Communication apparatus and communication method for multi-link 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 functions 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 problems related to communication devices and problems related to access points to which communication devices connect wirelessly.

[0003] The Institute of Electrical and Electronics Engineers (IEEE) 802.11 group 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 communication. Multi-channel aggregation across multiple links is a natural way to increase the throughput of communication data several times.

Summary of the Invention

Problems to be Solved by the Invention

[0004] To enable such multi-link operation between an access point (AP) multi-link device (MLD) and a non-AP MLD, it is necessary to establish 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] A non-limiting and exemplary embodiment promotes providing a first station (STA) included in a first plurality of STAs belonging to a first multi-link device (MLD), the first STA including a circuit that generates a request frame during operation, the request frame including request information, and a transmitter that transmits the request frame to a second STA to request a multi-link setup during operation, the second STA being included in a second plurality of STAs belonging to a second MLD, and the multi-link setup establishing one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information.

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

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

[0008] Note that general or specific embodiments may be implemented as a system, method, integrated circuit, computer program, storage medium, or any optional combination thereof. Further benefits and advantages of the disclosed embodiments will become apparent from the present specification and the drawings. Benefits and / or advantages can be obtained individually by various embodiments and features of the present specification and the drawings, and not all are provided to obtain one or more of such benefits and / or advantages.

Brief Description of the Drawings

[0009] The accompanying drawings are incorporated herein and constitute a part of this specification together with the following detailed description, illustrate various embodiments, and serve to explain various principles and advantages according to the present embodiments. Throughout the separate drawings, similar reference numerals refer to the same or functionally similar elements.

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[0010] Those skilled in the art will understand that the elements in the figures are shown for the 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 in nature 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. Further, 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 AP MLD and non-AP MLD is completed, the link can be in one of the following states. - Setup (or established): The AP MLD and the non-AP MLD have all the information necessary to enable data operations with each other. This state corresponds to state 3 in the state transition diagram of a non-mesh STA, where the IEEE 802.1X control port is blocked (i.e., only EAPOL (Extensible Authentication Protocol over LANs) data frames are permitted, and other data frames are not permitted). - Enabled (activated): Both MLDs have agreed to start data operations on the link. For example, at least one traffic identifier (TID) is mapped to the link, and RSNA (Robust Security Network Association) for the link is complete. This state corresponds to state 4 in the state transition diagram of a non-mesh STA, where the IEEE 802.1X control port is unblocked (i.e., all data frames are permitted). - Disabled: In this state, the link may be set up but data operations are disabled, or the setup and RSNA are complete but no TID is mapped to the link, or the MLD ignores frames received on the link.

[0013] It is important to clarify how the MLD maintains the link state and define the rules for permitted / non-permitted frames and related MLD operations for each link state.

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

[0015] In fact, just the link capabilities of the non-AP MLD may not be able to provide sufficient information for setting up a link. Among the (potential) links / STAs of the MLD, there may be a fourth state (i.e., non-setup (not established / unusable)) after the completion of the multi-link setup procedure. Thus, frame exchange is not possible on that link. However, such a link may become setup-capable if the conditions change (e.g., a non-MLD moves close to the AP MLD).

[0016] Therefore, links should not be set up or established based on capability information only. The non-AP MLD should be able to select which links are set up. Also, the channel quality of links (especially the second and subsequent links) needs to be checked before establishing / enabling the links (checked during the multi-link setup itself or during subsequent enabling operations). Furthermore, the channel quality of enabled links needs to be checked periodically to confirm that the links are alive and suitable for the TIDs mapped to the links.

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

[0018] Figure 2 shows the communication flow between the AP MLD 202 and the non-AP MLD 204 for multi-link setup, link quality evaluation, mapping of traffic identifiers (TIDs) to links, and subsequent communication, according to a typical solution to address the above-described problems. During multi-link setup, a multi-link setup request 206 is sent from the non-AP MLD 204 to the AP MLD 202 on link 2. The multi-link setup request includes information regarding the link capabilities of links 1, 2, 3. In response to this request, the AP MLD 202 sets up the requested links 1, 2, 3 and then sends a multi-link setup response 208 notifying the non-AP MLD 204 of the link setup. At 210, the non-AP MLD 204 is authenticated / associated, and thus three links are set up. Then, a multi-link RSNA (4-way handshake / group key handshake) between the AP MLD 202 and the non-AP MLD 204 is performed on link 2. Note that each of links 1, 2, 3 connects the associated STA of the AP MLD 202 and the associated STA of the non-AP MLD 204, and thus it will be understood that these STAs can transmit or receive any data or frames on the corresponding link.

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

[0020] Thereafter, the AP MLD 202 can start the TID-link mapping by determining the TIDs mapped to each link based on the link quality evaluation and sending a TID-link mapping request 222 to the non-AP MLD 204 on link 2. The TID-link mapping request contains a TID map indicating how each TID is mapped to each link. In response to this, the non-AP MLD 204 sends a TID-link mapping response 224 to the AP MLD 202 on link 2 to indicate the status of the TID mapping. After all three links are enabled and the TIDs are mapped to the links (226), frame exchange can be performed on any / all of the three links (228).

[0021] The above solution has several drawbacks. For example, the links are set up based only on the capability information (i.e., included in the multi-link setup request 206). Furthermore, this is an AP-centric solution, i.e., 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 for the exchange of multi-link setup frames) should not be set up (established) based on capability information alone. The first MLD can request the second MLD as part of the multi-link setup, using, for example, the setup request field of the multi-link setup request frame, which links are to be set up, regardless of the capabilities of the links. The MLD can also include information regarding the link quality of the requested links (e.g., uplink / downlink (UL / DL) link margin, UL / DL path loss, etc.). Further, the second MLD sets up only the links requested by the first MLD during multi-link setup (e.g., assignment of an association identifier (AID), insertion into an association record, etc.). The set-up links may be referred to as a multi-link set. The second MLD can also consider information regarding link quality in order to determine whether to set up / enable a link, especially when there are TID restrictions on some links. This information can also be used for subsequent TID-link mapping (i.e., enabling / disabling of links).

