COMMUNICATION APPARATUS AND METHOD FOR PERFORMING MULTI-LINK SETUP AND LINK MAINTENANCE - Patent application

Abstract

A communications apparatus and method for performing multi-link setup and link maintenance is provided. One exemplary embodiment provides a first station (STA) included in a first plurality of STAs belonging to a first multi-link device (MLD), the first STA comprising: circuitry that, in operation, generates a request frame, the request frame including request information; and a transmitter that, in operation, transmits the request frame to a second STA to request multi-link setup, the second STA being included in the second plurality of STAs belonging to a second MLD, the multi-link setup establishing one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present invention relate generally to communication devices, and more particularly to methods and apparatus for multi-link setup and link maintenance. [Background technology]

[0002] Today, communication devices are expected to perform the same functions wirelessly as wired computing devices. For example, users expect to be able to seamlessly watch high definition movies streamed to their wireless communication devices. This creates challenges for the communication devices and the access points to which they wirelessly connect.

[0003] The Institute of Electrical and Electronics Engineers (IEEE) 802.11 group recently formed an 802.11 Task Group (TG) to address these challenges. Multilink operation in the 2.4 GHz, 5 GHz, and 6 GHz frequency bands has been identified as an important candidate technology for such communications. Multichannel aggregation across multiple links is a natural way to increase communication data throughput several-fold. Summary of the Invention [Problem to be solved by the invention]

[0004] To enable such multi-link operation between an Access Point (AP) Multi-Link Device (MLD) and a non-AP MLD, it is necessary to establish associations of Associated Stations (STAs) on one or more links, which requires performing a multi-link setup on one of the supported links. [Means for solving the problem]

[0005] One non-limiting and exemplary embodiment facilitates providing a first station (STA) included in a first plurality of STAs belonging to a first multi-link device (MLD), the first STA comprising: circuitry that, when operational, generates a request frame, the request frame including request information; and a transmitter that, when operational, transmits the request frame to a second STA to request a multi-link setup, the second STA being included in a second plurality of STAs belonging to a second MLD, the multi-link setup establishing one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information.

[0006] Another non-limiting and exemplary embodiment facilitates providing a second STA, the second STA being included in a second plurality of STAs belonging to a second multi-link device (MLD), the second STA comprising: a receiver that, in operation, receives a request frame from a first STA, the first STA being included in the first plurality of STAs belonging to the first MLD, the request frame including request information and requesting a multi-link setup to establish one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information; and a transmitter that, in operation, transmits a response frame to the first STA to notify a result of the multi-link setup, the response frame conveying information of the one or more links established between the one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs.

[0007] Another non-limiting and exemplary embodiment promotes providing a communication method, the communication method including: generating a request frame in a first STA included in a first plurality of STAs belonging to a first MLD, the request frame including request information; and transmitting the request frame to a second STA to request a multi-link setup, the second STA being included in the second plurality of STAs belonging to a second MLD, the multi-link setup establishing one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information.

[0008] It should be noted that the general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof. Further benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. Benefits and / or advantages may be obtained individually from various embodiments and features of the specification and drawings, and not all need be provided to obtain one or more of such benefits and / or advantages. [Brief description of the drawings]

[0009] The accompanying drawings, together with the following detailed description, are incorporated in and constitute a part of this specification, and serve to illustrate various embodiments and to explain various principles and advantages according to the present embodiments. Throughout the different drawings, like reference numbers indicate identical or functionally similar elements. [Figure 1] 1 illustrates the relationship between coverage frequency and range of a wireless node. [Diagram 2] 1 illustrates communication flows between AP MLD and non-AP MLD for multi-link setup, link quality assessment, traffic identifier (TID) to link mapping, and subsequent communication, according to one example. [Diagram 3]1 shows an illustration of an AP MLD having multiple basic service sets (BSSs) and multiple non-AP MLDs within those BSSs, according to various embodiments. [Figure 4] 1 illustrates an illustration of an extended service set (ESS) that includes multiple MLDs, according to various embodiments. [Diagram 5] 1 illustrates the communication flow between AP MLD and non-AP MLD for multi-link discovery, authentication, setup, TID and link mapping, and subsequent communication according to a first embodiment. [Figure 6] 2 shows an illustration of a Multi-link Action frame according to a first embodiment; [Figure 7] 2 shows an illustration of a Multi-link Setup frame according to a first embodiment. [Figure 8] 2 shows an illustration of a Multi-link element according to a first embodiment; [Figure 9] 2 shows an illustration of a Multi-link Teardown frame according to a first embodiment. [Figure 10] 2 shows an illustration of transmit power control (TPC) request elements according to a first embodiment. [Figure 11] 1 shows an illustration of TPC Report elements according to a first embodiment. [Figure 12] 1 shows an illustration of a Multi-link element configured for multi-link authentication according to a first embodiment. [Figure 13] 1 shows an illustration of a Multi-link element configured for a Multi-link setup request according to a first embodiment. [Figure 14A]1 illustrates one variation of a minimum link quality requirement table maintained by an AP MLD according to a first embodiment. [Figure 14B] 1 shows a mapping table between User Priority (UP) and TID defined in the 802.11 specification. [Figure 14C] 1 shows an illustration of a Multi-link element configured for Multi-link setup response and TID-link mapping according to a first embodiment. [Figure 14D] 3 shows a TID map encoding table according to the first embodiment. [Figure 15] 1 illustrates a communication flow between an AP MLD and a non-AP MLD, including a multi-link re-setup request, according to a first embodiment. [Figure 16] 1 shows an illustration of a Multi-link Action frame configured for a Multi-link Setup Response according to a first embodiment. [Figure 17-1] 2 shows a state transition diagram according to the first embodiment; [Figure 17-2] 2 shows a state transition diagram according to the first embodiment; [Figure 18] 4 shows an alternative state transition diagram according to the first embodiment. [Figure 19] 1 shows an illustration of a method for performing link maintenance according to a first embodiment; [Figure 20] 13 illustrates a communication flow between an AP MLD and a non-AP MLD, including a link quality evaluation step, according to a second embodiment. [Figure 21-1] 13 shows an alternative state transition diagram according to the second embodiment. [Figure 21-2] 13 shows an alternative state transition diagram according to the second embodiment. [Figure 22] 13 shows an illustration of a Multi-link element configured for multi-link re-setup request and link deletion according to a second embodiment; [Diagram 23] 1 shows an illustration of a Multi-link Teardown frame according to a second embodiment. [Figure 24] 1 shows an illustration of multi-link setup and link maintenance between AP MLD and non-AP MLD according to various embodiments. [Diagram 25] 2 shows a schematic diagram of an MLD 2500 according to various embodiments. [Figure 26] 26 shows a flowchart 2600 illustrating a method for secure retransmission of multilink, according to various embodiments. [Figure 27] 27 shows a partially boxed schematic diagram of one of the associated STAs 2700 of a multi-link device that may be implemented for multi-link communications, according to various embodiments.

[0010] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following detailed description is merely illustrative and is not intended to limit the embodiments or the application and uses of the embodiments. Moreover, it is not intended to be bound by any theory presented in the preceding Background or Detailed Description sections. Moreover, other desirable features and characteristics will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the background of this disclosure.

[0012] In general, once a multi-link setup between an AP MLD and a non-AP MLD is completed, the link can be in one of the following states: - Setup (or Established): The AP MLD and non-AP MLD have all the information to enable data operations with each other. This state corresponds to state 3 in the state transition diagram of a non-mesh STA, where the IEEE 802.1X controlled port is blocked (i.e. only EAPOL (Extensible Authentication Protocol over LANs) data frames are allowed, and no other data frames are allowed). - Enabled (Activated): Both MLDs have agreed to start data operations on the link, i.e. at least one Traffic Identifier (TID) is mapped to the link and a robust security network association (RSNA) has been completed for the link. This state corresponds to state 4 in the state transition diagram for a non-mesh STA, where the IEEE 802.1X controlled port is unblocked (i.e. all data frames are allowed). - Disabled: In this state, the link may be set up but data operations are disabled, or setup and RSNA are complete but no TID is mapped to the link, or the MLD ignores frames received on the link.

[0013] It is important to clarify how MLD maintains link state and, for each link state, define the rules for what frames are / are not allowed and the associated behavior of MLD.

[0014] Furthermore, different links of MLD may have different range / channel conditions. Referring to FIG. 1 showing the relationship between coverage frequency and range of wireless nodes, 11af coverage (54-698MHz) has a coverage range of 3km or more, cellular coverage (600-900MHz) has a range of 1-3km, 11ah coverage (900MHz) has a range of 1km, 11b / g / n coverage (2.4GHz) has a range of 100m, 11a / ac coverage (5GHz) has a range of 50m, and 11ad coverage (60GHz) has a range of 10m. When a setup frame for multilink setup is exchanged on a link of a lower frequency band (e.g., 2.4GHz band), other links of a higher frequency band (e.g., 5GHz and 6GHz) may not be within range of MLD. Furthermore, even if the MLD is in range for other supported links, some links may be of poor quality, e.g., due to excessive overlapping basic service set (OBSS) interference, frequency dependent fading, or coexistence interference (e.g., due to Bluetooth in the 2.4 GHz band), and therefore may not be suitable for link activation.

[0015] In fact, the link capabilities of a non-AP MLD may not provide enough information to set up a link. Some MLD (potential) links / STAs may be in the fourth state (i.e. not set up (not established / unavailable)) after the completion of the multilink setup procedure. Thus, no frame exchange is possible on that link. However, such a link may become available for setup if conditions change (e.g. a non-MLD moves closer to an AP MLD).

