Per-link (twt, r-twt) process support and state switching for emlsr or elmlr common accessory station

Abstract

The non-AP MLD operates in an EML mode applied in the set of EML links. The non-AP MLD receives a first beacon frame on a first link of the EML links through the first subsidiary station, the first beacon frame including a TBTT associated with a second beacon frame. Further, the non-AP MLD configures the first subsidiary station to be in a receive state at the TBTT to receive the second beacon frame.

Description

Technical Field

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

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

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

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

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

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

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

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

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

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

[0011] Once the EMLSR mode is activated, it allows the non-AP MLD to simultaneously listen to a set of enabled links (so-called EMLSR links, usually consisting of two enabled links) to receive an initial control frame (e.g., MU-RTS trigger frame, BSRP trigger frame) from the AP MLD to initiate frame exchange, and then perform data frame exchange with the AP MLD on only one EMLSR link at a time (usually the link via which the initial control frame is received).

[0012] This indicates that the EMLSR (or EMLMR) links are not completely independent of each other.

[0013] In addition, the non-AP MLD also has the ability to initiate frame exchange with the AP MLD on an EMLSR or EMLMR link to transmit uplink data. In this case, the STA attached to the non-AP MLD operating in EMLSR or EMLMR mode does not need to transmit an initial control frame or initial frame to initiate frame exchange with the AP MLD (untriggered UL transmission), and follows the rules defined in sections 10.3.2.4 (Setting and resetting the NAV) and 10.23.2 (HCF contention based channel access (EDCA)) to access the wireless medium specified in the IEEE802.11-2020 standard.

[0014] The EML mode mechanisms coexist with other 802.11 mechanisms. Some of them (also called "link-specific procedures") are defined on a given radio medium and therefore operate on a given link in the EMLSR (or EMLMR) links independently of the other links. This is, for example, the case of the so-called Target Wake Time (TWT) procedure or its recent adaptation, known as the Restricted Target Wake Time procedure (referred to as rTWT or R-TWT).

[0015] The implementation of EML mode may not be conducive to the efficient operation of these link-specific procedures. As an example, the network activity of a non-AP MLD on a first EMLSR (or EMLMR) link may prevent the non-AP MLD from being aware of link-specific procedures (e.g., rTWT service period) on another EMLSR (or EMLMR) link because the non-AP MLD cannot listen on the other link while operating on the first link.

[0016] There is a need to improve the coexistence of EML mode with link specific procedures. Summary of the invention

[0017] The inventors have noted that the reason why a non-AP MLD cannot participate in a link-specific procedure is that the MLD cannot receive a beacon frame announcing such a procedure on another link due to the network operation of the non-AP MLD on the first link.

[0018] It is therefore a broad object of the present invention to facilitate the reception of beacon frames. This will provide enhanced link specific procedures adapted for EML mode taking into account the use of EML mode.

[0019] In this context, a communication method in a wireless network is provided, comprising: at a non-AP MLD (non-access point multi-link device) operating in an EML (enhanced multi-link) mode applied in an EML link set,

[0020] - receiving, by a first secondary station, a first beacon frame on a first one of said EML links, said first beacon frame comprising a TBTT (Target Beacon Transmission Time) associated with a second beacon frame; and

[0021] - configuring said first secondary station to be in a receiving state at said TBTT to receive said second beacon frame.

[0022] It should be understood that the first subsidiary station operates on a first link, while one or more other subsidiary stations operate on other EML links.

[0023] Thus, regardless of any network activity on one or more of the other EML links, the non-AP MLD considers the expected time (TBTT) of the next beacon frame to be received on the first link to configure itself (at the corresponding first satellite station) in an appropriate receive mode.

[0024] As a result, reception of the next beacon frame is guaranteed, so the non-AP MLD becomes aware of any first link specific procedures advertised by the next beacon frame.

[0025] Optional features of the invention are defined below with reference to methods, whereas method features may be converted into apparatus features.

[0026] In some embodiments, configuring the first auxiliary station includes ending ongoing frame exchanges on a second one of the EML links and switching the first auxiliary station to an operational state compatible with receiving the second beacon frame.

[0027] It will be appreciated that due to the frame exchange on the second link, the first secondary station is initially in a disabled frame exchange state.

[0028] Therefore, the non-AP MLD makes a decision to stop the current frame exchange at the expected time of the next beacon frame to change the first secondary station from its disabled frame exchange state to a receiving state suitable for receiving the next beacon frame. Therefore, the interruption of frame exchange allows the beacon frame to be correctly received on the first link.

[0029] In a particular embodiment, switching to an operational state compatible with receiving said second beacon frame comprises switching said first auxiliary station to a listening operational state.This advantageously allows a second auxiliary station to listen on its respective second EML link to, for example, simultaneously receive another beacon frame.

[0030] In a particular embodiment, the second secondary station should ignore any initial frames used to trigger a frame exchange sequence on the second link that overlap in time with the first beacon frame on the first link.

[0031] It should be understood that the second auxiliary station operates on a second link that is different from the first link.

[0032] This configuration ensures that the non-AP MLD receives the entire expected beacon frame regardless of network activity on the second link.

[0033] More generally, the configuration relates to a communication method in a wireless network, comprising: at a non-AP MLD (non-access point multi-link device) operating in an EML (enhanced multi-link) mode applied in an EML link set,

[0034] The second subordinate station of the non-AP MLD is configured to ignore any received initial frames that trigger a frame exchange sequence on a second one of the EML links and overlap in time with beacon frames received by the first subordinate station of the non-AP MLD on a first one of the EML links.

[0035] In a particular embodiment, switching to an operational state compatible with receiving the second beacon frame includes switching the first auxiliary station to an enabled frame exchange state. This configuration prevents a non-AP MLD receiving the beacon frame from switching on the second link (e.g., when the AP MLD sends an initial (control) frame on the second link simultaneously with the second beacon frame).

[0036] In some embodiments, configuring the first auxiliary station comprises switching the first auxiliary station from a listening state of operation to a frame exchange enabled state. Again, this prevents non-AP MLDs receiving the beacon frame from switching on the second link (e.g. when the AP MLD sends an initial (control) frame on the second link simultaneously with the second beacon frame).

[0037] In some embodiments, configuring the first auxiliary station comprises ending an ongoing frame exchange on the first link and maintaining the first auxiliary station in a frame exchange enabled state.

[0038] This means that the first secondary station does not switch back to the listening operation state once the frame exchange ends. The frame exchange end may correspond to the end of an acquired transmission opportunity or may be actively triggered by the non-AP MLD to configure itself to receive a second beacon frame due to the approaching time of the TBTT.

[0039] These embodiments avoid useless state switching of the secondary stations while ensuring correct reception of beacon frames.

[0040] In a specific embodiment, if the time distance from the end of frame exchange to TBTT is less than a predefined threshold, the first auxiliary station is maintained in the frame exchange enabled state. For example, the predetermined threshold is at least the sum of the following:

[0041] - a transition period required for the non-AP MLD to switch the state of its subordinate stations from the listening operation state to the frame exchange enabled state or the frame exchange disabled state; and

[0042] - A transition period required for the non-AP MLD to switch the state of its subordinate stations from the enabled frame exchange state or the disabled frame exchange state to the listening operation state.

[0043] This allows fine-grained control over which non-AP MLDs may benefit from remaining in a frame exchange enabled state, and which non-AP MLDs that terminate frame exchange may still attempt to have network activity on the second link. Thus, utilization of the wireless network is improved.

[0044] In some embodiments, configuring the first auxiliary station is triggered at least a first determined delay ahead of the TBTT. For example, the first determined delay belongs to the group consisting of: an EMLSR active switching delay, an EMLMR active switching delay, and the maximum of the EMLSR active switching delay and the EMLMR active switching delay. This configuration ensures that the first auxiliary station is in a receiving state at the TBTT, which means that the first auxiliary station can correctly receive the expected second beacon frame.

[0045] In some embodiments, the second beacon frame schedules a service period on the first link, and when frame exchange ends within the service period, the first auxiliary station is maintained in the frame exchange enabled state until the service period ends. In this configuration, the first auxiliary station no longer automatically switches back to the listening operation state once the frame exchange ends, but continues to be in the frame exchange enabled state until the entire service period (e.g., rTWT SP) ends. This increases the chances of non-APMLDs exchanging frames during the service period, thereby improving network efficiency.

[0046] In some embodiments, the second beacon frame schedules a service period on the first link, and switches the first auxiliary station to an enabled frame exchange state before the service period begins, and maintains the first auxiliary station in the enabled frame exchange state until the service period ends. In this configuration, the first auxiliary station is in the enabled frame exchange state throughout the service period (e.g., rTWT SP). This increases the chances of non-AP MLDs exchanging frames during the service period, thereby improving network efficiency.

[0047] In a particular embodiment, the method comprises, at the end of said service period, switching said first secondary station from said enabled frame exchange state to a listening operation state.

[0048] In some embodiments, the second beacon frame includes other TBTTs related to a third beacon frame for scheduling a TWT service period on the first link, and, while signaling the scheduled TWT service period with TWT persistence, continuing frame exchange by the second auxiliary station on the second link in the EML link without configuring the first auxiliary station to be in a receiving state at the other TBTTs to receive the third beacon frame on the first link.

[0049] It should be understood that TWT persistence (Broadcast TWT persistence field in TWT element) indicates the number of TBTTs for which there are broadcast TWT service periods corresponding to the broadcast TWT parameter set. Since the TWT service period is repeated, the non-AP MLD does not need to obtain the next beacon frame announcing the same information. Therefore, these embodiments avoid network activity on the second link from being interrupted. This improves network efficiency.

[0050] In some embodiments, the second beacon frame schedules a silent period on the first link, and during the silent period, the first auxiliary station is switched to a disabled frame exchange state until the end of the silent period. This means that during the silent period, the second auxiliary station operating on the second link in the EML link is switched to an enabled frame exchange state until the end of the silent period. Therefore, the non-AP MLD can quickly start frame exchange on the second link, thereby improving network efficiency.

[0051] In some embodiments, the method further comprises: transmitting, by the non-AP MLD to the AP MLD, an indication for scheduling a service period for the non-AP MLD in a future beacon frame, the service period not overlapping in time with any beacon frame transmitted by the APMLD on a second link in the EML link. Such indication ensures that the non-AP MLD will be able to receive beacon frames on the second link regardless of the service period scheduled on the first link.

[0052] The present invention also relates to a communication method in a wireless network, comprising: at an AP MLD (Access Point Multi-Link Device) configured to perform a frame exchange operation with at least a given non-AP MLD operating in an EML mode applied to an EML (Enhanced Multi-Link) link set,

[0053] A service period for the given non-AP MLD is scheduled in a beacon frame transmitted by the AP MLD on a first one of the EML links, the service period not overlapping in time with any beacon frame transmitted by the AP MLD on a second one of the EML links.

[0054] Therefore, the scheduled service period (eg, rTWT SP) is no longer an obstacle for the non-AP MLD to correctly receive the beacon frame.

[0055] The present invention also relates to a communication method in a wireless network, comprising: at an AP MLD (Access Point Multi-Link Device) configured to perform a frame exchange operation with a non-AP MLD operating in an EML mode applied to an EML (Enhanced Multi-Link) link set,

[0056] transmitting an initial frame for triggering a frame exchange sequence with at least one non-AP MLD operating in EMLSR mode and at least one non-AP MLD operating in EMLMR mode,

[0057] The AP MLD ensures that a padding duration of a Padding field of the initial frame is greater than or equal to a maximum value of a value indicated in an EMLSR Padding Delay subfield and an EMLMR Delay subfield received from the non-AP MLD with which the frame exchange sequence is initiated.

[0058] Therefore, the AP MLD can trigger both one or more non-AP MLDs operating in EMLSR mode and one or more non-AP MLDs operating in EMLMR mode, while ensuring that the filling duration indicated in the initial frame (IC frame in EMLSR mode and initial frame in EMLMR mode) is sufficient to allow all these non-AP MLDs (one or more non-AP MLDs operating in EMLSR mode or one or more non-AP MLDs operating in EMLMR mode) to switch the state of their subordinate stations from the listening operation state to the enable / disable frame exchange state.

[0059] Relatedly, the present invention also provides a wireless communication device, which includes at least one microprocessor configured to execute any method as described above.

[0060] Another aspect of the present invention relates to a non-transitory computer-readable medium storing a program which, when executed by a microprocessor or a computer system in a wireless device, causes the wireless device to perform any of the methods described above.

[0061] At least a portion of the method according to the invention may be computer-implemented. Thus, the invention may take the form of a fully hardware embodiment, a fully software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, which may be collectively referred to herein as "circuits," "modules," or "systems." Furthermore, the invention may take the form of a computer program product embodied in any tangible medium of expression having a computer-usable program code embodied in the medium.

[0062] Since the present invention can be implemented in software, the present invention can be embodied as computer readable code for providing to a programmable device on any suitable carrier medium. Tangible, non-transitory carrier media may include storage media such as floppy disks, CD-ROMs, hard disk drives, magnetic tape devices, or solid-state memory devices. Transient carrier media may include signals such as electrical signals, electronic signals, optical signals, acoustic signals, magnetic signals, or electromagnetic signals (e.g., microwave or RF signals). BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which:

[0064] Figure 1 A typical 802.11 network environment involving ML transmission between MLDs with EML capability in which the present invention may be implemented is illustrated;

[0065] Figure 1a and Figure 1b An exemplary 802.11be multi-link reference model illustrating MLD for AP MLD or non-AP MLD;

[0066] Figure 2 Schematically illustrating an exemplary frame sequence of the EMLSR mode of operation as specified in the D2.0 standard;

[0067] Figure 3 Illustrate a format of a target wake time (TWT) element suitable for use with r-TWT according to the D2.0 standard;

[0068] Figure 4 Using a frame sequence to illustrate an EMLSR mode of operation in a non-AP MLD that has negotiated rTWT service with its AP MLD on one of its EMLSR links according to a particular embodiment of the present invention;

[0069] Figure 5 Using a flow chart to illustrate the steps performed by the EMLSR active non-AP MLD according to an embodiment of the present invention;

[0070] Figure 6aAn enhanced frame exchange sequence for a TWT mechanism supported by an EMLSR station according to a first embodiment of the present invention is presented;

[0071] Figure 6b An enhanced frame exchange sequence for a TWT mechanism supported by an EMLSR station according to a second embodiment of the present invention is presented;

[0072] Figure 6c Presenting an enhanced frame type exchange sequence regarding a TWT mechanism supported by an EMLSR station according to a third embodiment of the present invention;

[0073] Figure 7 Using a flow chart to illustrate the steps performed by an EMLSR-active non-AP MLD when a TWT service has been set up before an EML operation is to be activated;

[0074] Figure 8 Using a flow chart to illustrate the steps performed by a non-AP MLD that intends to limit the use of EMLSR activities for TWT services on a given number of links;

[0075] Fig. 9 The architecture of the EMLSR capability for MLD used to implement the embodiment of the present invention is schematically illustrated;

[0076] Figure 9a Schematically illustrating the architecture for implementing the EMLMR capability for MLD according to an embodiment of the present invention; and

[0077] Fig.10 A schematic diagram showing a wireless communication device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0078] The technology described herein can be used in various broadband wireless communication systems, including communication systems based on orthogonal multiplexing schemes. Examples of such communication systems include space division multiple access (SDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency division multiple access (SC-FDMA) systems. SDMA systems can use sufficiently different directions to simultaneously transmit data belonging to multiple user terminals (i.e., wireless devices or STAs). TDMA systems can allow multiple user terminals to share the same frequency channel by dividing the transmission signal into different time slots or resource units, and each time slot is assigned to a different user terminal. OFDMA systems use orthogonal frequency division multiplexing (OFDM), which is a modulation technique that divides the entire system bandwidth into multiple orthogonal subcarriers or resource units. These subcarriers can also be referred to as frequency modulation, frequency bands, etc. With OFDM, each subcarrier can be modulated independently using data. An SC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit on subcarriers distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on blocks of adjacent subcarriers, or enhanced FDMA (EFDMA) to transmit on multiple blocks of adjacent subcarriers.

