSO). DSO Support subfield 401 is set to 1 in a case where the MLD supports the DSO; otherwise, it is set to 0. The DSO Support subfield 401 is preferably one-bit width.

[0238] An AP MLD that supports DSO sets the DSO Support subfield 401 to 1 in the UHR Capabilities subfield 400 in the Common Info field of a Basic Multi-Link element carried in a Probe Response frame or a (Re)Association Response frame it sends to a non-AP MLD.

[0239] A non-AP MLD that supports DSO sets the DSO Support subfield 401 to 1 in the UHR Capabilities subfield 400 in the Common Info field of a Basic Multi-Link element carried in a (Re)Association Request frame it sends to an AP MLD.

[0240] NPCA Support subfield 402 indicates whether the MLD described in the Basic Multi-Link element supports Non-Primary Channel Access (NPCA) operation. NPCA Support subfield 402 is set to 1 in a case where the MLD supports the NPCA operation; otherwise, it is set to 0. The NPCA Support subfield 402 is preferably one-bit width.

[0241] An AP MLD that supports NPCA operation sets the NPCA Support subfield 402 to 1 in the UHR Capabilities subfield 400 in the Common Info field of a Basic Multi-Link element carried in a Probe Response frame or a (Re)Association Response frame it sends to a non-AP MLD.

[0242] A non-AP MLD that supports NPCA operation sets the NPCA Support subfield 402 to 1 in the UHR Capabilities subfield 400 in the Common Info field of a Basic Multi-Link element carried in a (Re)Association Request frame it sends to an AP MLD.

[0243] DBE Support subfield 404 indicates whether the MLD described in the Basic Multi-Link element supports Dynamic Bandwidth Expansion (DBE) operation. DBE Support subfield 404 is set to 1 in a case where the MLD supports the DBE operation; otherwise, it is set to 0. The DBE Support subfield 404 is preferably one-bit width.

[0244] An AP MLD that supports DBE operation sets the DBE Support subfield 404 to 1 in the UHR Capabilities subfield 400 in the Common Info field of a Basic Multi-Link element carried in a Probe Response frame or a (Re)Association Response frame it sends to a non-AP MLD. A non-AP MLD that supports DBE operation sets the DBE Support subfield 404 to 1 in the UHR Capabilities subfield 400 in the Common Info field of a Basic Multi-Link element carried in a (Re)Association Request frame it sends to an AP MLD.

[0245] Reserved subfield 403 corresponds to reserved bits not assigned. For example, the size of the Reserved subfield 403 is 5 bits.

[0246] It may be noted that additional support subfields (using any reserved bit) may be provided to signal capabilities of any other channel switching mechanism. For example, a one-bit subfield may be used to signal support of the HE SST mechanism.

[0247] Also, only one of the DSC, NPCA and DBE Support subfields may be provided when only one of the corresponding channel switching mechanisms is considered. The description below makes reference to the three mechanisms together to ease the explanations. However, the skilled person would easily adapt the teachings below to a single one or two of the three mechanisms or to any combination and sub-combination of three or more channel switching mechanisms.

[0248] Furthermore, other subfields not illustrated in Figure 4a may be contemplated in UHR Capabilities subfield 400. For example, DSO / NPCA Padding Delay subfields and DSO / NPCA Transition Delay subfields may be present in UHR Capabilities subfield 400 to indicate the delays needed by the MLD to perform a DSO / NPCA channel switching. UHR Capabilities subfield 400 may in that case have a length greater than one byte. In variants as shown below, these delays may be included in element 420 of Figure 4b.

[0249] The name “UHR Capabilities” of element 400 is a naming example and other naming could be contemplated. As example the naming “UHR MAC Capabilities” could also be used for element 400.

[0250] Figure 4b illustrates an exemplary format of the DSO / NPCA / DBE Configuration element 420, for example used in a Per-STA Profile subelement of Link Info field of Basic Multi-Link element according to embodiments. The Configuration element is named “DSO / NPCA / DBE” because the illustrated element focuses on signalling information about the DSO mechanism, the NPCA mechanism and the DBE mechanism. As mentioned above, other channel switching mechanisms may be considered in variants and / or in combination. Hence, the naming above may be changed.

[0251] Figure 4b defines the format of the DSO / NPCA / DBE Configuration element 420 in a Per- STA Profile subelement of the Link Info field of a Basic Multi-Link element carried in a Probe Response frame, in a (Re)Association Response frame or in a (Re)Association Request frame.

[0252] DSO / NPCA / DBE Configuration element 420 contains a number of fields that are used by an AP MLD and a non-AP MLD to advertise the DSO, the NPCA and the DBE configuration parameters that will be used on the link between the affiliated AP and the affiliated non-AP STA corresponding to the Per-STA Profile subelement, during DSO, NPCA and DBE operations (i.e., during TXOPs). Element ID field 421 and Element ID Extension field 423 are used to identify element 420 as being a DSO / NPCA / DBE Configuration element. For example, they could be set to value 255 and to a predefined value between 144-255, respectively.

[0253] Length field 422 indicates the number of octets forming DSO / NPCA / DBE Configuration element 420, excluding the Element ID and Length fields.

[0254] DSO / NPCA / DBE Configuration Control field 424 embeds a DSO Configuration Parameters Present subfield 427, a NPCA Configuration Parameters Present subfield 428, a DBE Configuration Parameters Present subfield 430 and a Reserved subfield 429. DSO Configuration Parameters Present subfield 427 indicates the presence of the DSO Configuration Parameters subfield 425: it is set to 1 to indicate that the DSO Configuration Parameters subfield 425 is present; otherwise, it is set to 0. The DSO Configuration Parameters Present subfield 427 is preferably one-bit width. NPCA Configuration Parameters Present subfield 428 indicates the presence of the NPCA Configuration Parameters subfield 426: it is set to 1 to indicate that the NPCA Configuration Parameters subfield 426 is present; otherwise, it is set to 0. NPCA Configuration Parameters Present subfield 428 is preferably one-bit width. DBE Configuration Parameters Present subfield 430 indicates the presence of the DBE Configuration Parameters subfield 431 : it is set to 1 to indicate that the DBE Configuration Parameters subfield 431 is present; otherwise, it is set to 0. DBE Configuration Parameters Present subfield 430 is preferably one-bit width. Reserved subfield 429 corresponds to reserved bits not assigned. For example, the size of the Reserved subfield 429 is 5 bits.

[0255] DSO Configuration Parameters field 425 embeds several subfields (not shown) indicating the various parameters needed to perform DSO between the affiliated AP and the affiliated non- AP STA. Any configuration to convey the parameters needed may be used. For example, when transmitted by an AP MLD, the DSO Configuration Parameters field 425 embeds a DSO Channels Positions subfield to indicate a substitute channel for DSO, i.e. , where the initial STA’s operating bandwidth of the affiliated non-AP STA will be translated during a DSO TXOP. As another example, when transmitted by a non-AP MLD, the DSO Configuration Parameters field 425 embeds a DSO Padding Delay subfield and DSO Transition Delay subfield indicating the delays needed by the affiliated non-AP STA to perform a DSO channel switching on the link corresponding to the Per-STA Profile subelement. The length of DSO Configuration Parameters field 425 is variable.

[0256] NPCA Configuration Parameters field 426 embeds several subfields (not shown) indicating the various parameters needed to perform NPCA operation between the affiliated AP and the affiliated non-AP STA. Any configuration to convey the parameters needed may be used. For example, when transmitted by an AP MLD, the NPCA Configuration Parameters field 426 embeds an Anchor Channel or NPCA Primary Channel subfield to indicate a substitute channel position for NPCA operation, i.e., the secondary (anchor) channel position where the affiliated AP and the affiliated non-AP STA will have to switch, upon detection of a busy primary channel, to perform a NPCA TXOP. As another example, when transmitted by an AP MLD or a non-AP MLD, the NPCA Configuration Parameters field 426 embeds a NPCA Padding Delay subfield and NPCA Transition Delay subfield indicating the delays needed by the affiliated AP or affiliated non-AP STA to perform a NPCA channel switching on the link corresponding to the Per-STA Profile subelement. The length of NPCA Configuration Parameters field 426 is variable.

[0257] DBE Configuration Parameters field 431 embeds several subfields (not shown) indicating the various parameters needed to perform DBE operation between the affiliated AP and the affiliated non-AP STA. Any configuration to convey the parameters needed may be used. For example, when transmitted by an AP MLD, the DBE Configuration Parameters field 431 embeds the DBE Bandwidth subfield to indicate the maximum bandwidth supported by the affiliated AP during DBE operation. As another example, when transmitted by a non-AP MLD, the DBE Configuration Parameters field 431 embeds the Maximum Supported DBE Bandwidth subfield to indicate the maximum bandwidth supported by the affiliated non-AP STA during DBE operation. As yet another example, when transmitted by an AP MLD or a non-AP MLD, the DBE Configuration Parameters field 431 embeds a DBE Switch Delay subfield and DBE Switch Back Delay subfield indicating the delays needed by the affiliated AP or affiliated non-AP STA to perform a DBE channel switching on the link corresponding to the Per-STA Profile subelement. The length of DBE Configuration Parameters field 431 is variable.

[0258] During the association procedure, the AP MLD can send the DSO / NPCA / DBE Configuration element 420 in one or several Per-STA Profile subelement(s) of the Link Info field of a Basic Multi-Link element carried in a Probe Response frame or in a (Re)Association Response frame to advertise the DSC, the NPCA and the DBE configuration parameters that will be used on one or several link(s) by corresponding affiliated AP(s) during DSC, NPCA and DBE TXOPs.

[0259] Similarly, during the association procedure, the non-AP MLD can send the DSO / NPCA / DBE Configuration element 420 in one or several Per-STA Profile subelement(s) of the Link Info field of a Basic Multi-Link element carried in an (Re)Association Request frame to advertise the DSO, the NPCA and the DBE configuration parameters that will be used on one or several link(s) by corresponding affiliated non-AP STA(s) during DSO, NPCA and DBE TXOPs.

[0260] A non-AP MLD may respond to a DSO / NPCA / DBE Configuration element 420 sent by an AP MLD, with the DSO / NPCA / DBE Configuration element 420 in one or several Per-STA Profile subelement(s) of the Link Info field of a Basic Multi-Link element carried in another (Re)Association Request frame to try to negotiate the DSO / NPCA / DBE configurations (or more generally the configuration of the channel switching mechanisms), for example the substitute channel to be used.

[0261] The name “DSO / NPCA / DBE Configuration element” of the element 420 is a naming example and other naming could be contemplated. As example the naming “DSO / NPCA / DBE Operation element” or “UHR Operation element” could also be used for the element 420. Also, the order of the fields as shown in Figure 4b may be changed. Figure 4c illustrates the format of the MLD Capabilities And Operations subfield 440 in the Common Info field of a Basic Multi-Link element as defined in P802.11 be / D7.0. MLD Capabilities And Operations subfield 440 is made of sixteen bits (two bytes).

