Method and apparatus for power management support in a wireless network

Abstract

An Access Point (AP) multi-link device (MLD) operating a power management (PM) mechanism according to two different operating modes, advertising an operating mode among the two different operating mod

Description

FIELD OF THE INVENTION The present invention generally relates to wireless communications and more specifically to Power Management (PM) mechanism support. BACKGROUND OF INVENTION Nowadays mainstream APs have been specified to be always in active mode using the highest bandwidths (BW) and number of spatial streams (NSS) so that the associated STAs can get the highest throughput and fastest service possible. This paradigm has been emphasized with 802.11be with the introduction of Multi-Link (ML) Operation (MLO) for which the devices operate with several radios to communicate over multiple concurrent and non-contiguous communication links. However, the power consumed by APs is now significant (tens of watts) whereas the power consumption is now a key performance indicator for consumer (environmentally conscious consumers, variable energy-price sensitive consumers). In such context, the new 802.11.bn amendment sets the objective to provide new Power Management (PM) mechanisms not only for non-AP stations (STAs) but also for AP which is quite a new paradigm. At the current stage, only one PM mechanism for AP has been specified in the standard IEEE Std 802.11-2020 and it is only specific to devices operating on sub-1 GHz license exempt ISM bands (S1G) which is not the scope of 802.11.bn amendment. If no new PM mechanism for AP has been yet specified in 802.11 be, the task group moves towards the specification of a PM mechanism directly for an AP MLD with as main concept that its affiliated APs operate in a power save mode in which power saving features are implemented to reduce energy consumption. In this context, the invention proposes means to support and implement advanced PM mechanisms operating at MLD level allowing to be used in parallel and in complement of the enablement / disablement link mechanism (TID-to-Link Mapping mechanism) specified in 802.11 be used to select which link (affiliated AP) the data shall be used. Notably, it allows to extends the notion of enabled link (at least one TID is mapped to that link either in DL or in UL) for which the radio is on and disabled link (no TIDs are mapped to that link both in DL and UL) for with the radio is off and specify new PM operations others than the standardized operations of Affiliated AP link disablement and enablement in order to manage more efficiently the PM of an affiliated AP when this one operates in AP PS mode. SUMMARY OF THE INVENTION The present invention has been devised to address one or more of the foregoing concerns. According to a first aspect of the invention there is provided a method of communication in a wireless network, the method comprising: - by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, advertising an operating mode among the at least two different operating modes; and - by the AP MLD, operating according to the advertised operating mode. In some embodiments, the advertising step comprises transmitting a frame comprising an indication of the operating mode. In some embodiments, the indication indicates a time for the AP MLD to operate according to the advertised operating mode. In some embodiments, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the time for the AP MLD to operate according to the advertised operating mode is the next Target Beacon Transmission Time, TBTT of the active PM AP. In some embodiments, the frame is a beacon frame. In some embodiments, the indication is comprised in a Power Management field of a Frame Control field in the MAC Header of the beacon frame. In some embodiments, the indication is comprised in an AP MLD PM mode field in a MLD Capabilities And Operations field in a Common Info field of a Multi-Link element of the Beacon frame. In some embodiments, the indication is comprised in a AP MLD PM mode field in an Extended MLD Capabilities And Operations field in a Common Info field of a MultiLink element of the Beacon frame. In some embodiments, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the frame is only transmitted by the active PM AP. In some embodiments, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the two different operating modes are an AP MLD active mode where all affiliated APs of the AP MLD operate in AP active mode, and an AP MLD Power Save mode, AP MLD PS mode, where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLD operates in AP PS mode. In some embodiments, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the link associated with the active PM AP is and remains enabled in DL and UL. In some embodiments, the AP MLD refuses a negotiated TID-to-Link Mapping proposed by non-AP MLD if the proposed negotiated TID-to-Link Mapping for which the link associated with the active PM AP is enabled in DL and UL. In some embodiments, an AP MLD shall not advertise a TID to link mapping for which the link associated with the active PM AP is disabled According to another aspect of the invention there is provided a method of communication in a wireless network, the method comprising: - by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, receiving an association request from a non-AP MLD; and - by the AP MLD, refusing the association when the non-AP MLD does not advertise the support of AP PM mechanism. In some embodiments, the non-AP MLD advertises the support of AP PM mechanism by transmitting a Probe Request comprising an AP PM support field with a value indicating the support of AP PM mechanism. In some embodiments: - refusing the association request by the AP MLD comprises transmitting an association response comprising an indication indicating that the association is refused because the non-AP MLD does not support AP PM mechanism. In some embodiments, the indication is a specific status code. According to another aspect of the invention there is provided a method of communication in a wireless network, the method comprising: - by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, the AP MLD having one of its affiliated AP stations operating as an active PM AP, receiving an association request from a non-AP MLD; and - by the AP MLD, refusing the association when the non-AP MLD does not request a link corresponding to the active PM AP. In some embodiments: - refusing the association request by the AP MLD comprises transmitting an association response comprising an indication indicating that the association is refused because the non-AP MLD does not request the link corresponding to the active PM AP. In some embodiments, the association response further comprises the link identifier of the link operated by the Active PM AP. According to another aspect of the invention there is provided a method of communication in a wireless network, the method comprising: - by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, receiving an association request from a non-AP MLD; and - transmitting a ML Probe Response comprising an indication indicating which of its affiliated APs operate as an active PM AP. In some embodiments, the indication is an Active PM AP field in an UHR capabilities field of the