[0079] The teachings herein may be incorporated into (e.g., implemented in or performed by) various devices (e.g., STAs). In some aspects, a wireless device or STA implemented according to the teachings herein may include an access point (so-called AP) or may not include an access point (so-called non-AP STA or STA).

[0080] Although the examples are described in the context of a WiFi (RTM) network, the invention may be used with any type of wireless network, such as a mobile phone cellular network implementing very similar mechanisms.

[0081] An AP may include, be implemented as, or be referred to as a Node B, a radio network controller (“RNC”), an evolved Node B (eNB), a 5G next-generation base STA (gNB), a base STA controller (“BSC”), a base transceiver STA (“BTS”), a base STA (“BS”), a transceiver function (“TF”), a radio router, a radio transceiver, a basic service set (“BSS”), an extended service set (“ESS”), a radio base STA (“RBS”), or some other terminology.

[0082] A non-AP STA may include, be implemented as, or be referred to as a subscriber STA, a subscriber unit, a mobile STA (MS), a remote STA, a remote terminal, a user terminal (UT), a user agent, a user device, a user equipment (UE), a user STA, or some other terminology. In some implementations, a STA may include a cellular phone, a cordless phone, a session initiation protocol ("SIP") phone, a wireless local loop ("WLL") STA, a personal digital assistant ("PDA"), a handheld device with wireless connection capabilities, or some other suitable processing device connected to a wireless modem. Thus, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or a smart phone), a computer (e.g., a laptop computer), a tablet computer, a portable communication device, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a global positioning system (GPS) device, or any other suitable device configured to communicate via a wireless or wired medium. In some aspects, a non-AP STA may be a wireless node. Such a wireless node may provide, for example, connectivity to or from a network (eg, a wide area network such as the Internet or a cellular network) via a wired or wireless communication link.

[0083] The AP manages a collection of STAs (STAs registered to or associated with the AP) that organize their access to the wireless medium together for communication purposes. The STAs (including the APs to which they are registered) form a service set, hereinafter referred to as a basic service set (BSS) (although other terms may be used). The same physical STA used as an access point may manage two or more BSSs (and therefore corresponding WLANs): each BSS is therefore uniquely identified by a specific basic service set identifier (BSSID) and managed by a separate virtual AP implemented in the physical AP. Each STA is identified within the BSS due to an identifier (AID) assigned to the STA by the AP at registration.

[0084] The 802.11 family of standards defines various Medium Access Control (MAC) mechanisms to drive access to the wireless medium.

[0085] Current discussions in task group 802.11be introduce multi-link operation (MLO) when it comes to MAC layer operations, as shown in the draft IEEE P802.11be / D2.0 in May 2022. MLO allows multi-link devices to establish or set up multiple links and operate them simultaneously.

[0086] A multi-link device (MLD) is a logical entity and has more than one subordinate STA (STA) and has a single medium access control (MAC) service access point (SAP) for a logical link control (LLC), which includes one MAC data service. An access point multi-link device (or AP MLD) then corresponds to an MLD in which the individual STAs subordinate to the MLD are APs and are therefore referred to as "subordinate APs." A non-access point multi-link device (or non-AP MLD) corresponds to an MLD in which the individual STAs subordinate to the MLD are non-AP STAs and are therefore referred to as "subordinate non-AP STAs." According to the text, "multi-link device," "ML device" (MLD), "multi-link logical entity," "ML logical entity" (MLE), "multi-link set," and "ML set" are synonyms for the same type of ML device. Reference is made below to Figure 1a and Figure 1b An example architecture of a multi-link device is described below.

[0087] Then, multiple subordinate non-AP STAs of the non-AP MLD may set up communication links with multiple subordinate APs of the AP MLD, thereby forming a multi-link channel.

[0088] The links established for MLD (or enabling links) are theoretically independent, which means that the channel access process (to the communication medium) and the communication are performed independently on each link. Therefore, different links can have different data rates (e.g., due to different bandwidths, number of antennas, etc.) and can be used to communicate different types of information (each through a specific link).

[0089] Thus, a communication link or "link" corresponds to a given channel (eg, 20 MHz, 40 MHz, etc.) in a given frequency band (eg, 2.4 GHz, 5 GHz, 6 GHz) between an AP attached to an AP MLD and a non-AP STA attached to a non-AP MLD.

[0090] The attached APs and non-AP STAs operate on their respective channels according to one or more of the IEEE 802.11 standards (a / b / g / n / ac / ad / af / ah / aj / ay / ax / be) and other wireless communication standards.

[0091] Due to multi-link aggregation, traffic associated with a single MLD can theoretically be transmitted across multiple parallel communication links, thereby increasing network capacity and maximizing the utilization of available resources.

[0092] From an architectural perspective, an MLD typically contains a number of radios to implement its affiliated STAs, but not necessarily a number equal to the number of its affiliated STAs. In particular, a non-AP MLD may operate with a greater number of affiliated STAs than the number of radios (which may even be reduced to a single radio).

[0093] From this physical architecture, the D2.0 standard has defined several enhanced multi-link operation modes (or EML OM for short), namely Enhanced Multi-Link Single Radio (EMLSR) and Enhanced Multi-Link Multi-Radio (EMLMR). The D2.0 standard states that the two EMLSR and EMLMR modes are mutually exclusive.

[0094] Any non-AP MLD declares its support for EMLSR and / or EMLMR mode (in its so-called EML capabilities) to the AP MLD during the association phase. In operational mode, activation and deactivation of EMLSR or EMLMR mode is initiated by the non-AP MLD, which sends a specific EHT action frame called "EML OM notification", indicating the set of enabled links (so-called EMLSR or EMLMR links) for which the EMLSR or EMLMR mode is to be activated. Typically, the set "EMLSR / EMLMR links" consists of two enabled links. However, a larger number of enabled links may be used.

[0095] Once activated, the EMLSR mode allows non-AP MLDs to simultaneously listen to the enabled links of the set "EMLSR links" to receive the initial control frame (e.g., MU-RTS trigger frame or BSRP trigger frame) transmitted by the AP MLD, and then exchange data frames with the AP MLD on only one link at a time (usually the link via which the initial control frame is received). Individual non-AP MLDs may or may not support the EMLSR capable operating mode.

[0096] In EMLMR mode, a non-AP MLD is able to aggregate some physical resources of multiple radios dedicated to multiple enabled links (so-called EMLMR links) to transmit or receive data up to a predefined number of supported Rx / Tx spatial streams. This predefined number is higher than the number of supported Rx / Tx spatial streams for each radio, thereby providing throughput enhancement and latency reduction. As an example, a multi-radio (MR) non-AP MLD supporting EMLMR mode on two links (with associated radios) uses the two corresponding radios to communicate on the two links when the EMLMR mode is deactivated (e.g., in a 2×2 MIMO antenna configuration of each radio). On the other hand, a MR non-AP MLD uses a radio with aggregated physical resources of two radios (usually antennas) in its radio to communicate on one of the two links when the EMLMR mode is activated (e.g., in a 4×4 MIMO antenna configuration). At the same time, the other link (deprived of a physical antenna) cannot be used.

[0097] Once activated, the EMLMR mode allows non-AP MLDs to simultaneously listen to the enabled links of the set "EMLMR links" to receive the initial frame transmitted by the AP MLD to initiate frame exchange, and then exchange data frames with the AP MLD on only one EMLMR link (of the aggregated radio resources) at a time (usually the link via which the initial frame is received).

[0098] For ease of explanation, the following description focuses primarily on the EMLSR mode. However, similar considerations can be made with respect to the EMLMR mode.

[0099] Figure 1 A typical 802.11 network environment involving ML transmission between EML-capable MLDs (EMLSRs and / or EMLMRs) is illustrated in which the present invention may be implemented.

[0100] The wireless communication network 100 involves an AP MLD 110 and two non-AP MLDs 120 and 130. In this example, the two non-AP MLDs are considered to be EML-capable and have declared their respective capabilities to the AP MLD 110 within the EMLSR-related field and the EMLMR-related field of the EML-capability (these fields are referred to below as EMLSR-capability and EMLMR-capability (i.e., sub-parts of the EML-capability)). Of course, another number of non-AP MLDs that register with the AP MLD 110 and then exchange frames with it, as well as another (larger) number of non-AP MLDs that are EML-capable, can be envisioned.

[0101] AP MLD 110 has multiple subordinate APs. Figure 1There are two attached APs 111 and 112 (also labeled as AP1 and AP2, respectively), each attached AP behaves as an 802.11 AP on its operating channel within a frequency band. Known 802.11 frequency bands include 2.4 GHz band, 5 GHz band and 6 GHz band. Of course, other frequency bands can be used to replace or supplement these three frequency bands.

[0102] The non-AP MLD 120, 130 has multiple subordinate non-AP STAs, each of which appears as an 802.11 non-AP STA in the BSS in which it is registered (managed by the subordinate AP 111 or 112). Figure 1 , two non-AP STAs 121 and 122 (also labeled as A1 and A2, respectively) are attached to the non-AP MLD 120, and two non-AP STAs 131 and 132 (also labeled as B1 and B2, respectively) are attached to the non-AP MLD 130.

[0103] For the purpose of illustration, non-AP MLDs 120 and 130 are single radio non-AP MLDs. For example, AP 111 is set to operate on channel 38 corresponding to a 40 MHz operating channel in the 5 GHz band, and AP 112 is also set to operate on channel 151 corresponding to another 40 MHz operating channel in the 5 GHz band. In another example, the affiliated STAs may operate on different frequency bands.

[0104] Each subordinate AP provides a link toward the AP MLD 110 to the subordinate non-AP STA of the non-AP MLD (120 or 130). Therefore, the link of each non-AP MLD can be identified only with the identifier of each subordinate AP. In this context, each subordinate AP 111 and 112 can be identified by an identifier called a "link ID". The link ID of each subordinate AP is unique and does not change during the life cycle of the AP MLD. The AP MLD can assign link IDs to its subordinate APs by incrementing the ID from 0 (for the first subordinate AP). Of course, other terms such as "AP ID" and the like can be used in variations.

[0105] In order to perform multi-link communication, each non-AP MLD 120, 130 must discover, authenticate, associate and set up multiple links with the AP MLD 110, each link being established between an AP affiliated with the AP MLD 110 and a non-AP STA affiliated with the non-AP MLD. Each such link, referred to as an enabling link, enables respective channel access and frame exchanges between the non-AP MLD and the AP MLD based on the supported capabilities exchanged during association.

[0106] The discovery phase is referred to below as the ML discovery procedure, and the multi-link setup phase (or association phase) is referred to below as the ML setup procedure.

[0107] The ML discovery process allows a non-AP MLD to discover the wireless communication network 100, i.e., various links to the AP MLD provided by multiple subordinate APs. The ML discovery process therefore seeks various subordinate APs advertising the AP MLD and corresponding network information, such as including all or part of the capabilities and operating parameters. Once the non-AP MLD has discovered the wireless communication network 100 through the ML discovery process, and after the MLD authentication process, the ML setup process allows the non-AP MLD to select a set of candidate setup links between its own subordinate non-AP STAs and some of the discovered subordinate APs, and request the AP MLD 110 to establish these links, which may be accepted or rejected by the AP MLD. If the AP MLD accepts, the non-AP MLD is provided with an association identifier (AID) by the AP MLD, which is used by the subordinate non-AP of the non-AP MLD to communicate wirelessly with its corresponding subordinate APs over multiple links (communication channels). During the ML setup process, the non-AP MLD declares some or all of its capabilities. For example, the non-AP MLD can declare its EMLSR capabilities. For this purpose, appropriate fields are provided in the management frame. In particular, some management frames exchanged during the ML discovery and ML setup procedures contain new information elements specific to multilink operation (MLO), referred to as basic multilink elements. In fact, in all management frames including basic multilink elements except authentication frames, a non-AP or AP MLD with EMLSR capability (dot11EHTEMLSROptionImplemented equal to true) or EMLMR capability (dot11EHTEMLMROptionImplemented equal to true) sets the EMLSR or EMLMR Support bit to 1 in the EML Capability subfield of the Common Information field.

[0108] For the purpose of illustration, in the wireless communication network 100, during the ML setup process, two candidate setup links have been requested by the non-AP MLD 120 and accepted by the AP MLD 110: a first link 151 between the attached AP 111 (AP1) and the attached non-AP STA 121 (A1), and a second link 152 between the attached AP 112 (AP2) and the attached non-AP STA 122 (A2). Similarly, two candidate setup links have been requested by the multi-radio non-AP MLD 130 and accepted by the AP MLD 110: a first link 161 between the attached AP 111 (AP1) and the attached non-AP STA 131 (B1), and a second link 162 between the attached AP 112 (AP2) and the attached non-AP STA 132 (B2).

[0109] AP MLD 110, non-AP MLD 120 and non-AP MLD 130 are considered to be EMLSR capable (dot11EHTEMLSROptionImplemented equals true) or EMLMR capable (dot11EHTEMLMROptionImplemented equals true). They exchange their EMLSR or EMLMR capabilities (sub-part of EML capabilities) during their ML discovery process and multi-link setup phase.

[0110] As currently defined in the D2.0 standard, the EMLSR and EMLMR capabilities include the following subfields:

[0111] - "EMLSR Support" subfield, which indicates support for EMLSR operation of MLD. If MLD supports EMLSR operation, the EMLSR Support subfield is set to 1; otherwise, the subfield is set to 0;

[0112] - "EMLSR Stuffing Delay" 3-bit subfield, which indicates the minimum MAC stuffing duration of the padding field of the initial control frame requested by the non-AP MLD (as defined in Enhanced Multilink Single Radio Operation (Section 35.3.17)). The table converts the 3-bit value to the stuffing delay in μs. This delay is used to define the transition period required for the MLD to switch the state of its subordinate stations from the listening operation state to the enable / disable frame exchange state. As described below, the transition period consists of this delay added to the time length of the initial control frame response. Therefore, this transition period is called "EMLSR active switching delay";

[0113] - "EMLSR Transition Delay" 3-bit subfield, which indicates the transition delay time required for the non-AP MLD to switch from the so-called frame exchange mode (on one of the enabled links) to the so-called listening mode of operation for the enabled links. The table converts the 3-bit value to a delay in μs. For example, it is set to 0 for 0 μs, 1 for 16 μs, 2 for 32 μs, 3 for 64 μs, 4 for 128 μs, 5 for 256 μs, and the values ​​6 to 7 are reserved;

[0114] - "EMLMR Support" subfield, which indicates support for EMLMR operation for the MLD. If the MLD supports the EMLMR operation, the EMLMR Support subfield is set to 1; otherwise, the field is set to 0;

[0115] - "EMLMR Delay" 3-bit subfield, which indicates the minimum padding duration required for EMLMR link switching when the non-AP MLD is operating in EMLMR mode. This delay is used to define the transition period required for the MLD to switch the state of its subordinate stations when starting or ending a frame exchange. As described below, the transition period for the start of a frame exchange consists of this delay (EMLMR Delay) added to the time length of the initial control frame response. Therefore, this start transition period is hereinafter referred to as "EMLMR Active Switch Delay".

