Communication equipment and communication method for performing multilink setup and link maintenance.

Abstract

To provide communication devices and methods for multi-link setup and link maintenance.SOLUTION: An AP MLD includes: a receiving unit which receives, from a non-AP MLD, an association request frame including information for specifying one or more links requested for multi-link setup and link specific information of the requested one or more links; a control unit which determines, based on the link specific information, whether to accept each of the requested one or more links; and a transmission unit which transmits an association response frame indicating the link accepted by the control unit. The association request frame includes a common information field for indicating a MAC address of the non-AP MLD.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] Embodiments of the present invention generally relate to communication devices, and more particularly, to methods and apparatuses for performing multi-link setup and link maintenance.

Background Art

[0002] Today, communication devices are expected to operate wirelessly with the same functionality as wired computing devices. For example, users expect to be able to seamlessly view high-resolution movies streamed to their wireless communication devices. This has led to issues related to communication devices and issues related to the access points to which communication devices connect wirelessly.

[0003] The Institute of Electrical and Electronics Engineers (IEEE) 802.11 group has recently formed an 802.11 task group (TG) to address these issues. Multi-link operation in the 2.4 GHz, 5 GHz, and 6 GHz frequency bands has been recognized as an important candidate technology for such communications. Multi-channel aggregation across multiple links is a natural way to increase the throughput of communication data several-fold.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order 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 the association of related stations (STAs) in one or more links. For this purpose, it is required to perform multi-link setup in one of the supported links.

Means for Solving the Problems

[0005] One non-limiting and exemplary embodiment facilitates the provision of a first station (STA) comprising a first plurality of STAs belonging to a first multilink device (MLD), wherein the first STA comprises a circuit that generates a request frame when in operation, the request frame containing request information, and a transmitter that, when in operation, transmits the request frame to a second STA to request a multilink setup, the second STA comprising a second plurality of STAs belonging to a second MLD, the multilink setup establishing one or more links between one or more STAs from the first plurality of STAs and corresponding one or more STAs from the second plurality of STAs based on the request information.

[0006] Another non-limiting and exemplary embodiment facilitates the provision of a second STA, comprising: a receiver that, in operation, receives a request frame from a first STA, the first STA being part of a first plurality of STAs belonging to a first MLD, the request frame containing request information, which requests a multilink setup to establish one or more links between one or more STAs from the first plurality of STAs and corresponding one or more STAs from 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 the result of the multilink setup, the response frame conveying information about one or more links established between one or more STAs from the first plurality of STAs and corresponding one or more STAs from the second plurality of STAs.

[0007] Another non-limiting and exemplary embodiment facilitates the provision of a communication method comprising: generating a request frame in a first STA included in a first plurality of STAs belonging to a first MLD, wherein the request frame includes request information; and transmitting the request frame to a second STA to request a multilink setup, wherein the second STA is included in a second plurality of STAs belonging to a second MLD, and the multilink setup establishes one or more links between one or more STAs from the first plurality of STAs and corresponding one or more STAs from the second plurality of STAs based on the request information.

[0008] It should be noted that general or specific embodiments may be implemented as systems, methods, integrated circuits, computer programs, storage media, or any selective combination thereof. Further benefits and advantages of the disclosed embodiments will become apparent from this specification and the drawings. Benefits and / or advantages may be obtained individually by the various embodiments and features of this specification and the drawings, and not all of them are required to obtain one or more such benefits and / or advantages. [Brief explanation of the drawing]

[0009] The attached figures, along with the following detailed description, are incorporated herein and constitute part of it, illustrating various embodiments and illustrating the various principles and advantages of these embodiments. Throughout the separate figures, similar reference figures refer to identical or functionally similar elements. [Figure 1] This shows the relationship between the coverage frequency and range of a wireless node. [Figure 2] This example illustrates the flow of communication between AP MLDs and non-AP MLDs for multilink setup, link quality assessment, traffic identifier (TID) mapping to links, and subsequent communication. [Figure 3]This diagram illustrates AP MLDs with multiple basic service sets (BSS) in various embodiments, as well as multiple non-AP MLDs within the scope of these BSSs. [Figure 4] This diagram illustrates extended service sets (ESS) containing multiple MLDs in various embodiments. [Figure 5] The first embodiment illustrates the communication flow between an AP MLD and a non-AP MLD for multilink discovery, authentication, setup, TID and link mapping, and subsequent communication. [Figure 6] This diagram illustrates a multi-link action frame according to the first embodiment. [Figure 7] This diagram illustrates the multi-link setup frame according to the first embodiment. [Figure 8] This diagram illustrates a multi-link element according to the first embodiment. [Figure 9] This diagram illustrates a multi-link teardown frame according to the first embodiment. [Figure 10] This diagram illustrates the transmit power control (TPC) requirement elements according to the first embodiment. [Figure 11] This diagram illustrates the elements of a TPC report according to the first embodiment. [Figure 12] This diagram illustrates the multi-link elements configured for multi-link authentication according to the first embodiment. [Figure 13] This diagram illustrates the multi-link elements configured for a multi-link setup requirement according to the first embodiment. [Figure 14A]Shows one variation of the minimum link quality requirement table maintained by AP MLD according to the first embodiment. [Figure 14B] Shows the mapping table of user priority (UP: User Priority) and TID defined in the 802.11 specification. [Figure 14C] Illustrates the multi-link element configured for multi-link setup response and TID-link mapping according to the first embodiment. [Figure 14D] Shows the TID map encoding table according to the first embodiment. [Figure 15] Shows the communication flow between AP MLD and non-AP MLD including multi-link reset setup request according to the first embodiment. [Figure 16] Illustrates the multi-link action frame configured for multi-link setup response according to the first embodiment. [Figure 17-1] Shows the state transition diagram according to the first embodiment. [Figure 17-2] Shows the state transition diagram according to the first embodiment. [Figure 18] Shows an alternative state transition diagram according to the first embodiment. [Figure 19] Illustrates the method of performing link maintenance according to the first embodiment. [Figure 20] Shows the communication flow between AP MLD and non-AP MLD including link quality evaluation step according to the second embodiment. [Figure 21-1] Shows an alternative state transition diagram according to the second embodiment. [Figure 21-2] Shows an alternative state transition diagram according to the second embodiment. [Figure 22] Illustrates the multi-link element configured for multi-link reset setup request and link deletion according to the second embodiment. [Figure 23] Illustrates a Multi-link Teardown frame according to the second embodiment. [Figure 24] Illustrates multi-link setup and link maintenance between an AP MLD and a non-AP MLD according to various embodiments. [Figure 25] Shows a schematic diagram of an MLD 2500 according to various embodiments. [Figure 26] Shows a flowchart 2600 illustrating a method for secure retransmission of multi-links according to various embodiments. [Figure 27] Shows a partially framed schematic diagram of one of the associated STAs 2700 of a multi-link device that can be implemented for multi-link communication according to various embodiments.

[0010] Those skilled in the art will understand that the elements in the figures are shown for purposes of brevity and clarity and are not necessarily drawn to scale. **DETAILED DESCRIPTION OF THE INVENTION**

[0011] The following detailed description is merely exemplary and is not intended to limit the embodiments or the application and uses of the embodiments. Further, it is not intended to be bound by the theory presented in the previous background art or detailed description of the invention section. Furthermore, other desirable features and characteristics will become apparent from the following detailed description and the appended claims in conjunction with the accompanying drawings and the background of the present disclosure.