[0023] Figure 3 shows an illustration 300 of an AP MLD 302 having a plurality of BSSs and non-AP MLDs 304, 306, 308 within the range of the BSSs, according to various embodiments. The AP MLD 302 can be shown as a schematic diagram 314 including a MAC-service access point (MAC-SAP) for accessing a distribution service (DS), an MLD MAC address for identifying the AP MLD, and three associated APs (i.e., AP1, AP2, and AP3). Each AP has its own STA MAC address in the MAC layer and is connected via a link in the physical layer for transmitting and receiving data (i.e., AP1 is connected via link 1, AP2 is connected via link 2, and AP3 is connected via link 3).

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

[0025] AP MLD 302 sets up multiple (multi-link) BSSs (one BSS per associated AP). Each BSS has its own BSSID and beacon and can have different coverage. For example, AP1 operates the BSS at 6 GHz, AP2 operates the BSS at 5 GHz, and AP3 operates the BSS at 2.4 GHz. The coverage of different APs can be different (due to factors such as frequency band, transmit (Tx) power, etc.). Coverage may also depend on the modulation and coding scheme (MCS), i.e., MCS 0 may have much larger coverage compared to MCS 9. Further, 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] AP MLD is an entity with a distribution system access function (DSAF), and the DSAF enables access to the DS via the wireless medium (WM) for associated non-AP MLDs (having one or more associated STAs) and legacy STAs. Different associated STAs of non-AP MLDs can connect to different APs of AP MLD to obtain access to the DS. However, all APs of AP MLD can connect to the DS via the same single MAC-SAP and DSAF.

[0027] This network forms an Extended Service Set (ESS) 400 shown in FIG. 4. STAs STA1, STA2, and STA3 belonging to non-AP MLD 1 can, for example, connect to APs AP1, AP2, and AP3 of AP MLD 1 respectively to obtain access to the DS. APs AP1, AP2, and AP3 can connect to the DS via the MAC-SAP and DSAF of AP MLD 1. Further, STAs STA4, STA5, and STA6 belonging to non-AP MLD 2 can, for example, connect to APs AP4, AP5, and AP6 of AP MLD 2 respectively to obtain access to the DS. APs AP4, AP5, and AP6 can connect to the DS via the MAC-SAP and DSAF of AP MLD 2. Conventionally, a legacy STA such as STA7 obtains access to the DS by associating with an AP, and can also continue access by associating with any one of the associated APs of the AP MLD (for example, AP4 of AP MLD 2). However, in the case of non-AP MLD, the association process can be replaced by a multi-link setup procedure, as will be further explained later. The multi-link setup executed between any one set of associated STA and associated AP can provide access to the DS to one or more associated STAs of the non-AP MLD.

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

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

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

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

[0032] After the completion of the multi-link setup, the AP MLD 502 can start the TID-link mapping by, for example, sending the TID-link mapping request 522 on link 2 to the non-AP MLD 504. The TID-link mapping request 522 can include a TID map for the requested links 1, 2, 3 indicating how each TID is mapped to each link. In response, the non-AP MLD 504 can send a TID-link mapping response 524 on link 2 to the AP MLD 502 to indicate the status of the TID mapping. After all three links are enabled and TIDs are mapped to the links (526), frame exchange can be performed on any / all of the three links (528). After the TID-link mapping is completed in 526, the multi-link state of the non-AP MLD can change to state 4. The TID-link mapping can be optional or the initial mapping can be performed as part of the multi-link setup step. By default, all TIDs are mapped to all the configured links.

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

[0034] For the multi-link operation shown in FIG. 5, a new (class 1) action frame can be defined. FIG. 6 shows an illustration of a new multi-link action frame 600 according to the first embodiment. The multi-link action frame 600 can include a frame control field, a duration field, three address fields, a sequence control field, an HT control field, a category field, a multi-link action field, a variable field, and a frame check sequence (FCS) field. The multi-link action field can have a value of 0 indicating that the action frame is targeted at multi-link setup, or a value of 1 indicating that the action frame is targeted at multi-link tear-down. Values 2 to 255 can be reserved.

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

[0036] FIG. 8 illustrates a Multi-link element 800 according to the first embodiment. The Multi-link element 800 can 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 conveyed in a multi-link action frame 600, or in other frames such as an Association Request / Response frame or another management frame. When multiple multi-link operations (e.g., TID mapping and BA setup, or multi-link setup and TID mapping) are signaled in the same frame exchange, multiple Multi-link elements can be conveyed in the same frame. The operation is signaled by the value indicated in the Action Type field of the Multi-link element 800. The value 0 can indicate multi-link authentication, the value 1 can indicate a multi-link setup request, the value 2 can indicate a multi-link setup response, the value 3 can indicate a TID-link mapping request, the value 4 can indicate a TID-link mapping response, the value 5 can indicate a Block ACK setting request, and the value 6 can indicate a Block ACK setting response. Other values 7 to 255 can be reserved.

[0037] FIG. 9 illustrates a Multi-link Teardown frame 900 according to the first embodiment. The Multi-link Teardown frame 900 can include a Frame Control field, a Duration field, three Address fields, a Sequence Control field, an HT control field, a Category field, a Multi-link Action field 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 link addition / removal request / response).

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

[0040] The AP MLD 502 can estimate the UL path loss and the UL link margin based on the transmit power indicated in the TPC Request element of the received probe request frame, and include this information in the probe response frame 508 transmitted to the non-AP MLD 504 in each multi-link BSS (i.e., in the modified TPC report element). FIG. 11 shows an illustration of the TPC Report element 1100 according to the first embodiment. The TPC Report element 1100 can include an Element ID field, a Length field, a Transmit Power field, a Link Margin field, and a Path Loss field. The Transmit Power field can be set to the transmit power used for the host frame (i.e., the probe response frame 508). The link margin is the difference between the received power (dBm) and the receive 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 the absence of a link margin. The path loss is the difference between the transmit power of the frame carrying the TPC Request element, such as the probe request frame, and the received power received from the non-AP MLD. The Path Loss field is encoded as a two's complement signed integer in decibels and can be set to 128 to indicate the absence of a path loss. The Link Margin field is set to the UL link margin estimated by the AP MLD 502, and the Path Loss field is set to the UL path loss estimated by the AP MLD 502.

