Link-based (TWT, R-TWT) procedural support and status switching for EMLSR or EMLMR co-affiliated stations.

Abstract

This provides enhanced link-specific procedures adapted to Enhanced Multilink (EML) mode, taking into account the use of Enhanced Multilink (EML) mode. [Solution] A non-access point (non-AP) multilink device (MLD) operates in EML mode applied to a set of EML links, and a first affiliated station (STA) receives a first beacon frame via a first link of the EML links, including a target beacon transmission time (TBTT) associated with a second beacon frame, and configures the first affiliated station to be in a receiving state at TBTT in order to receive the second beacon frame.

Description

Technical Field

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

Background Art

[0002] Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless networks can be multiple access networks that support multiple users by sharing 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 standard family adopted by the Institute of Electrical and Electronics Engineers (IEEE (registered trademark)) provides a number of mechanisms for wireless communication between STAs.

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

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

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

[0007] An MLD is a logical entity having multiple stations (STAs) and a single Media Access Control (MAC) service access point (SAP) to Logical Link Control (LLC), and containing one MAC data service. Thus, an AP MLD consists of multiple affiliated APs, and a non-AP MLD consists of multiple affiliated non-AP STAs. Both AP and non-AP MLD affiliated STAs can use the 802.11 mechanism to communicate with affiliated STAs of other MLDs via each of the multiple communication links that have been set up.

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

[0009] Non-AP MLDs declare their support for EML operating modes (known as EML Capabilities) to AP MLDs during the association phase. In operating modes, activation and deactivation of EML operating modes are initiated by non-AP MLDs that send specific EHT action frames called "EML OM Notifications". The D2.0 standard states that the two modes, EMLSR and EMLMR, are mutually exclusive.

[0010] When EMLMR mode is enabled, a non-AP MLD simultaneously listens on a set of active links (so-called EMLMR links, typically consisting of two active links) to receive an Initial frame transmitted by an AP MLD and initiate frame exchange. It can then aggregate some of the physical resources of different radios used on different links (so-called EMLMR links) to send and receive data for a predefined number of supported transmit / receive spatial streams, over only one EMLMR link at a time (typically the link on which the Initial frame was received). This number may be greater than the number of transmit / receive spatial streams supported by each radio.

[0011] When EMLSR mode is enabled, a non-AP MLD simultaneously listens on a set of active links (so-called EMLSR links, usually consisting of two active links) to receive an Initial Control frame (e.g., a MU-RTS trigger frame, a BSRP trigger frame) from an AP MLD and initiate frame exchange, and then can exchange data frames with the AP MLD via only one EMLSR link at a time (usually the link that received the Initial Control frame).

[0012] This indicates that one link in ELMMR (or EMLSR) is not completely independent of the other.

[0013] Furthermore, non-AP MLDs also have the ability to initiate frame exchange with AP MLDs over a single EMLSR or ELMMR link in order to transmit uplink data. In such cases, an STA affiliated with a non-AP MLD operating in EMLSR or ELMMR mode does not need to transmit an Initial Control frame or Initial frame to initiate frame exchange with the AP MLD (non-triggered UL transmission), and accesses the radio medium according to the rules defined in Section 10.3.2.4 (NAV Setup and Reconfiguration) and Section 10.23.2 (HCF Conflict Base Channel Access (EDCA)) as specified in the IEEE 802.11-2020 standard.

[0014] The EML mode mechanism coexists with other 802.11 mechanisms. Some of these (also called "link-specific procedures") are defined on a given radio medium and operate on a given link of an EMLSR (or EMLMR) link independently of the other link. An example is the so-called Target Wake Time (TWT) procedure, and its more recent adaptation, the Restricted Target Wake Time (rTWT or R-TWT) procedure.

[0015] The implementation of EML mode can prevent link-specific procedures from functioning efficiently. For example, network activity of a non-AP MLD on a first EMLSR (or ELMMR) link can prevent the non-AP MLD from recognizing link-specific procedures (e.g., rTWT service duration) on other EMLSR (or ELMMR) links, because the non-AP MLD cannot listen on other links while operating on the first link.

[0016] The coexistence of EML mode and link-specific procedures needs improvement. [Overview of the project]

[0017] The inventors realized that non-AP MLDs are unable to participate in link-specific procedures because the network operation of the non-AP MLD on the first link causes it to fail to receive the beacon frame that announces the procedure on the other link.

[0018] Therefore, a broad objective of the present invention is to facilitate the reception of beacon frames. This should provide enhanced link-specific procedures adapted to EML mode, taking into account the use of EML mode.

[0019] In this context, a method of communication in a wireless network is provided for a non-access point (non-AP) multilink device (MLD) operating in Enhanced Multi-Link (EML) mode applied to a set of EML links, including the following: - A first affiliated station receives a first beacon frame via a first link of an EML link, wherein the first beacon frame includes a Target Beacon Transmission Time (TBTT) associated with a second beacon frame. - To receive the second beacon frame, configure the first affiliated station to be in a receiving state in TBTT.

[0020] It is understood that the first affiliated station works with the first link, and one or more other affiliated stations work with other EML links.

[0021] Therefore, non-AP MLDs consider the expected time to receive the next beacon frame (TBTT) on the first link to set their device to the appropriate receiving mode (at the corresponding first affiliated station), regardless of network activity on other links in the EML link.

[0022] As a result, since the reception of the next beacon frame is guaranteed, the non-AP MLD will come to recognize the first link-specific procedure notified by the next beacon frame.

[0023] Any feature of the present invention is defined below with reference to a method, but these can be replaced with features of an apparatus.

[0024] In some embodiments, setting the first affiliated station includes ending an ongoing frame exchange via a second link of the EML link and switching the first affiliated station to an operating state suitable for receiving a second beacon frame.

[0025] It is understood that through frame exchange via the second link, the first affiliated station is initially in an invalid frame exchange state.

[0026] Therefore, the non-AP MLD decides to stop the current frame exchange in order to change the first affiliated station from the invalid frame exchange state to a reception state suitable for receiving the next beacon frame at the time when the next beacon frame is expected. Thus, due to the interruption of the frame exchange, the beacon frame can be correctly received on the first link.

[0027] In a particular embodiment, switching to an operating state suitable for receiving a second beacon frame includes switching the first affiliated station to a listening operating state. Thereby, advantageously, the second affiliated stations can listen on their respective second EML links and, for example, receive another beacon frame simultaneously.

[0028] In certain embodiments, the second affiliated station must trigger a frame exchange sequence on the second link and ignore Initial frames that temporally overlap with the first beacon frame on the first link.

[0029] It is understood that the second affiliated station operates on a second link different from the first link.

[0030] This configuration ensures that the non-AP MLD receives the entire set of expected beacon frames regardless of the network activity on the second link.

[0031] More generally, this configuration relates to a communication method for a wireless network in a non-access point (non-AP) multi-link device (MLD) operating in an enhanced multi-link (EML) mode applied to a set of EML links, including: Configuring the second affiliated station of the non-AP MLD to trigger a frame exchange sequence on the second link of the EML link and ignore received Initial frames that temporally overlap with the beacon frame received by the first affiliated station of the non-AP MLD on the first link of the EML link.

[0032] In certain embodiments, switching to an operating state suitable for receiving the second beacon frame includes switching the first affiliated station to an active frame exchange state. This configuration prevents the non-AP MLD that has received the beacon frame from switching on the second link, for example, when the AP MLD transmits an Initial (Control) frame on the second link simultaneously with the second beacon frame.

[0033] In some embodiments, setting up a first affiliated station includes switching the first affiliated station from a listening operation state to an active frame exchange state. In this case as well, for example, when an AP MLD transmits an Initial (Control) frame on the second link simultaneously with a second beacon frame, this prevents a non-AP MLD that has received a beacon frame from switching on the second link.

[0034] In some embodiments, setting up a first affiliated station includes terminating an ongoing frame exchange via a first link and maintaining the first affiliated station in an active frame exchange state.

[0035] This means that the first affiliated station does not immediately switch back to listening mode after the frame exchange is complete. The end of the frame exchange may correspond to the end of the acquired transmission opportunity, or it may be spontaneously triggered by a non-AP MLD due to the temporal proximity of the TBTT in order to set up its device to receive the second beacon frame.

[0036] These embodiments ensure the correct reception of beacon frames while avoiding unnecessary state switching of affiliated stations.

[0037] In certain embodiments, the first affiliated station is maintained in an active frame exchange state if the time distance from the end of the frame exchange to TBTT is less than a predetermined threshold. For example, the predetermined threshold is at least the sum of the following: - Non-AP MLD requires a transition period to switch the state of its affiliated station from a listening operation state to an enabled or disabled frame exchange state, and - The transition period required by non-AP MLD to switch the state of its affiliated station from an enabled or disabled frame exchange state to a listening operation state.

[0038] This allows for fine-grained control over which non-AP MLDs can benefit from maintaining an active frame exchange state and which non-AP MLDs that have terminated frame exchanges can attempt network activity on a second link. As a result, wireless network utilization improves.

[0039] In some embodiments, setting up the first affiliated station is triggered by at least a first determined delay before TBTT. For example, the first determined delay belongs to a group that includes the EMLSR active switching delay, the ELMMR active switching delay, and the maximum value of the EMLSR and ELMMR active switching delays. This configuration ensures that the first affiliated station is in a receiving state at TBTT and can correctly receive the expected second beacon frame.

[0040] In some embodiments, the second beacon frame schedules a service period on the first link, and once it has finished frame-exchanging within the service period, it maintains the first affiliated station in an active frame-exchanging state until the end of the service period. In this configuration, the first affiliated station does not automatically switch back to a listening state as soon as frame-exchanging is complete, but remains in an active frame-exchanging state until the end of the entire service period (e.g., rTWT SP). This increases the opportunities for non-AP MLDs to exchange frames during the service period, improving network efficiency.

[0041] In some embodiments, a second beacon frame schedules a service period on the first link, switches the first affiliated station to an active frame-exchange state before the start of the service period, and maintains the active frame-exchange state until the end of the service period. In this configuration, the first affiliated station remains in an active frame-exchange state for the entire service period (e.g., rTWT SP). This increases the opportunities for non-AP MLDs to perform frame exchanges during the service period, improving network efficiency.

[0042] In a particular embodiment, the method includes switching the first affiliated station from an active frame exchange state to a listening operation state at the end of the service period.

[0043] In some embodiments, the second beacon frame includes another TBTT related to the third beacon frame that schedules the TWT service period on the first link. If a scheduled TWT service period is signaled by TWT persistence, the frame exchange performed by the second affiliated station on the second link of the EML link continues without the first affiliated station being configured to receive a third beacon frame on the first link in other TBTTs.

[0044] The TWT persistence (the Broadcast TWT Persistence field of the TWT element) is understood to indicate the number of TBTTs for which a broadcast TWT service period exists corresponding to this set of broadcast TWT parameters. Since the TWT service period repeats, non-AP MLDs do not need to obtain the next beacon frame advertising the same information. Thus, these embodiments avoid interrupting network activity on the second link, thereby improving network efficiency.

[0045] In some embodiments, the second beacon frame schedules a quiet period on the first link, and during the quiet period, switches the first affiliated station to an inactive frame-exchange state until the end of the quiet period. This means that during the quiet period, the second affiliated station operating on the second link of the EML link is switched to an active frame-exchange state until the end of the quiet period. Therefore, non-AP MLDs can quickly initiate frame-exchange on the second link, thus improving network efficiency.

[0046] In some embodiments, the method further includes the non-AP MLD sending instructions to the AP MLD to schedule a service period for the non-AP MLD that does not temporally overlap with any beacon frames transmitted by the AP MLD on the second link of the EML link in future beacon frames. Such instructions ensure that the non-AP MLD can receive beacon frames on the second link regardless of the service period scheduled on the first link.

[0047] The present invention also relates to a wireless network communication method in an access point multilink device (AP MLD) configured to perform frame-switching operations with at least a given non-AP MLD operating in Enhanced Multilink (EML) mode applied to a set of EML links, including: To schedule a predetermined non-AP MLD service period for beacon frames transmitted by AP MLD on the first link of the EML link, such that it does not overlap temporally with beacon frames transmitted by AP MLD on the second link of the EML link.

[0048] As a result, scheduled service periods (such as rTWT SP) no longer pose an obstacle to non-AP MLDs correctly receiving beacon frames.

[0049] The present invention also relates to a wireless network communication method in an access point multilink device (AP MLD) configured to perform frame-switching operations with at least a given non-AP MLD operating in Enhanced Multilink (EML) mode applied to a set of EML links, including: Send an Initial frame that triggers 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. The AP MLD ensures that the padding period of the Initial frame's Padding field is greater than or equal to the maximum value indicated in the EMLSR Padding Delay subfield and EMLMR Delay subfield received from the non-AP MLD from which the frame exchange sequence was initiated.

[0050] Therefore, an AP MLD can trigger both one or more non-AP MLDs operating in EMLSR mode and one or more non-AP MLDs operating in ELMMR mode, and the padding period shown in the Initial frame (the IC frame in EMLSR mode and the Initial frame in ELMMR mode) ensures that all of these non-AP MLDs (both MLDs operating in EMLSR mode and MLDs operating in ELMMR mode) are sufficient to switch the affiliated station state from a listening operation state to an enable / disable frame exchange state.

[0051] In connection therewith, the present invention also provides a wireless communication device comprising at least one microprocessor configured to perform any of the methods described above.

[0052] Another aspect of the present invention relates to a non-transient computer-readable medium storing a program that, when executed by a microprocessor or computer system within the wireless device, causes the wireless device to perform any of the methods described above.

[0053] At least a portion of the methods according to the present invention can be implemented on a computer. Therefore, the present invention may take the form of a hardware embodiment as a whole, a software embodiment as a whole (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which can be generally referred to herein as “circuits,” “modules,” or “systems.” Furthermore, the present invention may take the form of a computer program product embodied in a representation of any tangible medium having computer-usable program code embodied in that medium.

