Enhanced power management for multi-link devices

Abstract

Benefits can be obtained by activating or deactivating a Per-Link PM mechanism on behalf of other affiliated non-AP STAs. An affiliated STA may thus activate multiple Per-Link PM mechanisms at once (i.e., using a single notification frame) for multiple affiliated non-AP STAs. A method comprises, at the affiliated non-AP STA, sending one notification frame to an AP MLD to enable or disable power management (PM) on an enabled link between another non-AP STA of the non-AP MLD and the AP MLD, in particular to enable or disable power management (PM) on multiple enabled links with the AP MLD. A Multiple Per-Link PM Mode subfield is provided in the frame to indicate activation or deactivation. A Multiple Per-Link PM Link Bitmap is provided to signal which links are concerned. Finally, a Multiple Per-Link PM subfield indicates the Per-Link PM mechanism to activate, e.g., the Single Link EMLSR feature.

Description

[0001] ENHANCED POWER MANAGEMENT FOR MULTI-LINK DEVICES

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to wireless communications, to Multi-Link (ML) communications, and more specifically to the management of power saving modes at stations of a non-AP Multi-Link Device (MLD).

[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 release, known as 802.1 1 be or EHT for “Extremely High Throughput”, (last version known as IEEE P802.11 be™ / D5.1 of March 2024, “the D5.1 standard” below) introduces the Multi-Link (ML) Operation (MLO). MLO improves data throughput by allowing communications between STAs over multiple concurrent and non-contiguous communication links.

[0008] MLO enables a non-AP (Access Point) MLD (ML Device) to register with an AP MLD, i.e. , to discover, authenticate, associate and set up multiple links with the AP MLD. A setup link becomes an enabled link for a non-AP MLD when at least one TID is mapped to that link. Each enabled link enables channel access and frame exchanges between the nton-AP MLD and the AP MLD based on supported capabilities exchanged during the association procedure.

[0009] A MLD is a logical entity that has more than one affiliated station (STA) and has a single medium access control (MAC) service access point (SAP) to logical link control (LLC), which includes one MAC data service for the multiple affiliated stations. An AP MLD is thus made of multiple affiliated APs whereas a non-AP MLD is made of multiple affiliated non-AP STAs. The affiliated STAs in both AP MLD and non-AP MLD can use 802.11 mechanisms to communicate with affiliated STAs of another MLD over each of the multiple communication links that are set up and then enabled.

[0010] With the introduction of MLO and of spatial multiplexing capabilities of the MLDs, new Operating Modes (OM) referred to as Enhanced Multi-Link Operating Mode (EML OM), have been introduced in the standard 802.11 be, namely the EMLSR (Enhanced Multi-Link Single Radio) mode and the EMLMR (Enhanced Multi-Link Multi-Radio) mode allowing significant gain in terms of throughput enhancement and latency reduction.

[0011] However, the power consumption of a non-AP MLD increases compared to a single link device, mainly because the non-AP MLD operates now on two or more links under the MLO.

[0012] In order to cope with this issue, each affiliated non-AP STA of the non-AP MLD may activate Power Management (PM) where the affiliated non-AP STA switches between a low- power mode reducing communication performance and a high-power mode providing high communication performance.

[0013] A Power Management (PM) mechanism or scheme defines the rules the affiliated non- AP STA follows to switch from one mode to the other.

[0014] Conventional PM mechanisms are legacy PM mechanisms in the meaning they can be used by legacy single link devices or stations (i.e., up to 802.11 ax station). Legacy PM mechanisms are specified in the standard IEEE Std 802.11 -2020 for the legacy non-MLD STAs, in particular in section “1 1 .2 Power Management”.

[0015] They include TIM (Traffic Indication Map)-based mechanisms and SMPS mechanism. In the TIM-based mechanism (section 11 .2.3), the STA powers on its receiver when it needs to listen for a TIM in a Beacon frame, which TIM indicates the presence (or not) of buffered data at the AP for that STA. In case of no buffered data, the STA powers off its receiver until the next Beacon frame, otherwise it is involved in a transmission of the buffered data and thus remains in the power-on mode. The Spatial Multiplexing Power Save (SMPS) feature (section 11.2.6) allows a non-AP HT STA in an infrastructure BSS to operate with only one active receive chain for a significant portion of time. In dynamic SM power save mode, the STA enables its multiple receive chains when it receives the start of a frame exchange sequence addressed to it (e.g. an RTS / CTS sequence). The STA switches to the multiple receive chain mode when it receives the starting frame addressed to it and switches back immediately when the frame exchange sequence ends.

[0016] Another PM mechanism has recently emerged with the ML developments of the 802.11 be Working Group. A so-called Single Link EMLSR feature has been defined, consisting for a non- AP MLD to apply the EMLSR mode on only one link. As known, the EMLSR mode requires that an Initial Control Frame (ICF) be transmitted by the AP MLD prior to a frame exchange. As the ICF is a non-HT (duplicate) PPDU (using a rate of 6 Mb / s, 12 Mb / s, or 24 Mb / s) with the number of spatial stream (NSS) equal to 1 , it allows the non-AP MLD to operate in a listen mode with a minimal and low power radio configuration on the concerned link, up to receiving the ICF. Indeed, there is no need to set up with the maximum supported MCS and NSS as the ICF is a non-HT PPDU. The non-AP MLD switches to the transmission mode (with full resources for the radio configuration) only when the ICF is received, and for the duration of the frame exchange. Consequently, the Single Link EMLSR feature can be viewed as a PM mechanism.

[0017] For the time being, all these PM mechanisms are insufficient to provide optimal power management in non-AP MLD that have multiple enabled links with an AP MLD. There is a need to improve this situation. SUMMARY OF INVENTION

[0018] Both the legacy PM mechanisms and the recent Single Link EMLSR feature operate at link level only, meaning they are activated and deactivated independently of each other link. In other words, each affiliated non-AP STA initiates its own PM mechanism independently of the others non-AP STA. Such mechanisms can therefore be named “Per-Link” PM mechanisms.

[0019] This activation / deactivation at link level is not optimal and can be optimized. In particular, the inventors have considered allowing any affiliated non-AP STA to activate and / or deactivate a Per-Link PM mechanism for one or more other affiliated non-AP STAs of the same non-AP MLD. This may result in activating and / or deactivating Per-Link PM mechanisms at once (i.e. , using a single notification frame) for multiple affiliated non-AP STAs, hence reducing signalling costs.

[0020] In this respect, a communication method in a wireless network is proposed that comprises, at a non-access point (non-AP) station (STA) affiliated with a non-AP multi-link device (MLD), sending one notification frame to an AP MLD to enable or disable power management (PM) on at least an enabled link between another non-AP STA of the non-AP MLD and the AP MLD.

[0021] In particular, the notification frame may be provided to enable or disable power management (PM) on multiple enabled links with the AP MLD.

[0022] The AP MLD thus receives this notification frame to contribute to PM on each of the links, where appropriate (e.g., to send TIMs in its Beacon frames, to send Initial Control Frames, ...).

[0023] It turns out that the non-AP MLD thus applies a PM mechanism on each of the links, be them the same PM mechanism over the links or different ones as explained below.

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

[0025] As known, the non-AP MLD includes a plurality of affiliated non-AP stations having enabled links with respective APs affiliated with the AP MLD. In embodiments, the notification frame enables or disables PM on the enabled link between the non-AP STA sending the notification frame and the AP MLD. In other words, one of the multiple links on which PM is enabled or disabled is the one of the sending affiliated non-AP MLD.

[0026] In embodiments, the notification frame includes a bitmap signalling the at least one (more generally multiple) link for PM enabling or disabling from amongst a plurality of enabled links with the AP MLD. This allows links to be individually indicated.

[0027] In some embodiments, the bitmap is signalled in the EMLSR / EMLMR Link Bitmap subfield of an EML Control field according to the IEEE P802.11 be™ / D5.1 standard (section 9.4.1 .70). Reuse of known field advantageously does not require new frame formats to be defined. The bitmap is defined in bits B8 and seq. Due to this new use of the bitmap, this subfield may be renamed EMLSR / EMLMR / Multiple Per-Link PM Link Bitmap.