[0012] Generally, when the 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 necessary to enable data manipulation between them. This state corresponds to state 3 in the non-mesh STA state transition diagram, where the IEEE 802.1X control port is blocked (i.e., only EAPOL (Extensible Authentication Protocol over LANs) data frames are allowed, and other data frames are not). - Enabled (Activated): Both MLDs agree to initiate data operations on the link. For example, 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 non-mesh STA state transition diagram, where the IEEE 802.1X control port is unblocked (i.e., all data frames are allowed). - Disabled: In this state, the link may be set up but data manipulation is disabled, or setup and RSNA are complete but the TID is not 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 to define the rules for allowed / forbidden frames and associated MLD behavior for each link state.

[0014] Furthermore, multiple different links in an MLD can have different range / channel conditions. Referring to Figure 1, which shows the relationship between the coverage frequency and range of a radio node, 11af coverage (54-698 MHz) has a coverage range of over 3 km, cellular coverage (600-900 MHz) has a range of 1-3 km, 11ah coverage (900 MHz) has a range of 1 km, 11b / g / n coverage (2.4 GHz) has a range of 100 m, 11a / ac coverage (5 GHz) has a range of 50 m, and 11ad coverage (60 GHz) has a range of 10 m. If setup frames for a multilink setup are exchanged on a lower frequency band link (e.g., 2.4 GHz band), the MLD may not be within range on other links in higher frequency bands (e.g., 5 GHz or 6 GHz). Furthermore, even if MLD is within range on other supported links, some links may have poor quality due to, for example, excessive overlapping OBS (OBSS: overlapping basic service set) interference, frequency-dependent fading, or coexisting interference (such as Bluetooth in the 2.4GHz band), and therefore may not be suitable for link activation.

[0015] In fact, the link capability of a non-AP MLD alone may not provide sufficient information to set up a link. Some (potential) links / STAs of an MLD may be in a fourth state (i.e., not set up (not established / unavailable)) after the multilink setup procedure is complete. Therefore, frame exchange is not possible on that link. However, such links may become set up if conditions change (for example, if the non-MLD moves closer to the AP MLD).

[0016] Therefore, links should not be set up or established based solely on capability information. Non-AP MLDs should be able to select which links are set up. Additionally, the channel quality of links (especially second and subsequent links) should be checked before establishing / activating the links (checked during the multilink setup itself or during the subsequent activation operation). Furthermore, the channel quality of activated links should be checked periodically to ensure that the links are alive and suitable for the TIDs mapped to them.

[0017] Therefore, the present invention aims to solve the problems described above.

[0018] Figure 2 shows the communication flow between AP MLD 202 and non-AP MLD 204 for multilink setup, link quality assessment, traffic identifier (TID) and link mapping, and subsequent communication, using a typical solution to address the aforementioned challenges. During multilink setup, non-AP MLD 204 sends a multilink setup request 206 to AP MLD 202 on link 2. The multilink setup request includes information about the link capabilities of links 1, 2, and 3. In response to this request, AP MLD 202 sets up the requested links 1, 2, and 3, and then sends a multilink setup response 208 to non-AP MLD 204 notifying it of the link setup. At 210, non-AP MLD 204 is authenticated / associated, and the three links are now set up. Subsequently, a multilink RSNA (4-way handshake / group key handshake) is performed between AP MLD 202 and non-AP MLD 204 on link 2. Links 1, 2, and 3 each connect the associated STA of AP MLD 202 to the associated STA of non-AP MLD 204, and it will be understood that these STAs can transmit or receive any data or frames over these links.

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

[0020] Subsequently, AP MLD 202 can initiate TID-link mapping by determining the TIDs to be mapped to each link based on the link quality assessment and sending a TID-link mapping request 222 to non-AP MLD 204 on link 2. The TID-link mapping request includes a TID map showing how each TID is mapped to each link. In response, non-AP MLD 204 sends a TID-link mapping response 224 to AP MLD 202 on link 2 to indicate the status of TID mapping. After all three links are enabled and the TIDs have been mapped to the links (226), frame exchange can be performed 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., included in the multilink setup request 206). Furthermore, this is an AP-centric solution, meaning that the STA has no say in which links are set up or enabled.

[0022] During multi-link setup, additional links (i.e., links other than those used to exchange the Multi-link Setup frame) should not be set up (established) based solely on capability information. The first MLD can request which links to be set up, regardless of their capability, from the second MLD as part of the multi-link setup, for example using the Setup Request field of the Multi-link Setup Request frame. The MLD can also include information about the link quality of the requested links (e.g., uplink / downlink (UL / DL) link margin, UL / DL path loss, etc.). 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 are sometimes referred to as a multi-link set. The second MLD may also consider information about link quality to decide whether to set up / enable a link, especially if some links have TID restrictions. This information can also be used for subsequent TID-link mapping (i.e., enabling / disabling links).

[0023] Figure 3 shows a schematic diagram 300 of AP MLD 302 having multiple BSSs and non-AP MLDs 304, 306, and 308 within the BSS range, according to various embodiments. AP MLD 302 can be shown as schematic diagram 314, including a MAC-Service Access Point (MAC-SAP) for accessing the 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 links at the physical layer to transmit and receive data (i.e., AP1 is connected via link 1, AP2 via link 2, and AP3 via link 3).

[0024] Furthermore, non-AP MLDs 304, 306, and 308 can be represented as schematic diagram 316, which includes a MAC-SAP for accessing the DS, an MLD MAC address that identifies 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 links at the physical layer to send and receive data (i.e., STA1 is connected via link 1, STA2 via link 2, and STA3 via link 3).

[0025] The AP MLD 302 sets up multiple (multilink) BSSs (one BSS per associated AP). Each BSS has its own BSSID and beacon, and can have different coverage. For example, AP1 operates its BSS at 6GHz, AP2 at 5GHz, and AP3 at 2.4GHz. The coverage of different APs can differ (due to frequency band, transmit (Tx) power, etc.). Coverage can also depend on the modulation and coding scheme (MCS), meaning MCS 0 can have much greater coverage than MCS 9. Furthermore, non-AP MLDs can be within the range of one or more such BSSs. For example, only STA1 of non-AP MLD 304 is within the coverage of AP MLD 302 via AP1, only STA1 and STA2 of non-AP MLD 308 are within the coverage of AP MLD 302 via AP1 and AP2, and all three STAs of 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 enables access to the DS via 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 the AP MLD to obtain access to the DS. However, all APs of an AP MLD can connect to the DS via the same single MAC-SAP and DSAF.

[0027] This network forms the Extended Service Set (ESS) 400 shown in Figure 4. STA1, STA2, and STA3, belonging to non-AP MLD 1, can obtain access to the DS by connecting to AP1, AP2, and AP3 of AP MLD 1, respectively. AP1, AP2, and AP3 can connect to the DS via MAC-SAP and DSAF of AP MLD 1. Furthermore, STA4, STA5, and STA6, belonging to non-AP MLD 2, can obtain access to the DS by connecting to AP4, AP5, and AP6 of AP MLD 2, respectively. AP4, AP5, and AP6 can connect to the DS via MAC-SAP and DSAF of AP MLD 2. Traditionally, legacy STAs such as STA7 obtained access to the DS by associating with an AP, and could also maintain access to AP MLDs by associating with one of the associated APs of AP MLD (e.g., AP4 of AP MLD 2). However, in the case of non-AP MLDs, the association process can be replaced by a multilink setup procedure, as will be explained further later. A multilink setup performed between any one pair of related STAs and related APs can provide one or more related STAs of a non-AP MLD with access to the DS.

