Communication apparatus and communication method for multi-link establishment and link maintenance

Abstract

Communication devices and methods for multi-link establishment and link maintenance are provided. One example embodiment provides a first station (STA) included in a first plurality of STAs affiliated with a first multi-link device (MLD), the first STA comprising: circuitry that generates a request frame, the request frame including request information; and a transmitter that transmits the request frame to a second STA to request multi-link establishment, wherein the second STA is included in a second plurality of STAs affiliated with a second MLD, and wherein the multi-link establishment sets up one or more links between one or more STAs of the first plurality of STAs and a corresponding one or more STAs of the second plurality of STAs based on the request information.

Description

TECHNICAL FIELD

[0001] The present embodiments relate generally to communication devices, and more specifically, to methods and apparatus for multi-link setup and link maintenance. BACKGROUND

[0002] In today's world, communication devices are expected to operate wirelessly with the same capabilities as wired computing devices. For example, users expect to be able to seamlessly watch a high-definition movie streamed to the user's wireless communication device. This presents challenges for the communication devices as well as the access points to which the communication devices wirelessly connect.

[0003] The Institute of Electrical and Electronics Engineers (IEEE) 802.11 group recently established an 802.11 Task Group (TG) to address these challenges. Multi-link operation in the 2.4 GHz, 5 GHz, and 6 GHz bands has been identified as a key candidate technology for such communications. Multi-channel aggregation over multiple links is a natural way to create orders of magnitude growth in communication data throughput.

[0004] To enable such multi-link operation between an access point (AP) multi-link device (MLD) and a non-AP MLD, a multi-link setup can be performed on one of the supported links to set up associations of stations (STAs) in one or more links. SUMMARY

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

[0006] Another non-limiting and exemplary embodiment facilitates providing a second STA included in a second plurality of STAs affiliated with a second multi-link device (MLD), the second STA comprising: a receiver that receives a request frame from a first STA, wherein the first STA is included in a first plurality of STAs affiliated with a first MLD, and wherein the request frame includes request information and is requesting a multi-link setup that sets up 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 inform a result of the multi-link setup, wherein the response frame carries information of the one or more links that have been set up between the one or more STAs of the first plurality of STAs and the corresponding one or more STAs of the second plurality of STAs.

[0007] Another non-limiting and exemplary embodiment facilitates providing a communication method comprising: generating, at a first STA included in a first plurality of STAs affiliated with a first MLD, a request frame, the request frame including 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 affiliated with a second MLD, and wherein the multi-link setup sets up one or more links between one or more STAs of the first plurality of STAs and corresponding one or more STAs of the second plurality of STAs based on the request information.

[0008] It should be noted that general or specific embodiments can be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof. Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. Benefits and / or advantages can be had from one or more of the embodiments and / or variations thereof without necessarily employing all of the embodiments and / or variations. BRIEF DESCRIPTION OF DRAWINGS

[0009] The accompanying drawings are used to illustrate various embodiments and to explain the principles and advantages according to various embodiments, in which the same reference numbers in the separate views refer to the same or functionally similar elements, and which are incorporated in and form part of the specification.

[0010] Figure 1 The relationship between coverage frequency and range of a wireless node is illustrated.

[0011] Figure 2 A communication flow between an AP MLD and a non-AP MLD for multi-link setup, link quality assessment, traffic identifier (TID) to link mapping, and communication thereafter is depicted according to one example.

[0012] Figure 3 A diagram depicting an AP MLD with multiple basic service sets (BSSs) and multiple non-AP MLDs within the range of the BSSs is depicted in accordance with various embodiments.

[0013] Figure 4 A diagram depicting an extended service set (ESS) with MLDs is depicted in accordance with various embodiments.

[0014] Figure 5 A communication flow between an AP MLD and a non-AP MLD for multi-link discovery, authentication, setup, TID-to-link mapping, and communication thereafter is depicted in accordance with a first embodiment.

[0015] Figure 6 A diagram of a multi-link action frame in accordance with a first embodiment is depicted.

[0016] Figure 7 A diagram of a multi-link setup frame in accordance with a first embodiment is depicted.

[0017] Figure 8 A diagram of a multi-link element in accordance with a first embodiment is depicted.

[0018] Figure 9 A diagram of a multi-link teardown frame in accordance with a first embodiment is depicted.

[0019] Figure 10 A diagram of a transmit power control (TPC) request element in accordance with a first embodiment is depicted.

[0020] Figure 11 A diagram of a TPC report element in accordance with a first embodiment is depicted.

[0021] Figure 12 A diagram of a multi-link element for multi-link authentication in accordance with a first embodiment is depicted.

[0022] Figure 13 A diagram of a multi-link element for a multi-link setup request in accordance with a first embodiment is depicted.

[0023] Figure 14A A variation of a minimum link quality requirement table maintained by an AP MLD in accordance with a first embodiment is depicted.

[0024] Figure 14B A user priority (UP) to TID mapping table as specified in the 802.11 specification is depicted.

[0025] Figure 14C A diagram of a multi-link element for a multi-link setup response and TID-to-link mapping in accordance with a first embodiment is depicted.

[0026] Figure 14D A TID mapping encoding table according to the first embodiment is depicted.

[0027] Figure 15 A communication flow between an AP MLD and a non-AP MLD including a multi-link setup request according to the first embodiment is depicted.

[0028] Figure 16 A diagram of a multi-link action frame of a multi-link setup response according to the first embodiment is depicted.

[0029] Figure 17 A state transition diagram according to the first embodiment is depicted.

[0030] Figure 18 An alternative state transition diagram according to the first embodiment is depicted.

[0031] Figure 19 A diagram of how link maintenance is conducted according to the first embodiment is depicted.

[0032] Figure 20 A communication flow between an AP MLD and a non-AP MLD including a link quality assessment step according to the second embodiment is depicted.

[0033] Figure 21 An alternative state transition diagram according to the second embodiment is depicted.

[0034] Figure 22 A diagram of a multi-link setup request and link deletion multi-link element according to the second embodiment is depicted.

[0035] Figure 23 A diagram of a multi-link teardown frame according to the second embodiment is depicted.

[0036] Figure 24 A diagram of multi-link setup and link maintenance between an AP MLD and a non-AP MLD according to various embodiments is depicted.

[0037] Figure 25 A schematic diagram of an MLD 2500 according to various embodiments is depicted.

[0038] Figure 26 A flowchart 2600 illustrating a method of retransmission of multi-link guarantees according to various embodiments is shown; and

[0039] Figure 27 A schematic partial cutaway view of one of the affiliated STAs of a multi-link device 2700 that can be implemented for multi-link communications according to various embodiments is shown.

[0040] Those skilled in the art will understand that the elements in the figures are illustrated for simplicity and clarity and that the actual implementation can be of a different form. DETAILED DESCRIPTION

[0041] 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. Furthermore, there is no intention to be bound by any theory of operation presented in the preceding background or the following detailed description. Also, throughout the specification, any and all references to a numerical value should be read as "about" that value, unless the context clearly indicates otherwise.

[0042] Generally, upon the completion of the multi-link setup between the AP MLD and the non-AP MLD, the concerned link can be in one of the following states:

[0043] - Established (or setup): the AP MLD and the non-AP MLD have all the information to enable each other for data operations. This state can be equivalent to state 3 of the state transition diagram for non-mesh STAs, where the IEEE 802. IX controlled port is blocked (i.e., only Extensible Authentication Protocol over LAN (EAPOL) data frames are allowed, no other data frames are allowed).

[0044] - Enabled (activated): both MLDS agree to start data operations on the link. For example, at least one traffic identifier (TID) is mapped to the link, and the robust security network association (RSNA) for the link has been completed. This can be equivalent to state 4 of the state transition diagram for non-mesh STAs, where the IEEE 802. IX controlled port is not blocked (i.e., all data frames are allowed).

[0045] - Disabled: in this state, the link can be established but data operations are disabled, or the establishment and RSNA are completed but no TID is mapped to the link, or the MLD can ignore the frames received on the link.

[0046] It is important to explicitly define how the MLD maintains the link state and the rules for allowing / disallowing frames and the related actions of the MLD for each link state.

[0047] In addition, different links of an MLD can have different range / channel conditions. Referring to Figure 1 , Figure 1The relationship between coverage frequency and range of wireless nodes is depicted, with 11af coverage (54-698 MHz) having a 3 km and greater coverage range, cellular coverage (600-900 MHz) having a 1-3 km range, 11ah coverage (900 MHz) having a 1 km range, 11 / b / g / n coverage (2.4 GHz) having a 100 m range, 11a / ac coverage (5 GHz) having a 50 m range, and 11ad coverage (600 MHz) having a 10 m range. If the establishment frames of the multi-link establishment are exchanged in a link in a lower frequency band (e.g., 2.4 GHz band), the MLD can not be within range of the other links in a higher frequency band (e.g., 5 GHz or 6 GHz). Moreover, even if the MLD is within range in the other supported links, some links can not be of good quality, e.g., due to excessive Overlapping Basic Service Set (OBSS) interference, frequency-dependent fading, etc., or due to coexistence interference (e.g., due to Bluetooth, etc., in the 2.4 GHz band) and thus can not be suitable for link enablement.