[0041] When the non-AP MLD 504 receives the probe response frame 508, it can calculate the DL path loss using the transmission power information in the TPC Report element, while on the other hand, it can calculate the DL link margin based on the received power. The non-AP MLD 504 can use the link margin and path loss information to estimate the UL / DL link quality of each BSS (link). Alternatively, when the link measurement request / report frame is reclassified as a class 1 frame for non-DMG / 11be STAs, similar information can be realized 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 multi-link capability element) so that it can be used during multi-link authentication (SAE, FILS) and multi-link setup. If not advertised, the probe request frame needs to request to indicate the MAC address of the AP MLD. Note that although the link measurement request / response frame was mentioned as an alternative, it will be understood that any other suitable management frame may be used for this purpose. Additionally, the results of the sounding procedure (e.g., Channel Quality Index (CQI)) can also be used if available.

[0042] Upon successful authentication, the state of the legacy STA changes to state 2. In the case of MLD, the state can be maintained at the MLD level (instead of the STA level). In the case of open system authentication (e.g., EAP), two authentication frames are exchanged between two MLDs. Existing authentication steps may be reused or completely omitted. In the case of SAE (authentication using a password), four authentication frames are exchanged between two MLDs, and the MLDs authenticate each other using a shared key (e.g., a password) and generate a pairwise master key (PMK). The MLD MAC address may be used instead of the link MAC address to initialize the STA-A-MAC value and STA-B-MAC value used to generate the secret password element (PWE). In the case of FILS authentication, two authentication frames are exchanged between 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 FIG. 5, although it is assumed that the non-AP MLD 504 discovers the MLD MAC address of the AP-MLD when a multi-link is discovered, for the purpose of enabling the AP MLD 502 to authenticate the non-AP MLD 504 and for the purpose of signaling to 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 (e.g., within the multi-link element). For this purpose, the multi-link element can be conveyed in the authentication frame (or multi-link setup frame). FIG. 12 shows an illustration of a multi-link element 1200 configured for multi-link authentication according to the first embodiment. The multi-link element 1200 includes the same fields as the multi-link element 800. However, the action type field is set to the value 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 a multi-link setup request / response frame may be used, or the authentication frame may be reused. Multi-link authentication is used to establish the identity of one MLD as a member of a set of MLDs permitted to associate with another MLD.

[0044] Figure 13 shows an illustration of a Multi-link element 1300 configured for a multi-link setup request according to the first embodiment. The Action Type field is set to a multi-link setup request (i.e., value 1). The Multi-link Parameters field can 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 can include information specific to the link, such as a Link MAC Address sub-field, a Link Capabilities sub-field, a Setup Requested sub-field, a UL Link Margin sub-field, a UL Path Loss sub-field, a DL Link Margin sub-field, and a DL Path Loss sub-field.

[0045] Referring to the multi-link setup of FIG. 5, the non-AP MLD 504 can explicitly request which link to establish by using the Setup Requested subfield of the multi-link element 1300. For example, the value 0 indicates that no setup is requested for the link, and the value 1 indicates that setup is requested. The non-AP MLD 504 can consider link quality information to determine the link for which the multi-link setup is requested. Other factors may also be considered. For example, the non-AP MLD 504 has the ability for a 2.4 GHz link (i.e., Link 1), but may choose not to request the setup of this link due to coexistence issues with its own Bluetooth radio, or may choose not to request the setup of a specific link for power saving or other reasons. Also, the non-AP MLD 504 can include information regarding the link quality of the requested link (e.g., UL / DL link margin, UL / DL path loss obtained at discovery, etc.). If link quality information is not available, the received signal strength indicator (RSSI) / received channel power indicator (RCPI) of the beacon / probe response frame received on the link can be included as an estimated value of the link quality. Also, if the result of the sounding procedure (e.g., channel quality indicator (CQI)) is available as link quality information, it may be used.

[0046] Also, the non-AP MLD 504 can include a field describing the traffic flow characteristics and QoS expectation values in the link. Further, 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 setup of the link is not requested. Advantageously, this enables the link to be set up based on the requests of the non-AP MLD and the link quality.

[0047] When the AP MLD 502 receives a multi-link setup request from the non-AP MLD 504, it performs setup of only the links requested by the non-AP MLD 504 (i.e., assignment of AID, insertion into the association record, etc.) and subsequent procedures (i.e., TID-link mapping, generation / distribution of security keys, etc.). The AP MLD 502 can use information regarding link quality to determine whether to set up / enable the requested links, especially when there are TID restrictions on some of the links. Also, this information can be used for subsequent TID-link mapping (i.e., enabling / disabling of links). The AP MLD 502 can maintain a table of the minimum link quality required for the non-AP MLD to use the links.

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

[0049] When traffic flow information (similar to the TSPEC element) is provided, the AP MLD can also use this information to determine whether to set up / enable specific requested links for non-AP MLDs. For example, the AP MLD can reject enabling the link mapped to TID 6,7 for a non-AP MLD that shows a large amount of traffic flow in TID 6,7 for the purpose of maintaining QoS requirements on the link. In some cases, the AP MLD can set up all the requested links and consider link quality only to determine whether to enable the links (e.g., at the first or subsequent TID-link mapping). In another case, the AP MLD can consider link quality when setting up the requested links as well.

[0050] AP MLD can include only the information of the established links in the multi-link setup response frame. FIG. 14C shows an illustration of a multi-link action frame 1400 configured for multi-link setup response and TID-link mapping according to the first embodiment. The multi-link action field of the multi-link action frame 1400 is set to multi-link setup (i.e., value 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., it is an action type field set to multi-link setup response and has one or more link information sub-fields (one for each established link). The multi-link element 1404, which is an action type field, is set to TID-link mapping request (i.e., set to value 3) and can include one or more link information fields (one for each established link) (similar to the multi-link elements 1300 and 1402). However, each of the one or more link information fields can include a link ID sub-field, a UL TID map, and a DL TID map. Each TID map can be a bitmap (i.e., 8 bits, 1 bit per TID) indicating the TIDs mapped to the links in that direction (UL or DL), or one or more 4-bit fields can be used to indicate the TIDs. An example of the encoding of the TID map based on the 4-bit field is shown in FIG. 14D and has values from 0 to 15.When the non-AP MLD receives a TID-link mapping request frame from the AP MLD, it can send back a TID-link mapping response frame indicating its commitment to the TID mapping. If the TID mapping is rejected, the default TID mapping can be applied to the link, or the AP MLD can disable the link for the non-AP MLD. In the multi-link setup action frame (or association response frame), it can be understood that two multi-link elements can be used to signal multi-link setup and TID-link mapping respectively, or they can be combined into one element.