[0054] Since the present invention can be implemented in software, it can be embodied as computer-readable code for provision to a programmable device on any suitable carrier medium. Tangible non-transient carrier mediums may include storage media such as floppy disks, CD-ROMs, hard disk drives, magnetic tape devices, or solid-state memory devices. Transient carrier mediums may include signals such as electrical signals, electronic signals, optical signals, acoustic signals, magnetic signals, or electromagnetic signals, such as microwave signals or RF signals. [Brief explanation of the drawing]

[0055] Hereinafter, embodiments of the present invention will be described only as illustrative methods, with reference to the following drawings: [Figure 1] This illustrates a typical 802.11 network environment including ML transmission between EML-enabled MLDs in which the present invention can be implemented; [Figure 1ab] An exemplary 802.11be multilink reference model for AP MLD or non-AP MLD MLD is shown; [Figure 2] A schematic example of a frame sequence for the EMLSR operating mode as defined in the D2.0 standard is shown below; [Figure 3] This shows the format of a Target Wake Time (TWT) element adapted for use in r-TWT according to the D2.0 standard; [Figure 4] The EMLSR operating mode of a non-AP MLD negotiating an rTWT service over one of the AP MLD and EMLSR links, according to a specific embodiment of the present invention, is shown using a frame sequence; [Figure 5] The steps performed by the EMLSR-active non-AP MLD according to an embodiment of the present invention are shown using a flowchart; [Figure 6a] This shows an extended frame exchange sequence for a TWT mechanism supported by an EMLSR station according to a first embodiment of the present invention; [Figure 6b] The extended frame exchange sequence for a TWT mechanism supported by an EMLSR station, according to a second embodiment of the present invention, is shown; [Figure 6c] This shows an extended frame exchange sequence for a TWT mechanism supported by an EMLSR station according to a third embodiment of the present invention; [Figure 7] A flowchart illustrates the steps performed by an EMLSR-active non-AP MLD when the TWT service is already set up before EML operation becomes active; [Figure 8] The steps taken by an EMLSR-active non-AP MLD attempting to restrict the use of TWT services on a given number of links are illustrated in a flowchart; [Figure 9] A schematic diagram of an EMLSR-enabled architecture for implementing embodiments of the present invention is shown below; [Figure 9a] A schematic diagram of an ELMMR-enabled architecture for MLD to implement embodiments of the present invention is shown; [Figure 10] A schematic diagram of a wireless communication device according to an embodiment of the present invention is shown; [Modes for carrying out the invention]

[0056] The techniques described herein can be used in a variety of broadband wireless communication systems, including communication systems based on orthogonal multiplexing schemes. Examples of such communication systems include spatial division multiplexing (SDMA) systems, time division multiplexing (TDMA) systems, orthogonal frequency division multiplexing (OFDMA) systems, and single-carrier frequency division multiplexing (SC-FDMA) systems. SDMA systems can utilize sufficiently different directions to simultaneously transmit data belonging to multiple user terminals, such as wireless devices or STAs. TDMA systems can enable multiple user terminals to share the same frequency channel by dividing the transmission signal into different time slots or resource units and assigning each time slot to a different user terminal. OFDMA systems utilize orthogonal frequency division multiplexing (OFDM), a modulation technique that divides the bandwidth of the entire system into multiple orthogonal subcarriers or resource units. These subcarriers may be called tones, bins, etc. In OFDM, each subcarrier can be independently modulated with data. The SC-FDMA system can utilize interleaved FDMA (IFDMA), which transmits using subcarriers distributed across the system bandwidth; localized FDMA (LFDMA), which transmits using blocks of adjacent subcarriers; or extended FDMA (EFDMA), which transmits using multiple blocks of adjacent subcarriers.

[0057] The teachings herein can be incorporated into (e.g., implemented or performed by) various devices (e.g., STAs). In some embodiments, a wireless device or STA implemented in accordance with the teachings herein may or may not include an access point (referred to as a non-AP STA or STA).

[0058] Although the examples are described in the context of a WiFi® network, the present invention can be used in any type of wireless network, such as a mobile phone cellular network that implements a very similar mechanism.

[0059] AP may be implemented or known as NodeB, Wireless Network Controller (“RNC”), Evolutionary Node B (eNB), 5G Next Generation Base STA (“gNB”), Base STA Controller (“BSC”), Base Transceiver STA (“BTS”), Transceiver Function (“TF”), Wireless Router, Wireless Transceiver, Basic Service Set (“BSS”), Extended Service Set (“ESS”), Wireless Base STA (“RBS”), or other terms.

[0060] Non-AP STAs include, but may be implemented as, subscriber STAs, subscriber units, mobile STAs (MS), remote STAs, remote terminals, user terminals (UTs), user agents, user devices, user equipment (UEs), user STAs, or other terms. In some implementations, an 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 connectivity capabilities, or any other suitable processing device connected to a wireless modem. Thus, one or more embodiments taught herein may be incorporated into a telephone (e.g., a cellular phone or smartphone), a computer (e.g., a laptop), a tablet, a portable communication device, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a Global Positioning System (GPS) device, or any other suitable device configured to communicate via a wireless or wired medium. In some embodiments, a non-AP STA may be a wireless node. Such wireless nodes can provide connectivity to a network (e.g., the Internet or a wide-area network such as a cellular network) via, for example, wired or wireless communication links.

[0061] An AP manages a set of STAs (registered with or associated with the AP) that together constitute access to the wireless medium for communication purposes. The STAs (including the APs they register with) form a service set, which is hereafter referred to as the Basic Service Set (BSS). An identical physical STA operating as an access point may manage two or more BSSs (and thus corresponding WLANs), and each BSS is uniquely identified by a specific Basic Service Set Identifier (BSSID) and managed by another virtual AP implemented on the physical AP. Each STA is identified within the BSS by an identifier AID assigned by the AP at registration.

[0062] The 802.11 standard family defines various media access control (MAC) mechanisms for driving access to wireless media.

[0063] As outlined in the May 2022 draft IEEE P802.11be / D2.0, current discussions within the 802.11be task group propose introducing Multilink Operations (MLO) with respect to MAC layer operation. MLO will enable multilink devices to establish or configure multiple links and operate them simultaneously.

[0064] A multilink device (MLD) is a logical entity that has multiple affiliated STAs (STAs), a single Media Access Control (MAC) service access point (SAP) to Logical Link Control (LLC), and one MAC data service. An access point multilink device (or AP MLD) corresponds to an MLD in which each STA affiliated to the MLD is an AP (hence referred to as an "affiliated AP"). A non-access point multilink device (or non-AP MLD) corresponds to an MLD in which each STA affiliated to the MLD is a non-AP STA (hence referred to as an "affiliated non-AP STA"). In some literature, "multilink device," "ML device" (MLD), "multilink logical entity," "ML logical entity" (MLE), "multilink set," and "ML set" are synonyms referring to the same type of ML device. An exemplary architecture of a multilink device is described below with reference to Figure 1ab.

[0065] Multiple affiliated non-AP STAs of a non-AP MLD can set up communication links with multiple affiliated APs of an AP MLD, forming a multilink channel.

[0066] Links established for MLD (or "enabled links") are theoretically independent, meaning that channel access procedures and communication (to the communication medium) are performed independently on each link. Therefore, different links may have different data rates (e.g., different bandwidths, number of antennas, etc.) and may be used (each via a specific link) to communicate different types of information.

[0067] Thus, a communication link or "link" corresponds to a given channel (e.g., 20MHz, 40MHz, etc.) in a given frequency band (e.g., 2.4GHz, 5GHz, 6GHz) between an AP affiliated with an AP MLD and a non-AP STA affiliated with a non-AP MLD.

[0068] Affiliated 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) or other wireless communication standards.

[0069] Multilink aggregation theoretically allows traffic associated with a single MLD to be transmitted over multiple parallel communication links, thereby increasing network capacity and maximizing the utilization of available resources.

[0070] From an architectural standpoint, an MLD typically includes several radios to implement an affiliated STA, but the number of radios does not need to be equal to the number of affiliated STAs. In particular, a non-AP MLD may operate with more affiliated STAs than the number of radios (it can also be reduced to one).

[0071] The D2.0 standard defines several enhanced multilink operating modes (EML OM) from this physical architecture, namely Enhanced Multilink Single Radio (EMLSR) and Enhanced Multilink Multi-Radio (EMLMR). The D2.0 standard states that the two modes, EMLSR and ELMMR, are mutually exclusive.

[0072] During the association phase, a non-AP MLD declares support for EMLSR and / or EMLMR modes to the AP MLD (in the so-called EML Capabilities). In operation mode, the activation and deactivation of EMLSR or EMLMR modes are initiated by the non-AP MLD, which sends a specific EHT action frame called "EML OM Notification" that indicates the set of valid links (so-called EMLSR or EMLMR links) to which the activation of EMLSR or EMLMR mode applies. Typically, an "EMLSR / EMLMR link" consists of two valid links; however, more valid links may be used.

[0073] When EMLSR mode is enabled, non-AP MLDs simultaneously listen on a set of active "EMLSR links" to receive Initial Control frames (e.g., MU-RTS trigger frames or BSRP trigger frames) transmitted by AP MLDs, and then perform data frame exchange with AP MLDs on only one link at a time (usually the link that received the Initial Control frame). Each non-AP MLD may or may not support EMLSR operating mode.

[0074] In EMLMR mode, a non-AP MLD can aggregate some of the physical resources of multiple radios for multiple active links (so-called EMLMR links) to send and receive a predetermined number of data streams for a predetermined number of supported transmit and receive spatial streams. Since this predetermined number is greater than the number of transmit and receive spatial streams supported per radio, it provides improved throughput and reduced latency. For example, a multi-radio (MR) non-AP MLD that supports EMLMR mode on two links (with associated radios) will communicate over the two links using each radio when EMLMR mode is deactivated, such as in a 2x2 MIMO antenna configuration for each radio. On the other hand, an MR non-AP MLD, for example in a 4x4 MIMO antenna configuration, will aggregate the physical resources (usually antennas) of two radios when EMLMR mode is activated, and communicate over one of the two links using one of the radios. At the same time, the other link (the link whose physical antenna has been taken away) will be unavailable.

[0075] When ELMR mode is enabled, a non-AP MLD simultaneously listens to a set of active "EMLMR links" to receive the Initial frame transmitted by the AP MLD and initiate frame exchange, and can then perform data frame exchange with the AP MLD over only one ELMR link at a time (usually the link that received the Initial frame) (aggregating radio resources).

[0076] In the following explanation, for the sake of simplicity, we will mainly discuss the EMLSR mode. However, similar considerations are possible for the EMLMR mode as well.

[0077] Figure 1 shows a typical 802.11 network environment including ML transmission between EML-enabled MLDs (EMLSR and ELMMR compatible) in which the present invention may be implemented.

[0078] The wireless communication network 100 includes AP MLD 110 and two non-AP MLDs, 120 and 130. In this example, the two non-AP MLDs are assumed to be EML-capable and declare their ability to communicate with AP MLD 110 in the EML Capabilities' EMLSR-related and EMLMR-related fields (these fields will be referred to below as EMLSR Capabilities and EMLMR Capabilities, e.g., subparts of EML Capabilities). Of course, there may be other numbers of non-AP MLDs that register with AP MLD 110 and exchange frames with AP MLD 110, as well as other (more) numbers of EML-capable non-AP MLDs.

[0079] AP MLD110 has multiple affiliated APs, two affiliated APs 111 and 112 (also called AP1 and AP2, respectively) in the illustrative Figure 1, each operating as an 802.11 AP on an operating channel within a single frequency band. Known 802.11 frequency bands include the 2.4 GHz, 5 GHz, and 6 GHz bands. Of course, other frequency bands can be used instead of, or in addition to, these three frequency bands.

[0080] Non-AP MLD120, 130 has multiple affiliated non-AP STAs, each non-AP STA operating as an 802.11 non-AP STA in the BSS (managed by affiliated AP 111 or 112) to which it registers. In the illustrative Figure 1, two non-AP STAs 121 and 122 (also called A1 and A2, respectively) are affiliated to non-AP MLD120, and two non-AP STAs 131 and 132 (also called B1 and B2, respectively) are affiliated to non-AP MLD130.

[0081] For illustrative purposes, non-AP MLDs 120 and 130 are single-radio non-AP MLDs. For example, AP111 is configured to operate on channel 38, corresponding to an operating 40MHz channel in the 5GHz frequency band, and AP112 is configured to operate on channel 151, corresponding to another operating 40MHz channel in the same 5GHz frequency band. In another example, affiliated STAs may operate in different frequency bands.

[0082] Each affiliated AP provides a link to AP MLD110 for affiliated non-AP STAs of non-AP MLDs (120 or 130). Therefore, each link in a non-AP MLD can simply be identified by the identifier of its respective affiliated AP. In this context, each affiliated AP111 and 112 can be identified by an identifier called a “link ID”. Each affiliated AP’s link ID is unique and does not change during the lifetime of the AP MLD. The AP MLD can assign link IDs to affiliated APs by incrementing the ID from 0 (for the first affiliated AP). Of course, other expressions such as “AP ID” can be used as variations.

[0083] To perform multilink communication, each non-AP MLD120, 130 must discover, authenticate, associate, and set up multiple links with AP MLD110, with each link being established between the affiliated AP of AP MLD110 and the affiliated non-AP STA of the non-AP MLD. Each of these links, called an "enabled link," allows for separate channel access and frame exchange between the non-AP MLD and the AP MLD, based on the supported capabilities exchanged during the association.

[0084] The discovery phase is called the ML discovery procedure, and the multilink setup phase (or association phase) is called the ML setup procedure.

[0085] The ML discovery procedure enables a non-AP MLD to discover the wireless communication network 100, for example, various links to the AP MLD provided by multiple affiliated APs. Accordingly, the ML discovery procedure attempts to advertise the various affiliated APs of the AP MLD, along with their respective network information (e.g., including all or some of their capabilities and operating parameters). After the non-AP MLD discovers the wireless communication network 100 through the ML discovery procedure and the MLD authentication procedure, the ML setup procedure can select a set of candidate setup links between the non-AP MLD's affiliated non-AP STA and some of the discovered affiliated APs, and request the AP MLD 110 to set up 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 the non-AP MLD's affiliated non-AP uses to wirelessly communicate with the corresponding affiliated AP over multiple links (communication channels). During the ML setup procedure, non-AP MLDs declare some or all of their capabilities, such as EMLSR capability. For this purpose, the appropriate fields are provided in the management frame. In particular, the management frame exchanged between ML discovery and the ML setup procedure includes a new information element called the Basic Multi-Link element, which is specific to multilink operations (MLO). In effect, in all management frames containing the Basic Multi-Link element, excluding the authentication frame, non-AP or AP MLDs that are EMLSR-enabled (dot11EHTEMLSROptionImplemented is true) or EMLMR-enabled (dot11EHTEMLMROptionImplemented is true) set the EMLSR or EMLMR Support bit in the EML Capabilities subfield of the Common Info field to 1.

[0086] For illustrative purposes, in a wireless communication network 100, during the ML setup procedure, two candidate setup links are requested by a non-AP MLD120 and accepted by AP MLD110: a first link 151 between affiliated AP111 (AP1) and affiliated non-AP STA121 (A1), and a second link 152 between affiliated AP112 (AP2) and affiliated non-AP STA122 (A2). Similarly, two candidate setup links are requested by a multi-radio non-AP MLD130 and accepted by AP MLD110: a first link 161 between affiliated AP 111 (AP1) and affiliated non-AP STA131 (B1), and a second link 162 between affiliated AP112 (AP2) and affiliated non-AP STA132 (B2).

[0087] AP MLD110, non-AP MLD120, and non-AP MLD130 must be EMLSR-enabled (dot11EHTEMLSROptionImplemented is true) or EMLMR-enabled (dot11EHTEMLMROptionImplemented is true). EMLSR or EMLMR capabilities (a subpart of EML Capabilities) are exchanged during the ML discovery procedure and the multilink setup phase.