[0048] In fact, the link capabilities of the non-AP MLD itself can not provide enough information to establish links. After the completion of the multi-link establishment procedure, some (potential) links / STAs of the MLD can be in the fourth state (i.e., not established (not setup / available)). Therefore, frame exchange is not possible on the links. However, such links can become available for establishment if the conditions change (e.g., the non-MLD moves closer to the AP MLD).

[0049] Therefore, links should not be established or setup based on capability information only. The non-AP MLD should be able to select which links to establish. Moreover, the channel quality of the links (especially the second and subsequent links) needs to be checked before the links are setup / enabled (either during the multi-link establishment itself or during a subsequent enablement operation). The channel quality of the enabled links also needs to be checked periodically to ensure that the link is active and suitable for the TID(s) mapped to it.

[0050] Accordingly, the present invention seeks to address the above problems.

[0051] Figure 2A communication flow between the AP MLD 202 and the non-AP MLD 204 according to a typical solution for addressing the above issues is depicted, which is for multi-link setup, link quality assessment, traffic identifier (TID) to link mapping, and communication thereafter. 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 on link capabilities for links 1, 2, and 3. In response to the request, the AP MLD 202 sets up the requested links 1, 2, and 3, and then sends a multi-link setup response 208 to the non-AP MLD 204 to notify of the setup of the links. At 210, the non-AP MLD 204 is now authenticated / associated, and the 3 links are now set up. A multi-link RSNA (4-way handshake / group key handshake) between the AP MLD 202 and the non-AP MLD 204 is then performed on link 2. It should be understood that each of links 1, 2, and 3 connects a dependent STA of the AP MLD 202 and a dependent STA of the non-AP MLD 204, such that these STAs transmit or receive any data or frames on the relevant link.

[0052] After the multi-link setup is complete, the AP MLD 202 can initiate a link quality assessment procedure to check the quality of the set up links, which can be used to decide the TID to link mapping. The AP MLD 202 can send a link measurement request 214 on link 1 and a link measurement request 218 on link 3 in order to assess the link quality of the other links except link 2. In response, the non-AP MLD 204 sends a link measurement report 216 and a link measurement report 220 to the AP MLD 202 over link 1 and link 3, respectively. The link measurement report 216 includes the link quality information of link 1, and the link measurement report 220 includes the link quality information of link 3. The link quality assessment can also be performed before the multi-link setup.

[0053] Thereafter, the AP MLD 202 can decide the TIDs to be mapped to each link based on the link quality assessment, and initiate the TID to link mapping by sending a TID to link mapping request 222 to the non-AP MLD 204 on link 2. The TID to link mapping request includes a TID mapping indicating how each TID is mapped to each link. In response, the non-AP MLD 224 sends a TID to link mapping response 224 to the AP MLD 202 on link 2 to indicate the status of the TID mapping. After all 3 links are enabled and the TIDs are mapped to the links (at 226), frame exchange can then proceed on any / all of the 3 links (at 228).

[0054] The above solution has some drawbacks. For example, the link is established based only on capability information (i.e., the capability information included in the multi-link setup request 206). Furthermore, this is an AP-centric solution; that is, the STA has no say in which link is established or enabled.

[0055] During multi-link setup, additional links (i.e., links other than the one used to exchange the multi-link setup frames) should not be established based only on capability information. The first MLD can request the second MLD, whose links are to be established as part of the multi-link setup, independent of link capabilities, e.g., using the setup request field in the multi-link setup request frame. The MLD can also include information about the link quality (e.g., uplink / downlink (UL / DL) link margin, UL / DL path loss, etc.) of the requested link. Furthermore, the second MLD will only establish the links requested by the first MLD during the multi-link setup (e.g., allocation of association identifiers (AIDs), contents in the association record, etc.). The established links can be referred to as a multi-link set. The second MLD can also take into account the information about the link quality to decide whether to establish / enable a link, especially in the case of TID restrictions on some links. This information can also be used for subsequent TID-to-link mapping (i.e., link enable / disable).

[0056] Figure 3 A diagram 300 is depicted of an AP MLD 302 with multiple BSSs and non-AP MLDs 304, 306, and 308 within the BSS range, in accordance with various embodiments. The AP MLD 302 can be illustrated as a schematic 314 including a MAC-service access point (MAC-SAP) for accessing a distribution service (DS), an MLD MAC address identifying the AP MLD, and three affiliated APs (i.e., AP1, AP2, and AP3). Each AP has its own STA MAC address at the MAC layer and is connected via a link at the PHY 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).

[0057] Furthermore, the non-AP MLDs 304, 306, and 308 can be illustrated as a schematic 316 including a MAC-SAP for accessing a DS, an MLD MAC address identifying the non-AP MLD, and three affiliated STAs (i.e., STA1, STA2, and STA3). Each STA has its own STA MAC address at the MAC layer and is connected via a link at the PHY 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).

[0058] The AP MLD 302 establishes multiple (multi-link) BSSs, one per affiliated AP. Each BSS has its own BSSID, beacon, and can have different coverage. For example, API runs a BSS on 6 GHz, AP2 runs a BSS on 5 GHz, and AP3 runs a BSS on 2.4 GHz. The coverage of the different APs can differ (due to frequency band, transmit (Tx) power, etc.). The coverage can also depend on the modulation and coding scheme (MCS), i.e., MCS 0 can have a much larger coverage than MCS 9. In addition, non-AP MLDS can be within range of one or more such BSSs. For example, only STA1 of non-AP MLD 304 is within coverage of API of AP MLD 302 via API; only STA1 and STA2 of non-AP MLD 306 are within coverage of API and AP2 of AP MLD 302 via API and AP2, while all 3 STAs of non-AP MLD 308 are within coverage of AP MLD 302 (i.e., all three APs).

[0059] The AP MLD is an entity with distributed system access function (DSAF) that enables associated non-AP MLDS (with one or more affiliated STAs) as well as legacy STAs to access a DS via a wireless medium (WM). Different affiliated STAs of a non-AP MLD can connect to different APs of the AP MLD to gain access to the DS. However, all APs of the AP MLD can connect to the DS through the same single MAC-SAP and DSAF.

[0060] The network forms Figure 4The extended service set (ESS) 400 illustrated in the middle. STAs 1, 2, and 3 affiliated with the non-AP MLD 1 can connect to, for example, APs 1, 2, and 3 of the AP MLD 1, respectively, to gain access to the DS. The APs 1, 2, and 3 can connect to the DS through the MAC-SAP and DSAF of the AP MLD 1. In addition, STAs 4, 5, and 6 affiliated with the non-AP MLD 2 can connect to, for example, APs 4, 5, and 6 of the AP MLD 2, respectively, to gain access to the DS. The APs 4, 5, and 6 can connect to the DS through the MAC-SAP and DSAF of the AP MLD 2. Traditionally, a legacy STA such as STA 7 gains access to the DS by associating with an AP, and it can even continue to do so with an AP MLD by associating with any one of its affiliated APs (e.g., AP 4 of the AP MLD 2). However, for a non-AP MLD, the association procedure can be replaced by a multi-link setup procedure, as will be further described below. The multi-link setup performed between any pair of affiliated STA and affiliated AP can provide access to the DS for one or more affiliated STAs of the non-AP MLD.

[0061] Figure 5 A communication flow between an AP MLD and a non-AP MLD according to the first embodiment is depicted, for multi-link discovery, authentication, setup, TID-to-link mapping, and communication thereafter. First, in the multi-link discovery phase, the non-AP MLD 504 checks the quality of links 1, 2, and 3 by sending a probe request frame 506 on each link to the AP MLD 502. The probe request frame 506 can include a transmit power control (TPC) request element. The AP MLD 502 can respond to the receipt of the probe request frame 506 by sending a beacon or probe response frame 508 on each link to the non-AP MLD 504. The beacon or probe response frame 508 can include the MLD MAC address of the AP MLD 502 as well as a TPC report element. After the completion of the multi-link discovery phase, the non-AP MLD can be considered to be in state 1.

[0062] After the discovery phase, the non-AP MLD 504 can initiate multi-link authentication by sending an authentication request 510 to the AP MLD 502 on, for example, link 2. The authentication request can include information of the MLD MAC address of the non-AP MLD 504. In response to receiving the authentication request 510, the AP MLD 502 can send an authentication response 512 to the non-AP MLD 504 on the same link 2. The authentication response can include information about the MLD MAC address of the AP MLD 502. Multi-link authentication can be optional for Open Systems with Extensible Authentication Protocol (EAP), but mandatory for SAE and Fast Initial Link Setup (FILS). The MLD MAC address can be used during authentication for SAE and FILS. After the authentication is successfully completed, the multi-link state of the non-AP MLD can be changed to state 2.

[0063] After the authentication is successfully completed, the non-AP MLD 504 can initiate multi-link setup / association by sending a multi-link setup request 514 to the AP MLD 502 on, for example, link 2. The multi-link setup request 514 can include link capabilities of links 1, 2, and 3 and request information that identifies the non-AP MLD 504’s affiliated STAs for which links are to be setup, i.e., in this case, links 1, 2, and 3. The request information can also include information about the wireless channel quality in each of links 1, 2, and 3. The request information can also include information about the traffic characteristics expected for each of links 1, 2, and 3, which is one of a traffic identifier (TID), a payload size, a delay bound, a data rate, a minimum PHY rate, etc.