ML Probe Response. In some embodiments, the Active PM AP field is further comprised in each per-STA profile sub element of a Basic ML element of the ML Probe Response. According to another aspect of the invention there is provided a method of communication in a wireless network, the method comprising: - by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, the AP MLD with one of its affiliated AP stations operating as an active PM AP, receiving an association request from a non-AP MLD that does not advertise the support of AP PM mechanism; and - accepting the association of the non-AP MLD when the non-AP MLD only request the link associated with the active PM AP. According to another aspect of the invention there is provided a method of communication in a wireless network, the method comprising: - by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, the two different operating modes being an AP MLD active mode where all affiliated AP station of the AP MLD operate in AP active mode, and an AP MLD Power Save mode where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLD operates in AP PS mode, receiving an association request from a non-AP MLD that does not advertise the support of AP PM mechanism; - accepting the association of the non-AP MLD; and - by the AP MLD, operating in active PM mode as long as the non-AP MLD is associated. According to another aspect of the invention there is provided a method of communication in a wireless network, the method comprising: - by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the two different operating modes being an AP MLD active mode where all affiliated AP station of the AP MLD operate in AP active mode, and an AP Power Save, PS, mode where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLD operates in AP PS mode, receiving an association request from a non-AP MLD that does not include the link associated with the active PM AP; - accepting the association of the non-AP MLD that does not include the link associated with the active PM AP; and - by the AP MLD, operating in active PM mode as long as the non-AP MLD is associated. According to another aspect of the invention there is provided a method according to the invention, wherein the affiliated AP operating as an active PM AP has a link established with an affiliated station of each non-AP MLD. According to another aspect of the invention there is provided a computer-readable storage medium storing instructions of a computer program for implementing a method according to the invention. According to another aspect of the invention there is provided a computer program product for a programmable apparatus, the computer program product comprising a sequence of instructions for implementing a method according to the invention when loaded into and executed by the programmable apparatus. According to another aspect of the invention there is provided a computer program which upon execution causes the method of the invention to be performed. According to another aspect of the invention there is provided an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, communicating in a wireless network, the AP MLD comprising a processor configured for: - advertising an operating mode among the at least two different operating modes; and - operating according to the advertised operating mode. According to another aspect of the invention there is provided an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, communicating in a wireless network, the AP MLD comprising a processor configured for: - receiving an association request from a non-AP MLD; and - refusing the association when the non-AP MLD does not advertise the support of AP PM mechanism. According to another aspect of the invention there is provided an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, the AP MLD having one of its affiliated AP stations operating as an active PM AP, communicating in a wireless network, the AP MLD comprising a processor configured for: - receiving an association request from a non-AP MLD; and - refusing the association when the non-AP MLD does not request the link corresponding to the active PM AP. According to another aspect of the invention there is provided an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the AP MLD comprising a processor configured for: - receiving an association request from a non-AP MLD that does not advertise the support of AP PM mechanism; and - accepting the association of the non-AP MLD when the non-AP MLD only request the link associated with the active PM AP. According to another aspect of the invention there is provided an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, the two different operating modes being an AP MLD active mode where all affiliated AP station of the AP MLD operate in AP active mode, and an AP MLD Power Save, PS, mode where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLD operates in AP PS mode, communicating in a wireless network, the AP MLD comprising a processor configured for: - receiving an association request from a non-AP MLD that does not advertise the support of AP PM mechanism; - accepting the association of the non-AP MLD; and - operating in active PM mode as long as the non-AP MLD is associated. According to another aspect of the invention there is provided an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the two different operating modes being an AP MLD active mode where all affiliated AP station of the AP MLD operate in AP active mode, and an AP MLD Power Save, PS, mode where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLD operates in AP PS mode, communicating in a wireless network, the AP MLD comprising a processor configured for: - receiving an association request from a non-AP MLD that does not; - accepting the association of the non-AP MLD that does not require the link associated with the active PM AP; and - operating in active PM mode as long as the non-AP MLD is associated. 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. 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. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of example only, and with reference to the following drawings in which: Figure 1 illustrates a typical 802.11be / bn network environment involving an AP MLD operating an AP PM mechanism in accordance with embodiments of the present invention; Figure 2 illustrates a first frame format used by an AP MLD operating with an AP PM mechanism for announcing its AP MLD PM Mode in accordance with embodiments of the present invention; Figure 3 illustrates a second frame format used by an AP MLD operating with an AP PM mechanism for announcing its AP MLD PM Mode in accordance with embodiments of the present invention; Figure 4 illustrates a third frame format used by an AP MLD operating with an AP PM mechanism for announcing its AP MLD PM Mode in accordance with embodiments of the present invention; Figure 5 schematically illustrates an exemplary timeline of an AP MLD operating with a PM mechanism in accordance with embodiments of the present invention; Figure 6 schematically illustrates an exemplary 802.11be / bn multi-link reference model for an AP MLD operating with an AP PM mechanism in accordance with embodiments of the present invention; Figure 7 illustrates a schematic representation of a wireless communication device in accordance with embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION 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 SingleCarrier 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 subcarriers 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 not (so-called non-AP STA or STA). 