[0051] Furthermore, not only can multi-link setup request / response frames be used for multi-link setup, but also association request / response frames (including multi-link elements) can be used for multi-link setup. When the multi-link setup is completed successfully, one or more non-AP STAs of the non-AP MLD can call the distribution system service through one or more AP STAs of the AP MLD.

[0052] For example, new MAC sublayer management entity (MLME) primitives for multi-link setup can be defined for use by the non-AP MLD or the AP MLD. The MLME primitives are used to pass information between the MLME and the station management entity (SME). The SME uses the services provided by the MLME via the MLME SAP. The primitives for requesting multi-link setup for the non-AP MLD are as follows.

Table 1

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

[0054] The primitive for the non-AP MLD to confirm the multi-link setup can be as follows.

Table 2

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

[0056] The non-AP MLD indicates that one or more links are available by invoking the MLME-MULTI-LINK-SETUP.confirm primitive. Thereby, it is signaled to the supplicant that the MAC of the MLD has transitioned to state 3. If the MLD negotiates to use IEEE 802.1X authentication during multi-link setup, the management entity of the MLD can respond to the MLME-MULTI-LINK-SETUP.confirm (or indication) primitive by requesting the supplicant (or authenticator) to start IEEE 802.1X authentication. In this case, the authentication is performed by the decision of the non-AP MLD to start multi-link setup and the decision of the AP MLD to approve the multi-link setup.

[0057] The primitive for indicating the reception of a multi-link setup request for the AP MLD can be as follows.

Table 3

[0058] This primitive can be generated when a multi-link setup request (Multi-link Setup Request) frame is received. PeerMLDAddress is set as the MLD MAC address of the peer MLD. One or more multi-link elements transmitted in the multi-link setup request (Multi-link Setup Request) frame are included.

[0059] The primitive for responding to a multi-link setup request for the AP MLD can be as follows.

Table 4

[0060] In this primitive, a multi-link setup response frame is sent to the peer MLD. The PeerMLDAddress is set as the MLD MAC address of the non-AP MLD, and the PeerLinkAddress is set as the MAC address of the associated STA of the peer MLD (for the link on which the multi-link setup response frame is sent). One or more multi-link elements can be included to convey the information necessary for the multi-link setup response.

[0061] Furthermore, the primitive that requests multi-link teardown (for both non-AP MLD and AP MLD) can be as follows.

Table 5

[0062] In this primitive, a multi-link teardown frame is sent. The PeerMLDAddress is set as the MLD MAC address of the peer MLD. Optionally, one or more link IDs can be included, and each link ID identifies the link to be torn down.

[0063] The non-AP MLD can request to add a new link by re-executing the multi-link setup. Link quality and traffic flow information can also be included. FIG. 15 shows an illustration 1500 of the communication flow between the AP MLD 1502 and the non-AP MLD 1504 including a multi-link reset setup request according to the first embodiment. At the time of multi-link setup, the AP MLD 1502 rejects the setup of Link 3 due to poor link quality. Therefore, only Link 1 and Link 2 are activated. Thereafter, the non-AP MLD 1504 can request the setup of Link 3 by transmitting a multi-link setup request 1506 including request information to the AP MLD 1502, for example, because the link quality of Link 3 has improved. The request information can include link capabilities, information identifying Link 3, and the link quality of Link 3. The AP MLD 1502 sets up the requested link based on the request information and transmits a multi-link setup response 1508 including information on the set-up link (i.e., Link 3) and the TID map of Link 3 to the non-AP MLD 1504. Authentication by the IEEE 802.1X server, PMKSA setting, etc. are not executed. Advantageously, this allows for flexible addition of new links with improved link quality.

[0064] Since the non-AP MLD 1504 is considered to have already been authenticated and associated with the AP MLD 1502 during the initial multi-link setup, the non-AP MLD 1504 only executes procedures related to the addition of the required new link (e.g., AID assignment for the new link, update of the link MAC address to the association record, TID-link mapping, etc.). Also, if necessary, security keys for the new link (i.e., pairwise temporal key (PTK), group temporal key / (integrity) group temporal key (GTK / IGTK: (Integrity) Group Temporal Key)) can be generated / distributed. If the same PTK is used for all activated links, a 4-way handshake is not required for the new link. If different GTK / IGTK are used for the new link, they can be distributed using the group key handshake. Alternatively, instead of reusing the multi-link setup, another signaling (e.g., multi-link link addition request / response) can be defined for this purpose.

[0065] When adding a new link, it may be necessary to change some parameters of the existing block ACK agreement for the TID mapped to the new link. For the existing block ACK agreement with the AP MLD as the source (i.e., in the DL flow), the AP MLD can also include the relevant block ACK parameters in the same frame that conveys the multi-link setup response. The non-AP MLD can also follow this by initiating an update of the block ACK parameters targeted at the TID mapped to the new link for the UL flow (piggybacked in the additional block acknowledgment (ADDBA) request frame or in another frame such as the TID-link mapping response frame).

[0066] FIG. 16 shows an illustration of a Multi-link Action frame 1600 configured for a multi-link setup response to add a new link according to the first embodiment. Similar to the multi-link action frame 1400, the multi-link action frame 1600 further includes a multi-link element (block ACK setting request) field 1602. The multi-link element field 1602 can include one or more link information fields, and each of the one or more link information fields includes a link ID field and one or more TID information fields. Further, the one or more TID information fields can 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 the multi-link action frame 1600, the non-AP MLD can send a TID-link mapping response frame to the transmitting AP MLD in response to the TID-link mapping request 1604. The TID-link mapping response frame can be a multi-link action frame that conveys a multi-link element with an action type set to a TID-link mapping response.