[0064] In response to the request and based on the request information, the AP MLD 502 sets up the requested links 1, 2, and 3, and then sends a multi-link setup response 516 to the non-AP MLD 504 to inform of the setup of the links. At 518, the non-AP MLD 504 is now authenticated / associated and the 3 requested links are now setup. After the setup is successfully completed, the multi-link state of the non-AP MLD can be changed to state 3. Multi-link RSNA (4-way handshake / group key handshake) between the AP MLD 502 and the non-AP MLD 504 can then be performed on, for example, link 2.

[0065] After the multi-link setup is complete, the AP MLD 502 can initiate TID-to-link mapping by sending a TID-to-link mapping request 522 to the non-AP MLD 504 on, for example, link 2. The TID-to-link mapping request 522 can include the requested TID mapping for links 1, 2, and 3, indicating how each TID is mapped to each link. In response, the non-AP MLD 524 can send a TID-to-link mapping response 524 to the AP MLD 502 on link 2 to indicate the status of the TID mapping. After all 3 links are enabled and the TIDs are mapped to the links (at 526), frame exchange can then proceed (at 528) on any / all of the 3 links. After the TID-to-link mapping is complete at 526, the multi-link state of the non-AP MLD can be changed to state 4. The TID-to-link mapping can be optional, and the initial mapping can also be performed as part of the multi-link setup steps. By default, all TIDs are mapped to all established links.

[0066] It should also be understood that each of links 1, 2, and 3 connects the affiliated AP of the AP MLD 502 and the affiliated STA of the non-AP MLD 504, such that the STAs transmit or receive any data or frames on the relevant link. Prior to sending the setup request 514, the affiliated STAs of the non-AP MLD 504 can collect information about the wireless channel quality for each of one or more links, where the wireless channel quality includes one or more of a link margin, a path loss, a received signal strength indication (RSSI), and a received channel power indication (RCPI).

[0067] The multi-link operation shown can define a new (class 1) action frame. Figure 5 The multi-link operation shown can define a new (class 1) action frame. Figure 6 A diagram depicting a new multi-link action frame 600 according to a first embodiment is shown. The multi-link action frame 600 can include a frame control field, a duration field, three address fields, a sequence control field, an HT control field, a category field, a multi-link action field, a variable field, and a frame check sequence (FCS) field. The multi-link action field can have a value of 0, indicating that the action frame is for multi-link setup, or a value of 1, indicating that the action frame is for multi-link teardown. Values 2-255 can be reserved.

[0068] Figure 7A diagram depicting a multi-link setup frame 700 according to the first embodiment is depicted. 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 a FCS field.

[0069] Figure 8 A diagram depicting a multi-link element 800 according to the first embodiment is depicted. 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 parameter control field, and a multi-link parameter field. The multi-link element 800 can be carried in the multi-link action frame 600 or other frames such as association request / response frames and other management frames. Multiple multi-link elements can also be carried in the same frame if multiple multi-link operations are signaled in the same frame exchange (e.g., TID mapping and BA setup, or multi-link setup and TID mapping). The operation is signaled by the value indicated in the action type field of the multi-link element 800. A value of 0 can indicate multi-link authentication, a value of 1 can indicate multi-link setup request, a value of 2 can indicate multi-link setup response, a value of 3 can indicate TID to link mapping request, a value of 4 can indicate TID to link mapping response, a value of 5 can indicate block acknowledgement setup request, and a value of 6 can indicate block acknowledgement setup response. Other values of 7-255 can be reserved.

[0070] Figure 9 A diagram depicting a multi-link teardown frame 900 according to the first embodiment is depicted. 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 a value of 1 (i.e., set to multi-link teardown), and a FCS field.

[0071] Alternatively, different multi-link action frames and different multi-link elements can be defined for each category. Alternatively, different signaling can be defined for the purpose of adding / removing links (i.e., multi-link link Add Remove request / response).

[0072] Referring back to Figure 5 After discovering the multi-link BSS (i.e., through the multi-link capability element in the beacon frame), in order for the AP to be able to compute the UL pathloss, the non-AP MLD 504 can include its transmit power (i.e., in a modified transmit power control (TPC) request element) in the probe request frame 506 transmitted in each multi-link BSS (link). Figure 10A diagram depicting a TPC request element 1000 according to the first embodiment is depicted. 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 primary frame (i.e., the probe request frame 506).

[0073] Based on the transmit power indicated in the TPC request element of the received probe request frame, the AP MLD 502 can estimate the UL path loss and the UL link margin and include this information in the probe response frame 508 (i.e., in the modified TPC report element) for transmission back to the non-AP MLD 504 in each multi-link BSS. Figure 11 A diagram depicting a TPC report element 1100 according to the first embodiment is depicted. The TPC report element 1000 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 primary frame (i.e., the probe response frame 508). The link margin is the difference between the received power (dBm) and the receiver sensitivity (dBm). The link margin field is encoded as a 2s-complement signed integer in decibels and can be set to -128 to indicate that no link margin is provided. The path loss is the difference between the transmit power and the received power of the frame carrying the TPC request element (e.g., the probe request frame received from the non-AP MLD). The path loss field is encoded as a 2s-complement signed integer in decibels and can be set to 128 to indicate that no path loss is provided. 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.

[0074] On receiving the probe response frame 508, the non-AP MLD 504 can use the transmit power information in the TPC report element to compute the DL path loss, while the DL link margin can be computed based on the received power. The non-AP MLD 504 can use the information of the link margin and path loss to estimate the UL / DL link quality of each BSS (link). Alternatively, if the link measurement request / report frames are reclassified as class 1 frames for Directional Multi-Gigabit (DMG) / 11be STAs, they can be used to achieve similar information. In addition, the AP MLD 502 can also advertise its MLD MAC address in the beacon / probe response frames (e.g., within the multi-link capability element) to be used during multi-link authentication (SAE, FILS), multi-link setup. If not, the probe request frame needs to carry an indication of the request for the MAC address of the AP MLD. It will be understood that the link measurement request / response frames mentioned here are alternatives, but any other suitable management frames can also be used for this purpose. In addition, the results of the probe procedure (e.g., Channel Quality Index (CQI)) can also be used if available.

[0075] If the authentication is successful, the legacy STA state is changed to state 2. For MLDs, the state can be maintained at the MLD level (rather than the STA level). For open system authentication (e.g., EAP), two authentication frames are exchanged between the two MLDs. The existing authentication steps can be reused or completely omitted. For SAE (i.e., authentication using a password), four authentication frames are exchanged between the two MLDs using a shared key (e.g., password) to authenticate each other and generate a Pairwise Master Key (PMK). The MLD MAC address can be used instead of the link MAC address to initialize the STA-A-MAC and STA-B-MAC values that are used to generate the secret Password Element (PWE). For FILS authentication, two authentication frames are exchanged between the two MLDs to authenticate each other and generate a PMK. The AP-BSSID / STA-MAC can be replaced with the corresponding MLD MAC address to generate the PMK.

[0076] Reference Figure 5 Assuming that the non-AP MLD 504 discovers the MLD MAC address of the AP-MLD during multi-link discovery, but the non-AP MLD 504 needs to include its MLD MAC address in the authentication / multi-link setup frame (e.g., in the multi-link element) in order to allow the AP MLD 502 to authenticate the non-AP MLD 504 and also signal the AP MLD 502 to use the MLD MAC address for SAE and FILS authentication. For this purpose, a multi-link element can be carried in the authentication frame (or multi-link setup frame). Figure 12A diagram of a multi-link element 1200 for multi-link authentication according to the first embodiment is depicted. The multi-link element 1200 includes the same fields as the multi-link element 800. However, the action type field is set to a value of 0 indicating multi-link authentication, and the multi-link parameter 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 can be used, or an authentication frame can be re-used. The multi-link authentication is used to establish the identity of one MLD as a member of a set of MLDs that are authorized to associate with another MLD.

[0077] Figure 13 A diagram of a multi-link element 1300 for a multi-link setup request according to the first embodiment is depicted. The action type field is set to a multi-link setup request (i.e., set to a value of 1). The multi-link parameter field can also include an MLD MAC address field, a multi-link capability field, a common information field carrying 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 link-specific information, such as a link MAC address subfield, a link capability subfield, a setup request subfield, a UL link margin subfield, a UL path loss subfield, a DL link margin subfield, and a DL path loss subfield.

[0078] Reference is made to Figure 5 With respect to multi-link setup in, the non-AP MLD 504 can explicitly request which links to be setup, i.e., by using the setup request subfield in the multi-link element 1300. For example, a value of 0 indicates that no setup is requested for the concerned link, while a value of 1 indicates that setup is requested. The non-AP MLD 504 can consider information of link quality to decide which links to request for multi-link setup. It can also consider other factors, e.g., the non-AP MLD 504 can have the capability for a 2.4 GHz link (i.e., link 1), but due to coexistence issues of its Bluetooth radio, it can choose not to request setup of this link, or it can choose not to request setup of certain links to save power, etc. The non-AP MLD 504 can also include information on link quality of the requested links (e.g., UL / DL link margin, UL / DL path loss, etc. obtained during discovery). If link quality information is not available, the received signal strength indicator (RSSI) / received channel power indicator (RCPI) of the beacon / probe response frame received on the link can be included as an estimate of link quality. Results of a sounding procedure (e.g., channel quality index (CQI)) can also be used as link quality information if available.