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. 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. 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. 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. The 802.11 family of standards define various media access control (MAC) mechanisms to drive access to the wireless medium. The current discussions in the task group 802.11 be introduce 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. 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 MultiLink 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. An illustrative architecture of a Multi-Link Device is described below with reference to Figures 6. 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 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). A communication link or “link” thus corresponds to a given channel (e.g. 20 MHz, 40 MHz, and so on) 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 affiliated APs and non-AP STAs operate on their respective channels in accordance with one or more of the IEEE 802.11 standards (a / b / g / n / ac / ad / af / ah / aj / ay / ax / be / bn) or other wireless communication standards. 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. From architecture point of view, a 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). Figure 1 illustrates a typical 802.11 network environment involving an AP MLD operating an AP PM mechanism in accordance with embodiments of the present invention. Wireless communication network 100 involves an AP MLD 110 and three non-AP MLDs 120, 130 and 140. Of course, another number of non-AP MLDs registering to the AP MLD 110 and then exchanging frames with it may be contemplated. AP MLD 110 has multiple affiliated APs, three affiliated APs 111, 112 and 113 (also referenced AP1, AP2, AP3 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. The non-AP MLDs 120, 130 and 140 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, 112 and 113) 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, two non-AP STAs 131 and 132 (also referenced B1 and B2 respectively) are affiliated with non-AP MLD 130 and three non-AP STAs 141, 142 and 143 (also referenced C1, C2 and C3 respectively) are affiliated with non-AP MLD 140. For illustrative purpose, AP 111 is set to operate on channel 10 corresponding to an operating 20 MHz channel in the 2.4 GHz frequency band, AP 112 is set to operate on channel 36-40 corresponding to an operating 40 MHz channel in the 5 GHz frequency band and AP 113 is set to operate on channel 149-153 corresponding to an operating 40 MHz channel in the 5GHz frequency band too. Each affiliated AP offers a link towards the AP MLD 110 to the affiliated non-AP STAs of a non-AP MLD. Hence, the links for each non-AP MLD (referred to as link corresponding to the affiliated AP) can be merely identified with the identifiers of the respective affiliated APs. In this context, each of the affiliated APs 111, 112 and 113 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). Of course, other wording, such as “AP ID”, could be used in a variant. To perform multi-link communications, each non-AP MLD 120, 130 and 140 operates a ML discovery and ML setup to discover, authenticate, associate and set up multiple links with the AP MLD 110, each link, referred to setup link, being established between an affiliated AP of the AP MLD 110 and an affiliated non-AP STA of the non-AP MLD. According to the present disclosure, the AP MLD 110 operates a PM mechanism, referred to as AP PM mechanism. The present disclosure does not relate to the AP PM mechanism itself, which is considered out of the scope of the document. The present disclosure relates to support of the AP PM mechanism. In particular, it is described means for an AP MLD to signal to associated non-AP MLD the PM operating mode of the AP PM mechanism. It is also described means for a non-AP MLD to signal the support of AP PM mechanism, means to signal AP PM mechanism related causes for an AP MLD to refuse the association of a non-AP MLD and means for advertising an active PM AP. According to some embodiments, the AP PM mechanism is activated by default and remains always activated. According to other embodiments, specific action frames as specified in IEEE Std 802.11-2020 are defined to advertise an operating mode the AP PM mechanism at any time. An Action frame identified by a ‘Category’ field assigned to a specific value k in the range [31,125] as specified in Table 9-51 of the IEEE Std 802.11-2020, so far reserved. For the purpose of illustration, a reserved value, e.g. 31, is used to define a new category value corresponding to “AP PM Action frames”, meaning action frames relative to AP PM mechanism. Of course, any other value in the above range can be used. An “AP PM Action frame” is sent by the AP MLD through an affiliated AP and received by non-AP MLDs through an affiliated non-AP. The frame formats are identified by the one-byte ‘AP PM Action’ field which follows immediately the Category field in the action frame. The values of the AP PM Action field may be defined to distinguish between an active operating mode of the AP PM mechanism and a deactivated operating mode of the AP PM mechanism. As an example, the following table can be used: Action Field value Meaning 1 AP PM active 2 AP PM deactivated An AP PM Action field value set to 1 thus signals the active operation mode of the AP PM mechanism and an AP PM Action field value set to 2 activation signals the deactivated operating mode of the AP PM mechanism. In the following description, the AP PM mechanism of AP MLD is considered activated. According to some embodiments, an AP MLD may refuse the association of a non-AP MLD if this one doesn’t support the AP PM mechanism operating by the AP MLD. For this, according to some embodiments, the non-AP MLD advertises its support to the AP PM mechanism in the ML probe request in a specific 1 -bit field referred to as “AP PM support” which is included in the 802.11bn (UHR) capabilities. For example, theAP PM support field is set to 1 if the non-AP MLD supports the AP PM mechanism and 0 otherwise. If the ML probe request doesn’t include an AP PM support field, the AP MLD considers that the non-AP MLD doesn’t support the AP PM mechanism. When an AP MLD refuses the association of a non-AP MLD, a specific status code may be specified for indicating that the reason of the failure is due to the fact that non-AP MLD doesn’t support the AP PM mechanism operated by the AP MLD. For this, a new reserved value of the table 9-78 of the standard IEEE Std 802.11-2020 between 130 and 65535 may be used with a specific name, for example PM-AP_MLD_NOT_SUPPORTED. This status code is included in the status code field of the associated response transmitted by the AP MLD. According to some embodiments, an AP MLD may accept the association of a non-AP MLD even if this one doesn’t support the AP PM mechanism operated by the AP MLD. In this case, the association implies some constraints described in the later