[0088] The capabilities of EMLSR and EMLMR as defined in the current D2.0 standard include the following subfields: - The "EMLSR Support" subfield indicates whether the MLD supports EMLSR operation. The EMLSR Support subfield is set to 1 if the MLD supports EMLSR operation, and to 0 otherwise. - The 3-bit subfield of "EMLSR Padding Delay" indicates the minimum MAC padding period for the padding field of the Initial Control frame requested by the non-AP MLD, as defined in Enhanced multi-link single radio operation (Section 35.3.17). The table converts the 3-bit value to a padding delay in microseconds. This delay is used to define the transition period required for the MLD to switch the affiliated station's state from listening operation to active / inactive frame exchange state. This transition period is the Initial Control frame response time length plus this delay. Therefore, this transition period is called the "EMLSR active switching delay"; - The 3-bit subfield of "EMLSR Transition Delay" indicates the transition delay time required for a non-AP MLD to switch from so-called frame-exchange mode (on one of the active links) to so-called listening operation mode on an active link. The table converts the 3-bit value to a delay in microseconds. 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, and 5 for 256 μs, with values ​​from 6 to 7 reserved; - The "EMLMR Support" subfield indicates that the MLD supports ELMR operation. If the MLD supports ELMR operation, the ELMR Support subfield is set to 1; otherwise, it is set to 0. - The 3-bit subfield "EMLMR Delay" indicates the minimum padding period required for ELMR link switching when a non-AP MLD operates in ELMR mode. This delay is used to define the transition period required for the MLD to switch the state of the affiliated station when initiating or ending a frame exchange. The transition period for frame exchange is the length of the Initial frame response (described later) plus this delay (EMLMR delay). For this reason, this initiation transition period is called the "EMLMR active switching delay"; - The "Transition Timeout" subfield indicates the timeout value for EML Operating Mode Notification frame exchange in EMLSR (or EMLMR).

[0089] When an EMLSR (or EMLMR)-enabled non-AP MLD attempts to operate in the corresponding mode over a set of valid links called EMLSR (or EMLMR) links, the STA affiliated with that non-AP MLD sends an EML Operating Mode (OM) Notification frame (as defined in the D2.0 standard) with the EMLSR (or EMLMR)Mode subfield of the EML Control field set to 1 to the AP affiliated with the EMLSR (or EMLMR)-enabled AP MLD (here, AP MLD110). An EMLSR (or EMLMR) link is indicated in the EMLSR (or EMLMR)Link Bitmap subfield of the EML Control field of the EML OM Notification frame by setting the bit position of the EMLSR (or EMLMR)Link Bitmap subfield to 1 for each EMLSR (or EMLMR) link. For example, in an EMLSR (or ELMMR)Link Bitmap, bit position i corresponds to a link whose link ID is equal to i, and is set to 1 to indicate that the link is a member of an EMLSR (or ELMMR) link.

[0090] An AP affiliated with an AP MLD that has received an EML Operating Mode Notification frame from an STA affiliated with a non-AP MLD will then send an EML Operating Mode Notification frame to one of the STAs affiliated with the non-AP MLD as an acknowledgment of the EML Operating Mode Notification sent by the STA affiliated with the non-AP MLD, within a timeout interval indicated in the Transition Timeout subfield of the EML Capabilities subfield of the Basic Multi-Link element, which begins at the end of the PPDU sent by the AP affiliated with the AP MLD.

[0091] Following the successful transmission of an EML Operating Mode Notification frame via one of the EMLSR (or ELMMR) links by an STA affiliated with a non-AP MLD, the non-AP MLD operates in EMLSR (or ELMMR) mode and the EMLSR is considered active (or ELMMR is active).

[0092] When an EMLSR-enabled non-AP MLD attempts to disable EMLSR (or ELMMR) mode, the STA affiliated with the non-AP MLD sends an EML Operating Mode (OM) Notification frame (as defined in the D2.0 standard) to the AP affiliated with the AP MLD, with the EMLSR (or ELMMR)Mode subfield of the EML Control field set to 0. Again, the AP affiliated with the AP MLD, having received the EML Operating Mode (OM) Notification frame from the STA affiliated with the non-AP MLD, sends an EML Operating Mode Notification frame as described above as an acknowledgment of the EML Operating Mode (OM) Notification frame. After the STA affiliated with the non-AP MLD successfully sends the EML Operating Mode Notification frame via one of the EMLSR (or ELMMR) links, the non-AP MLD disables EMLSR (or ELMMR) mode.

[0093] The set of STAs affiliated with an EMLSR (or EMLMR)-enabled non-AP MLD operating over an EMLSR (or EMLMR) link may be all or part of the STAs affiliated with the non-AP MLD. Hereafter, this set of STAs will be referred to as the "EMLSR co-affiliated STAs" (or EMLMR co-affiliated STAs) of the non-AP MLD.

[0094] In the example in Figure 1, the jointly affiliated STAs of non-AP MLD120 and non-AP MLD130 EMLSRs operate on the same link (e.g., the same affiliated AP, AP1 and AP2) and share the same EMLSR link.

[0095] Figure 1a shows an exemplary 802.11be multilink reference model of an MLD, either AP MLD or non-AP MLD.

[0096] The MLD includes the PHY layer 200, MAC layer 220, Logical Link Control (LLC) sublayer, and upper layers.

[0097] The upper layers may include applications that generate traffic data or use received traffic data.

[0098] The transmission and reception of traffic data are handled by the MAC220 and PHY200 layers. Such transmission and reception of traffic data can occur over multiple links 20-x, 20-y, and 20-z, as shown in Figure 1, with reference to 151, 152, 161, and 162. Three links, and therefore three affiliated stations, are shown. Of course, other configurations including two or more affiliated stations are also possible.

[0099] Traffic data is provided from the upper layer as a series of data frames, or "traffic streams." Each traffic stream and therefore each data frame is associated with an access category (AC), as defined in the EDCA mechanism (Figure 1b). This mapping between streams or data frames and ACs is performed by the classifier 213.

[0100] It should be noted that 802.11 stations (APs and non-AP stations) maintain four access categories (ACs), each having one or more corresponding transmit buffers or queues. The four ACs are conventionally defined as follows: - AC1 and AC0 are reserved for best-effort and background traffic. These traffics have the second lowest priority and the lowest priority, respectively. - AC3 and AC2 are typically reserved for real-time applications (such as audio and video transmission). They have the highest and second highest priority, respectively.

[0101] Data frames, also known as MSDUs (MAC Service Data Units), which are input from the upper layers of the protocol stack, are mapped by classifier 213 to one of the four ACs and therefore entered into the queue of the mapped AC.

[0102] Figure 1b shows an implementation model with four send queues, one for each access category.

[0103] The 802.11be multilink reference model reflects the fact that MLDs can transmit and receive data using multiple links, particularly at the MAC layer 220 and PHY layer 200 levels.

[0104] MAC layer 220 includes one Unified Upper-MAC (UMAC) layer 230 and multiple Lower-MAC (LMAC) layers 220-x, 220-y, and 220-z, each paired with a PHY layer 200-x, 200-y, and 200-z, with each pair corresponding to links 20-x, 20-y, and 20-z.

[0105] The UMAC230 performs functions common to all links, while each LMAC220-x, 220-y, and 220-z performs functions local to each link 20-x, 20-y, and 20-z. The UMAC layer provides UMAC interfaces to link-specific blocks 220-x, 220-y, and 220-z, and provides UMAC Service Access Points (SAPs) to the LLC and higher layers.

[0106] UMAC230 is responsible for link-independent MAC procedures such as authentication, association, security association, sequence number assignment, MAC protocol data unit (MPDU) encryption / decryption, aggregation / deaggregation, and acknowledgment scoreboarding procedures.

[0107] Each data unit (MSDU) with a priority (User Priority (UP) and therefore Traffic IDentifer (TID)) arriving at MAC Layer 220 from a higher layer (e.g., Link Layer) is mapped to one of the ACs in UMAC Layer 230 according to a mapping rule. Also in UMAC Layer 230, the data unit (MSDU) is provided with the next available sequence number and stored in the queue corresponding to its TID (or UP) in the mapped AC.

[0108] Each LMAC220-x, 220-y, and 220-z is responsible for link-specific functions such as channel access. In particular, each MLD Lower MAC includes its own competition-based channel access procedure, e.g., EDCA221-x, 221-y, and 221-z. Some functions require joint processing of both the UMAC230 and the LMAC220-x, 220-y, and 220-z.

[0109] As shown in Figure 1ab, each EDCA 221-x, 221-y, 221-z per link performs contention for each queue on a per-link basis. In this respect, each AC has its own set of queue contention parameters for each link, associated with priority values, and thus defines higher-priority or lower-priority traffic for MSDUs. Thus, multiple traffic queues exist to serve data traffic with different priorities for a given link. The contention window (CW) and backoff value are known as EDCA variables and are specific to each link 221-x, 221-y, 221-z.

[0110] In other words, each AC operates as an independent DCF contention entity on a given link, including its own queue backoff engine 211. Thus, each queue backoff engine 211 is associated with each traffic queue 210 to use the queue contention parameters and subtract the backoff value (from CW) to initialize the respective queue backoff counter, which is specialized for each AC and each link. The backoff counter is used to contest access to links 20-x, 20-y, and 20-z in order to transmit data stored in the AC's queue. In practice, the backoff counter is decremented from its initialization value when the medium is idle, and when the backoff counter becomes 0, transmission is permitted (access is permitted) to the corresponding affiliated STA 201-x and 201-z.

[0111] When access to the wireless medium is permitted for an AC on the link, the MSDU stored for that AC is sent to physical (PHY) layers 200-x, 200-y, and 200-z for transmission over the link.

[0112] Figure 2 shows the EMLSR operating mode in a non-AP MLD120 when AP MLD110 decides to use EMLSR mode, using a frame sequence. Of course, EMLSR mode is highlighted here as an example, but similar considerations are possible for ELMMR mode as well.

[0113] This sequence means that the non-AP MLD is operating in EMLSR mode, and that the EML Operating Mode Notification frame, which activates EMLSR mode, has been successfully sent by the affiliated STA of the non-AP MLD120. In other words, it has entered active Enhanced Multi-Link Single Radio (EMLSR) mode, which applies to a specific set of two or more active links.

[0114] Affiliated STA121 and 122 are co-affiliated STAs of EMLSR within non-AP MLD120. Each affiliated STA can be in one of three defined states: listening operation state, active frame exchange state, and inactive frame exchange state.

[0115] Non-AP MLD120s can simultaneously listen on their EMLSR links by putting the co-affiliated STAs of the EMLSRs corresponding to those links into an "awake" or "listening operation" state. For example, affiliated STAs A1 and A2 are in a listening operation state (see references 241, 242). The listening operation includes a Clear Channel Assessment (CCA) and the reception of the Initial Control frame of a frame exchange initiated by the AP MLD. Thus, in a non-AP MLD 120, the co-affiliated STAs of the two EMLSRs simultaneously listen for the reception of the Initial Control frame from the AP MLD.

[0116] When AP MLD110 attempts to initiate frame exchange with one or more non-AP MLDs on one of the EMLSR links, it initiates the frame exchange by sending an Initial Control frame 245 that explicitly triggers the non-AP MLDs. To some extent, the Initial Control frame schedules the non-AP MLDs. The Initial Control frame for frame exchange is sent in OFDM PPDU or non-HT duplicate PPDU format using rates of 6Mbps, 12Mbps, or 24Mbps (i.e., the MCS subfield in the frame is set to a maximum value of 2). As defined in the D2.0 standard, the Initial Control frame must be a MU-RTS Trigger frame or a BSRP Trigger frame as defined in IEEE standard 802.11ax(registered trademark)-2021. For such trigger frame formats containing one or more User Info fields, this condition means that frame 245 contains a User Info field destined for the non-AP MLD, i.e., the AID12 field is set to the non-AP MLD's AID (obtained at registration).

[0117] In this embodiment, and as shown in reference "IC(A)", the Initial Control frame 245 explicitly triggers a non-AP MLD A120. The Initial Control frame may explicitly trigger multiple non-AP MLDs using several User Info fields within it.

[0118] A co-affiliated STA of a non-AP MLD EMLSR (e.g., co-affiliated STA A1 in the embodiment), explicitly triggered by the Initial Control frame 245 that received the frame, initiates a state change of the co-affiliated STA of the considered non-AP MLD EMLSR (e.g., a state change of co-affiliated STAs A1 and A2 in the embodiment) and sends an Initial Control frame response (IC resp.) 246 to AP AP1 affiliated to AP MLD 110.

[0119] After receiving the Frame Exchange Initial Control frame 245 and sending an immediate response frame 246 in response to the Initial Control frame, the STA affiliated with the non-AP MLD that was listening on the corresponding link (for example, the receiving EMLSR co-affiliated STA A1 in the example) is configured to send or receive frames on the active link where the Initial Control frame 245 was received (for example, link 151 in the example). To this end, a state switching procedure is initiated that switches the receiving EMLSR co-affiliated STA from the listening operation state 241 to the "active frame exchange" or "active frame exchange" state, referenced by 251 in the figure, after an EMLSR active switching delay. In this new state, the receiving EMLSR co-affiliated STA can receive PPDUs transmitted using multiple spatial streams on the link where the Initial Control frame 245 was received. The EMLSR active switching delay corresponds to the delay time required for the non-AP MLD to switch from the EMLSR listening operation mode to the EMLSR frame exchange mode. As mentioned above, this is identified by the EML Capabilities (via EMLSR Padding Delay) that are exchanged with AP MLD.

[0120] Simultaneously, other co-affiliated STAs of the same non-AP MLD (e.g., STA A2 in the example) are configured not to send or receive over other EMLSR links until frame exchange is complete. To this end, a state switching procedure is also initiated for the co-affiliated STAs of the other EMLSRs, and those STAs are sequentially switched from listening operation state 242 to the "blindness frame" or "inactive frame exchange" state, as referenced in 252 in the figure. In particular, AP MLD does not send data to these co-affiliated STAs of the other EMLSRs.

[0121] The state switching of all jointly affiliated STAs within the same non-AP MLD is inseparable and occurs simultaneously. This is because it is a matter of allocating a complete radio resource chain (see Figure 9 below) to one STA, while the others lose that chain. In EMLMR mode, the physical resources (e.g., antennas) of one radio resource chain are allocated (aggregated) to another radio resource chain, resulting in the former losing its transmit / receive capability (see Figure 9a below).

[0122] The above indicates that when a non-AP MLD operates in EMLSR mode (more generally, either EMLSR mode or ELMMR mode), it is either in listening operation mode (its co-affiliated STA is in a listening operation state) or frame exchange mode (one of its co-affiliated STAs is in an active frame exchange state, and the other co-affiliated STA is in an inactive frame exchange state).

[0123] In EMLSR mode, as explained below with reference to Figure 9, a single complete radio resource is available, allocated only to the co-affiliated STA of the receiving EMLSR, whereas in ELMMR mode, as explained below with reference to Figure 9a, the antenna resources of one radio stack are allocated to the other radio stack, requiring simultaneous state changes.

[0124] It can be seen that only one of the co-affiliated STAs of an explicitly triggered non-AP MLD EMLSR can exchange dataframes with the AP MLD at a time.

[0125] An exemplary frame exchange sequence is shown in Figure 2, which includes the transmission (and thus downlink transmission) of an A-MPDU frame 255 by affiliated AP AP1 to co-affiliated STA A1 of an explicitly triggered non-AP MLD A 120 EMLSR, followed by a corresponding block acknowledgment 256 from the latter.