[0028] In some embodiments, a bit in an EML Control field according to the IEEE P802.11 be™ / D5.1 standard takes a first value to signal enabling of power management on the at least one (more generally multiple) link or a second value to signal disabling of power management on the at least one link. In particular, the bit may be one from bits B4-B7 (reserved bits in the D5.1 standard), the EMLSR Mode bit (bit BO), and

[0029] - the EMLMR Mode bit (bit B1).

[0030] In some embodiments, the bit is the EMLSR Mode bit if the non-AP MLD declares it supports EMLMR operation or is the EMLMR Mode bit if the non-AP MLD declares it supports EMLSR operation. Indeed, as the EMLSR and EMLMR modes are exclusive one of the other in the D5.1 standard, one of the two EMLSR Mode and EMLMR Mode bits is not used depending on the support declaration made by the non-AP MLD. The above configuration thus proposes to reuse this “lost” bit in order to reduce signalling costs.

[0031] Of course, in case neither EMLSR operations nor EMLMR operations are supported, any of the two bits may be used to signal the enabling or disabling of PM on multiple links (Multiple Per-Link PM).

[0032] In some embodiments, the notification frame signals one or more PM mechanisms that are enabled or disabled on the at least one (more generally multiple) link. This provides more flexibility for the non-AP MLDs to choose their PM mechanism or mechanisms.

[0033] In embodiments, a PM mechanism is signalled per link of multiple links to enable or disable. This configuration provides the highest level of flexibility to the non-AP MLDs to choose the PM mechanism(s) to use.

[0034] In variants, a single PM mechanism is signalled that is enabled or disabled on multiple links. This configuration limits the signalling costs while providing flexibility of PM mechanism choice to the non-AP MLDs.

[0035] In some embodiments, the notification frame includes a configuration switch delay defining a duration required by the non-AP MLD to configure an affiliated non-AP station when switching between a low-power configuration and a high-power configuration (meaning either from low-power to high-power, or from high-power to low-power). This allows the AP MLD to properly initiate and perform a frame exchange with that affiliated non-AP station. As an example, such a frame exchange that is initiated by a non-HT PPDU such as an ICF requires the non-AP station to reconfigure its radio resources before being able to operate on a full bandwidth with full MCS and SS.

[0036] The configuration switch delay may be set per link or be one and the same for all the links concerned by the PM enabling or disabling.

[0037] In some embodiments, the notification frame is an Enhanced Multi-Link (EML) Operating Mode Notification frame as defined in the IEEE P802.11 be™ / D5.1 standard. Reuse of a known format advantageously avoids new frame formats to be defined.

[0038] In alternative embodiments, the notification frame is a protected Ultra High Reliability (UHR) Action frame (meaning this type of frame does not yet exist in the IEEE P802.11 be™ / D5.1 standard) that includes a Control field (which can be labelled EML PM Control field or UHR PM Control field) comprising: a subfield taking a first value to signal enabling of PM on the at least one link or a second value to signal disabling of PM on the at least one link, a bitmap subfield signalling the at least one link for PM enabling or disabling from amongst a plurality of enabled links with the AP MLD, and optionally, a parameter subfield signalling one or more PM mechanisms that are enabled or disabled on the at least one link and / or signalling a configuration switch delay defining a duration required by the non-AP MLD to configure an affiliated non- AP station when switching between a low-power configuration and a high-power configuration.

[0039] UHR or “Ultra High Reliability” makes reference to the 802.11 bn standard under drafting. The above new frame format can advantageously be optimized in terms of fields compared to reusing known formats, in order to save signalling bits.

[0040] In some embodiments, the method further comprises signalling, to the AP MLD, a Multiple Per-Link PM support (or capability) of the non-AP MLD. This defines the capability of the non-AP MLD to exchange frames triggering simultaneously PM for multiple links.

[0041] In embodiments, the Multiple Per-Link PM support is signalled using one signalling field from amongst: one bit of an Enhanced Multi-Link (EML) Capabilities subfield in a Common Info field of a Basic Multi-Link element, in particular any of bits B8-B10 and B15 (reserved bits), one bit of an Extended MLD Capabilities And Operations subfield in a Common Info field of a Basic Multi-Link element, in particular any of bits B6 (used by the AP MLD to signal support of EMLSR Enablement On One link, i.e. , Single Link EMLSR) and B7-B15 (reserved bits).

[0042] In some embodiments, the signalling of the Multiple Per-Link PM support is made together with a signalling of one or more PM mechanisms (or schemes) supported (i.e., available) by the non-AP MLD. This configuration provides some flexibility to the non-AP MLD to choose the PM mechanism or mechanisms it wishes to use.

[0043] In embodiments, one or more supported PM mechanisms are signalled per each enabled link with the AP MLD. This configuration provides the highest level of flexibility to the non-AP MLDs to choose the PM mechanism(s) to use.

[0044] In variants, one or more supported PM mechanisms is signalled once for all enabled links with the AP MLD. This configuration limits the signalling costs while providing flexibility of PM mechanism choice to the non-AP MLDs.

[0045] In some embodiments, the notification frame enables or disables power management (PM) of the other non-AP STA of the non-AP MLD. Correspondingly, the present disclosure also provides a communication method in a wireless network, comprising, at a non-access point (non- AP) station (STA) affiliated with a non-AP multi-link device (MLD), activating or deactivating power management (PM) mechanism for one or more other affiliated non-AP STAs of the same non-AP MLD.

[0046] The present disclosure also provides a protected Action frame (in the meaning of the D5.1 standard) to be sent by a non-access point (non-AP) station (STA) affiliated with a non-AP multilink device (MLD), the protected Action frame including: a first field taking a first value to signal enabling of power management (PM) on one or more enabled links between the non-AP MLD and an AP MLD, and a second value to signal disabling of PM, a bitmap field to indicate the one or more links.

[0047] The frame may further comprise: a parameter field to indicate one or more Per-Link PM mechanisms to be applied on the one or more links, and / or a configuration switch delay field indicating a duration required by the non-AP MLD to configure an affiliated non-AP station when switching between a low-power configuration and a high-power configuration.

[0048] Correlatively, the disclosure also provides a wireless communication device comprising at least one microprocessor configured for carrying out any method as described above.

[0049] Another aspect of the disclosure 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.

[0050] 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.

[0051] 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 carrier medium may comprise a storage medium such as 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.

[0052] BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Embodiments of the invention will now be described, by way of example only, and with reference to the following drawings in which:

[0054] Figure 1 illustrates a typical 802.11 network environment involving ML transmissions between MLDs in which power management (PM) may be handled at MLD level; Figure 2 illustrates, using a flowchart, general steps of a communication method according to embodiments, that allows power management (PM) of non-AP STA, in particular activation of PM, to be handled at MLD level;

[0055] Figure 3 illustrates alternate formats of a Common Info field for signalling Multiple PerLink PM support according to embodiments;

[0056] Figure 4 illustrates an exemplary frame format of a proposed new protected Ultra High Reliability (UHR) Action frame that includes a Control field;

[0057] Figures 5a and 5b illustrate the use and possible adaptation of the existing frame format of the Enhanced Multi-Link (EML) Operating Mode (OM) Notification frame as defined in the IEEE P802.11 be™ / D5.1 standard, when used by an affiliated non-AP STA as an UHR Notification frame to activate or deactivate a Per-Link PM mechanism on behalf of another affiliated non-AP STA, e.g. to activate at once multiple Per-Link PM mechanisms;

[0058] Figure 6 illustrates, using a flowchart, general steps of a communication method according to embodiments, that allows power management (PM) of non-AP STA, in particular deactivation of PM, to be handled at MLD level;

[0059] Figure 7 schematically illustrates an exemplary timeline of activation and deactivation of multiple per-link PM mechanisms at once, according to embodiments; and

[0060] Figure 8 shows a schematic representation of a wireless communication device in accordance with embodiments.

[0061] DETAILED DESCRIPTION OF EMBODIMENTS

[0062] 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. 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).