description. When an AP MLD operates an AP PM mechanism, according to some embodiments of the invention, it operates with two (AP MLD) PM modes referred to as “AP MLD Active” mode and “AP MLD PS” mode. Similarly, its affiliated APs operate also with two (AP) PM modes referred to as “AP Active” mode wherein the affiliated AP radio is always on and “AP PS” mode for which the power saving features are implemented to reduce energy consumption. The power saving features are out of scope of the disclosure. When the AP MLD operates in AP MLD Active mode, all these affiliated APs operate in AP Active mode. When the AP MLD operates in AP MLD PS mode, one of its affiliated APs operates in AP Active mode and at least one of its other affiliated AP(s) operates in AP PS mode. This affiliated AP operating in AP Active mode is referred to as Active PM AP. The link associated with the Active PM AP may be referred as the Active PM link According to some embodiments, the Active PM AP is connected with each associated non-AP MLD. The link associated with the Active PM AP may be referred as the Active PM link. In other words, during the ML setup procedure of a non-AP MLD with the AP MLD, a setup link is established between the Active PM AP and one affiliated non-AP STA of each non-AP MLD. In case of the non-AP MLD has not requested the link corresponding to the Active PM AP, the Active PM link, in its association request, according to some embodiments, the AP MLD may refuse the association of the non-AP MLD. According to some embodiments, a specific status code is specified indicating that the reason of the failure is due to the fact that non-AP MLD has not requested the Active PM link. For this, a new reserved value of the table 9-78 of the standard IEEE Std 802.11-2020 between 130 and 65535 may be used with a specific name, for example ACTIVE_PM_AP_NOT_SELECTED. This status code is included in the status code field of the association response transmitted by the AP MLD. In such a case, the payload of the association response may contain the link ID of the link operated by the Active PM AP. According to other embodiments wherein the non-AP MLD has not requested the Active PM link in its association request, the AP MLD may accept the association of the non-AP MLD with some constraints detailed below. According to some embodiments, during the ML discovery, the AP MLD may advertise the Active PM AP in the ML probe response. According to some embodiments, an Active PM AP 1-bit field is introduced and carried in the 802.11bn (UHR) capabilities of the ML probe response transmitted by an affiliated AP of the AP MLD referred to as reporting affiliated AP. A corresponding Active PM AP field is also introduced in each per-STA profile sub element of the Basic Multi-Link element of the ML probe response, each per-STA profile corresponding to an affiliated AP of the AP MLD referred to as reported affiliated AP. The Active PM AP 1-bit field carried in the 802.11bn (UHR) capabilities is set to 1 if the reporting affiliated AP is the Active PM AP and 0 otherwise. The Active PM AP 1-bit field of a per-STA profile sub element is set to 1 if the corresponding reported affiliated AP is the Active PM AP and 0 otherwise. According to other embodiments, an Active PM AP 4-bits field may be introduced in the 802.11 bn (UHR) capabilities of the ML probe response corresponding to the Link ID of the Active PM AP. In the example of Figure 1, the affiliated AP 111 is designated as the Active PM AP. During the association procedure of the non-AP MLD 120 with the AP MLD 110, a first setup link has been established between the affiliated AP 111 as Active PM AP and the affiliated non-AP STA 121 and a second setup link has been established between the affiliated AP 112 and the affiliated non-AP STA 122. During the association procedure of the non-AP MLD 130 with the AP MLD 110, a first setup link has been established between the affiliated AP 111 as Active PM AP and the affiliated non-AP STA 131 and a second setup link has been established between the affiliated AP 113 and the affiliated non-AP STA 132. During the association procedure of the non-AP MLD 140 with the AP MLD 110, a first setup link has been established between the affiliated AP 111 as Active PM AP and the affiliated non-AP STA 141, a second setup link has been established between the affiliated AP 112 and the affiliated non-AP STA 142 and a third setup link has been established between the affiliated AP 113 and the affiliated non-AP STA 143. Once setup, a link is either enabled or disabled according to the TID-to-link mapping mechanism. This mechanism allows an AP MLD and a non-AP MLD that performed or are performing multi-link setup to determine how Data frames belonging to TIDs 0-7 and management frames will be assigned for transmission, on the setup links between the two MLDs in downlink (DL) and uplink (UL). A setup link is defined as enabled for a non-AP MLD if at least one TID is mapped to that link either in DL or in UL and is defined as disabled if no TIDs are mapped to that link both in DL and UL. At any point in time, a TID shall always be mapped to at least one setup link both in DL and UL, which means that a TID-to-link mapping change is only valid and successful if it will not result in having any TID for which the link set for DL or UL is made of zero setup links. According to the disclosure, the AP PM mechanism operates only on the enabled links of the AP MLD. _Two operations have been specified in order to change over the time the current assigned TID-to-link mapping of the setup links to a new one: TID-to-link mapping negotiation and TID-to-link mapping advertisement. The TID-to-link mapping negotiation is initiated by a non-AP MLD or an AP MLD. For this, during the multi-link setup procedure, a non-AP MLD includes the TID-to-link Mapping element in its (Re)Association Request frame specifying the new TID-to-link mapping. Similarly, after a successful multi-link (re)setup and complete 4-way handshake is (if RSNA is required), the non-AP MLD sends a dedicated individually addressed protected EHT Action frames called TID-to-link Mapping Request frame including a TID-to-link Mapping element specifying the new TID-to-link mapping to the AP MLD to negotiate a new TID-to-link mapping. In the same way, an AP MLD sends an individually addressed TID-to-link Mapping Request frame specifying the new TID-to-link mapping to a non-AP MLD. Upon receiving the individually addressed TID-to-link Mapping Request frame, the responding MLD shall send an individually addressed TID-to-link Mapping Response frame to the initiating MLD according to the following rules: if the responding MLD accepts the requested TID-to-link mapping in the TID-to-link Mapping element in the received TID-to-link Mapping Request frame, it shall set to 0 (SUCCESS) the Status Code in the TID-to-link Mapping Response frame. Otherwise, the responding MLD shall indicate rejection of the proposed TID-to-link mapping by setting to either 133 (DENIED_TID_TO_LINK_MAPPING) or 134 (PREFERRED_TID_TO_LINK_MAPPING_SUGGESTED) the Status Code in the TID-to-link Mapping Response frame. When the Status Code in the TID-to-link Mapping Response frame is 134 (PREFERRED_TID_TO_LINK_MAPPING_SUGGESTED), the responding MLD is suggesting a preferred mapping as indicated in