[0016] Therefore, links should not be set up or established based on capability information alone. Non-AP MLD should be allowed to select which links are set up. Also, the channel quality of the links (especially the second and subsequent links) should be checked before establishing / enabling the link (either during the multilink setup itself or during a subsequent activation operation). Furthermore, the channel quality of the enabled links should be checked periodically to ensure that the link is alive and suitable for the TIDs mapped to it.

[0017] Therefore, the present invention seeks to solve the above-mentioned problems.

[0018] FIG. 2 illustrates a communication flow between an AP MLD 202 and a non-AP MLD 204 for multi-link setup, link quality evaluation, traffic identifier (TID) to link mapping, and subsequent communication according to a typical solution for addressing the above-mentioned problems. During multi-link setup, a multi-link setup request 206 is sent from the non-AP MLD 204 to the AP MLD 202 on link 2. The multi-link setup request includes information about the link capabilities of links 1, 2, and 3. In response to this request, the AP MLD 202 sets up the requested links 1, 2, and 3, and then sends a multi-link setup response 208 to the non-AP MLD 204 informing the setup of the links. At 210, the non-AP MLD 204 is authenticated / associated, and now the three links are set up. A multi-link RSNA (4-way handshake / group key handshake) between the AP MLD 202 and the non-AP MLD 204 is then performed on link 2. It will be appreciated that each of links 1, 2, and 3 connects associated STAs of the AP MLD 202 with associated STAs of the non-AP MLD 204, and therefore these STAs may transmit or receive any data or frames on that link.

[0019] After the multi-link setup is completed, the AP MLD 202 can initiate a link quality assessment procedure to check the quality of the set up links, and this assessment can be used to determine the TID-to-link mapping. The AP MLD 202 can send a link measurement request 214 on link 3 and a link measurement request 218 on link 1 for the purpose of assessing the link quality of links other than link 2. In response, the non-AP MLD 204 sends a link measurement report 216 and a link measurement report 220 to the AP MLD 202 through link 3 and link 1, respectively. The link measurement report 216 includes information on the link quality of link 3, and the link measurement report 220 includes information on the link quality of link 1. The link quality assessment may be performed before the multi-link setup.

[0020] The AP MLD 202 may then determine the TIDs to be mapped to each link based on the link quality assessments and initiate TID-link mapping by sending a TID-link mapping request 222 to the non-AP MLD 204 on link 2. The TID-link mapping request includes a TID map indicating how each TID is mapped to each link. In response, the non-AP MLD 204 sends a TID-link mapping response 224 to the AP MLD 202 on link 2 to indicate the status of the TID mapping. After all three links are enabled and the TIDs are mapped to the links (226), frame exchanges may occur on any / all of the three links (228).

[0021] The above solution has several drawbacks, for example, links are set up based solely on capability information (i.e., contained in the multi-link setup request 206). Furthermore, it is an AP-centric solution, i.e., the STAs have no say in which links are set up or enabled.

[0022] During multi-link setup, additional links (i.e., links other than those used in the exchange of Multi-link Setup frames) should not be set up (established) based solely on capability information. The first MLD may request which links are to be set up from the second MLD as part of the multi-link setup, regardless of the link's capabilities, for example, using the Setup Request field of the Multi-link Setup Request frame. The MLD may also include information about the link quality (e.g., uplink / downlink (UL / DL) link margin, UL / DL path loss, etc.) of the requested links. Furthermore, the second MLD sets up only the links requested by the first MLD during multi-link setup (e.g., assigning association identifiers (AIDs), inserting them into association records, etc.). The set up links may be referred to as a multi-link set. The second MLD may also take into account information about link quality to decide whether to set up / enable links, especially if some links have TID restrictions. This information can also be used for subsequent TID-link mapping (i.e., link activation / deactivation).

[0023] 3 shows an illustration 300 of an AP MLD 302 with multiple BSSs and non-AP MLDs 304, 306, 308 within the range of the BSSs, according to various embodiments. The AP MLD 302 can be shown as a schematic diagram 314 including a MAC-Service Access Point (MAC-SAP) for accessing a distribution service (DS), an MLD MAC address that identifies the AP MLD, and three associated APs (i.e., AP1, AP2, and AP3). Each AP has its own STA MAC address at the MAC layer and is connected via a link at the physical layer to transmit and receive data (i.e., AP1 is connected via link 1, AP2 is connected via link 2, and AP3 is connected via link 3).

[0024] Further, the non-AP MLDs 304, 306, 308 may be shown as a schematic diagram 316 including a MAC-SAP for accessing the DS, an MLD MAC address identifying the non-AP MLD, and three associated STAs (i.e., STA1, STA2, and STA3). Each STA has its own STA MAC address at the MAC layer and is connected via a link at the physical layer to transmit and receive data (i.e., STA1 is connected via link 1, STA2 is connected via link 2, and STA3 is connected via link 3).

[0025] The AP MLD 302 sets up multiple (multi-link) BSSs (one BSS per associated AP). Each BSS has its own BSSID, beacon and can have different coverage. For example, AP1 operates a BSS at 6 GHz, AP2 operates a BSS at 5 GHz, and AP3 operates a BSS at 2.4 GHz. The coverage of different APs can be different (due to frequency band, transmit (Tx) power, etc.). The coverage can also depend on the modulation and coding scheme (MCS), i.e. MCS 0 can have much larger coverage compared to MCS 9. Furthermore, a non-AP MLD can be within the range of one or more such BSSs. For example, only STA1 in non-AP MLD 304 is within the coverage of AP MLD 302 via AP1, only STA1 and STA2 in non-AP MLD 308 are within the coverage of AP MLD 302 via AP1 and AP2, and all three STAs in non-AP MLD 306 are within the coverage of AP MLD 302 (i.e., all three APs).

[0026] An AP MLD is an entity with a distribution system access function (DSAF), which allows access to a DS over the wireless medium (WM) for associated non-AP MLDs (with one or more associated STAs) and legacy STAs. Different associated STAs of a non-AP MLD can connect to different APs of an AP MLD to gain access to a DS. However, all APs of an AP MLD can connect to a DS via the same single MAC-SAP and DSAF.

[0027] This network forms an extended service set (ESS) 400 shown in FIG. 4. STA1, STA2, and STA3 belonging to non-AP MLD 1 can, for example, connect to AP1, AP2, and AP3 in AP MLD 1, respectively, to obtain access to the DS. AP1, AP2, and AP3 can obtain access to the DS via the MAC-SAP and DSAF of AP MLD 1. Furthermore, STA4, STA5, and STA6 belonging to non-AP MLD 2 can, for example, connect to AP4, AP5, and AP6 in AP MLD 2, respectively, to obtain access to the DS. AP4, AP5, and AP6 can obtain access to the DS via the MAC-SAP and DSAF of AP MLD 2. Conventionally, a legacy STA such as STA7 obtains access to the DS by associating with an AP, and can continue to access the AP MLD by associating with one of the AP MLD's associated APs (e.g., AP4 in AP MLD 2). However, in the case of non-AP MLD, the association process can be replaced by a multi-link setup procedure, as will be further described below. One or more associated STAs of a non-AP MLD can be provided with access to the DS by the multi-link setup performed between any pair of associated STAs and associated APs.

[0028] FIG. 5 illustrates the communication flow between the AP MLD and the non-AP MLD for multi-link discovery, authentication, setup, TID-link mapping, and subsequent communication according to the first embodiment. Initially, during the multi-link discovery phase, the non-AP MLD 504 checks the quality of links 1, 2, and 3 by sending a probe request frame 506 to the AP MLD 502 on each link. The probe request frame 506 may include a transmit power control (TPC) request element. In response to receiving the probe request frame 506, the AP MLD 502 may send a beacon frame or a probe response frame 508 to the non-AP MLD 504 on each link. The beacon frame or the probe response frame 508 may include the MLD MAC address of the AP MLD 502 and a TPC Report element. After the multi-link discovery phase is completed, the non-AP MLD may be considered to be in state 1.

[0029] After the discovery phase, the non-AP MLD 504 can initiate multi-link authentication by sending an authentication request 510 to the AP MLD 502, for example, on link 2. The authentication request can include information of the MLD MAC address of the non-AP MLD 504. In response to receiving the authentication request 510, the AP MLD 502 can send an authentication response 512 to the non-AP MLD 504 on the same link 2. The authentication response can include information of the MLD MAC address of the AP MLD 502. Multi-link authentication may be optional in an open system using the Extensible Authentication Protocol (EAP), but is mandatory for SAE and Fast Initial link setup (FILS). The MLD MAC address can be used during the authentication process of SAE and FILS. After authentication is successfully completed, the state of the multi-link of the non-AP MLD can change to state 2.

[0030] After authentication is successfully completed, the non-AP MLD 504 can initiate a multi-link setup / association by sending a multi-link setup request 514 to the AP MLD 502, for example, on link 2. The multi-link setup request 514 can include link capabilities of links 1, 2, and 3, and request information identifying associated STAs of the non-AP MLD 504 for which links (i.e., links 1, 2, and 3 in this case) are to be set up. The request information may also include information regarding the quality of the wireless channel for each of links 1, 2, and 3. The request information may further include information regarding expected traffic characteristics for each of links 1, 2, and 3, the traffic characteristics being one of a traffic identifier (TID), payload size, delay bound, data rate, minimum PHY rate, and the like.