[0028] Figure 5 shows the communication flow between the AP MLD and the non-AP MLD for multilink discovery, authentication, setup, TID-link mapping, and subsequent communication according to the first embodiment. First, during the multilink discovery phase, the non-AP MLD 504 checks the quality of links 1, 2, and 3 by sending probe request frames 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 probe response frame 508 to the non-AP MLD 504 on each link. The beacon frame or probe response frame 508 may include the MLD MAC address of the AP MLD 502 and a TPC Report element. After the multilink discovery phase is complete, the non-AP MLD can be considered to be in state 1.

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

[0030] After successful authentication, the non-AP MLD 504 can initiate multilink setup / association by sending a multilink setup request 514 to the AP MLD 502, for example, on link 2. The multilink setup request 514 may include request information that identifies the link capabilities of links 1, 2, and 3, and the associated STA of the non-AP MLD 504 on which the links (i.e., in this case links 1, 2, and 3) are to be set up. The request information may also include information regarding the quality of each radio channel of links 1, 2, and 3. The request information may further include information regarding the expected traffic characteristics for each of links 1, 2, and 3, where the traffic characteristics are one of the following: traffic identifier (TID), payload size, delay limit, data rate, minimum PHY rate, etc.

[0031] In response to this request, 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 non-AP MLD 504 notifying it of the link setup. 518 confirms that 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 non-AP MLD can change to state 3. Subsequently, a multilink RSNA (4-way handshake / group key handshake) between AP MLD 502 and non-AP MLD 504 can be performed, for example, on link 2.

[0032] After the multilink setup is complete, AP MLD 502 can initiate TID-link mapping by sending a TID-link mapping request 522 to a non-AP MLD 504, for example, on link 2. The TID-link mapping request 522 may include a TID map for the requested links 1, 2, and 3, showing how each TID is mapped to each link. In response, non-AP MLD 504 may send a TID-link mapping response 524 to AP MLD 502 on link 2 to indicate the status of the TID mapping. After all three links are enabled and the TIDs have been mapped to the links (526), ​​frame exchange can be performed on any / all of the three links (528). After TID-link mapping is completed in 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 set up links.

[0033] Furthermore, each of links 1, 2, and 3 connects the associated AP of AP MLD 502 to the associated STA of non-AP MLD 504, and it will be understood that these STAs transmit or receive any data or frames on the links. The associated STA of non-AP MLD 504 may be configured to collect information regarding the quality of the radio channel for each of one or more links before sending the setup request 514, and the quality of the radio channel includes one or more of the link margin, path loss, receive signal strength indicator (RSSI), and receive channel power indicator (RCPI).

[0034] For the multilink operation shown in Figure 5, a new (Class 1) action frame can be defined. Figure 6 illustrates a new multi-link action frame 600 according to the first embodiment. The multi-link action frame 600 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, a Variable field, and a Frame Check Sequence (FCS) field. The Multi-link Action field may have a value of 0, indicating that the action frame targets multilink setup, or a value of 1, indicating that the action frame targets multilink teardown. Values ​​2 to 255 may be reserved.

[0035] Figure 7 illustrates a Multi-link Setup frame 700 according to the 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 value 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] Figure 8 illustrates 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 can be communicated in a multi-link action frame 600, or in other frames such as an association request / response frame or another management frame. If multiple multi-link actions (e.g., TID mapping and BA setup, or multi-link setup and TID mapping) are signaled in the same frame exchange, multiple multi-link elements may be communicated in the same frame. The actions are signaled by the value indicated in the Action Type field of the multi-link element 800. A value of 0 can indicate multilink authentication, a value of 1 can indicate a multilink setup request, a value of 2 can indicate a multilink setup response, a value of 3 can indicate a TID-link mapping request, a value of 4 can indicate a TID-link mapping response, a value of 5 can indicate a block ACK setting request, and a value of 6 can indicate a block ACK setting response. Other values ​​from 7 to 255 can be reserved.

[0037] Figure 9 illustrates a multi-link teardown frame 900 according to the 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 value 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. In addition, different signaling can be defined for the purpose of adding / removing links (i.e., Multi-link add / remove requests / responses).

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

[0040] AP MLD 502 can estimate 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 sent to the non-AP MLD 504 in each multilink BSS (i.e., in the modified TPC report element). Figure 11 illustrates the TPC report element 1100 according to the first embodiment. The TPC report element 1100 may 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 for the host frame (i.e., the probe response frame 508). The link margin is the difference between the received power (dBm) and the received sensitivity (dBm). The Link Margin field is encoded as a two's complement signed integer in decibels and can be set to -128 to indicate that there is no link margin. Path loss is the difference between the transmit power of frames carrying TPC Request elements, such as probe request frames, and the received power received from non-AP MLDs. The Path Loss field is encoded as a two's complement signed integer in decibels and can be set to 128 to indicate that there is 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 a non-AP MLD 504 receives a probe response frame 508, it can calculate DL path loss using the transmit power information in the TPC Report element, while simultaneously 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 for each BSS (link). Alternatively, if the link measurement request / report frame is reclassified as a Class 1 frame for non-directional multi-gigabit (non-DMG) / 11be STA, similar information can be achieved using these frames. Furthermore, the AP MLD 502 can also advertise its MLD MAC address in the beacon frame / probe response frame (e.g., within the multilink capability element) for use during multilink authentication (SAE, FILS) and multilink setup. If not advertised, the probe request frame must request that the AP MLD's MAC address be displayed. While link measurement request / response frames were mentioned as an alternative, it should be understood that any other suitable control frame may be used for this purpose. Furthermore, the results of sounding procedures (e.g., Channel Quality Index (CQI)) can also be used if available.

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

[0043] Referring to Figure 5, it is assumed that the non-AP MLD 504 discovers the AP-MLD's MLD MAC address during multilink discovery. However, for the purpose of enabling the AP MLD 502 to authenticate the non-AP MLD 504 and signaling the AP MLD 502 to use the MLD MAC address in SAE authentication and FILS authentication, the non-AP MLD 504 needs to include its own MLD MAC address in the authentication frame / multi-link setup frame (for example, within a multi-link element). For this purpose, a multi-link element can be conveyed in the authentication frame (or multi-link setup frame). Figure 12 shows an illustration of a multi-link element 1200 configured for multilink authentication according to the first embodiment. The multi-link element 1200 contains the same fields as the multi-link element 800. However, the Action Type field is set to 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 understood 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 permitted to associate with other MLDs.

[0044] Figure 13 illustrates a Multi-link element 1300 configured for a Multi-link Setup Request according to the first embodiment. The Action Type field is set to 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 that conveys 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 link-specific information, 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 in Figure 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 no setup is requested for that link, and a value of 1 indicates that a setup is requested. The non-AP MLD 504 may consider link quality information to determine which links to request multi-link setup for. Other factors may also be considered; for example, the non-AP MLD 504 may have the capability for a 2.4GHz link (i.e., link 1) but choose not to request setup for this link due to coexistence issues with its own Bluetooth radio, or it may choose not to request setup for a particular link for reasons such as power saving. The non-AP MLD 504 may also include information about the link quality of the requested links (e.g., UL / DL link margin, UL / DL path loss, etc., obtained at discovery). If link quality information is unavailable, the Received Signal Strength Indicator (RSSI) / Received Channel Power Indicator (RCPI) of beacon / probe response frames received on the link may be included as an estimate of link quality. Alternatively, if the results of a sounding procedure (e.g., Channel Quality Index (CQI)) are available as link quality information, they may be used.