[0068] (Using TID - link mapping) Dynamically enabling / disabling a link may affect block ACK parameters (such as receive reordering buffer size, unified BA scoreboard size, etc.), and ADDBA renegotiation may be triggered each time a link is enabled / disabled. For example, when a new link is added, it is necessary to specify the BA scoreboard size, start sequence number, etc. for the new link. Also, the receiving - side MLD may need to increase the size of the receive (RX) reordering buffer so that it can receive additional frames from the added link.

[0069] Figure 17 shows the state transition diagram 1700 according to the first embodiment. The MLD can maintain an enumerated state variable (instead of maintaining the state between two associated STAs) for each MLD that needs to communicate directly with the WM through one or more links. For example, based on the 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), State 4 (authenticated, associated, RSNA established or not required). When authentication is successful, the state of the MLD changes from "State 1" to "State 2". When multi-link setup (where at least one link is required) is successful, the state of the MLD changes from State 2 to State 3. During multi-link setup, the security parameters are verified. An MLD that performs IEEE 802.1X authentication uses open system authentication. An MLD that performs password-based authentication can use SAE authentication. An MLD that performs FILS uses FILS authentication. SAE authentication and FILS authentication provide mutual authentication and the derivation of the PMK. If open system authentication is selected instead, the authenticator or supplicant starts IEEE 802.1X authentication. Before IEEE 802.1X authentication and key installation are completed, the IEEE 802.1X control port of the AP MLD blocks all data frames. The IEEE 802.1X non-control port is permitted to pass IEEE 802.1X frames between the supplicant and the authenticator. During the authentication process, an encryption key shared between the encryption endpoints is created, regardless of whether SAE authentication or FILS authentication using authentication frames is used, or IEEE 802.1X authentication using data frames post association is used. The encryption endpoints are the AP MLD and the non-AP MLD when SAE / FILS is used, and the IEEE 802.1X AS (authentication server) and the non-AP MLD when IEEE Std 802.1X is used.When using IEEE Std 802.1X, the AS transfers these keys to the AP MLD, and the AP MLD and non-AP MLD use one of the key confirmation handshakes (e.g., a 4-way handshake over either link or an FT 4-way handshake) to complete the establishment of the security association. When using SAE authentication, the AS does not exist and thus no key transfer occurs. The 4-way handshake is performed directly between the AP MLD and the non-AP MLD. The key confirmation handshake indicates that the link is secured by the key and is ready to permit normal data traffic and protected robust management frames. When FILS authentication is performed, key confirmation is performed as part of the FILS exchange using the association frame. Thus, no additional handshake is required. If the key confirmation handshake is completed for at least one link, the IEEE 802.1X control port is considered unblocked for the non-AP MLD. After a multi-link tear-down, the IEEE 802.1X control port returns to the unauthenticated state and blocks all data frames.

[0070] Furthermore, the link state is maintained per (pair of associated STAs) / link and can take one of the following four states. - Not Setup (Unestablished / Unavailable): The AP MLD and non-AP MLD do not have all the information necessary to enable data operations with each other. The permitted frames depend on the state of the MLD. Data frames are not permitted. Access to the DS is not permitted. - Setup (Established): The AP MLD and non-AP MLD have all the information necessary to enable data operations with each other. Data frames (except EAPOL frames) are not permitted. Access to the DS is not permitted. - Enabled (Activated): Both MLDs have agreed to start data operations on the link. For example, at least one TID is mapped to the link, and a security association (RSNA) for the link is complete. All frames permitted by the TID mapping are permitted. Access to the DS is permitted. - Disabled (Deactivated): Data frames (except EAPOL frames) are not permitted. Non-data frames may be permitted. Access to the DS is not permitted.

[0071] In the case of a legacy STA or non-MLD STA, the normal authentication / association process can be used, and the state is maintained at the STA level. A unique pair of IEEE 802.1X ports is created by the multi-link setup between pairs of MLDs, and authentication is performed only for these ports. Basically, in the case of MLDs, the roles of the authenticator and supplicant can be implemented at the MLD level rather than at the STA level.

[0072] When the STA / link is in the Not Setup state, even if the IEEE 802.1X control port is unblocked at the MLD level, data frames other than EAPOL are not permitted for that link. When multi-link setup (link is requested) is successful, the state of the link changes from Not Setup to Setup. When the 4-way / group key handshake + TID-link mapping (at least one TID is mapped to the link) is successful, the state of the link changes from Setup to Enabled. When the mapping of TID to the link is successful, the state toggles between Enabled and Disabled. When multi-link teardown is performed, the state of MLD becomes state 1 and all related STA / links become in the Not Setup state. Further, while no TID is mapped to the STA / link in both the Setup state and the Disabled state, the security key may not be generated for the STA / link in the Setup state. On the other hand, in the Disabled state, the security key is generated for the STA / link. However, in any state where no TID is mapped to the link, even if the IEEE 802.1X control port is unblocked, the AP cannot transfer data frames from the link to the DS.

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

[0074] According to the first embodiment, the MLD can also maintain a record of the link quality of all valid links based on link quality measurement values such as the signal noise ratio (SNR), packet error ratio (PER), and RSSI. FIG. 19 shows an illustration of how link maintenance is performed according to the first embodiment. For a link where transmission is active, the link quality can be measured based on the transmitted / received frames. For an inactive link (awake power save state), a management frame (i.e., a response type / non-response type link measurement frame) can be transmitted periodically (i.e., once per beacon interval) to access the link quality. If the link quality falls below a specific threshold, that link can be considered "Down". In a "Down" link, data frames are not permitted, or can be transmitted at a lower MCS. The threshold can depend on the TID mapped to the link, the MCS requirements of the link, etc. On the other hand, if the link quality is improved from the threshold, that link can be reused as a normal valid link. However, if the link quality continues to be below the threshold over a specific TIMEOUT period, that link can be invalidated (by TID-link mapping). Advantageously, this allows links to be set up based on link quality.