the TID-to-link Mapping element included in the frame. The TID-to-link mapping advertisement is initiated by the AP MLD which advertises a mandatory TID-to-link mapping by including a TID-To-Link Mapping element specifying the new TID-to-link mapping in the Beacon and Probe Response frames that the APs affiliated with the AP MLD transmit. The link corresponding to the affiliated AP 111 designated as the Active PM AP shall be and remain always enabled in DL and UL when an AP MLD operates an AP PM mechanism. In other words, the link corresponding to the affiliated AP 111 shall not be disabled neither by the TID-to-link mapping negotiation operation nor TID-to-link mapping advertisement. It means also that an AP MLD shall deactivate its AP PM mechanism if it has the intention to disable the Active PM AP by transmitting a specific action frame as described previously. For this, the new TID-to-link mapping negotiated by the TID-to-link mapping negotiation shall ensure that the Active PM link is enabled in DL and UL. If it is not the case, meaning that the TID-to-link Mapping Request frame includes a new TID-to-link mapping for which the link corresponding to the Active PM AP is disabled, the responding MLD shall indicate rejection of the proposed TID-to-link mapping by setting to 133 (DENIED_TID_TO_LINK_MAPPING). In alternative embodiments, the responding MLD shall indicate rejection of the proposed TID-to-link mapping by setting a new status code, for instance to 135 value that may be referred to as DENIED_TID_TO_LINK_MAPPING_FOR_PM. Similarly, an AP MLD shall not advertise a new TID-to-link mapping for which the link corresponding to the Active PM AP 111 is disabled. When an AP MLD has associated a non-AP MLD which doesn’t support the AP PM mechanism, according to some embodiment, the AP MLD shall accept only as requested link the Active PM link. According to other embodiments, the AP MLD may accept any requested link and in such a case, the AP MLD operates always in AP MLD Active mode and shall not operate in AP MLD PS mode. In other words, the AP MLD must operate in AP MLD Active mode as long as the non-AP MLD which doesn’t support the AP PM mechanism is associated. According to some embodiments wherein a non-AP MLD is associated with the AP MLD but doesn’t operate with the Active PM AP, the AP MLD may accept the association of the non-AP MLD but in such a case, it operates always in AP MLD Active mode and shall not operate in AP MLD PS mode. In other words, the AP MLD must operate in AP MLD Active mode as long as the non-AP MLD which doesn’t operate with the Active PM AP is associated. The AP MLD PM mode of the AP MLD is only advertised by the Active PM AP. As the Active PM AP is connected with each associated non-AP MLD, the advertisement is potentially received by all non-AP MLD. The Active PM AP advertises the AP MLD PM mode of the AP MLD in each beacon that it transmits. For the advertisement in a beacon frame, the disclosure provides a first frame format as illustrated in Figure 2, a second frame format as illustrated in Figure 3 and a third frame format as illustrated in Figure 4. During the multi-link setup, the AP MLD shall advertise its current MLD PM mode in the (Re) Association Response. By default, an AP MLD is in AP MLD Active mode. According to some embodiments, the advertisement of the AP MLD PM mode is effective at the PM date. According to one embodiment, the PM date corresponds to the start of the next Target Beacon Transmission Time, TBTT, of the Active PM AP. From it, the AP MLD advertises its affiliated AP to update their AP PM Mode at the start of the next TBTT. The implementation details are described in relation to Figure 6. The non-AP MLD shall retrieve the advertised AP MLD PM mode of the AP MLD transmitted by the Active PM AP to be applied at the PM date. This means that when the advertised AP MLD PM mode corresponds to the current AP MLD PM mode, this indicates that the AP MLD PM mode does not change. When the advertised AP MLD PM mode is different from the current AP MLD PM mode, a change or switch of the AP MLD PM mode will occur at the PM date corresponding to the next TBTT in the exemplary embodiment. After retrieving the advertised AP MLD PM mode, the non-AP MLD shall update the PM information relative to the AP MLD in order to take into account the updated AP MLD PM mode of the AP MLD at the start of the next TBTT of the Active PM AP. For this, the non-AP MLD advertises its affiliated STA to update the PM Mode information of the affiliated AP with which it is associated. Once an MLD has successfully negotiated a new TID-to-link mapping or the AP MLD has advertised a new TID-to-link mapping, the AP MLD PM mode of an affiliated AP (other than the Active PM AP) switching from disabled to enabled is “AP Active” if the AP MLD is in “AP MLD Active” or “AP PS” mode if the AP MLD is in “AP MLD PS”. According to some embodiments, when an affiliated AP operates in “AP PS” mode, it no longer transmits beacon frames. In such a case, the Timing Synchronization Function (TSF) of the non-AP MLD is ensured through the Active PS AP. More precisely, the non-AP MLD determines the Timing Synchronization Function (TSF) information of all the APs affiliated with an AP MLD when it receives a frame carrying TSF of the Active PM AP and use that information to maintain TSF timer for each non-AP STA. Figure 2 illustrates a first frame format that may be used by an AP MLD operating with an AP PM mechanism for announcing its AP MLD PM Mode in accordance with embodiments of the present invention. This first frame format proposes a different use of the existing Power Management field 230 specified in the standard IEEE Std 802.11-2020 and which is present in all exchanged 802.11 frames 200 and more precisely in their Frame Control field 220 of their MAC header 210 specified in the section 9.2.4.1. According to the standard, it is used to indicate the power management mode of a STA and is reserved in all frames transmitted by the AP. According to some embodiments of the invention, the Power Management field 230 is now used to indicate the PM mode of the AP MLD (no longer reserved). It may be, for example, set to 1 to indicate that the AP MLD will operate in AP MLD PS mode at the PM date and it may be set to 0 to indicate that the AP MLD will operate in AP MLD active mode at the PM date. Depending on the current AP MLD PM mode, this field is an indication of a switch of AP MLD PM mode or an indication that the current AP MLD PM mode is maintained after the next TBTT. Figure 3 illustrates a second frame format that may be used by an AP MLD operating with an AP PM mechanism for announcing its AP MLD PM Mode in accordance with embodiments of the present invention. This second frame format relies on a new 1 -bit field 340 referred to as AP MLD Mode field which is included in a management frame 300, typically a beacon frame, transmitted by an affiliated AP of an AP MLD and more precisely in their MLD Capabilities And Operations field 330 of their Common Info field 320 of their Multi-Link element 310, replacing a reserved bit as it is specified in section 9.4.2.312 of IEEE P802.11be / D4. According to some embodiments of the invention, the 1-bit AP MLD Mode subfield 340 is used to indicate the PM mode of the AP MLD. It may be, for example, set