[0079] The non-AP MLD 504 can also include fields describing characteristics and QoS expectations of the traffic flow on the relevant link. Furthermore, the link quality information in the UL link margin subfield, UL path loss subfield, DL link margin subfield, and DL path loss subfield can be omitted if no setup is requested for the relevant link. Advantageously, this ensures that the link is setup based on the non-AP MLD’s request and link quality.

[0080] Upon receiving the multi-link setup request from the non-AP MLD 504, the AP MLD 502 will setup only the links requested by the non-AP MLD 504 (i.e., allocation of AIDs, content in the association record, etc.), as well as the subsequent procedures (i.e., TID-to-link mapping, security key generation / distribution, etc.). The AP MLD 502 can use the information on link quality to decide whether to setup / enable the requested links, especially in the case where there are TID restrictions on some links. This information can also be used for subsequent TID-to-link mapping (i.e., link enable / disable). The AP MLD 502 can maintain a minimum link quality table required for the non-AP MLD to use the links.

[0081] Figure 14A A variation of the minimum link quality requirement table maintained by the AP MLD according to the first embodiment is depicted. Figure 14A The link quality (in terms of link margin) required to map a TID to a specific link is specified. Different links can have different values. For example, referring to Figure 14A The links mapped with TIDs 6, 7 (AC_VO) can have higher link quality requirements to support higher MCS. The requirements can be different for uplink (UL) and downlink (DL). Figure 14B The mapping of user priority (UP) to TID as specified in the 802.11 specification is depicted.

[0082] The AP MLD can also use the information of the traffic flow (similar to the TSPEC element) if provided to decide whether to setup / enable specific requested links for the non-AP MLD. For example, for a non-AP MLD that has indicated heavy traffic flow for TIDs 6, 7, the AP MLD can refuse to enable the links mapped with TIDs 6, 7 in order to maintain the QoS requirements on the links. In some cases, the AP MLD can setup all the requested links and only consider the link quality to decide whether to enable the links (e.g., during the initial or subsequent TID-to-link mapping). In other cases, the AP MLD can even consider the link quality to setup the requested links.

[0083] The AP MLD can only include information of the links that have been setup in the multi-link setup response frame.Figure 14C A diagram of a multi-link action frame 1400 according to the first embodiment depicting a multi-link setup response and TID-to-link mapping is depicted. The multi-link action field of the multi-link action frame 1400 is set to multi-link setup (i.e., set to 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., the action type field is set to multi-link setup request with one or more link information subfields (one for each link that has been setup). The action type field of the multi-link element 1404 is set to TID-to-link mapping request (i.e., set to value 3) and can include (similar to the multi-link elements 1300 and 1402) one or more link information fields (one for each link that has been setup). However, each of the one or more link information fields can include a link ID subfield, an UL TID mapping, and a DL TID mapping. Each TID mapping can be a bitmap (i.e., 8 bits: 1 bit / TID) indicating the TIDs mapped to the link in that direction (UL or DL) or can use one or more 4-bit fields to indicate the TIDs. Figure 14D An example of a 4-bit field based TID mapping encoding is illustrated in the middle, whose value ranges from 0 to 15. Upon receiving a TID-to-link mapping request frame from the AP MLD, the non-AP MLD can send back a TID-to-link mapping response frame indicating acceptance of the TID mapping. If the TID mapping is rejected, the default TID mapping applies to the link or the AP MLD can disable the link of the non-AP MLD. It will be appreciated that two multi-link elements can be carried in a multi-link setup action frame (or association response frame) to signal multi-link setup and TID-to-link mapping, respectively, or they can also be combined in a single element.

[0084] Furthermore, not only the multi-link setup request / response frames can be used for multi-link setup, the association request / response frames (i.e., carrying multi-link elements) can also be used for multi-link setup. Upon successful completion of the multi-link setup, one or more non-AP STAs of the non-AP MLD are able / allowed to invoke distribution system services via one or more AP STAs of the AP MLD.

[0085] New MAC sublayer management entity (MLME) primitives can be defined for multi-link setup, e.g., used by the non-AP MLD or the AP MLD. MLME primitives are used to transfer information between the MLME and the station management entity (SME). The SME uses the services provided by the MLME through the MLME SAP. A primitive for a non-AP MLD to request multi-link setup can be as follows:

[0086]

[0087] This primitive causes a multi-link setup request frame to be sent to the peer MLD. PeerMLDAddress is set to the MLD MAC address of the peer MLD; PeerLinkAddress is set to the MAC address of the peer MLD's affiliated STA (of the link in which the multi-link setup request frame will be sent). One or more multi-link elements can be included to carry the information required by the multi-link setup request.

[0088] The primitive to acknowledge the multi-link setup for a non-AP MLD can be as follows:

[0089]

[0090] This primitive is generated upon receipt of a multi-link setup response frame. PeerMLDAddress is set to the MLD MAC address of the peer MLD; the one or more multi-link elements carried in the multi-link setup response frame are included. The dialog token is used to identify the multi-link setup request / response transaction.

[0091] A non-AP MLD indicates that one or more links are available by invoking the MLME- MULTI-LINK-SETUP.confirm primitive. This signals to the supplicant that the MLD MAC has transitioned to state 3. If the MLD negotiated the use of IEEE 802. IX authentication during the multi-link setup, the MLD's management entity can respond to the MLME-MULTI-LINK-SETUP.confirm (or indicate) primitive by requesting the supplicant (or authenticator) to initiate IEEE 802. IX authentication. Thus, in this case, the authentication is driven by the non-AP MLD's decision to initiate the multi-link setup and the AP MLD's decision to accept the multi-link setup.

[0092] The primitive to indicate that a request for multi-link setup for an AP MLD was received can be as follows:

[0093] This primitive can be generated upon receipt of a multi-link setup request frame. PeerMLDAddress is set to the MLD MAC address of the peer MLD. The one or more multi-link elements carried in the multi-link setup request frame are included.

[0094] The primitive to respond to a request for multi-link setup for an AP MLD is as follows:

[0095]

[0096] This primitive causes a multi-link setup response frame to be sent to the peer MLD. PeerMLDAddress is set to the MLD MAC address of the non-AP MLD; PeerLinkAddress is set to the MAC address of the peer MLD's affiliated STA (of the link in which the multi-link setup response frame will be sent). One or more multi-link elements can be included to carry the information needed by the multi-link setup response.

[0097] In addition, a primitive to request a multi-link teardown (for both non-AP MLDs or AP MLDs) can be as follows:

[0098]

[0099] This primitive causes a multi-link teardown frame to be sent. PeerMLDAddress is set to the MLD MAC address of the peer MLD. Optionally, one or more Link IDs can be included, each identifying a link to be torn down.

[0100] A non-AP MLD can request to add a new link by re-executing a multi-link setup. Link quality, traffic flow information can also be included. Figure 15 A diagram 1500 depicting a communication flow between an AP MLD 1502 and a non-AP MLD 1504 including a multi-link setup request according to a first embodiment is depicted. During a multi-link setup, the AP MLD 1502 rejects the setup of link 3 due to poor link quality. Thus, only links 1 and 2 are enabled. Subsequently, the non-AP MLD 1504 can request the setup of link 3 by sending a multi-link setup request 1506 including request information to the AP MLD 1502, e.g., due to an improvement in the link quality of link 3. The request information can include link capabilities, information identifying link 3, and link quality of link 3. The AP MLD 1502 sets up the requested link based on the request information and sends a multi-link setup response 1508 to the non-AP MLD 1504 including information of the setup link (i.e., link 3) and TID mapping of link 3. No authentication with an IEEE 802. IX server, PMKSA setup, etc. is performed. Advantageously, this enables the flexible addition of a new link with improved link quality.

[0101] Since the non-AP MLD 1504 has already been considered as authenticated / associated with the AP MLD 1502 during the initiation of the multi-link setup, the AP MLD 1504 only performs the procedures related to the addition of the new requested link (e.g., AID allocation for the new link, update of the link MAC addresses of the association record, TID-to-link mapping, etc.). If needed, security keys (i.e., pairwise transient key (PTK), group transient key / (integrity) group transient key (GTK / IGTK)) can also be generated / distributed for the new link. If the same PTK is used for all enabled links, the 4-way handshake is not necessarily needed for the new link. If different GTK / IGTK are used for the new link, they can be distributed using the group key handshake. Alternatively, different signaling can be defined for this purpose instead of reusing the multi-link setup (e.g., multi-link link addition request / response).

[0102] The addition of the new link can have to change some parameters of the existing block acknowledgement agreement that are mapped to the TIDs of the new link. For the existing block acknowledgement agreement with the AP MLD as the initiator (i.e., for DL streams), the AP MLD can also include the related block acknowledgement parameters in the same frame carrying the multi-link setup response. The non-AP MLD can also follow suit by initiating the update of the block acknowledgement parameters for the TIDs mapped to the new link of the UL stream (either in an add block acknowledgement (ADDBA) request frame or piggybacked in another frame, e.g., in a TID-to-link mapping response frame).

[0103] Figure 16 A diagram of a multi-link action frame 1600 of a multi-link setup response depicting the addition of a new link according to a first embodiment is depicted. While similar to the multi-link action frame 1400, the multi-link action frame 1600 also includes a multi-link element (block acknowledgement setup request) field 1602. The multi-link element 1602 can include one or more link information fields, each of the one or more link information fields including 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. Thus, the related block acknowledgement parameters for the new link can be included in the multi-link element 1602.