[0031] In response to this request, the AP MLD 502 sets up the requested links 1, 2, and 3 based on the request information and sends a multilink setup response 516 to the non-AP MLD 504 informing it of the link setup. At 518, the non-AP MLD 504 is now authenticated / associated and the three requested links are set up. After the setup is successfully completed, the multilink state of the non-AP MLD can change to state 3. A multilink RSNA (4-way handshake / group key handshake) between the AP MLD 502 and the non-AP MLD 504 can then be performed, for example, on link 2.

[0032] After the multilink setup is complete, the AP MLD 502 can initiate TID-link mapping by sending a TID-link mapping request 522 to the non-AP MLD 504, for example, on link 2. The TID-link mapping request 522 can include the requested TID maps for links 1, 2, and 3, indicating how each TID is mapped to each link. In response, the non-AP MLD 504 can send a TID-link mapping response 524 to the AP MLD 502 on link 2 to indicate the status of the TID mapping. After all three links are enabled and the TIDs are mapped to the links (526), ​​frame exchanges can occur on any / all of the three links (528). After the TID-link mapping is complete at 526, the multilink state of the non-AP MLD can change to state 4. TID-link mapping may be optional and initial mapping may be performed as part of the multilink setup step. By default, all TIDs are mapped to all links that are set up.

[0033] It will also be understood that each of links 1, 2, and 3 connects an associated AP of the AP MLD 502 and an associated STA of the non-AP MLD 504, and thus these STAs transmit or receive any data or frames on that link. Prior to sending a setup request 514, the associated STA of the non-AP MLD 504 may be configured to collect information regarding the quality of the wireless channel for each of the one or more links, the quality of the wireless channel including one or more of a link margin, a path loss, a receive signal strength indication (RSSI), and a receive channel power indication (RCPI).

[0034] For the multi-link operation shown in FIG. 5, a new (Class 1) action frame can be defined. FIG. 6 shows an illustration of a new Multi-link Action frame 600 according to a first embodiment. The Multi-link Action frame 600 can include a Frame Control field, a Duration field, three Address fields, a Sequence Control field, an HT Control field, a Category field, a Multi-link Action field, a Variable field, and a Frame Check Sequence (FCS) field. The Multi-link Action field can have a value of 0, indicating that the action frame is for a multi-link setup, or a value of 1, indicating that the action frame is for a multi-link teardown. Values ​​2 to 255 can be reserved.

[0035] 7 shows an illustration of a Multi-link Setup frame 700 according to a first embodiment. The Multi-link Setup frame 700 may include a Frame Control field, a Duration field, three Address fields, a Sequence Control field, an HT Control field, a Category field, a Multi-link Action field set to a value of 0 (i.e., set to Multi-link Setup), a dialog field, a Multi-link element field, one or more Optional element fields, and an FCS field.

[0036] FIG. 8 shows an illustration of a Multi-link element 800 according to the first embodiment. The Multi-link element 800 may include an Element ID field, a Length field, an Element ID Extension field, an Action Type field, an Action Status field, a Multi-link Parameters Control field, and a Multi-link Parameters field. The Multi-link element 800 may be conveyed in a Multi-link action frame 600 or in other frames, such as an Association Request / Response frame or another management frame. Multiple Multi-link elements may be conveyed in the same frame if multiple Multi-link operations (e.g., TID mapping and BA setup, or Multi-link setup and TID mapping) are signaled in the same frame exchange. The operation is signaled by the value indicated in the Action Type field of the Multi-link element 800. A value of 0 may indicate a multilink authentication, a value of 1 may indicate a multilink setup request, a value of 2 may indicate a multilink setup response, a value of 3 may indicate a TID-link mapping request, a value of 4 may indicate a TID-link mapping response, a value of 5 may indicate a Block Ack setup request, and a value of 6 may indicate a Block Ack setup response. Other values ​​7-255 may be reserved.

[0037] 9 shows an illustration of a Multi-link Teardown frame 900 according to a first embodiment. The Multi-link Teardown frame 900 may include a Frame Control field, a Duration field, three Address fields, a Sequence Control field, an HT control field, a Category field, a Multi-link Action field set to a value of 1 (i.e., set to Multi-link Teardown), and an FCS field.

[0038] Alternatively, different Multi-link Action frames and different Multi-link elements can be defined for each category, and in addition, different signaling can be defined for the purpose of adding / removing links (i.e., Multi-link Link Add / Remove Request / Response).

[0039] Referring again to FIG. 5, after discovering the multilink BSS (i.e., through the multilink capability element in the beacon frame), the non-AP MLD 504 can include its transmit power in the probe request frame 506 (i.e., in a modified transmit power control (TPC) request element) transmitted in each multilink BSS (link) so that the AP can calculate the UL path loss. FIG. 10 shows an illustration of a TPC Request element 1000 according to the first embodiment. The TPC Request element 1000 can include an Element ID field, a Length field, and a Transmit Power field. The Transmit Power field can be set to the transmit power used in the host frame (i.e., the probe request frame 506).

[0040] The AP MLD 502 can estimate the UL path loss and UL link margin based on the transmit power indicated in the TPC Request element of the received probe request frame, and includes this information in the probe response frame 508 (i.e., in a modified TPC report element) sent to the non-AP MLD 504 in each multilink BSS. Figure 11 shows an illustration of a TPC Report element 1100 according to the first embodiment. The TPC Report element 1100 can include an Element ID field, a Length field, a Transmit Power field, a Link Margin field, and a Path Loss field. The Transmit Power field can be set to the transmit power used in the host frame (i.e., the probe response frame 508). The link margin is the difference between the receive power (dBm) and the receive sensitivity (dBm). The Link Margin field is coded as a 2s complement signed integer in decibels and may be set to -128 to indicate no link margin. Path Loss is the difference between the transmit power of a frame carrying a TPC Request element, such as a Probe Request frame, and the receive power received from a non-AP MLD. The Path Loss field is coded as a 2s complement signed integer in decibels and may be set to 128 to indicate no path loss. The Link Margin field is set to the UL link margin estimated by the AP MLD 502 and the Path Loss field is set to the UL path loss estimated by the AP MLD 502.

[0041] When the non-AP MLD 504 receives the probe response frame 508, it can use the transmit power information in the TPC Report element to calculate DL path loss, while calculating DL link margin based on the received power. The non-AP MLD 504 can use the link margin and path loss information to estimate the UL / DL link quality of each BSS (link). Alternatively, similar information can be achieved using link measurement request / report frames if these frames are reclassified as class 1 frames for non-directional multi-gigabit (non-DMG) / 11be STAs. Additionally, the AP MLD 502 can also advertise its own MLD MAC address in beacon / probe response frames (e.g., in the multi-link capability element) for use during multi-link authentication (SAE, FILS), multi-link setup. If not advertised, the probe request frame must request to indicate the AP MLD's MAC address. It will be appreciated that although link measurement request / response frames have been mentioned as an alternative, any other suitable management frame may be used for this purpose. Furthermore, the results of the sounding procedure (e.g., Channel Quality Index (CQI)) may also be used if available.

[0042] Upon successful authentication, the legacy STA's state changes to state 2. In the case of MLD, state may be maintained at the MLD level (rather than at the STA level). In the case of open system authentication (e.g., EAP), two authentication frames are exchanged between the two MLDs. Existing authentication steps may be reused or omitted entirely. In the case of SAE (authentication using passwords), four authentication frames are exchanged between the two MLDs, where the MLDs authenticate each other using a shared key (e.g., a password) and generate a pairwise master key (PMK). The MLD MAC address may be used instead of the link MAC address to initialize the STA-A-MAC and STA-B-MAC values ​​used to generate the secret password element (PWE). In the case of FILS authentication, two authentication frames are exchanged between the two MLDs to authenticate each other and generate the PMK. To generate the PMK, the AP-BSSID / STA-MAC may be replaced with the MAC address of the corresponding MLD.

[0043] 5, it is assumed that the non-AP MLD 504 discovers the MLD MAC address of the AP-MLD during multi-link discovery, but the non-AP MLD 504 needs to include its MLD MAC address in the authentication frame / Multi-link Setup frame (e.g., in a Multi-link element) in order for the AP MLD 502 to be able to authenticate the non-AP MLD 504 and to signal the AP MLD 502 to use the MLD MAC address in SAE and FILS authentication. For this purpose, the Multi-link element can be conveyed in the authentication frame (or Multi-link Setup frame). FIG. 12 shows an illustration of a Multi-link element 1200 configured for multi-link authentication according to the first embodiment. The Multi-link element 1200 includes the same fields as the Multi-link element 800. 5, except that the Action Type field is set to a value of 0 indicating multi-link authentication, and the Multi-link Parameters field is set to the MLD MAC address of the non-AP MLD 504. It will be appreciated that multi-link setup request / response frames may be used or authentication frames may be reused. Multi-link authentication is used to establish the identity of one MLD as a member of a set of MLDs that are allowed to associate with another MLD.

[0044] FIG. 13 shows an illustration of a Multi-link element 1300 configured for a Multi-link Setup Request according to the first embodiment. The Action Type field is set to a Multi-link Setup Request (i.e., to a value of 1). The Multi-link Parameters field may further include an MLD MAC Address field, a Multi-link Capabilities field, a Common Information field conveying information common to all links, and one or more Link Information fields (i.e., one Link Information field for each supported link). Each Link Information field may include information specific to the link, such as a Link MAC Address subfield, a Link Capabilities subfield, a Setup Requested subfield, a UL Link Margin subfield, a UL Path Loss subfield, a DL Link Margin subfield, and a DL Path Loss subfield.