[0116] - A "Transition Timeout" subfield indicates the timeout value for the exchange of EML operation mode notification frames in the EMLSR (or EMLMR).

[0117] When a non-AP MLD with EMLSR (respectively, EMLMR) capability intends to operate in a corresponding mode on a set of enabled links (referred to as EMLSR (respectively, EMLMR) links), a STA attached to the non-AP MLD transmits an EMLSR (respectively, EMLMR) Mode subfield of the EML Control field to an AP attached to an AP MLD with EMLSR (respectively, EMLMR) capability (here, AP MLD 110) (specified in the D2.0 standard) with an EMLSR (respectively, EMLMR) Mode subfield set to 1. The EMLSR (respectively, EMLMR) links are indicated in the EMLSR (respectively, EMLMR) Link Bitmap subfield of the EML Control field of the EML OM notification frame by setting the bit position of the EMLSR (respectively, EMLMR) Link Bitmap subfield to 1 for each EMLSR (respectively, EMLMR) link. For example, in the EMLSR (respectively, EMLMR) bitmap, bit position i corresponds to the link with link ID equal to i and is set to 1 to indicate that the link is a member of the EMLSR (respectively, EMLMR) links.

[0118] The AP affiliated with the AP MLD that receives the EML operation mode notification frame from the STA affiliated with the non-AP MLD then transmits the EML operation mode notification frame to one of the STAs affiliated with the non-AP MLD within the timeout interval indicated in the transition timeout subfield in the EML capability subfield of the basic multilink element (which starts from the end of the PPDU transmitted by the AP affiliated with the AP MLD) as an acknowledgment of the EML operation mode notification frame transmitted by the STA affiliated with the non-AP MLD.

[0119] After a STA attached to the non-AP MLD successfully transmits an EML operation mode notification frame on one of the EMLSR (respectively, EMLMR) links, the non-AP MLD operates in the EMLSR (respectively, EMLMR) mode, which is considered to be EMLSR active (respectively, EMLMR active).

[0120] When a non-AP MLD with EMLSR capability intends to disable the EMLSR (respectively, EMLMR) mode, the STA attached to the non-AP MLD transmits an EML operation mode (OM) notification frame (specified in the D2.0 standard) with the EMLSR (respectively, EMLMR) mode subfield of the EML control field set to 0 to the AP attached to the AP MLD. Again, the AP attached to the AP MLD, which receives the EML operation mode notification frame from the STA attached to the non-AP MLD, transmits the EML operation mode notification frame as an acknowledgment of the EML operation mode notification frame as described above. After the STA attached to the non-AP MLD successfully transmits the EML operation mode notification frame on one of the EMLSR (respectively, EMLMR) links, the non-AP MLD disables the EMLSR (respectively, EMLMR) mode.

[0121] The set of STAs affiliated to a non-AP MLD with EMLSR (respectively, EMLMR) capability operating on an EMLSR (respectively, EMLMR) link may be all or part of the STAs affiliated to the non-AP MLD. The STAs of this set are hereinafter referred to as "EMLSR co-affiliated STAs" (respectively, EMLMR co-affiliated STAs) of the non-AP MLD.

[0122] exist Figure 1 In the example of FIG. 4 , the EMLSR common affiliated STAs of the non-AP MLD 120 and the non-AP MLD 130 operate on the same link (ie, have the same affiliated AP, AP1 and AP2), which means that these STAs share the same EMLSR link.

[0123] Figure 1a An exemplary 802.11be multi-link reference model illustrating MLD for AP MLD or non-AP MLD.

[0124] The MLD includes a PHY layer 200, a MAC layer 220, a logical link control (LLC) sublayer, and an upper layer.

[0125] The upper layer may include applications that generate traffic data or use received traffic data.

[0126] The transmission and reception of traffic data is handled by the MAC 220 and PHY 200 layers. Such transmission and reception of traffic data may be performed over multiple links 20-x, 20-y, 20-z (see reference Figure 1 The transmission is performed on the incoming links 151, 152, 161, 162). Three links and therefore three auxiliary stations are shown. Of course, other configurations including two auxiliary stations or more than three auxiliary stations can be envisaged.

[0127] Traffic data is provided by upper layers as a sequence of data frames or "traffic flows". Each traffic flow, and therefore each data frame, is associated with an access category (AC) defined in the EDCA mechanism ( Figure 1b ). This mapping between flows or data frames and ACs is performed by classifier 213.

[0128] Recall that 802.11 stations (AP and non-AP stations) maintain four access categories (ACs), each with one or more corresponding transmission buffers or queues. The four ACs are generally defined as follows:

[0129] -AC1 and AC0 are reserved for best effort and background traffic. They have the second-lowest priority and the lowest priority respectively.

[0130] - AC3 and AC2 are usually reserved for real-time applications (eg, voice or video transmission). They have the highest priority and the second-to-last priority, respectively.

[0131] Data frames incoming from the upper layers of the protocol stack, known as MAC Service Data Units (MSDUs), are mapped onto one of the four ACs by the classifier 213 and are thus entered into the queue of the mapped AC.

[0132] Figure 1b An implementation model with four transmit queues (one for each access category) is illustrated.

[0133] The 802.11be multi-link reference model reflects the fact that an MLD may use several links for transmission and reception (particularly at the MAC layer 220 and PHY layer 200 levels).

[0134] The MAC layer 220 includes a unified upper MAC (UMAC) layer 230, and multiple lower MAC (LMAC) layers 220-x, 220-y, 220-z coupled with corresponding PHY layers 200-x, 200-y, 200-z, each coupling corresponding to the links 20-x, 20-y, 20-z.

[0135] The UMAC 230 performs functions that are common across all links, and each LMAC 220-x, 220-y, 220-z performs functions that are local to each link 20-x, 20-y, 20-z. The UMAC layer then provides a UMAC interface with the link-specific blocks 220-x, 220-y, 220-z, and also provides a UMAC Service Access Point (SAP) to the LLC and upper layers.

[0136] The UMAC 230 is responsible for link-agnostic MAC processes such as authentication, association, security association, sequence number allocation, MAC protocol data unit (MPDU) encryption / decryption, aggregation / deaggregation, confirmation score boarding process, etc.

[0137] Each data unit (MSDU) with a traffic type (user priority (UP), and thus traffic identifier (TID)) priority, arriving at the MAC layer 220 from an upper layer (e.g., link layer) is mapped onto one of the ACs according to a mapping rule at the UMAC layer 230. Then, still at the UMAC layer 230, the data unit (MSDU) is provided with the next available sequence number and is stored in a queue corresponding to its TID (or UP) within the mapped AC.

[0138] Each LMAC 220-x, 220-y, 220-z is responsible for link-specific functions such as channel access. In particular, each MLD MAC includes its own contention-based channel access process, such as EDCA 221-x, 221-y, 221-z. Some functions require joint processing of both the UMAC 230 and the LMAC 220-x, 220-y, 220-z.

[0139] like Figure 1a and Figure 1b As shown, each EDCA 221-x, 221-y, 221-z of each link competes for each queue for each link. In this regard, each AC has its own set of queue competition parameters for each link, and is associated with a priority value, thus defining higher or lower priority traffic for the MSDU. Therefore, for a given link, there are multiple traffic queues for serving data traffic at different priorities. The contention window (CW) and backoff value are known as EDCA variables and are specific to each link 20-x, 20-y, 20-z.

[0140] This means that each AC acts as an independent DCF competing entity on a given link (including its corresponding queue backoff engine 211). Therefore, each queue backoff engine 211 is associated with a corresponding traffic queue 210 to initialize a corresponding queue backoff counter dedicated to each AC and each link using queue competition parameters and drawing a backoff value (from the CW). The backoff counter is used to compete for access to the link 20-x, 20-y or 20-z to transmit data stored in the queue of the AC. In practice, when the medium is idle, the backoff counter is decremented from its initialization value, and when the backoff counter reaches 0, the corresponding affiliated STA201-x, 201-z is allowed to transmit (access is granted).

[0141] When access to the wireless medium is granted for an AC on a link, the MSDU stored for that AC is transmitted to the physical (PHY) layer 200-x, 200-y, 200-z for transmission on the link.

[0142] Figure 2 The frame sequence is used to illustrate the EMLSR mode of operation in the non-AP MLD 120 when the AP MLD 110 decides to use the EMLSR mode. Of course, although the EMLSR mode is emphasized here by way of example, similar considerations can be made with respect to the EMLMR mode.

[0143] In this sequence, the non-AP MLD operates in the EMLSR mode, which means that an EML operation mode notification frame activating the EMLSR mode has been successfully transmitted by the affiliated STA of the non-AP MLD 120. In other words, the non-AP MLD has entered an active enhanced multi-link single radio (EMLSR) mode applied to a specific set of two or more enabled links.

[0144] The dependent STAs 121 and 122 are EMLSR common dependent STAs within the non-AP MLD 120. Each dependent STA can be in one of three defined states: a listening operation state, a frame exchange enabled state, and a frame exchange disabled state.

[0145] The non-AP MLD 120 is able to simultaneously listen on its EMLSR links by making one or more of its EMLSR co-affiliated STAs correspond to these links in the "awake" or "listening operation" state. For example, the affiliated STAs A1, A2 are in the listening operation state (labeled as 241 and 242). The listening operation includes CCA (Clear Channel Assessment) and receiving the initial control frame of the frame exchange initiated by the AP MLD. Therefore, in the non-AP MLD 120, two EMLSR co-affiliated STAs simultaneously listen to receive the initial control frame from the AP MLD.

[0146] When the AP MLD 110 intends to initiate a frame exchange with one or more non-AP MLDs on one of the EMLSR links, the frame exchange is started by transmitting an initial control frame 245 that explicitly triggers the non-AP MLDs. To the extent possible, the initial control frame schedules the non-AP MLDs. The initial control frame for the frame exchange is sent in an OFDM PPDU or non-HT repeated PPDU format using a rate of 6 Mbps, 12 Mbps, or 24 Mbps (i.e., the MCS subfield in the frame is set to a value up to 2). As defined in the D2.0 standard, the initial control frame should be as defined in IEEE Standard 802.11ax. TM-MU-RTS trigger frame or BSRP trigger frame as defined in 2021. Given a trigger frame format, according to which such a frame includes one or more user information fields, this condition means that frame 245 includes a user information field addressed to the non-AP MLD, i.e., wherein the AID12 field is set to the AID of the non-AP MLD (obtained at registration).

[0147] In this example and as indicated by reference numeral "IC(A)", the initial control frame 245 explicitly triggers the non-AP MLDA 120. The initial control frame may explicitly trigger multiple non-AP MLDs using multiple user information fields therein.

[0148] The EMLSR co-affiliated STA of the non-AP MLD (e.g., affiliated STA A1 in the example) explicitly triggered by the initial control frame 245 of the received frame initiates the state change of the EMLSR co-affiliated STA of the non-AP MLD under consideration (e.g., the change of the state of affiliated STAs A1 and A2 in the example), and sends an initial control frame response (IC response) 246 to the AP AP1 affiliated to the AP MLD 110.

[0149] After receiving the initial control frame 245 of the frame exchange and transmitting the immediate response frame 246 as a response to the initial control frame, the STA (i.e., the receiving EMLSR co-affiliated STA A1 in the example) attached to the non-AP MLD that is listening on the corresponding link is configured to be able to transmit or receive frames on the enabled link (i.e., link 151 in the example) that received the initial control frame 245. To this end, a state switching process is called, which results in the receiving EMLSR co-affiliated STA being switched from the listening operation state 241 to the "active frame exchange" or "enable frame exchange" state (marked as 251 in the figure) after the EMLSR active switching delay. The receiving EMLSR co-affiliated STA in this new state is able to receive PPDUs sent on the link that received the initial control frame 245 by using more than one spatial stream. The EMLSR active switching delay corresponds to the delay time required for the non-AP MLD to switch from the EMLSR listening operation mode to the EMLSR frame exchange mode. As described above, this is specified in the EML capabilities (via the EMLSR padding delay) exchanged with the AP MLD.

[0150] At the same time, other EMLSR co-affiliated STAs of the same non-AP MLD (i.e., STA A2 in the example) are configured not to transmit or receive on one or more other EMLSR links until the frame exchange is completed. To this end, a state switching process is also called for other EMLSR co-affiliated STAs, which then switch from the listening operation state 242 to a "blindness frame" or "disabled frame exchange" state (marked as 252 in the figure). In particular, the APMLD does not transmit data intended for these other EMLSR co-affiliated STAs.

[0151] The state switching of all EMLSRs commonly affiliated STAs in the same non-AP MLD is inseparable and therefore simultaneous, because this is the whole radio resource chain (see below). Fig. 9 ) is allocated to one of the STAs while the other STAs are deprived of such a chain. Regarding the EMLMR mode, the physical resources (e.g., antennas) of one radio resource chain are allocated (and aggregated) to another radio resource chain, so the former is deprived of transmission / reception capabilities (see below Figure 9a ).

[0152] The above shows that when the non-AP MLD operates in EMLSR mode (and more generally in either EMLSR and EMLMR modes), it is in a listening operation mode (its co-affiliated STAs are in a listening operation state) or a frame exchange mode (one of its co-affiliated STAs is in an enabled frame exchange state, while the other co-affiliated STAs are in a disabled frame exchange state).

[0153] The simultaneous state change is required because in EMLSR mode, only a single full radio resource allocated to the receiving EMLSR co-affiliated STA is available (see below for details). Fig. 9 In EMLMR mode, antenna resources of one radio stack are allocated to another radio stack (as described below). Figure 9a as described).

[0154] As a result, only one of the EMLSR co-affiliated STAs that is not the AP MLD that is explicitly triggered can exchange data frames with the AP MLD at a time; this is typically the EMLSR co-affiliated STA that received the initial control frame 245 .

[0155] exist Figure 2 An exemplary frame exchange sequence is shown in , which comprises the sending of an A-MPDU frame 255 by the subordinate AP AP1 to the explicitly triggered EMLSR co-subordinate STA A1 of the non-APMLD A120 (hence a downlink transmission), followed by a corresponding block acknowledgment 256 from the latter.

[0156] After the frame exchange operated by the receiving EMLSR co-affiliated STA ends plus the EMLSR transition delay specified in the EML capability, the non-AP MLD 120 switches back to the EMLSR listening operation state, which means that the receiving EMLSR co-affiliated STA A1 switches back to the listening operation state 241 and the other EMLSR co-affiliated STA A2 switches back to (listening operation state 242). Therefore, the state switching process is called for each EMLSR co-affiliated STA.

[0157] The non-AP MLD (here, non-AP MLD 120) may sense the end of the frame exchange if one of the following conditions is met:

[0158] (1) The MAC of the STA attached to the non-AP MLD that received the initial control frame 245 does not receive the PHY-RXSTART.indication primitive during the timeout interval of aSIFSTime+aSlotTime+aRxPHYStartDelay, which starts at the end of the PPDU (e.g., ACK 256) transmitted by the STA of the non-AP MLD as a response to the most recently received frame (e.g., A-MPDU frame 255) from the AP attached to the AP MLD, or starts at the end of the reception of the following PPDU, which contains a frame that does not require immediate ACK from the STA of the AP attached to the AP MLD. This indicates the end of the actual exchange with the AP MLD without receiving a subsequent frame from the AP MLD.