[0126] In addition to the termination of frame exchange operated by the co-affiliated STA of the receiving EMLSR, after the EMLSR Transition Delay specified in EML Capabilities, the non-AP MLD 120 switches to the listening state of the EMLSR, meaning that the co-affiliated STA A1 of the receiving EMLSR switches to listening state 241, similar to the co-affiliated STA A2 (listening state 242) of the other EMLSR. Therefore, a state switching procedure is triggered for each of the co-affiliated STAs of the EMLSR.

[0127] A non-AP MLD (in this case, non-AP MLD 120) may detect the end of a frame exchange if one of the following conditions is met: (1) The MAC of the STA affiliated with the non-AP MLD that received the Initial Control frame 245 did not receive the PHY-RXSTART.indication primitive during a timeout interval of aSIFSTime + aSlotTime + aRxPHYStartDelay, which begins at the end of the PPDU (e.g., acknowledgment 256) sent 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 affiliated with the AP MLD, or at the end of receiving a PPDU containing a frame from the AP affiliated with the AP MLD to the STA that does not require an immediate acknowledgment. This indicates that the actual exchange with the AP MLD has ended without receiving any subsequent frames from the AP MLD. (2) The MAC of the STA affiliated with the non-AP MLD that received the Initial Control frame 245 begins at the end of the PPDU (e.g., acknowledgment 256) sent by the STA of the non-AP MLD as a response to the most recently received frame (e.g., AP-MPDU frame 255) from the AP affiliated with the AP MLD (e.g., AP-MPDU frame 255), or begins at the end of the reception of a PPDU containing a frame from the AP affiliated with the AP MLD to the STA that does not require an immediate acknowledgment, during a timeout interval of aSIFSTime + aSlotTime + aRxPHYStartDelay, if the STA of the non-AP MLD receives the PHY-RXSTART.indication primitive and does not find any of the following frames in the PPDU corresponding to the PHY-RXSTART.indication: - Individually addressed frames with an RA equal to the MAC address of a STA affiliated with a non-AP MLD, - A trigger frame containing one of the User Info fields addressed to a STA affiliated with a non-AP MLD, - RA sends a CTS-to-self frame to AP MLD that is equal to the MAC address of the AP affiliated with AP MLD. - Multi-STA BlockAck frame with one of the Per AID TID Info fields addressed to a STA affiliated with a non-AP MLD, - An NDP Announcement frame with one of the STA Info fields addressed to a non-AP MLD, This addresses the situation where, after an actual exchange with the AP MLD, a non-AP MLD receives another frame from the AP MLD that is not destined for its own device (for example, there is no data destined for its own device, or there are no resources allocated to its own device). (3) An STA affiliated with a non-AP MLD that received an Initial Control frame 245 fails to respond to the most recently received frame (e.g., A-MPDU frame 255) from an AP affiliated with an AP MLD that requires an immediate response after SIFS.

[0128] Because the non-AP MLD120 has entered EMLSR listening operation mode, the AP MLD may initiate a new frame exchange sequence (with either the non-AP MLD 120 or 130) by sending a new Initial Control frame.

[0129] In the example shown in the figure, AP MLD110 decides to initiate a new sequence with non-AP MLD 120 again, using its co-affiliated STA A2 122 of the EMLSR. Specifically, AP MLD110 sends a new Initial Control frame 265 IC(A) that explicitly triggers non-AP MLD A120 using the other affiliated AP112, and this frame is received by the co-affiliated STA A2 122 of the EMLSR. The receiving co-affiliated STA A2 122 of the EMLSR sends 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 EMLSR frame exchange mode, the co-affiliated STA A2 122 of the receiving EMLSR switches from listening operation state 242 to active frame exchange state 272, and the co-affiliated STA A1 121 of the other EMLSR simultaneously switches from listening operation state 241 to inactive frame exchange state 271. Subsequently, frames 275 and 276 are exchanged during the frame exchange sequence until the end of the sequence in which the non-AP MLD 120 returns to the EMLSR listening operation mode.

[0130] A-MPDU255 / 275 is provided for illustrative purposes only. Other types of frames may be transmitted by AP MLD, for example, a basic trigger frame to trigger a UL transmission. Figure 2 shows a frame exchange in which acknowledgment 256 / 276 consists of a single frame 255 / 275, but a simpler frame exchange may include only a single frame transmitted by AP MLD without an acknowledgment, and a more complex frame exchange may include multiple exchange sequences, e.g., a cascaded TXOP (Transmit Opportunities) of UL transmissions (triggered by a basic trigger frame) and / or DL ​​transmissions (via HE MU PPDU).

[0131] This example demonstrates the advantages of EMLSR mode in terms of throughput and latency. AP MLD can quickly switch from one link to another, improving communication performance while minimizing increased complexity and cost.

[0132] In this example, the AP MLD110 initiates a frame exchange sequence with one or more designated non-AP MLDs. The D2.0 standard also allows non-AP MLDs to initiate frame exchange sequences with AP MLDs. In other words, an STA affiliated with a non-AP MLD operating in EMLSR mode does not need to send an Initial Control frame to initiate a frame exchange with an AP MLD. Such an affiliated STA accesses the radio medium according to the rules defined in Section 10.3.2.4 (NAV Setup and Reset) and Section 10.23.2 (HCF Conflict-Based Channel Access (EDCA)).

[0133] However, conventional media access mechanisms (e.g., TWT or rTWT, described below) do not define the specifics of EMLSR-active MLDs (particularly the state of co-affiliated STAs). It should be noted that an EMLSR-enabled non-AP MLD becomes EMLSR-active after successfully exchanging EML OM Notification frames with an EMLSR-enabled AP MLD, in which the EMLSR Mode subfield of the EML Control field is set to 1, the EMLSR link is identified, and the corresponding EMLSR co-affiliated STA is identified.

[0134] As stated above, the above description also applies to ELMMR modes with the following matching in implementation: ELMMR Delay applies to both EMLSR Padding Delay and EMLSR Transition Delay; the Initial frame of an ELMMR mode matches the Initial Control frame of an EMLSR mode, and similarly the Initial frame response of an ELMMR mode matches the Initial Control frame response of an EMLSR mode; although not specified in the D2.0 standard, the ELMMR listening operating state / mode may be defined to match the EMLSR listening operating state / mode in which a co-affiliated EMLSR is listening to those links before aggregation of physical radio resources.

[0135] More generally, according to the implementation of the present invention, the following delays are defined to determine the timing of the EML switching operation. This standard is insufficient to provide guidance on these timings. Some of the EML Capabilities subfields of the Common Info field of the Basic Multi-Link element specified in the standard are reused for the newly defined delays.

[0136] "EML active switch delay"

[0137] "EML Active Switching Delay" is defined as the transition period required for a non-AP MLD to switch the state of an affiliated station from an awake or listening operational state to an enabled or disabled frame exchange state. The EML Active Switching Delay ensures that the non-AP MLD completes its switching operation before the frame exchange triggered by the AP MLD.

[0138] This delay is called the "EMLSR active switchover delay" in the case of EMLSR operation, and the "EMLMR active switchover delay" in the case of ELMMR operation.

[0139] In the implementation of EMLSR's active switching delay, EMLSR Active Switching Delay = EMLSR Padding Delay + aSIFSTime + Initial Control Response Frame Transmission Time: "EMLSR Padding Delay" is a 3-bit subfield of the EML Capabilities subfield of the Common Info field of the Basic Multi-Link element; "aSIFSTime" is the nominal time (in microseconds) required from the time the MAC and PHY receive the end of a PPDU until they process the frames within it and respond with the start of a PPDU containing the earliest possible response frame. "Initial Control response frame transmission time" is the shortest Initial Control response frame time used in an EMLSR link where the EMLSR Padding Delay is determined by a non-AP MLD.

[0140] In the implementation of EMLMR's active switching delay, EMLMR active switching delay = EMLMR Delay + aSIFSTime + Initial response frame transmission time: "EMLMR Delay" is a 3-bit subfield of the EML Capabilities subfield of the Common Info field of the Basic Multi-Link element. "Initial response frame transmission time" is the shortest initial response frame time used in an ELMMR link where the ELMMR Delay is determined by a non-AP MLD.

[0141] "EML transition delay (or EML de-active switch delay)"

[0142] "EML transition delay" is defined as the transition period required for a non-AP MLD to switch the state of an affiliated station from an enabled or disabled frame exchange state to an awake or listening state. EML transition delay is useful for AP MLDs to determine when a non-AP MLD is ready to receive a subsequent Initial (Control) frame on any of the EML links.

[0143] This delay is called the "EMLSR transition delay" in the case of EMLSR operation, and the "EMLMR transition delay" in the case of EMLMR operation.

[0144] In the implementation, the EMLSR transition delay is the 3-bit subfield "EMLSR transition delay" in the EML Capabilities subfield.

[0145] In the implementation, the ELMR transition delay is the 3-bit subfield "EMLMR Delay" in the EML Capabilities subfield.

[0146] In another embodiment, the ELMMR transition delay is determined as follows: EMLMR transition delay = EMLMR Delay + aSIFSTime + Initial response frame transmission time: "EMLMR Delay" is a 3-bit subfield of the EML Capabilities subfield. "Initial response frame transmission time" is the shortest initial response frame time used in the ELMMR link, as estimated by AP MLD.

[0147] The time of the initial response frame can vary depending on the initial frame. AP MLD can estimate the time of the shortest initial response frame used in the ELMMR link (for example, the CTS frame of the highest-rate non-HT PPDU with the BSSBasicRateSet parameter).

[0148] In the case of a non-AP MLD in EMLSR mode, the time required to switch from awake / listening operation to frame exchange operation (EMLSR active switching delay) and the time required to switch back from frame exchange operation to awake / listening operation (EMLSR transition or inactive switching delay) may be different or equal.

[0149] In the case of a non-AP MLD in EMLMR mode, the time required to switch from awake / listening operation to frame exchange operation (EMLMR active switching delay) and the time required to switch back from frame exchange operation to awake / listening operation (EMLMR transition or inactive switching delay) may be different or equal.

[0150] Non-AP MLDs can determine the value of the ELMR Delay subfield to satisfy constraints related to both the ELMR active switch delay and the ELMR transition delay (for example, ELMR Delay may correspond to the maximum of the minimum allowable values ​​for the ELMR active switch delay and the ELMR transition delay).

[0151] To illustrate the ELMMR operation according to embodiments of the present invention, refer to the exemplary frame exchange sequence shown in Figure 2.

[0152] In a TXOP initiated by an AP affiliated to an AP MLD, where an ELMR STA affiliated to a non-AP MLD acts as a TXOP responder, the non-AP MLD switches to a per-link spatial stream capability defined by the EHT Capabilities element or the latest OM (if any) after an ELMR transition delay (e.g., "EMLMR Delay" or "EMLMR Delay + aSIFSTime + Initial response frame transmission time" as described above) if any of the following conditions are met and this is defined as the end of the frame exchange sequence: - The MAC of an STA affiliated with a non-AP MLD that received Initial frame 245 begins with the end of a PPDU (e.g., acknowledgment 256) sent 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 an AP affiliated with an AP MLD, or begins with the end of receiving a PPDU containing a frame from an AP affiliated with an AP MLD to the STA that does not require immediate acknowledgment, and does not receive the PHY-RXSTART.indication primitive during the aSIFSTime + aSlotTime + aRxPHYStartDelay timeout interval. - The MAC of an STA affiliated with a non-AP MLD that received Initial frame 245 begins with the end of a PPDU (e.g., acknowledgment 256) sent 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 begins with the end of receiving a PPDU containing a frame from the AP affiliated with the AP MLD to the STA that does not require immediate acknowledgment, and the STA affiliated with the non-AP MLD receives the PHY-RXSTART.indication primitive during a timeout interval of aSIFSTime + aSlotTime + aRxPHYStartDelay, and does not find any of the following frames in the PPDU corresponding to PHY-RXSTART.indication: ○ Individually addressed frames with RAs equal to the MAC address of a STA affiliated with a non-AP MLD. ○ Trigger frame containing one of the User Info fields addressed to an STA affiliated with a non-AP MLD ○ CTS-to-self frame where the MAC address of the AP affiliated to the AP MLD is equal to the MAC address of the RA. ○ Multi-STA BlockAck frame with one of the Per AID TID Info fields addressed to a STA affiliated with a non-AP MLD ○ One of the STA Info fields addressed to an STA affiliated with a non-AP MLD, and an NDP Announcement frame with a sounding NDP. - An STA affiliated with a non-AP MLD that received Initial frame 245 fails to respond to the most recently received frame (e.g., A-MPDU frame 255) from an AP affiliated with an AP MLD that requires immediate acknowledgment after SIFS.

[0153] In the above paragraph, ELMR STA refers to a non-AP STA affiliated with a non-AP MLD on an ELMR link, and OM refers to an Operation Mode notification.

[0154] To meet the low latency requirements of EHT and improve the operational efficiency of UL MU, existing mechanisms were reused and improved within the D2.0 standard, and other new mechanisms were added.

[0155] 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 multilinks allows non-AP MLDs to define (latency-sensitive) traffic streams identified by SCS identifiers (SCSIDs) and advertise them to AP MLDs. The adaptation of the SCS mechanism makes it possible to define QoS requirements for SCS streams through so-called QoS Characteristics elements, and in particular, to classify SCS streams as belonging to the corresponding uplink (UL) or downlink (DL) direction TID class.

[0156] The Target Wake Time (TWT) mechanism, originally defined in the IEEE 802.11ah and 802.11ax standards, has been adapted for inclusion in the D2.0 standard. This adaptation, known as Restricted Target Wake Time (rTWT), allows a station (affiliated to a non-AP MLD) to schedule a separate (and protected) Service Period (SP) for transmitting latency-sensitive traffic (e.g., SCS streams) over its BSS. The rTWT agreement is nothing more than a Broadcast TWT agreement negotiated between the AP and the associated non-AP station on a given link's BSS. The non-AP station establishes membership in the Broadcast TWT (or rTWT) schedule with the AP. The schedule can be defined for several TIDs (e.g., QoS characteristics identified through the SCS mechanism). The rTWT Service Periods SP (rTWT Service Periods SP) for an rTWT schedule where a protected exchange of SCS traffic streams may occur is advertised in a broadcast management frame (e.g., a beacon) using rTWT information (usually the Broadcast TWT ID (bTWT ID)) related to the negotiated rTWT SP.

[0157] While the SCS mechanism is negotiated between the initiator's non-AP MLD and AP MLD, there are still mechanisms like TWT and rTWT that are negotiated on a per-link basis, i.e., between the non-AP MLD initiator's affiliated STA and the corresponding affiliated AP of the AP MLD.

[0158] For a given link, a non-AP station establishes membership in the AP's broadcast TWT schedule, and the AP delivers a broadcast TWT parameter set to the non-AP station. The non-AP station is called a TWT-scheduled station, and the AP is called a TWT scheduling station.

[0159] Negotiations to become a member of an rTWT schedule (more commonly a broadcast TWT) or to terminate membership are performed in the exchange of frames that carry TWT elements, as shown below, with the Negotiation Type subfield set to 3 (Broadcast TWT). In particular, a non-AP STA MLD may request to become a member of a TWT schedule by sending a TWT Request frame containing TWT elements for a given rTWT schedule to an associated AP MLD.