[0262] Frequency Separation For STR / AP MLD Type Indication subfield 441 , made of bits B7- B11 , signals a Frequency Separation For STR when sent by a non-AP MLD and signals an AP MLD Type Indication when sent by an AP MLD. Frequency Separation For STR of a non-AP MLD indicates the minimum frequency gap between any two links that is recommended by the non-AP MLD for STR operation. In practice, when set to a nonzero value n, the Frequency Separation For STR subfield indicates that the STR frequency gap is (n-1)*80MHz. The value 0 indicates no frequency separation information is provided.

[0263] The other fields are of less importance. A description thereof is available in P802.11 be / D7.0.

[0264] The Frequency Separation For STR provided by the non-AP MLDs may be used by the AP MLD to efficiently organize the communication in its BSS, in particular to select the associated non-AP MLDs concerned by the usage of the channel switching mechanisms (DSO and / or NPCA and / or DBE and / or HE SST), and / or to select channel switching mechanism parameters’ settings (such as the position of the substitute channel, and so on.). An aim of these adjusted selections includes avoiding, as far as possible, that a STR link pair become a NSTR link pair through the usage of the channel switching mechanisms.

[0265] In embodiments of the disclosure, a rule can therefore be provided for an AP MLD for the usage of the channel switching mechanisms considering the NSTR constraints of the non-AP MLDs.

[0266] To that end, the AP MLD receives, from one or more non-AP MLDs, a minimum frequency gap value for Simultaneous Transmit Receive (STR) operation.

[0267] The AP MLD may select, based on the minimum frequency gap value or values received, a non-AP MLD to trigger a communication mechanism (requiring switching of a station affiliated with the non-AP MLD from an initial STA’s operating channel to a substitute channel) at the non- AP MLD.

[0268] In a variant or in combination, the AP MLD may select, based on the minimum frequency gap values received, substitute channel parameters to trigger the communication mechanism at the non-AP MLD.

[0269] In this scenario, an AP MLD should take into account the information provided by associated non-AP MLDs in the Frequency Separation For STR subfield in their transmitted MultiLink elements when the AP MLD intends to use the DSO mode and / or the NCPA mode and / or the DBE mode (and / or the HE SST mode) in the BSS of at least one of its affiliated APs.

[0270] To allow the AP MLD to apply the above rule, the information in the Frequency Separation For STR subfield is required from multi-radio non-AP MLDs subject to NSTR constraints. In other words, a multi-radio non-AP MLD sets the Frequency Separation For STR subfield in the Common Info field of the Basic Multi-Link element to a nonzero value to indicate the minimum frequency gap that is recommended between two links for the non-AP MLD for STR operation; a singleradio non-AP MLD or a multi-radios non-AP MLD not subject to NSTR constraints sets the Frequency Separation For STR subfield to 0.

[0271] Figure 5 illustrates, using flowchart 500, steps at an AP MLD to apply the above rule.

[0272] At step 502, the AP MLD gathers DSO / NPCA / DBE / HE SST Capabilities from its associated non-AP MLDs, and gathers Frequency Separation For STR indications from the DSO / NPCA / DBE / HE SST-capable non-AP MLDs.

[0273] The AP MLD retrieves this information from UHR Capabilities subfield 400 and MLD Capabilities And Operations subfield 440 as received from the non-AP MLDs, e.g., in (Re)Association Request frames.

[0274] At step 504, the AP MLD selects non-AP MLDs in which to activate a channel switching mechanism, based the gathered capabilities and Frequency Separation For STR indications.

[0275] For example, the AP MLD may only select non-AP MLDs that are DSO or NPCA or DBE or HE SST capable.

[0276] Also, the AP MLD may select non-AP MLDs having no NSTR constraints changing with an activation of a channel switching mechanism. For example, the AP MLD determines whether the Frequency Separation For STR is compatible with any substitute channel available for a channel switching mechanism, in order not to change the NSTR constraint of a link pair when activating the channel switching mechanism. The AP MLD may for example use the calculations of Figure 2 with the substitute channel rather than the conventional operating channel, or of Figure 3a, 3c or 3b, 3d to decide whether there are risks of NSTR constraint changes.

[0277] At step 506, the AP MLD selects appropriate DSO / NPCA / DBE / HE SST parameters for the selected non-AP MLDs. For example, the AP MLD sets (selects) the substitute channel (e.g., from multiple substitute channel candidates) to be used to avoid change of the NSTR constraint of a link pair at the non-AP MLD. Other parameters, such a transmission power and / or MCS can be adjusted too.

[0278] Other embodiments of the present disclosure are now described with reference to Figures 6 to 8. In these embodiments, the NSTR statuses of the link pairs are updated when needed, i.e., when the channel switching mechanism is activated / enabled by the AP MLD.

[0279] Figure 6 illustrates an exemplary frame exchange sequence between an AP MLD and a non-AP MLD.

[0280] Figure 7 illustrates, using flowchart 700, steps performed by the AP MLD. In particular, the AP MLD receives, from at least one non-AP MLD, NSTR statuses of pairs of links setup between the AP MLD and the non-AP MLD, wherein an NSTR status of a link pair is based on frequency edges of only STA’s operating channels of non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair - i.e., it is a legacy NSTR status; the AP MLD activates a channel switching mechanism (DSO or NPCA or DBE or HE SST) on a link of the link pair at the non-AP MLD; and responsive to the activation, the AP MLD receives updated NSTR statuses from the non-AP MLD, wherein at least one updated NSTR status is determined based on a frequency edge different from a frequency edge of the STA’s operating channels of the affiliated non-AP STAs - e.g., it is a universal NSTR status as described above.

[0281] Figure 8 illustrates, using flowchart 800, steps performed by the non-AP MLD. In particular, the non-AP MLD shares, with the AP MLD, (legacy) NSTR statuses of pairs of links setup with the AP MLD; and upon the AP MLD activating a channel switching mechanism (DSO or NPCA or DBE or HE SST) on a link of the link pair at the non-AP MLD, the non-AP MLD updates the shared NSTR statuses, wherein at least one updated NSTR status is determined based on a frequency edge different from a frequency edge of the STA’s operating channels of the affiliated non-AP STAs - e.g., it is a universal NSTR status as described above.

[0282] In embodiments described below, during the association procedure, the non-AP MLD computes the legacy NSTR Indication Bitmaps; and during ML operations, the AP MLD activates any DSO / NPCA / DBE mechanism, using for example the rules defined above with reference to Figure 5; next, the non-AP MLD updates its NSTR Indication Bitmaps into the above universal NSTR Indication Bitmaps (whatever the variant of Figure 3a, 3c or 3b, 3d). Instead of updating the bitmaps, the non-AP MLD may merely refuse the activation of the DSO / NCPA / DBE mechanism if it impacts its NSTR Indication Bitmap or for other reasons.

[0283] In embodiments, upon announcement of DSO, NPCA or DBE mode enablement (activation) on a link by an affiliated AP of an AP MLD, a non-AP MLD that supports the mode on the corresponding link may send a frame carrying a Reconfiguration ML element through its affiliated non-AP STA associated with the affiliated AP in order to provide the updated NSTR statuses of the link pairs (i.e., the updated [universal] NSTR Indication Bitmaps) involving the link where the mode is activated. The frame carrying the Reconfiguration ML element could be an UHR Link Reconfiguration frame or an MLO Update Request frame.

[0284] Similarly, upon announcement of DSO, NPCA or DBE mode disablement (deactivation) on a link by an affiliated AP of an AP MLD, a non-AP MLD that supports the mode on the corresponding link may send a frame carrying a Reconfiguration ML element through its affiliated non-AP STA associated with the affiliated AP in order to provide the updated NSTR statuses of the link pairs (i.e., the updated [legacy] NSTR Indication Bitmaps) involving the link where the mode is deactivated. The frame carrying the Reconfiguration ML element could be an UHR Link Reconfiguration frame or an MLO Update Request frame.

[0285] At step 701 , the AP MLD starts a Discovery and Association procedure in order to be discovered and to be associated with a non-AP MLD. At step 801 , the non-AP MLD starts a Discovery and Association procedure in order to discover and to associate with the AP MLD. As example, the AP MLD and the non-AP MLD start the Discovery and Association sequence through the frame exchanges 601 and 602 of Figure 6.

[0286] In embodiments, the non-AP MLD computes the Legacy NSTR Indication Bitmap during this Discovery and Association step.

[0287] Figure 6 illustrates a frame exchange sequence 600 between AP MLD 110 and non-AP MLD 120 (of Figure 1) on Link#0 between their affiliated AP1 1 11 and affiliated non-AP STA A1 121 , and on Link#1 between their affiliated AP2 112 and affiliated non-AP STA A2 122, respectively.

[0288] The frame exchange sequence 600 starts on Link#0 with the discovery phase where ML Probe Request and ML Probe response frames 601 are exchanged between affiliated non-AP STA A1 121 and affiliated AP1 111 . Next, the sequence continues with the association procedure phase where ML Association Request and ML Association Response frames 602 are exchanged between affiliated non-AP STA A1 121 and affiliated AP1 111 . Through this frame exchange 602, among other things, AP MLD 110 and non-AP MLD 111 indicate their support to the channel switching mechanisms (DSO, NPCA, DBE, HE SST) through the UHR Capabilities subfield 400 and AP MLD 110 may indicate, for each of its affiliated APs (i.e., for each link), the Configuration Parameters 425 / 426 / 431 to be used during the TXOPs under the channel switching mechanism.

[0289] Also, during the association procedure, non-AP MLD 120 may compute and signal the legacy NSTR Indication Bitmap (Figure 2) of each of its affiliated non-AP STAs, if at least one link pair is identified as NSTR. At this stage, non-AP MLD 120 uses the legacy way to compute the NSTR Indication Bitmap as no channel switching mechanism is yet enabled / activated. For example here, the single link pair in the scenario, pair <0,1 >, being not identified as NSTR by non-AP MLD 120, the signalling of the legacy NSTR Indication bitmap is not performed by non- AP MLD 120. Of course, a higher number of link pairs may be signalled, when the MLDs sets up more than two links between them.

[0290] The legacy NSTR Indication Bitmap for link T is provided in the Per-STA Profile having Link ID set to i, in the case where at least one bit Bj (with j i) is 1 (at least one NSTR link pair involving link i). Hence, as soon as one link pair is NSTR, multiple legacy NSTR Indication Bitmaps are conveyed in the Basic Multi-Link element. Figure 4d illustrates the format of a Per- STA Profile according to P802.11 be / D7.0.

[0291] Per-STA Profile 460 includes STA Control field 461 in which Link ID subfield 462 specifies the link (hence AP and non-AP STA) concerned by the Per-STA Profile, NSTR Link Pair Present subfield 463 indicates whether STA Info field 470 includes a NSTR Indication Bitmap 471 and NSTR Bitmap Size subfield 464 indicates the size of the NSTR Indication Bitmap 471 when present. NSTR Indication Bitmap 471 of STA Info field 470 includes the legacy NSTR Indication Bitmap for the link specified in Link ID subfield 462.

[0292] The Basic Multi-Link element having the computed legacy NSTR Indication Bitmaps may be included in the (Re)Association Request frame 602 from the non-AP STA.