[0159] (2) The MAC of the STA attached to the non-AP MLD that received the initial control frame 245 receives the PHY-RXSTART.indication primitive during the timeout interval of aSIFSTime+aSlotTime+aRxPHYStartDelay, which timeout interval starts from the end of the PPDU (e.g., acknowledgment 256) transmitted by the STA of the non-AP MLD as a response to the most recently received frame (e.g., A-MPDU frame 255) from the AP attached to the AP MLD, or starts from the end of reception of the following PPDU, which contains a frame that does not require immediate acknowledgment from the STA of the AP attached to the AP MLD, and the STA attached to the non-AP MLD does not detect any of the following frames in the PPDU corresponding to the PHY-RXSTART.indication:

[0160] - Individually addressed frames where the RA is equal to the MAC address of the STA attached to the non-AP MLD;

[0161] - a trigger frame having one of the user information fields addressed to a STA attached to a non-AP MLD;

[0162] -CTS-to-self frame, where RA is equal to the MAC address of the AP attached to the AP MLD;

[0163] - A Multi-STA Block Ack frame with one per-AID TID information field addressed to a STA attached to a non-AP MLD;

[0164] - NDP announcement frame, which has one of the STA Information fields addressed to the STAs attached to the non-AP MLD.

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

[0166] (3) The STA attached to the non-AP MLD that receives the initial control frame 245 does not respond to the latest received frame (eg, A-MPDU frame 255) from the AP attached to the AP MLD that requires an immediate response after SIFS.

[0167] When the non-AP MLD 120 is now in the EMLSR snooping mode of operation, the AP MLD may initiate any new frame exchange sequence (with either of the non-AP MLDs 120 or 130) by transmitting a new initial control frame.

[0168] In the example of the figure, the AP MLD 110 decides to initiate again such a new sequence with the non-AP MLD 120 using its EMLSR co-affiliated STA A2 122. In detail, the AP MLD 110 transmits a new initial control frame 265IC(A) that explicitly triggers the non-AP MLD A 120 using its other affiliated AP 112, which is now received by the EMLSR co-affiliated STA A2 122. The receiving EMLSR co-affiliated STA A2 122 transmits a response frame 266 to the initial control frame 265. After the EMLSR active switching delay, the explicitly triggered non-AP MLD 120 switches to the EMLSR frame exchange mode, wherein the receiving EMLSR co-affiliated STA A2 122 switches from the listening operation state 242 to the enabled frame exchange state 272, while its other EMLSR co-affiliated STA A1 121 simultaneously switches from the listening operation state 241 to the disabled frame exchange state 271. The frames 275, 276 are then exchanged during the frame exchange sequence until the end of the sequence at which the non-AP MLD 120 switches back to the EMLSR listening mode of operation.

[0169] A-MPDU 255 / 275 is provided only for illustration. AP MLD may send other types of frames, such as basic trigger frames for triggering UL transmissions. Figure 2 A frame exchange consisting of a single frame 255 / 275 followed by an acknowledgment 256 / 276 is shown, but a simpler frame exchange may include only a single frame sent by the AP MLD without an acknowledgment, while a more complex frame exchange may include multiple exchange sequences, such as concatenated TXOPs (transmission opportunities) for UL transmissions (triggered by a basic trigger frame) and / or for DL ​​transmissions (via a HE MU PPDU).

[0170] This illustrative example shows the advantages of the EMLSR mode in terms of throughput and latency: the AP MLD can quickly switch from one link to another, thereby improving communication performance for a limited increase in complexity and cost.

[0171] In this example, AP MLD 110 initiates a frame exchange sequence with one or more designated non-AP MLDs. The D2.0 standard also allows non-AP MLDs to initiate a frame exchange sequence with an AP MLD. In other words, a STA attached to a non-AP MLD operating in EMLSR mode does not need to transmit an initial control frame to initiate a frame exchange with the AP MLD. Such an attached STA follows the rules defined in Sections 10.3.2.4 (to set and reset NAV) and 10.23.2 (HCF contention-based channel access (EDCA)) to access the wireless medium.

[0172] However, with respect to the peculiarities of the EMLSR-active MLD, in particular with respect to the status of its co-affiliated STAs, no conventional medium access mechanism (such as TWT or rTWT as described below) is defined. To review, an EMLSR-capable non-AP MLD becomes EMLSR-active after successfully exchanging an EMLSR-capable AP MLD with an EMLSR-capable AP MLD, in which the EMLSR Mode subfield of the EML Control field is set to 1 and an EMLSR link is designated, and thus a corresponding EMLSR co-affiliated STA is designated.

[0173] As described above, the foregoing description also applies to the EMLMR mode, and in particular, has the following matches in the implementation: the EMLMR delay applies to both the EMLSR filling delay and the EMLSR transition delay; the initial frame in the EMLMR mode matches the initial control frame in the EMLSR mode, and similarly, the initial frame response in the EMLMR mode matches the initial control frame response in the EMLSR mode; although not defined in the D2.0 standard, an EMLMR listening operation state / mode that matches the EMLSR listening operation state / mode may be defined (in which co-affiliated STAs listen to their links before physical radio resources are aggregated).

[0174] More generally, according to the implementation of the present invention, the following delays are defined to specify the timing for EML switching operations. The standard does not provide guidance on these timings. Some subfields of the EML Capability subfield in the common information field of the basic multilink element as specified in the standard are reused for the newly defined delays.

[0175] "EML activity switching delay"

[0176] "EML Active Switching Delay" is defined as the transition period required for a non-AP MLD to switch the state of its subordinate stations from awake or listening operation state to enabled or disabled frame exchange state. The EML Active Switching Delay ensures that the non-AP MLD has completed its switching operation before the frame exchange triggered by the AP MLD.

[0177] The delay is referred to as "EMLSR active switching delay" in the case of EMLSR operation and as "EMLMR active switching delay" in the case of EMLMR operation.

[0178] In the implementation of EMLSR activity switching delay,

[0179] EMLSR active switching delay = EMLSR filling delay + aSIFSTime + transmission time of initial control response frame, where:

[0180] "EMLSR Stuff Delay" is a 3-bit subfield of the EML Capability subfield in the Common Information field of the Basic Multilink Element;

[0181] "aSIFSTime" is the nominal time (in microseconds) required by the MAC and PHY from the reception of the end of a PPDU until the MAC and PHY have processed one or more of any frames therein and responded with the start of a PPDU containing the earliest possible response frame; and

[0182] The "transmission time of the initial control response frame" is the duration of the shortest initial control response frame used on the EMLSR link for which the EMLSR padding delay has been determined by the non-AP MLD.

[0183] In the implementation of EMLMR activity switching delay,

[0184] EMLMR active switching delay = EMLMR delay + aSIFSTime + initial response frame transmission time, where:

[0185] "EMLMR Delay" is a 3-bit subfield of the EML Capability subfield in the Common Information field of the Basic Multilink Element; and

[0186] The "transmission time of the initial response frame" is the duration of the shortest initial response frame used on the EMLMR link for which the EMLMR delay has been determined by the non-AP MLD.

[0187] “EML transition delay” (or “EML de-active switching delay”)

[0188] "EML Transition Delay" is defined as the transition period required for a non-AP MLD to switch the state of its subordinate stations from an enabled or disabled frame exchange state to an awake or listening operation state. The EML Transition Delay is useful for the AP MLD to determine when the non-AP MLD is ready to receive subsequent initial (control) frames on either of the EML links.

[0189] The delay is referred to as "EMLSR transition delay" in the case of EMLSR operation, and is referred to as "EMLMR transition delay" in the case of EMLMR operation.

[0190] In implementation, the EMLSR Transition Delay is the "EMLSR Transition Delay" 3-bit subfield of the EML Capability subfield.

[0191] In implementation, the EMLMR Transition Delay is the "EMLMR Delay" 3-bit subfield of the EML Capability subfield.

[0192] In another implementation, the EMLMR transition delay is determined as follows:

[0193] EMLMR transition delay = EMLMR delay + aSIFSTime + initial response frame transmission time; where:

[0194] "EMLMR Delay" is a 3-bit subfield of the EML Capability subfield; and

[0195] The "transmission time of the initial response frame" is the duration of the shortest initial response frame used on the EMLMR link estimated by the AP MLD.

[0196] The duration of the initial response frame may vary from one initial frame to another. The AP MLD may estimate the duration of the shortest initial response frame used on the EMLMR link (eg, the CTS frame in the non-HT PPDU with the highest rate in the BSSBasicRateSet parameter).

[0197] For a non-AP MLD in EMLSR mode, the duration for switching from awake / listening operation to frame exchange operation (EMLSR active switching delay) and the duration for switching from frame exchange operation back to awake / listening operation (EMLSR transition or inactive switching delay) may be different or equal.

[0198] For a non-AP MLD in EMLMR mode, the duration for switching from awake / listening operation to frame exchange operation (EMLMR active switching delay) and the duration for switching from frame exchange operation back to awake / listening operation (EMLMR transition or inactive switching delay) can be different or equal.

[0199] The non-AP MLD may determine a value of the EMLMR Delay subfield such that the value satisfies constraints related to both EMLMR Active Switch Delay and EMLMR Transition Delay (eg, EMLMR Delay may correspond to a maximum of minimum allowed values ​​of EMLMR Active Switch and EMLMR Transition Delay).

[0200] refer to Figure 2 An exemplary frame exchange sequence is shown to describe EMLMR operation according to an embodiment of the present invention.

[0201] Within a TXOP initiated by an AP-attached AP MLD with an EMLMR STA attached to a non-AP MLD as a TXOP responder, the non-AP MLD switches to its per-link spatial stream capability defined by the EHT Capability element or the latest OM (if present) after the EMLMR transition delay (e.g., "EMLMR Delay" or "EMLMR Delay + aSIFSTime + transmission time of the initial response frame" as described above) if any of the following conditions are met and this is defined as the end of the frame exchange sequence:

[0202] -The MAC of a STA affiliated with a non-AP MLD that receives the initial frame 245 does not receive a PHY-RXSTART.indication primitive during the timeout interval of aSIFSTime+aSlotTime+aRxPHYStartDelay, which timeout interval starts from the end of a PPDU (e.g., acknowledgment 256) transmitted by the STA affiliated with the non-AP MLD as a response to the most recently received frame (e.g., A-MPDU frame 255) from the AP affiliated with the AP MLD, or starts from the end of reception of a PPDU containing a frame that does not require immediate acknowledgment from the STA affiliated with the AP MLD.

[0203] - The MAC of the STA attached to the non-AP MLD that received the initial frame 245 receives the PHY-RXSTART.indication primitive during the timeout interval of aSIFSTime+aSlotTime+aRxPHYStartDelay, which timeout interval starts at the end of the PPDU (e.g., the ACK 256) transmitted by the STA attached to the non-AP MLD as a response to the most recently received frame (e.g., the A-MPDU frame 255) from the AP attached to the AP MLD, or starts at the end of reception of the following PPDU, which contains a frame that does not require immediate ACK from the STA attached to the AP MLD, and the STA attached to the non-AP MLD does not detect any of the following frames in the PPDU corresponding to the PHY-RXSTART.indication:

[0204] o Individually addressed frames where the RA is equal to the MAC address of the STA attached to the non-AP MLD;

[0205] o A trigger frame having one of the User Information fields addressed to a STA attached to a non-AP MLD;

[0206] ○CTS-to-self, where RA is equal to the MAC address of the AP attached to the AP MLD;

[0207] o Multi-STA Block Ack frame with one per-AID TID Information field addressed to the STAs attached to the non-AP MLD;

[0208] o NDP Announcement frame with one of the STA Information fields addressed to the STA attached to the non-AP MLD, and a Probe NDP;

[0209] - A STA attached to a non-AP MLD that receives the initial control frame 245 does not respond to the latest received frame (eg, A-MPDU frame 255) from an AP attached to an AP MLD that requires an immediate response after a SIFS.

[0210] In the above paragraphs, EMLMR STA refers to a non-AP STA attached to a non-AP MLD on an EMLMR link, and OM refers to an operation mode indication.

[0211] To meet the low latency requirements in EHT and to increase the efficiency of UL MU operation, existing mechanisms are reused and improved within the D2.0 standard, while other new mechanisms are added.

[0212] The Stream Classification Service (SCS) mechanism originally defined in the IEEE 802.11aa standard has been adapted for inclusion in the D2.0 standard. The SCS mechanism for multilink now allows non-AP MLDs to define and advertise (delay-sensitive) traffic flows identified with SCS identifiers (SCSIDs) to AP MLDs. The adaptation of the SCS mechanism allows QoS requirements to be defined for SCS flows through so-called QoS characteristic elements, in particular the classification of SCS flows into TID classes belonging to the corresponding uplink (UL) or downlink (DL) direction.

[0213] The target wake-up time (TWT) mechanism originally defined in the IEEE 802.11ah and 802.11ax standards has been adapted to be included in the D2.0 standard. The adaptation is known as restricted target wake-up time (rTWT), which schedules dedicated (and protected) service periods (SPs) for stations (affiliated to non-APMLDs) to transmit one or more of their delay-sensitive traffic (e.g., SCS flows) on the BSS of these stations. The rTWT agreement is nothing more than a broadcast TWT agreement negotiated between the AP and the associated non-AP stations of the BSS of a given link. Non-AP stations establish membership with the AP in a broadcast TWT (or rTWT) schedule. Scheduling can be defined for some TIDs (i.e., QoS characteristics specified by the SCS mechanism). The rTWT SPs of the rTWT schedule are advertised in broadcast management frames (e.g., beacons) using rTWT information about the negotiated rTWT service period (SP) (usually a broadcast TWT ID (bTWT ID)), where protected exchanges of SCS traffic flows can occur.

[0214] Although the SCS mechanism is negotiated between the initiator non-AP MLD and the AP MLD, there are still mechanisms such as TWT or rTWT, which are negotiated for each link, that is, negotiated between the initiator affiliated STA of the non-AP MLD and the corresponding affiliated AP of the AP MLD.

[0215] For a given link, non-AP stations establish membership in the AP's broadcast TWT schedule, and the AP delivers a set of broadcast TWT parameters to the non-AP stations. Non-AP stations are called TWT scheduled stations, and APs are called TWT scheduling stations.

[0216] Negotiation to become a member of or terminate membership in an rTWT schedule (more generally a broadcast TWT) is performed through the exchange of frames carrying TWT elements (with the negotiation type subfield set to 3 (broadcast TWT)) as shown below. In particular, a non-AP STA MLD can request to become a member of a TWT schedule by transmitting a TWT request frame to its associated AP MLD, which TWT request frame contains a TWT element for a given rTWT schedule.

[0217] The AP then advertises the scheduled broadcast TWT (or rTWT) using the broadcast TWT element in its management frames (typically in beacon frames, FILS discovery frames, and broadcast probe response frames).

[0218] Figure 3 A format of a TWT element 300 suitable for use in r-TWT according to the D2.0 standard is illustrated.

[0219] The TWT element 300 is identified by an element ID 301 and includes a "Control" field 310 and a field 320 for transmitting TWT parameter information.

[0220] The "Control" field 310 allows the TWT to be told whether it is a broadcast TWT or a separate TWT agreement through the "Negotiation Type" field 311. The MSB of the Negotiation Type subfield 311 is the broadcast field, so when the MSB of the subfield 311 is 1, the TWT element 300 is called a broadcast TWT element. The other fields are less important for this description.

[0221] If it is a single TWT (not shown), the "TWT parameter information" field 320 contains a single "Single TWT parameter set" field, and if it is a broadcast TWT (when the broadcast field of the "Negotiation Type" subfield is 1), the "TWT parameter information" field 320 contains one or more "Broadcast TWT parameter set" fields having the format 320a shown in the figure.