[0075] According to the second embodiment, the non-AP MLD can implicitly signal the links to be set up during multi-link setup by including only the information of the links to be requested to set up (i.e., link capabilities, MAC addresses, etc.). The information of the links not requested to be set up is not included in the multi-link setup request. For example, the setup request can include the capability information and the information indicating the MAC address of only the associated STAs of the non-AP MLD for which the link is to be set up. This can be used as the default option for requesting to set up the link. Alternatively, by providing link information but setting a very low link quality value (i.e., setting the path loss of the link to the maximum value (e.g., 128) for either or both of UL / DL, or setting the link margin to the minimum value (e.g., -128)), the request not to set up the link is implicitly signaled. For example, the setup request can include information regarding the quality of the wireless channels of the plurality of links that can be set up between the first plurality of STAs and the second plurality of STAs, and the quality of the wireless channels is 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 multi-link setup request, the AP MLD can start a link quality evaluation of the requested links including / excluding the link on which the multi-link request was received before sending the multi-link setup response, and can determine whether to set up the links. FIG. 20 shows a communication flow 2000 between an AP MLD 2002 and a non-AP MLD 2004 including a link quality evaluation step according to a second embodiment. After the non-AP MLD 2004 starts a multi-link setup by sending a multi-link request to the AP MLD on link 2 to request setup of links 1, 2, and 3, the AP MLD 2002 starts a link quality evaluation by sending link measurement requests 2006 and 2010 at links 3 and 1 respectively (before sending the multi-link setup response). In this example, in the link quality evaluation of the requested links, the link on which the multi-link request was received (i.e., link 2) is excluded, but the AP MLD may choose to include that link as well. In response to the link measurement requests, the non-AP MLD 2004 sends a link measurement report 2008 on link 3 (in response to link measurement request 2006) and a link measurement report 2012 on link 1 (in response to link measurement request 2010) to the AP MLD 2002. The AP MLD determines to set up / establish only links 1 and 2 (in 2014) based on the collected link quality information provided by the link measurement reports 2008 and 2012. Link 3 is rejected. Thus, the AP MLD 2002 sends a multi-link setup response indicating that links 1 and 2 are set up.

[0077] AP MLD 2002 can use information regarding link quality to determine whether to set up / enable the requested links, especially when there are TID restrictions on some of the links. However, the link quality assessment needs to be done such that the multi-link setup can be performed within the timeout value range associated with the setup. Further, while the example shown in Figure 20 shows 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 the state transition diagram 2100, alternative states of MLD are assumed, and these states are maintained at each relevant STA level of MLD, similar to the legacy STA. Also, the roles of the authenticator and the supplicant are implemented at the STA level (rather than at the MLD level). This version of the state machine is possible in SAE authentication and FILS authentication, i.e., IEEE 802.1X authentication is not used. At the same time, 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 the STA / link is in the Not Setup state, data frames are not permitted on that link. Upon successful (multi-link) authentication, at 2104, the state of all associated STAs (i.e., STA1 and STA2) becomes state 2. However, the state of the excluded associated STA remains in state 1. Upon successful multi-link setup (where the link is requested), the state of the link changes from Not Setup to Setup, and the state of the corresponding associated STA changes to state 3. The unrequested link remains in the Not Setup state, and the state of the corresponding associated STA remains in state 1 or state 2. For example, after a successful multi-link setup requested for link 1 (corresponding to STA1), at 2106, STA1 is in state 3 and STA2 is still in state 2. When the 4-way / group key handshake + TID-link mapping (where at least one TID is mapped to the link) is successful, the state of the link changes from Setup to Enabled, and the state of the corresponding associated STA changes to state 4. For example, at 2108 after a successful 4-way / group key handshake + TID-link mapping (where 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. When a successful multi-link re-setup is requested for link 2, at 2110, STA2 changes from state 2 to state 3 (i.e., link 2 is set up). When the TID-link mapping is successful, the state of the link toggles between Enabled and Disabled, but the state of the associated STA does not change.For example, after the TID-link mapping is successful (from 2110, one or more TIDs are mapped to Link 2, but no TID is mapped to Link 1) and the 4-way / group key handshake for Link 2 is successful at 2114, STA1 is in state 4 even though Link 1 is invalid, and STA2 enters state 4 and Link 2 is valid. Alternatively, these state changes can also occur at 2114 after the multi-link re-setup is successful (i.e., Link 2 is requested) from 2108, the TID-link mapping is successful (one or more TIDs are mapped to Link 2, but no TID is mapped to Link 1), and the 4-way / group key handshake for Link 2 is successful. Further, at 2116 after the TID-link mapping is successful (one or more TIDs are mapped to Link 1, but no TID is mapped to Link 2) from 2114, both STA1 and STA2 are in state 4, Link 2 is valid, and Link 1 is invalid. Also, from 2116, it is possible to return to 2114 due to the success of the TID-link mapping where one or more TIDs are mapped to Link 2 but no TID is mapped to Link 1. Further, due to the multi-link teardown, the states of all related STAs become state 1, and all links become in the Not Setup state, i.e., return to 2102.

[0080] In this example, the difference between Setup and Disabled is that in both cases, no TID is mapped to the link. In the Setup state, a security key may not be generated for the STA / link, but in the Disabled state, a security key is generated for the STA / link. However, in neither state is a TID mapped to the link, and the AP cannot transfer data frames from the link to the DS.

[0081] According to the second embodiment, the non-AP MLD can request which link to delete as part of the multi-link setup (i.e., explicitly by using the Deletion Requested field of the Multi-link Setup Request element or implicitly by indicating low channel quality). The non-AP MLD can also include information regarding the link quality of the link requested to be deleted (i.e., UL / DL link margin, UL / DL path loss, etc. obtained at discovery). If link quality information is not available, the RSSI / RCPI of the beacon / probe response frame received on the link can be included as an estimated value of the link quality. The non-AP MLD can determine which link deletion to request considering the link quality information. Other factors may also be considered. For example, the non-AP MLD may choose to request deletion of a 2.4GHz link due to coexistence issues with its own Bluetooth radio, etc., or may choose not to request deletion of a specific link for power saving, etc. Advantageously, based on this, links are set up based on the requests and link quality of the non-AP MLD.

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

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

[0084] When a link is deleted, the state of the link transitions 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 corresponding two MLDs are considered connected. When all links are torn down, the MLDs are no longer connected, and if the state is maintained at the MLD level, the state of the MLD changes to state 1.