[0104] In response to the TID-to-link mapping request 1604, the non-AP MLD receiving the multi-link action frame 1600 can send a TID-to-link mapping response frame back to the sending AP MLD. The TID-to-link mapping response frame can be a multi-link action frame carrying a multi-link element with the action type set to TID-to-link mapping response.

[0105] Dynamic enabling / disabling of links (using TID-to-link mapping) can impact block acknowledgement parameters (e.g., receive reordering buffer size, unified BA scoreboard size, etc.) and can trigger ADDBA re-negotiation during each link enable / disable. For example, if a new link is added, the BA scoreboard size, starting sequence number, etc. need to be specified for the new link. The receiver MLD can also be required to increase the size of the receive (RX) reordering buffer to be able to receive additional frames from the added link.

[0106] Figure 17A state transition diagram 1700 according to the first embodiment is depicted. The MLDs can maintain an enumerated type state variable for each MLD that needs to communicate directly with it via WM over one or more links (rather than maintaining the state between two affiliated STAs). For example, based on the state transition diagram 1700, each MLD can be in one of four states: State 1 (unauthenticated, unassociated), State 2 (authenticated, unassociated), State 3 (authenticated, associated, pending RSNA authentication), and State 4 (authenticated, associated, RSNA established or not needed). Successful authentication changes the state of the MLD from State 1 to State 2. Successful multi-link setup (with at least one requested link) changes the state of the MLD from State 2 to State 3. Confirmation of security parameters occurs during multi-link setup. MLDs that perform IEEE 802. IX authentication use Open System authentication. MLDs that perform password-based authentication can use SAE authentication. MLDs that perform FILS use FILS authentication. SAE and FILS authentication provide mutual authentication and derivation of PMK. If Open System authentication is chosen instead, the supplicant or the authenticator initiates IEEE 802. IX authentication. Before IEEE 802. IX authentication and key installation are complete, IEEE 802. IX controlled ports in the AP MLD block all data frames. IEEE 802. IX uncontrolled ports allow IEEE 802. IX frames to pass between the supplicant and the authenticator. When SAE / FILS or IEEE Std 802. IX are used separately, whether SAE or FILS authentication with authentication frames or IEEE 802. IX authentication with post-data frames association, the authentication process creates shared encryption keys between the endpoints of the encryption (between the AP MLD and the non-AP MLD, or between the IEEE 802. IX AS (authentication server) and the non-AP MLD). When IEEE Std 802. IX is used, the AS delivers these keys to the AP MLD, and the AP MLD and the non-AP MLD complete the security association setup using one of the key confirmation handshakes, such as the 4-way handshake or the FT 4-way handshake over any of the links. When SAE authentication is used, there is no AS, so there is no key delivery; the 4-way handshake is performed directly between the AP MLD and the non-AP MLD. The key confirmation handshake indicates when the link has been protected by keys and is ready to allow normal data traffic and protected robust management frames. When FILS authentication is performed, the key confirmation is performed as part of the FILS exchange using association frames. Thus, no additional handshake is needed. The IEEE 802. IX controlled port is considered unblocked for the non-AP MLD as soon as the key confirmation handshake is completed for at least one link. After multi-link teardown, the IEEE 802. IX controlled port returns to the unauthenticated state and blocks all data frames.

[0107] In addition, a link state is also maintained for each (pair of STAs) / link, and the link state can be one of the following four states:

[0108] - Unestablished (not setup / not available): The AP MLD and the non-AP MLD do not have all the information to enable data operations with each other. Allowed frames depend on the MLD state. Data frames are not allowed. Access to the DS is not allowed.

[0109] - Established (or setup): The AP MLD and the non-AP MLD have all the information to enable data operations with each other. Data frames (except EAPOL frames) are not allowed. Access to the DS is not allowed.

[0110] - Enabled (activated): Both MLIDs agree to start data operations on the link. For example, at least one TID is mapped to the link, the security association (RSNA) for the link has been completed. All frames allowed by the TID mapping are allowed. Access to the DS is allowed.

[0111] - Disabled (deactivated): Data frames (except EAPOL frames) are not allowed. Non-data frames can be allowed. Access to the DS is not allowed.

[0112] For legacy STAs or non-MLD STAs, the regular authentication / association procedure can be used, and the state is maintained at the STA level. The multi-link establishment between a pair of MLIDs creates a unique pair of IEEE 802.1X ports, and the authentication happens only with respect to these ports. Essentially, for MLIDs, the roles of authenticator and supplicant can be enforced at the MLD level rather than at the STA level.

[0113] When a STA / link is in the unestablished state, even if the IEEE 802. IX controlled port is unblocked at the MLD's level, non-EOPAL data frames are not allowed for this link. A successful multi-link establishment (with the requested link) changes the state of the link from unestablished to established. A successful 4-way / group key handshake + TID-to-link mapping (with at least one TID mapped to this link) changes the state of the link from established to enabled. A successful TID-to-link mapping toggles between the enabled and disabled states. Multi-link teardown changes the MLD state to state 1 and all the attached STA / links to the unestablished state. In addition, while in both the established and disabled states, no TID is mapped to the STA / link, in the established state, security keys have not been generated for the STA / link. On the other hand, in the disabled state, security keys have been generated for the STA / link. However, in both states, no TID is mapped to the link and the AP cannot forward data frames from the link to the DS even if the IEEE 802. IX controlled port is unblocked.

[0114] Figure 18 An alternative state transition diagram is depicted according to a first embodiment, in which a link can be in one of four states: established state (MLD authenticated, associated, pending RSNA authentication, IEEE 802. IX controlled port blocked), enabled state (authenticated, associated, RSNA established or not needed, IEEE 802. IX controlled port unblocked, at least one TID mapped to the link), disabled state (MLD authenticated, associated, IEEE 802. IX controlled port unblocked, no TID mapped to the link), and unestablished state. The unestablished state includes 3 sub-states depending on the MLD state: unestablished-1 (MLD in state 1; only class 1 frames are allowed), unestablished-2 (MLD in state 2; only class 1 and 2 frames are allowed), unestablished-3 (MLD in state 3; classes 1, 2, 3 frames are allowed, but the link does not allow non-EOPAL data frames even if the IEEE 802. IX controlled port is unblocked at the MLD level).

[0115] According to the first embodiment, the MLD can also maintain a record of the link quality of all enabled links based on link quality measurements such as signal-to-noise ratio (SNR), packet error rate (PER), RSSI, etc. Figure 19A diagram depicting how link maintenance is carried out according to the first embodiment is depicted. For links with active transmissions, link quality can be measured based on the transmitted / received frames. For non-active links (in the wake power save state), management frames (i.e. solicited / unsolicited link measurement frames) can be periodically (i.e. once per beacon interval) transmitted to access the link quality. If the link quality is below a certain threshold, the link can be considered to be "down". No data frames can be allowed in a "down" link, or they can be transmitted with a lower MCS. The threshold can depend on the TID mapped to the link, the MCS requirements of the link, etc. On the other hand, if the link quality improves above the threshold, the link can be re-used as a normally enabled link. However, if the link quality remains below the threshold level for a certain TIMEOUT duration, the link can be disabled (i.e. by the TID to link mapping). Advantageously, this ensures that links are established based on link quality.

[0116] According to the second embodiment, the non-AP MLD can implicitly signal the links to be established during multi-link setup by including only information of the links for which it requests establishment (i.e. link capabilities, MAC addresses, etc.). Information of links for which establishment is not requested is not included in the multi-link setup request. For example, the setup request can include information indicating the capabilities information and MAC addresses of the non-AP MLD's affiliated STAs for which links are to be established only. This can be used as a default option to request establishment of links. Alternatively, link information can be provided but implicitly signal the request not to establish a link by setting a very low link quality value (i.e. for either or both of UL / DL, set the path loss to the maximum value (e.g. 128) or set the link margin to the minimum value (e.g. -128) for the concerned link). For example, the setup request can include information on the wireless channel quality of a plurality of links that can be established between the first plurality of STAs and the second plurality of STAs, and wherein the wireless channel quality is set to implicitly indicate one or more links to be established. Alternatively, as described in the previous embodiment, it is possible to provide an explicit request to establish a link in the multi-link setup frame.

[0117] If link quality information is not included in the multi-link setup request, the AP MLD can initiate link quality evaluation of the requested links including / excluding the links on which the multi-link request was received, before transmitting the multi-link setup response, to decide whether to establish the link or not. Figure 20A communication flow 2000 between an AP MLD 2002 and a non-AP MLD 2004 according to the second embodiment is described, including a link quality assessment step. After the non-AP MLD 2004 initiates multi-link setup by sending a multi-link request on link 2 to the AP MLD to request establishment of links 1, 2, and 3, the AP MLD 2002 initiates link quality assessment (prior to sending a multi-link setup response) by sending a link measurement request 2006 and 2010 on each of links 1 and 3. In this example, the link quality assessment of the requested links excludes the link on which the multi-link request was received (i.e., link 2), although the AP MLD can also choose to include that link. In response to the link measurement requests, the non-AP MLD 2004 sends a link measurement report 2008 to the AP MLD 2002 on link 1 (in response to link measurement request 2006) and a link measurement report 2012 to the AP MLD 2002 on link 3 (in response to link measurement request 2010). Based on the collected information of link quality provided by the link measurement reports 2008 and 2012, the AP MLD decides to establish / provision (at 2014) only links 1 and 2. Link 3 is rejected. Accordingly, the AP MLD 2002 sends a multi-link setup response indicating that links 1 and 2 are established.