[0222] The first field in the Broadcast TWT Parameter Set field 320a is the Request Type field 330, which includes:

[0223] -TWT request subfield 331, when issued by a TWT scheduled STA, it is set to 1. Otherwise, it is set to 0 by the TWT scheduling STA (AP);

[0224] -TWT Set Command subfield 332, used to indicate the type of TWT command: when issued by a non-AP STA, the type of TWT command is request, suggestion, requirement, or rejection; or when issued by a TWT scheduling AP, the type of TWT command is accept, replace, specify, or reject;

[0225] - Trigger field 333, used to indicate whether the TWT SP indicated by the TWT element 300 includes a trigger frame (for trigger-enabled, for r-TWT, the Trigger subfield is equal to 1). Such a TWT SP is named a trigger-enabled TWT SP, and a non-AP station cannot start transmitting data in it without a previous trigger from the AP;

[0226] - A broadcast TWT recommendation field 336, which is set to 4 to indicate that the TWT described in the broadcast TWT element 300 is a restricted TWT (r-TWT). In this case, the broadcast TWT element 300 is also referred to as a restricted TWT element (r-TWT IE), and the broadcast TWT parameter set 320a is referred to as a restricted TWT parameter set.

[0227] - Other subfields are less important:

[0228] o The Last Broadcast Parameter Set subfield 334 is set to 0 to indicate that another Broadcast TWT parameter set follows this set.The Last Broadcast Parameter Set subfield is set to 1 to indicate that this is the last Broadcast TWT parameter set in the Broadcast TWT element.

[0229] ○ The stream type subfield 335 indicates whether the TWT is announced (the TWT scheduling AP will wait to receive a frame from the TWT scheduled STA to signal its awake state) or not announced (for the "announced" mode, for r-TWT, the stream type subfield is equal to 0, because r-TWT is a trigger-enabled TWT).

[0230] The other fields in the restricted TWT parameter set field 320a are used to define the time parameters of the rTWT schedule, as follows:

[0231] - The Target Wake-up Time (TWT) field 340 indicates the next time (in microseconds) that a station participating in the rTWT schedule should wake up in the next rTWT SP;

[0232] - The nominal minimum TWT wake-up duration field 350 indicates the minimum amount of time that a TWT scheduled STA is expected to be awake from the start time of the TWT SP to complete frame exchange in the period of the TWT wake-up interval. The TWT wake-up interval of the rTWT SP is a value calculated based on the TWT wake-up interval mantissa 360 and the TWT wake-up interval index 337. This field is expressed in a number of units (e.g., typically 256 μs) as defined in the wake-up duration units subfield 312 of the control field 310.

[0233] The other fields in the restricted TWT parameter set field 320a are used to define parameters specific to the broadcast and restricted nature of the rTWT SP:

[0234] -Broadcast TWT information field 370.

[0235] ○ This field conveys the identifier of the rTWT schedule (i.e., broadcast TWT ID 373 (bTWT ID)), which is used to identify the rTWT SPs belonging to the same rTWT schedule. Therefore, this identifier, which is not 0, allows the AP to schedule multiple broadcast TWT SP sets with different TWT parameter sets;

[0236] o This field specifies, via the Broadcast TWT Persistence subfield 374, the number of target beacon transmission times (TBTTs) for which there are broadcast TWT SPs corresponding to this restricted (more generally broadcast) set of TWT parameters;

[0237] o This field also signals the r-TWT scheduler AP via the RestrictedTWTScheduleAll subfield 372 (when set to 1) that it is unlikely to accept requests from STAs in the BSS to establish new membership in the corresponding schedule (identified by bTWT ID 373);

[0238] ○ Finally, this field also signals whether the restricted TWT traffic information field 380 exists through the restricted TWT traffic information existence field 371 (field 371 to 1).

[0239] - Restricted TWT Traffic Information field 380 specific to restricting broadcast TWT to specific traffic. This field is mandatory (hence field 371 is mandatory set to 1) when the broadcast TWT is associated with a SCSLL flow (otherwise, the traffic information is associated with a TID).

[0240] ○ This field includes a traffic information control field 381 indicating whether the following fields 382 and 383 are provided (i.e., "valid"). The DL TID bitmap valid subfield 3811 (correspondingly, the UL TID bitmap valid subfield 3812) indicates whether the restricted TWT DL TID bitmap field 382 (correspondingly, the restricted TWT UL TID bitmap field 383) has valid information.

[0241] ○ The restricted TWT DL TID bitmap field 382 (correspondingly, the restricted TWT UL TID bitmap field 383) identifies the TIDs of the latency-sensitive traffic in the DL (correspondingly, UL) direction, i.e., the TIDs allowed in the rTWT defined by the restricted TWT element 300. The TID can be the TID defining the SCS flow. A value of 1 at bit position k in the bitmap indicates that TID k is classified as a latency-sensitive traffic flow in the relevant transmission direction.

[0242] The TWT SP scheduled by the rTWT is uniquely identified by the <bTWT ID, MAC address of the TWT-scheduling AP> tuple, where the TWT-scheduling AP is the affiliated AP of the relevant link of the AP MLD.

[0243] Due to this element included in the TWT request frame, the initiating STA can request its AP to become an r-TWT scheduled STA by negotiating an r-TWT SP for its low-latency traffic. For example, the initiating STA (affiliated with a non-AP MLD) can negotiate a wake-up TWT, a wake-up interval, and the SCS flows allowed in the rTWT. The AP (the affiliated AP of the AP MLD on this link) provides a TWT response frame accepting or rejecting the request. In other words, the STA requests membership in the rTWT scheduling.

[0244] The TWT request frame carries a TWT element, where the negotiation type subfield 311 is set to 3, and the TWT setup command field 332 is set to request TWT, suggest TWT, or require TWT. The restricted TWT parameter set 320a indicates the broadcast TWT ID 373 of the rTWT scheduling that the STA is requesting to join. The AP may respond (with a TWT response frame) without a new rTWT scheduling for the bTWT ID (maintaining the existing rTWT scheduling), or provide an alternative parameter set for the parameters indicated in the TWT request frame, or create a new rTWT scheduling with a new bTWT ID.

[0245] Once negotiation and membership are completed, a regular TWT / rTWT scheduled STA in the awake state may enter the sleep state due to the advertisement of the rTWTSP (e.g., through the beacon frame) after receiving a beacon frame with a restricted TWT element indicating the presence of rTWT scheduling, and switch back to the awake state at the rTWT start time. The beacon frame indicates the rTWT SP during which the TWT scheduling AP intends to send a trigger frame to the TWT scheduled STA on that link or DL ​​BU.

[0246] At the beginning of each TWT / rTWT service period, and the TWT scheduled stations are expected to be in the awake state, the TWT scheduling AP typically uses OFDMA multi-user technology (e.g., MU UL triggered transmission, MU DL transmission) to manage the rTWT SP and may provide resource units to all or part of the TWT scheduled stations in the awake state.

[0247] Figure 4 A specific embodiment of the EMLSR mode of operation in a non-AP MLD 120 is illustrated using a frame sequence that has negotiated rTWT service with its AP MLD 110 on one of its EMLSR links (e.g., link 151). Of course, while the EMLSR mode is emphasized here by way of example, similar considerations can be made for the EMLMR mode.

[0248] At the beginning of the sequence, the non-AP MLD enters the EMLSR listening mode of operation, which means that its EMLSR co-affiliated STAs are set in the listening state of operation, so these STAs listen to their respective EMLSR links simultaneously. As a response to receiving an EML OM notification frame (in the EML Control field) with its EMLSR Mode subfield set to 1, the non-AP MLD may enter the EMLSR listening mode of operation. In a variant, the non-AP MLD may enter the EMLSR listening mode of operation by switching back from the EMLSR frame exchange mode.

[0249] like Figure 4 As shown in the case where the EMLSR-active non-AP MLD 120 is in the EMLSR listening operation mode, both EMLSR co-affiliated STAs A1 121 and A2 122 are in the listening operation states 410 and 411.

[0250] exist Figure 4 In the example of , the EMLSR co-affiliated STA A1 is selected as the station that has negotiated rTWT scheduling on link 151. This station may be a station with a full radio or a station with a light (reduced functionality) radio insignificantly.

[0251] The non-AP MLD 120 is able to listen on these links simultaneously by placing one or more of its EMLSR co-affiliated STAs corresponding to the EMLSR links in an "awake" or "listening operation" state. For example, the affiliated STAs A1, A2 are in the listening operation state (labeled 410 and 411). The listening operation includes CCA (clear channel assessment) and receiving the initial control frame of the frame exchange initiated by the AP MLD. In the non-AP MLD 120, the two EMLSR co-affiliated STAs therefore listen simultaneously to receive the initial control frame from the AP MLD as well as the beacon frame (this is because such a beacon frame is also transmitted in a low MCS and non-HT format).

[0252] By receiving the beacon frame 430 , the affiliated STA A1 is therefore able to determine the dedicated transmission window (rTWT) reserved for it on the link 151 .

[0253] Then, at the beginning of the reserved rTWT service period, the AP MLD 110 intends to initiate a frame exchange with one or more non-AP MLDs on one of the EMLSR links, and the AP MLD 110 starts the frame exchange by transmitting an initial control frame 445 that explicitly triggers the non-AP MLDs.

[0254] The EMLSR co-affiliated STA of the non-AP MLD that receives the initial control frame 445 explicitly triggered by the frame (e.g., affiliated STA A1 in the example) initiates a state change of the EMLSR co-affiliated STA of the non-AP MLD under consideration (e.g., a state change of affiliated STAs A1 and A2 in the example), and sends an initial control frame response (IC response) 446 to AP AP1 affiliated to AP MLD 110.

[0255] In case a response 446 is to be sent, after the EMLSR active switching delay 499a, the non-AP MLD 120 switches to the EMLSR frame exchange mode, wherein the EMLSR co-affiliated STA A1 121 switches from the listening operation state 410 to the enabled frame exchange state 420, while the EMLSR co-affiliated STA A2 122 simultaneously switches from the listening operation state 411 to the disabled frame exchange state 421.

[0256] The frames 455, 456 are then exchanged during the frame exchange sequence until the end of the sequence at which the non-AP MLD 120 switches back to the EMLSR listening mode of operation.

[0257] Typically, the subordinate AP1 111 may transmit a basic trigger frame 455 to the EMLSR co-subordinate STA A1 121 to allocate uplink resource units for the non-AP MLD 120. In this case, the non-AP MLD 120 transmits an EHT TB (extremely high throughput based on trigger) PPDU 456 in its allocated resource units via the EMLSR co-subordinate STA A1 121.

[0258] Once the frame exchange on link 151 is completed, the non-AP MLD 120 again invokes the state switching procedure to switch the EMLSR co-affiliated STAs A1 121 and A2 122 back to their listening operation states 410, 411. Thus, the non-AP MLD 120 switches back to the EMLSR listening operation mode. The switch back 499b is operational after the frame exchange within the service period is completed at the EMLSR transition delay (as specified in the EML capabilities).

[0259] In the case where the AP1 111 attached to the AP MLD 110 transmits an initial (control) frame that initiates a frame exchange with at least one non-AP MLD operating in the EMLSR mode and at least one non-AP MLD operating in the EMLMR mode, the AP ensures that the padding duration of the padding field of the initial control frame is greater than or equal to the maximum of the values ​​indicated in the EMLSR padding delay subfield and the EMLMR delay subfield of the basic multilink element received from the non-AP MLD initiating the frame exchange with it. From the perspective of each STA MLD 120, the transition period 499a fits within a delay generally referred to as the "EML active switching delay" from the perspective of the AP, which is composed of the maximum of the "EMLSR active switching" delay and the "EMLMR active switching" delay of the triggered station.

[0260] In other words, AP1 111 attached to AP MLD 110 transmits an initial frame that triggers frame exchange with at least one non-AP MLD operating in EML Single Radio (EMLSR) mode and at least one non-AP MLD operating in EML Multi Radio (EMLMR) mode. The AP MLD ensures that a padding duration of a padding field of the initial frame is greater than or equal to a maximum value of a value indicated in an EMLSR Padding Delay subfield received from at least one non-AP MLD operating in EMLSR mode and an EMLMR Delay subfield received from at least one non-AP MLD operating in EMLMR mode.

[0261] Figure 4The exemplary scenario of shows that the EML operation mode and TWT (e.g., rTWT) mechanism can theoretically work in combination. They will advantageously allow EML stations to transmit their delay-sensitive flows in a dedicated transmission window (rTWT) reserved for them. However, the resulting overall mechanism still has defects:

[0262] - The initial control frame 445 and corresponding response 446 that explicitly triggers non-AP MLD provides significant overhead within the critical resources dedicated to delay sensitive flows.

[0263] - In order to benefit from scheduled rTWT SP, EML STAs should know when the SP will occur: therefore, this forces EML STAs to also take care of beacon reception, which is not yet envisaged by the 802.11be standard.

[0264] Typically, the mechanisms or procedures operating for each link process, such as the exemplary target wake time (TWT) or its more recent adaptation known as restricted target wake time (rTWT), may not be fully adapted to the EML mode where EMLSR or EMLMR links are not fully independent of each other.

[0265] It has been sought to efficiently manage the EML mode of an EML non-AP MLD once a first affiliated STA of the EML non-AP MLD has negotiated a medium access service or mechanism on a first link of its EML links. When such a mechanism (link-specific process) is determined based on the first affiliated STA receiving a beacon frame on the first link, the first affiliated STA should not be in a blind mode during the reception of the beacon frame, and thus a second affiliated STA of the same EML non-AP MLD should not communicate on a second other link in the EML links during that period.

[0266] Typically, for a TWT schedule in which the initiating non-AP station (e.g., STA A1) has established membership with the AP (AP 111) of the BSS, the subordinate STA (A1) must be awake to receive the beacon frame indicating the TWT service period (on link 151) so that an early start of the upcoming service period in this rTWT schedule is available.

[0267] Although additional embodiments will be described with respect to TWT (rTWT), the present invention can be extended to other link-specific processes and should not be limited to the TWT mechanism. As an example, the silent element corresponding to the silent interval scheduled to protect the r-TWT SP is also a specific mechanism for each link (i.e., a link-specific process).

[0268] Figure 5 , Figure 6a , Figure 6b and Figure 6c Exemplary embodiments of the present invention are illustrated.

[0269] Figure 5 A flowchart is used to illustrate the steps performed by the EMLSR-active non-AP MLD to operate the TWT service (service period schedule acquisition and channel access process) according to an embodiment of the present invention. Figure 6a and Figure 6b Schematically illustrated as Figure 5 An exemplary timeline of TWT operations described in .

[0270] For ease of explanation, reference will be mainly made to the EMLSR mode only, but the same applies to the EMLMR mode.

[0271] The process starts at step 500, where the non-AP MLD enters the (EMLSR or EMLMR) listening mode of operation, which means that its co-affiliated STAs are set in the listening state of operation, so that these STAs listen to their respective (EMLSR or EMLMR) links simultaneously. The non-AP MLD may enter the listening mode of operation in response to receiving an EML OM notification frame whose corresponding mode subfield (EMLSR or EMLMR mode subfield in the EML control field) is set to 1. In a variation, the non-AP MLD may enter the listening mode of operation by switching back from the frame exchange mode.

[0272] In step 510, the non-AP MLD waits until it has buffered the delay-sensitive data to be transmitted to the AP MLD 110 (uplink). It is also possible to consider delay-sensitive data (triggered direct link data) transmitted to other non-AP MLDs over direct links under the control of the AP MLD 110. As described above, such data may be provided by upper layers and stored in the buffer 210 of the non-AP MLD. The non-AP MLD determines whether to transmit the delay-sensitive data to one of the EMLSR or EMLMR links (in the uplink). Figure 6a and Figure 6b In the example, link 151 is a selected link) on which TWT negotiation is activated.