[0045] Referring to the multi-link setup of FIG. 5, the non-AP MLD 504 can explicitly request which links to establish by using the Setup Requested subfield of the Multi-link element 1300. For example, a value of 0 indicates that setup is not requested for that link, and a value of 1 indicates that setup is requested. The non-AP MLD 504 can consider link quality information to determine which links to request multi-link setup for. It may also consider other factors, for example, the non-AP MLD 504 may have capability for a 2.4 GHz link (i.e., link 1) but choose not to request setup of this link due to coexistence issues with its Bluetooth radio, or may choose not to request setup of a particular link for power conservation, etc. The non-AP MLD 504 can also include information regarding the link quality of the requested link (e.g., UL / DL link margin obtained at discovery, UL / DL path loss, etc.). If link quality information is not available, the Received Signal Strength Indicator (RSSI) / Received Channel Power Indicator (RCPI) of the beacon / probe response frame received on the link can be included as an estimate of the link quality, or the results of a sounding procedure (e.g., Channel Quality Index (CQI)) can be used as link quality information if available.

[0046] The non-AP MLD 504 may also include fields describing the characteristics and QoS expectations of the traffic flows on the link. Additionally, the link quality information in the UL Link Margin, UL Path Loss, DL Link Margin, and DL Path Loss subfields may be omitted if the link is not required to be set up. Advantageously, this allows the link to be set up based on the non-AP MLD requirements and the link quality.

[0047] When the AP MLD 502 receives a multi-link setup request from a non-AP MLD 504, it performs setup (i.e., AID assignment, insertion into association record, etc.) and subsequent procedures (i.e., TID-link mapping, security key generation / distribution, etc.) of only the link requested by the non-AP MLD 504. The AP MLD 502 can use information about link quality to decide whether to set up / enable the requested link or not, especially if some links have TID restrictions. This information can also be used for subsequent TID-link mapping (i.e., link activation / disabling). The AP MLD 502 can maintain a table of minimum link quality required for a non-AP MLD to use the link.

[0048] FIG. 14A illustrates one variation of the minimum link quality requirement table maintained by the AP MLD according to the first embodiment. FIG. 14A specifies the link quality (in terms of link margin) required to map a TID to a particular link. Different links can have different values. For example, referring to FIG. 14A, the link to which TID 6,7 (AC_VO) is mapped can have a higher link quality requirement to support a higher MCS. The requirement may be different for the uplink (UL) and downlink (DL). FIG. 14B illustrates the mapping of user priority (UP) to TID as specified in the 802.11 specification.

[0049] If traffic flow information (similar to TSPEC elements) is provided, AP MLD can also use this information to decide whether to set up / enable a particular requested link for non-AP MLD. For example, AP MLD can refuse to enable a link with TIDs 6,7 mapped to a non-AP MLD that showed a large amount of traffic flow in TIDs 6,7 in order to maintain QoS requirements on the link. In some cases, AP MLD can set up all requested links and consider link quality only (e.g., during initial or subsequent TID-link mapping) to decide whether to enable the link. In other cases, AP MLD can consider link quality even when setting up requested links.

[0050] AP MLD can include only the information of the set up links in the Multi-link Setup Response frame. Figure 14C shows an illustration of a Multi-link Action frame 1400 configured for Multi-link Setup Response and TID-Link Mapping according to the first embodiment. The Multi-link Action field of the Multi-link Action frame 1400 is set to Multi-link Setup (i.e., to a value of 0). The Multi-link Action frame 1400 further includes two Multi-link elements 1402 and 1404. The Multi-link element 1402 is similar to the Multi-link element 1300, i.e., an action type field set to Multi-link Setup Response, and has one or more link information subfields (one for each set up link). The action type field, Multi-link element 1404, is set to TID-link mapping request (i.e., set to a value of 3) and may contain one or more Link Information fields (one for each link set up) (similar to Multi-link elements 1300 and 1402). However, each of the one or more Link Information fields may contain a Link ID subfield, a UL TID Map, and a DL TID Map. Each TID Map may be a bitmap (i.e., 8 bits, one bit per TID) indicating the TIDs mapped to the link in that direction (UL or DL), or one or more 4-bit fields may be used to indicate the TIDs. An example of the encoding of the TID Map based on a 4-bit field is shown in FIG. 14D and has values ​​from 0 to 15.When the non-AP MLD receives a TID-Link Mapping Request frame from the AP MLD, it can send back a TID-Link Mapping Response frame indicating acceptance of the TID mapping. If the TID mapping is rejected, a default TID mapping can be applied to the link or the AP MLD can disable the link for the non-AP MLD. It will be understood that in the Multi-link Setup Action frame (or Association Response frame), two Multi-link elements can be carried to signal the multi-link setup and the TID-Link mapping, respectively, or may be combined into one element.

[0051] Furthermore, not only can a Multi-link Setup Request / Response frame be used for Multi-link Setup, but also an Association Request / Response frame (including a Multi-link element) can be used for Multi-link Setup. After the Multi-link Setup is successfully completed, one or more non-AP STAs in the non-AP MLD are enabled / allowed to invoke a distribution system service via one or more AP STAs in the AP MLD.

[0052] New MAC sublayer management entity (MLME) primitives for multilink setup can be defined, e.g. for use by non-AP MLD or AP MLD. The MLME primitives are used to pass information between the MLME and the station management entity (SME). The SME uses the services provided by the MLME via the MLME SAP. The primitives for requesting multilink setup for non-AP MLD are: [Table 1]

[0053] In this primitive, a Multi-link Setup Request frame is sent to the peer MLD. PeerMLDAddress is set as the MLD MAC address of the peer MLD, and PeerLinkAddress is set as the MAC address of the associated STA of the peer MLD (for the link on which the Multi-link Setup Request frame is sent). One or more Multi-link elements may be included to carry the information required for the Multi-link Setup Request.

[0054] For non-AP MLD, the primitive to confirm the multi-link setup may be as follows: [Table 2]

[0055] This primitive is generated when a Multilink Setup Response frame is received. PeerMLDAddress is set to the MLD MAC address of the peer MLD. It contains one or more Multi-link elements carried in the Multilink Setup Response frame. The Dialog Token is used to identify the Multilink Setup Request / Response transaction.

[0056] The non-AP MLD indicates that one or more links are available by invoking the MLME-MULTI-LINK-SETUP.confirm primitive. This signals to the supplicant that the MLD's MAC has transitioned to state 3. If the MLD negotiated to use IEEE 802.1X authentication during multi-link setup, the MLD's management entity can respond to the MLME-MULTI-LINK-SETUP.confirm (or indication) primitive by requesting the supplicant (or authenticator) to initiate IEEE 802.1X authentication. In this case, authentication is driven by the non-AP MLD's decision to initiate multi-link setup and the AP MLD's decision to accept multi-link setup.

[0057] For AP MLD, the primitive to indicate receipt of a multilink setup request may be as follows: [Table 3]

[0058] This primitive can be generated upon receiving a Multi-link Setup Request frame. PeerMLDAddress is set to the MLD MAC address of the peer MLD. It contains one or more Multi-link elements carried in the Multi-link Setup Request frame.

[0059] For AP MLD, the primitives for responding to a multilink setup request may be as follows: [Table 4]

[0060] In this primitive, a Multilink Setup Response frame is sent to the peer MLD. PeerMLDAddress is set as the MLD MAC address of the non-AP MLD, and PeerLinkAddress is set as the MAC address of the associated STA of the peer MLD (for the link on which the Multilink Setup Response frame is sent). One or more Multi-link elements may be included to carry the information required for the Multilink Setup Response.

[0061] Furthermore, the primitives requesting multilink teardown (for both non-AP MLD and AP MLD) can be as follows: [Table 5]

[0062] This primitive sends a Multi-link Teardown frame. PeerMLDAddress is set to the MLD MAC address of the peer MLD. Optionally, one or more Link IDs may be included, each identifying a link to be torn down.

[0063] The non-AP MLD can request to add a new link by re-performing multi-link setup. Link quality, traffic flow information can also be included. FIG. 15 shows a diagram 1500 of communication flow between an AP MLD 1502 and a non-AP MLD 1504, including a multi-link re-setup request, according to a first embodiment. During multi-link setup, the AP MLD 1502 rejects the setup of link 3 due to poor link quality. Thus, only links 1 and 2 are enabled. The non-AP MLD 1504 can then request the setup of link 3 by sending a multi-link setup request 1506 including request information to the AP MLD 1502, for example, because the link quality of link 3 has improved. The request information can include link capabilities, information identifying link 3, and link quality of link 3. Based on the request information, the AP MLD 1502 sets up the requested link and sends a multi-link setup response 1508 to the non-AP MLD 1504, including the information of the set up link (i.e., link 3) and the TID map of link 3. No authentication by the IEEE 802.1X server, PMKSA configuration, etc. is performed. Advantageously, this allows for the flexibility of adding new links with improved link quality.