[0118] The AP MLD 2002 can use the information about link quality to decide whether to establish / enable the requested links, especially in the case of TID restrictions on some links. However, any link quality assessment of the links needs to be performed so that the multi-link setup can be performed within any timeout value associated with the establishment. Further, it will be understood that while the example shown illustrates the use of link measurement request / response frames, any other suitable management frames can be used for this purpose. Figure 20 The example shown illustrates the use of link measurement request / response frames, although any other suitable management frames can be used for this purpose.

[0119] Figure 21 An alternative state transition diagram 2100 according to the second embodiment is depicted. The alternative state transition diagram 2100 contemplates alternative states for the MLD, where the states are maintained at each subordinate STA level of the MLD, similar to a legacy STA. Further, the roles of the authenticator and supplicant are implemented at the STA level (rather than at the MLD level). This version of the state machine can be used for SAE and FILS authentication, i.e., without using IEEE 802. IX authentication. At the same time, the links maintain their own states, which are the same as in the first embodiment.

[0120] For example, at 2102, both STAl and STA2 are in state 1 (unauthenticated, unassociated, class 1 frame, link not established). When the STA / link is in the unestablished state, the link does not allow data frames. A successful (multi-link) authentication brings the states of all the affiliated STAs (i.e., STAl and STA2) to state 2. However, the states of the excluded affiliated STAs remain in state 1. A successful multi-link setup (with the requested link) changes the state of the link from unestablished to established and changes the state of the corresponding affiliated STA to state 3. The unrequested links remain in the unestablished state and the corresponding affiliated STAs remain in state 1 or 2. For example, after a successful multi-link setup of the requested link 1 (corresponding to STAl) at 2106, STAl is in state 3 and STA2 is still in state 2. A successful 4-way / group key handshake + TID-to-link mapping (with at least 1 TID mapped to the link) changes the state of the link from established to enabled and changes the state of the corresponding affiliated STA to state 4. For example, at 2108, after a successful 4-way / group key handshake + TID-to-link mapping (with one or more TIDs mapped to link 1) from 2106, STAl is in state 4 and link 1 is enabled, while STA2 is still in state 2 and link 2 is still not established. At 2110, a successful multi-link reestablishment of link 2 brings STA2 from state 2 (i.e., link 2 is established) to state 3. A successful TID-to-link mapping toggles the link state between enabled and disabled, but does not change the state of the affiliated STAs. For example, at 2114 (from 2112), after a successful TID-to-link mapping (with one or more TIDs mapped to link 2, but no TIDs mapped to link 1) and a successful 4-way / group key handshake of link 2, STAl is still in state 4, although link 1 is disabled, and STA2 is now in state 4, with link 2 enabled. Alternatively, these state changes can occur from 2108 to 2114 after a successful multi-link reestablishment (i.e., of link 2), a successful TID-to-link mapping (with one or more TIDs mapped to link 2, but no TIDs mapped to link 1), and a successful 4-way / group key handshake of link 2. Further, at 2116, after a successful TID-to-link mapping (with one or more TIDs mapped to link 1, but no TIDs mapped to link 2) from 2114, both STAl and STA2 will be in state 4, with link 1 enabled, but link 2 disabled. It is also possible to go from 2116 back to 2114 with a successful TID-to-link mapping with one or more TIDs mapped to link 2, but no TIDs mapped to link 1.Further, the multi-link teardown brings the status of all the affiliated STAs to status 1 and all the links to the unestablished status, i.e., back to 2102.

[0121] In the present example, the difference between established and disabled is that in both cases, no TID is mapped to the link. In the established status, no security key can have been generated for the STA / link, but in the disabled status, a security key has been generated for the STA / link. However, in both statuses, no TID is mapped to the link and the AP can not forward data frames from the link to the DS.

[0122] According to a second embodiment, as part of the multi-link setup, the non-AP MLD can request which links are to be deleted (i.e., explicitly by using the deletion request field in the multi-link setup request element, or implicitly by indicating low channel quality). The non-AP MLD can also include information on the link quality of the links requested to be deleted (i.e., the UL / DL link margin obtained during the discovery, the UL / DL path loss, etc.). If the link quality information is not available, the RSSI / RCPI of the beacon / probe response frame received on the link can be included as an estimate of the link quality. The non-AP MLD can take into account the link quality information to make the decision of which links to request to be deleted. It can also take into account other factors, e.g., due to coexistence issues with its Bluetooth radio, the non-AP MLD can choose to request to delete the 2.4 GHz link, or it can choose not to request to delete certain links to save power, etc. Advantageously, this ensures that the links are established based on the request of the non-AP MLD and the link quality.

[0123] Figure 22 A diagram of the multi-link element 2200 for multi-link setup request and link deletion as described above is depicted. The action type field of the multi-link element 2200 is set to multi-link setup request. There can be one or more link information fields, such that there is one link information field for each established link. Each link information field can include a link ID subfield, a link MAC address subfield, a deletion request subfield, a UL link margin subfield, a UL path loss subfield, a DL link margin subfield, and a DL path loss subfield. The deletion request subfield can be used to indicate whether the related link is requested to be deleted (i.e., value 0 = not requested, value 1 = requested). For example, a value of 1 in the deletion request subfield will cause the related link to be removed from the multi-link set. The link quality information that can be included in the UL link margin subfield, the UL path loss subfield, the DL link margin subfield, and the DL path loss subfield is optional.

[0124] Alternatively, a multi-link teardown frame can also be used for link deletion. Referring to a diagram illustrating a multi-link teardown frame 2300, the action type field of the multi-link element 2300 is set to multi-link teardown. There can be one or more link information fields, such that there is one link information field for each established link. Each link information field can include a link ID subfield, a link MAC address subfield, and a deletion request subfield. The deletion request subfield can be used to indicate whether the related link is requested to be deleted (i.e., value 0 = not requested, value 1 = requested). For example, a value of 1 in the deletion request subfield will cause the related link to be removed from the multi-link set. Figure 23The multi-link action field is set to multi-link teardown (i.e., value of 1). There can be one or more link ID fields, such that there is one link ID field for each established link.

[0125] Link deletion moves the state of the link to unestablished. If each of the affiliated STAs is maintained in the connected state, the corresponding STA's state is also changed to state 1 (unauthenticated, unassociated). As long as one link remains in a state other than unestablished, the corresponding two MLDs are considered connected. If all links are torn down, the MLDs are no longer connected, and if the state is maintained at the MLD level, the MLD's state is changed to state 1.

[0126] According to a third embodiment, the AP MLD can limit the exchange of frames for multi-link setup to one of the links, i.e., on the link in the highest frequency band (e.g., 6 GHz), to ensure that the non-AP MLD is in range on all links. For example, it can be signaled during the discovery phase (e.g., in the beacon / probe response frames sent on the link, or in the (reduced) Neighbor Report element sent on the other links, etc.) whether or not the exchange of frames for multi-link setup is allowed on the link. Alternatively, it can also be possible for the AP MLD to attempt to ensure that its all affiliated APs' BSSs have more or less the same coverage range by controlling the transmit power of each affiliated AP. However, this can mean that the transmit power of the AP associated with the BSS in the lower frequency range (e.g., 2.4 GHz band) can be significantly lower than the transmit power of the AP associated with the BSS in the higher frequency range (e.g., 5 / 6 GHz). Thus, these can mitigate the range disparity issue, but can not mitigate other link quality issues.

[0127] Figure 24 A diagram 2400 depicting multi-link setup and link maintenance between an AP MLD and a non-AP MLD is depicted. According to one example, at step 2402, both MLDs are capable of operating on links 1, 2, and 3. Prior to initiating multi-link setup, the non-AP MLD STA can listen to beacons (passive scanning) or perform active scanning (exchange of probe request / response frames) on all 3 links and measure link quality. The non-AP MLD obtains authentication with the AP MLD by exchanging authentication frames or multi-link setup (authentication) frames on one of the links, i.e., link 3. At this stage, the MLDs are in state 2. The non-AP MLD initiates a multi-link setup request and requests to setup links 2 and 3 by sending a multi-link setup request frame on link 3. Link 1 is excluded from the request due to poor channel quality. The non-AP MLD can also include link quality information for links 2 and 3.

[0128] The AP MLD considers establishing links 2 and 3 and decides to establish both links. The AP MLD sends a multi-link setup response frame indicating that links 2 and 3 have been established. At this stage, the multi-link set consists of links 2 and 3. In this example, the AP uses the default TID-to-link mapping on all links and thus the multi-link setup response frame does not include any TID-to-link mapping information. Thus, at step 2404, the AP MLD and the non-AP MLD are now associated and the AP MLD records the relevant information of the non-AP MLD as well as the relevant information of links 2 and 3. No information of link 1 is recorded. At this stage, the MLD is in state 3 but the IEEE 802. IX controlled port is still blocked. Next, the IEEE 802. IX authentication is performed and security keys for links 2 and 3 are generated and distributed to the non-AP MLD. At this stage, the MLD is in state 4, the IEEE 802. IX controlled port is unblocked. At this stage, links 2 and 3 are considered enabled while link 1 remains in the unestablished state. At this stage, data and non-data frames can be exchanged on links 2 and 3.