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] The 802.11 family of standards define various media access control (MAC) mechanisms to drive access to the wireless medium. They include the Enhanced Distributed Channel Access (EDCA) scheme in which each STA contends for access to the wireless medium, using backoff procedures. They also include the Multi-User (MU) schemes that supplement the EDCA scheme and that allows for instance a MU uplink (UL) transmission to be triggered by the AP (through a so-called trigger frame) when gaining access to the wireless medium. During the MU UL transmission, various non-AP STAs can simultaneously transmit data to the AP over resource units (RUs the allocation of which to the STAs is indicated in the trigger frame).

[0068] The D5.1 standard 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.

[0069] 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 a 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 a MLD where each STA affiliated with the MLD is a non-AP STA, referred to as “affiliated non-AP STA”. Depending on the literature, “multilink device”, “ML Device” (MLD), “multilink logical entity”, “ML logical entity” (MLE), “multilink set” and “ML set” are synonyms to designate the same type of ML Device.

[0070] In operation, multiple affiliated non-AP STAs of a non-AP MLD set up communication links with multiple affiliated APs of an AP MLD, hence forming a multi-link channel for communication. Thanks to the multi-link aggregation, traffic associated with a single MLD can theoretically be transmitted across multiple parallel communication links, thereby increasing network capacity and maximizing utilization of available resources.

[0071] A setup link is defined as “enabled” for a non-AP MLD if at least one TID is mapped to that link either in downlink (DL) or in uplink (UL), meaning traffic data is assigned to such a link.

[0072] The links so 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).

[0073] A communication link or “link” thus corresponds to a given channel (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.

[0074] The affiliated APs and non-AP STAs operate on their respective link or channel 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.

[0075] From architecture point of view, a MLD contains typically several radios in order to implement its affiliated STAs. However, the number of actual radios is not necessarily equal to the number of STAs affiliated with the MLD. 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). Several Enhanced Multi-Link Operating Modes (or EML OMs in short) have been defined by the D5.1 standard to handle this architectural constrain, namely the Enhanced Multi-Link Single Radio (EMLSR) mode and the Enhanced Multi-Link Multi Radio (EMLMR) mode.

[0076] In the D5.1 standard, the two EMLSR and EMLMR modes have been made mutually exclusive. Indeed, the standard rules that for a non-AP MLD, the EMLSR Support subfield to declare EMLSR capability is set to 0 if the EMLMR Support subfield is set to 1 , and correspondingly, the EMLMR Support subfield to declare EMLMR capability is set to 0 if the EMLSR Support subfield is set to 1 .

[0077] Any non-AP MLD declares such support of the EMLSR or EMLMR mode (in its so-called EML Capabilities field including the above subfields) to the AP MLD during the association phase.

[0078] In operation mode, the activation or enabling of the EMLSR or EMLMR Mode is initiated by the non-AP MLD which transmits a specific protected EHT Action frame referred to as “EML Operating Mode Notification” (EML OM Notification), indicating in particular the set of enabled links (so-called EMLSR or EMLMR links) in which the EMLSR or EMLMR mode to activate is applied. More precisely (as explained below with reference to Figure 5a), a non-AP STA affiliated with the non-AP MLD transmits an EML Operating Mode Notification frame to an AP affiliated with its associated AP MLD with the EMLSR (resp. EMLMR) Mode subfield of the EML Control field set to 1 to indicate activation. Furthermore, the EMLSR / EMLMR Link Bitmap subfield of the EML Control field is filled in by setting the bit position(s) corresponding to the link ID value(s) of the EMLSR (resp. EMLMR) link(s) in the EMLSR (resp. EMLMR) Link Bitmap subfield to 1 , to signal which link(s) are to be used for the enabled mode.

[0079] As a response to a received EML Operating Mode Notification frame, an AP affiliated with the AP MLD ready to serve the non-AP MLD in the EMLSR or EMLMR operation transmits an EML OM Notification frame set to the same value as the EML Control field in the received EML OM Notification frame.

[0080] Similarly, the deactivation or disabling of the EMLSR or EMLMR Mode is initiated by the non-AP MLD which transmits an EML OM Notification. More precisely, a non-AP STA affiliated with the non-AP MLD transmits an EML OM Notification frame to an AP affiliated with its associated AP MLD with the EMLSR (resp. EMLMR) Mode subfield of the EML Control field set to 0.

[0081] As a response to a received EML OM Notification frame, an AP affiliated with the AP MLD transmits an EML OM Notification frame set to the same value as the EML Control field in the received EML OM Notification frame

[0082] The EMLSR mode, once activated, allows the non-AP MLD to listen to the EMLSR links simultaneously, waiting for an Initial Control Frame (ICF) sent by the AP MLD in the non-HT PPDU or non-HT duplicate PPDU format using a rate of 6 Mb / s, 12 Mb / s, or 24 Mb / s, i.e., in a format requiring few transmission (radio) resources. The ICF, once received, is followed by a frame exchange with two or more spatial streams on the link on which the ICF was received, hence requiring more transmission (radio) resources. Originally, the set of EMLSR links was made of two or more enabled links. It is now (in the last developments of the standard) possible to operate the EMLSR mode on a single EMLSR link. In such a case, the EML OM is referred to as Single Link EMLSR.

[0083] An AP which supports the Single Link EMLSR feature indicates this support (or capability) in the management frames exchanged during the ML discovery and more precisely sets a so- called “EMLSR Enablement On One Link Support” subfield to 1. This subfield is provided in the so-called “Extended MLD Capabilities And Operations” subfield of the Common Info field of the Basic Multi-Link element in all Management frames that include the Basic Multi-Link element, except Authentication frames exchanged during the association procedures.

[0084] When a non-AP MLD receives from an associated AP MLD a Basic Multi-Link element with the “EMLSR Enablement On One Link Support” subfield set to 1 , the non-AP MLD is allowed to set a single bit position to 1 in the above-mentioned EMLSR / EMLMR Link Bitmap subfield of the EML OM Notification frame, when the non-AP MLD desires to enable / activate the EMLSR mode on one single EMLSR link.

[0085] In absence of EMLSR Enablement On One Link Support by the AP MLD, the non-AP MLD cannot set a single bit position to 1 in the EMLSR / EMLMR Link Bitmap subfield, meaning it shall operate the EMLSR mode with two or more EMLSR links.

[0086] It may be noted that the “EMLSR Enablement On One Link Support” subfield has not to be used by a non-AP MLD in the declaration of its capabilities. That is why, in the standard, this subfield is reserved in all Management frames transmitted by a non-AP MLD during the association procedure.

[0087] Due to the difference of transmission (radio) resources needed for receiving the ICF from the AP MLD and for subsequently performing the frame exchange, the Single Link EMLSR feature can be used by a non-AP MLD as a Power Management (PM) mechanism on the corresponding link. It is therefore a Per-Link PM mechanism that can be activated (enabled) or deactivated (disabled) by the concerned affiliated non-AP STA, transmitting for example a frame request to its associated affiliated AP.

[0088] Handling power management at the MLD level rather than at link level would be profitable to wireless networks. In particular, signalling costs can be reduced.

[0089] For example, it would be profitable if it is possible for a first affiliated non-AP STA to activate or deactivate any Per-Link PM mechanism for one or more second (and different) affiliated non-AP STAs of the same non-AP MLD. Indeed, the first affiliated non-AP STA would transmit only one single notification frame with the effect of activating or deactivating a Per-Link PM mechanism for another non-AP STA, and even at once multiple Per-Link PM mechanisms involving multiple affiliated non-AP STAs of the same non-AP MLD.

[0090] To that end and as described in the present disclosure, a communication method in a wireless network can be proposed where a non-AP MLD sends one notification frame to an AP MLD to enable or disable power management (PM) on at least an enabled link between another non-AP STA of the non-AP MLD and the AP MLD. Preferably, the notification frame enables or disables PM on multiple enabled links with the AP MLD.

[0091] It turns out that the non-AP MLD can apply a PM mechanism on each of those multiple links, be them the same PM mechanism over the links or different ones as explained below. Not only the Single Link EMLSR feature can be used as PM mechanism to implement at link level, but also the legacy Per-Link PM mechanisms, e.g., TIM (Traffic Indication Map)-based mechanisms and SMPS mechanism.