[0064] Since the non-AP MLD 1504 is assumed to have already been authenticated and associated with the AP MLD 1502 during the initial multilink setup, the AP MLD 1504 only performs procedures related to the requested addition of the new link (e.g., AID assignment for the new link, updating the link MAC address to the association record, TID-link mapping, etc.). It may also generate / distribute security keys for the new link (i.e., Pairwise Temporal Key (PTK), Group Temporal Key (GTK) / (Integrity) Group Temporal Key (IGTK)) if necessary. If the same PTK is used for all enabled links, no 4-way handshake is required for the new link. If different GTKs / IGTKs are used for the new link, they can be distributed using the group key handshake. Alternatively, instead of reusing the multilink setup, a separate signaling (e.g., Multilink Link Addition Request / Response) may be defined for this purpose.

[0065] When adding a new link, some parameters of existing Block ACK agreements for the TIDs mapped to the new link may need to be modified. For existing Block ACK agreements originating from the AP MLD (i.e., in DL flows), the AP MLD may also include the relevant Block ACK parameters in the same frame that carries the Multilink Setup Response. A non-AP MLD may also follow suit by initiating an update of the Block ACK parameters covering the TIDs mapped to the new link for UL flows (piggybacked in an Add Block Acknowledgement (ADDBA) Request frame or in another frame such as a TID-Link Mapping Response frame).

[0066] FIG. 16 shows an illustration of a Multi-link Action frame 1600 configured for a Multi-link Setup Response to add a new link according to the first embodiment. Similar to the Multi-link Action frame 1400, the Multi-link Action frame 1600 further includes a Multi-link Element (Block ACK Setup Request) field 1602. The Multi-link Element field 1602 can include one or more Link Information fields, each of which includes a Link ID field and one or more TID Information fields. Furthermore, the one or more TID Information fields can include a TID subfield, a Scoreboard Size subfield, and a Starting Sequence Number subfield. The associated Block ACK parameters for the new link can thus be included in the Multi-link Element field 1602.

[0067] The non-AP MLD that receives the Multi-link Action frame 1600 may send a TID-Link Mapping Response frame to the sending AP MLD in response to the TID-Link Mapping Request 1604. The TID-Link Mapping Response frame may be a Multi-link Action frame carrying a Multi-link element with the action type set to TID-Link Mapping Response.

[0068] Dynamically enabling / disabling links (using TID-link mapping) may affect Block ACK parameters (e.g. receive reordering buffer size, unified BA scoreboard size, etc.) and may trigger ADDBA renegotiations on each link enable / disable. For example, if a new link is added, the BA scoreboard size, starting sequence number, etc. must be specified for the new link. Also, the receiving MLD may need to increase the size of its receive (RX) reordering buffer to be able to receive additional frames from the added link.

[0069] FIG. 17 shows a state transition diagram 1700 according to the first embodiment. The MLD can maintain an enumerated state variable (instead of maintaining state between two associated STAs) for each MLD that needs to communicate directly through the WM over one or more links. For example, based on the state transition diagram 1700, each MLD is in one of four states: state 1 (unauthenticated, unassociated), state 2 (authenticated, unassociated), state 3 (authenticated, associated, waiting for RSNA authentication), and state 4 (authenticated, associated, RSNA established or not required). If authentication is successful, the state of the MLD changes from "state 1" to "state 2". If multilink setup (at least one link is requested) is successful, the state of the MLD changes from state 2 to state 3. During multilink setup, security parameters are verified. MLDs that perform IEEE 802.1X authentication use open system authentication. MLDs that perform password-based authentication can use SAE authentication. MLDs that perform FILS use FILS authentication. SAE and FILS authentication provide mutual authentication and derivation of the PMK. If open system authentication is selected instead, either the authenticator or the supplicant initiates IEEE 802.1X authentication. Before IEEE 802.1X authentication and key installation are complete, IEEE 802.1X controlled ports in AP MLD block all data frames. IEEE 802.1X non-controlled ports allow IEEE 802.1X frames to pass between the supplicant and the authenticator. The authentication process creates an encryption key that is shared between the cryptographic endpoints, whether SAE or FILS authentication uses authentication frames, or IEEE 802.1X authentication uses Data frames post association. The cryptographic endpoints are the AP MLD and non-AP MLD when SAE / FILS is used, and the IEEE 802.1X AS (Authentication Server) and non-AP MLD when IEEE Std 802.1X is used.When using IEEE Std 802.1X, the AS forwards these keys to the AP MLD, and the AP MLD and non-AP MLD complete the establishment of the security association using one of the key confirmation handshakes (e.g., 4-way handshake over one of the links or FT 4-way handshake). When using SAE authentication, there is no AS, and therefore no key transfer takes place. The 4-way handshake is performed directly between the AP MLD and the non-AP MLD. The key confirmation handshake indicates that the link is secured by the keys and is ready to allow normal data traffic and protected robust management frames. When FILS authentication is performed, the key confirmation is performed as part of the FILS exchange using the association frame; therefore, no additional handshake is required. If the key confirmation handshake has been completed for at least one link, the IEEE 802.1X controlled port is considered unblocked for non-AP MLD. After multilink teardown, the IEEE 802.1X controlled port returns to the unauthorized state and blocks all data frames.

[0070] Additionally, a link state is maintained for each (pair of associated STAs) / link, which can be in one of four states: - Not Setup (not established / unavailable): The AP MLD and the non-AP MLD do not have all the information to allow data operations with each other. The frames allowed depend on the state of the MLD. No data frames are allowed. No access to the DS is allowed. - Setup (Established): The AP MLD and non-AP MLD have all the information to enable data operations with each other. No data frames (except EAPOL frames) are allowed. No access to the DS is allowed. - Enabled (Activated): Both MLDs agree to start data operations on the link. For example, at least one TID is mapped to the link and a security association (RSNA) is completed for the link. All frames allowed by the TID mapping are allowed. Access to the DS is allowed. - Disabled (Deactivated): No data frames (except EAPOL frames) are allowed. Non-data frames may be allowed. No access to the DS is allowed.

[0071] For legacy or non-MLD STAs, the normal authentication / association process can be used and state is maintained at the STA level. A multilink setup between a MLD pair creates a unique pair of IEEE 802.1X ports and authentication is done only for these ports. Essentially, in the MLD case, the authenticator and supplicant roles can be implemented at the MLD level instead of at the STA level.

[0072] When a STA / link is in Not Setup state, no data frames other than EAPOL are allowed for that link even if the IEEE 802.1X controlled port is unblocked at the MLD level. A successful multilink setup (link is requested) changes the link state from Not Setup to Setup. A successful 4-way / group key handshake + TID-link mapping (at least one TID is mapped to the link) changes the link state from Setup to Enabled. A successful TID-to-link mapping switches the state between Enabled and Disabled. A multilink teardown causes the MLD state to state 1 and all associated STAs / links to go to Not Setup state. Additionally, security keys may not be generated for a STA / link in Setup state while no TID is mapped to the STA / link in both Setup and Disabled states. On the other hand, in the Disabled state, a security key is generated for the STA / link, but in either state no TID is mapped to the link, and the AP cannot forward data frames from the link to the downstream even if the IEEE 802.1X controlled port is unblocked.

[0073] FIG. 18 shows an alternative state transition diagram according to the first embodiment, in which a link can be in one of four states: Setup state (MLD authenticated, associated, waiting for RSNA authentication, IEEE 802.1X controlled port blocked), Enabled state (authenticated, associated, RSNA established or not required, IEEE 802.1X controlled port unblocked, at least one TID mapped to the link), Disabled state (MLD authenticated, associated, IEEE 802.1X controlled port unblocked, no TID mapped to the link), and Not Setup state. The Not Setup state includes three sub-states depending on the state of the MLD: Not Setup-1 (MLD is in state 1, only class 1 frames are allowed), Not Setup-2 (MLD is in state 2, only class 1 and class 2 frames are allowed), Not Setup-3 (MLD is in state 3, class 1, 2 and 3 frames are allowed, but no data frames other than EAPOL are allowed on the link even if the IEEE 802.1X controlled port is unblocked at the MLD level).

[0074] According to the first embodiment, the MLD can also maintain a record of the link quality of all active links based on link quality measurements such as signal noise ratio (SNR), packet error ratio (PER), RSSI, etc. Figure 19 shows an illustration of how link maintenance is performed according to the first embodiment. For links with active transmission, the link quality can be measured based on frames transmitted / received. For inactive links (Awake Power Save state), management frames (i.e., solicited / unsolicited link measurement frames) can be sent periodically (i.e., once every beacon interval) to access the link quality. If the link quality falls below a certain threshold, the link can be considered "Down". Data frames may not be allowed on a "Down" link or may be sent with a lower MCS. The threshold can depend on the TID mapped to the link, the MCS requirements of the link, etc. On the other hand, if the link quality improves above the threshold, the link can be used again as a normal active link. However, if the link quality remains below a threshold for a certain TIMEOUT period, the link can be disabled (by the TID-link mapping), which advantageously allows links to be set up based on link quality.

[0075] According to the second embodiment, the non-AP MLD can implicitly signal the links to be set up during the multi-link setup by including only the information of the links it requests to set up (i.e., link capabilities, MAC addresses, etc.). Information of the links that it does not request to set up is not included in the multi-link setup request. For example, the setup request can include information indicating the capability information and MAC addresses of only the associated STAs of the non-AP MLD for which the link is to be set up. This can be used as a default option for requesting to set up a link. Alternatively, a request to not set up a link is implicitly signaled by providing link information but setting a very low link quality value (i.e., setting the path loss of the link to a maximum value (e.g., 128) or setting the link margin to a minimum value (e.g., -128) for either or both UL / DL). For example, the setup request can include information regarding the quality of the radio channels of the multiple links that can be set up between the first and second multiple STAs, and the quality of the radio channels is set to implicitly indicate the link or links to be set up. Alternatively, as described in the previous embodiment, an explicit request to set up the link can be provided in a Multi-link Setup frame.