[0129] After some time, the AP MLD notices that the link quality of link 2 has been below the AP threshold of the required quality of this link. It keeps monitoring the link and since the link quality remains below the required threshold for longer than a certain TIMEOUT duration, the AP decides to disable this link by performing a TID-to-link mapping that does not map any TID to link 2. This causes link 2 to be in the disabled state and all traffic to be switched to link 3 at step 2406.

[0130] Thereafter, both the AP MLD and the non-AP MLD keep monitoring the links and after some time, the link quality of both link 1 and link 2 improves above the necessary threshold. At this stage, either one of the MLDs (e.g., the non-AP MLD) requests the establishment of link 1 (i.e., adding link 1 to the multi-link set) by sending a multi-link setup request frame. The AP MLD accepts the request and link 1 is added to the multi-link set. At the same time, the AP MLD also maps TID 6 and TID 7 to both link 1 and link 2 at step 2408, causing both link 1 and link 2 to be switched to the enabled state. At this stage, data and non-data frames can be exchanged on links 1, 2 and 3.

[0131] According to another example, for the case where the state is maintained at the STA level, the multi-link operation can have little variation. For example, at step 2402, the affiliated STA, not the corresponding MLD, is in state 2. The non-AP MLD only requests to enable links 2 and 3 but it includes the information (i.e., capability information) of all 3 links.

[0132] The AP MLD considers all 3 links to be established and decides to establish all 3 links. It therefore sends a multi-link setup response frame indicating that link 1, link 2 and link 3 have been established. At this stage, the multi-link set consists of link 1, link 2 and link 3. However, the multi-link setup response frame includes a TID-to-link mapping element which maps all TIDs to only link 2 and link 3, with no TIDs being mapped to link 1. In this case, at step 2404, all 3 affiliated STAs are considered to be associated (i.e. in state 3), but only link 2 and link 3 are in the enabled state, while link 1 is in the established state. The parameters of all links (1 to 3) are recorded by the AP MLD and all legacy procedures related to association (AID allocation etc.) are performed for all links. However, secret key generation / distribution is only performed for the enabled links. Alternatively, it can be that only the affiliated STAs corresponding to the enabled links are considered to be associated (i.e. state 3), while the affiliated STAs corresponding to the other links are not considered to be associated (i.e. state 1 or 2). The parameters of all links (1 to 3) are recorded by the AP MLD, but all legacy procedures related to association (AID allocation etc.) and secret key generation / distribution are only performed for the enabled links.

[0133] Some time later, the AP MLD notices that the link quality of link 2 has fallen below the AP threshold of the required quality for this link. It keeps monitoring the link and, since the link quality remains below the required threshold for longer than a certain TIMEOUT duration, the AP decides to disable this link by performing a TID-to-link mapping which does not map any TIDs to link 2. This puts link 2 in the disabled state and all traffic is switched to link 3, i.e. at step 2406.

[0134] In addition to the steps 2408 described in the preceding example, the AP MLD can also perform the procedures related to association (AID allocation etc.) and secret key distribution as if they had not been completed at step 2404. Subsequent enabling / disabling will not require this and can be done via the TID-to-link mapping.

[0135] Figure 25A schematic diagram of an MLD 2500 is depicted in accordance with various embodiments. The MLD 2500 includes a MAC-SAP 2502 for accessing a distribution service (DS) via controlled and uncontrolled ports, optional IEEE 802. IX port controlled and uncontrolled filtering, a link activity monitoring module 2504, a link quality assessment module 2506, and a link state module 2508. The MLD 2500 also includes three affiliated STAs or stations, STA1 2510a, STA2 2510b, and STA3 2510c. Each STA includes a MAC layer and also a PHY layer from which transmissions occur via link 1 (for STA1 2510a), link 2 (for STA2 2510b), and link 3 (for STA3 2510c). It will be understood that the MLD 2500 can be an AP MLD (STA 1-3 are affiliated APs) or a non-AP MLD (STA 1-3 are affiliated non-AP STAs), and the number of links and affiliated STAs or stations can be further extended.

[0136] Figure 26 A flow diagram 2600 illustrating a method of communication is shown in accordance with various embodiments. At step 2602, a request frame is generated at a first STA included in a first plurality of STAs affiliated to a first MLD, the request frame including request information. At step 2604, the request frame is transmitted to a second STA to request a multi-link setup, wherein the second STA is included in a second plurality of STAs affiliated to a second MLD, and wherein the multi-link setup establishes one or more links between one or more of the first plurality of STAs and a corresponding one or more of the second plurality of STAs based on the request information.

[0137] Figure 27 A schematic partial cutaway view of a STA 2700 in accordance with the first through third embodiments is shown, which can be implemented for multi-link setup and link maintenance. In accordance with various embodiments, the STA 2700 can be implemented as a STA or an AP included in a plurality of STAs or APs affiliated to an AP MLD or a non-AP MLD.

[0138] Various functions and operations of the STA 2700 are arranged into layers in accordance with a layered model. In this model, lower layers report to and receive instructions from higher layers in accordance with IEEE specifications. Details of the layered model are not discussed in this disclosure for the sake of brevity.

[0139] As shown in Figure 27 The STA 2700 can include circuitry 2714, at least one radio transmitter 2702, at least one radio receiver 2704, and a plurality of antennas 2712 (for the sake of brevity, for the sake of illustration, only one antenna 2712 is shown in FIG. 27), in accordance with various embodiments.Figure 27 The circuitry can include at least one controller 2706 for software and hardware aided execution of tasks that the controller 2706 is designed to perform, including control of communications with one or more other multi-link devices in a MIMO wireless network. The at least one controller 2706 can control at least one transmit signal generator 2708 for generating multi-link action frames to be transmitted by the at least one radio transmitter 2702 to one or more other STAs or MLDs, and at least one receive signal processor 2710 for processing multi-link action frames received by the at least one radio receiver 2704 from one or more other STAs or MLDs. The at least one transmit signal generator 2708 and the at least one receive signal processor 2710 can be independent modules of the STA 2700 that communicate with the at least one controller 2706 for the above-described functions. Alternatively, the at least one transmit signal generator 2708 and the at least one receive signal processor 2710 can be included in the at least one controller 2706. It will be apparent to those skilled in the art that the arrangement of these functional modules is flexible and can vary depending on the actual needs and / or requirements. Data processing, storage, and other related control apparatus can be provided on appropriate circuit boards and / or in chip sets.

[0140] In various embodiments, the at least one radio transmitter 2702, the at least one radio receiver 2704, and the at least one antenna 2712 can be controlled by the at least one controller 2706. Further, while only one radio transmitter 2702 is shown, it will be understood that there can be more than one such transmitter.

[0141] In various embodiments, the at least one radio receiver 2704 together with the at least one receive signal processor 2710 form a receiver of the STA 2700. The receiver of the STA 2700 provides the functionality needed for multi-link communications. While only one radio receiver 2704 is shown, it will be understood that there can be more than one such receiver.

[0142] The STA 2700 provides the functionality needed for multi-link setup and link maintenance. For example, the STA 2700 can be a first STA included in a first plurality of STAs affiliated with a first MLD. The circuitry 2714 can generate a request frame including request information. The transmitter 2702 can transmit the request frame to a second STA to request a multi-link setup, where the second STA is included in a second plurality of STAs affiliated with a second MLD, and where the multi-link setup establishes one or more links between one or more STAs in the first plurality of STAs and a corresponding one or more STAs in the second plurality of STAs based on the request information.

[0143] The request information can identify one or more STAs of the first plurality of STAs. The request frame can further include information regarding a wireless channel quality of each of the one or more links. The first plurality of STAs can collect the information regarding the wireless channel quality of each of the one or more links prior to transmitting the request frame, and wherein the wireless channel quality includes one or more of a link margin, a path loss, a received signal strength indication (RSSI), and a received channel power indication (RCPI). The request information can further include information regarding a wireless channel quality of the plurality of links that can be established between the first plurality of STAs and the second plurality of STAs, and wherein the wireless channel quality is set to implicitly indicate the one or more links to be established. The first MLD can be a non-AP MLD and the second MLD can be an AP MLD.

[0144] For example, the STA 2700 can be a second STA included in a second plurality of STAs affiliated with a second multi-link device (MLD). The receiver 2704 can receive a request frame from a first STA, where the first STA is included in a first plurality of STAs affiliated with a first MLD, and where the request frame includes request information and is requesting a multi-link setup that sets up one or more links between one or more of the first plurality of STAs and a corresponding one or more of the second plurality of STAs based on the request information. The transmitter 2702 can transmit a response frame to the first STA to inform a result of the multi-link setup, where the response frame carries information of the one or more links that have been set up between the one or more of the first plurality of STAs and the corresponding one or more of the second plurality of STAs.

