Communication apparatus and communication method for multi-link traffic indication map

Abstract

To reduce the overhead required for signaling additional information about buffered BUs in WLAN networks that contain MLDs.SOLUTION: A station (STA) is an STA of multiple stations (STAs) belonging to a non-AP Multi-Link Device (MLD), each of the STAs operating in a corresponding link of the non-AP MLD. The STA includes: a receiving unit which receives a frame comprising a traffic indication map (TIM) element and starting AID information, the TIM element including a partial virtual bitmap (PVM) indicating the presence of one or more buffered units (BUs) for the non-AP MLD, the starting AID information indicating the smallest AID for which additional information relating to one or more BUs is present in the frame; and circuitry which processes receiving the frame.SELECTED DRAWING: Figure 18

Description

[Technical field]

[0001] The present embodiments relate to communication devices, and more particularly, to a method and device supporting a multi-link traffic indication map. [Background technology]

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

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

[0004] In multilink operation between an access point (AP) multilink device (MLD) and a non-AP MLD, a traffic indication map (TIM) element is conveyed, such as in a beacon frame or a TIM frame, to indicate buffered traffic (BU) for associated non-AP STAs operating in power save (PS) mode. Unlike single-link operation, in multilink operation, the BU indication in the TIM element alone does not provide additional information about the BU, such as the recommended link to acquire the BU, or the TID associated with the BU. Methods for signaling additional information about the buffered BU, such as link mapping, link set indication with link recommendation, traffic identifier (TID), etc., can be used, but in order for the non-AP MLD to properly locate itself in the link / TID information set, an additional bitmap is required for each bit set to 1 in the TIM element, regardless of the method used, as described below.

[0005] Therefore, what is needed is a communication device and method that supports a multi-link traffic indication map to address the above-mentioned problems and reduce the overhead required to signal additional information about buffered BUs in a WLAN network that includes MLD. Furthermore, other desirable features and characteristics will become apparent from the following detailed description and appended claims, taken in conjunction with the accompanying drawings and the Background section of this disclosure. [Means for solving the problem]

[0006] Non-limiting and illustrative embodiments facilitate providing a communications apparatus and method that supports a multi-link traffic indication map.

[0007] In a first embodiment, the present disclosure provides an AP among a plurality of access points (APs) belonging to an AP multi-link device (MLD), each of the plurality of APs operating on a corresponding link of the AP MLD, the AP comprising the following components: a circuit that, in operation, generates a frame including a traffic indication map (TIM) element and a presence bitmap, wherein the TIM element includes a partial virtual bitmap (PVM) indicating the presence of one or more buffered units for one of a non-AP STA or a non-AP MLD associated with the AP or the AP MLD, and the presence bitmap indicates whether additional information related to one or more BUs is present in the frame intended for one of the non-AP STAs or the non-AP MLD, and a transmitter that, in operation, transmits the frame on the link.

[0008] In a second embodiment, the present disclosure provides a station (STA), among a plurality of stations (STAs) belonging to a non-access point (non-AP) multi-link device (MLD) associated with an AP MLD, each of the plurality of STAs operating on a corresponding link of the non-AP MLD, the STA comprising the following components: a receiver that, in operation, receives a frame on the link, the frame including a traffic indication map (TIM) element and a presence bitmap, the TIM element including a partial virtual bitmap (PVM) indicating the presence of one or more buffered units for the non-AP MLD, and the presence bitmap indicating whether additional information related to one or more BUs is present in the frame targeted for the non-AP MLD; and a circuit that, in operation, processes the frame.

[0009] In a third embodiment, the present disclosure provides a communication method, the method including: generating a frame including a traffic indication map (TIM) element and a presence bitmap, where the TIM element includes a partial virtual bitmap (PVM) indicating the presence of one or more buffered units for one of a non-AP STA or a non-AP MLD associated with an AP or an AP MLD, and the presence bitmap indicates whether additional information related to one or more BUs is present in the frame targeted to one of the non-AP STAs or the non-AP MLD; and transmitting the frame on a link.