[0293] Following the provision of the legacy NSTR Indication Bitmaps during the association procedure, the MLDs may operate using these legacy NSTR Indication Bitmaps.

[0294] At step 702, the AP MLD starts the usage of the legacy NSTR Indication Bitmap received from the non-AP MLD for the management of its legacy Multi-Link Operation with the non-AP MLD. At step 802, the non-AP MLD starts the usage of the computed legacy NSTR Indication Bitmaps for its legacy Multi-Link Operation with the AP MLD. As an example, the AP MLD and non-AP MLD use the legacy NSTR Indication Bitmaps during the usage period 630 of Figure 6. Legacy frame exchanges may take place.

[0295] At step 703, the AP MLD may decide to enable / activate a channel switching mechanism, such as the DSO, NPCA or DBE mechanism, on one or more links at the non-AP MLD. As an example, the AP MLD enables the DSO mode with non-AP MLD through an exchange of frames 603, 604, referred to as Operating Mode Notification frame or DSO / NPCA / DBE Operating Mode Notification frame to be more specific to the DSO, NPCA and DBE mechanisms. Of course, the AP MLD may apply the rule described above with reference to Figure 5 to decide on the opportunity to activate the channel switching mechanism at the non-AP MLD.

[0296] With reference to Figure 6, AP MLD 110 decides to enable the DSO mechanism (or any other channel switching mechanism) with non-AP MLD 120 on both Link#0 and Link #1 . To that end, AP MLD 110 sends DSO / NPCA / DBE OM Notification frame 603 through its affiliated AP1 111 to non-AP MLD 120 through its affiliated non-AP STA A1 121.

[0297] Figures 9a and 9b illustrate an exemplary frame format of the (DSO / NPCA / DBE) Operating Mode (OM) notification frame according to embodiments. The DSO / NPCA / DBE Operating Mode Notification frame is used by an AP MLD to enable or disable a channel switching mechanism, such as the DSO, NPCA or DBE mechanism, in one or several link(s). The DSO / NPCA / DBE Operating Mode Notification frame is used by a non-AP MLD to acknowledge / non-acknowledge the enablement / activation of the channel switching mechanism in one or several link(s) and to acknowledge the disablement / deactivation of the channel switching mechanism in one or several link(s).

[0298] The DSO / NPCA / DBE Operating Mode Notification frame is used to indicate that an AP MLD with which the transmitting AP STA is affiliated is changing the DSO, NPCA or DBE operation(s) on one or several link(s) and is used by a non-AP MLD as a response, transmitted by a non-AP STA affiliated with the non-AP MLD, to the received DSO / NPCA / DBE Operating Mode Notification frame from the soliciting AP STA affiliated with the AP MLD.

[0299] The DSO / NPCA / DBE Operating Mode Notification frame is a Protected UHR Action frame which can be sent using either Unicast or Multicast or Broadcast addressing.

[0300] Figure 9a illustrates the Action field format of the DSO / NPCA / DBE Operating Mode notification frame according to embodiments.

[0301] The Action field 900 of the DSO / NPCA / DBE Operation Mode Notification frame includes:

[0302] - Category field 901 set to a value corresponding to the category Protected UHR. For example, Category field 901 is set to a predefined value between 40-125.

[0303] - Protected UHR Action field 902 set to a value corresponding to the DSO / NPCA / DBE Operating Mode Notification. For example, Protected Action field is set to a predefined value between 0-255.

[0304] - Dialog Token field 903 set by an AP MLD to a nonzero value chosen by the AP MLD and set by a non-AP MLD to the value copied from the corresponding received DSO / NPCA / DBE Operating Mode Notification frame. Dialog Token field 903 thus helps the MLDs to monitor the evolution of the same operations.

[0305] - DSO / NPCA / DBE Operating Mode Control field 910 described below with reference to Figure 9b.

[0306] - optional DSO / NPCA / DBE Configuration element 420 already described above with reference to Figure 4b. During operation, an AP MLD can for example send one or several DSO / NPCA / DBE Configuration element(s) 420 carried in the DSO / NPCA / DBE Operating Mode Notification frame to update the DSO and / or the NPCA and / or the DBE configuration parameters that will be used on one or several link(s) by corresponding affiliated AP(s) and affiliated non-AP STA(s), during DSO, NPCA and DBE TXOPs.

[0307] Figure 9b illustrates the DSO / NPCA / DBE Operating Mode Control field format of the DSO / NCPA / DBE Operating Mode notification frame according to embodiments.

[0308] DSO / NPCA / DBE Operating Mode Control field 910 includes DSO Mode subfield 911 , NPCA Mode subfield 912, DBE Mode subfield 918, DSO / NPCA / DBE Link Bitmap subfield 913, Target Beacon Transmission Time (TBTT) Count subfield 914, DSO / NPCA / DBE Configuration Element Presence Bitmap subfield 915, NSTR Status Update Required subfield 916 and optional Reserved subfield 917.

[0309] DSO Mode subfield 911 indicates whether the DSO / NPCA / DBE OM notification frame is dedicated to DSO, in particular is used to enable (activate) or disable (deactivate) the DSO mechanism (or mode) on one or several links. DSO Mode subfield 91 1 is set to 1 to indicate that the DSO / NPCA / DBE OM notification frame is dedicated to the DSO mechanism. Otherwise, DSO Mode subfield 91 1 is set to 0. The DSO Mode subfield 911 is preferably one-bit width. If DSO mode subfield 91 1 is set to 1 , NPCA Mode subfield 912 and DBE Mode subfield 918 are set to 0.

[0310] An MLD sets DSO Mode subfield 911 to 1 in the DSO / NPCA / DBE OM notification frame it transmits only when the MLD has declared support of the DSO mode in the UHR Capabilities subfield 400 (Figure 4a) during the association procedure. A non-AP MLD with dot1 1 UHRDSOOptionActivated equal to true sets DSO Mode subfield 911 to the same value obtained from the DSO Mode subfield of a received DSO / NPCA / DBE OM notification frame when responding to that frame.

[0311] NPCA Mode subfield 912 indicates whether the DSO / NPCA / DBE OM notification frame is dedicated to NPCA, in particular is used to enable or disable the NPCA mechanism (or mode) on one or several links. NPCA Mode subfield 912 is set to 1 to indicate that the DSO / NPCA / DBE OM notification frame is dedicated to the NPCA mechanism. Otherwise, NPCA Mode subfield 912 is set to 0. NPCA Mode subfield 912 is preferably one-bit width. If NPCA mode subfield 912 is set to 1 , DSO Mode subfield 911 and DBE Mode subfield 918 are set to 0.

[0312] An MLD sets NPCA Mode subfield 912 to 1 in the DSO / NPCA / DBE OM notification frame it transmits only when the MLD has declared support of the NPCA mode in the UHR Capabilities subfield 400 during the association procedure. A non-AP MLD with dot1 1 UHRNPCAOptionActivated equal to true sets NPCA Mode subfield 912 to the same value obtained from the NPCA Mode subfield of a received DSO / NPCA / DBE OM notification frame when responding to that frame.

[0313] DBE Mode subfield 918 indicates whether the DSO / NPCA / DBE OM notification frame is dedicated to DBE, in particular is used to enable or disable the DBE mechanism (or mode) on one or several links. DBE Mode subfield 918 is set to 1 to indicate that the DSO / NPCA / DBE OM notification frame is dedicated to the DBE mechanism. Otherwise, DBE Mode subfield 918 is set to 0. DBE Mode subfield 918 is preferably one-bit width. If DBE mode subfield 918 is set to 1 , DSO Mode subfield 911 and NPCA Mode subfield 912 are set to 0.

[0314] An MLD sets DBE Mode subfield 918 to 1 in the DSO / NPCA / DBE OM notification frame it transmits only when the MLD has declared support of the DBE mode in the UHR Capabilities subfield 400 during the association procedure. A non-AP MLD with dot1 1 UHRDBEOptionActivated equal to true sets DBE Mode subfield 918 to the same value obtained from the DBE Mode subfield of a received DSO / NPCA / DBE OM notification frame when responding to that frame.

[0315] DSO / NPCA / DBE Link Bitmap subfield 913 indicates the enabled (activated) link(s) that is(are) used for DSO or NPCA or DBE operation (more generally for the activated channel switching mechanism). The presence of bits enabled in the bitmap allows to know, compared to a previous bitmap, on which links the DSO or NPCA or DBE mechanism is activated (bit changed from 0 to 1 between the two bitmaps) or deactivated (bit changed from 1 to 0 between the two bitmaps). When DSO Mode subfield 911 is set to 1 , DSO / NPCA / DBE Link Bitmap subfield 913 corresponds to the DSO Link Bitmap. When NPCA Mode subfield 912 is set to 1 , DSO / NPCA / DBE Link Bitmap subfield 913 corresponds to the NPCA Link Bitmap. When DBE Mode subfield 918 is set to 1 , DSO / NPCA / DBE Link Bitmap subfield 913 corresponds to the DBE Link Bitmap. The bit Bi having position i in the DSO / NPCA / DBE Link Bitmap subfield 913 corresponds to the link with the Link ID subfield equal to i and Bi is set to 1 to indicate that the DSO or NPCA or DBE mode is enabled on that link; otherwise, bit Bi is set to 0 to indicate that the DSO or NPCA or DBE mode is disabled on that link. For example, the width of DSO / NPCA / DBE Link Bitmap subfield 913 is 8 bits.

[0316] A non-AP MLD with dot11 UHRDSOOptionActivated equal to true sets the DSO / NPCA / DBE Link Bitmap subfield 913 to the same value obtained from the DSO / NPCA / DBE Link Bitmap subfield of the received DSO / NPCA / DBE OM Notification frame.

[0317] In a variant embodiment, a non-AP MLD with dot11 UHRDSOOptionActivated equal to true sets the DSO / NPCA / DBE Link Bitmap subfield to a different value than the one obtained from the DSO / NPCA / DBE Link Bitmap subfield of the received DSO / NPCA / DBE OM Notification frame. This may be used, for example, to refuse the enablement of the channel switching mechanism (DSO or NPCA or DBE) on a link i: the non-AP MLD may set bit Bi to 0 in the DSO / NPCA / DBE Link Bitmap subfield of the DSO / NPCA / DBE OM notification frame it transmits as a response, when Bi was set to 1 in the DSO / NPCA / DBE Link Bitmap subfield of the received DSO / NPCA / DBE OM Notification frame. Target Beacon Transmission Time (TBTT) Count subfield 914 indicates the number of Beacon frames after which the enablement or disablement of the DSO or NPCA or DBE mode will be effective. The TBTT Count subfield 914 is for example eight-bit width. When the DSO / NPCA / DBE CM notification frame is transmitted by a non-AP MLD, this TBTT Count subfield 914 is not present.

[0318] DSO / NPCA / DBE Configuration Element Presence Bitmap subfield 915 indicates, for each link, whether a DSO / NPCA / DBE Configuration element 420 is present or not in the transmitted DSO / NPCA / DBE OM notification frame (as shown in Figure 9a). The order of the DSO / NPCA / DBE Configuration elements 420 (if multiple) may be the (increasing) order of their respective Link IDs.