[0046] Furthermore, the non-AP MLD 504 may also include fields describing the characteristics of the traffic flow and the expected QoS values ​​on the link. In addition, the link quality information in the UL Link Margin subfield, UL Path Loss subfield, DL Link Margin subfield, and DL Path Loss subfield may be omitted if the link setup is not required. Advantageously, this allows the link to be set up based on the requirements and link quality of the non-AP MLD.

[0047] When AP MLD 502 receives a multilink setup request from a non-AP MLD 504, it performs the setup of only the links requested by the non-AP MLD 504 (i.e., AID assignment, insertion into association records, etc.) and subsequent procedures (i.e., TID-link mapping, security key generation / distribution, etc.). AP MLD 502 can use information about link quality to determine whether to set up / enable the requested links, especially if some links have TID restrictions. This information can also be used for subsequent TID-link mapping (i.e., enabling / disabling links). AP MLD 502 can maintain a table of the minimum link quality required for non-AP MLDs to use the links.

[0048] Figure 14A shows one variation of the minimum link quality requirements table maintained by AP MLD according to the first embodiment. Figure 14A specifies the link quality (in terms of link margin) required to map a TID to a particular link. Different links may have different values. For example, referring to Figure 14A, the link to which TID 6,7 (AC_VO) is mapped may have a higher link quality requirement in order to support a higher MCS. This requirement may differ between uplinks (UL) and downlinks (DL). Figure 14B shows the mapping of User Priority (UP) and TID as defined 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 specific requested link for a non-AP MLD. For example, AP MLD may refuse to enable the link mapped to TIDs 6 and 7 for a non-AP MLD that shows a large amount of traffic flow at TIDs 6 and 7, in order to maintain QoS requirements on the link. In some cases, AP MLD may set up all requested links and consider link quality only to decide whether to enable the links (e.g., during the initial or subsequent TID-link mapping). In other cases, AP MLD may also consider link quality when setting up the requested links.

[0050] AP MLD can include only information about the set-up links in the multi-link setup response frame. Figure 14C illustrates a Multi-link Action frame 1400 configured for the multi-link setup response and TID-link mapping according to a 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 a TID-link mapping request (i.e., set to value 3) and can 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 can contain a Link ID subfield, an UL TID Map, and an DL TID Map. Each TID map can be a bitmap (i.e., 8 bits, 1 bit per TID) showing the TID mapped to the link in its direction (UL or DL), or it can represent the TID using one or more 4-bit fields. An example of encoding a TID map based on 4-bit fields is shown in Figure 14D, which has values ​​from 0 to 15.When a non-AP MLD receives a TID-link mapping request frame from an AP MLD, it can send back a TID-link mapping response frame indicating acceptance of that TID mapping. If the TID mapping is rejected, a default TID mapping is applied to the link, or the AP MLD can disable the link for the non-AP MLD. It will be understood that in a multi-link setup action frame (or association response frame), two multi-link elements can be communicated to signal multi-link setup and TID-link mapping, respectively, or they can be combined into a single element.

[0051] Furthermore, not only can multilink setup request / response frames be used for multilink setup, but association request / response frames (including the Multi-link element) can also be used for multilink setup. Once multilink setup is successfully completed, one or more non-AP STAs of non-AP MLDs are able to call distribution system services through one or more AP STAs of AP MLDs.

[0052] For example, you can define a new MAC sublayer management entity (MLME) primitive for multilink setup, for use by non-AP MLDs or AP MLDs. The MLME primitive is 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 primitive for requesting a multilink setup for a non-AP MLD is as follows: [Table 1]

[0053] This primitive sends a Multi-link Setup Request frame 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 peer MLD's associated STA (on the link to which the Multi-link Setup Request frame is sent). One or more Multi-link elements can be included to convey the information necessary for the Multi-link Setup Request.

[0054] For non-AP MLDs, the primitives used to verify a multilink setup can be as follows: [Table 2]

[0055] This primitive is generated when a multi-link setup response frame is received. PeerMLDAddress is set as the MLD MAC address of the peer MLD. It contains one or more multi-link elements conveyed in the multi-link setup response frame. The Dialog Token is used to identify the multi-link setup request / response transaction.

[0056] A non-AP MLD indicates that one or more links are available by calling the MLME-MULTI-LINK-SETUP.confirm primitive. This signals the supplicant that the MLD's MAC has transitioned to state 3. If the MLD negotiates to use IEEE 802.1X authentication during multilink setup, the MLD's administrative entity may 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 performed by the non-AP MLD's decision to initiate multilink setup and the AP MLD's decision to accept the multilink setup.

[0057] The primitive to indicate the receipt of a multilink setup request for AP MLD can be as follows: [Table 3]

[0058] This primitive can be generated when a Multi-link Setup Request frame is received. PeerMLDAddress is set as the MLD MAC address of the peer MLD. It contains one or more multi-link elements transmitted in the Multi-link Setup Request frame.

[0059] The primitives for responding to multilink setup requests for AP MLD can be as follows: [Table 4]

[0060] This primitive sends a multilink setup response frame 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 (on the link to which the multilink setup response frame is sent). One or more multi-link elements can be included to convey the information necessary for the multilink setup response.

[0061] Furthermore, primitives that request multilink teardown (both non-AP MLD and AP MLD) can be configured as follows: [Table 5]

[0062] This primitive sends a Multi-link Teardown frame. PeerMLDAddress is set as the MLD MAC address of the peer MLD. Optionally, it can include one or more link IDs, each identifying the link being teardown.

[0063] A non-AP MLD can request the addition of a new link by re-running the multilink setup. This can also include link quality and traffic flow information. Figure 15 shows a diagram 1500 of the communication flow between AP MLD 1502 and non-AP MLD 1504, including a multilink re-setup request, according to a first embodiment. During multilink setup, AP MLD 1502 refuses to set up link 3 due to poor link quality. Therefore, only links 1 and 2 are enabled. Subsequently, non-AP MLD 1504 can request the setup of link 3 by sending a multilink setup request 1506 to AP MLD 1502, for example, because the link quality of link 3 has improved, and the request information may include link capability, information identifying link 3, and the link quality of link 3. AP MLD 1502 sets up the requested link based on the request information and sends a multilink setup response 1508 to non-AP MLD 1504 containing information about the set up link (i.e., link 3) and the TID map for link 3. Authentication by the IEEE 802.1X server, PMKSA configuration, etc., are not performed. Advantageously, this allows for the flexible addition of new links with improved link quality.

[0064] Since non-AP MLD 1504 is assumed to have already been authenticated and associated with AP MLD 1502 during the initial multilink setup, AP MLD 1504 only performs the procedures related to the requested addition of a new link (e.g., AID assignment for the new link, updating the link MAC address in the association record, TID-link mapping, etc.). It can also generate / distribute security keys for the new link (i.e., Pairwise Temporal Key (PTK), Group Temporal Key (GTK), or Integrity Group Temporal Key (IGTK)) as needed. If the same PTK is used for all enabled links, a 4-way handshake is not required for the new link. If different GTKs / IGTKs are used for the new link, they can be distributed using a group key handshake. Alternatively, instead of reusing the multilink setup, a different signaling (e.g., multilink-link-add request / response) can be defined for this purpose.