[0273] In some embodiments, where TID-to-link mapping is negotiated between the AP MLD and the non-AP MLD to map some TIDs to a set of links and some other TIDs to another set of links, the buffered delay-sensitive data corresponds to one or more TIDs allowed to be transmitted on the selected links and is indicated in the bitmap 3811 and / or 3912 of the TWT element 320a in the rTWT format.

[0274] In response to the successful establishment of the TWT mechanism on the first link, a scheduling operation (same as step 550 described further) can be performed for the reception date of the next beacon frame (that is, for the next TBTT to occur).

[0275] Next, in a test step 520, various events allow the non-AP MLD to perform EML configuration itself, according to the embodiment. This can be the detection of a beacon frame on the link of interest (the selected link, such as 151), or a scheduled EML event according to the present invention (e.g., an EML event scheduled before the start of the TWT service period).

[0276] EML events related to the reception of a beacon frame (scheduled events before actual reception and / or the TBTT of the link) are processed through steps 530 to 550.

[0277] In fact, in this case, the non-AP MLD should not participate in frame exchanges on either of its EMLSR or EMLMR links.

[0278] Various configurations are possible for step 530:

[0279] - If there is no activity on any link, the state switching process is invoked by the non-AP MLD to continue its mode on the listening mode of operation, where the co-affiliated STAs are forced to maintain the listening mode until the end of the beacon frame reception (steps 531 and 532). In addition, these EML co-affiliated STAs should ignore any initial control frames addressed to them that overlap in time with the beacon frames transmitted on the selected link (TBTT on the intended link).

[0280] As an alternative embodiment, the selected co-affiliated STA (corresponding to the selected link (e.g., link 1 151) that intends to transmit a beacon frame) is switched (step 531) from the listening operation state to the enabled frame exchange state to enable frame exchange (even if only beacon frames are willing to be received), while in parallel (synchronously or simultaneously), the other co-affiliated STAs of the EMLSR or EMLMR link set (e.g., one of link 2) are switched (step 532) from the listening operation state to the disabled frame exchange state. This will easily avoid receiving any IC frames on one or more other links. This situation is caused by Figure 6c The subsequence "Case C" is used as an example.

[0281] - If there are frames exchanged on one or more other EML links, the co-affiliated STAs of the other links are requested to end their participation in the TXOP (Transmission Opportunity) and be in an EML mode compatible with the reception of beacon frames. This situation is addressed by Figure 6a Let's use the subsequence "Case A" as an example.

[0282] The non-AP MLD invokes a state switching procedure for each of the EMLSR or EMLMR co-affiliated STAs, causing these STAs to switch back to the EML listening state of operation. This will allow the co-affiliated STA1 121 to be able to receive the beacon frame 430 successfully.

[0283] - If there is a frame exchange on the selected EML link, the transmitting EMLSR co-affiliated STA (the selected link) remains in the frame exchange enabled state and waits for the medium to return to the idle state (the STA can end its existing TXOP, just like a legacy station does when it issues an approach at the TBTT time). The other EMLSR co-affiliated STAs also maintain their current state (disabled, step 532). This will continue for beacon frame reception. This situation is caused by Figure 6b The subsequence "Case B" is used as an example.

[0284] In other words, in step 530, the configuration of the selected co-affiliated STA or first affiliated station (corresponding to the selected link or first link (eg, link 1 151) intended to transmit a beacon frame) by the non-AP MLD 120 includes:

[0285] - Case A: ending the ongoing frame exchange on the second of the EML links and switching the first auxiliary station to an operational state compatible with receiving the second beacon frame (e.g., in a first variant, by switching the first auxiliary station to a listening operational state, in which case the second auxiliary station shall ignore any initial frames that trigger a frame exchange sequence on the second link and that overlap in time with the first beacon frame on the first link; and in a second variant, by switching the first auxiliary station to an enabled frame exchange state); or

[0286] - Case B: End the ongoing frame exchange on the first link and maintain the first auxiliary station in the frame exchange enabled state (for example, if the time distance to TBTT is less than a predetermined threshold, then maintain, wherein the predetermined threshold in a specific embodiment is at least the sum of the (first) transition period required for the non-AP MLD to switch the state of its auxiliary station from the listening operation state to the enabled or disabled frame exchange state and the (second) transition period required for the non-AP MLD to switch the state of its auxiliary station from the enabled or disabled frame exchange state to the listening operation state); or

[0287] - Case C: Switching the first secondary station from the listening operation state to the frame exchange enabled state.

[0288] As a result, in step 540, the selected EMLSR co-affiliated STA may receive the beacon frame and analyze its content.

[0289] As an example of content of interest for this embodiment, the TWT information element 300 may be analyzed to confirm the scheduling of the TWT service period (eg, wake-up TWT and wake-up interval via fields 340, 360, 337).

[0290] In order to silence the STAs during the r-TWT service period, the r-TWT scheduling AP may schedule a silent interval that overlaps with the r-TWTSP for a given link. Overlapping silent intervals may be scheduled by including one or more silent elements in the beacon frame. The silent element is thus another example of what is of interest to this embodiment: that is, the non-AP MLD should not participate in transmissions during any silent interval. Even more, the non-AP MLD therefore determines that one of its co-affiliated STAs should be silent during the silent interval corresponding to the r-TWT service period of which it is not a member.

[0291] Next (step 550), the non-AP MLD may schedule one or more EML events in response to the mechanism determined by the beacon frame.

[0292] First, the non-AP MLD schedules itself to be awake for the next TBTT on the selected link.

[0293] In other words, at the next TBTT occurrence (considering that the current TBTT occurrence is associated with the first beacon frame), the test step 520 will be performed again and will indicate the detection of the EML event associated with the next (second) beacon frame, so steps 530 to 550 will be performed again. Therefore, the non-AP MLD performs a communication method, which includes:

[0294] - receiving, by a first auxiliary station (eg, STAA1) on a first link (eg, 151) of the EML links, a first beacon frame including a target beacon transmission time (TBTT) associated with a second beacon frame; and

[0295] -Configuring the first auxiliary station (eg, STA A1) to be in a receiving state at TBTT to receive the second beacon frame.

[0296] As an option, after associating with the AP MLD, the non-AP MLD may be considered to schedule its events for TBTT timing on all EML links: this is to be able to determine link-specific procedures for all its EML links (e.g., silent elements of TWTs of which the non-AP MLD is not a member). When link-specific procedures have been negotiated in step 510, the non-AP MLD may schedule itself for beacon frames on the selected link for initial discovery of TWT / rTWT elements indicating the service period of the TWT service it has negotiated.

[0297] Regarding further beacon TBTT scheduling, related to TWT operation, the non-AP MLD can relax the constraints on the individual TBTTs for the selected link: the indication of the broadcast TWT persistence subfield 374 can allow determining the number of target beacon transmission times (TBTTs) for the broadcast TWT SP corresponding to this restricted (more generally, broadcast) TWT parameter set, so that the intermediate TBTTs can be ignored (only the beacon frame of the last TBTT of the persistent information can contain new information).

[0298] In other words, in the above context where the non-AP MLD configures the first auxiliary station (e.g., STA A1) to be in a receive state at a TBTT to receive a second beacon frame, the second beacon frame includes another TBTT related to a third beacon frame that schedules a TWT service period on the first link, and in the case where the scheduled TWT service period is signaled with TWT persistence, frame exchange by the second auxiliary station continues on the second link in the EML link without configuring the first auxiliary station to be in a receive state at another TBTT to receive the third beacon frame on the first link.

[0299] If it will Figures 6a to 6c As becomes apparent above, scheduled events are preferably prior to the emission date (of a beacon frame or TWT period), such as "EML active switching delay" 499 / 499a being optional.

[0300] This is because the simultaneous switching lasts at most the EMLSR or EMLMR active switching delay as previously specified and shown by reference numeral 499 / 499a in the figure. In this example, EMLSR co-affiliated STA A1 is selected. It can be a station with a full radio or with a light (reduced functionality) radio indifferently. In practice, (due to the physics and reconfiguration required for the full radio link) the switching for an EMLSR co-affiliated STA with a full radio (requiring only an antenna connection) is shorter than the switching for another EMLSR co-affiliated STA with a light radio, so the non-AP MLD is able to adapt its scheduling to take into account the appropriate timing 499 / 499a regarding its hardware configuration (e.g., reducing the scheduling margin for the link configured with the full radio).

[0301] Furthermore, the non-AP MLD can also adapt its scheduling to take into account current activity before the event of interest: a timing margin can be envisaged to stop any existing TXOP before the switching delay 499 / 499a ( Figure 6a and Figure 6b ).

[0302] In practice, the scheduling operation is performed by the non-AP MLD at its upper MAC 230. This is because this entity collects management frame information from all links and can configure the lower MAC entities 220-x / 220-y / 220-z accordingly. Since the upper MAC can be responsible for frame decoding, the TBTT of all links can be obtained, so it seems preferable that the U-MAC 230 controls the activities of the L-MAC (e.g., temporarily deactivating activities on the medium, or forcing a "listening" mode).

[0303] It is also possible to first inform LL-MAC to stop its TXOP activity, and then inform EML to configure the switch, such as according to Figure 5 as described.

[0304] Once the beacon frame reception on link 1 is completed, the non-AP MLD invokes the state switching procedure again to switch its co-affiliated STAs back to their listening operation state (step 590). Thus, the non-AP MLD switches back to the listening operation mode. After the frame exchange is completed, it is operational to switch back to the EMLSR transition delay (as specified in the EML capabilities) or the EMLMR transition delay (as specified above, according to an embodiment of the present invention).

[0305] Returning to test 520, the EML event scheduled by step 550 is processed through steps 560 to 580 with respect to the link-specific mechanism.

[0306] The purpose of step 560 is to configure the non-AP MLD to be in the appropriate state on the link of interest. Therefore, the state switching process is invoked for each EML co-affiliated STA, and accordingly:

[0307] -When the scheduled EML event involves a (r-)TWT service period, the non-AP MLD is intended to be active for the link at the location and time when the (r-)TWT period will begin. Therefore, the "first" link of step 561 is the link corresponding to the selected co-affiliated STA.

[0308] STAs attached to non-AP MLD on the corresponding link (i.e., Figure 6a and Figure 6b The receiving EMLSR co-affiliated STA A1 in the example is configured to be able to transmit or receive frames on the enabled link during the TWT service period (step 561). As further becomes apparent, the EMLSR co-affiliated STA A1 does not need to receive the initial control frame for frame exchange, thus saving resources in the TWT SP.

[0309] At the same time, other EMLSRs of the same non-AP MLD are co-attached to STAs (i.e., Figure 6a and Figure 6bIn the example of STA A2, it is configured to transmit or receive on one or more other EMLSR links until the end of the TWT period. To this end, the state switching process is also called for other EMLSR co-affiliated STAs, which in turn switch from the listening operation to the "blind frame" or "disabled frame exchange" state (step 562).

[0310] - When a scheduled EML event involves a silent element of a (r-)TWT service period, the non-AP MLD is intended to be disabled for that link at the location and time when the silent period will start.

[0311] To this end, the selected EMLSR co-affiliated STA of the same non-AP MLD (i.e., STA A1 belonging to the link that sends the beacon frame in the example) is configured not to transmit or receive until the frame exchange is completed (step 562). The other EMLSR co-affiliated STAs of the same non-AP MLD can be switched to the listening operation state (if even possible by hardware, as a complement to the disabled one link), or alternatively, at most one of the other EMLSR co-affiliated STAs of the same non-AP MLD (i.e., STA A2 in the example) is switched from the listening operation state to the "active frame exchange" or "enable frame exchange" state (step 561).

[0312] In other words, in the above context where the non-AP MLD configures the first subsidiary station (e.g., STA A1) to be in a receiving state at TBTT to receive the second beacon frame, the second beacon frame schedules a silent period on the first link, and during the silent period, the first subsidiary station is switched to a disabled frame exchange state until the silent period ends. In addition, during the silent period, the non-AP MLD switches the second subsidiary station to an enabled frame exchange state on the second link in the EML link until the silent period ends.

[0313] As already discussed, for the efficiency of the configuration of the appropriate date, the "EML activity switching delay" is preferably taken into account.

[0314] The state switching of all EMLSRs commonly affiliated STAs in the same non-AP MLD is inseparable and therefore simultaneous, because this is the whole radio resource chain (see below). Figure 9a ) is allocated to one of the STAs while the other STAs are deprived of such a chain. Regarding the EMLMR mode, the physical resources (e.g., antennas) of one radio resource chain are allocated (and aggregated) to another radio resource chain, so the former is deprived of transmission / reception capabilities (see below Figure 9a ).

[0315] The above shows that when the non-AP MLD operates in EMLSR mode (and more generally, in either of the EMLSR and EMLMR modes), it is in a listening operation mode (its co-affiliated STAs are in a listening operation state) or in a frame exchange mode (one of its co-affiliated STAs is in an enabled frame exchange state and the other co-affiliated STAs are in a disabled frame exchange state).

[0316] After the configuration of step 560, step 570 (where Figure 6a and Figure 6b The receiving EMLSR co-affiliated STA A1 in the example operates frame exchange on the enabling link (first link) during the TWT service period) until step 580 (end of service period). The duration is obtained from the TWT IE or silence element.

[0317] For TWT, the nominal minimum TWT wake-up duration field 350 indicates the minimum amount of time that a TWT scheduled STA is expected to be awake from the start time of the TWT SP to complete frame exchange in the period of the TWT wake-up interval. Therefore, switching back is operational after the end of the service period, rather than after the end of the internal frame exchange, in the EMLSR transition delay (as specified in the EML capabilities). This also provides more space inside the TWT SP for delay-sensitive data transmission.

[0318] An exemplary frame exchange sequence is shown in the following figure.

[0319] Figure 6a and Figure 6b An enhanced frame exchange sequence for supporting TWT mechanism by EMLSR stations according to the present invention is presented. For ease of description of the figure, reference is mainly made to EMLSR mode only, while the same applies to EMLMR mode.

[0320] In the example, the EMLSR co-affiliated STA1 121 is selected as the station interested in the per-link procedure. This station can be a station with a full radio or with a light (reduced functionality) radio indifferently.

[0321] The simultaneous switching lasts at most the EMLSR active switching delay as previously specified and shown by reference numerals 499a / 499b in the figure. In practice, (due to the physical and reconfiguration of the required full radio chain) the switching for an EMLSR co-affiliated STA with a full radio (requiring only antenna connection) is shorter than the switching for other EMLSR co-affiliated STAs with a light radio. Therefore, the values ​​considered for 499a / 499b can correspond to the radio configuration of STA A1 (or to the respective maximum values, respectively).

[0322] like Figure 6aAs shown in the case of EMLSR-active non-AP MLD 120, both of the EMLSR co-affiliated STA A1 121 and STA A2 122 have switched from listening operation to (in the past, not shown) a “blind frame” or “disabled frame exchange” state 610 for STA1 121, and correspondingly to an “active frame exchange” or “enabled frame exchange” state 611 for STA2 122.

[0323] As previously described with respect to step 530, both the end of STA A2's TXOP participation and the switching of the last period 499b are considered here with respect to the termination phases 610 and 611. The end of the TXOP can be done in several ways, even by shortening its data communication or not responding to the peer device (AP of Link 2), or even by sending a CF end frame if STA A2 is the TXOP holder.