[0319] The bit Bi at position i in DSO / NPCA / DBE Configuration Element Presence Bitmap subfield 915 corresponds to the link with the Link ID subfield equal to i and Bi is set to 1 to indicate that one DSO / NPCA / DBE Configuration element 420 is present for that link; otherwise, the bit Bi is set to 0 to indicate that no DSO / NPCA / DBE Configuration element 420 is present for that link. For example, the width of DSO / NPCA / DBE Configuration Element Presence Bitmap subfield 915 is 8 bits (one byte). It may be 16 bits (two bytes) in a case where more than eight links are set up.

[0320] NSTR Status Update Required subfield 916 indicates, for a non-AP MLD, whether the enablement or disablement of the DSO or NPCA or DBE mode signalled in the DSO / NPCA / DBE OM notification frame received from an AP MLD requires an update of the NSTR Indication Bitmaps or not. The NSTR Status Update Required subfield 916 is set to 1 to indicate that an update of the NSTR Indication Bitmaps is required. Otherwise, the NSTR Status Update Required subfield 916 is set to 0. When the DSO / NPCA / DBE OM notification frame is transmitted by an AP MLD, NSTR Status Update Required subfield 916 is not present.

[0321] Reserved subfield 917 corresponds to reserved bits not assigned. For example, the size of Reserved subfield 917 is 4 bits.

[0322] The order of the fields shown in Figure 9b may be changed.

[0323] Back to Figure 6, AP MLD 110 activates the DSO mechanism (or any other channel switching mechanism) by sending DSO / NPCA / DBE OM notification frame 603.

[0324] For example, in DSO / NCPA / DBE Notification frame 603, DSO Mode subfield 911 is set to 1 , DSO Link Bitmap subfield 913 is set to xO3(Hex), TBTT count subfield 914 is set to xOA(Hex) and DSO Configuration Element Presence Bitmap subfield 915 may be set to xO3(Hex) to indicate the presence of one DSO / NPCA / DBE Configuration element 420 for each of links #0 and #1 . NPCA Mode subfield 912 and DBE Mode subfield 918 are set to 0.

[0325] At step 803 (Figure 8), upon receiving a frame from the AP MLD, the non-AP MLD checks whether the AP MLD enables the DSO or NPCA or DBE mode, by checking the values of DSO Mode subfield 911 , NPCA Mode subfield 912 and DBE Mode subfield 918. If yes, the algorithm goes to step 804. If no, the algorithm loops to step 802.

[0326] At optional step 804, the non-AP MLD processes DSO / NPCA / DBE OM notification frame 603 received from the AP MLD in order to determine whether to accept or not the DSO or NPCA or DBE mode enablement. If yes, the algorithm goes to step 807. If no, the algorithm goes to step 805.

[0327] At optional step 805, the non-AP MLD sends a DSO / NPCA / DBE enablement response frame to the AP MLD to indicate a DSO / NPCA / DBE enablement refusal. As an example, the non- AP MLD sends frame 604 to the AP MLD to indicate its refusal.

[0328] At optional step 806, the non-AP MLD decides to continue using the legacy NSTR Indication Bitmaps for its legacy Multi-Link Operation with the AP MLD.

[0329] Multiple criteria may be implemented at the non-AP MLD to decide whether to accept or refuse a proposed DSO or NPCA or DBE activation. For example, the non-AP MLD may consider whether the activation modifies too much its NSTR constraints, e.g., modify a NSTR status of a link pair involving a link over which the non-AP MLD is already communicating.

[0330] In embodiments, the refusal procedure therefore first includes by the non-AP MLD the sharing, with the AP MLD, of (legacy) NSTR statuses of pairs of links setup with the AP MLD, wherein an NSTR status of a link pair is based on frequency edges of only STA’s operating channels of non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair; and then, upon receiving from the AP MLD a frame to activate a Dynamic Subband Operation (DSO) or a Non-Primary Channel Access (NPCA) or Dynamic Bandwidth Expansion (DBE) or a High Efficiency Subchannel Selective Transmission (HE SST) at the non-AP MLD, the decision to accept or refuse the activation based on whether the activation of the DSO or NPCA or DBE or HE SST modifies or not at least one (or more) NSTR status of a link pair. The non-AP MLD may then send to the AP MLD a frame 604 reporting the decision.

[0331] At the AP MLD side, at optional step 704, the AP MLD checks whether the DSO or NPCA or DBE mode enablement is accepted by the non-AP MLD, by reading the received DSO / NPCA / DBE enablement response frame. If yes, the algorithm goes to step 706. If no, the algorithm goes to step 705.

[0332] At optional step 705, the AP MLD decides to continue using the legacy NSTR Indication Bitmaps for its legacy Multi-Link Operation with the non-AP MLD, as the non-AP MLD does at step 806.

[0333] Turning now to the case where the non-AP MLD accepts the mechanism activation, at step 807, the non-AP MLD processes the DSO or NPCA or DBE mode enablement frame 603 received from the AP MLD in order to check whether an update of its NSTR Indication Bitmaps is required due to the DSO or NPCA or DBE mode enablement. For example, an update is required as soon as one link pair changes its NSTR status. If yes at test 807, the algorithm goes to step 810. If no, the algorithm goes to step 808. In both cases, the non-AP MLD responses to the AP MLD with a responding frame, here DSO / NPCA / DBE OM notification frame 604.

[0334] Furthermore, at step 807, the non-AP MLD may obtain or save the TBTT count 914 to trigger the channel switching to the substitute channel (either predefined or indicated in the corresponding DSO / NPCA / DBE Configuration element 420 of frame 603 as exchanged). In other words, the non-AP MLD receives, from the AP MLD, a frame 603 to activate the DSO or NPCA or DBE or HE SST mechanism, wherein the frame to activate includes time information 914 about when the mechanism and any updated NSTR statuses (bitmaps), if any, enter into force. The time information 914 is a number of Target Beacon Transmission Times (TBTT).

[0335] At step 808, the non-AP MLD sends DSO / NPCA / DBE enablement response frame 604 to the AP MLD to acknowledge the enablement of the DSO or NPCA or DBE mode. NSTR Status Update Required subfield 916 is set to 0 to indicate the NSTR Indication Bitmaps do not change.

[0336] At step 809, the non-AP MLD decides to continue using the current, i.e., legacy, NSTR Indication Bitmaps for both its legacy and UHR Multi-Link Operation with the AP MLD.

[0337] In case of bitmap update, at step 810, the non-AP MLD sends DSO / NPCA / DBE enablement response frame 604 to the AP MLD to acknowledge the enablement of the DSO or NPCA or DBE mode and to indicate that an update of the NSTR Indication Bitmaps is required by setting NSTR Status Update Required subfield 916 to 1 .

[0338] In other words, the non-AP MLD, responsive to receiving, from the AP MLD, a frame 603 to activate the DSO or NPCA or DBE or HE SST mechanism, sends to the AP MLD a frame 604 to acknowledge the activation, wherein the frame to acknowledge includes a signalling 916 that an update of the shared NSTR statuses (bitmaps) by the non-AP STA is needed.

[0339] Back to Figure 6, after receiving and processing DSO / NPCA / DBE OM notification frame

[0340] 603, non-AP MLD 120 sends DSO / NPCA / DBE OM notification frame response 604 through its affiliated non-AP STA A1 121 to AP MLD 110 through its affiliated AP1 1 11 . In the scenario here, link pair <0,1 > being now identified as NSTR by the non-AP MLD 120 due to the DSO enablement, non-AP MLD 120 has to update its NSTR Indication Bitmaps and signals the update requirement to the AP MLD.

[0341] In an embodiment, the non-AP MLD 120 indicates in response frame 604 that it acknowledges the enablement of the DSO Mode on Link#0 and Link#1 and that it needs to update its NSTR Indication Bitmap. For that purpose, in DSO / NCPA / DBE Notification frame response

[0342] 604, DSO Mode subfield 911 is set to 1 , DSO Link Bitmap subfield 913 is set to xO3(Hex) and NSTR Status Update Required subfield 916 is set to 1 .

[0343] In some embodiments not illustrated, the non-AP MLD 120 may indicate in the response frame 604 that it acknowledges the enablement of the DSO Mode on Link#0, but refuses the enablement of the DSO mode on Link#1 , and that it needs to update its NSTR Indication Bitmaps. For that purpose, in the DSO / NCPA / DBE Notification frame response 604, DSO Mode subfield 911 may be set to 1 , DSO Link Bitmap subfield 913 set to x01 (Hex) to refuse DSO enablement on Link#1 while accepting DSO enablement on Link#0, and NSTR Status Update Required subfield 916 set to 1 . A non-AP MLD may refuse the enablement of the DSO mode on a specific Link for several reasons such as power saving constraints (switch / switch back to different channels may be costly in term of power), NSTR constraints (a non-AP MLD may want to avoid a link pair to become NSTR), and so on. Still in case of bitmap update, at step 811 , the non-AP MLD computes its updated NSTR Indication Bitmap for each of its affiliated non-AP STAs. They may be universal NSTR Indication Bitmaps as explained above.

[0344] With reference to Figures 3a and 3c, the updated NSTR status of a link pair is determined by comparing a frequency difference between the nearest frequency edges of AP’s operating channels of two affiliated APs of the AP MLD corresponding to the links of the link pair with a minimum frequency gap value specific to the non-AP MLD. More generally, the updated NSTR status of a link pair is determined based on a frequency edge of an AP’s operating channel of an affiliated AP of the AP MLD corresponding to the link on which the DSO or NPCA or DBE or HE SST is activated.

[0345] With reference to Figures 3b and 3d, the updated NSTR status of a link pair is determined by comparing a frequency difference with a minimum frequency gap value specific to the non-AP MLD, the frequency difference being calculated between the nearest frequency edge of channels comprising an initial STA’s operating channel of an affiliated non-AP STA of the non-AP MLD that corresponds to the link on which the DSO or NPCA or DBE or HE SST is activated and a substitute channel of the affiliated non-AP STA to operate DSO or NPCA or DBE or HE SST on that link, to a frequency edge of the other link of the link pair.

[0346] In embodiments, the updated NSTR Indication Bitmaps may be defined from the substitute channels (secondary or anchor channels) only when existing. In that case, the updated NSTR status of a link pair is determined by comparing a frequency difference with a minimum frequency gap value specific to the non-AP MLD, the frequency difference being calculated between the nearest frequency edge of a substitute channel of an affiliated non-AP STA of the non-AP STA to operate DSO or NPCA or DBE or HE SST on one of the links to a frequency edge of the other link.

[0347] More generally, the updated NSTR status of a link pair may be determined based on a frequency edge of a substitute channel to operate DSO or NPCA or DBE or HE SST on the link on which the DSO or NPCA or DBE HE SST is activated.