[0092] Figure 1 illustrates a typical 802.11 network environment involving ML transmissions between MLDs in which PM may be handled at MLD level.

[0093] 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 EML capable and have declared their corresponding capabilities to the AP MLD 110, within the EMLSR-related fields and EMLMR-related fields of the EML Capabilities. Of course, any other number of non-AP MLDs registering to the AP MLD 110 and then exchanging frames with it may be contemplated, as well as another (greater) number of EML-capable non-AP MLDs.

[0094] AP MLD 110 has multiple affiliated APs, two affiliated APs 11 1 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.

[0095] 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 1 12) to which it registers. 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.

[0096] 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 38 corresponding to an operating 40 MHz channel in the 5 GHz frequency band and AP 112 is set to operate on channel 159 corresponding to another operating 40 MHz channel in the 5 GHz frequency band too. In another example, the affiliated STAs could operate on different frequency bands and / or with different bandwidths than 40 MHz.

[0097] Each affiliated AP offers a link towards 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. In this context, each of the affiliated APs 111 and 112 can be identified by an identifier referred to as “link ID”. The link ID of each affiliated AP is unique and does not change during the lifetime of the AP MLD. AP MLD may assign the link ID to its affiliated APs by incrementing the IDs from 0 (for the first affiliated AP). Correspondingly, each affiliated non-AP STA can also be uniquely identified through the corresponding link ID. In the above example of the EMLSR / EMLMR Link Bitmap, there is therefore a unique matching between an affiliated non-AP STA (identified by its link ID) and the corresponding link-IDthbit in the bitmap (bit having position equal to link ID).

[0098] To perform multi-link communications, each non-AP MLD 120, 130 discovers, authenticates, associates and sets up multiple links with AP MLD 1 10 during the association procedure, each link being established between an affiliated AP of AP MLD 110 and an affiliated non-AP STA of the non-AP MLD concerned. 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.

[0099] The discovery phase is referred below to as MLO discovery procedure, and the multi-link setup phase (or association phase) is referred below to as ML setup procedure.

[0100] The MLO 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. 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 AP MLD 110 to set up these links, 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.

[0101] 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), a second link 152 between affiliated AP 112 (AP2) and affiliated non-AP STA 122 (A2). Similarly, two candidate setup links have been requested by multi-radio non-AP MLD 130 and accepted by AP MLD 1 10: a first link 161 between affiliated AP 111 (AP1) and affiliated non-AP STA 131 (B1), a second link 162 between affiliated AP 112 (AP2) and affiliated non-AP STA 132 (B2).

[0102] During the ML setup procedure, the non-AP MLDs declare part or all of their capabilities. For instance, they may declare their EML capability. 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 Element specific to the Multi-Link Operation (MLO), referred to as Basic Multi-Link element. De facto, in all Management frames that include a Basic Multi-Link element except Authentication frames, a non-AP or AP MLD which is EMLSR or EMLMR capable sets the EMLSR or EMLMR Support bit to 1 , in the EML Capabilities subfield of the Common Info field within the Basic Multi-Link element. In the same way, an AP MLD that supports the Single Link EMLSR feature sets the “EMLSR Enablement On One Link Support” subfield to 1 , in the “Extended MLD Capabilities And Operations” subfield of the Common Info field.

[0103] Once the links have been set up and the respective capabilities of the MLDs are known from each other, the AP MLD and the non-AP MLDs can operate on the links using the known (e.g., PM, channel access) mechanisms.

[0104] Figure 2 illustrates, using a flowchart, general steps of a communication method according to embodiments, that allows power management (PM) of non-AP STA, in particular activation of PM, to be handled at MLD level. The flowchart is performed at a non-AP MLD.

[0105] At step 200, the non-AP MLD declares its capabilities to the AP MLD, in particular its capability to handle PM at MLD level. To do so, at step 200, the non-AP MLD signals, to the AP MLD, a Multiple Per-Link PM support (or capability) of the non-AP MLD. Either affiliated non-AP STA of the non-AP MLD can send the signalling frame(s) to the AP MLD.

[0106] The Multiple Per-Link PM support means that the affiliated non-AP STAs of the non-AP MLD can notify the AP MLD about an activation or deactivation of a Per-Link PM mechanism on behalf of any other affiliated non-AP STA of the same non-AP MLD.

[0107] Figure 3 illustrates alternate embodiments for signalling Multiple Per-Link PM support.

[0108] These embodiments provide signalling within the Common Info field 300 of a Basic MultiLink element provided when associating with the AP MLD. In particular, such field 300 is transmitted in all Management frames that include a Basic Multi-Link element except Authentication frames transmitted by the non-AP MLD. Of course, any other field could be defined to carry the signalling of Multiple Per-Link PM support.

[0109] In a first embodiment, the Multiple Per-Link PM support is signalled using one bit of an Enhanced Multi-Link (EML) Capabilities subfield in a Common Info field of a Basic Multi-Link element, in particular any of bits B8-B10 and B15.

[0110] As shown in the Figure, a one-bit subfield 315 (here bit B8) in the EML Capabilities subfield 310 of Common Info field 300 of the Basic Multi-Link element is renamed as “Multiple Per-Link PM Support” subfield to indicate whether the non-AP MLD supports that its affiliated non- AP STAs activate / d eactivate PM on behalf of another affiliated non-AP STA. In one embodiment, the bit may indicate whether the non-AP MLD supports at once of multiple Per-Link PM mechanism, implicitly meaning the non-AP STA sending the management frame operates on behalf of at least one other affiliated non-AP STA of the same non-AP MLD.

[0111] The Multiple Per-Link PM Support subfield 315 may be set to 1 in case of support and set to 0 in case of absence of support.

[0112] As only the non-AP MLDs send their capability for Multiple Per-Link PM Support, the Multiple Per-Link PM Support subfield 315 remains a reserved bit when the Basic Multi-Link element containing the Common Info field 300 is transmitted by an AP MLD.

[0113] In the other embodiments below, Multiple Per-Link PM Support subfield 315 is no longer used and thus it remains a reserved bit. In second and third embodiments, the Multiple Per-Link PM support is signalled using one bit of an Extended MLD Capabilities And Operations subfield 320 in the Common Info field 300 of the Basic Multi-Link element, in particular any of bits B6 (used by the AP MLD to signal support of EMLSR Enablement On One link, i.e., Single Link EMLSR) and B7-B15 (reserved bits).

[0114] In the second embodiment, a one-bit subfield 325 is added to the existing fields 321 , 322, 323, 324 (according to the D5.1 Standard) in the Extended MLD Capabilities And Operations subfield 320 of the Common Info field 300 of the Basic Multi-Link element, in order to signal the support or not of the activation / deactivation of PM on behalf of another affiliated non-AP STA (or support at once of multiple Per-Link PM mechanisms). Any of bits B7-B15 can be used. In the Figure, B7 is used for that one-bit subfield 325 which is referred to as “Multiple Per-Link PM Support” subfield.

[0115] Like in the first embodiment, Multiple Per-Link PM Support subfield 325 may be set to 1 in case of support and set to 0 in case of absence of support.

[0116] As only the non-AP MLDs send their capability for Multiple Per-Link PM Support, the Multiple Per-Link PM Support subfield 325 remains a reserved bit when the Basic Multi-Link element containing the Common Info field 300 is transmitted by an AP MLD.

[0117] In the third embodiment, the legacy “EMLSR Enablement On One Link Support” one-bit subfield 324 is reused to signal the support or not of the activation / deactivation of PM on behalf of another affiliated non-AP STA (or support at once of multiple Per-Link PM mechanisms). It is bit B6 in the Extended MLD Capabilities And Operations subfield 320 of the Common Info field 300 of the Basic Multi-Link element. As mentioned above, this subfield in the legacy format is not used by a non-AP MLD in the declaration of its capabilities because the Single Link EMLSR feature is only declared by the AP MLDs. It is proposed to take advantage of this situation to optimize the signalling by saving the use of a reserved bit.