[0160] The AP then advertises scheduled broadcast TWTs (or rTWTs) using the broadcast TWT element in management frames such as beacon frames, FILS Discovery frames, and broadcast Probe Response frames.

[0161] Figure 3 shows the format of the TWT element 300 adapted for use in r-TWT according to the D2.0 standard.

[0162] The TWT element 300 is identified by Element ID 301 and includes a "Control" field 310 and a field 320 for transmitting TWT parameter information.

[0163] The "Control" field 310 allows notification, via the "Negotiation Type" field 311, whether the TWT is a broadcast TWT or an individual TWT (individual TWT) aggregation. Therefore, the MSB of the Negotiation Type subfield 311 is the Broadcast field, and if the MSB of the subfield 311 is 1, the TWT element 300 is called a Broadcast TWT element. The other fields are of less importance in this description.

[0164] The "TWT Parameter Information" field 320 includes a single "Individual TWT Parameter Set" field for individual TWTs (not shown), and for Broadcast TWTs (when the Broadcast field in the "Negotiation Type" subfield is 1), it includes one or more "Broadcast TWT Parameter Set" fields having the format 320a shown in the figure.

[0165] The first field of the "Broadcast TWT Parameter Set" field 320a is the Request Type field 330, which includes the following: - If issued by a TWT Scheduled STA, the TWT Request Type subfield 331 is set to 1. Otherwise, it is set to 0 by the TWT Scheduled STA (AP); - TWT Setup Command subfield 332 indicates the type of TWT command: Request, Suggest, Demand, Reject if issued by a non-AP STA; Accept, Alternate, Dictate, Reject if issued by a TWT scheduling AP; - The Trigger field 333 indicates whether the TWT SP indicated by the TWT element 300 contains a trigger frame (the Trigger subfield is 1 for trigger activation in the case of an r-TWT). Such a TWT SP is called a trigger-enabled TWT SP, and a non-AP station cannot start transmitting data in it without a prior trigger by the AP; - When the Broadcast TWT Recommendation field 336 is set to 4, it indicates that the TWT specified in the Broadcast TWT element 300 is a Restricted TWT (r-TWT). In this case, the Broadcast TWT element 300 is also called a restricted TWT element (r-TWT IE), and the Broadcast TWT Parameter Set 320a is also called a Restricted TWT Parameter Set. - The other subfields are not that important: ○ The "Last Broadcast Parameter Set" subfield 334 is set to 0 to indicate another Broadcast TWT Parameter Set following this set. The "Last Broadcast Parameter Set" subfield is set to 1 to indicate that this is the last Broadcast TWT Parameter Set for the Broadcast TWT element. ○ The "Flow Type" subfield 335 indicates whether the TWT is announced (the TWT scheduling AP waits to receive a frame from the TWT scheduled STA to signal its awakened state) or not (the Flow Type subfield is 0 in the case of r-TWT in "Announce" mode, as r-TWT is a trigger-enabled TWT).

[0166] The other fields in field 320a of the Restricted TWT Parameter Set are used to define the time parameters of the rTWT schedule, as follows: - The Target Wake Time (TWT) field 340 indicates the next time (in microseconds) that a station participating in the rTWT schedule should wake up for the next rTWT SP; - The Nominal Minimum TWT Wake Duration field 350 indicates the minimum time that the TWT scheduled STA is expected to be awake after the start time of the TWT SP in order to complete a frame exchange for the duration of the TWT Wake Interval. The TWT Wake Interval of the rTWT SP is a value calculated from the TWT Wake Interval Mantissa 360 and the TWT Wake Interval Exponent 337. This is expressed in units as defined in the Wake Duration Unit subfield 312 of the Control field 310, which is typically 256 μs, for example.

[0167] The other fields in the Restricted TWT Parameter Set field 320a are used to define parameters specific to the Broadcast and Restricted properties of the rTWT SP: - Broadcast TWT Info Field 370 ○ This transmits the rTWT schedule identifier (i.e., the Broadcast TWT ID 373 (bTWT ID) used to identify rTWT SPs belonging to the same rTWT schedule). Since this identifier is not 0, the AP can schedule multiple sets of Broadcast TWT SPs with different sets of TWT parameters; ○ This identifies the number of target beacon transmission times (TBTT) for which a Broadcast TWT SP exists that corresponds to this Restricted (more commonly, Broadcast) TWT Parameter Set, via the Broadcast TWT Persistence subfield 374; ○ It also signals, through the Restricted TWT Schedule Full subfield 372, that the r-TWT scheduling AP is unlikely to accept a request from the STA in the BSS to establish new membership in the corresponding schedule (identified by bTWT ID 373); ○ Finally, it also signals whether the Restricted TWT Traffic Info field 380 exists (setting field 371 to 1) through the Restricted TWT Traffic Info Present field 371. - The Restricted TWT Traffic Info field 380 is specific to the restriction of the Broadcast TWT to a particular traffic. This field is required if the Broadcast TWT is associated with an SCS LL stream (otherwise, Traffic Info is associated with the TID) (and therefore field 371 is forced to be set to 1). ○ This includes a Traffic Info Control field 381 that indicates whether the following fields 382 and 383 are provided (e.g., "valid"). The DL TID Bitmap Valid subfield 3811 (and the UL TID Bitmap Valid subfield 3812, respectively) indicates whether the Restricted TWT DL TID Bitmap field 382 (and the Restricted TWT UL TID Bitmap field 383, respectively) has valid information. ○ The Restricted TWT DL TID Bitmap field 382 (and the Restricted TWT UL TID Bitmap field 383, respectively) identifies the TID as latency-sensitive traffic in the DL (and UL, respectively) direction (for example, a TID permitted in the rTWT as defined by the Restricted TWT element 300). The TID may define an SCS stream. A value of 1 at bit position k of the bitmap indicates that the TID k is classified as a latency-sensitive traffic stream for that transmission direction.

[0168] The TWT SP for the rTWT schedule is,<bTWT ID、TWTスケジューリングAPのMACアドレス> Uniquely identified by a tuple, the TWT scheduling AP is the affiliated AP for that link in the AP MLD.

[0169] This element, included in the TWT Request frame, allows an initiator STA to request an AP to become an r-TWT scheduled STA by negotiating an r-TWT SP for low-latency traffic. For example, an initiator STA (affiliated to a non-AP MLD) may negotiate the wake TWT, wake interval, and SCS streams allowed by the rTWT. The AP (an affiliated AP of the AP MLD on its link) provides a TWT Response frame to accept or reject the request. In other words, the STA requests membership in the rTWT schedule.

[0170] The TWT Request frame transmits a TWT element with the Negotiation Type subfield 311 set to 3 and the TWT Setup Command field 332 set to Request TWT, Suggest TWT, or Demand TWT. The Restricted TWT Parameter Set 320a indicates the Broadcast TWT ID 373 of the rTWT schedule that the STA is requesting to join. The AP may respond (TWT Response frame) by indicating that there is no new rTWT schedule for that bTWT ID (and maintaining the existing one), by providing an alternative set of parameters indicated in the TWT Request frame, or by creating a new rTWT schedule with the new bTWT ID.

[0171] Once negotiation and membership are complete, a conventional TWT / rTWT scheduled STA in the awake state may enter the Doze state and then switch back to the awake state at the rTWT start time after receiving a Beacon frame with a Restricted TWT element indicating the presence of an rTWT schedule, and then being advertised by an rTWT SP (e.g., via a beacon frame). The Beacon frame indicates that a TWT scheduling AP is attempting to send a Trigger frame or a DL BU to a TWT scheduled STA on its link.

[0172] At the start of each TWT / rTWT service term, expecting the TWT scheduled stations to be in an awake state, the TWT scheduling AP may typically use OFDMA multi-user technology (e.g., MU UL trigger-based transmission, MU DL transmission) to manage the rTWT SP and provide resource units to all or some of the awake TWT scheduled stations.

[0173] Figure 4 shows a specific embodiment of the EMLSR operating mode in a non-AP MLD120 that negotiates an rTWT service with AP MLD110 and one of the EMLSR links (e.g., link 151), using a frame sequence. Of course, the EMLSR mode is highlighted here as an example, but similar considerations can be made for the ELMMR mode.

[0174] At the beginning of the sequence, the non-AP MLD enters EMLSR listening operation mode, and the EMLSR co-affiliated STA is set to listening operation mode, and they simultaneously listen to their respective EMLSR links. The non-AP MLD may enter EMLSR listening operation mode in response to receiving an EML OM Notification frame with the EMLSR Mode subfield (in the EML Control field) set to 1. As a variation, the non-AP MLD may enter EMLSR listening operation mode by switching back from EMLSR frame exchange mode.

[0175] As shown in Figure 4 with the EMLSR-active non-AP MLD120 in EMLSR listening operation mode, the EMLSR co-affiliated STAs A1 121 and A2 122 are both in listening operation states 410 and 411.

[0176] In the example in Figure 4, EMLSR Co-affiliated STA A1 is selected as the station that negotiated the rTWT schedule on link 151. It may be a station with a full radio or a station with a light (reduced-function) radio.

[0177] Non-AP MLD120s can simultaneously listen on their EMLSR links by putting the co-affiliated STAs of the EMLSRs corresponding to those links into an "awake" or "listening operation" state. For example, affiliated STAs A1 and A2 are in a listening operation state (see references 410, 411). The listening operation includes a Clear Channel Assessment (CCA) and the reception of the Initial Control frame of the frame exchange initiated by the AP MLD. In a non-AP MLD120, the co-affiliated STAs of the two EMLSRs will therefore simultaneously listen for the reception of beacon frames as well as Initial Control frames from the AP MLD (since such beacon frames are also radiated in a low MCS and non-non-HT format).

[0178] Therefore, by receiving the beacon frame 430, the affiliated STA A1 can determine the individual transmission window (rTWT) to be reserved for its device on link 151.

[0179] Then, at the start of this reserved rTWT service period, AP MLD110 attempts to initiate a frame exchange with one or more non-AP MLDs on one of the EMLSR links, initiating the frame exchange by sending an Initial Control frame 445 that explicitly triggers the non-AP MLDs.

[0180] Upon receiving the frame explicitly triggered by the Initial Control frame 445, a co-affiliated STA of a non-AP MLD EMLSR (e.g., affiliated STA A1 in the embodiment) initiates a state change of the co-affiliated STA of the considered non-AP MLD EMLSR (e.g., state changes of affiliated STAs A1 and A2 in the embodiment) and sends an Initial Control frame response (IC resp.) 446 to AP AP1, which is affiliated to AP MLD 110.

[0181] If response 446 is sent, after an EMLSR active switching delay 499a, the non-AP MLD120 switches to EMLSR frame exchange mode, the EMLSR co-affiliated STA A1 121 switches from listening operation state 410 to active frame exchange state 420, and the EMLSR co-affiliated STA A2 122 simultaneously switches from listening operation state 411 to inactive frame exchange state 421.

[0182] Then, frames 455 and 456 are exchanged during the frame exchange sequence until the end of the sequence in which the non-AP MLD120 switches back to EMLSR listening operation mode.

[0183] Typically, an affiliated AP1 111 can send a basic trigger frame 455 to the EMLSR's co-affiliated STA A1 121 to allocate an uplink resource unit for a non-AP MLD 120. In such a case, the non-AP MLD 120, via the EMLSR's co-affiliated STA A1 121, sends an EHT TB (Extremely High Throughput Trigger-Based) PPDU 456 on its allocated resource unit.

[0184] Once frame exchange on link 151 is complete, the non-AP MLD 120 initiates the state switching procedure again to return the EMLSR co-affiliated STAs A1 121 and A2 122 to listening operation states 410 and 411. Thus, the non-AP MLD 120 switches back to EMLSR listening operation mode. The switchback 499b operates only for the EMLSR transition delay (as defined in EML Capabilities) after the completion of frame exchange within the service period.

[0185] When AP1 111, affiliated to AP MLD 110, sends an Initial (Control) frame to initiate frame exchange with at least one non-AP MLD operating in EMLSR mode and at least one non-AP MLD operating in ELMMR mode, the AP ensures that the padding period of the Padding field in the Initial Control frame is greater than or equal to the maximum value indicated in the EMLSR Padding Delay subfield and ELMMR Delay subfield of the Basic Multi-Link element received from the non-AP MLD from which frame exchange was initiated. The transition period 499a, from the perspective of an individual STA MLD 120, falls within a delay commonly referred to as the "EML active switch delay" from the AP's perspective, and consists of the maximum values ​​of the "EMLSR active switch" delay and "EMLMR active switch" delay of the triggered station.

[0186] In other words, AP1 111 affiliated with AP MLD110 sends an Initial frame that triggers a frame exchange between 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 the padding period of the Padding field in the Initial frame is greater than or equal to the maximum value indicated in the EMLSR Padding Delay subfield received from at least one non-AP MLD operating in EMLSR mode and the ELMR Delay subfield received from at least one non-AP MLD operating in ELMR mode.

[0187] The illustrative scenario in Figure 4 demonstrates how the EML operating mode and the TWT (e.g., rTWT) mechanism theoretically work together. These allow the EML station to transmit latency-sensitive streams within a separate transmit window (rTWT) reserved for the EML station. However, the resulting overall mechanism still has flaws: - The Initial Control frame 445, which explicitly triggers a non-AP MLD, and the corresponding response 446, provide significant overhead within critical resources for latency-sensitive streams. - In order to utilize scheduled rTWT SPs, the EML STA must know when the SPs will occur; therefore, the EML STA must also perform beacon reception, which is not yet anticipated in the 802.11be standard.

[0188] Generally, mechanisms and procedures that operate on a per-link basis, such as the exemplary Target Wake Time (TWT) and its more recent adaptation known as Restricted Target Wake Time (rTWT), may not be fully applicable to EML modes where EMLSR and EMLMR links are not completely independent.

[0189] After a first affiliated STA of an EML non-AP MLD negotiates a media access service or mechanism on the first link of its EML link, there has been a need to efficiently manage the EML mode of the EML non-AP MLD. If such a mechanism (link-specific procedure) is determined based on the reception of a beacon frame on the first link by the first affiliated STA, the latter should not be in blind mode during the reception of the beacon frame, and therefore, a second affiliated STA of the same EML non-AP MLD should not be communicating over a second other link of the EML link during that period.

[0190] Typically, in a TWT schedule in which an initiator non-AP station (e.g., STA A1) establishes membership with the AP of BSS (AP111), the affiliated STA (A1) must be awake (on link 151) to receive the beacon frame indicating the TWT service period, and therefore must be available at the early beginning of the service period arriving in this rTWT schedule.

[0191] Further embodiments are described with respect to TWT(rTWT), but the present invention can be extended to other link-specific procedures and should not be limited to the TWT mechanism. For example, a Quiet element corresponding to a scheduled quiet interval to protect an r-TWT SP is also a link-specific mechanism (i.e., a link-specific procedure).

[0192] Exemplary embodiments of the present invention are shown in Figures 5, 6a, 6b, and 6c.

[0193] Figure 5 shows a flowchart illustrating the steps (service duration schedule acquisition and channel access procedure) performed by an EMLSR-active non-AP MLD to operate a TWT service according to an embodiment of the present invention. Figures 6a and 6b schematically show an exemplary timeline of TWT operation as described in Figure 5.