to 1 to indicate that the AP MLD will operate in AP MLD PS mode at the PM date. It may be set to 0 to indicate that the AP MLD will operate in AP MLD active mode at the PM date. Depending on the current AP MLD PM mode, this field is an indication of a switch of AP MLD PM mode or an indication that the current AP MLD PM mode is maintained after the next TBTT. Figure 4 illustrates a third frame format that may be used by an AP MLD operating with an AP PM mechanism for announcing its AP MLD PM Mode in accordance with embodiments of the present invention. This third frame format relies on a new 1-bit field 440 referred to as AP MLD Mode field which is included in a management frame 400, typically beacon frame, transmitted by an affiliated AP of an AP MLD and more precisely in their Extended MLD Capabilities and Operations field 430 of their Common Info field 420 of their Multi-Link element 410, replacing a reserved bit as it is specified in section 9.4.2.312 of IEEE P802.11be / D4. It is to be noted that this embodiment differs from the previous one by the use of the Extended MLD Capabilities and Operations field 430 instead of the MLD Capabilities And Operations field 330. According some embodiments of the invention, the 1 -bit AP MLD Mode subfield 440 is used to indicate the PM mode of the AP MLD. It may be, for example, set to 1 to indicate that the AP MLD will operate in AP MLD PS mode at the start of the next TBTT of the Active PM AP. It may be set to 0 to indicate that the AP MLD will operate in AP MLD active mode at the start of the next TBTT of the Active PM AP. Depending on the current AP MLD PM mode, this field is an indication of a switch of AP MLD PM mode or an indication that the current AP MLD PM mode is maintained at the PM date. Figure 5 schematically illustrates an exemplary timeline of an AP MLD operating with an AP PM mechanism as illustrated in Figure 1 in accordance with embodiments of the present invention. In a first phase 501, the AP MLD 110 operates in AP MLD Active Mode. It means that all its affiliated APs, AP1 120, AP2 130 and AP3 140 operate in AP Active mode, schematically referred by respective phases 511, 521 and 531. During this phase 501, AP1 transmits beacon frames 515 and 516, AP2 beacon frames 525 and 526, AP3 beacon frames 535 and 536. According to these embodiments, only the Active PM AP AP1 120 advertises the AP MLD PM mode of the AP MLD, namely AP MLD Active Mode during phase 501. This advertisement is done in the beacon frame 515. It indicates that the AP MLD operates in the AP MLD Active Mode and may rely, for example on any of the frame formats as illustrated in Figure 2 or Figure 3 or Figure 4. During this first phase 501, the AP MLD may decide to switch from its AP MLD from AP MLD Active Mode to AP MLD PS Mode. Phase 502 represents the time interval when the AP MLD is in AP MLD PS mode. The switch is advertised by the AP MLD in the beacon frames 516 by using, for example, either of the frame formats illustrated in Figure 2 or Figure 3 or Figure 4. By advertising in beacon frame 516 an AP MLD PS mode while the current AP MLD PM mode is AP MLD active mode, the AP MLD notifies the switch to the receiving non-AP MLD. The change of the AP MLD mode is effective at the start of the next TBTT of the Active PM AP AP1 120. Once the AP MLD operates in AP MLD PS Mode in phase 502, its affiliated Active PM AP AP1 120 remains in AP Active mode in phase 512 and its other affiliated APs AP2 130 and AP3 140 operate now in AP PS mode in respectively referenced phases 522 and 532. The next beacon frames 517 and 518 transmitted by the Active PM AP AP1 120 indicates that the AP MLD remains in the AP MLD PS Mode. According to some embodiments, if the Active PM AP AP1 120 continues to transmit beacon frames when the AP MLD operates in AP MLD PS Mode, phase 502, the affiliated APs AP2 130 and AP3140 operating now in AP PS mode transmit no longer beacon frames during phases 522, 532. Figure 6 schematically illustrate the reference model of an AP MLD operating with an AP PM mechanism in accordance with embodiments of the present invention. The 802.11 be multi-link reference model illustrates the fact that an AP MLD may transmit using several links, particularly at the level of the MAC layer 620 and the PHY layer 630. The MAC layer 620 comprises one MLD Upper MAC Sublayer (UMAC) 610 and multiple MLD lower MAC sublayer (LMAC) 620-x, 620-y, 620-z coupled with a respective PHY layer 630-x, 630-y, 630-z, each couple corresponding to a link 640-x, 640-y, 640-z and an affiliated AP of the AP MLD. The UMAC 610 performs functionalities that are common across all links and each LMAC 620-x, 620-y, 620-z performs functionalities that are local to each link 640-x, 640-y, 640-z. The UMAC layer then offers UMAC interfaces with the link-specific blocks 620-x, 620-y, 620-z, respectively 612, 613 and 614. According to some embodiments of the invention, the UMAC 610 contains an MLD AP PM module 611 which manages the AP MLD PM Modes of the AP MLD and each LMAC 620-x, 620-y, 620-z contain respectively AP PM module 621-x, 621-y, 621-z which manages the AP PM Modes of its affiliated AP. When the MLD AP PM module 611 changes the AP MLD PM Mode of the AP MLD, it shall advertise to each of these affiliated AP the new AP mode to be applied at the start of the next TBTT of the Active PM AP. For this, it transmits an AP PM mode update to each AP PM module 621-x, 621-y, 621-z through the respective interfaces 612, 613 and 614 indicating the new AP PM Mode that the affiliated AP shall apply with the application date corresponding to the start of the next TBTT of the Active PM AP. According to some embodiments, the advertisement of the AP MLD PM mode is effective at the start of the next TBTT of the Active PM AP. For this, the AP MLD requests its affiliated AP to update their AP PM Mode at the start of the next TBTT. Figure 7 shows a schematic representation of a wireless communication device in accordance with embodiments of the present invention. The communication device 700 may preferably be a device such as a microcomputer, a workstation or a light portable device. The communication device 700 comprises a communication bus 713 to which there are preferably connected: a central processing unit 701, such as a processor, denoted CPU; a memory 703 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 702 and 702’ 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 704 and 704’, respectively. Preferably the communication bus 713 provides communication and interoperability between the various elements included in the communication device 700 or connected to it. The representation of the bus is not limiting and in particularthe central processing unit is operable to communicate instructions to any element of the communication device 700 directly or by means of another element of the communication device 700. 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 702 or 702’, in order to be stored in the memory of the communication device 700 before being executed. 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. Many further modifications and variations will suggest themselves to those versed in the art upon referring to the foregoing illustrative embodiments, which are given 5 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. 10