[0118] Subfield 324 may be renamed “EMLSR Enablement On One link I Multiple Per-Link PM Support” subfield, as shown in the Figure.

[0119] Like in the preceding embodiments, subfield 324 may be set to 1 in case of support and set to 0 in case of absence of support.

[0120] In some embodiments supplementing the above embodiments, parameters regarding the PM mechanism to activate or deactivate may be provided simultaneously to the support declaration. For instance, any above signalling of the Multiple Per-Link PM support is made together with a signalling of one or more PM mechanisms (or schemes) supported (i.e., available) by the non-AP MLD.

[0121] As shown in the Figure, an additional subfield 326, referred to as Multiple Per-Link PM subfield, may be provided in the reserved bits (B7-B15) of the Extended MLD Capabilities And Operations subfield 320. In the Figure, bits B8 and B9 are used due to the presence of subfield 325 (second embodiments). However, bits B7 and B8 can be used when B7 is not used for subfield 325. Note that in variants, reserved bits of the EML Capabilities subfield 310 can be used instead. Although the present example used two bits for Multiple Per-Link PM subfield 326, any other number of bits can be used.

[0122] In particular embodiments, Multiple Per-Link PM subfield 326 conveys a value identifying a single supported PM mechanism. It means one and the same PM mechanism applies for all enabled links with the AP MLD when PM activation or deactivation is triggered. In an example, Multiple Per-Link PM subfield 326 is coded on two bits taking four values, 0,1 ,2,3. It is set to 0 to indicate that the Per-Link PM mechanism is the Single Link EMLSR. It is set to 1 to indicate that the Per-Link PM mechanism is a Spatial Multiplexing Power Save (SMPS) mechanism as specified in the standard IEEE Std 802.11 -2020. It is set to 2 to indicate that the Per-Link PM mechanism is the legacy TIM-based PM mechanism specified in section 11.2.3 in the standard IEEE Std 802.11-2020. Value 3 may be “reserved” or used for any other PM mechanism.

[0123] In variants to subfield 326 containing a single value, Multiple Per-Link PM subfield 326 may be a bitmap to declare all PM mechanisms that the non-AP MLD wishes to be available. For example, the first bit is enabled to make the Single Link EMLSR mechanism available, the second bit is enabled to make the SMPS mechanism available, and the third bit is enabled to make the TIM-based PM mechanism available. In that way, one or more supported PM mechanisms can be signalled once for all enabled links with the AP MLD.

[0124] Although these examples signal PM mechanisms once for all links, variants may be used with multiple subfields within Multiple Per-Link PM subfield 326 to separately signal PM mechanism or mechanisms per link. In other words, one or more supported PM mechanisms are signalled per each enabled link with the AP MLD.

[0125] In some embodiments, the AP MLD supports by default the activation / deactivation on behalf of another affiliated non-AP STA, and possibly at once of multiple Per-Link PM mechanisms.

[0126] Back to Figure 2, once the declaration of Multiple Per-Link PM support has been made by the non-AP MLD, the latter operates in the wireless network in a conventional manner.

[0127] It may however decide to activate power management of one or more of its affiliated non- AP STAs not using the conventional Per-Link PM activation signalling, but the one of the present disclosure. This is step 210. In particular, one affiliated non-AP STA (below “sending” affiliated non-AP STA) is designated to notify the AP MLD to enable PM on at least another link that its own one. “To enable PM” may mean activating PM for one or more links which do not currently operate under PM, but also modifying a currently activated PM. Modifying a currently activated PM may include, inter alia, modifying the set of links concerned by the PM, modifying the PerLink PM mechanism to be implemented as PM on the links.

[0128] To do the PM enablement, it sends a notification frame, that may be referred to as UHR Notification frame (UHR or “Ultra High Reliability” making reference to 802.1 1 bn under drafting).

[0129] Multiple notification frames can be sent to activate PM on different subsets of links, for example when each notification frame signals a specific PM mechanism to apply, which PM mechanism is different from one subset of links to the other. As an illustration, the Single Link EMLSR feature may be enabled as PM mechanism on links 1 and 3, while the SMPS mechanism is activated on link 2.

[0130] As described below, some embodiments reuse an existing protected Action frame, while other embodiments propose to rely on a new type of protected Action frame in the meaning of the 802.11 standards.

[0131] Figure 4 illustrates an exemplary frame format of a proposed new protected Ultra High Reliability (UHR) Action frame that includes a Control field, referred to as “EML PM Control” field or “UHR PM Control” field because it provides information per link as described below.

[0132] In the UHR PM Notification frame relies on EML-related fields, it may also be referred to as an EML PM Notification frame.

[0133] The Action field of the EML PM Notification contains the following information:

[0134] The Category field specified is set to a value / code indicating that the EML PM Notification is a protected UHR Action frame (a value between 40 and 125).

[0135] The Protected UHR Action field is set to value / code indicating that the protected UHR Action frame is an EML PM Notification. For illustrative purpose, value 0 is selected.

[0136] The Dialog Token field is set to a nonzero value to identify the request / response transaction.

[0137] The EML PM Control field 400 is described as illustrated in Figure 4. It contains a Multiple Per-Link PM Mode subfield 410, a Multiple Per-Link PM Link Bitmap subfield 420 and a Per-Link PM Parameters subfield 430.

[0138] In some embodiments, subfields 420 and 430 are optional, in particular for an EML PM Notification that deactivates PM, because it may be decided to deactivate all the pending PM at the requesting non-AP MLD. More generally, parameter subfield 430 may be optional, in particular when there is no PM parameter to be transmitted (e.g., they are predefined).

[0139] EML PM Control field 400 includes a subfield taking a first value to signal enabling of PM on at least one enabled link of another affiliated non-AP STA than the sending STA, or a second value to signal disabling of PM on the at least one link. For example, Multiple Per-Link PM Mode subfield 410 is a 1 -bit subfield. It is set to 1 when the sending STA of the non-AP MLD requests to activate or enable PM on behalf of another affiliated non-AP STA, e.g., to activate or enable at once multiple Per-Link PM mechanisms. Otherwise (deactivate or disable), it is set to 0.

[0140] In step 210 of the process of Figure 2, Multiple Per-Link PM Mode subfield 410 is set to EML PM Control field 400 also includes a bitmap subfield signalling the at least one link for PM enabling or disabling from amongst a plurality of enabled links with the AP MLD. For example, Multiple Per-Link PM Link Bitmap subfield 420 is a 0 (hence optional) or 16-bit subfield.

[0141] When the non-AP MLD requests to activate or enable PM on behalf of any other affiliated non-AP STA, e.g., to activate or enable at once multiple Per-Link PM mechanisms, Multiple PerLink PM Link Bitmap subfield 420 indicates the set of the enable links for which it is requested the activation or enablement of a Per-Link PM mechanism.

[0142] Signalling through the bitmap may be as follows: bit having position i within the Multiple Per-Link PM Link Bitmap subfield corresponds to the link with the Link ID equal to i. It is set to 1 to indicate that the activation of a Per-Link PM mechanism is requested for that link.

[0143] Assuming the sending STA corresponds to Link ID ‘j’, setting bit j to 1 means the sending STA requests activation of a Per-Link PM mechanism for itself; setting bit i j) to 1 means the sending STA requests activation of a Per-Link PM mechanism on behalf of another affiliated non- AP STA (the one corresponding to Link ID i); setting multiple bits of the bitmap to 1 means the activation of multiple Per-Link PM mechanisms is requested for multiple affiliated non-AP STAs of the non-AP MLD.

[0144] It is recalled that Multiple Per-Link PM Link Bitmap subfield 420 may be optional, in particular in case of deactivation. For example, when the non-AP MLD requests to deactivate or disable at once multiple Per-Link PM mechanisms, subfield 420 is not present. It means that the deactivation request is addressed to all pending links on which a Per-Link PM mechanism is currently activated.

[0145] EML PM Control field 400 may also (however this may be optional) includes a parameter subfield. Such subfield may signal parameters for the multiple Per-Link PM mechanisms, such as one or more PM mechanisms that are enabled or disabled on the one or more link signalled in bitmap 420. Also, this subfield may indicate a configuration switch delay defining a duration required by the non-AP MLD to configure an affiliated non-AP station when switching between a low-power configuration and a high-power configuration, e.g., from low-power configuration to high-power configuration.