[0194] For the sake of simplicity, this explanation will primarily focus on EMLSR mode, but the same principles apply to ELMMR mode as well.

[0195] This process begins in step 500, meaning that the non-AP MLD enters the (EMLSR or ELMMR) listening operation mode, and its co-affiliated STA is set to the listening operation state, and therefore, it is listening to each (EMLSR or ELMMR) link simultaneously. The non-AP MLD may enter the listening operation mode in response to receiving an EML OM Notification frame in which the corresponding Mode subfield (EMLSR or ELMMR Mode subfield of the EML Control field) is set to 1.

[0196] In step 510, the non-AP MLD waits until it has buffered latency-sensitive data to be sent to the AP MLD 110 (uplink). It may also consider latency-sensitive data (triggered direct-link data) that is sent to other non-AP MLDs via a direct link under the control of the AP MLD 110. As mentioned above, such data may be provided from a higher layer and stored in the non-AP MLD's buffer 210. The non-AP MLD determines the TWT negotiation to be activated on one of the EMLSR or EMLMR links (link 151 is one of the links selected in Figures 6a and 6b).

[0197] In some embodiments, if a TID-To-Link mapping is negotiated between an AP MLD and a non-AP MLD, mapping some TIDs to a set of links and some other TIDs to another set of links, the buffered latency-sensitive data corresponds to the TIDs permitted to be transmitted over the selected links and is shown in the bitmaps 3811 and / or 3912 of the TWT element 320a in rTWT format.

[0198] In response to the successful establishment of the TWT mechanism via the first link, scheduling operations (identical to step 550, further described) may be performed regarding the date of receipt of the next beacon frame (i.e., the next TBTT occurrence).

[0199] Next, in test step 520, various events may cause the non-AP MLD to perform EML configuration on its own according to the embodiment. This could be the detection of a beacon frame on the relevant link (a selected link, e.g., 151), or an EML event scheduled according to the present invention (e.g., an EML event scheduled before the start of the TWT service period).

[0200] EML events related to the reception of Beacon frames (scheduled events prior to actual reception and / or link TBTT) are processed through steps 530 to 550.

[0201] In fact, in that case, non-AP MLDs must not perform frame swaps over EMLSR or EMLMR links.

[0202] Step 530 allows for various configurations: - If there is no activity on any link, the non-AP MLD initiates a state switching procedure, and the co-affiliated STA is obligated to maintain this listening mode until the reception of beacon frames ends (steps 531 and 532). Furthermore, these EML co-affiliated STAs must ignore Initial Control frames addressed to their own device that overlap in time with beacon frames transmitted on the selected link (TBTT on the intended link). As an alternative embodiment, the selected co-affiliated STA (corresponding to the selected link from which the beacon frame is to be transmitted, e.g., link 1 151) is switched from a listening state to an active frame-exchanging state so that it can perform frame exchange (even if it intends to receive the beacon frame) (step 531), while in parallel (synchronously or simultaneously), other co-affiliated STAs of the EMLSR or EMLMR link set (e.g., one of links 2) are switched from a listening state to an inactive frame-exchanging state (step 532). This makes it easy to avoid receiving IC frames on other links. This case is shown in the subsequence “Case C” in Figure 6c. - If there is frame exchange on other EML links, the co-affiliated STA on the other links will be required to terminate its participation in TXOP (Transmit Opportunity) and switch to an EML mode suitable for receiving beacon frames. This case is shown in sub-sequence "Case A" in Figure 6a. The non-AP MLD triggers a state switching procedure for each co-affiliated STA of EMLSR or EMLMR, switching them back to the EML listening operation state. As a result, co-affiliated STA1 121 becomes able to receive beacon frame 430 normally. - If there is a frame exchange on the selected EML link, the co-affiliated STA (selected link) of the transmitting EMLSR remains in an active frame exchange state and waits for the medium to return to an idle state (it may terminate the existing TXOP as a legacy station does when the TBTT time issuance is approaching). The co-affiliated STAs of other EMLSRs also maintain their current state (inactive, step 532). This allows for continued reception of beacon frames. This case is shown in sub-sequence “Case B” in Figure 6b.

[0203] 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 from which the beacon frame is to be transmitted, e.g., link 1 151) by the non-AP MLD120 includes: - Case A: Terminate the ongoing frame exchange over the second link of the EML link and switch the first affiliated station to an operational state suitable for receiving the second beacon frame (for example, in the first variation, by switching the first affiliated station to a listening operational state, in which case the second affiliated station triggers a frame exchange sequence over the second link, ignoring any Initial frames that temporally overlap with the first beacon frame on the first link, and in the second variation, by switching the first affiliated station to an active frame exchange state); or - Case B: Terminate ongoing frame exchanges via the first link and maintain the first affiliated station in an active frame exchange state (for example, if the time distance to TBTT is less than a predetermined threshold, which in a particular embodiment is at least the sum of the (first) transition period required by the non-AP MLD to switch the state of its affiliated station from a listening operation state to an active or inactive frame exchange state and the (second) war time required by the non-AP MLD to switch the state of its affiliated station from an active or inactive frame exchange state to a listening operation state), or - Case C: Switch the first affiliated station from listening operation state to active frame exchange state.

[0204] As a result, in step 540, the co-affiliated STA of the selected EMLSR can receive the Beacon frame and analyze its contents.

[0205] As an example of the relevant content of this embodiment, the TWT Information element 300 may be analyzed to confirm the scheduling of the TWT service period (e.g., wake TWT and wake interval via fields 340, 360, and 337).

[0206] To quiet an STA during an r-TWT service period, an r-TWT scheduling AP may schedule a quiet interval that overlaps with the r-TWT SP of a given link. The overlapping quiet interval may be scheduled by including one or more Quiet elements in a Beacon frame. Thus, the Quiet element is another example of content relevant to this embodiment: namely, a non-AP MLD must not transmit during any quiet interval. Furthermore, a non-AP MLD thus decides that it must quiet one of its co-affiliated STAs during the quiet interval corresponding to an r-TWT service period to which it is not a member.

[0207] Next (step 550), the non-AP MLD can schedule an EML event in response to the mechanism determined via the beacon frame.

[0208] First, the non-AP MLD is scheduled to wake up on the selected link for the next TBTT.

[0209] In other words, when the next TBTT occurs (considering that the current TBTT occurs in relation to the first beacon frame), test step 520 is performed again, and steps 530 through 550 are performed again to indicate the detection of an EML event related to the next (second) beacon frame. Thus, the non-AP MLD implements a communication method that includes: - A first affiliated station (e.g., STA A1) receives a first beacon frame via a first link (e.g., 151) of the EML link, wherein the first beacon frame includes a target beacon transmission time (TBTT) associated with a second beacon frame. - To receive the second beacon frame, configure the first affiliated station (e.g., STA A1) to be in a receiving state via TBTT.

[0210] Optionally, after association with an AP MLD, a non-AP MLD may schedule events for TBTT timing on all EML links: this is so that link-specific procedures for all EML links can be determined (e.g., Quiet elements for non-member TWTs). If link-specific procedures are negotiated in step 510, the non-AP MLD may schedule itself for a beacon frame on a selected link for the first discovery of a TWT / rTWT element indicating the service duration of the TWT service it negotiated.

[0211] Regarding further beacon TBTT scheduling related to TWT operation, non-AP MLDs may relax the constraints on each TBTT for selected links: notification of the Broadcast TWT Persistence subfield 374 may allow determining the number of target beacon transmission time (TBTT) for which a Broadcast TWT SP exists corresponding to this Restricted (more generally Broadcast) TWT Parameter set, and therefore intermediate TBTTs may be ignored (only the beacon frame of the last TBTT of persistence information may contain new information).

[0212] In other words, in the context described above, where a non-AP MLD configures a first affiliated station (e.g., STA A1) to be in a receiving state in TBTT to receive a second beacon frame, the second beacon frame includes another TBTT related to a third beacon frame scheduling a TWT service period on the first link, and the scheduled TWT service period is signaled by TWT persistence, the frame exchange performed by the second affiliated station continues on the second link of the EML link without configuring the first affiliated station to be in a receiving state in another TBTT to receive a third beacon frame on the first link.

[0213] As is evident from Figures 6a to 6c, it is preferable that scheduled events occur before the issuance date and time (of the beacon frame or TWT period) to avoid "EML active switching delay" 499 / 499a, etc.

[0214] This is because the simultaneous switching previously defined and indicated by reference numbers 499 / 499a in the figure lasts for at most the EMLSR or EMLMR active switching delay time. In the embodiment, an EMLSR co-affiliated STA A1 is selected. It may be a station with a full radio or a station with a light (reduced functionality) radio. In practice, the switching of a co-affiliated STA of an EMLSR with a full radio (requiring only antenna connection) is shorter than the switching of a co-affiliated STA of another EMLSR with a light radio (requiring the physical and reconfiguration of the full radio chain), so non-AP MLDs can adapt their scheduling to take appropriate timing 499 / 499a into consideration with respect to their hardware configuration (e.g., by reducing the scheduling margin for links configured with full radios).

[0215] In addition, non-AP MLDs can also adapt their scheduling to take into account current activity prior to relevant events: the timing margin may be such that existing TXOPs (Figures 6a and 6b) are stopped before the switchover delay 499 / 499a.

[0216] In practice, scheduling operations are performed by the non-AP MLD on its upper MAC 230. This is because this entity can collect management frame information from all links and set the lower MAC entities 220-x / 220-y / 220-z accordingly. Since the upper MAC can be responsible for frame decoding, it can obtain the TBTT for all links, and therefore it is preferable that the U-MAC 230 controls the activity of the L-MAC (e.g., temporarily suspending activity on the medium or forcing a "listening" mode).

[0217] Alternatively, as explained in Figure 5, one could first stop the LL-MAC's TXOP activity and then switch the EML settings.

[0218] Once the reception of beacon frames on Link 1 is complete, the non-AP MLD initiates the state switching procedure again to return its co-affiliated STA to the listening operation state (step 590). Thus, the non-AP MLD switches back to listening operation mode. The switchback operates only by the EMLSR transition delay (as defined in EML Capabilities) or the ELMMR transition delay (as described above, according to the implementation of the present invention) after the completion of frame exchange.

[0219] Returning to test 520, the EML events scheduled in step 550 regarding the link-specific mechanism are processed through steps 560 to 580.

[0220] The objective of step 560 is to set the non-AP MLD to the appropriate state on the relevant link. Therefore, the state switching procedure is called for each co-affiliated STA of the EML, thus: - If a scheduled EML event is associated with a (r-)TWT service period, the non-AP MLD aims to become active for that link when the (r-)TWT period begins. Thus, the “first” link in step 561 is the link corresponding to the selected co-affiliated STA. An STA affiliated with a non-AP MLD on the corresponding link (e.g., the receiving EMLSR's co-affiliated STA A1 in the examples of Figures 6a and 6b) is configured to be able to send or receive frames on a valid link during the TWT service period (step 561). As will become clearer, the EMLSR's co-affiliated STA A1 does not need to receive an Initial Control frame for frame exchange, thus saving resources for the TWT SP. Simultaneously, other EMLSR co-affiliated STAs of the same non-AP MLD (e.g., STA A2 in the examples of Figures 6a and 6b) are configured not to send or receive on other EMLSR links until the TWT period ends. To this end, a state switching procedure is also initiated for the other EMLSR co-affiliated STAs, which switches them from listening operation (step 562) to a "blind frame" or "invalid frame exchange" state. - If a scheduled EML event is associated with a Quiet element in the (r-)TWT service period, the non-AP MLD aims to be disabled on that link when the Quiet period begins. To this end, the co-affiliated STA of the selected EMLSR on the same non-AP MLD (e.g., STA A1 in the example belonging to the link from which the beacon frame was issued) is configured not to send or receive until the frame exchange is complete (step 562). The co-affiliated STAs of other EMLSRs on the same non-AP MLD may be switched to a listening state (if hardware is possible to compensate for the deactivation of one link), or better, up to one of the co-affiliated STAs of other EMLSRs on the same non-AP MLD (e.g., STA A2 in the example) may switch from a listening state to an "active frame exchange" or "enabled frame exchange" state (step 561). In other words, in the context described above, where a non-AP MLD configures the first affiliated station (e.g., STA A1) to be in a receiving state in TBTT in order to receive a second beacon frame, the second beacon frame schedules a quiet period on the first link, and during the quiet period, switches the first affiliated station to an inactive frame-exchange state until the quiet period ends. Furthermore, when the quiet period begins, the non-AP MLD switches the second affiliated station on the second link of the EML link to an active frame-exchange state until the quiet period ends.

[0221] As already mentioned, an "EML active switching delay" is preferably considered to enable the setting at the appropriate time.

[0222] The state switching of all jointly affiliated STAs within the same non-AP MLD is inseparable and occurs simultaneously. This is because one STA is assigned a complete radio resource chain (see Figure 9a below), and the other STAs are deprived of the radio resource chain. In EMLMR mode, the physical resources (such as antennas) of one radio resource chain are assigned (aggregated) to another radio resource chain, so the former is deprived of transmit / receive capabilities (see Figure 9b below).

[0223] The above indicates that when a non-AP MLD operates in EMLSR mode (more generally, either EMLSR mode or ELMMR mode), it is either in listening operation mode (its co-affiliated STA is in a listening operation state) or frame exchange mode (one of its co-affiliated STAs is in an active frame exchange state, and the other co-affiliated STA is in an inactive frame exchange state).

[0224] After setting up in step 560, step 570 (in the examples in Figures 6a and 6b, the co-affiliated STA A1 of the receiving EMLSR operates frame exchange on the active link (the first link) for the duration of the TWT service) continues until step 580 (end of service period). This period is obtained from the TWT IE or Quiet element.

[0225] In the case of TWT, the Nominal Minimum TWT Wake Duration field 350 indicates the minimum time that a TWT-scheduled STA is expected to be awake from the start time of the TWT SP in order to complete frame exchange for the duration of the TWT Wake Interval. Therefore, the cutback operates after the end of the service period to the EMLSR transition delay (as defined in EML Capabilities). This provides more space within the TWT SP for latency-sensitive data transmission.

[0226] An example of a frame exchange sequence is shown in the following figure.

[0227] Figures 6a and 6b show the extended frame exchange sequence with respect to the TWT mechanism supported by the EMLSR station according to the present invention. For the sake of clarity, only the EMLSR mode is mainly referred to, but the same applies to the ELMMR mode.

[0228] In the embodiment, EMLSR's co-affiliated STA1 121 is selected as the relevant station in a per-link procedure. It may be a station with a full radio or a station with a light (reduced-function) radio.

[0229] Simultaneous switching continues with the maximum active switching delay of the EMLSR, as previously defined and indicated by reference numbers 499a / 499b in the diagram. In practice, the switching of a co-affiliated STA of an EMLSR with a complete radio (requiring only antenna connection) is shorter than the switching of a co-affiliated STA of another EMLSR with a light radio (because it requires the physical and reconfiguration of the complete radio chain). Therefore, the values ​​considered for 499a / 499b may correspond to the radio configuration of STA A1 (or their respective maximum values).