[0065] When adding a new link, it may be necessary to modify some parameters of the existing block ACK agreement for the TID mapped to the new link. For existing block ACK agreements originating from an AP MLD (i.e., in a DL flow), the AP MLD may also include the relevant block ACK parameters in the same frame that transmits the multilink setup response. Non-AP MLDs may follow suit by initiating an update of the block ACK parameters for the TID mapped to the new link for a UL flow (piggybacked in an Additional Block Acknowledgment (ADDBA) request frame or in another frame such as a TID-link mapping response frame).

[0066] Figure 16 illustrates a Multi-link Action frame 1600 configured for a Multi-link Setup Response to Add a New Link, according to a 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 may include one or more Link Information fields, each of which includes a Link ID field and one or more TID Information fields. Furthermore, one or more TID Information fields may include a TID subfield, a Scoreboard Size subfield, and a Starting Sequence Number subfield. The relevant block ACK parameters for the new link can thus be included in the Multi-link element field 1602.

[0067] Upon receiving a Multi-link Action frame 1600, a non-AP MLD may, in response to a TID-link mapping request 1604, send a TID-link mapping response frame to the transmitting AP MLD. The TID-link mapping response frame may be a Multi-link Action frame that conveys a Multi-link element whose action type is set to TID-link mapping response.

[0068] Dynamically enabling / disabling links (using TID-link mapping) can affect block ACK parameters (e.g., receive sort buffer size, unified BA scoreboard size, etc.), and ADDBA renegotiation may be triggered each time a link is enabled or disabled. For example, if a new link is added, the BA scoreboard size, start sequence number, etc., must be specified for the new link. Also, the receiving MLD may need to increase the size of its receive (RX) sort buffer to receive additional frames from the added link.

[0069] Figure 17 shows a state transition diagram 1700 according to the first embodiment. For each MLD that needs to communicate directly via the WM through one or more links, an enumerated state variable can be maintained (instead of maintaining state between two associated STAs). For example, based on state transition diagram 1700, each MLD is in one of the following 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). Upon successful authentication, the state of the MLD changes from "State 1" to "State 2". Upon successful multilink setup (at least one link is requested), the state of the MLD changes from State 2 to State 3. Security parameters are checked during multilink setup. MLDs performing IEEE 802.1X authentication use open system authentication. MLDs performing password-based authentication can use SAE authentication. MLDs performing FILS use FILS authentication. SAE and FILS authentication provide mutual authentication and PMK derivation. If open system authentication is selected instead, the authenticator or supplicant initiates IEEE 802.1X authentication. Before IEEE 802.1X authentication and key installation are complete, the AP MLD's IEEE 802.1X control port blocks all data frames. The IEEE 802.1X non-control port allows IEEE 802.1X frames to pass between the supplicant and authenticator. The authentication process creates a cryptographic key that is shared between cryptographic endpoints, regardless of 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 using SAE / FILS, and the IEEE 802.1X AS (authentication server) and non-AP MLD when using IEEE Std 802.1X.When using IEEE Std 802.1X, the AS transfers 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 verification handshakes (e.g., a four-way handshake or FT four-way handshake over either link). When using SAE authentication, there is no AS, and therefore no key transfer occurs. The four-way handshake is performed directly between the AP MLD and the non-AP MLD. The key verification handshake indicates that the link is secured by the key and ready to allow normal data traffic and protected, robust management frames. When FILS authentication is performed, key verification is performed as part of the FILS exchange using the association frame; therefore, no additional handshake is required. If a key verification handshake has been completed for at least one link, the IEEE 802.1X control port is considered unblocked to the non-AP MLD. After a multilink teardown, the IEEE 802.1X control port reverts to an unauthenticated state and blocks all data frames.

[0070] Furthermore, the link state is maintained for each (associated STA pair) / link, and can be in one of the following four states. - Not Setup (Not Established / Unavailable): AP MLDs and non-AP MLDs do not have all the information necessary to enable data manipulation between them. Allowed frames depend on the MLD state. Data frames are not allowed. Access to DS is not allowed. - Setup (Established): AP MLDs and non-AP MLDs have all the information necessary to enable data manipulation between them. Data frames (except EAPOL frames) are not permitted. Access to DS is not permitted. - Enabled (Activated): Both MLDs agree to initiate data operations on the link. For example, at least one TID is mapped to the link, and a Security Association (RSNA) has been completed for the link. All frames permitted by the TID mapping are permitted. Access to the DS is permitted. - Disabled (Deactivated): Data frames (except EAPOL frames) are not allowed. Non-data frames may be allowed. Access to DS is not allowed.

[0071] For legacy STAs or non-MLD STAs, the normal authentication / association process can be used, and the state is maintained at the STA level. The multilink setup between MLD pairs creates unique pairs of IEEE 802.1X ports, and authentication is performed only for these ports. Essentially, for MLDs, the roles of authenticator and supplicant can be implemented at the MLD level rather than the STA level.

[0072] When an STA / link is in the Not Setup state, data frames other than EAPOL are not permitted for that link, even if the IEEE 802.1X control port is unblocked at the MLD level. Upon successful multilink setup (link requested), the link state changes from Not Setup to Setup. Upon successful 4-way / group key handshake + TID-link mapping (at least one TID is mapped to the link), the link state changes from Setup to Enabled. Upon successful TID-to-link mapping, the state switches between Enabled and Disabled. When a multilink teardown occurs, the MLD state becomes State 1, and all associated STA / links enter the Not Setup state. Furthermore, while no TID is mapped to an STA / link in both the Setup and Disabled states, a security key may not have been generated for the STA / link in the Setup state. On the other hand, in the disabled state, a security key is generated for the STA / link. However, in either state, the TID is not mapped to the link, and even if the IEEE 802.1X control port is unblocked, the AP cannot transfer data frames from the link to the DS.

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

[0074] According to the first embodiment, 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), and RSSI. Figure 19 illustrates how link maintenance is performed according to the first embodiment. For links with active transmission, link quality can be measured based on transmitted / received frames. For inactive links (awake power save state), link quality can be accessed by periodically transmitting management frames (i.e., responsive / non-responsive link measurement frames) (i.e., once per beacon interval). If the link quality falls below a certain threshold, the link can be considered "down". Data frames are not allowed on a "down" link, or may be transmitted at a lower MCS. The threshold may depend on the TID mapped to the link, the link's MCS requirements, 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 link quality remains below a threshold for a certain timeout period, that link can be disabled (by TID-link mapping). Conveniently, this ensures that links are set up based on link quality.

[0075] According to the second embodiment, a non-AP MLD can implicitly signal which links will be set up during a multilink setup by including only the link information it requests to be set up (i.e., link capability, MAC address, etc.). Information on links that are not requested to be set up is not included in the multilink setup request. For example, a setup request may include information indicating the capability information and MAC address of only the relevant STA of the non-AP MLD to which the link is to be set up. This can be used as a default option for requesting a link to be set up. Alternatively, a request not to set up a link is implicitly signaled by providing link information but setting extremely low link quality values ​​(i.e., setting the path loss for the link to the maximum value (e.g., 128) or the link margin to the minimum value (e.g., -128) for either UL / DL or both). For example, a setup request may include information on the radio channel quality of multiple links that can be set up between a first set of multiple STAs and a second set of multiple STAs, with the radio channel quality set to implicitly indicate one or more links to be set up. Alternatively, as described in the previous embodiment, an explicit request to set up the link can be provided in the Multi-link Setup frame.