[0348] At step 812, the non-AP MLD sends the updated NSTR Indication Bitmaps to the AP MLD. As an example, the non-AP sends the updated Universal NSTR Indication Bitmaps using frame 605. Frame 605 may be a legacy Multi-Link Operation (MLO) Update Request frame including a Reconfiguration Multi-Link element (with the Reconfiguration Operation Type subfield set to 4 to indicate a NSTR Status Update) that conveys the updated NSTR Indication Bitmaps. Note that the presence of each NSTR Indication Bitmap in each Per-STA Profile sub-element in Link Info field of the Reconfiguration Multi-Link element is indicated through a dedicated NSTR Indication Bitmap Present subfield in the STA Control field of the corresponding Per-STA Profile sub-element. The Reconfiguration Multi-Link element is sent through its affiliated non-AP STA1 121 to AP MLD 110 through its affiliated AP1 111.

[0349] More generally, frame 605 may be any other Multi-Link frame (hence not limited to MLO Update Request frame) including a Reconfiguration Multi-Link element (with the Reconfiguration Operation Type subfield set to 4 to indicate a NSTR Status Update or set to any other value) that conveys the updated NSTR Indication Bitmaps. As an example, frame 605 may be a Link Reconfiguration Request frame as specified in P802.1 1 be / D7.0 standard or a modified version of this frame called UHR Link Reconfiguration Request frame as discussed in 802.11 bn TG.

[0350] At step 813, the non-AP MLD decides to use the updated NSTR Indication Bitmaps for both its legacy and UHR Multi-Link Operation with the AP MLD.

[0351] At step 706, the AP MLD checks whether it receives an Updated NSTR Indication Bitmap from the non-AP MLD. As an example, the AP MLD performs this check through the processing of frames 604, 605. If yes, the AP MLD 1 10 sends legacy Multi-Link Operation (MLO) Update Response frame 606 to acknowledge frame 605, through its affiliated AP1 111 to non-AP MLD 120 through its affiliated non-AP STA A1 121 , and goes to step 707. If no, the algorithm goes to step 708. Again, frame 606 may be any other Multi-Link frame, not limited to MLO Update Response frame.

[0352] At step 707, the AP MLD decides to use the received updated NSTR Indication Bitmaps for both its Legacy and UHR Multi-Link Operation.

[0353] At step 708, the AP MLD decides to continue using the current, i.e., legacy, NSTR Indication Bitmaps for both its Legacy and UHR Multi-Link Operation.

[0354] After this enablement sequence, the usage period 630 of the legacy NSTR Indication Bitmap lasts up to reaching a Beacon counting number corresponding to the value indicated in the TBTT Count field 914 in the DSO / NPCA / DBE OM notification frame 603. Once this value is reached, the enablement period 631 of the DSO Mode becomes effective and the usage period 632 of the updated (e.g., universal) NSTR Indication Bitmaps starts.

[0355] For some channel switching mechanisms such as DSO and NPCA (and contrary to DBE for example), the stations targeted by the activated channel switching mechanism(s) do not automatically switch to the assigned substitute channel at the time indicated in the TBTT Count field 914.

[0356] Indeed, during the DSO mode enablement period 631 , both legacy TXOPs and DSO TXOPs are supported on Link#0, between the affiliated AP1 111 and affiliated non-AP STA A1 121 , and on Link#1 , between the affiliated AP2 112 and affiliated non-AP STA A2 122. This support of both legacy and DSO TXOPs is made possible thanks to the use of the updated NSTR Indication Bitmaps that take into account the substitute channel(s).

[0357] During period 631 , several TXOP types may be performed on both Link#0 and Link#1. All or part of the exemplary TXOPs below may be performed successively, or individually.

[0358] A first legacy TXOP is initiated on Link#0, for example through an exchange 607 of initial frames such as Request To Send / Clear To Send (RTS / CTS) frames between the affiliated AP1 111 and the affiliated non-AP STA A1 121. Then, an exchange 608 of legacy data frames is performed between the affiliated AP1 11 1 and the affiliated non-AP STA A1 121 .

[0359] Next, a first DSO TXOP may be initiated on Link#1 , for example through an exchange 621 of initial control frames such as Initial Control Frame / Initial Control Response (ICF / ICR) frames between affiliated AP2 1 12 and affiliated non-AP STA A2 122. The format of these ICF / ICR frames is currently under discussion in 802.11 bn Task Group (TG), it could typically be modified MU-RTS / CTS frames supporting the signalling of an incoming DSO TXOP. This ICF / ICR exchange triggers the switching of the affiliated non-AP STA A2 122 to the substitute channel for DSO operations.

[0360] In the case of the NPCA mode, the simultaneous detection of busyness of the primary channel of affiliated AP2 1 12 and affiliated non-AP STA A2 122 triggers their switching to the anchor (substitute) channel for NPCA operations.

[0361] Then, once the channel switching is completed, a data frame exchange 622 is performed between affiliated AP2 112 and affiliated non-AP STA A2 122.

[0362] In the case of DSO mode, at the end ofthis frame exchange 622 (i.e. , end to DSO TXOP), the affiliated non-AP STA A2 122 switches back to its initial operating channel.

[0363] In the case of the NPCA mode, at the end of this frame exchange 622 (i.e., end of NPCA TXOP), the affiliated AP2 112 and affiliated non-AP STA A2 122 switch back to their initial operating channel.

[0364] Next, a second DSO TXOP is initiated on Link#0, for example through an exchange 609 of initial control frames such as Initial Control Frame / Initial Control Response (ICF / ICR) frames between affiliated AP1 111 and affiliated non-AP STA A1 121. This ICF / ICR exchange triggers the switching of the affiliated non-AP STA A1 121 to the substitute channel for DSO operations. Again, in the case of the NPCA mode, the simultaneous detection of busyness of the primary channel of affiliated AP1 111 and affiliated non-AP STA A1 121 may trigger their switching to the anchor (substitute) channel for NPCA operations.

[0365] Then, once the channel switching is completed, a data frame exchange 610 is performed between affiliated AP1 11 1 and affiliated non-AP STA A1 121.

[0366] In the case of DSO mode, at the end ofthis frame exchange 610 (i.e. end to DSO TXOP), the affiliated non-AP STA A1 121 switches back to its initial operating channel.

[0367] In the case of the NPCA mode, at the end of this frame exchange 610 (i.e. end of NPCA TXOP), the affiliated AP1 111 and affiliated non-AP STA A1 121 switch back to their initial operating channel.

[0368] Next, a second legacy TXOP is initiated on Li n k#1 , for example through an exchange 623 of initial frames such as Request To Send / Clear To Send (RTS / CTS) frames between affiliated AP2 112 and affiliated non-AP STA A2 122.

[0369] Then, an exchange 624 of legacy data frames is performed between affiliated AP2 1 12 and affiliated non-AP STA A2 122.

[0370] For other channel switching mechanisms such as DBE, the stations targeted by the activated channel switching mechanism(s) automatically switch to the assigned substitute channel at the time indicated in the TBTT Count field 914. For such channel switching mechanisms, as the substitute channel is the widest and as it overlaps the operating channel, it supports both legacy TXOPs and DBE TXOPs types

[0371] In case of DBE, during enablement period 631 , both legacy TXOPs and DBE TXOPs are supported on Link#0, between the affiliated AP1 111 and affiliated non-AP STA A1 121 , and on Link#1 , between the affiliated AP2 112 and affiliated non-AP STA A2 122. This support of both legacy and DBE TXOPs is made possible thanks to the use of the updated NSTR Indication Bitmaps that take into account the substitute channels).

[0372] During the enablement period 631 , both legacy TXOPs and DBE TXOPs are supported by the affiliated AP1 1 11 and by the affiliated AP2 112 over their respective DBE operating channel and by the affiliated non-AP STA 121 and affiliated non-AP STA 122 over their respective substitute channel.

[0373] In the case of DBE mode, the first DBE TXOP may be initiated on Link#1 , for example through an exchange 621 of initial frames such as Request To Send / Clear To Send (RTS / CTS) frames between affiliated AP2 112 and affiliated non-AP STA A2 122. Then, a data frame exchange 622 is performed between affiliated AP2 112 and affiliated non-AP STA A2 122. As the bandwidths of the substitute channel of affiliated non-AP STA A2 122 and the DBE operating channel of affiliated AP2 112 may differ, the determined bandwidth for data frame exchange 622 will be typically the smallest bandwidth among the two, this determination being also dependent on the result (which 20 MHz channels are idle) of the RTS / CTS frame exchange.

[0374] In the case of DBE mode, a second DBE TXOP may be initiated on Link#0, for example through an exchange 609 of initial frames such as Request To Send / Clear To Send (RTS / CTS) frames between affiliated AP1 111 and affiliated non-AP STA A1 121. Then, a data frame exchange 610 is performed between affiliated AP1 11 1 and affiliated non-AP STA A1 121. As the bandwidths of the substitute channel of affiliated non-AP STA A1 121 and the DBE operating channel of affiliated AP1 111 may differ, the determined bandwidth for data frame exchange 610 will be typically the smallest bandwidth among the two, this determination being also dependent on the result of the RTS / CTS frame exchange.

[0375] After these TXOP sequences, AP MLD 110 decides to disable the DSO mode with non- AP MLD 120 on both Link#0 and Link #1. For this purpose, at step 709, AP MLD 110 sends DSO / NPCA / DBE OM Notification frame 611 through its affiliated AP1 1 11 to non-AP MLD 120 through its affiliated non-AP STA A1 121. For example, in the DSO / NCPA / DBE Notification frame 611 , DSO Mode subfield 911 is set to 1 and DSO Link Bitmap subfield 913 is set to xOO(Hex) to make it clear that there is no longer DSO enabled on any links, TBTT count subfield 914 is set to xOA(Hex) and DSO Configuration Element Presence Bitmap subfield 915 may be set to xOO(Hex) to indicate that no DSO / NPCA / DBE Configuration element 420 is present, for neither links 0 and 1.

[0376] Similar to the steps of enablement, at step 814, upon receiving a frame from the AP MLD, the non-AP MLD checks whether the AP MLD disables the current DSO or NPCA or DBE mode. If yes, the algorithm goes to step 815 (similar to step 807) where the non-AP MLD processes the DSO or NPCA or DBE mode disablement frame 611 received from the AP MLD in order to check whether an update of its NSTR Indication Bitmaps is required due to the DSO or NPCA or DBE mode disablement. If no, the algorithm loops to step 813.

[0377] In case of no bitmap update, at steps 816, 817 (similar to steps 808, 809), the non-AP MLD sends a DSO / NPCA / DBE disablement response frame 612 to the AP MLD to acknowledge the disablement of the DSO or NPCA or DBE mode, and decides to continue using the current NSTR Indication Bitmaps.

[0378] In case of bitmap update, at step 818 (similar to step 810), the non-AP MLD sends DSO / NPCA / DBE disablement response frame 612 to the AP MLD to acknowledge the disablement of the DSO or NPCA or DBE mode and to indicate that an update of the NSTR Indication Bitmaps is required by setting NSTR Status Update Required subfield 916 to 1. Non- AP MLD 120 sends DSO / NPCA / DBE OM notification frame response 612 through its affiliated non-AP STA A1 121 to AP MLD 110 through its affiliated AP1 111. For example here, link pair <0, 1 > being identified again as STR by the non-AP MLD 120 due to the DSO disablement, non- AP MLD 120 indicates an update of its NSTR Indication Bitmap.