[0146] To illustrate that, Figure 4 shows an exemplary implementation where Per-Link PM Parameters subfield 430 is the parameter subfield with a variable length.

[0147] In a first implementation, it comprises Multiple Per-Link PM subfield 431 and a set 432 of one or more Per-Link PM Parameters fields 440, one for each link for which it is requested an activation or a deactivation.

[0148] This implementation is used to save signalling bits when the same Per-Link PM mechanism is to be activated or deactivated for all the links signalled in bitmap 420. Multiple PerLink PM subfield 431 may be filled in as described above for Multiple Per-Link PM subfield 325. For example, it is a two-bit subfield set to 0 to indicate the Single Link EMLSR feature, set to 1 to indicate the Spatial Multiplexing Power Save (SMPS) mechanism, or set to 2 to indicate the legacy TIM-based PM mechanism. In a second and alternate implementation, it only comprises a set 432 of one or more PerLink PM Parameters fields 440, one for each link for which it is requested an activation or a deactivation. This implementation can be used to signal different Per-Link PM mechanisms for the different links signalled in bitmap 420, in particular to signal one Per-Link PM mechanism per signalled link.

[0149] The one or more Per-Link PM Parameters fields 440 in the set 432 are organized in the order of the enabled bits within bitmap 420: the first Per-Link PM Parameters field 440 is for the link (or associated non-AP STA) corresponding to the first bit set to 1 in bitmap 420, and so on.

[0150] Each Per-Link PM Parameters field 440 corresponds to a set of parameters to perform the activation or deactivation of a Per-Link PM mechanism on the requested link.

[0151] A large number of parameters can be transmitted using dedicated subfields within field 440.

[0152] As an example, when the requested Per-Link PM mechanism is the Single Link EMLSR feature for the link concerned by Per-Link PM Parameters field 440, the latter may contain an EMLSR Padding Delay subfield 441 and an EMLSR Transition Delay subfield 442 as they are specified in the D5.1 standard.

[0153] As another example, subfields 441 and 442 (conventionally known as Padding Delay subfield and Transition Delay subfield), or any other subfield, may be used to indicate a configuration switch delay needed by the affiliated non-AP STAs to configure themselves when switching between a low-power configuration and a high-power configuration. Indeed, an affiliated non-AP STA implementing PM may be configured on a 20 MHz channel in a low-power configuration and may need to transition to (or transition back from) an 80 MHz radio configuration for high power operations, e.g., after a 20MHz ICF is received from the AP MLD to trigger an 80MHz frame exchange. The configuration switch delay so signalled to the AP MLD may allow the AP MLD to add padding data (in a padding field) in the triggering ICF frame to give more time to the affiliated non-AP STA receiving the ICF frame to change its bandwidth (BW) configuration and use SIFS to check CCA on the bandwidth for the frame exchange (TXOP BW)-

[0154] The two subfields 441 and 442 may for instance be used to indicate durations to be taken into account, respectively when switching from low-power configuration to high-power configuration and when switching back from high-power configuration to low-power configuration. The two values may be identical. However, switching to high-power configuration may be more demanding than switching back to low-power configuration, and the values may thus be different one from the other. As an example related to the Single Link EMLSR feature, Padding Delay subfield 441 is dedicated to the switching to high-power configuration and its value is set so that the corresponding padding delay plus the duration of a FCS subfield in the ICF plus the SIFS between the ICF and the ICF response matches a predefined first duration (defined for switch to high-power configuration). In the same way, Transition Delay subfield 442 is dedicated to the switching back to low-power configuration and its value is set so that the corresponding transition matches a predefined second duration (defined for switch back). As shown in the Figure, optional Multiple Per-Link PM subfield 443 is used when subfield 431 is not used, to signal one Per-Link PM mechanism per signalled link. Multiple Per-Link PM subfield 443 may be filled in as described above for subfield 325 or 431 : for example, it is a two- bit subfield set to 0 to indicate the Single Link EMLSR feature, set to 1 to indicate the Spatial Multiplexing Power Save (SMPS) mechanism, or set to 2 to indicate the legacy TIM-based PM mechanism.

[0155] Figures 5a and 5b illustrate the use and possible adaptation of the existing frame format of the Enhanced Multi-Link (EML) Operating Mode (OM) Notification frame (an existing protected Action frame) as defined in the IEEE P802.11 be™ / D5.1 standard, when used by an affiliated non- AP STA as an UHR Notification frame to activate (or deactivate as described below) a Per-Link PM mechanism on behalf of another affiliated non-AP STA, e.g., to activate at once multiple PerLink PM mechanisms.

[0156] Like the new Action frame of Figure 4, this UHR PM Notification frame relies on EML- related fields and may be referred to as an EML PM Notification frame.

[0157] As known, an EML OM Notification frame includes an EML Control field 500 comprising EMLSR Mode subfield 501 (bit B0), EMLMR Mode subfield 502 (bit B1), EMLSR Parameter Update Control subfield 503 (bit B2), In-Device Coexistence Activities subfield 504 (bit B3), set

[0158] 505 of bits B4-B7 not used in the D5.1 standard, EMLSR / EMLMR Link Bitmap subfield 506 (0 or 16 bits), MCS Map Count Control subfield 507 (0 or 8 bits) and EMLMR Supported MCS And NSS Set subfield 508 (variable length).

[0159] Both embodiments of Figures 5a and 5b uses the EMLSR / EMLMR Link Bitmap subfield

[0160] 506 of the EML Control field according to the IEEE P802.11 be™ / D5.1 standard, to signal with link or links are concerned by the activation (or deactivation) signalled through the EML PM Notification frame. The same signalling as for bitmap 420 can be used. The standardized EMLSR / EMLMR Link Bitmap subfield can therefore be renamed EMLSR / EMLMR I Multiple PerLink PM Link Bitmap subfield, as shown in the Figures.

[0161] Also, both embodiments of Figures 5a and 5b may signal parameters in a parameter subfield when appropriate, typically using an additional (to conventional fields) Per-Link PM Parameters subfield 530 similar to subfield 430 described above (Figure 4).

[0162] As apparent from the above, Per-Link PM Parameters subfield 530 allows the non-AP MLD to signal one or more PM mechanisms that are enabled (or disabled) on one or more links signalled in bitmap 506. A subfield such as Multiple Per-Link PM subfield 431 can be used to signal a single PM mechanism that is enabled or disabled on all the links set to 1 in bitmap 506. Subfields such as Multiple Per-Link PM subfields 443 repeated in each Per-Link PM Parameters fields 440 can be used to signal a PM mechanism to enable or disable per link of all the links set to 1 in bitmap 506.

[0163] Per-Link PM Parameters subfield 530 may include conventional EMLSR Padding Delay (such as subfield 441) and EMLSR Transition Delay (such as subfield 442). Per-Link PM Parameters subfield 530 may also allow the non-AP MLD to indicate a configuration switch delay defining a duration required by the non-AP MLD to configure an affiliated non-AP station when switching between a low-power configuration and a high-power configuration.

[0164] Embodiments of Figures 5a and 5b distinguish one from the other by the way they signal PM activation or deactivation.

[0165] In the embodiment of Figure 5a, an additional subfield, referred to as Multiple Per-Link PM Mode subfield 510, is provided within the conventional frame format. As shown in the Figure, Multiple Per-Link PM Mode subfield 510 is included in the standardized 4-bit reserved field 505 of the EML Control field 500. Multiple Per-Link PM Mode subfield 510 may be any bit B4 to B7. In the Figure, bit B4 is used.

[0166] Multiple Per-Link PM Mode subfield 510 is set to 1 when the non-AP MLD requests to activate or enable PM on behalf of another affiliated non-AP STA, e.g., to activate or enable at once multiple per-link PM mechanisms. Bitmap 506 is filled in in the same way as bitmap 420: each bit T is enabled when PM is to be activated on the link having Link ID ‘i ’.