[0076] If link quality information is not included in the multilink setup request, the AP MLD may initiate a link quality assessment of the requested links, including / excluding the link on which the multilink request was received, before sending the multilink setup response, and decide whether to set up the links. Figure 20 shows the communication flow 2000 between AP MLD 2002 and non-AP MLD 2004, including a link quality assessment step, according to a second embodiment. After the non-AP MLD 2004 initiates multilink setup by sending a multilink request to AP MLD on link 2 to request the setup of links 1, 2, and 3, AP MLD 2002 initiates link quality assessment by sending link measurement requests 2006 and 2010 on link 3 and link 1, respectively (before sending the multilink setup response). In this example, the link quality assessment of the requested links excludes the link on which the multilink request was received (i.e., link 2), but AP MLD may choose to include that link as well. In response to the link measurement requests, non-AP MLD 2004 sends Link Measurement Report 2008 on Link 3 (in response to Link Measurement Request 2006) and Link Measurement Report 2012 on Link 1 (in response to Link Measurement Request 2010) to AP MLD 2002. Based on the collected link quality information provided by Link Measurement Reports 2008 and 2012, AP MLD decides to set up / establish only Links 1 and 2 (in 2014). Link 3 is rejected. Therefore, AP MLD 2002 sends a multilink setup response indicating that Links 1 and 2 will be set up.

[0077] AP MLD 2002 can use link quality information to determine whether to set up / enable a requested link, especially if some links have TID limitations. However, the link quality assessment must be performed in a way that allows for multilink setup to be executed within the timeout value associated with the setup. Furthermore, while the example shown in Figure 20 demonstrates the use of link measurement request / response frames, it will be understood that any other suitable management frame can be used for this purpose.

[0078] Figure 21 shows an alternative state transition diagram 2100 according to the second embodiment. In state transition diagram 2100, alternative states of the MLD are assumed, and these states are maintained at each relevant STA level of the MLD, similar to the legacy STA. Furthermore, the roles of authenticator and supplicant are implemented at the STA level (not the MLD level). This version of the state machine is possible with SAE and FILS authentication, i.e., IEEE 802.1X authentication is not used. Simultaneously, the link maintains its own state, which is the same as in the first embodiment.

[0079] For example, both STA1 and STA2 are in state 1 (unauthenticated, unassociated class 1 frame, link not set up) at 2102. When an STA / link is in the Not Setup state, data frames are not allowed on that link. Upon successful (multilink) authentication, at 2104, the state of all associated STAs (i.e., STA1 and STA2) becomes state 2. However, the state of excluded associated STAs remains state 1. Upon successful multilink setup (where a link is requested), the link's state changes from Not Setup to Setup, and the corresponding associated STA's state changes to state 3. Unrequested links remain in the Not Setup state, and the corresponding associated STA's state remains state 1 or state 2. For example, after a successful multilink setup where link 1 (corresponding to STA1) is requested, at 2106, STA1 is in state 3, and STA2 is still in state 2. If the 4-way / group key handshake + TID-link mapping (at least one TID is mapped to a link) is successful, the link state changes from Setup to Enabled, and the state of the corresponding associated STA changes to state 4. For example, at 2108, after a successful 4-way / group key handshake + TID-link mapping (one or more TIDs are mapped to link 1) from 2106, STA1 is in state 4 and link 1 is enabled, while STA2 is still in state 2 and link 2 is not yet set up. If a multilink re-setup requesting link 2 is successful, at 2110, STA2 changes from state 2 to state 3 (i.e., link 2 is set up). If TID-link mapping is successful, the link state switches between Enabled and Disabled, but the state of the associated STA does not change.For example, at 2114, after a successful TID-link mapping (one or more TIDs are mapped to link 2, but no TIDs are mapped to link 1) from 2110, and a successful 4-way / group key handshake for link 2, STA1 is in state 4 despite link 1 being invalid, and STA2 is in state 4, meaning link 2 is valid. Alternatively, these state changes can also occur at 2114 after a successful multi-link re-setup (i.e., link 2 is requested) from 2108, a 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. Furthermore, at 2116, after a successful TID-link mapping (one or more TIDs are mapped to link 1, but no TIDs are mapped to link 2) from 2114, both STA1 and STA2 are in state 4, meaning link 2 is valid but link 1 is invalid. Furthermore, from 2116, it is also possible to return to 2114 due to a successful TID-link mapping in which one or more TIDs are mapped to link 2 but no TIDs are mapped to link 1. In addition, multilink teardown returns to 2102, where the state of all associated STAs becomes state 1 and all links become Not Setup.

[0080] In this example, the difference between Setup and Disabled is that in both cases, the TID is not mapped to the link. In the Setup state, a security key does not need to be generated for the STA / link, but in the Disabled state, a security key is generated for the STA / link. However, in both states, the TID is not mapped to the link, and the AP cannot transfer data frames from the link to the DS.

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

[0082] Figure 22 illustrates the 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, with one Link Information field for each link being 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 can be used to indicate whether deletion is requested for the link in question (i.e., value 0 = not requested, value 1 = requested). For example, if the value of the Deletion Requested subfield is 1, the link is removed from the multilink set. Link quality information that can 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 to delete a link. Referring to Figure 23, which shows a Multi-link Teardown frame 2300, the Multi-link Action field is set to Multi-link Teardown (i.e., value 1). There may be one or more Link ID fields, with one Link ID field for each link being established.

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

[0085] According to a third embodiment, the AP MLD may restrict frame exchange for a multilink setup to one of the links (i.e., the highest frequency band link (e.g., 6 GHz)) to ensure that non-AP MLDs are within range on all links. For example, whether or not frame exchange for a multilink setup is permitted on a given link can be signaled at the discovery stage (e.g., in a beacon / probe response frame transmitted on the link, or in a (abbreviated) neighbor reporting element transmitted on other links). Alternatively, the AP MLD may attempt to ensure that the BSS of all its associated APs have approximately the same coverage range by controlling the transmit power of each associated AP. However, in this case, the transmit power of APs associated with a lower frequency band (e.g., 2.4 GHz) BSS may be significantly lower than the transmit power of APs associated with a higher frequency band (e.g., 5 / 6 GHz) BSS. Thus, while these measures can mitigate range difference issues, they may not mitigate other link quality issues.

[0086] Figure 24 illustrates the multi-link setup and link maintenance between an AP MLD and a non-AP MLD. For 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 measure the link quality by listening for beacons on all three links (passive scan) or performing an active scan (exchanging probe request / response frames). The non-AP MLD is authenticated by the AP MLD by exchanging an authentication frame or multi-link setup (authentication) frame 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 that links 2 and 3 be set up 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 may also include link quality information for links 2 and 3.

[0087] The AP MLD considers setting up links 2 and 3 and decides to set up both links. The AP MLD sends a multilink setup response frame indicating that links 2 and 3 have been set up. At this stage, the multilink set consists of links 2 and 3. In this example, the AP uses the default TID-link mapping for all links, and therefore the multilink setup response frame does not contain TID-link mapping information. Thus, in step 2404, the AP MLD and the non-AP MLD are associated, and the AP MLD records the relevant information for the non-AP MLD and the relevant information for links 2 and 3. Information for link 1 is not recorded. At this stage, these MLDs are in state 3, but the IEEE 802.1X control port is still blocked. Immediately afterward, IEEE 802.1X authentication is performed, security keys for links 2 and 3 are generated and distributed to the non-AP MLD. At this stage, these MLDs are in state 4, and the IEEE 802.1X control port is unblocked. Links 2 and 3 are considered enabled at this stage, while Link 1 remains in a not-setup state. At this stage, dataframes and non-dataframes can be exchanged on Links 2 and 3.