[0379] For example, in the DSO / NCPA / DBE Notification frame response 612, DSO Mode subfield 911 is set to 1 , DSO Link Bitmap subfield 913 is set to xOO(Hex) (DSO no more enabled on any links) and NSTR Status Update Required subfield 916 is set to 1 .

[0380] Next, at step 819 (similar to step 811), non-AP MLD 120 computes the updated NSTR Indication Bitmap for each of its affiliated non-AP STAs. At this stage, non-AP MLD 120 may use the legacy way (Figure 2) for the computation of the updated NSTR Indication Bitmap.

[0381] Next, at step 820 (similar to step 812), non-AP MLD 120 sends the updated NSTR Indication Bitmap for each of its affiliated non-AP STAs to AP MLD 110. For this purpose, the non-AP MLD 120 may send legacy Multi-Link Operation (MLO) Update Request frame 613 including a Reconfiguration Multi-Link element (with the Reconfiguration Operation Type subfield set to 4 to indicate a NSTR Status Update) through its affiliated non-AP STA1 121 to AP MLD 110 through its affiliated AP1 111. Note that the presence of each NSTR Indication Bitmap in each Per-STA Profile sub-element in the Link Info field of the Reconfiguration Multi-Link element is indicated through a dedicated NSTR Indication Bitmap Present subfield in the STA Control field of the corresponding Per-STA Profile sub-element.

[0382] More generally, frame 613 may be any other Multi-Link frame (hence not limited to MLO Update Request frame) including a Reconfiguration Multi-Link element (with the Reconfiguration Operation Type subfield set to 4 to indicate a NSTR Status Update or set to any other value) that conveys the updated NSTR Indication Bitmaps. As an example, frame 613 may be a Link Reconfiguration Request frame as specified in P802.1 1 be / D7.0 standard or a modified version of this frame called UHR Link Reconfiguration Request frame as discussed in 802.11 bn TG.

[0383] At step 821 (similar to step 813), the non-AP MLD decides to use the updated NSTR Indication Bitmaps (here legacy NSTR Indication Bitmaps). At step 710 (similar to step 706), the AP MLD checks whether it receives an Updated NSTR Indication Bitmap from the non-AP MLD. As an example, the AP MLD performs this check through the processing of frames 612, 613. If yes, the AP MLD 110 sends legacy Multi-Link Operation (MLO) Update Response frame 614 to acknowledge frame 613, through its affiliated AP1 111 to non-AP MLD 120 through its affiliated non-AP STA A1 121 , and goes to step 71 1 (similar to step 707). If no, the algorithm goes to step 712 (similar to step 708). Again, frame 614 may be any other Multi-Link frame, not limited to MLO Update Response frame.

[0384] At step 711 , the AP MLD decides to use the received updated NSTR Indication Bitmaps.

[0385] At step 712, the AP MLD decides to continue using the current (unchanged) NSTR Indication Bitmap.

[0386] After the disablement sequence, the usage period 632 where the channel switching mechanism is enabled lasts up to reaching a Beacon counting number corresponding to the value indicated in the TBTT Count field 914 in the DSO / NPCA / DBE OM notification frame 61 1. Once this value is reached, the next legacy period becomes effective and the usage period 633 of the updated (e.g., legacy) NSTR Indication Bitmaps starts.

[0387] On overall, the sequence provides for the non-AP MLD that upon the AP MLD deactivating the DSO or NPCA or DBE or HE SST mechanism at the non-AP MLD, the latter updates back the shared NSTR statuses (bitmaps) based on the frequency edges of only the STA’s operating channels of the affiliated non-AP STAs, i.e., back to the legacy NSTR statuses.

[0388] Also, responsive to receiving, from the AP MLD, frame 611 to deactivate the DSO or NPCA or DBE or HE SST mechanism, the non-AP MLD sends frame 612 to the AP MLD to acknowledge the deactivation, wherein the frame 612 to acknowledge includes a signalling that an update of the shared NSTR statuses by the non-AP STA is needed. A subsequent (hence separate) frame 613 conveying the updated (legacy) NSTR statuses can then be transmitted thereafter.

[0389] Furthermore, to control the timing, the non-AP MLD receives, from the AP MLD, frame 611 to deactivate the DSO or NPCA or DBE or HE SST mechanism, wherein the frame 611 to deactivate includes time information 914 about when the NSTR statuses updated back enter into force.

[0390] The frame exchange sequence 600 described here above with reference to Figure 6 illustrates a frame exchange between AP MLD 1 10 and non-AP MLD 120 on two Links. Such frame exchange sequence can apply to a higher number of links established between an AP MLD and a non-AP MLD.

[0391] The frame exchange sequence 600 described here above with reference to Figure 6 illustrates a frame exchange between AP MLD 110 and non-AP MLD 120 on two links mainly for the case of DSO mode enablement / disablement. Such frame exchange sequence is also applicable for the case of NPCA mode enablement / disablement or DBE mode enablement / disablement or any other channel switching mechanism. In the embodiments above, the DSO / NPCA / DBE Operating Mode Notification frame with the format of Figures 9a and 9b allows the enablement or disablement of the channel switching mechanisms (DSO mode or NPCA mode or DBE mode) on one or several link(s) to be managed at MLD level. Indeed, the described DSO / NPCA / DBE Operating Mode notification frame is transmitted on a link by an affiliated AP or by an affiliated non-AP STA; however, as it carries information of enablement or disablement of the channel switching mechanism for one or several link(s), it is processed at MLD level.

[0392] In alternative embodiments (not shown), the DSO / NPCA / DBE Operating Mode Notification frame may be designed to allow the enablement or disablement of the channel switching mechanisms on only one link to be managed at affiliated AP / non-AP STA level. In that case, the DSO / NPCA / DBE Operating Mode notification frame is transmitted on a link by an affiliated AP or by an affiliated non-AP STA and, as it carries the information of enablement or disablement of DSO or NPCA or DBE mode for only that link, it can be processed at affiliated STA level. Obvious adaptations of the above-described formats may be implemented. For example, with reference to Figure 9b, DSO / NPCA / DBE Mode subfields 911 , 912, 918 may be used to enable or disable the corresponding mode on the link where the DSO / NPCA / DBE Operating Mode notification frame is sent (only one subfield at a time can be set to 1), and the DSO / NPCA / DBE Link Bitmap subfield 913 is no more needed and can be omitted. The usage of TBTT Count subfield 914 remains the same, as well as the usage of DSO / NPCA / DBE Configuration Element Presence Bitmap 915 subfield, which may however be reduced to only one bit (for the link concerned). Also, the usage of NSTR Status Update Required subfield 916 remains the same.

[0393] The scenario of Figure 6 shows enablement (activation) and disablement (deactivation) sequences during which updated NSTR Indication Bitmaps (or NSTR statuses) are computed and exchanged.

[0394] To reduce overhead of such exchanges, the NSTR Indication Bitmaps needed may be precomputed and exchanged during the initial (re)association procedure. For example, the legacy NSTR Indication Bitmaps may be computed as well as the universal NSTR Indication Bitmaps (whatever the embodiment of Figure 3a, 3c or 3b, 3d) and provided to the AP MLD. Next, each time a channel switching mechanism is activated, the universal NSTR Indication Bitmaps are used, whereas each time no channel switching mechanism is activated, the legacy NSTR Indication Bitmaps are used. In this scenario, each MLD (AP or non-AP) obtains two sets of Non- Simultaneous Transmit Receive (NSTR) Indication statuses of one (or more) pair of links setup between that MLD and a second MLD - the first MLD may be an AP MLD and the second MLD a non-AP MLD, or the reverse; and switches from a first one of the sets to the other set upon a Dynamic Subband Operation (DSO) or a Non-Primary Channel Access (NPCA) or Dynamic Bandwidth Expansion (DBE) or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism being activated (by one of the MLDs, usually the AP MLD) on one of the links setup between the first and second MLDs. Of course, the MLD may switch back to the first set upon the DSO or NPCA or DBE or HE SST mechanism being deactivated.

[0395] Thanks to the various teachings above, taken in isolation or in combination, an adjusted NSTR status of the link pairs is known by the AP MLD that ensures better scheduling of the non- AP MLD in the BSS, hence better spectrum’s usage and network efficiency.

[0396] Turning now to the signalling of the updated NSTR statuses to the AP MLD, it is to be noted that P802.11 be / D7.0 lacks to provide appropriate signalling of such updated NSTR statuses when all the link pairs become STR pairs.

[0397] Indeed, firstly, for the description of the STA Control field of the Reconfiguration MultiLink element, it is written that the NSTR Indication Bitmap Present subfield is set to 1 if at least 1 NSTR link pair is present. Secondly, for NSTR update procedure, it is written that the NSTR Indication Bitmap Present subfield shall be set to 1 .

[0398] So, according to P802.11 be / D7.0 for the NSTR update procedure, Multi-Link Operation Update Request frame 605, 613 has to have the NSTR Indication Bitmap Present subfield set to 1 , which is authorized only if at least one NSTR link pair is present - which cannot be the case when all link pairs are STR. Hence, through the Multi-Link Operation Update Request frame, the NSTR update procedure of P802.11 be / D7.0 only allows allSTR-to-NSTR and NSTR-to-NSTR changes to be signalled, but not NSTR-to-allSTR changes. “allSTR” means that all link pairs are STR, while “NSTR” means that at least one link pair is NSTR.

[0399] In embodiments, to report that all link pairs are STR, the non-AP MLD may set an NSTR Indication Bitmap Present subfield in a STA Control field of a Per-STA Profile subelement of the Link Info field of the Reconfiguration Multi-Link element to 0. This may be done in a single Per- STA Profile subelement or in all Per-STA Profile subelements. These embodiments add, for the NSTR update procedure, the possibility to set the NSTR Indication Bitmap Present subfield to 0 to report that all link pairs are STR (i.e., that no NSTR link pair is present).

[0400] In the example of Figure 6 above, only two links are illustrated and the unique link pair <0,1 > becomes again STR after disablement (frame 611) of the channel switching mechanism.

[0401] No updated NSTR Indication Bitmap needs to be present in the Multi-Link Operation (MLO) Update Request frame 613. Indeed, in this scenario, AP MLD 1 10 readily understands that non-AP MLD 120 has no more NSTR constraints when reading the NSTR Indication Bitmap Present subfield set to 0 in the STA Control field of a Per-STA Profile subelement of the Link Info field of the Reconfiguration Multi-Link element carried in the Multi-Link Operation (MLO) Update Request frame 613.

[0402] In alternative embodiments, to report that all link pairs are STR, the non-AP MLD may set an NSTR Indication Bitmap in the STA Info field of a Per-STA Profile subelement of the Link Info field of the Reconfiguration Multi-Link element to all 0s, i.e., all bits in the bitmap are set to 0. In this case, AP MLD 110 understands that non-AP MLD 120 has no more NSTR constraints when reading the NSTR Indication Bitmap Present subfield set to 1 in the STA Control field, which is authorized when the Operation Type subfield is set to the value 4 in the STA Control field corresponding to NSTR Status Update (independently of the presence or not of at least one NSTR link pair), and when reading the NSTR Indication Bitmap subfield with all bits set to 0 in the STA Info field of the Per-STA Profile subelement of the Link Info field of the Reconfiguration Multi-Link element carried in the Multi-Link Operation (MLO) Update Request frame 613. In other words in that case, the NSTR Indication Bitmap Present subfield in the STA Control field is set to 1 if at least one NSTR link pair is present for the non-AP MLD that contains the link corresponding to the Link ID or if the Reconfiguration Operation Type subfield is set to the value 4 corresponding to the NSTR Status Update; otherwise, this subfield is set to 0.