Claims

1. A method of communication in a wireless network, the method comprising:- by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, advertising an operating mode among the at least two different operating modes; and- by the AP MLD, operating according to the advertised operating mode.

2. The method of claim 1, wherein the advertising step comprises transmitting a frame comprising an indication of the operating mode.

3. The method of claim 2, wherein the indication indicates a time for the AP MLD to operate according to the advertised operating mode.

4. The method of claim 3, wherein, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the time for the AP MLD to operate according to the advertised operating mode is the next Target Beacon Transmission Time, TBTT of the active PM AP.

5. The method of claim 2, wherein the frame is a beacon frame.

6. The method of claim 5, wherein the indication is comprised in a Power Management field of a Frame Control field in the MAC Header of the beacon frame.

7. The method of claim 5, wherein the indication is comprised in an AP MLD PM mode field in a MLD Capabilities And Operations field in a Common Info field of a Multi-Link element of the Beacon frame.

8. The method of claim 5, wherein the indication is comprised in a AP MLD PM mode field in an Extended MLD Capabilities And Operations field in a Common Info field of a Multi-Link element of the Beacon frame.

9. The method of claim 2, wherein, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the frame is only transmitted by the active PM AP.

10. The method of any one claim 1 to 9, wherein, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the two different operating modes are an AP MLD active mode where all affiliated APs of the AP MLD operate in AP active mode, and an AP MLD Power Save mode, AP MLD PS mode, where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLD operates in AP PS mode.

11. The method of claim 1, wherein, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the link associated with the active PM AP is and remains enabled in DL and UL.

12. The method of claim 11, wherein the AP MLD refuses a negotiated TID-to-Link Mapping proposed by non-AP MLD if the proposed negotiated TID-to-Link Mapping for which the link associated with the active PM AP is enabled in DL and UL.

13. The method of claim 11, wherein an AP MLD shall not advertise a TID to link mapping for which the link associated with the active PM AP is disabled14. A method of communication in a wireless network, the method comprising:- by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, receiving an association request from a non-AP MLD; and- by the AP MLD, refusing the association when the non-AP MLD does not advertise the support of AP PM mechanism.