[0230] As shown in Figure 6a, EMLSR active non-AP MLD120, both EMLSR co-affiliated STAs A1 121 and A2 122 have switched from listening operation (not shown in the past) to a "blind frame" or "invalid frame exchange" state 610 for STA1 121 and to an "active frame exchange" or "enabled frame exchange" state 611 for STA2 122.

[0231] As previously mentioned with respect to step 530, both the termination of TXOP participation by STA A2 and the switchover following period 499b are considered, in particular here, to terminate phases 610 and 611. TXOP termination can be performed in several ways, including by shortening the data communication, by not responding to the other device (AP on link 2), or, if STA A2 is the TXOP holder, by issuing a CF-End frame.

[0232] As a result, if a non-AP STA affiliated with a non-AP MLD and operating on one of the paired EMLSR or EMLMR links aims to receive a broadcast management frame (beacon frame 430) on the first link (151), and a second non-AP STA (STA A2) affiliated with the same MLD participates in frame exchange on the second link (152) which overlaps with the TBTT of the first link, then the second non-AP STA (STA A2) and its associated AP (referred to as the second AP) should follow the following rules: - The second AP, as the TXOP holder for the second link (152), should ensure that its TXOP terminates at least T hours before the TBTT of the first link. - The second non-AP STA (STA A2) as the TXOP holder for the second link (152) should ensure that its TXOP terminates at least T hours before the TBTT of the first link.

[0233] In this embodiment, T is equal to one of the following values: - If two non-AP STAs belong to a pair of EMLSR links, the EMLSR transition delay (499b) is shown in the EMLSR Transition Delay subfield. - If two non-AP STAs belong to a pair of ELMMR links, the ELMMR delay specified for the pair of ELMMR links, as shown in the ELMMR Transition Delay subfield (e.g., the previously defined ELMMR inactive switching delay, depending on the implementation).

[0234] If multiple non-AP STAs are operating on the TXOP of the second link (152), the second AP as the TXOP holder of the second link (152) should ensure that T is greater than or equal to the largest individual T value (determined earlier here) for those non-AP STAs.

[0235] In other embodiments, T is equal to one of the following values: - If two non-AP STAs belong to a pair of EMLSR links, the EMLSR transition delay (499b) is shown in the EMLSR Transition Delay subfield; - If two non-AP STAs belong to a pair of ELMMR links, the ELMMR delay + aSIFSTime + transmission time of the initial response frame (e.g., the previously defined ELMMR inactivity switching delay, depending on the implementation).

[0236] The duration of the Initial response frame can vary depending on the Initial frame. Non-AP MLD and AP MLD may determine the duration for which the shortest Initial response frame is used in the ELMMR link (e.g., the CTS frame of the highest-rate non-HT PPDU specified by the BSSBasicRateSet parameter).

[0237] If multiple non-AP STAs are operating on the TXOP of the second link (152), the second AP as the TXOP holder of the second link (152) should ensure that T is greater than or equal to the largest individual T value (determined earlier here) for those non-AP STAs.

[0238] Simultaneous switching (for example, setting all co-affiliated STAs to "listening" mode) will last for a maximum of the EMLSR active switching delay or the previously defined EMLSR active switching delay.

[0239] In other words, the configuration of a selected co-affiliated STA or first affiliated station (STA A1) (corresponding to the selected link or first link from which the beacon frame is to be transmitted, e.g., link 1151) by a non-AP MLD120 is triggered by at least one first determined delay before TBTT (e.g., EMLSR active switch delay, ELMMR active switch delay, or the maximum value of EMLSR and ELMMR active switch delays).

[0240] This enables the reception of beacon frames for Link 1 (by STA A1). In addition, any co-affiliated STA of another EML (STA A2 in this case) must ignore any Initial Control frames addressed to its device that temporally overlap with the beacon frames of the selected link (TBTT of the intended link).

[0241] This mode can also be advantageous for receiving beacon frames via two EML links (if they are time-synchronized).

[0242] When a beacon frame is received, all EML co-affiliated STAs can perform their normal operations.

[0243] Next, arrive during the reservation period (630).

[0244] Compared to Figure 4, the EML scheduler is expected to schedule the switching of STA1 to the "active frame exchange" or "enabled frame exchange" state before the intended start of TWT SP630. Typically, the switching delay 499 / 499a (belonging to the group including EMLSR active switching delay, EMLMR active switching delay, and the maximum value of EMLSR and EMLMR active switching delay) occurs before TWT SP630.

[0245] Similar to Case A, but when TWT SP630 is applied, media activity on the EML link must be stopped (not shown).

[0246] As a result, if a non-AP STA affiliated with a non-AP MLD and operating on one of the EMLSR or EMLMR link pairs is a member of an R-TWT SP on the first link (151); if a second non-AP STA (STA A2) affiliated with the same MLD is not a member of another R-TWT SP on the second link (152) that overlaps with the first SP, then the second non-AP STA (STA A2) and its associated AP (referred to as the second AP) should follow the following rules: - The second AP, as the TXOP holder for the second link (152), should ensure that its TXOP terminates T hours before the start time of the R-TWT SP of the first link; - The second non-AP STA (STA A2) as a TXOP holder on the second link (152) should ensure that its TXOP terminates T hours before the start time of the R-TWT SP (630) on the first link.

[0247] In this embodiment, T is equal to one of the following values: - If two non-AP STAs belong to a pair of EMLSR links, the EMLSR transition delay (499b) is shown in the EMLSR Transition Delay subfield. - If two non-AP STAs belong to a pair of ELMMR links, the ELMMR delay specified for the pair of ELMMR links, as shown in the ELMMR Transition Delay subfield (e.g., the previously defined ELMMR inactive switching delay, depending on the implementation).

[0248] If multiple non-AP STAs are members of the R-TWT SP of the first link (151) and operate in the TXOP of the second link (152), then the second AP as the TXOP holder of the second link (152) should ensure that T is greater than or equal to the largest individual T value of the non-AP STAs that are members (as determined earlier here).

[0249] In other embodiments, T is equal to one of the following values: - If two non-AP STAs belong to a pair of EMLSR links, the EMLSR transition delay (499b) is shown in the EMLSR Transition Delay subfield. - If two non-AP STAs belong to a pair of ELMMR links, the ELMMR delay + aSIFSTime + transmission time of the initial response frame (e.g., the previously defined ELMMR inactivity switching delay, depending on the implementation).

[0250] The duration of the Initial response frame can vary depending on the Initial frame. Non-AP MLDs and AP MLDs may determine the duration for which the shortest Initial response frame is used in the ELMMR link (e.g., the CTS frame of a non-HT PPDU with the highest rate specified by the BSSBasicRateSet parameter).

[0251] If multiple non-AP STAs are members of the R-TWT SP of the first link (151) and operate in the TXOP of the second link (152), then the second AP as the TXOP holder of the second link (152) should ensure that T is greater than or equal to the largest individual T value of the non-AP STAs that are members (as determined earlier here).

[0252] The Initial (Control) frame 445 and corresponding response 446 used to explicitly trigger a non-AP MLD provide significant overhead within the critical TWT SP resource for latency-sensitive streams, and since the TWT SP has already been determined, the non-AP MLD can set its affiliated EML STA so that it is ready to operate during TWT SP 630.

[0253] If a non-AP MLD120 wishes to initiate a frame exchange sequence with AP MLD110 during TWT SP630 (where the co-affiliated STA A1 121 of the EMLSR is selected as the co-affiliated STA of the transmitting EMLSR in the negotiated TWT), it switches the co-affiliated STA A1 121 of the EMLSR from listening operation state 410 to active frame exchange state 620, and in parallel (synchronously or simultaneously) switches the co-affiliated STA A2 122 of the EMLSR from listening operation state 411 to inactive frame exchange state 621.

[0254] The listening operation state is restored and becomes operational after the completion of TWT SP630, which corresponds to the rollback (a period of 499b defined by the EMLSR Transition Delay set in EML Capabilities).

[0255] In other words, in the context where the non-AP MLD sets the first affiliated station (e.g., STA A1) to be in the receiving state at the TBTT to receive the second beacon frame, the second beacon frame schedules the service period on the first link, and when the frame exchange within the service period is completed, the non-AP MLD maintains the first affiliated station in the active frame exchange state until the end of the service period. In certain embodiments, the non-AP MLD switches the first affiliated station to active frame exchange before the start of the service period and maintains it in the active frame exchange state until the end of the service period. Further, at the end of the service period, the non-AP MLD switches the first affiliated station from the active frame exchange state to the listening operation state.

[0256] The co-affiliated STAs of the EMLSR switch back to the listening operation mode for the entire service period 630, regardless of the duration field of the frame (basic trigger 455) that triggered it (or more generally, after the end of the frame exchange with its AP). This can support multiple frame exchanges with the AP during the service period 630 (if any) without the overhead due to further Initial (Control) frame / response EML activation sequences.

[0257] FIG. 6b shows a variation of the frame exchange sequence compared to FIG. 6a, where the co-affiliated STAs A1 121 and A2 122 of the EMLSR start in the "active frame exchange" or "valid frame exchange" state 611 for STA1 121 and in the "blind frame" or "invalid frame exchange" state 610 for STA2 122, respectively.

[0258] Only the underlined sequence of "Case B" is different.

[0259] STA1 121 is already operating on the EMLSR link 151 for frame exchange with the AP MLD.

[0260] Normally, according to 802.11be D0.5, when a non-AP MLD STA starts a TXOP, after the end of the TXOP, the non-AP MLD switches back to the listening operation of the EMLSR link after the period indicated by the EMLSR Transition Delay subfield (499b).

[0261] This rule is applicable to the current situation where the TBTT is next to the TXOP. As already discussed, the TXOP of link 151 can be shortened to respect the TBTT time of that link.

[0262] The embodiment provides that the non-AP MLD maintains the current EML setting until the beacon frame is received: To enable the reception of the beacon frame, the co-affiliated STAA1 remains in the valid frame exchange state 620a, and the co-affiliated STA A2 remains in the invalid frame exchange state 621a (this avoids changing the EML mode due to the reception of the Initial frame during that period).

[0263] In a different operation, the non-AP MLD first determines the remaining time at TBTT, and based on that time, decides whether to return to the listening operation mode or remain in the current EMLSR frame exchange mode. For example, if the time is long (e.g., if its value is higher than the threshold), the co-affiliated STA of the EMLSR switches back to the listening operation mode (thus, the situation of case C shown in FIG. 6c occurs). And if the time is short (e.g., if its value is lower than the threshold), the co-affiliated STA of the EMLSR maintains the current state.

[0264] FIG. 6c first shows an extended frame exchange sequence ("Case C") regarding the support of beacon frames by the EML stations according to the embodiment.

[0265] The embodiment provides that a non-AP MLD can switch only one EMLSR's co-affiliated STA to an active state (for example, switching to an active frame exchange state for the selected EMLSR's co-affiliated STA and to an inactive transmitting EMLSR's co-affiliated STA for the other EMLSRs).

[0266] In the diagram, a co-affiliated STA (corresponding to the selected link on which the beacon frame is intended, e.g., link 1 151) is switched from a listening state to an active frame-exchange state 660 so that frame exchange can be performed (even if only attempting to receive a beacon frame), and in parallel (synchronously or simultaneously), other co-affiliated STAs in the set of EMLSR or EMLMR links (e.g., one of link 2) are switched from a listening state 411 to an inactive frame-exchange state 661.

[0267] Figure 6c also shows an extended frame exchange sequence ("Case D") with respect to the support of a quiet period for the rTWT mechanism by the EML station according to the present invention.

[0268] This corresponds to the application of step 561 to events in a scheduled quiet period. In an embodiment, this may correspond to a quiet period encompassing a (r-)TWT service period in which an EML station is not a member.

[0269] In this context, activity on the first link (where the beacon is received and a quiet period for TWT is indicated) is prohibited. Therefore, another EML link may be used to become active during that time.

[0270] Subsequently, according to the EMLSR mechanism, after an EMLSR active switching delay of 499, the non-AP STA is scheduled to switch from EMLSR listening operation mode to EMLSR frame-exchanging mode, with respect to deploying one of the EMLSR co-affiliated STAs that are operational for frame-exchanging on a link different from the prohibited first link. The EMLSR co-affiliated STA, including the first link 151 on which STA A1 received the beacon frame, is disabled.

[0271] In this example, the EMLSR co-affiliated STA A2 switches from listening operation state 411 to active frame exchange state 651, and in parallel (synchronously or simultaneously), the transmitting EMLSR co-affiliated STA A1 switches from listening operation state 410 to inactive frame exchange state 650.

[0272] Figures 7 and 8 illustrate, using flowcharts, the steps an EMLSR-active non-AP MLD performs to set up a TWT service. Essentially, they detail step 510, which determines which EML Co-affiliated STA is authorized to negotiate the Link Service.

[0273] Figure 7 provides guidance for the case where the TWT service is already set up before the EML operation is about to be activated.

[0274] For example, a non-AP MLD has one TWT service established on link 151 for a jointly affiliated STA A1 (step 710).

[0275] Step 720 corresponds to step 500 and means that the non-AP MLD attempts to operate in EMLSR / EMLMR mode, activates EMLSR / EMLMR mode, and successfully sends an EML Operating Mode Notification frame to the non-AP MLD 120 indicating affiliated STA A1 and A2.

[0276] Step 730 aims to inform the AP, according to the embodiment, that one of the EML links must be monitored for both EML operation and a per-link mechanism (such as TWT). The purpose of such notification is to prevent link conflicts for events that the AP monitors. In the embodiment, since the AP MLD controls the scheduling of TWTs and beacons for all 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 sends a notification to the AP MLD to schedule a service period (on the first link) for the non-AP MLD that does not temporally overlap with beacon frames transmitted by the AP MLD on the second link of the EML links in future beacon frames. Such notification ensures that the non-AP MLD can receive beacon frames via the second link 152 regardless of the service period scheduled on the first link 151.

[0277] As exemplary support for such notification, there is bit B15 (338) of the TWT Request subfield 331 of the TWT element 300. Thus, the "EML" field 338 can indicate whether the TWT SP indicated by the TWT element 300 is operating on a link where EML operation is enabled and the non-AP MLD originator of the TWT element is requesting AP assistance to avoid EML link conflicts. (The AP is requested to avoid scheduling r-TWT SPs for EML STAs that overlap with beacons on other EML links).

[0278] Figure 8 briefly illustrates the steps taken by a non-AP MLD attempting to restrict the use of the TWT service through a given number of links. While managing more links is possible, it may appear complex and inefficient (due to too many EML active / interruption cycles).

[0279] In step 810, the EML non-AP MLD is already operating in the EML (EMLSR or EMLMR) mode. The non-AP MLD receives an internal request (e.g., from a local application above the MAC) to open a new TWT service. By increasing the number of links for which an EML event (step 550) is scheduled, the EML operating mode according to the previous embodiments (cases A to C in the previous figures) can be periodically forced. Thus, the non-AP MLD may be required to interrupt existing TXOPs more frequently. This can also occur frequently when the TBTT interval of the link is short.

[0280] If the number of links is more than the desired number, the non-AP MLD may reject new (r)TWTs of other links. The algorithm stops. Otherwise, the non-AP MLD may close the existing rTWT service on the first link (step 820) and reinstall it in addition to the new upcoming TWT service on the second link (step 830). As an example from FIGS. 6a to 6c, this means that all TWT services are placed on a single link (here link 151).