[0324] As a result, when a non-AP STA attached to a non-AP MLD and operating on one of a pair of EMLSR links or EMLMR links intends to receive a broadcast management frame (beacon frame 430) on a first link (151); if a second non-AP STA (STA A2) attached to the same MLD participates in a frame exchange on a second link (152) that overlaps the TBTT of the first link, the second non-AP STA (STA A2) and its associated AP (referred to as a second AP) should follow the following rules:

[0325] - the second AP as the TXOP holder on the second link (152) shall ensure that its TXOP ends no later than T amount of time earlier than the TBTT on the first link,

[0326] - The second non-AP STA (STA A2) as the TXOP holder on the second link (152) should ensure that its TXOP ends no later than T amount of time earlier than the TBTT on the first link.

[0327] In an embodiment, T is equal to one of the following values:

[0328] - EMLSR Transition Delay (499b), which is indicated in the EMLSR Transition Delay subfield specified for a pair of EMLSR links if the two non-AP STAs belong to the pair of EMLSR links,

[0329] - EMLMR Delay, which is indicated in the EMLMR Delay subfield specified for a pair of EMLMR links if two non-AP STAs belong to the pair (ie, EMLMR Deactivation Switching Delay as specified previously, depending on the implementation).

[0330] When several non-AP STAs are operating in a TXOP in the second link (152), then the second AP as the TXOP holder on the second link (152) should ensure that T is greater than or equal to the maximum individual T value of these non-AP STAs (as determined previously herein).

[0331] In other embodiments, T is equal to one of the following values:

[0332] - EMLSR Transition Delay (499b), which is indicated in the EMLSR Transition Delay subfield specified for a pair of EMLSR links if two non-AP STAs belong to the pair of EMLSR links;

[0333] -MLMR Delay + aSIFSTime + transmission time of the initial response frame (in the case where two non-AP STAs belong to a pair of EMLMR links) (ie, depending on the implementation, EMLMR Deactivation Switching Delay as specified before).

[0334] The duration of the initial response frame may vary depending on the initial frame. The non-AP MLD and AP MLD may determine the duration when the shortest initial response frame is used on the EMLMR link (eg, the CTS frame in the non-HT PPDU with the highest rate in the BSSBasicRateSet parameter).

[0335] When several non-AP STAs are operating in a TXOP in the second link (152), then the second AP as the TXOP holder on the second link (152) should ensure that T is greater than or equal to the maximum individual T value for these non-AP STAs (as determined previously herein).

[0336] The simultaneous switching (eg, putting all co-affiliated STAs into "listen" mode) lasts at most as long as the EMLSR Active Switching Delay or the EMLMR Active Switching Delay specified previously.

[0337] In other words, configuration of the selected co-affiliated STA or first affiliated station (STA A1) (corresponding to the selected link or first link (e.g., link 1 151) intended to transmit a beacon frame) is triggered by at least a first determined delay (e.g., EMLSR active switching delay, EMLMR active switching delay, or a maximum of EMLSR and EMLMR active switching delays) before TBTT by the non-AP MLD 120.

[0338] This will make it possible to receive a beacon frame (by STA A1) on Link 1. Furthermore, one or more other EML co-affiliated STAs (here STA A2) should ignore any Initial Control Frames (if any) addressed to them that overlap in time with a Beacon Frame of the selected link (TBTT on the intended link).

[0339] This mode may also be advantageous to receive beacon frames on both EML links (if synchronized in time).

[0340] Once the beacon frame has been received, all EML co-affiliated STAs may proceed with their normal operations.

[0341] Next, the reservation period will reach a date (630).

[0342] and Figure 4 In contrast, the EML scheduler has envisioned scheduling a switch in the “active frame exchange” or “enabled frame exchange” state of STA1 before starting the intended TWT SP 630. Typically, a switch delay 499 / 499a (belonging to the group consisting of: EMLSR active switch delay, EMLMR active switch delay, and the maximum of EMLSR and EMLMR active switch delays) occurs before the TWT SP 630.

[0343] In the same manner as case A but applied to the TWT SP 630, any media activity on the EML link will cease (not shown).

[0344] As a result, when a non-AP STA affiliated with a non-AP MLD and operating on one of a pair of EMLSR links or EMLMR links is a member of an R-TWT SP on a first link (151); if a second non-AP STA (STAA2) affiliated with the same MLD is not a member of any other R-TWT SP overlapping with the first SP on a second link (152), the second non-AP STA (STAA2) and its associated AP (referred to as a second AP) should follow the following rules:

[0345] - The second AP, being the TXOP holder on the second link (152), shall ensure that its TXOP ends no later than T amount of time earlier than the start time of the R-TWT SP on the first link;

[0346] - The second non-AP STA (STA A2) as the TXOP holder on the second link (152) should ensure that its TXOP ends no later than T amount of time earlier than the start time of the R-TWT SP (630) on the first link.

[0347] In an embodiment, T is equal to one of the following values:

[0348] - EMLSR Transition Delay (499b), which is indicated in the EMLSR Transition Delay subfield specified for a pair of EMLSR links if the two non-AP STAs belong to the pair of EMLSR links,

[0349] - EMLMR Delay, which is indicated in the EMLMR Delay subfield specified for a pair of EMLMR links if two non-AP STAs belong to the pair (ie, EMLMR Deactivation Switching Delay as specified previously, depending on the implementation).

[0350] When several non-AP STAs are members of the R-TWT SP on the first link (151) and operate in a TXOP in the second link (152), the second AP as the TXOP holder on the second link (152) should ensure that T is greater than or equal to the maximum individual T value of these member non-AP STAs (as previously determined herein).

[0351] In other embodiments, T is equal to one of the following values:

[0352] - EMLSR Transition Delay (499b), which is indicated in the EMLSR Transition Delay subfield specified for a pair of EMLSR links if the two non-AP STAs belong to the pair of EMLSR links,

[0353] -EMLMR Delay + aSIFSTime + transmission time of the initial response frame (in the case where two non-AP STAs belong to a pair of EMLMR links) (ie, depending on the implementation, EMLMR Deactivation Switching Delay as specified previously).

[0354] The duration of the initial response frame may vary depending on the initial frame. The non-AP MLD and AP MLD may determine the duration when the shortest initial response frame is used on the EMLMR link (eg, the CTS frame in the non-HT PPDU with the highest rate in the BSSBasicRateSet parameter).

[0355] When several non-AP STAs are members of the R-TWT SP on the first link (151) and operate in a TXOP in the second link (152), the second AP as the TXOP holder on the second link (152) should ensure that T is greater than or equal to the maximum individual T value of these member non-AP STAs (as previously determined herein).

[0356] Since the initial (control) frame 445 and corresponding response 446 used to explicitly trigger the non-AP MLD provide significant overhead within the critical TWT SP resources dedicated to delay-sensitive flows, and since the TWT SP has been determined, the non-AP MLD can configure its subordinate EML STAs to be ready to operate during the TWT SP 630.

[0357] When the non-AP MLD 120 expects to initiate a frame exchange sequence with the AP MLD 110 during the TWT SP 630 (EMLSR co-affiliated STA A1 121 is selected as the EMLSR co-affiliated STA transmitting in the negotiated TWT), the non-AP MLD 120 switches the EMLSR co-affiliated STA A1 121 from the listening operation state 410 to the enabled frame exchange state 620, and in parallel (synchronously or simultaneously), switches the EMLSR co-affiliated STA A2 122 from the listening operation state 411 to the disabled frame exchange state 621.

[0358] The listening operational state is restored and operational after the TWT SP 630 ends, corresponding to the switch back (a period 499b defined by the EMLSR transition delay set in the EML capability).

[0359] In other words, in the above context where the non-AP MLD configures the first auxiliary station (e.g., STA A1) to be in a receiving state at TBTT to receive a second beacon frame, the second beacon frame schedules a service period on the first link, and when frame exchange ends within the service period, the non-AP MLD maintains the first auxiliary station in an enabled frame exchange state until the service period ends. In a specific embodiment, the non-AP MLD switches the first auxiliary station in an enabled frame exchange state before the service period starts, and maintains the first auxiliary station in an enabled frame exchange state until the service period ends. In addition, at the end of the service period, the non-AP MLD switches the first auxiliary station from the enabled frame exchange state to a listening operation state.

[0360] The EMLSR co-affiliated STA switches back to the listening mode of operation, independent of the duration field (Basic Trigger 455) in the frame that triggered it (or more generally, after the end of the frame exchange with its AP), but rather for the entire service period 630. This will support several frame exchanges (if any) with the AP during the service period 630 without the overhead due to an additional initial (control) frame / response EML enablement sequence.

[0361] Figure 6b Presented with Figure 6a12, wherein EMLSR co-affiliated STAs A1 121 and A2 122 start in an "active frame exchange" or "enabled frame exchange" state 611 for STA 1 121 and in a "blind frame" or "disabled frame exchange" state 610 for STA 2 122, respectively.

[0362] Only the sequence of emphasis in "Case B" is different.

[0363] STA1 121 is already operating on the EMLSR link 151 for frame exchange with the AP MLD.

[0364] Typically, according to 802.11be D0.5, when a STA of a non-AP MLD initiates a TXOP, the non-AP MLD should switch back to listening operation on the EMLSR link after the end of the TXOP for the duration indicated in the EMLSR Transition Delay subfield (499b).

[0365] This rule is suitable for the current situation, where the TBTT is immediately adjacent to the TXOP. As already discussed, the TXOP on link 151 can be shortened to respect the TBTT time on that link.

[0366] An embodiment provides that the non-AP MLD maintains the current EML configuration until a beacon frame is received: the co-affiliated STA A1 remains in the enabled frame exchange state 620a to be able to receive beacon frames, and the co-affiliated STA A2 remains in the disabled frame exchange state 621a (this will avoid any changed EML mode due to the receipt of an initiation frame during this period).

[0367] For different behaviors, the non-AP MLD first determines the duration remaining time at TBTT, and based on this time decides whether to switch back to the listening operation mode or remain in the current EMLSR frame exchange mode. For example, if the time is long, that is, its value is higher than the threshold, the EMLSR co-affiliated STA is switched back to the listening operation mode (thus resulting in the following Figure 6c And if the duration is short, ie its value is lower than the threshold, the EMLSR co-affiliated STA remains in its current state.

[0368] Figure 6c First, an enhanced frame exchange sequence with respect to support of beacon frames by EML stations according to an embodiment is presented ("Case C").

[0369] The embodiment provides that the non-AP MLD switches only one EMLSR co-affiliated STA to an active state (ie, switches to a frame exchange enabled state for the selected EMLSR co-affiliated STA and switches to a transmission disabled EMLSR co-affiliated STA for the other EMLSR co-affiliated STAs).

[0370] In the figure, a co-affiliated STA (corresponding to the selected link (e.g., link 1 151) intending a beacon frame) switches from the listening operation state to the enabled frame exchange state 660 to enable frame exchange (even if only willing to receive beacon frames), while in parallel (synchronously or simultaneously), other co-affiliated STAs in the EMLSR link set or the EMLMR link set (e.g., one of link 2) switch from the listening operation state 411 to the disabled frame exchange state 661.

[0371] Figure 6c An enhanced frame exchange sequence ("Case D") regarding EML station support of silent periods for the rTWT mechanism according to the present invention is also presented.

[0372] This corresponds to applying step 561 for a scheduled silent period event. In an embodiment, this may correspond to a silent period that includes a (r-)TWT service period of which the EML station is not a member.

[0373] In this context, activity on the first link (the silent period on which beacons are received and indicating TWT) is prohibited. Therefore, another EML link can be used to be active during this period.

[0374] Thereafter, according to the EMLSR mechanism, after the EMLSR active switching delay 499, the non-AP STA is scheduled to switch from the EMLSR listening operation mode to the EMLSR frame exchange mode in order to make one of the EMLSR co-affiliated STAs operable for frame exchange in a link other than the disabled first link. The EMLSR co-affiliated STAs including the first link 151 for which STA A1 has received a beacon frame are disabled.

[0375] In the example, the EMLSR co-subordinate STA A2 switches from the listening operation state 411 to the enabled frame exchange state 651 , while in parallel (synchronously or simultaneously) the transmitting EMLSR co-subordinate STA A1 switches from the listening operation state 410 to the disabled frame exchange state 650 .

[0376] Figure 7 and Figure 8 The steps performed by an EMLSR-active non-AP MLD to set up a TWT service are illustrated using a flow chart. Basically, step 510 is detailed to determine one or more EML co-affiliated STAs that are allowed to negotiate a link service.

[0377] Figure 7 Guidance is provided when TWT services have been set up before EML operations are to be activated.

[0378] As an example, the non-AP MLD has one TWT service established on link 151 for the co-affiliated STA A1 (step 710).

[0379] Step 720 corresponds to step 500, where the non-AP MLD intends to operate in the EMLSR / EMLMR mode, which means that the EML operation mode notification frame activating the EMLSR / EMLMR mode is successfully transmitted to the non-AP MLD 120 (indicating the attached STAs A1 and A2).

[0380] According to an embodiment, step 730 is intended to indicate to the AP that one of the EML links must be monitored for both EML operation and per-link mechanisms (e.g., similar to TWT). The purpose of this indication is to enable the AP to avoid link conflicts for the monitored events. In an embodiment, since the AP MLD controls TWT and beacon scheduling on all its active links, the MLD AP is warned to avoid scheduling TWT SPs for EMLSR STAs that overlap with beacons on other EMLSR links. In other words, the non-AP MLD transmits to the APMLD an indication of a service period for scheduling the non-AP MLD (on the first link) in a future beacon frame, which service period does not overlap in time with any beacon frame transmitted by the AP MLD on the second link in the EML link. This indication ensures that the non-AP MLD will be able to receive beacon frames on the second link 152, regardless of the service period scheduled on the first link 151.

[0381] As an exemplary support for such an indication, bit B15 (338) of the TWT request subfield 331 of the TWT element 300. Thus, the "EML" field 338 may indicate whether the TWT SP indicated by the TWT element 300 is operating on a link that enables EML operation, and the non-AP MLD organizer of the TWT element requests the help of the AP to avoid EML link conflicts. (Requesting the AP to avoid scheduling r-TWT SPs for EML STAs that overlap with beacons on other EML links).

[0382] Figure 8 The steps performed by non-AP MLDs to limit the use of TWT services to a given number of links are briefly described. Even if it is possible to manage more links, it may appear complex and inefficient (due to excessive switching of EML active / pause periods).

[0383] In step 810, the EML non-AP MLD is already operating in EML (EMLSR or EMLMR) mode. The non-AP MLD receives an internal request (e.g., from a local application on the MAC) to open a new TWT service. By increasing the number of links that schedule EML events (step 550), this can regularly force the EML operation mode according to the previous embodiments (cases A to C in the previous figures). Therefore, the non-AP MLD can be requested to suspend the existing TXOP more frequently. This may also be frequent when the TBTT interval of the link is short.

[0384] If the number of links is greater than the expected number, the non-AP MLD may reject any new (r)TWTs for the other links. The algorithm will stop. Otherwise, the non-AP MLD may shut down one or more existing rTWT services on the first link (step 820) and reinstall one or more existing rTWT services on the second link in addition to the new incoming TWT service (step 830). Figures 6a to 6c For example, this would mean that all TWT services would be arranged on a single link (e.g. link 151).