15. The method of claim 14, wherein the non-AP MLD advertises the support of AP PM mechanism by transmitting a Probe Request comprising an AP PM support field with a value indicating the support of AP PM mechanism.

16. The method of claim 14, wherein:- refusing the association request by the AP MLD comprises transmitting an association response comprising an indication indicating that the association is refused because the non-AP MLD does not support AP PM mechanism.

17. The method of claim 16, wherein the indication is a specific status code.

18. A method of communication in a wireless network, the method comprising:- by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, the AP MLD having one of its affiliated AP stations operating as an active PM AP, receiving an association request from a non-AP MLD; and- by the AP MLD, refusing the association when the non-AP MLD does not request a link corresponding to the active PM AP.

19. The method of claim 18, wherein:- refusing the association request by the AP MLD comprises transmitting an association response comprising an indication indicating that the association is refused because the non-AP MLD does not request the link corresponding to the active PM AP.

20. The method of claim 19, wherein the association response further comprises the link identifier of the link operated by the Active PM AP.

21. A method of communication in a wireless network, the method comprising:- by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, receiving an association request from a non-AP MLD; and- transmitting a ML Probe Response comprising an indication indicating which of its affiliated APs operate as an active PM AP.

22. The method of claim 21, wherein the indication is an Active PM AP field in an UHR capabilities field of the ML Probe Response.

23. The method of claim 22, wherein the Active PM AP field is further comprised in each per-STA profile sub element of a Basic ML element of the ML Probe Response.

24. A method of communication in a wireless network, the method comprising:- by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, the AP MLD with one of its affiliated AP stations operating as an active PM AP, receiving an association request from a non-AP MLD that does not advertise the support of AP PM mechanism; and- accepting the association of the non-AP MLD when the non-AP MLD only request the link associated with the active PM AP.

25. A method of communication in a wireless network, the method comprising:- by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, the two different operating modes being an AP MLD active mode where all affiliated AP station of the AP MLD operate in AP active mode, and an AP MLD Power Save mode where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLD operates in AP PS mode, receiving an association request from a non-AP MLD that does not advertise the support of AP PM mechanism;- accepting the association of the non-AP MLD; and- by the AP MLD, operating in active PM mode as long as the non-AP MLD is associated.

26. A method of communication in a wireless network, the method comprising:- by an Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the two different operating modes being an AP MLD active mode where all affiliated AP station of the AP MLD operate in AP active mode, and an AP Power Save, PS, mode where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLDoperates in AP PS mode, receiving an association request from a non-AP MLD that does not include the link associated with the active PM AP;- accepting the association of the non-AP MLD that does not include the link associated with the active PM AP; and- by the AP MLD, operating in active PM mode as long as the non-AP MLD is associated.

27. The method according to any one of Claims 4, 9 to 13 and 18 to 26, wherein the affiliated AP operating as an active PM AP has a link established with an affiliated station of each non-AP MLD.

28. A computer-readable storage medium storing instructions of a computer program for implementing a method according to any one of claims 1 to 28.

29. A computer program product for a programmable apparatus, the computer program product comprising a sequence of instructions for implementing a method according to any one of claims 1 to 28 when loaded into and executed by the programmable apparatus.

30. A computer program which upon execution causes the method of any one of claims 1 to 28 to be performed.

31. An Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, communicating in a wireless network, the AP MLD comprising a processor configured for:- advertising an operating mode among the at least two different operating modes; and- operating according to the advertised operating mode.

32. An Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, communicating in a wireless network, the AP MLD comprising a processor configured for:- receiving an association request from a non-AP MLD; and- refusing the association when the non-AP MLD does not advertise the support of AP PM mechanism.

33. An Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, the AP MLD having one of its affiliated AP stations operating as an active PM AP, communicating in a wireless network, the AP MLD comprising a processor configured for:- receiving an association request from a non-AP MLD; and- refusing the association when the non-AP MLD does not request the link corresponding to the active PM AP.

34. An Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism, the AP MLD having one of its affiliated AP stations operating as an active PM AP, the AP MLD comprising a processor configured for:- receiving an association request from a non-AP MLD that does not advertise the support of AP PM mechanism; and- accepting the association of the non-AP MLD when the non-AP MLD only request the link associated with the active PM AP.

35. An Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, the two different operating modes being an AP MLD active mode where all affiliated AP station of the AP MLD operate in AP active mode, and an AP MLD Power Save, PS, mode where the active PM AP operates in AP active mode and at least one affiliated AP of the AP MLD operates in AP PS mode, communicating in a wireless network, the AP MLD comprising a processor configured for:- receiving an association request from a non-AP MLD that does not advertise the support of AP PM mechanism;- accepting the association of the non-AP MLD; and- operating in active PM mode as long as the non-AP MLD is associated.

36. An Access Point, AP, Multi-Link Device, MLD, operating a Power Management, PM, mechanism according to two different operating modes, theAP MLD having one of its affiliated AP stations operating as an active PM AP, the two different operating modes being an AP MLD active mode where all affiliated AP station of the AP MLD operate in AP active mode, and an AP MLD Power Save, PS, mode where the active PM AP operates in AP active5 mode and at least one affiliated AP of the AP MLD operates in AP PS mode,communicating in a wireless network, the AP MLD comprising a processor configured for:- receiving an association request from a non-AP MLD that does not;- accepting the association of the non-AP MLD that does not require the 10 link associated with the active PM AP; and- operating in active PM mode as long as the non-AP MLD is associated.