[0167] Multiple Per-Link PM Mode subfield 510 is set to 0 when the non-AP MLD requests to deactivate or disable PM on behalf of another affiliated non-AP STA, e.g., to deactivate or disable at once multiple per-link PM mechanisms.

[0168] In step 210 of the process of Figure 2, Multiple Per-Link PM Mode subfield 510 is set to 1.

[0169] In the embodiment of Figure 5b, EMLSR Mode subfield 501 and / or EMLMR Mode subfield 502 can be reused to save signalling bits. In that case, they can be renamed EMLSR Mode I Multiple Per-Link PM Mode subfield 551 and EMLMR Mode I Multiple Per-Link PM Mode subfield 552, respectively.

[0170] This is because the same non-AP MLD cannot support both EMLSR and EMLMR modes simultaneously, as recalled above. It turns out that EMLSR Mode subfield 501 and / or EMLMR Mode subfield 502 are not both used simultaneously. Depending on which mode is supported (as declared through EMLSR Support and EMLMR Support fields of Figure 3), the Mode subfield 501 / 502 of the other (hence non-supported) mode is not used, and can be reused to signal the activation (or deactivation) of Multiple Per-Link PM.

[0171] The table below summarizes the situation that can be encountered depending on the supported mode.

[0172] The table shows that the bit to signal activation (or deactivation) of Multiple Per-Link PM is the EMLSR Mode bit 551 if the non-AP MLD declares it supports EMLMR operation or is the EMLMR Mode 552 bit if the non-AP MLD declares it supports EMLSR operation.

[0173] In more details, if the non-AP MLD supports neither the EMLSR mode nor the EMLMR mode, and supports the Multiple Per-Link PM mode (first line of the table), the EMLSR Mode I Multiple Per-Link PM Mode subfield 551 corresponds to a Multiple Per-Link PM Mode subfield to signal the activation (or deactivation) of Multiple Per-Link PM, and the EMLMR Mode I Multiple Per-Link PM Mode subfield 552 is unused. Of course, the reverse (subfield 552 is used instead of 551) may be contemplated.

[0174] In step 210 of the process of Figure 2 where none of the EMLSR and EMLMR mode are supported, EMLSR Mode I Multiple Per-Link PM Mode subfield 551 is thus set to 1 .

[0175] If the non-AP MLD supports the EMLSR mode, and supports neither the EMLMR mode nor the Multiple Per-Link PM mode (second line), the EMLSR Mode I Multiple Per-Link PM Mode subfield 551 corresponds to the conventional EMLSR Mode subfield and the EMLMR Mode I Multiple Per-Link PM Mode subfield 552 is unused. This is the conventional approach when the EMLSR mode is supported.

[0176] If the non-AP MLD supports the EMLSR mode and the Multiple Per-Link PM mode, and does not support the EMLMR mode (third line), the EMLSR Mode I Multiple Per-Link PM Mode subfield 551 corresponds to the conventional EMLSR Mode subfield and the EMLMR Mode I Multiple Per-Link PM Mode subfield 552 corresponds to a Multiple Per-Link PM Mode subfield to signal the activation (or deactivation) of Multiple Per-Link PM.

[0177] In step 210 of the process of Figure 2 where the EMLSR mode is supported, EMLMR Mode I Multiple Per-Link PM Mode subfield 552 is thus set to 1 .

[0178] If the non-AP MLD supports the EMLMR mode, and supports neither the EMLSR mode nor the Multiple Per-Link PM mode (fourth line), the EMLSR Mode I Multiple Per-Link PM Mode subfield 551 is not used and the EMLMR Mode I Multiple Per-Link PM Mode subfield 552 corresponds to the conventional EMLMR Mode subfield. This is the conventional approach when the EMLMR mode is supported.

[0179] If the non-AP MLD supports the EMLMR mode and the Multiple Per-Link PM mode, and does not support the EMLSR mode (fifth line), the EMLSR Mode I Multiple Per-Link PM Mode subfield 551 corresponds to a Multiple Per-Link PM Mode subfield to signal the activation (or deactivation) of Multiple Per-Link PM and the EMLMR Mode / Multiple Per-Link PM Mode subfield 552 corresponds to the conventional EMLMR Mode subfield.

[0180] In step 210 of the process of Figure 2 where the EMLMR mode is supported, EMLSR Mode / Multiple Per-Link PM Mode subfield 551 is thus set to 1 . In other words, when the Multiple Per-Link PM Mode subfield (implemented in either of subfield 551 or 552) is present, it is set to 1 when the non-AP MLD requests to activate or enable PM on behalf of another affiliated non-AP STA, e.g., to activate or enable at once multiple PerLink PM mechanisms. Bitmap 506 (hence corresponding to a Multiple Per-Link PM Link Bitmap) is filled in in the same way as bitmap 420: each bit T is enabled when PM is to be activated on the link having Link ID ‘i’.

[0181] The Multiple Per-Link PM Mode subfield is set to 0 when the non-AP MLD requests to deactivate or disable PM on behalf of another affiliated non-AP STA, e.g., to deactivate or disable at once multiple Per-Link PM mechanisms.

[0182] In an embodiment, when the two Mode subfields (either 501 / 502 and 510, or 551 and 552) are set to 1 (meaning both the supported EML mode and the Multiple Per-Link PM mode are activated through the same notification frame), an additional bitmap may be provided in the EML Control field 550 to signal the links on which a Per-Link PM mechanism is activated, and bitmap 506 remains the bitmap to signal the links affected by the activated EML mode. In embodiments, the two bitmaps have subsets of links set to 1 that are disjoints.

[0183] Back to Figure 2, once the non-AP MLD has signalled the activation of the Multiple PerLink PM mode to the AP MLD, with an indication of the link or links concerned, the non-AP MLD operates (step 220) on the multiple enabled links with the AP MLD, taking into account the power management specific to each link, if any. For example, an affiliated non-AP STA of a link on which a Per-Link PM mechanism is activated operates in a low-power configuration, e.g., over a 20 MHz channel, up to receiving an ICF from the AP MLD. This announces a frame exchange; hence the affiliated non-AP STA switches (in response to the ICF) to a high-power configuration, e.g., to operate on an 80 MHz channel.

[0184] In some embodiments, the UHR Notification frame from the non-AP MLD is followed by a response frame from the AP MLD to acknowledge the activation of the Multiple Per-Link PM mode. In embodiments, the response frame is a UHR (or EML PM) Notification frame as described above, that includes the same EML Control field (400, 500 or 550) as the one of the UHR Notification frame from the non-AP MLD.

[0185] Figure 6 illustrates, using a flowchart, general steps of a communication method according to embodiments, that allows power management (PM) of non-AP STA, in particular deactivation of PM, to be handled at MLD level. The flowchart is performed at a non-AP MLD.

[0186] While the non-AP MLD operates with power management (such as in step 220), it may decide to deactivate power management of one or more of its affiliated non-AP STAs not using the conventional Per-Link PM activation signalling, but the one of the present disclosure. This is step 600. In particular, one affiliated non-AP STA (below “sending” affiliated non-AP STA) is designated to notify the AP MLD to disable PM on at least another link that its own one. To do so, it sends a UHR notification frame as described above, wherein the Multiple Per-Link PM Mode subfield (410, 510 or 551 / 552) is set to 0. In embodiments, if a specific Per-Link PM mechanism (field 431 or 443) is indicated in the UHR notification frame (either generally or at link level), the deactivation may concern those links on which this specific Per-Link PM mechanism is currently operative.

[0187] In embodiments, if a bitmap (506) is provided that signals some links, the deactivation may concern only those signalled links.

[0188] Next to step 600, the non-AP MLD operates (step 610) on the enabled links with the AP MLD, without any power management on the links on which the power management has been deactivated at step 600.

[0189] In some embodiments, the UHR Notification frame from the non-AP MLD is followed by a response frame from the AP MLD to acknowledge the deactivation of the Multiple Per-Link PM mode. In embodiments, the response frame is a UHR (or EML PM) Notification frame as described above, that includes the same EML Control field (400, 500 or 550) as the one of the UHR Notification frame from the non-AP MLD.