[0076] If link quality information is not included in the multi-link setup request, the AP MLD can initiate link quality evaluation of the requested links, including / excluding the link on which the multi-link request was received, before sending the multi-link setup response, to determine whether to set up the links. Figure 20 shows a communication flow 2000 between the AP MLD 2002 and the non-AP MLD 2004, including a link quality evaluation step, according to a second embodiment. After the non-AP MLD 2004 initiates multi-link setup by sending a multi-link request to the AP MLD on link 2 to request the setup of links 1, 2, and 3, the AP MLD 2002 initiates link quality evaluation by sending link measurement requests 2006 and 2010 on links 3 and 1, respectively (before sending the multi-link setup response). In this example, the link quality evaluation of the requested links excludes the link on which the multi-link request was received (i.e., link 2), but the AP MLD may choose to include that link as well. In response to the link measurement request, the non-AP MLD 2004 sends a link measurement report 2008 on link 3 (in response to the link measurement request 2006) and a link measurement report 2012 on link 1 (in response to the link measurement request 2010) to the AP MLD 2002. The AP MLD decides (at 2014) to set up / establish only links 1 and 2 based on the collected link quality information provided by the link measurement reports 2008 and 2012. Link 3 is rejected. Thus, the AP MLD 2002 sends a multi-link setup response indicating that links 1 and 2 are set up.

[0077] The AP MLD 2002 can use information about link quality to decide whether to set up / enable the requested links, especially if some links have TID limitations. However, the link quality assessment needs to be done so that the multi-link setup can be performed within the timeout values ​​associated with the setup. Furthermore, while the example shown in Figure 20 shows the use of link measurement request / response frames, it will be appreciated that any other suitable management frames can be used for this purpose.

[0078] FIG. 21 shows an alternative state transition diagram 2100 according to the second embodiment. In the state transition diagram 2100, alternative states of the MLD are assumed, and these states are maintained at each associated STA level of the MLD, similar to the legacy STA. Also, the authenticator and supplicant roles are implemented at the STA level (rather than at the MLD level). This version of the state machine allows for SAE and FILS authentication, i.e., IEEE 802.1X authentication is not used. At the same time, the link maintains its state, which is the same as in the first embodiment.

[0079] For example, STA1 and STA2 are both in state 1 (unauthenticated, unassociated class 1 frames, link not set up) at 2102. When a STA / link is in Not Setup state, data frames are not allowed on that link. A successful (multi-link) authentication puts all associated STAs (i.e., STA1 and STA2) in state 2 at 2104. However, the states of excluded associated STAs remain in state 1. A successful multi-link setup (where a link is requested) changes the state of the link from Not Setup to Setup and the state of the corresponding associated STAs to state 3. The unrequested link remains in Not Setup state and the state of the corresponding associated STAs remains in state 1 or state 2. For example, after a successful multi-link setup where link 1 (corresponding to STA1) is requested, STA1 is in state 3 and STA2 is still in state 2 at 2106. If the 4-way / group key handshake+TID-link mapping (at least one TID is mapped to the link) is successful, the state of the link changes from Setup to Enabled, and the state of the corresponding associated STAs changes to state 4. For example, at 2108 after the 4-way / group key handshake+TID-link mapping (one or more TIDs are mapped to link 1) is successful from 2106, STA1 is in state 4 and link 1 is enabled, while STA2 is still in state 2 and link 2 has not yet been set up. If the multi-link re-setup, in which link 2 is required, is successful, at 2110, STA2 goes from state 2 to state 3 (i.e., link 2 is set up). If the TID-link mapping is successful, the state of the link switches between Enabled and Disabled, but the state of the associated STAs does not change.For example, after (from 2110) successful TID-link mapping (one or more TIDs are mapped to link 2, but no TIDs are mapped to link 1) and a successful 4-way / group key handshake for link 2, STA1 is in state 4 even though link 1 is disabled, and STA2 is in state 4 and link 2 is enabled, at 2114. Alternatively, these state changes may also occur after a successful multi-link re-setup from 2108 (i.e., link 2 is requested), successful TID-link mapping (one or more TIDs are mapped to link 2, but no TIDs are mapped to link 1), and a successful 4-way / group key handshake for link 2, at 2114. Furthermore, after (from 2114) successful TID-link mapping (one or more TIDs are mapped to link 1, but no TIDs are mapped to link 2), STA1 and STA2 are both in state 4, link 2 is enabled, and link 1 is disabled, at 2116. It is also possible to return from 2116 to 2114 due to successful TID-link mapping where one or more TIDs are mapped to link 2 but no TIDs are mapped to link 1. Furthermore, a multi-link teardown will cause the state of all associated STAs to go to state 1 and all links to go to the Not Setup state, i.e., return to 2102.

[0080] In this example, the difference between Setup and Disabled is that in neither case is the TID mapped to the link. In the Setup state, security keys may not be generated for the STA / link, but in the Disabled state, security keys are generated for the STA / link. However, in neither state is the TID mapped to the link, and the AP cannot forward data frames from the link to the DS.

[0081] According to a second embodiment, the non-AP MLD may request which links to delete as part of the multi-link setup (i.e. explicitly by using the Deletion Requested field of the Multi-link Setup Request element, or implicitly by indicating poor channel quality). The non-AP MLD may also include information about the link quality of the link it requests to delete (i.e. UL / DL link margin obtained during discovery, UL / DL path loss, etc.). If link quality information is not available, the RSSI / RCPI of the beacon / probe response frame received on the link may be included as an estimate of the link quality. The non-AP MLD may take into account the link quality information to decide which links to request deletion of. It may also take into account other factors. For example, the non-AP MLD may choose to request deletion of the 2.4 GHz link due to coexistence issues with its own Bluetooth radio, etc., or may choose not to request deletion of certain links due to power savings, etc. Advantageously, this allows links to be set up based on the non-AP MLD's request and link quality.

[0082] FIG. 22 shows an illustration of a Multi-link element 2200 configured for the Multi-link Re-Setup Request and Link Deletion described above. The Action Type field of the Multi-link element 2200 is set to Multi-link Setup Request. There may be one or more Link Information fields, such that there is one Link Information field for each link to be established. Each Link Information field may include a Link ID subfield, a Link MAC Address subfield, a Deletion Requested subfield, a UL Link Margin subfield, a UL Path Loss subfield, a DL Link Margin subfield, and a DL Path Loss subfield. The Deletion Requested subfield may be used to indicate whether deletion is requested for the link (i.e., value 0=not requested, value 1=requested). For example, the link is deleted from the multilink set if the value of the Deletion Requested subfield is 1. Link quality information that may be included in the UL Link Margin subfield, UL Path Loss subfield, DL Link Margin subfield, and DL Path Loss subfield is optional.

[0083] Alternatively, a Multi-link Teardown frame can be used for link removal. Referring to FIG. 23, which shows a Multi-link Teardown frame 2300, the Multi-link Action field is set to Multi-link Teardown (i.e., to a value of 1). There can be one or more Link ID fields, such that there is one Link ID field for each link that is established.

[0084] Removing a link transitions the link state to Not Setup. If connectivity state is maintained for each associated STA, the state of the corresponding STA also changes to state 1 (unauthenticated, not associated). As long as one link is in a state other than Not Setup, two corresponding MLDs are considered connected. When all links are torn down, the MLD is no longer connected and if state is maintained at the MLD level, the MLD state changes to state 1.

[0085] According to the third embodiment, the AP MLD can restrict frame exchange for multi-link setup to one of the links (i.e., the link with the highest frequency band (e.g., 6 GHz)) to ensure that the non-AP MLD is in range on all links. For example, whether frame exchange for multi-link setup is allowed or not on a link can be signaled during the discovery phase (e.g., in a beacon / probe response frame transmitted on the link, or in a (shortened) neighbor report element transmitted on the other link, etc.). Alternatively, the AP MLD can try to make the BSSs of all its associated APs have approximately the same coverage range by controlling the transmission power of each associated AP. However, in this case, the transmission power of an AP associated with a BSS in a lower frequency band (e.g., 2.4 GHz band) may be significantly lower than the transmission power of an AP associated with a BSS in a higher frequency band (e.g., 5 / 6 GHz). Thus, these measures can mitigate the range difference problem, but may not mitigate other link quality problems.

[0086] FIG. 24 shows a diagram 2400 of multi-link setup and link maintenance between AP MLD and non-AP MLD. According to an example, in step 2402, both MLDs are operational on links 1, 2, and 3. Before initiating multi-link setup, the non-AP MLD STA can listen to beacons (passive scan) or perform active scan (exchanging probe request / response frames) on all three links to measure the quality of the links. The non-AP MLD is authenticated by the AP MLD by exchanging authentication frames or multi-link setup (authentication) frames on one of the links (i.e., link 3). At this stage, these MLDs are in state 2. The non-AP MLD initiates a multi-link setup request, requesting to set up links 2 and 3 by sending a Multi-link Setup Request frame on link 3. Link 1 is excluded from the request due to poor channel quality. The non-AP MLD can also include link quality information of links 2 and 3.