[0088] After a while, AP MLD recognizes that the link quality of Link 2 has fallen below the AP's required quality threshold for this link. AP continues to monitor the link and, because the link quality remains below the required threshold for a period longer than a specific timeout period, decides to disable the link by performing a TID-link mapping that does not map the TID to Link 2. As a result, in step 2406, Link 2 becomes disabled and all traffic is diverted to Link 3.

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

[0090] In another example, if the state is maintained at the STA level, multilink operation is possible with minor changes. For example, in step 2402, the associated STA is in state 2 instead of the corresponding MLD. The non-AP MLD only requests that links 2 and 3 be enabled, but includes information for all three links (i.e., capability information).

[0091] AP MLD considers setting up all three links and decides to do so. Therefore, 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 includes a TID-link mapping element that maps all TIDs to links 2 and 3 only, and no TID is mapped to link 1. In this case, at 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, while link 1 is in the Setup state. AP MLD records the parameters of all links (1-3), and all conventional procedures related to the association (such as AID assignment) are performed for all links. However, private key generation / distribution is performed only for the Enabled links. Alternatively, it is possible to consider only the associated STA corresponding to the Enabled link as associated (i.e., state 3), and not the associated STA corresponding to any other link (i.e., state 1 or state 2). Parameters for all links (1-3) are recorded by AP MLD, but all conventional procedures related to the association (such as AID assignment) and the generation / distribution of private keys are performed only for the Enabled link.

[0092] After a while, the AP MLD recognizes 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 because the link quality remains below the required threshold for a period longer than a specific timeout period, the AP decides to disable this link by performing a TID-link mapping that does not map a TID to Link 2. As a result, in step 2406, Link 2 becomes disabled, and all traffic is diverted to Link 3.

[0093] In addition to step 2408 as described in the previous example, when AP MLD receives a request to enable the link for the first time, it can also perform association-related procedures (such as AID assignment) and distribute the private key if they were not done in step 2404. Subsequent activation / deactivation can be done via TID-link mapping without requiring this procedure.

[0094] Figure 25 shows schematic diagrams of the MLD 2500 in various embodiments. The MLD 2500 includes MAC-SAP 2502 for accessing the Distribution Service (DS) via control and non-control ports, optional IEEE 802.1X port control and non-control filtering, a link activity monitoring module 2504, a link quality assessment module 2506, and a link status 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 understood 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] Figure 26 shows a flowchart 2600 illustrating communication methods according to various embodiments. In step 2602, a request frame is generated in a first STA included in a first plurality of STAs belonging to a first MLD, and this request frame contains request information. In step 2604, the request frame is sent to a second STA to request a multilink setup, the second STA included in a second plurality of STAs belonging to a second MLD, and the multilink setup establishes one or more links between one or more STAs from the first plurality of STAs and one or more corresponding STAs from the second plurality of STAs based on the request information.

[0096] Figure 27 shows a partially framed schematic diagram of the STA 2700 that can be implemented for multilink setup and link maintenance according to the first to third embodiments. The STA 2700 can be implemented as an STA or AP included in multiple STAs or APs belonging to AP MLDs or non-AP MLDs according to various embodiments.

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

[0098] As shown in Figure 27, the STA 2700 may include a circuit 2714, at least one radio transmitter 2702, at least one radio receiver 2704, and multiple antennas 2712 (for simplicity, only one antenna is depicted in Figure 27 for illustrative purposes). The circuit may include at least one controller 2706, which is used to perform tasks designed to be performed, including controlling communication with one or more other multilink devices in a MIMO radio network, with the assistance of software and hardware. The at least one controller 2706 may control at least one transmit signal generator 2708 for generating multi-link action frames to be transmitted to one or more other STAs or MLDs via at least one radio transmitter 2702, and at least one receive signal processor 2710 for processing multi-link action frames received from one or more other STAs or MLDs via at least one radio receiver 2704. At least one transmit signal generator 2708 and at least one receive signal processor 2710 can be a standalone module of the STA 2700 communicating with at least one controller 2706 for the functions described above. 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 depending on the actual needs and / or requirements. Data processing devices, storage devices, and other related control devices can be provided on a suitable circuit board and / or chipset.

[0099] In various embodiments, at least one radio transmitter 2702, at least one radio receiver 2704, and at least one antenna 2712 can be controlled by at least one controller 2706 during operation. Furthermore, although only one radio transmitter 2702 is shown, it will be understood that multiple such transmitters may exist.

[0100] In various embodiments, during operation, at least one radio receiver 2704, together with at least one received signal processor 2710, forms a receiver of the STA 2700. The receiver of the STA 2700 provides the functions necessary for multilink communication during operation. Although only one radio receiver 2704 is shown, it will be understood that multiple such receivers may exist.

[0101] STA 2700 provides the functions necessary for multilink setup and link maintenance during operation. STA 2700 may be, for example, a first STA included in a first plurality of STAs belonging to a first MLD. Circuit 2714 can generate a request frame during operation, the request frame containing request information. Radio transmitter 2702 can send a request frame to a second STA to request multilink setup during operation, the second STA being included in a second plurality of STAs belonging to a second MLD, and the multilink setup establishes one or more links between one or more STAs from the first plurality of STAs and corresponding one or more STAs from the second plurality of STAs based on the request information.

[0102] The request information can identify one or more STAs from the first plurality of STAs. The request frame may further include information about the quality of each radio channel of one or more links. The first plurality of STAs may be configured to collect information about the quality of each radio channel of one or more links before transmitting the request frame, and the radio channel quality may include one or more of the link margin, path loss, received signal strength indicator (RSSI), and received channel power indicator (RCPI). The request information may further include information about the radio channel quality of multiple links that can be set up between the first plurality of STAs and the second plurality of STAs, and the radio channel quality is set to implicitly indicate 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, STA 2700 may be a second STA included in a second plurality of STAs belonging to a second multilink device (MLD). When operating, the radio receiver 2704 can receive a request frame from the first STA, the first STA being included in a first plurality of STAs belonging to the first MLD, and the request frame contains request information, requesting a multilink setup to establish one or more links between one or more STAs from the first plurality of STAs and one or more corresponding STAs from the second plurality of STAs based on the request information. The radio transmitter 2702 can send a response frame to the first STA to notify it of the result of the multilink setup, the response frame conveying information about one or more links established between one or more STAs from the first plurality of STAs and one or more corresponding STAs from the second plurality of STAs.

[0104] Request information can identify one or more STAs from a first plurality of STAs. Information for one or more links may include operational parameters for one or more links and capability information for one or more STAs from a second plurality of STAs corresponding to one or more links. Response frames may further include information on traffic identifiers (TIDs) mapped to each of the one or more links, and the first plurality of STAs are permitted to transmit only frames belonging to the one or more TIDs mapped to the link on each link. Request information may include information on the radio channel quality of one or more links, and the second MLD is configured to decide whether or not to establish one or more links based on this information. Response frames may further include information related to the block ACK parameters of the established links. The second MLD may be an AP MLD, and the first MLD may be a non-AP MLD, and STAs included in the second plurality of STAs may transmit a frame containing information on a common MAC address identifying the AP MLD in order to advertise the AP MLD, and the frame may be either a beacon frame or a probe response frame. An STA included in a second set of STAs may send a frame indicating the AP in the second set of STAs that is the destination of the request frame in order to advertise the AP MLD, and that frame may be either a beacon frame or a probe response frame.