[0281] In summary, the above-described embodiments provide that when a STA affiliated with the non-AP MLD attempts to receive a beacon frame scheduled at the TBTT on one (the first) link of its EML (EMLSR or EMLMR) links, the non-AP MLD must enable listening on the EML (EMLSR or EMLMR) link. Thus, the following rules must be satisfied: - If another STA affiliated with the same non-AP MLD successfully obtains a TXOP on another link of the EML (EMLSR or EMLMR) link, it should end the TXOP before the TBTT of that (the first) link (see FIG. 6a, case A) - If the same STA affiliated to the same non-AP MLD is part of the TXOP on the intended (first) link of the EML (EMLSR or ELMMR) link, that STA may remain awake on that link until TBTT (see Figure 6b, Case B). - An STA affiliated with the same non-AP MLD that is in listening state on an EML (EMLSR or ELMMR) link must ignore Initial Control frames addressed to its own device that overlap with the intended (first) link TBTT (for example, temporally overlap with a beacon frame sent in the TBTT on the first link).

[0282] Receipt of a beacon frame on a single EML (EMLSR or ELMMR) link is fulfilled if any of the following conditions are met: - A TWT or rTWT aggregation is established on that EMLSR link. - To protect the r-TWT SP, a Quiet element corresponding to the Quiet interval is scheduled.

[0283] Figure 9 schematically illustrates an EMLSR-enabled architecture for MLD. This figure illustrates a case where two non-AP STAs share the hardware resources of a non-AP MLD when EMLSR mode is enabled. The EMLSR-enabled architecture for MLD shown in this figure is for illustrative purposes only, and other alternative architectures are possible.

[0284] This architecture includes two wireless stacks: a lightweight wireless stack and a full wireless stack.

[0285] The complete radio stack includes a complete 802.11be MAC module 900a (for exchanging data with the upper layer), a complete 802.11be PHY module 905a connected to the complete MAC module, a complete radio frequency chain 915a connected to the complete PHY module, and an antenna 920a connected to the complete RF chain via an EMLSR switch 910.

[0286] The light radio stack includes a light 802.11be MAC module 900b (which exchanges data with the upper layer), a light 802.11be PHY module 905b connected to the light MAC module, a light radio frequency chain 915b connected to the light PHY module, and an antenna 920b connected to the light RF chain via an EMLSR switch 910.

[0287] The EMLSR switch 910 is shared by two radio stacks and is configured to switch the EMLSR co-affiliated STA from / to an active frame exchange state or an inactive frame exchange state when EMLSR mode is enabled.

[0288] Wireless chains 900a / 905a / 915a are complete wireless resources that enable the reception and transmission of any IEEE 802.11 frame. In particular, they include encoding and decoding modules for encoding and decoding any IEEE 802.11 frame. Wireless chains 900b / 905b / 915b, on the other hand, are reduced-function (or "light") wireless resources that enable the reception and transmission of only specific IEEE 802.11 frames. In particular, they include only encoding and decoding modules for encoding and decoding specific frames using rates of 6Mbps, 12Mbps, or 24Mbps.

[0289] The diagram in the lower left shows the function of the MLD when a non-AP MLD is in ELMMR listening operation mode: The common ELMMR switch 910 connects each radio chain 900a / 905a / 915a and 900b / 905b / 915b to antennas 920a and 920b, respectively. Thus, each radio stack can be used to listen to its respective link simultaneously. As shown in the diagram, two links are available. The complete 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.

[0290] The diagram at the bottom center shows the function of the MLD when a non-AP MLD switches to the first EMLSR frame exchange mode. The co-affiliated STA of the EMLSR corresponding to Link 1 is in the active frame exchange state, and the co-affiliated STA of the other EMLSR corresponding to Link 2 is in the inactive frame exchange state. In this case, the common EMLSR switch 910 connects the complete radio chain 900a / 905a / 915a to both antennas 920a and 920b, and the complete radio chain 900a / 905a / 915a and antennas 920a / 920b are configured to operate on Link 1. Here, since the complete radio chain remains configured to operate on Link 1, the switching period from the EMLSR listening state to the active frame exchange state can be considered short. In fact, in this case, the switching only involves switching antennas. On the other hand, the common EMLSR switch 910 disconnects the light radio chain 900b / 905b / 915b from antenna 920b. In this configuration, the lightweight wireless chains 900b / 905b / 915b cannot receive or transmit frames on link 2. Only link 1 is available.

[0291] The diagram in the lower right shows the function of the MLD when a non-AP MLD switches to the second EMLSR frame exchange mode. The co-affiliated STA of the EMLSR corresponding to Link 2 is in the active frame exchange state, while the co-affiliated STA of the other EMLSR corresponding to Link 1 is in the inactive frame exchange state. In this case, the common EMLSR switch 910 connects the complete radio chain 900a / 905a / 915a to both antennas 920a and 920b, and the complete radio chain 900a / 905a / 915a and antennas 920a / 920b are configured to operate on Link 2. Here, since the complete radio chain switches to operate on Link 2, the switch time from the EMLSR listening state to the active frame exchange state can be considered long. In fact, in this case, the switch involves both antenna switching and switching the configuration of the complete radio chain. On the other hand, the common EMLSR switch 910 disconnects the light radio chains 900b / 905b / 915b from antenna 920b. In this configuration, the light radio chains 900b / 905b / 915b cannot receive or transmit frames on link 1, and only link 2 is available.

[0292] The common EMLSR switching function of the 910 is that the radio chain is either connected to one STA or to the other STA, but since both STAs cannot be available at the same time, it clearly indicates that the state changes of the jointly affiliated STAs of two EMLSRs within the same MLD are necessarily simultaneous.

[0293] Figure 9a schematically shows the ELMMR-enabled architecture of the MLD. This figure illustrates the case where two affiliated non-AP STAs share antenna resources when ELMMR mode is activated.

[0294] This architecture includes two radio stacks, one for each non-AP STA.

[0295] The radio stack includes a complete 802.11be MAC module 900a' or 900b' (exchanging data with the upper layer), a complete 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 ELMMR switch 910' shared by the two radio stacks and configured to perform antenna resource aggregation when ELMMR mode is activated, and an antenna array 920a' or 920b'.

[0296] The diagram in the lower left shows the functionality when a non-AP MLD is listening to the initial frame: a common ELMMR switch 910' connects each antenna array to the RF chain. Thus, each radio stack is complete and can serve its respective link using, for example, a 2x2 MIMO antenna configuration. As shown in the diagram, two links are available.

[0297] The diagram at the bottom center shows the function of the MLD when the non-AP MLD switches to the first ELMMR frame-exchange mode. The co-affiliated STA of the ELMMR corresponding to Link 2 is in an active frame-exchange state, while the co-affiliated STA of the other ELMMR corresponding to Link 1 is in an inactive frame-exchange state. The common ELMMR switch 910 aggregates antenna resources to Link 2. To do this, it connects the antenna array 920a' of the second radio stack to the RF chain 915b' of the first radio stack. Thus, the first radio stack operates in a 4x4 MIMO antenna configuration, which can improve throughput to Link 2. Meanwhile, Link 1 becomes unavailable because its antenna array 920a' is no longer available to the second radio stack.

[0298] The diagram in the lower right shows the function of the MLD when the non-AP MLD switches to the second ELMMR frame exchange mode. The co-affiliated STA of the ELMMR corresponding to Link 1 is in an active frame exchange state, while the co-affiliated STA of the other ELMMR corresponding to Link 2 is in an inactive frame exchange state. The common ELMMR switch 910' aggregates antenna resources to Link 1. To this end, it connects the antenna array 920b' of the first radio stack to the RF chain 915a' of the second radio stack. Thus, the second radio stack operates in a 4x4 MIMO antenna configuration, which can improve throughput to Link 1. Link 2, on the other hand, becomes unusable because its antenna array 920b' is no longer available to the first radio stack.

[0299] The common function of the ELMMR switch 910' is that the antenna resource is either connected to one STA or to the other STA, but since both STAs are never available simultaneously, this clearly indicates that the state changes of the jointly affiliated STAs of two ELMMRs within the same MLD are necessarily simultaneous.

[0300] Figure 10 schematically shows a communication device 1000, typically one of the MLDs described above, in a wireless network configured to carry out at least one embodiment of the present invention. The communication device 1000 may preferably be a device such as a microcomputer, workstation, or lightweight portable device. The communication device 1000 preferably includes a communication bus 1013 to which the following are connected: A central processing unit such as a processor, referred to as a CPU, 1001; Memory 1003 for storing executable code for a method or step of a method according to an embodiment of the present invention, and registers adapted for recording variables and parameters necessary for carrying out the method; and At least two communication interfaces 1002 and 1002' are connected to a wireless communication network (for example, a communication network conforming to one of the standards of the IEEE 802.11 family) via transmit / receive antennas 1004 and 1004', respectively.

[0301] Preferably, the communication bus 1013 provides communication and interoperability between various elements included in or connected to the communication device 1000. The representation of the bus is not limited, and in particular, the central processing unit can be operated to communicate instructions directly to any element of the communication device 1000 or through another element of the communication device 1000.

[0302] The executable code may be stored in the memory of a read-only hard disk or a removable digital medium such as a disk. According to an optional modification, the program's executable code may be received by a communication network via interface 1002 or 1002' so that it is stored in the memory of communication device 1000 before execution.

[0303] In one embodiment, the device is a programmable device that uses software to implement embodiments of the present invention. Alternatively, embodiments of the present invention may be implemented in whole or in part in hardware (e.g., in the form of an Application Specific Integrated Circuit or ASIC).

[0304] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to specific embodiments, and modifications within the scope of the present invention will be obvious to those skilled in the art.

[0305] Many further modifications and variations will be suggested to those skilled in the art by reference to the exemplary embodiments described above, but these embodiments are given only as examples 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 substituted where appropriate.

[0306] In the claims, the term “comprising” does not exclude other elements or steps, and the indefinite articles “a” or “an” do not exclude plurals. The mere fact that different features are described in different dependent claims does not imply that combinations of these features cannot be used advantageously.

Claims

1. A method for communicating in a wireless network in a non-access point (non-AP) multilink device (MLD) operating in EML mode applied to a set of enhanced multilink (EML) links, The first affiliated station receives a first beacon frame via the first link of the EML link, wherein the first beacon frame includes a target beacon transmission time (TBTT) associated with the second beacon frame. This includes setting the first affiliated station to be in a receiving state in TBTT in order to receive the second beacon frame. method.

2. Setting up the first affiliated station includes terminating the ongoing frame exchange via the second link of the EML link and switching the first affiliated station to an operating state suitable for receiving the second beacon frame. The method according to claim 1.

3. Switching to an operating state suitable for receiving the second beacon frame includes switching the first affiliated station to a listening operating state. The method according to claim 2.

4. The second affiliated station triggers a frame exchange sequence on the second link, ignoring Initial frames that temporally overlap with the first beacon frames on the first link. The method according to claim 3.

5. Switching to an operating state suitable for receiving the second beacon frame includes switching the first affiliated station to an active frame exchange state. The method according to claim 2.

6. Setting up the first affiliated station includes switching the first affiliated station from a listening operation state to an active frame exchange state. The method according to claim 1.

7. Setting up the first affiliated station includes terminating the ongoing frame exchange via the first link and maintaining the first affiliated station in an active frame exchange state. The method according to claim 1.

8. Maintain if the time distance to the aforementioned TBTT is less than a predetermined threshold. The method according to claim 7.

9. The predetermined threshold is at least The non-AP MLD requires a transition period to switch the state of the affiliated station of the non-AP MLD from a listening operation state to an active frame exchange state or an inactive frame exchange state, The non-AP MLD is the sum of the transition period required to switch the state of the affiliated station of the non-AP MLD from the active frame exchange state or the inactive frame exchange state to the listening operation state. The method according to claim 8.

10. Setting up the first affiliated station is triggered at least a first determined delay before the TBTT. The method according to claim 1.

11. The first determined delay belongs to a group that includes the EMLSR active switching delay, the EMLMR active switching delay, and the maximum values ​​of the EMLSR and EMLMR active switching delays. The method according to claim 10.

12. The second beacon frame schedules a service period on the first link, and if it completes frame exchange within the service period, it maintains the first affiliated station in an active frame exchange state until the end of the service period. The method according to claim 1.

13. The second beacon frame schedules a service period on the first link, switches the first affiliated station to an active frame exchange state before the start of the service period, and maintains the active frame exchange state until the end of the service period. The method according to claim 1.

14. At the end of the service period, the first affiliated station is switched from the active frame exchange state to the listening operation state. The method according to claim 12 or 13.

15. The second beacon frame includes other TBTTs related to a third beacon frame that schedules a TWT service period on the first link, and if the scheduled TWT service period is signaled with TWT persistence, the frame exchange performed by the second affiliated station on the second link of the EML link continues without configuring the first affiliated station to be in a receiving state with the other TBTT to receive the third beacon frame on the first link. The method according to claim 1.

16. The second beacon frame schedules a quiet period on the first link and, during the quiet period, switches the first affiliated station to an invalid frame exchange state until the quiet period ends. The method according to claim 1.

17. During the aforementioned quiet period, until the end of the quiet period, the second affiliated station is switched to an active frame exchange state via the second link of the EML link. The method according to claim 16.

18. The non-AP MLD further includes sending a notification to the AP MLD via a second link of the EML link to schedule a service period for the non-AP MLD in a future beacon frame that does not overlap in time with the beacon frames transmitted by the AP MLD. The method according to claim 1.

19. A method for communicating in a wireless network in a non-access point (non-AP) multilink device (MLD) operating in EML mode applied to a set of enhanced multilink (EML) links, This includes triggering a frame exchange sequence on the second link of the EML link and configuring the second affiliated station to ignore Initial frames that temporally overlap with beacon frames received by the first affiliated station on the first link of the EML link. method.

20. A method for communicating in a wireless network in an access point (AP) MLD configured to perform frame-switching operations with at least a predetermined non-access point (non-AP) multilink device (MLD) operating in EML mode applied to a set of enhanced multilink (EML) links, In the beacon frame transmitted by the AP MLD on the first link of the EML link, a predetermined non-AP MLD service period is scheduled that does not temporally overlap with the beacon frame transmitted by the AP MLD on the second link of the EML link. method.

21. A method for wireless network communication between a non-access point (non-AP) multilink device (MLD) operating in EML mode applied to a set of enhanced multilink (EML) links and an access point (AP) MLD configured to perform frame-switching operations, Sending an Initial frame to trigger a frame exchange between 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 the padding period of the Initial frame's Padding field is greater than or equal to the maximum value indicated in the EMLSR Padding Delay subfield received from at least one non-AP MLD operating in EMLSR mode and the EMLMR Delay subfield received from at least one non-AP MLD operating in EMLMR mode. method.

22. A wireless communication device comprising at least one microprocessor configured to perform the method described in any one of claims 1, 19, 20, or 21 Wireless communication device.

23. A non-temporary computer-readable medium for storing a program, which, when executed by a microprocessor or computer system in a wireless device, enables the wireless device to perform the method according to any one of claims 1, 19, 20, or 21. Non-temporary computer-readable media.

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