[0385] In summary, the above embodiment stipulates that if a STA attached to a non-AP MLD intends to receive a beacon frame scheduled at TBTT on one (the first) of its EML (EMLSR or EMLMR) links, the non-AP MLD should be able to listen on the EML (EMLSR or EMLMR) link. Therefore, the following rules should be met:

[0386] - If another STA attached to the same non-AP MLD successfully obtains a TXOP on another link in the EML (EMLSR or EMLMR) links, the STA shall end its TXOP before the TBTT of the (first) link; (see Figure 6a , Case A)

[0387] - If the same STA attached to the same non-AP MLD is part of a TXOP on the intended (first) link in an EML (EMLSR or EMLMR) link, then the STA may remain awake on that link until the TBTT; (see Figure 6b , Case B)

[0388] - Any STA attached to the same non-AP MLD that is listening on an EML (EMLSR or EMLMR) link should ignore any Initial Control Frames addressed to it that overlap with a TBTT on the intended (first) link (i.e., overlap in time with a Beacon Frame transmitted with a TBTT on the first link).

[0389] Receiving a beacon frame on an EML (EMLSR or EMLMR) link is satisfied if one of the following conditions is met:

[0390] -Establish a TWT or rTWT protocol over the EMLSR link.

[0391] -Silence elements corresponding to silence intervals are scheduled to protect r-TWT SPs.

[0392] Fig. 9 The architecture of the EMLSR capability for MLD is schematically illustrated. The figure takes an example of two affiliated non-AP STAs sharing the hardware resources of their non-AP MLD when the EMLSR mode is activated. The EMLSR capability architecture for MLD presented in this figure is for illustration purposes only, and other alternative architectures can be envisioned.

[0393] The architecture includes two radio stacks, a light radio stack and a full radio stack.

[0394] The full radio stack includes a full 802.11be MAC module 900a (exchanging data with higher layers), a full 802.11be PHY module 905a connected to the full MAC module, a full RF chain 915a connected to the full PHY module, and an antenna 920a connected to the full RF chain through an EMLSR switch 910.

[0395] The light radio stack includes a light 802.11be MAC module 900b (exchanging data with higher layers), a light 802.11be PHY module 905b connected to the light MAC module, a light RF chain 915b connected to the light PHY module, and an antenna 920b connected to the light RF chain through an EMLSR switch 910.

[0396] The EMLSR switch 910 is shared by both radio stacks and is configured to switch the EMLSR co-affiliated STAs from a listening operation state to an enabling or disabling frame exchange state / from an enabling or disabling frame exchange state to a listening operation state when the EMLSR mode is activated.

[0397] Radio chain 900a / 905a / 915a is a full radio resource that allows reception and transmission of any IEEE802.11 frame. In particular, radio chain 900a / 905a / 915a includes a coding and decoding module that encodes and decodes any IEEE802.11 frame. On the other hand, radio chain 900b / 905b / 915b is a reduced-function (or "light") radio resource that only allows reception and transmission of specific IEEE802.11 frames. In particular, radio chain 900b / 905b / 915b only includes a coding and decoding module that encodes and decodes specific frames using a rate of 6Mbps, 12Mbps, or 24Mbps.

[0398] The lower left figure illustrates the function of the MLD when the non-AP MLD is in the EMLMR listening mode of operation: the common EMLSR switch 910 connects the individual radio chains 900a / 905a / 915a and 900b / 905b / 915b to antennas 920a and 920b, respectively. Therefore, the individual radio stacks can be used to listen to the corresponding links simultaneously. As shown, two links are available. The full radio chain 900a / 905a / 915a and antenna 920a are configured to operate on link 1, and the light radio chain 900b / 905b / 915b and antenna 920b are configured to operate on link 2.

[0399] The bottom center diagram illustrates the function of MLD when non-AP MLD switches to the first EMLSR frame exchange mode. The EMLSR common affiliated STA corresponding to link 1 is in the enabled frame exchange state, and the other EMLSR common affiliated STA corresponding to link 2 is in the disabled frame exchange state. In this case, the common EMLSR switch 910 connects the full radio chain 900a / 905a / 915a to both antennas 920a and 920b, and the full radio chain 900a / 905a / 915a and antennas 920a / 920b are configured to operate on link 1. Here, since the full radio chain reservation is configured to operate on link 1, the EMLSR switching duration from the listening operation state to the enabled frame exchange state can be considered to be short. In fact, in this case, the switch only involves antenna switching. On the other hand, the common EMLSR switch 910 disconnects the light radio chain 900b / 905b / 915b from the antenna 920b. In this configuration, the light radio chain 900b / 905b / 915b cannot receive or transmit any frames on link 2. Then, only link 1 is available.

[0400] The figure at the lower right illustrates the function of MLD when non-AP MLD switches to the second EMLSR frame exchange mode. The EMLSR common subsidiary STA corresponding to link 2 is in the enabled frame exchange state, and the other EMLSR common subsidiary STA corresponding to link 1 is in the disabled frame exchange state. In this case, the common EMLSR switch 910 connects the full radio chain 900a / 905a / 915a to both antennas 920a and 920b, and the full radio chain 900a / 905a / 915a and antenna 920a / 920b are configured to operate on link 2. Here, since the full radio chain is switched to operate on link 2, the EMLSR switching duration from the listening operation state to the enabled frame exchange state can be considered to be long. In fact, in this case, the switching involves both antenna switching and full radio chain configuration switching. On the other hand, the common EMLSR switch 910 disconnects the light radio chain 900b / 905b / 915b from the antenna 920b. In this configuration, the light radio chain 900b / 905b / 915b cannot receive or transmit any frames on link 1. Then, only link 2 is available.

[0401] The functionality of the common EMLSR switch 910 clearly shows that the state changes of two EMLSR common affiliated STAs in the same MLD are necessarily simultaneous, since the radio chain connects to either one of the STAs or to the other, but never remains available to both STAs at the same time.

[0402] Figure 9a The EMLMR capability architecture for MLD is schematically illustrated. The figure takes an example where two affiliated non-AP STAs share their antenna resources when the EMLMR mode is activated.

[0403] The architecture includes two radio stacks, one for each non-AP STA.

[0404] The radio stack includes a full 802.11be MAC module 900a' or 900b' (exchanging data with higher layers), a full 802.11be PHY module 905a' or 905b' connected to the MAC module, a radio frequency chain 915a' or 915b' connected to the PHY module, an EMLMR switch 910' shared by the two radio stacks and configured to aggregate antenna resources when the EMLMR mode is activated, and an antenna array 920a' or 920b'.

[0405] The lower left diagram illustrates the functionality when a non-AP MLD is listening to an initial frame: a common EMLMR switch 910' connects each antenna array to its RF chain. Thus, each radio stack is complete and can serve the corresponding link using, for example, a 2x2 MIMO antenna configuration. As shown, two links are available.

[0406] The bottom center figure illustrates the functionality of the MLD when the non-AP MLD switches to the first EMLMR frame exchange mode. The EMLMR co-affiliated STA corresponding to link 2 is in an enabled frame exchange state, while the other EMLMR co-affiliated STA corresponding to link 1 is in a disabled frame exchange state. The common EMLMR switch 910' aggregates antenna resources to link 2. To this end, the common EMLMR switch 910' connects the antenna array 920a' of the second radio stack to the RF chain 915b' of the first radio stack. Therefore, the first radio stack can operate in a 4×4 MIMO antenna configuration to improve the throughput on link 2. On the other hand, link 1 can no longer be used because its antenna array 920a' is no longer available to the second radio stack.

[0407] The lower right figure illustrates the function of the MLD when the non-AP MLD switches to the second EMLMR frame exchange mode. The EMLMR co-affiliated STA corresponding to link 1 is in an enabled frame exchange state, while the other EMLMR co-affiliated STA corresponding to link 2 is in a disabled frame exchange state. The common EMLMR switch 910' aggregates antenna resources to link 1. To this end, the common EMLMR switch 910' connects the antenna array 920b' of the first radio stack to the RF chain 915a' of the second radio stack. Therefore, the second radio stack can operate in a 4×4 MIMO antenna configuration to improve the throughput on link 1. On the other hand, link 2 can no longer be used because its antenna array 920b' is no longer available to the first radio stack.

[0408] The functionality of the common EMLMR switch 910' clearly shows that the state changes of two EMLMR common affiliated STAs in the same MLD are necessarily simultaneous, since antenna resources are connected to either one of the STAs or the other, but never remain available for both STAs at the same time.

[0409] Fig.10 A communication device 1000 (typically any of the MLDs discussed above) configured to implement a wireless network of at least one embodiment of the present invention is schematically illustrated. The communication device 1000 may preferably be a device such as a microcomputer, a workstation, or a light portable device. The communication device 1000 includes a communication bus 1013, which is preferably connected to:

[0410] A central processing unit 1001 denoted as CPU, such as a processor;

[0411] Memory 1003, used to store executable codes of methods or method steps according to embodiments of the present invention, and registers suitable for recording variables and parameters required to implement these methods; and

[0412] At least two communication interfaces 1002 and 1002', which are connected to a wireless communication network (eg a communication network according to one of the IEEE 802.11 family of standards) via transmit and receive antennas 1004 and 1004', respectively.

[0413] Preferably, the communication bus 1013 provides communication and interoperability between the various elements included in or connected to the communication device 1000. The representation of a bus is not limiting, and in particular, the central processing unit is operable to communicate instructions to any element of the communication device 1000, either directly or through other elements of the communication device 1000.

[0414] The executable code may be stored in a memory (which may be a read-only hard disk) or on a removable digital medium (such as a disk). According to an optional variation, the executable code of the program may be received via interfaces 1002 and 1002' via a communication network to store the executable code in the memory of the communication device 1000 before execution.

[0415] In an embodiment, the apparatus is a programmable device that implements embodiments of the invention using software.Alternatively, however, embodiments of the invention may be implemented in whole or in part in hardware (eg in the form of an application specific integrated circuit or ASIC).

[0416] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the specific embodiments, and modifications within the scope of the present invention will be apparent to those skilled in the art.

[0417] When referring to the foregoing illustrative embodiments, those skilled in the art will appreciate many further modifications and variations, which are given by way of example only and are not intended to limit the scope of the invention, which is determined solely by the appended claims. In particular, different features from different embodiments may be interchangeable where appropriate.

[0418] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

Claims

1. A communication method in a wireless network, comprising: At a non-APMLD operating in EML mode applied in an EML link set, receiving, by a first secondary station, a first beacon frame on a first one of the EML links, the first beacon frame including a TBTT associated with a second beacon frame; as well as configuring the first auxiliary station to be in a receiving state at the TBTT to receive the second beacon frame, Among them, EML is enhanced multi-link, non-AP is non-access point, MLD is multi-link device, and TBTT is target beacon transmission time.

2. The method according to claim 1, wherein: Configuring the first auxiliary station includes ending ongoing frame exchanges on a second one of the EML links and switching the first auxiliary station to an operational state compatible with receiving the second beacon frame.

3. The method according to claim 2, wherein: Switching to an operational state compatible with receiving the second beacon frame comprises switching the first auxiliary station to a listening operational state.

4. The method according to claim 3, wherein: The second secondary station shall ignore any initial frames used to trigger a frame exchange sequence on the second link that overlap in time with the first beacon frame on the first link.

5. The method according to claim 2, wherein: Switching to an operational state compatible with receiving the second beacon frame comprises switching the first auxiliary station to a frame exchange enabled state.

6. The method according to claim 1, wherein: Configuring the first auxiliary station includes switching the first auxiliary station from a listening operation state to a frame exchange enabled state.

7. The method according to claim 1, wherein: Configuring the first auxiliary station includes ending ongoing frame exchanges on the first link and maintaining the first auxiliary station in a frame exchange enabled state.

8. The method according to claim 7, wherein: Maintaining is performed while the time distance to the TBTT is less than a predetermined threshold.

9. The method according to claim 8, wherein: The predetermined threshold is at least the sum of: A transition period required for the non-AP MLD to switch the state of its subordinate station from the listening operation state to the frame exchange enabled state or the frame exchange disabled state; as well as A transition period required for the non-AP MLD to switch the state of its subordinate station from the enabled frame exchange state or the disabled frame exchange state to the listening operation state.

10. The method according to claim 1, wherein: Configuring the first secondary station is triggered at least a first determined delay ahead of the TBTT.

11. The method according to claim 10, wherein: The first determined delay belongs to the group consisting of: an EMLSR active switching delay, an EMLMR active switching delay, and a maximum of the EMLSR active switching delay and the EMLMR active switching delay.

12. The method according to claim 1, wherein: The second beacon frame schedules a service period on the first link, and when frame exchange ends within the service period, maintains the first auxiliary station in a frame exchange enabled state until the service period ends.

13. The method according to claim 1, wherein: The second beacon frame schedules a service period on the first link, and switches the first auxiliary station to a frame exchange enabled state before the service period starts, and maintains the first auxiliary station in the frame exchange enabled state until the service period ends.

14. The method according to claim 12 or 13, wherein: At the end of the service period, the first secondary station is switched from the frame exchange enabled state to a listening operation state.

15. The method according to claim 1, wherein: The second beacon frame includes other TBTTs related to a third beacon frame for scheduling a TWT service period on the first link, wherein, while signaling the scheduled TWT service period with TWT persistence, frame exchange by the second auxiliary station on the second link in the EML link is continued without configuring the first auxiliary station to be in a receiving state at the other TBTT to receive the third beacon frame on the first link.

16. The method according to claim 1, wherein: The second beacon frame schedules a silence period on the first link, and during the silence period, switches the first secondary station to a disabled frame exchange state until the silence period ends.

17. The method according to claim 16, wherein: During the silence period, the second secondary station is switched to a state enabling frame exchange on a second one of the EML links until the silence period ends.

18. The method of claim 1, further comprising: An indication is transmitted by the non-AP MLD to the AP MLD for scheduling a service period for the non-AP MLD in a future beacon frame, the service period not overlapping in time with any beacon frame transmitted by the APMLD on a second one of the EML links.

19. A communication method in a wireless network, comprising: At a non-APMLD operating in EML mode applied in an EML link set, configuring the second auxiliary station to ignore any initial frames for triggering a frame exchange sequence on a second one of said EML links that overlap in time with beacon frames received by the first auxiliary station on a first one of said EML links, Among them, EML is enhanced multi-link, non-AP is non-access point, and MLD is multi-link device.

20. A communication method in a wireless network, comprising: At an AP MLD configured to perform a frame exchange operation with at least a given non-AP MLD operating in an EML mode applied to an EML link set, scheduling a service period for the given non-APMLD in a beacon frame transmitted by the AP MLD on a first one of the EML links, the service period not overlapping in time with any beacon frame transmitted by the AP MLD on a second one of the EML links, Among them, EML is Enhanced Multi-Link, AP is Access Point, and MLD is Multi-Link Device.

21. A communication method in a wireless network, comprising: At an AP MLD configured to perform a frame exchange operation with a non-AP MLD operating in an EML mode applied to an EML link set, transmitting an initial frame for triggering frame exchange with at least one non-AP MLD operating in the EMLSR mode and at least one non-AP MLD operating in the EMLMR mode, the AP MLD ensuring that a padding duration of the padding field of the initial frame is greater than or equal to a maximum of a value indicated in an EMLSR Padding Delay subfield received from the at least one non-AP MLD operating in the EMLSR mode and an EMLMR Delay subfield received from the at least one non-AP MLD operating in the EMLMR mode, Among them, EML is Enhanced Multi-Link, AP is Access Point, MLD is Multi-Link Device, EMLSR is EML Single Radio, and EMLMR is EML Multi-Radio.

22. A wireless communication device comprising at least one microprocessor configured to perform the method of claim 1, 19, 20 or 21.

23. A non-transitory computer-readable medium storing a program, which, when executed by a microprocessor or a computer system in a wireless device, causes the wireless device to perform the method according to claim 1, 19, 20 or 21.

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