[0403] These embodiments add, for the description of the NSTR Indication Bitmap Present subfield, the condition that it is set to 1 if the Operation Type subfield is set to the value 4 corresponding to the NSTR Status Update. In addition, for the NSTR update procedure, it is clarified that all bits of the bitmap are set to 0 to indicate that all link pairs are STR.

[0404] With more details, the following overall views may apply.

[0405] The ability of a non-AP MLD to perform STR operation on a pair of setup links may change after ML setup if an AP affiliated with the associated AP MLD switches the AP’s operating channel (including the BSS operating channel) to a (substitute) channel that would cause the associated non-AP STA to not satisfy the new STR requirements or if an AP affiliated with the associated AP MLD enables DSC TXOPs or NPCA TXOPs or DBE TXOPS or HE SST SPs that switch the STA’s operating channel of associated non-AP STA to a (substitute) channel that would cause the associated non-AP STA to have different NSTR constraints. For a non-AP MLD with dot1 I NSTRStatusUpdatelmplemented set to true, if its ability to perform STR / NSTR operations changes after the channel switch or during DSO TXOPs, or NPCA TXOPS or DBE TXOPs or HE SST SPs, the non-AP MLD may transmit a Multi-Link Operation Update Request frame with the Operation Update Type subfield set to 4 on any enabled link to indicate the updated STR / NSTR link status to the associated AP MLD, from which it has received a Basic Multi-Link element with the NSTR Status Update Support subfield equal to 1 , using the NSTR Indication Bitmap subfields of the included Reconfiguration Multi-Link element. Otherwise, the non-AP MLD does not transmit a Multi-Link Operation Update Request frame with Operation Update Type subfield set to 4.

[0406] A non-AP MLD that transmits a Multi-Link Operation Update Request frame that contains a Reconfiguration Multi-Link element with Operation Type subfield equal to 4 may include, in the Reconfiguration Multi-Link element, one Per-STA Profile subelement for each link, identified by the link ID, that is setup between the non-AP MLD and the AP MLD. The Reconfiguration MultiLink element may additionally have:

[0407] • All subfields in the Presence Bitmap subfield of the Multi-Link Control field set to 0.

[0408] • All subfields of the STA Control field set to 0, except for the Link ID, the NSTR Indication Bitmap Present, and the NSTR Bitmap Size subfields that are set as indicated below: o The Link ID subfield may be set to the identifier of the setup link for which the NSTR status is reported in the Per-STA Profile subelement. o The NSTR Indication Bitmap Present subfield may be set to 1 if at least one NSTR link pair is present for the non-AP MLD; otherwise, the NSTR Indication Bitmap Present subfield may be set to 0 (contrary to P802.11 be / D7.0) if no NSTR link pair is present for the non-AP MLD (i.e., if all link pairs are STR). This corresponds to the first embodiments above to signal a NSTR-to-allSTR change. o The NSTR Bitmap Size subfield (present only if a bitmap is present) may be set to indicate the size of the NSTR Indication Bitmap subfield.

[0409] • When the NSTR Indication Bitmap subfield is included, it may be set to indicate STR or NSTR for each pair of links formed between the link corresponding to the link ID and other setup links for the non-AP MLD.

[0410] After receiving a Multi-Link Operation Update Request frame with Operation Update Type subfield equals to 4 from the non-AP STA affiliated with an associated non-AP MLD, the AP MLD with dotH NSTRStatusUpdatelmplemented set to true may send a Multi-Link Operation Update Response frame to the non-AP MLD on any enabled link subject to the power state of the non- AP STA operating on that link with the Status Code subfield set to 0 (SUCCESS).

[0411] The AP MLD may update the NSTR status of the setup link pairs for that non-AP MLD after successfully sending the Multi-Link Update Response frame to the non-AP MLD, after which the AP MLD and non-AP MLD may exchange frames using the updated constraints.

[0412] In a case where, after a BSS channel switch or enablement / disablement of DSO / NPCA / DBE / HE SST mechanisms, a non-AP MLD has no any remaining NSTR link pair, the non-AP MLD may send an MLO Update Request frame to the AP MLD with the NSTR Indication Bitmap Present subfield set to 0 and no NSTR Indication Bitmap present, as introduced above.

[0413] In a variant, the ability of a non-AP MLD to perform STR operation on a pair of setup links may change after ML setup if an AP affiliated with the associated AP MLD switches the AP’s operating channel to a (substitute) channel that would cause the associated non-AP STA to not satisfy the new STR requirements or if an AP affiliated with the associated AP MLD enables DSC TXOPs or NPCA TXOPs or DBE TXOPS or HE SST SPs that switch the STA’s operating channel of associated non-AP STA to a (substitute) channel that would cause the associated non-AP STA to have different NSTR constraints. For a non-AP MLD with dot1 I NSTRStatusUpdatelmplemented set to true, if its ability to perform STR / NSTR operations changes after the channel switch or during DSO TXOPs, or NPCA TXOPS or DBE TXOPs or HE SST SPs, the non-AP MLD may transmit a Multi-Link Operation Update Request frame with the Operation Update Type subfield set to 4 on any enabled link to indicate the updated STR / NSTR link status to the associated AP MLD, from which it has received a Basic Multi-Link element with the NSTR Status Update Support subfield equal to 1 , using the NSTR Indication Bitmap subfields of the included Reconfiguration Multi-Link element. Otherwise, the non-AP MLD does not transmit a Multi-Link Operation Update Request frame with Operation Update Type subfield set to 4.

[0414] A non-AP MLD that transmits a Multi-Link Operation Update Request frame that contains a Reconfiguration Multi-Link element with Operation Type subfield equal to 4 may include in the Reconfiguration Multi-Link element one Per-STA Profile subelement for each link, identified by the link ID, that is setup between the non-AP MLD and the AP MLD. The Reconfiguration MultiLink element may additionally have:

[0415] • All subfields in the Presence Bitmap subfield of the Multi-Link Control field set to 0.

[0416] • All subfields of the STA Control field set to 0, except for the Link ID, the NSTR Indication Bitmap Present, and the NSTR Bitmap Size subfields. o The Link ID subfield may be set to the identifier of the setup link for which the NSTR status is reported in the Per-STA Profile subelement. o The NSTR Indication Bitmap Present subfield may be set to 1 , as already required in P802.11 be / D7.0. o The NSTR Bitmap Size subfield may be set to indicate the size of the NSTR Indication Bitmap subfield.

[0417] • The NSTR Indication Bitmap subfield may be included and may be set to indicate STR or NSTR for each pair of links formed between the link corresponding to the link ID and other setup links for the non-AP MLD. All bits of the NSTR Indication Bitmap subfield may be set to 0 (contrary to P802.11 be / D7.0) to indicate the STR status for each pair of links formed between the link corresponding to the link ID and other setup links for the non-AP MLD. This corresponds to the second embodiments above to signal a NSTR-to-allSTR change.

[0418] In this variant, it is assumed that the NSTR Indication Bitmap Present subfield in the STA Control field of the Reconfiguration Multi-Link element field is set to 1 if at least one NSTR link pair is present for the non-AP MLD that contains the link corresponding to the Link ID or if the Reconfiguration Operation Type subfield in the STA Control field is set to the value 4 corresponding to the NSTR Status Update; otherwise, this subfield is set to 0.

[0419] In other words, it is assumed that the NSTR Indication Bitmap Present subfield in the STA control field of the Reconfiguration Multi-Link element indicates the presence of the NSTR Indication Bitmap subfield in the STA Info field and is set to 1 if the NSTR Indication Bitmap subfield is present in the STA Info field; otherwise, this subfield is set to 0. The NSTR Indication Bitmap subfield is present in the STA Info field if at least one NSTR link pair is present for the non-AP MLD that contains the link corresponding to the Link ID or if the Reconfiguration Operation Type subfield in the STA Control field is set to the value 4 corresponding to the NSTR Status Update.

[0420] After receiving a Multi-Link Operation Update Request frame with Operation Update Type subfield equals to 4 from the non-AP STA affiliated with an associated non-AP MLD, the AP MLD with dotH NSTRStatusUpdatelmplemented set to true may send a Multi-Link Operation Update Response frame to the non-AP MLD on any enabled link subject to the power state of the non- AP STA operating on that link with the Status Code subfield set to 0 (SUCCESS). The AP MLD may update the NSTR status of the setup link pairs for that non-AP MLD after successfully sending the Multi-Link Update Response frame to the non-AP MLD, after which the AP MLD and non-AP MLD may exchange frames using the updated constraints.

[0421] In a case where, after a BSS channel switch or enablement / disablement of DSO / NPCA / DBE / HE SST mechanisms, a non-AP MLD has no any remaining NSTR link pair, the non-AP MLD may send an MLO Update Request frame to the AP MLD with the NSTR Indication Bitmap Present subfield set to 1 and all bits of the NSTR Indication Bitmap set to 0, as introduced above.

[0422] Figure 10 shows a schematic representation of a wireless communication device 1000 in accordance with embodiments.

[0423] Communication device 1000 is typically any of the MLDs discussed above, of a wireless network, configured to implement at least one embodiment of the present invention. The communication device 1000 may preferably be a device such as a micro-computer, a workstation or a light portable device. The communication device 1000 comprises a communication bus 1013 to which there are preferably connected: a central processing unit 1001 , such as a processor, denoted CPU; a memory 1003 for storing an executable code of methods or steps of the methods according to embodiments of the invention as well as the registers adapted to record variables and parameters necessary for implementing the methods; and at least two communication interfaces 1002 and 1002’ connected to the wireless communication network, for example a wireless communication network according to one of the IEEE 802.11 family of standards, via transmitting and receiving antennas 1004 and 1004’, respectively.

[0424] Preferably the communication bus 1013 provides communication and interoperability between the various elements included in the communication device 1000 or connected to it. The representation of the bus is not limiting and in particular the central processing unit is operable to communicate instructions to any element of the communication device 1000 directly or by means of another element of the communication device 1000.

[0425] The executable code may be stored in a memory that may either be read only, a hard disk or on a removable digital medium such as for example a disk. According to an optional variant, the executable code of the programs can be received by means of the communication network, via the interface 1002 or 1002’, in order to be stored in the memory of the communication device 1000 before being executed.

[0426] In an embodiment, the device is a programmable apparatus which uses software to implement embodiments of the invention. However, alternatively, embodiments of the present invention may be implemented, totally or in partially, in hardware (for example, in the form of an Application Specific Integrated Circuit or ASIC). Although the present invention has been described hereinabove with reference to specific embodiments, the present invention is not limited to the specific embodiments, and modifications will be apparent to a skilled person in the art which lie within the scope of the present invention.