[0085] According to the third embodiment, the AP MLD can limit frame exchange for multi-link setup to one of the links (i.e., the link in the highest frequency band (e.g., 6 GHz)) in order to ensure that the non-AP MLD is within range in all links. For example, it can be signaled at the discovery stage (e.g., in beacon / probe response frames transmitted on the link or in (shortened) neighbor report elements transmitted on other links) whether frame exchange for multi-link setup is permitted or not on a certain link. Alternatively, the AP MLD can also attempt to make the BSSs of all its associated APs have approximately the same coverage range by controlling the transmission power of each associated AP. However, in this case, the transmission power of the AP associated with the BSS in the lower frequency band (e.g., 2.4 GHz band) may be significantly lower than that of the AP associated with the BSS in the higher frequency band (e.g., 5 / 6 GHz). Therefore, although these measures can mitigate the problem of range difference, they may not be able to mitigate other link quality problems.

[0086] Figure 24 shows an illustration 2400 of multi-link setup and link maintenance between AP MLD and non-AP MLD. According to one example, at step 2402, both MLDs are operable on links 1, 2, 3. The non-AP MLD STA can measure the link quality by listening for beacons (passive scanning) on all three links or performing active scanning (exchanging probe request / response frames) before starting the multi-link setup. The non-AP MLD is authenticated by the AP MLD by exchanging an authentication frame or a 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 starts a multi-link setup request and requests to set up links 2 and 3 by sending a multi-link setup request frame on link 3. Link 1 is excluded from the request due to poor channel quality. The non-AP MLD can also include the link quality information of links 2 and 3.

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

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

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

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

[0091] The AP MLD considers setting up all three links and decides to set up all three links. Therefore, the AP MLD sends a multi-link setup response frame indicating that links 1, 2, and 3 have been set up. At this stage, the multi-link set consists of links 1, 2, and 3. However, the multi-link setup response frame includes a TID-link mapping element that maps all TIDs to only link 2 and link 3, and no TID is mapped to link 1. In this case, at step 2404, all three associated STAs are considered to be associated (i.e., in state 3), but only link 2 and link 3 are in the Enabled state, and link 1 is in the Setup state. The parameters of all links (1 to 3) are recorded by the AP MLD, and all conventional procedures related to association (such as AID assignment) are executed for all links. However, the generation / distribution of the secret key is only executed for the Enabled links. Alternatively, it is also possible to consider that only the associated STAs corresponding to the Enabled links are associated (i.e., in state 3), and the associated STAs corresponding to the other links are not considered to be associated (i.e., in state 1 or state 2). The parameters of all links (1 to 3) are recorded by the AP MLD, but all conventional procedures related to association (such as AID assignment) and the generation / distribution of the secret key are only executed for the Enabled links.

[0092] After a while, the AP MLD recognizes that the link quality of link 2 has fallen below the threshold of the required quality of the AP for this link. The AP continues to monitor the link, and since the link quality continues to be below the required threshold for a period longer than a specific TIMEOUT period, the AP decides to disable this link by performing a TID-link mapping that does not map TIDs to link 2. As a result, at step 2406, link 2 becomes the Disabled state, and all traffic is redirected to link 3.

[0093] In addition to step 2408 described in the previous example, when the AP MLD receives a request to enable a link for the first time, if step 2404 has not been performed, it can also perform procedures related to association (such as AID assignment) and distribute the private key. Subsequent activation / deactivation does not require this procedure and can be performed via the TID-link mapping.

[0094] FIG. 25 shows a schematic diagram of an MLD 2500 according to various embodiments. The MLD 2500 includes a MAC-SAP 2502 for accessing a distribution service (DS) via a control port and a non-control port, 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 state module 2508. The MLD 2500 also includes three associated STAs or stations, namely STA1 2510a, STA2 2510b, and STA3 2510c. Each STA includes a MAC layer and a physical layer, and transmissions are performed from the physical layer via link 1 (for STA1 2510a), link 2 (for STA2 2510b), and link 3 (for STA3 2510c). The MLD 2500 may be an AP MLD (where STA1-3 are associated APs) or a non-AP MLD (where STA1-3 are associated non-AP STAs), and it will be understood that the number of links and associated STAs or stations may be further expanded.

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

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

[0097] Various functions and operations of the STA 2700 are arranged in a plurality of layers according to a hierarchical model. In this model, according to the IEEE specification, the lower layer reports to the upper layer and receives instructions from the upper layer. For the sake of brevity, the details of the hierarchical model are not described in this disclosure.

[0098] As shown in FIG. 27, the STA 2700 can include a circuit 2714, at least one wireless transmitter 2702, at least one wireless receiver 2704, and a plurality of antennas 2712 (only one antenna is depicted in FIG. 27 for illustrative purposes for simplicity). The circuit can include at least one controller 2706, and the controller 2706 is used when executing tasks designed to include controlling communication with one or more other multi-link devices in a MIMO wireless network, under the support of software and hardware. The at least one controller 2706 can control at least one transmission signal generator 2708 for generating a multi-link action frame transmitted to one or more other STAs or MLDs via at least one wireless transmitter 2702, and at least one reception signal processor 2710 for processing a multi-link action frame received from one or more other STAs or MLDs via at least one wireless receiver 2704. The at least one transmission signal generator 2708 and the at least one reception signal processor 2710 can be stand-alone modules of the STA 2700 that communicate with at least one controller 2706 for the above-described functions. Alternatively, the at least one transmission signal generator 2708 and the at least one reception signal processor 2710 may be included in the at least one controller 2706. Those skilled in the art will understand that the arrangement of these functional modules is flexible and can vary according to actual needs and / or requirements. The data processing device, storage device, and other related control devices can be provided on a suitable circuit board and / or chipset.

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

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

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

[0102] The request information can identify one or more STAs among the first plurality of STAs. The request frame can further include information regarding the quality of the wireless channel of each of the one or more links. The first plurality of STAs may be configured to collect information regarding the quality of the wireless channel of each of the one or more links before transmitting the request frame, and the quality of the wireless channel includes one or more of link margin, path loss, received signal strength indicator (RSSI), and received channel power indicator (RCPI). The request information can further include information regarding the quality of the wireless channels of the plurality of links that can be set up between the first plurality of STAs and the second plurality of STAs, and the quality of the wireless channel is set to implicitly indicate one or more of the 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 the second plurality of STAs belonging to the second multi-link device (MLD). The wireless receiver 2704 can receive a request frame from the first STA during operation, the first STA is included in the first plurality of STAs belonging to the first MLD, the request frame includes request information, and based on the request information, it requests a multi-link setup to establish one or more links between one or more STAs among the first plurality of STAs and the corresponding one or more STAs among the second plurality of STAs. The wireless transmitter 2702 can transmit a response frame to the first STA to notify the result of the multi-link setup, and the response frame conveys information about the one or more links established between one or more STAs among the first plurality of STAs and the corresponding one or more STAs among the second plurality of STAs.