[0190] Figure 7 schematically illustrates an exemplary timeline of activation and deactivation of multiple Per-Link PM mechanisms at once, according to embodiments.

[0191] In this scenario, non-AP MLD 120 has declared to AP 110 its support to the activation / deactivation of PM on behalf of other affiliated non-AP stations, in particular the activation / deactivation at once of multiple Per-Link PM mechanisms (subfield 315 set to 1). AP 110 also supports the Multiple Per-Link PM mode.

[0192] Next, non-AP MLD 120 intends to activate at once multiple Per-Link PM mechanisms on its two links 151 , 152 enabled with the AP MLD. To that end, affiliated non-AP STA A1 121 transmits an EML PM Notification 700 to the AP MLD (affiliated AP1) with Multiple Per-Link PM Mode subfield (410, 510 or 551 / 552) set to 1 and a Multiple Per-Link PM Link Bitmap subfield in which the bits corresponding to the Link IDs of links 151 and 152 are set to 1 . In this example, the UHR notification frame 700 enables PM on the link 151 enabled between the affiliated non-AP STA 121 sending the notification frame and the AP MLD, in addition to PM on another link (152) on behalf of the other affiliated non-AP STA (122).

[0193] In addition, the Per-Link PM mechanism to activate, e.g., the Single Link EMLSR feature, may be signalled in Multiple Per-Link PM subfield 431 or 443.

[0194] As a response to the received EML PM Notification 700, affiliated AP1 111 of the AP MLD 110 may transmit an EML PM Notification 710 as soon as AP MLD 110 is ready to operate with non-AP MLD 120 with the multiple Per-Link PM mechanisms on the multiple links indicated in the Multiple Per-Link PM Link Bitmap subfield of the received EML PM Notification.

[0195] Affiliates non-AP STA A1 and A2 now operates on their respective links using power management, in accordance with the Per-Link PM mechanism that has been activated for them.

[0196] Similarly, when the non-AP MLD 120 for which multiple Per-Link PM mechanisms are enabled (on links 151 and 152) intends to deactivate these activated Per-Link PM mechanisms, the same affiliated non-AP STA 121 (however, another affiliated STA could be used in a variant) transmits an EML PM Notification 750 to the AP MLD 110 (affiliated AP1) with Multiple Per-Link PM Mode subfield (410, 510 or 551 / 552) set to 0. Again, an EML PM Notification 760 may be sent in response by the AP MLD (affiliated AP1) as soon as the latter is ready to deactivate all the activated per-link PM mechanisms.

[0197] Affiliates non-AP STA A1 and A2 now operates on their respective links without any power management.

[0198] Figure 8 schematically illustrates a communication device 800, 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 800 may preferably be a device such as a microcomputer, a workstation or a light portable device. The communication device 800 comprises a communication bus 813 to which there are preferably connected: a central processing unit 801 , such as a processor, denoted CPU; a memory 803 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 802 and 802’ connected to the wireless communication network, for example a communication network according to one of the IEEE 802.11 family of standards, via transmitting and receiving antennas 804 and 804’, respectively.

[0199] Preferably the communication bus 813 provides communication and interoperability between the various elements included in the communication device 800 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 800 directly or by means of another element of the communication device 800.

[0200] 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 802 or 802’, in order to be stored in the memory of the communication device 800 before being executed.

[0201] 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).

[0202] 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.

[0203] 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. 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 communication method in a wireless network, comprising, at a non-access point (non-AP) station (STA) affiliated with a non-AP multi-link device (MLD), sending one notification frame to an AP MLD to enable or disable power management (PM) on at least an enabled link between another non-AP STA of the non-AP MLD and the AP MLD.

2. The method of Claim 1 , wherein the notification frame enables or disables power management (PM) on multiple enabled links with the AP MLD.

3. The method of Claim 1 , wherein the notification frame enables or disables PM on the enabled link between the non-AP STA sending the notification frame and the AP MLD.

4. The method of Claim 1 , wherein the notification frame includes a bitmap signalling the at least one link for PM enabling or disabling from amongst a plurality of enabled links with the AP MLD.

5. The method of Claim 4, wherein the bitmap is signalled in the EMLSR / EMLMR Link Bitmap subfield of an EML Control field according to the IEEE P802.11 be™ / D5.1 standard.

6. The method of Claim 1 , wherein a bit in an EML Control field according to the IEEE P802.11 be™ / D5.1 standard takes a first value to signal enabling of power management on the at least one link or a second value to signal disabling of power management on the at least one link.

7. The method of Claim 6, wherein the bit is one from- bits B4-B7, the EMLSR Mode bit, and the EMLMR Mode bit.

8. The method of Claim 6, wherein the bit is the EMLSR Mode bit if the non-AP MLD declares it supports EMLMR operation or is the EMLMR Mode bit if the non-AP MLD declares it supports EMLSR operation.

9. The method of Claim 1 , wherein the notification frame signals one or more PM mechanisms that are enabled or disabled on the at least one link.

10. The method of Claim 9, wherein a PM mechanism is signalled per link of multiple links to enable or disable.

11. The method of Claim 9, wherein a single PM mechanism is signalled that is enabled or disabled on multiple links.

12. The method of Claim 1 , wherein the notification frame includes a configuration switch delay defining a duration required by the non-AP MLD to configure an affiliated non-AP station when switching between a low-power configuration and a high-power configuration.

13. The method of Claim 1 , wherein the notification frame is an Enhanced Multi-Link (EML) Operating Mode Notification frame as defined in the IEEE P802.11 be™ / D5.1 standard.

14. The method of Claim 1 , wherein the notification frame is a protected Ultra High Reliability (UHR) Action frame that includes a Control field comprising:a subfield taking a first value to signal enabling of PM on the at least one link or a second value to signal disabling of PM on the at least one link, a bitmap subfield signalling the at least one link for PM enabling or disabling from amongst a plurality of enabled links with the AP MLD, and optionally, a parameter subfield signalling one or more PM mechanisms that are enabled or disabled on the at least one link and / or signalling a configuration switch delay defining a duration required by the non-AP MLD to configure an affiliated non- AP station when switching between a low-power configuration and a high-power configuration.

15. The method of Claim 1 , further comprising signalling, to the AP MLD, a Multiple PerLink PM support of the non-AP MLD.

16. The method of Claim 15, wherein the Multiple Per-Link PM support is signalled using one signalling field from amongst: one bit of an Enhanced Multi-Link (EML) Capabilities subfield in a Common Info field of a Basic Multi-Link element, in particular any of bits B8-B10 and B15, one bit of an Extended MLD Capabilities And Operations subfield in a Common Info field of a Basic Multi-Link element, in particular any of bits B6 and B7-B15.

17. The method of Claim 15, wherein the signalling of the Multiple Per-Link PM support is made together with a signalling of one or more PM mechanisms supported by the non-AP MLD.

18. The method of Claim 17, wherein one or more supported PM mechanisms are signalled per each enabled link with the AP MLD.

19. The method of Claim 17, wherein one or more supported PM mechanisms is signalled once for all enabled links with the AP MLD.

20. The method of Claim 1 , wherein the notification frame enables or disables power management (PM) of the other non-AP STA of the non-AP MLD.

21. A communication method in a wireless network, comprising, at a non-access point (non-AP) station (STA) affiliated with a non-AP multi-link device (MLD), activating or deactivating power management (PM) mechanism for one or more other affiliated non-AP STAs of the same non-AP MLD.

22. A protected Action frame to be sent by a non-access point (non-AP) station (STA) affiliated with a non-AP multi-link device (MLD), the protected Action frame including: a first field taking a first value to signal enabling of power management (PM) on one or more enabled links between the non-AP MLD and an AP MLD, and a second value to signal disabling of PM, a bitmap field to indicate the one or more links, and optionally a parameter field to indicate one or more Per-Link PM mechanisms to be applied on the one or more links, and / or a configuration switch delay field indicating a duration required by the non-AP MLD to configure an affiliated non-AP station when switching between a low-power configuration and a high-power configuration.

23. A wireless communication device comprising at least one microprocessor configured for carrying out the method of Claim 1 .

24. 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 .

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