[0087] The AP MLD considers setting up Link 2 and Link 3, and decides to set up both links. The AP MLD sends a multilink setup response frame indicating that Link 2 and Link 3 have been set up. At this stage, the multilink set consists of Link 2 and Link 3. In this example, the AP uses the default TID-link mapping for all links, so the multilink setup response frame does not include TID-link mapping information. Therefore, in step 2404, the AP MLD and the non-AP MLD are associated, and the AP MLD records the relevant information of the non-AP MLD and the relevant information of Link 2 and Link 3. The information of Link 1 is not recorded. At this stage, these MLDs are in state 3, but the IEEE 802.1X controlled ports are still blocked. Immediately after, IEEE 802.1X authentication is performed, and security keys for Link 2 and Link 3 are generated and distributed to the non-AP MLD. At this stage, these MLDs are in state 4, and the IEEE 802.1X controlled ports are unblocked. Link 2 and Link 3 are considered Enabled at this stage, while Link 1 remains in a Not Setup state. At this stage, data and non-data frames can be exchanged over Link 2 and Link 3.

[0088] After some time, the AP MLD notices that the link quality of Link 2 has fallen below the AP's required quality threshold for this link. The AP continues to monitor the link and decides that since the link quality has been below the required threshold for a period longer than a certain TIMEOUT period, it should disable the link by performing TID-Link mapping that does not map any TID to Link 2. This causes Link 2 to go into the Disabled state in step 2406 and all traffic is diverted to Link 3.

[0089] After that, both AP MLD and non-AP MLD continue to monitor the links, and after some time, the link quality of both Link 1 and Link 2 improves until it is above the required threshold. At this stage, either MLD (e.g., non-AP MLD) requests to set up Link 1 (i.e., add Link 1 to the multi-link set) by sending a Multi-link Setup Request frame. The AP MLD accepts this request, and Link 1 is added to the multi-link set. At the same time, the AP MLD maps TID6 and TID7 to both Link 1 and Link 2, which causes both Link 1 and Link 2 to transition to the Enabled state in step 2408. At this stage, data and non-data frames can be exchanged on Link 1, Link 2, and Link 3.

[0090] According to another example, if the state is maintained at the STA level, multi-link operation is possible with minor modifications. For example, in step 2402, the associated STAs are in state 2 instead of the corresponding MLD. The non-AP MLD only requires link 2 and link 3 to be enabled, but includes information (i.e., capability information) for all three links.

[0091] The AP MLD considers setting up all three links and decides to set up all three links. Therefore, the AP MLD sends a Multilink Setup Response frame indicating that links 1, 2, and 3 have been set up. At this stage, the multilink set consists of links 1, 2, and 3. However, the Multilink Setup Response frame contains a TID-Link Mapping element that maps all TIDs to only links 2 and 3, with no TIDs mapped to link 1. In this case, in step 2404, all three associated STAs are considered associated (i.e., in state 3), but only links 2 and 3 are in the Enabled state, and link 1 is in the Setup state. The parameters of all links (1-3) are recorded by the AP MLD, and all conventional procedures related to association (e.g., AID assignment) are performed for all links. However, secret key generation / distribution is performed only for the Enabled links. Alternatively, only associated STAs corresponding to Enabled links can be considered associated (i.e., state 3), and associated STAs corresponding to other links can not be considered associated (i.e., state 1 or state 2). Parameters of all links (1-3) are recorded by AP MLD, but all traditional procedures related to association (e.g., AID assignment) and secret key generation / distribution are performed only for Enabled links.

[0092] After some time, the AP MLD notices that the link quality of Link 2 has fallen below the AP's required quality threshold for this link. The AP continues to monitor the link, and since the link quality continues to be below the required threshold for a period longer than a certain TIMEOUT period, the AP decides to disable this link by performing TID-link mapping that does not map any TID to Link 2. This causes Link 2 to go into Disabled state in step 2406, and all traffic is diverted to Link 3.

[0093] In addition to step 2408 described in the previous example, the first time the AP MLD receives a request to activate a link, it may also perform association related procedures (such as AID assignment) and secret key distribution if not done in step 2404. Subsequent activations / deactivations do not require this procedure and can be done via TID-link mapping.

[0094] 25 shows a schematic diagram of an MLD 2500 according to various embodiments. The MLD 2500 includes a MAC-SAP 2502 for accessing a distribution service (DS) via controlled and uncontrolled ports, optional IEEE 802.1X port controlled and uncontrolled filtering, a link activity monitoring module 2504, a link quality assessment module 2506, and a link state module 2508. The MLD 2500 also includes three associated STAs or stations, namely, STA1 2510a, STA2 2510b, and STA3 2510c. Each STA has a MAC layer and a physical layer, from which transmissions are made via link 1 (for STA1 2510a), link 2 (for STA2 2510b), and link 3 (for STA3 2510c). It will be appreciated that the MLD 2500 may be an AP MLD (STA1-3 are associated APs) or a non-AP MLD (STA1-3 are associated non-AP STAs), and the number of links and associated STAs or stations may be further expanded.

[0095] 26 shows a flowchart 2600 illustrating a method of communication according to various embodiments. In step 2602, a request frame is generated at a first STA included in a first plurality of STAs belonging to a first MLD, the request frame including request information. In step 2604, the request frame is sent to a second STA, the second STA included in the second plurality of STAs belonging to a second MLD, to request a multi-link setup, the multi-link setup establishing one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information.

[0096] 27 shows a partially boxed schematic diagram of a STA 2700 that may be implemented for multi-link setup and link maintenance according to the first to third embodiments. The STA 2700 may be implemented as a STA or AP included in multiple STAs or APs that belong to an AP MLD or a non-AP MLD according to various embodiments.

[0097] The various functions and operations of the STA 2700 are arranged in layers according to a hierarchical model, where lower layers report to and receive instructions from higher layers, in accordance with the IEEE specification, and for the sake of brevity, the details of the hierarchical model are not described in this disclosure.

[0098] As shown in FIG. 27, the STA 2700 may include a circuit 2714, at least one wireless transmitter 2702, at least one wireless receiver 2704, and multiple antennas 2712 (only one antenna is depicted in FIG. 27 for purposes of illustration for simplicity). The circuit may include at least one controller 2706, which is used when performing the tasks it is designed to perform with the aid of software and hardware, including controlling communications with one or more other multi-link devices in a MIMO wireless network. The at least one controller 2706 may control at least one transmit signal generator 2708 for generating Multi-link Action frames to be transmitted via the at least one wireless transmitter 2702 to one or more other STAs or MLDs, and at least one receive signal processor 2710 for processing Multi-link Action frames received via the at least one wireless receiver 2704 from one or more other STAs or MLDs. At least one transmit signal generator 2708 and at least one receive signal processor 2710 may be standalone modules of the STA 2700 that communicate with at least one controller 2706 for the above-mentioned functions. Alternatively, at least one transmit signal generator 2708 and at least one receive signal processor 2710 may be included in at least one controller 2706. It will be understood by those skilled in the art that the arrangement of these functional modules is flexible and may vary according to actual needs and / or requirements. The data processing device, storage device, and other related control devices may be provided on an appropriate circuit board and / or chipset.

[0099] In various embodiments, in operation, the at least one wireless transmitter 2702, the at least one wireless receiver 2704, and the at least one antenna 2712 may be controlled by at least one controller 2706. Further, while only one wireless transmitter 2702 is shown, it will be understood that there may be multiple such transmitters.

[0100] In various embodiments, in operation, the at least one wireless receiver 2704 together with the at least one receive signal processor 2710 form a receiver for the STA 2700. In operation, the receiver for the STA 2700 provides the functionality necessary for multi-link communication. Although only one wireless receiver 2704 is shown, it will be understood that there may be multiple such receivers.

[0101] In operation, the STA 2700 provides functions necessary for multi-link setup and link maintenance. The STA 2700 may be, for example, a first STA included in a first plurality of STAs belonging to a first MLD. In operation, the circuit 2714 may generate a request frame, the request frame including request information. In operation, the wireless transmitter 2702 may transmit the request frame to a second STA to request a multi-link setup, the second STA being included in a second plurality of STAs belonging to a second MLD, and the multi-link setup establishes one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information.

[0102] The request information may identify one or more STAs of the first plurality of STAs. The request frame may further include information regarding a quality of a wireless channel of each of the one or more links. The first plurality of STAs may be configured to collect information regarding a quality of a wireless channel of each of the one or more links before transmitting the request frame, the quality of the wireless channel including one or more of a link margin, a path loss, a received signal strength indicator (RSSI), and a received channel power indicator (RCPI). The request information may further include information regarding a quality of a wireless channel of a plurality of links that may be set up between the first plurality of STAs and the second plurality of STAs, the quality of the wireless channel being set to implicitly indicate the one or more links to be set up. The first MLD may be a non-AP MLD, and the second MLD may be an AP MLD.

[0103] For example, the STA 2700 may be a second STA included in a second plurality of STAs belonging to a second multi-link device (MLD). In operation, the wireless receiver 2704 can receive a request frame from a first STA, the first STA being included in the first plurality of STAs belonging to the first MLD, the request frame including request information, and requesting a multi-link setup to establish one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information. The wireless transmitter 2702 can transmit a response frame to the first STA to notify the result of the multi-link setup, the response frame carrying information of one or more links established between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs.