[0104] The request information can identify one or more STAs among the first plurality of STAs. The information of one or more links can include the operation parameters of one or more links and the capability information of one or more STAs among the second plurality of STAs corresponding to the one or more links. The response frame can 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 one or more TIDs mapped to the link on each link. The request information can include information regarding the quality of the wireless channel of one or more links, and the second MLD is configured to determine whether to establish one or more links based on that information. The response frame can further include information related to the block ACK parameters of the established links. The second MLD can be an AP MLD, the first MLD can be a non-AP MLD, and the STAs included in the second plurality of STAs can transmit a frame including information on a common MAC address identifying the AP MLD to advertise the AP MLD, and the frame is one of a beacon frame or a probe response frame. The STAs included in the second plurality of STAs can transmit a frame indicating the AP among the second plurality of STAs that is the destination of the request frame to advertise the AP MLD, and that frame is one of a beacon frame or a probe response frame.

[0105] The present disclosure can be implemented by software, hardware, or software that cooperates with hardware. Each functional block used in the description of each of the above-described embodiments 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 a combination of LSIs. The LSI may be formed as individual chips, or one chip may be formed to include part or all of the functional blocks. The LSI can include a data input / output section coupled to itself. Here, the LSI may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. However, the technology for implementing the integrated circuit is not limited to the LSI, and may be realized using an application-specific circuit, a general-purpose processor, or a special-purpose processor. Further, a programmable FPGA (Field Programmable Gate Array) after manufacturing the LSI, or a reconfigurable processor capable of changing the connection and setting of circuit cells arranged inside the LSI may be used. The present disclosure can be realized as digital processing or analog processing. With the progress of semiconductor technology and other derivative technologies, when future integrated circuit technology replaces the LSI, it is also possible to integrate functional blocks using the future integrated circuit technology. Biotechnology can also be applied.

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

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

[0108] Some non-limiting examples of such communication devices include telephones (e.g., cellular (mobile) 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), gaming consoles, e-book readers, telemedicine / telehealth (remote medical / pharmaceutical) devices, vehicles that provide communication capabilities (e.g., automobiles, airplanes, ships), and various combinations thereof.

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

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

[0111] The communication device can 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 can include a controller or sensor that generates a control signal or data signal used by a communication device that performs the communication functions of the communication device.

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

[0113] Non-limiting examples of stations can include stations included in a first plurality of stations belonging to a multilink station logical entity (i.e., such as an MLD), and as part of the first plurality of stations belonging to the multilink station logical entity, the stations of the first plurality of stations share a common media access control (MAC) data service interface to an upper layer, and the common MAC data service interface is associated with a common MAC address or traffic identifier (TID).

[0114] Therefore, it can be understood that embodiments of the present disclosure provide a communication device and a communication method operating on a plurality of links to fully realize the throughput gain of multilink communication, especially in secure retransmission of multilinks.

[0115] In the detailed description so far of this embodiment, exemplary embodiments have been presented, but it should be understood that there are a vast number of variations. Furthermore, it should be understood that the exemplary embodiments are examples and are not intended to limit the scope, applicability, operation, or configuration of the present disclosure in any way. Rather, the detailed description so far provides a convenient guide for those skilled in the art to implement the exemplary embodiments. It should be understood that various changes can be made to the steps of the operations, the functions and arrangements of the methods, and the modules and structures of the devices described in the exemplary embodiments without departing from the scope of the subject matter described in the appended claims.

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

[0117] According to one example, the second STA where the request information identifies one or more STAs among the first plurality of STAs.

[0118] According to one example, the information about one or more links includes the operation parameters of the one or more links and the capability information of one or more STAs among the second plurality of STAs corresponding to the one or more links.

[0119] According to one example, the response frame further includes information about 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 one or more TIDs mapped to the link on each link.

[0120] According to one example, the request information includes information about the quality of the wireless channel of one or more links, and the second MLD is configured to determine whether to establish one or more links based on the information.

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

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

[0123] A frame indicating an AP among a second plurality of STAs that is the destination of a request frame is transmitted by an STA included in the second plurality of STAs for advertising the AP MLD, and the frame is one of a beacon frame or a probe response frame. A second STA according to an example.

Claims

1. A receiver for receiving an association request frame from a non-access point multi-link device (non-AP MLD), the association request frame including information for identifying one or more links requested for multi-link setup and link-specific information of 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 transmitter for transmitting an association response frame indicating a link accepted by the controller; Equipped with the association request frame includes a common information field for indicating a MAC address of the non-AP MLD; AP MLD.

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

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

4. Before the multi-link setup, the receiving unit receives an authentication frame including a MAC address of the non-AP MLD, and the transmitting unit transmits an authentication response frame. The AP MLD of 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 of claim 1.

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

7. the association response frame is transmitted on the link on which the association request frame was received. The AP MLD of claim 1.

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

9. A communication method for an Access Point Multi-Link Device (AP MLD), comprising: receiving an association request frame from a non-access point multi-link device (non-AP MLD) including information for identifying one or more links requested for multi-link setup and link-specific information of the one or more requested links; determining whether to accept each of the one or more requested links based on the link-specific information; sending an association response frame indicating the accepted link; the association request frame includes a common information field for indicating a MAC address of the non-AP MLD; Communication methods.

10. the association request frame includes a multi-link element including one or more link information fields, each link information field including information for identifying one of the one or more requested links and its link specific information; The communication method according to claim 9.

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

12. Before the multi-link setup, receiving an authentication frame including a MAC address of the non-AP MLD and sending an authentication response frame; The communication method according to claim 9.

13. receiving a re-setup request frame for establishing a new link different from one or more links established between the non-AP MLD and the AP MLD; The communication method according to claim 9.

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

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

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

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