[0427] Many further modifications and variations will suggest themselves to those versed in the art upon referring to the foregoing illustrative embodiments, which are given by way of example only and which are not intended to limit the scope of the invention, that being determined solely by the appended claims. In particular the different features from different embodiments may be interchanged, where appropriate.

[0428] 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

CLAIMS1. A method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: determining a Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup with two respective APs affiliated with an AP MLD, the determining being based on frequency edges of operating channels of the two affiliated APs.

2. The method of Claim 1 , wherein the NSTR status of the link pair is based on the nearest frequency edges of the operating channels of the two affiliated APs.

3. The method of Claim 2, wherein the NSTR status of the link pair is obtained by comparing a frequency difference between the nearest frequency edges of the operating channels of the two affiliated APs with a minimum frequency gap value specific to the non-AP MLD.

4. The method of Claim 1 , including reporting the NSTR status during association or re-association of the non-AP MLD with the AP MLD.

5. The method of Claim 1 , wherein at least one operating channel of the two affiliated APs is an expended operating channel resulting from a Dynamic Bandwidth Expansion (DBE) mechanism, compared to a Basic Service Set (BSS) operating channel implemented by the affiliated AP in absence of DBE mechanism.

6. A method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: determining a Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup between two respective non-AP stations (STAs) affiliated with the non-AP MLD and two respective APs affiliated with an AP MLD, the determining being based on a frequency edge of channels comprising an operating channel of a first one of the affiliated non-AP STAs that corresponds to a first link of the link pair and a substitute channel of the first affiliated non-AP STA, and a frequency edge of the other link of the link pair.

7. The method of Claim 6, wherein the NSTR status of the link pair is based on the nearest frequency edge of the channels comprising the operating and substitute channels of the first affiliated non-AP STA to the frequency edge of the other link.

8. The method of Claim 7, wherein the NSTR status of the link pair is obtained by comparing a frequency difference between the nearest frequency edge of the channels comprising the operating and substitute channels of the first affiliated non-AP STA, and the frequency edge of the other link with a minimum frequency gap value specific to the non-AP MLD.

9. The method of Claim 6, wherein the non-AP MLD obtains the substitute channel from the AP MLD and reports the NSTR status of the link pair to the AP MLD, wherein the obtaining and the reporting take place during association or re-association of the non-AP MLD with the APMLD.

10. The method of Claim 1 or 6, wherein the non-AP MLD obtains operating channels of the affiliated APs from the AP MLD.

11. The method of Claim 1 or 6, wherein the non-AP MLD reports the NSTR status of the link pair to the AP MLD.

12. The method of Claim 1 or 6, wherein the non-AP MLD reports statuses of a plurality of link pairs to the AP MLD.

13. The method of Claim 1 or 6, including reporting the NSTR status of the link pair upon the AP MLD activating a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism on one link of the link pair at the non-AP MLD.

14. The method of Claim 13, wherein upon the AP MLD deactivating the DSO or NPCA or DBE or HE SST mechanism, the non-AP MLD reports to the AP MLD a NSTR status of the link pair that is based on frequency edges of only operating channels of non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair.

15. A method in a first Multi-Link Device (MLD), comprising: obtaining two sets of Non-Simultaneous Transmit Receive (NSTR) Indication statuses of a pair of links setup between the first MLD and a second MLD; switching from a first one of the sets to the other set upon a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism being activated on one of the links setup between the first and second MLDs.

16. The method of Claim 15, wherein the first MLD switches back to the first set upon the DSO or NPCA or DBE or HE SST mechanism being deactivated.

17. A method in an Access Point (AP) Multi-Link Device (MLD), comprising: receiving, from one or more non-AP MLDs, a minimum frequency gap value for Simultaneous Transmit Receive (STR) operation, selecting, based on the minimum frequency gap value or values received, a non-AP MLD and / or substitute channel parameters to trigger a communication mechanism at the non-AP MLD, the communication mechanism requiring switching of a station affiliated with the non-AP MLD from an operating channel to a substitute channel.

18. A method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: sharing, with an AP MLD, a Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup with the AP MLD;upon the AP MLD enabling a Dynamic Subband Operation (DSO) mechanism or a NonPrimary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism on a link of the link pair, updating the shared NSTR status.

19. The method of Claim 18, further comprising sharing the updated NSTR status with the AP MLD.

20. The method of Claim 18, wherein the updated NSTR status is an NSTR status for a link pair that includes the link on which the DSO or NPCA or DBE or HE SST mechanism is activated.

21. The method of Claim 18, wherein, responsive to receiving, from the AP MLD, a frame to enable the DSO or NPCA or DBE or HE SST mechanism, the non-AP MLD sends to the AP MLD a frame to acknowledge the enabling, wherein the frame to acknowledge includes a signalling that an update of the shared NSTR status by the non-AP STA is needed.

22. The method of Claim 18, wherein the non-AP MLD receives, from the AP MLD, a frame to enable the DSO or NPCA or DBE or HE SST mechanism, wherein the frame to enable includes time information about when the updated NSTR status enter into force.

23. The method of Claim 22, wherein the time information is a number of Target Beacon Transmission Times (TBTT).

24. The method of Claim 18, wherein upon the AP MLD disabling the DSO or NPCA or DBE or HE SST mechanism at the non-AP MLD, the non-AP MLD updates back the shared NSTR status based on the frequency edges of only the operating channels of the affiliated non-AP STAs.

25. The method of Claim 24, wherein the non-AP MLD, responsive to receiving, from the AP MLD, a frame to disable the DSO or NPCA or DBE or HE SST mechanism, sends to the AP MLD a frame to acknowledge the disabling, wherein the frame to acknowledge includes a signalling that an update of the shared NSTR status by the non-AP STA is needed.

26. The method of Claim 24, wherein the non-AP MLD receives, from the AP MLD, a frame to disable the DSO or NPCA or DBE or HE SST mechanism, wherein the frame to disable includes time information about when the NSTR status updated back enter into force.

27. The method of Claim 18, wherein sharing the NSTR status take place during association or re-association of the non-AP MLD with the AP MLD.

28. A method in an Access Point (AP) Multi-Link Device (MLD), comprising: receiving, from at least one non-AP MLD, a Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup between the AP MLD and the non-AP MLD; enabling a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a HighEfficiency Subchannel Selective Transmission (HE SST) mechanism on a link of the link pair at the non-AP MLD; responsive to the enabling, receiving an updated NSTR status from the non-AP MLD.

29. The method of Claim 18 or 28, wherein the updated NSTR status of a link pair is determined based on a frequency edge of an operating channel of an affiliated AP of the AP MLD corresponding to the link on which the DSO or NPCA or DBE or HE SST mechanism is activated.

30. The method of Claim 18 or 28, wherein the updated NSTR status of a link pair is determined by comparing a frequency difference between the nearest frequency edges of operating channels of two affiliated APs of the AP MLD corresponding to the links of the link pair with a minimum frequency gap value specific to the non-AP MLD.

31. The method of Claim 18 or 28, wherein the updated NSTR status of a link pair is determined based on a frequency edge of a substitute channel to operate DSO or NPCA or DBE or HE SST on the link on which the DSO or NPCA or DBE or HE SST mechanism is activated.

32. The method of Claim 31 , wherein the DSO or NPCA is operated in an expended operating channel resulting from a Dynamic Bandwidth Expansion (DBE) mechanism enabled by the AP MLD.

33. The method of Claim 18 or 28, wherein the updated NSTR status of a link pair is determined by comparing a frequency difference with a minimum frequency gap value specific to the non-AP MLD, the frequency difference being calculated between the nearest frequency edge of channels comprising an operating channel of an affiliated non-AP STA of the non-AP STA that corresponds to the link on which the DSO or NPCA or DBE or HE SST mechanism is activated and a substitute channel of the affiliated non-AP STA to operate DSO or NPCA or DBE or HE SST on that link, to a frequency edge of the other link of the link pair.

34. The method of Claim 18 or 28, wherein the updated NSTR status of a link pair is determined by comparing a frequency difference with a minimum frequency gap value specific to the non-AP MLD, the frequency difference being calculated between the nearest frequency edge of a substitute channel of an affiliated non-AP STA of the non-AP STA to operate DSO or NPCA or DBE or HE SST on one of the links to a frequency edge of the other link.

35. The method of Claim 18 or 28, wherein an NSTR status of a link pair is based on frequency edges of only operating channels of non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair.

36. The method of Claim 18 or 28, wherein at least one updated NSTR status is determined based on a frequency edge different from a frequency edge ofthe operating channels of the affiliated non-AP STAs.

37. The method of Claim 19 or 28, wherein the updated NSTR status are exchanged in a frame carrying a Reconfiguration Multi-Link (ML) element.

38. The method of Claim 37, wherein the frame carrying the Reconfiguration ML element is an UHR Link Reconfiguration frame or a MLO Update Request frame.

39. A method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: activating a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism over an operating channel of the non-AP MLD, wherein the operating channel is an expended operating channel resulting from a Dynamic Bandwidth Expansion (DBE) mechanism.

40. A method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: sharing, with an AP MLD, at least one Non-Simultaneous Transmit Receive (NSTR) status of a pair of links setup with the AP MLD, wherein an NSTR status of a link pair is based on frequency edges of only operating channels of non-AP STAs affiliated to the non-AP MLD that correspond to the links of the link pair; upon receiving from the AP MLD a frame to activate a Dynamic Subband Operation (DSO) mechanism or a Non-Primary Channel Access (NPCA) mechanism or a Dynamic Bandwidth Expansion (DBE) mechanism or a High Efficiency Subchannel Selective Transmission (HE SST) mechanism at the non-AP MLD, deciding to accept or refuse the activation based on whether the activation of the DSO or NPCA or DBE or HE SST mechanism modifies or not at least one NSTR status of the link pair, and sending to the AP MLD a frame to report the decision.

41. A method in a non-Access Point (non-AP) Multi-Link Device (MLD), comprising: sending, to an AP MLD, a Multi-Link Operation Update Request frame including a Reconfiguration Multi-Link element to report a change of Non-Simultaneous Transmit Receive (NSTR) statuses of pairs of links setup with the AP MLD, wherein to report that all link pairs are STR, an NSTR Indication Bitmap Present subfield in a STA Control field of a Per-STA Profile subelement of a Link Info field of the Reconfiguration Multi-Link element is set to 0, or the NSTR Indication Bitmap Present subfield is set to 1 and an NSTR Indication Bitmap in a STA Info field of a Per-STA Profile subelement of the Link Info field of the Reconfiguration Multi-Link element is set to all Os.

42. The method of Claim 41 , wherein setting the NSTR Indication Bitmap to all Os to report that all link pairs are STR is conditional to a Reconfiguration Operation Type subfield in the STA Control field set to 4.

43. A wireless communication device comprising at least one microprocessor configured for carrying out the method of Claim 1 , 6, 15, 17, 18, 28, 39, 40 or 41 .

44. A non-transitory computer-readable medium storing a program which, when executed by a microprocessor or computer system in a wireless device, causes the wireless device to perform the method of Claim 1 , 6, 15, 17, 18, 28, 39, 40 or 41 .

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