[0104] The request information may identify one or more STAs of the first plurality of STAs. The information of the one or more links may include operation parameters of the one or more links and capability information of one or more STAs of the second plurality of STAs corresponding to the one or more links. The response frame may further include information of a traffic identifier (TID) mapped to each of the one or more links, and the first plurality of STAs is permitted to transmit, on each link, only frames belonging to the one or more TIDs mapped to the link. The request information may include information on a quality of a wireless channel of the one or more links, and the second MLD is configured to determine whether to establish the one or more links based on the information. The response frame may further include information related to a block ACK parameter of the established link. The second MLD may be an AP MLD, and the first MLD may be a non-AP MLD, and the STAs included in the second plurality of STAs may transmit a frame including information of a common MAC address identifying the AP MLD to advertise the AP MLD, and the frame is one of a beacon frame or a probe response frame. To advertise the AP MLD, a STA included in the second plurality of STAs can transmit a frame indicating an AP among the second plurality of STAs to which the request frame is addressed, the frame being one of a beacon frame or a probe response frame.

[0105] The present disclosure can be realized by software, hardware, or software cooperating with hardware. Each functional block used in the description of each embodiment above can be realized in part or in whole by an LSI such as an integrated circuit, and each process described in each embodiment can be controlled in part or in whole by the same LSI or a combination of LSIs. The LSI may be formed as an individual chip, or a single chip may be formed to include some or all of the functional blocks. The LSI may include a data input / output unit coupled to it. The LSI referred to here may be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. However, the technology for implementing the integrated circuit is not limited to the LSI, and may be realized using a dedicated circuit, a general-purpose processor, or a special-purpose processor. Furthermore, a field programmable gate array (FPGA) that can be programmed after the manufacture of the LSI, or a reconfigurable processor that can change the connection and settings of the circuit cells arranged inside the LSI may be used. The present disclosure can be realized as digital processing or analog processing. If future integrated circuit technology replaces LSI due to advances in semiconductor technology and other derived technologies, it may be possible to integrate functional blocks using that future integrated circuit technology. Biotechnology can also be applied.

[0106] The present disclosure may be implemented by any type of apparatus, device, or system having communication capabilities, referred to as a communications device.

[0107] A communication device may include a transceiver and a processing / control circuit. The transceiver may include a receiver and a transmitter and / or function as a receiver and a transmitter. The transceiver as a transmitter and a receiver may include an RF (radio frequency) module including an amplifier, an RF modulator / demodulator, etc., and one or more antennas.

[0108] Some non-limiting examples of such communications devices include phones (e.g., cellular phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), gaming consoles, e-book readers, telemedicine equipment, vehicles providing communications capabilities (e.g., automobiles, airplanes, ships), and various combinations thereof.

[0109] The communications devices are not limited to being portable or mobile, but may also include any type of apparatus, device, or system that is non-portable or stationary, such as smart home devices (e.g., appliances, lights, smart meters, control panels), vending machines, and any other "things" in the Internet of Things (IoT) network.

[0110] Communications may include, for example, exchanging data through cellular systems, wireless LAN systems, satellite systems, and various combinations thereof.

[0111] The communications device may include devices such as controllers and sensors coupled to the communications apparatus to perform the communications functions described in this disclosure. For example, the communications device may include a controller or sensor that generates control or data signals used by the communications apparatus to perform the communications functions of the communications device.

[0112] The communications device may further include infrastructure facilities, such as base stations, access points, and any other apparatus, devices, or systems that communicate with or control apparatuses such as the apparatuses in the non-limiting examples above.

[0113] A non-limiting example of a station may be a station included in a first plurality of stations belonging to a multi-link station logical entity (i.e., MLD, etc.), where as part of the first plurality of stations belonging to the multi-link station logical entity, the stations of the first plurality of stations share a common Medium Access Control (MAC) data service interface to higher layers, where the common MAC data service interface is associated with a common MAC address or traffic identifier (TID).

[0114] It can therefore be seen that embodiments of the present disclosure provide communication devices and methods operating on multiple links to fully realize the throughput gains of multi-link communication, particularly in multi-link secure retransmission.

[0115] In the above detailed description of the present embodiment, an exemplary embodiment has been presented, but it should be understood that a vast number of variations exist. Furthermore, it should be understood that the exemplary embodiment is an example, and is not intended to limit the scope, applicability, operation, or configuration of the present disclosure in any way. Rather, the above detailed description provides those skilled in the art with a convenient guide for implementing the exemplary embodiment. It should be understood that various changes can be made in the function and organization of the steps and methods of operation described in the exemplary embodiment, and in the modules and structures of the devices described in the exemplary embodiment, without departing from the scope of the subject matter described in the appended claims.

[0116] According to one example, there is a second STA included in a second plurality of STAs belonging to a second multi-link device (MLD), and the second STA includes: a receiver that, in operation, receives a request frame from a first STA, where the first STA is included in the first plurality of STAs belonging to the first MLD, the request frame including request information, and based on the request information, requests a multi-link setup to establish one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs; and a transmitter that, in operation, transmits a response frame to the first STA to notify a result of the multi-link setup, where the response frame conveys information of the one or more links established between the one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs.

[0117] The second STA according to one example, wherein the request information identifies one or more STAs of the first plurality of STAs.

[0118] A second STA according to one example, wherein the information of the one or more links includes operating parameters of the one or more links and capability information of one or more STAs among the second plurality of STAs corresponding to the one or more links.

[0119] A second STA according to an example, wherein the response frame further includes information of a traffic identifier (TID) mapped to each of the one or more links, and the first plurality of STAs are permitted to transmit, on each link, only frames belonging to the one or more TIDs mapped to the link.

[0120] A second STA according to one example, wherein the request information includes information regarding the quality of the wireless channel of one or more links, and the second MLD is configured to make an informed decision as to whether to establish the one or more links.

[0121] The second STA according to an example, wherein the response frame further includes information related to a Block ACK parameter of the established link.

[0122] The second MLD is an AP MLD and the first MLD is a non-AP MLD; A frame including information of the common MAC address identifying the AP MLD is transmitted by a STA included in the second plurality of STAs to advertise the AP MLD, the frame being one of a beacon frame or a probe response frame; A second STA according to an example.

[0123] In one example, a second STA, in order to advertise an AP MLD, transmits a frame indicating an AP among the second plurality of STAs to which the request frame is addressed, the frame being one of a beacon frame or a probe response frame.

Claims

1. a circuit for generating an association request frame including information for identifying one or more links requested by a non-access point multi-link device (non-AP MLD) and link-specific information of the requested one or more links; a transmitter for transmitting the association request frame to an access point multi-link device (AP MLD) to request a multi-link setup between the non-AP MLD and the AP MLD; Equipped with the association request frame includes a multilink element including a common information field for indicating a MAC address of the non-AP MLD; Non-AP MLD.

2. the association request frame includes a multi-link element including one or more link information fields, each link information field including information for identifying one of the one or more requested links and its link specific information; The non-AP MLD of claim 1.

3. the link specific information includes parameters necessary for establishing the requested link; The non-AP MLD of claim 1.

4. Before the multi-link setup, the circuit is further configured to generate an authentication frame including a MAC address of the non-AP MLD, and the transmitter is further configured to transmit the generated authentication frame to the AP MLD for multi-link authentication. The non-AP MLD of claim 1.

5. The transmitter transmits a re-setup request frame for establishing a new link different from one or more links established between the non-AP MLD and the AP MLD. The non-AP MLD of claim 1.

6. The transmitter transmits the association request frame on one link that the non-AP MLD wishes to use as part of the multi-link setup. The non-AP MLD of claim 1.

7. and a receiver for receiving an association response frame indicating one or more links accepted by the AP MLD. The non-AP MLD of claim 1.

8. the association response frame is received on the link on which the association request frame was transmitted; The non-AP MLD of claim 7.

9. The non-AP MLD has a plurality of associated stations (STAs), and the AP MLD has a plurality of associated access points (APs), and multi-links are set up between the plurality of associated STAs and the plurality of associated access points (APs) on different frequency bands; The non-AP MLD of claim 1.

10. A communication method for a non-access point multilink device (non-AP MLD), comprising: generating an association request frame including information for identifying one or more links requested by a non-access point multi-link device (non-AP MLD) and link-specific information for the requested one or more links; sending the association request frame to an access point multilink device (AP MLD) to request a multilink setup between the non-AP MLD and the AP MLD; the association request frame includes a multilink element including a common information field for indicating a MAC address of the non-AP MLD; Communication methods.

11. the association request frame includes a multi-link element including one or more link information fields, each link information field including information for identifying one of the one or more requested links and its link specific information; The communication method according to claim 10.

12. the link specific information includes parameters necessary for establishing the requested link; The communication method according to claim 10.

13. Before the multi-link setup, generate an authentication frame including a MAC address of the non-AP MLD, and send the generated authentication frame to the AP MLD for multi-link authentication; The communication method according to claim 10.

14. sending a re-setup request frame for establishing a new link different from one or more links established between the non-AP MLD and the AP MLD; The communication method according to claim 10.

15. sending the association request frame on one link that the non-AP MLD wishes to use as part of the multi-link setup; The communication method according to claim 10.

16. receiving an association response frame indicating one or more links accepted by the AP MLD; The communication method according to claim 10.

17. the association response frame is received on the link on which the association request frame was transmitted; 17. The communication method according to claim 16.

18. The non-AP MLD has a plurality of associated stations (STAs), and the AP MLD has a plurality of associated access points (APs), and multi-links are set up between the plurality of associated STAs and the plurality of associated access points (APs) on different frequency bands; The communication method according to claim 10.

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