[0105] This disclosure can be implemented by software, hardware, or software working in conjunction with hardware. Each functional block used in the description of each embodiment above can be implemented 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 combination of LSIs. The LSI may be formed as individual chips, or it may form a single chip that includes some or all of the functional blocks. The LSI may include data input / output units coupled to it. The LSI referred to herein may be called an IC, system LSI, super LSI, or ultra LSI depending on the degree of integration. However, the technology for implementing the integrated circuit is not limited to LSIs and may be implemented using dedicated circuits, general-purpose processors, or special-purpose processors. Furthermore, a Field Programmable Gate Array (FPGA) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can change the connections and settings of circuit cells located inside the LSI may be used. This disclosure can be implemented as digital or analog processing. Advances in semiconductor technology and other derivative technologies mean that if future integrated circuit technology is replaced by LSIs, it will also be possible to integrate functional blocks using that future integrated circuit technology. Biotechnology can also be applied.

[0106] This disclosure can be implemented by any type of device, apparatus, or system having communication capabilities, referred to as a communication device.

[0107] A communication device may comprise a transceiver and a processing / control circuit. The transceiver may comprise a receiver and a transmitter, and / or may function as both a receiver and a transmitter. A transceiver acting as both 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-exclusive examples of such communication devices include telephones (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, smartwatches, tracking devices), game consoles, e-readers, telemedicine / telemedicine devices, vehicles providing communication capabilities (e.g., automobiles, airplanes, ships), and various combinations thereof.

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

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

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

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

[0113] A non-exclusive example of a station is a station that is part of a first group of stations belonging to a multilink station logical entity (i.e., an MLD), where the stations of the first group of stations share a common medium access control (MAC) data services interface to the upper layer, and the common MAC data services interface is associated with a common MAC address or traffic identifier (TID).

[0114] Therefore, embodiments of the present disclosure can be understood to provide communication devices and communication methods that operate on multiple links in order to fully realize the throughput gain of multilink communication, particularly in secure retransmission of multilinks.

[0115] While the detailed description of this embodiment so far has presented exemplary embodiments, it should be understood that a vast number of variations exist. Furthermore, it should be understood that the exemplary embodiments are examples and are not intended to limit in any way the scope, applicability, operation, or configuration of this disclosure. Rather, the detailed description so far provides a useful guide for carrying out the exemplary embodiments. It should be understood that the function and organization of the steps and methods of operation described in the exemplary embodiments, and the modules and structures of the devices described in the exemplary embodiments, can be modified in various ways without departing from the scope of the subject matter set forth in the appended claims.

[0116] For example, there exists a second STA included in a second plurality of STAs belonging to a second multilink 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 a first plurality of STAs belonging to a first MLD, and the request frame includes request information, which, based on the request information, requests a multilink setup to establish one or more links between one or more STAs from the first plurality of STAs and one or more corresponding STAs from the second plurality of STAs; and a transmitter that, in operation, sends a response frame to the first STA to notify the result of the multilink setup, the response frame conveying information about one or more links established between one or more STAs from the first plurality of STAs and one or more corresponding STAs from the second plurality of STAs.

[0117] A second STA, by example, in which the requested information identifies one or more STAs from a first set of multiple STAs.

[0118] A second STA, for example, in which the information of one or more links includes the operating parameters of one or more links and capability information of one or more STAs from a second group of STAs corresponding to one or more links.

[0119] A second STA, for example, wherein the response frame further includes information about traffic identifiers (TIDs) mapped to each of one or more links, and the first multiple STAs are permitted to transmit only frames on each link that belong to one or more TIDs mapped to the link.

[0120] A second STA, in one example, is configured such that the request information includes information about the quality of radio channels for one or more links, and the second MLD decides, based on this information, whether or not to establish one or more links.

[0121] A second STA, as an example, in which the response frame further includes information related to the block ACK parameters of the established link.

[0122] The second MLD is AP MLD, and the first MLD is non-AP MLD. A frame containing information about a common MAC address that identifies the AP MLD is sent by an STA included in a second group of STAs to advertise the AP MLD, and the frame is either a beacon frame or a probe response frame. A second STA based on one example.

[0123] To advertise the AP MLD, a frame indicating the AP among a second set of STAs, which is the destination of the request frame, is sent by an STA included in the second set of STAs, where the frame is either a beacon frame or a probe response frame, for example, in the second STA.

Claims

1. A receiving unit receives an association request frame from a non-access point multilink device (non-AP MLD) which includes information for identifying one or more links requested for multilink setup and link-specific information for the one or more requested links. A control unit that determines whether to accept each of the one or more requested links based on the link-specific information, A transmission unit that transmits an association response frame indicating a link accepted by the control unit, Equipped with, The association request frame includes an MLD MAC address field for indicating the MAC address of the non-AP MLD, AP MLD.

2. The association request frame includes a multilink element containing one or more link information fields, each link information field containing information to identify one of the requested one or more links and link-specific information. The AP MLD according to claim 1.

3. The link-specific information includes parameters necessary for establishing the requested link. The AP MLD according to claim 1.

4. Prior to the multilink setup, the receiving unit receives an authentication frame containing the MAC address of the non-AP MLD, and the transmitting unit transmits an authentication response frame. The AP MLD according to claim 1.

5. The receiving unit receives 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 AP MLD according to claim 1.

6. The receiving unit receives the association request frame on one link that the non-AP MLD wishes to use as part of the multilink setup. The AP MLD according to claim 1.

7. The association response frame is transmitted on the link that received the association request frame. The AP MLD according to claim 1.

8. The non-AP MLD has multiple associated terminals (STAs), the AP MLD has multiple associated access points (APs), and a multilink is set up between the multiple associated STAs and the multiple associated access point APs on different frequency bands. The AP MLD according to claim 1.

9. A communication method for an access point multilink device (AP MLD), An association request frame is received from a non-access point multilink device (non-AP MLD) which includes information to identify one or more links requested for multilink setup and link-specific information for the one or more requested links. Based on the link-specific information, a decision is made as to whether to accept each of the one or more links requested. Send an association response frame indicating the accepted link, The association request frame includes an MLD MAC address field for indicating the MAC address of the non-AP MLD, Communication method.

10. The association request frame includes a multilink element containing one or more link information fields, each link information field containing information to identify one of the requested one or more links and link-specific information. The communication method according to claim 9.

11. The link-specific information includes parameters necessary for establishing the requested link. The communication method according to claim 9.

12. Prior to the multilink setup, the system receives an authentication frame containing the MAC address of the non-AP MLD and sends an authentication response frame. The communication method according to claim 9.

13. Receiving a re-setup request frame to establish 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 9.

14. The non-AP MLD receives the association request frame on one link that it wishes to use as part of the multilink setup. The communication method according to claim 9.

15. The association response frame is transmitted on the link that received the association request frame. The communication method according to claim 9.

16. The non-AP MLD has multiple associated terminals (STAs), the AP MLD has multiple associated access points (APs), and a multilink is set up between the multiple associated STAs and the multiple associated access point APs on different frequency bands. The communication method according to claim 9.

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