[0145] The request information can identify one or more STAs of the first plurality of STAs. The information of the one or more links can include operating parameters of the one or more links and capability information of one or more STAs of the second plurality of STAs corresponding to the one or more links. The response frame can further include information mapped to a traffic identifier (TID) of each link of the one or more links, and wherein the first plurality of STAs are only allowed to send frames on each link that belong to the one or more TIDs mapped to the link. The request information can include information on a wireless channel quality of the one or more links, and wherein the second MLD decides whether to setup the one or more links based on the information. The response frame can further include information related to block acknowledgement parameters of the setup links. The second MLD can be an AP MLD and the first MLD can be a non-AP MLD, wherein a frame including information identifying a common MAC address of the AP MLD can be sent by a STA included in the second plurality of STAs to advertise the AP MLD, the frame being one of a beacon frame or a probe response frame. A frame indicating an AP of the second plurality of STAs to which the request frame should be addressed can be sent by a STA included in the second plurality of STAs to advertise the AP MLD, the frame being one of a beacon frame or a probe response frame.

[0146] The present disclosure can be realized by software, hardware, or a combination of software and hardware. Each functional block used in the description of each embodiment described above can be partly or entirely realized by an LSI such as an integrated circuit, and each process described in each embodiment can be controlled partly or entirely by the same LSI or a combination of LSIs. The LSI can be individually formed of chips, or one chip can be formed to include a part or all of the functional blocks. The LSI can include a data input and output coupled thereto. The LSI here can be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on a difference in the integration level. However, the technique of implementing an integrated circuit is not limited to the LSI, and can be realized by using a dedicated circuit, a general-purpose processor, or a special-purpose processor. In addition, a FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor in which the connections and settings of circuit cells disposed inside the LSI can be reconfigured can be used. The present disclosure can be realized as a digital processing or an analog processing. If future integrated circuit technology replaces LSIs as a result of the advancement of semiconductor technology or other derivative technology, the functional blocks could be integrated using the future integrated circuit technology. Biotechnology can also be applied.

[0147] The present disclosure can be realized by any kind of apparatus, device, or system (referred to as a communication device) having a communication function.

[0148] The communication device may include a transceiver and processing / control circuitry. The transceiver may include and / or act as a receiver and transmitter. As a transmitter and receiver, the transceiver may include an RF (radio frequency) module, which includes an amplifier, an RF modulator / demodulator, etc., and one or more antennas.

[0149] Some non-limiting examples of such communication devices include telephones (e.g., cellular phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital cameras / camcorders), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smartwatches, tracking devices), game consoles, digital book readers, remote health / telemedicine (remote health and medical) devices, and vehicles that provide communication capabilities (e.g., cars, airplanes, ships), and various combinations thereof.

[0150] Communication devices are not limited to portable or mobile devices, but may also include any kind of non-portable or fixed device, equipment or system, such as smart home devices (e.g., appliances, lighting, smart meters, control panels), vending machines and any other “thing” in an “Internet of Things” network.

[0151] Communication may include the exchange of data through, for example, cellular systems, wireless LAN systems, satellite systems, and various combinations thereof.

[0152] The communication device may include means, such as a controller or sensor, coupled to a communication means that performs the communication functions described in this disclosure. For example, the communication device may include a controller or sensor that generates control signals or data signals used by the communication means performing the communication functions of the communication device.

[0153] Communication equipment may also include infrastructure such as base stations, access points, and any other devices, equipment, or systems that communicate with or control devices such as those in the non-limiting examples above.

[0154] A non-limiting example of a station may be a station included in a first plurality of stations attached to a multi-link station logical entity (i.e., such as an MLD), wherein, as part of the first plurality of stations attached to the multi-link station logical entity, the stations of the first plurality of stations share a common media access control (MAC) data service interface with the upper layer, wherein the common MAC data service interface is associated with a common MAC address or traffic identifier (TID).

[0155] Therefore, it can be seen that this embodiment provides a communication device and method for operating on multiple links in order to fully realize the throughput gain of multi-link communication, especially for multi-link guaranteed retransmission.

[0156] While the foregoing detailed description has set forth exemplary embodiments, it will be appreciated that numerous variations can be made. It will be further appreciated that the exemplary embodiments are illustrative and not limiting of the scope, spirit, or character of the disclosure. Rather, the exemplary embodiments are amenable to various changes and modifications, and the scope of the disclosure is not limited to the specific details set forth above. Accordingly, it is intended that all changes and modifications that fall within the scope of the subject matter recited in the claims appended hereto be embraced by the scope of the disclosure.

[0157] According to an example, there is a second STA included in a second plurality of STAs affiliated with a second multi-link device (MLD), the second STA comprising: a receiver that receives a request frame from a first STA, wherein the first STA is included in a first plurality of STAs affiliated with a first MLD, and wherein the request frame includes request information and is requesting a multi-link setup that sets up 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 inform a result of the multi-link setup, wherein the response frame carries information of the one or more links that have been set up between the one or more STAs of the first plurality of STAs and the corresponding one or more STAs of the second plurality of STAs.

[0158] According to an example, the second STA, wherein the request information identifies the one or more STAs of the first plurality of STAs.

[0159] According to an example, the second STA, wherein the information of the one or more links includes operating parameters of the one or more links and capability information of the one or more STAs of the second plurality of STAs corresponding to the one or more links.

[0160] According to an example, the second STA, wherein the response frame further includes information mapped to a traffic identifier (TID) of each of the one or more links, and wherein the first plurality of STAs is only allowed to transmit frames belonging to the one or more TIDs mapped to each link on the link.

[0161] According to an example, the second STA, wherein the request information includes information about wireless channel quality of the one or more links, and wherein the second MLD decides whether to set up the one or more links based on the information.

[0162] According to an example, the second STA, wherein the response frame further includes information related to block acknowledgement parameters of the set up links.

[0163] According to an example, the second STA, wherein the second MLD is an AP MLD and the first MLD is a non-AP MLD; and

[0164] wherein the frame including the information identifying the common MAC address of the AP MLD is transmitted by a STA included in the second plurality of STAs to announce to the AP MLD that the frame is one of a beacon frame or a probe response frame.

[0165] According to an example, the second STA, wherein the frame indicating that the request frame should be addressed to an AP of the second plurality of STAs is transmitted by a STA included in the second plurality of STAs to announce to the AP MLD that the frame is one of a beacon frame or a probe response frame.

Claims

1. A first STA included in a first plurality of station STAs attached to a non-access point (non-AP) multi-link device (MLD), the first STA comprising: A circuit that generates an association request frame, the association request frame including request information identifying the requested link for the establishment of multiple links and link-specific information indicating the traffic parameters of the requested link. as well as A transmitter sends the association request frame to a second STA to request the establishment of a multi-link between a non-AP MLD and an access point AP MLD, wherein the second STA is included in a second plurality of STAs attached to the AP MLD, and wherein the multi-link establishment establishes one or more links between one or more STAs in the first plurality of STAs and corresponding one or more STAs in the second plurality of STAs based on the request information and the link-specific information. The association request frame includes a multi-link element, which includes an MLD MAC address field for indicating the MLD MAC address of the non-AP MLD and a link information field for each link in the requested links. Each link information field includes link-specific information, which includes a link MAC address field indicating the MAC address of the corresponding link in the requested links.

2. The first STA according to claim 1, wherein the association request frame includes a multi-link element, the multi-link element including one or more link information fields, each link information field indicating one of the requested links and its link-specific information.

3. The first STA according to claim 1, wherein the link-specific information includes the operating parameters of the requested link.

4. The first STA according to claim 1, wherein the link-specific information is information about the radio channel quality of each link in the requested links, including one or more of link margin, path loss, received signal strength indicator (RSSI), and received channel power indicator (RCPI).

5. The first STA according to claim 1, wherein prior to the establishment of the multi-link, The circuit generates an authentication frame that includes the MAC address identifying the non-AP MLD; and The transmitter sends the generated authentication frame to the AP MLD for multi-link authentication.

6. The first STA according to claim 1, wherein the transmitter sends a reassociation request frame to one of the second plurality of STAs to establish a new link between the non-AP MLD and the AP MLD, wherein the new link is independent of one or more existing links.

7. The first STA of claim 1, wherein the link-specific information includes traffic information regarding the desired traffic characteristics of each link in the requested links, the traffic characteristics being one of a Traffic Identifier (TID), payload size, delay limit, data rate, and minimum PHY rate.

8. The first STA according to claim 1, further comprising a receiver for receiving associated response frames indicating that one or more links are accepted by the AP MLD.

9. The first STA of claim 8, wherein the receiver receives the association response frame on the link on which the association request frame was sent.

10. The first STA according to claim 1, wherein, The link-specific information also includes information about the link quality of the corresponding link in the requested link.

11. A communication method for a first STA included in a first plurality of station STAs attached to a non-access point (non-AP) multi-link device (MLD), comprising: Generate an association request frame, the association request frame including request information identifying the requested link established for multiple links and link-specific information indicating the traffic parameters of the requested link; as well as The association request frame is sent to the second STA to request the establishment of a multi-link between the non-AP MLD and the access point AP MLD, wherein the second STA is included in a second plurality of STAs attached to the AP MLD, and wherein the multi-link establishment establishes one or more links between one or more STAs in the first plurality of STAs and corresponding one or more STAs in the second plurality of STAs based on the request information and the link-specific information. The association request frame includes a multi-link element, which includes an MLD MAC address field for indicating the MLD MAC address of the non-AP MLD and a link information field for each link in the requested links. Each link information field includes link-specific information, which includes a link MAC address field indicating the MAC address of the corresponding link in the requested links.

Images