[0010] Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. These benefits and / or advantages may be obtained individually by the various embodiments and features of the specification and drawings, and it is not necessary for all of the embodiments and features to be provided in order to obtain one or more of such benefits and / or advantages. [Brief description of the drawings]

[0011] The accompanying drawings, together with the following detailed description, are incorporated in and constitute a part of this specification, and serve to illustrate various embodiments and to explain various principles and advantages according to the present embodiments. Throughout the different drawings, like reference numbers indicate identical or functionally similar elements. [Figure 1] 1 shows a TIM element and its Bitmap Control field. [Diagram 2] 1 shows a schematic diagram illustrating communication between AP MLD and non-AP MLD for multi-link power management and traffic direction. [Diagram 3] 1 shows a TIM bitmap and a set of link mapping bitmaps (LMBs). [Figure 4]The TIM bitmap and link recommendation (LR) elements are shown. [Diagram 5] 5 shows a TIM bitmap 500 in a TIM element, a multi-link (ML)-TIM element, and an LR element. [Figure 6] 1 shows a TIM bitmap and a traffic identifier (TID) bitmap. [Figure 7] 3 shows the TIM bitmap and the TID indication. [Figure 8] 8 shows a schematic diagram illustrating an exemplary configuration of a communication device 800 according to the present disclosure. [Figure 9] 1 shows a flowchart illustrating a communication method corresponding to a multi-link traffic map according to various embodiments of the present disclosure. [Figure 10] 1 shows an exemplary beacon / TIM frame. [Figure 11] 1 shows an exemplary associated identifier (AID) assignment and three exemplary TIM bitmaps transmitted by AP-MLD on three links, respectively. [Figure 12] 1 shows an exemplary TIM bitmap, an exemplary LMB presence bitmap, and an exemplary LMB set in a TIM frame / beacon frame. [Figure 13] 1 shows an example TIM bitmap, an example LR presence bitmap, and an example LR bitmap set in a TIM frame / beacon frame. [Figure 14] 1 shows an example TIM bitmap, an example linkset presence bitmap, an example linkset bitmap set, and an example LR bitmap set in a TIM frame / beacon frame. [Figure 15] 1 illustrates an exemplary TIM bitmap, an exemplary TID information presence bitmap, and an exemplary TID information bitmap set in a TIM frame / beacon frame. [Figure 16] 1 shows an example TIM bitmap, an example AC information presence bitmap, and an example AC information bitmap set in a TIM frame / beacon frame. [Figure 17] 1 shows an exemplary AID assignment and three exemplary TIM bitmaps transmitted from the AP MLD on three links respectively. [Figure 18] 1 shows an exemplary beacon / TIM frame. [Figure 19] 1 illustrates an exemplary TIM bitmap and an exemplary LMB set in a beacon / TIM frame. [Figure 20] 2 illustrates another exemplary beacon / TIM frame. [Figure 21] 1 illustrates an exemplary TIM bitmap, an exemplary TID information presence bitmap, and an exemplary TID information bitmap set in a beacon frame / TIM frame. [Figure 22] 1 illustrates an exemplary TIM bitmap transmitted on a link from an AP MLD, and an exemplary format of an AC information present bitmap and an AC information bitmap set. [Figure 23] 23 shows an example format of the TIM bitmap, the TID information present bitmap 2304, and the TID information bitmap set in a beacon / TIM frame. [Figure 24] 1 illustrates an exemplary format of a Multi-link TIM element. [Diagram 25] 1 illustrates an exemplary TIM bitmap, an exemplary multilink TIM bitmap, an exemplary AC information presence bitmap, and an exemplary AC information bitmap set in a beacon / TIM frame. [Figure 26] 1 illustrates an exemplary format of a Multi-link TIM element that includes a Multi-link TIM bitmap. [Figure 27]1 illustrates an exemplary configuration of a communication device and three communication units belonging to the communication device, the communication device being implemented as an AP MLD, each of which may be implemented as an AP configured to support a multilink traffic indication map according to the present disclosure. [Figure 28] 1 illustrates an exemplary configuration of a communication device and three communication units belonging to the communication device, the communication device being implemented as a non-AP MLD, each of which may be implemented as a STA configured to support a multilink traffic indication map according to the present disclosure.

[0012] Those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale For example, the dimensions of some elements in the illustrations, block diagrams or flow charts may be exaggerated relative to other elements to facilitate an accurate understanding of the embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The following detailed description is merely illustrative and is not intended to limit the embodiments or the application and uses of the embodiments. Moreover, it is not intended to be bound by any theory presented in the preceding Background or Detailed Description sections. Moreover, other desirable features and characteristics will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the background of this disclosure.

[0014] In the context of IEEE 802.11 (Wi-Fi) technology, a station (also synonymously referred to as a STA) is a communication device capable of using the 802.11 protocol. Based on the definition of IEEE 802.11-2020, a STA can be any device that includes an IEEE 802.11-compliant medium access control (MAC) and physical layer (PHY) interface to the wireless medium (WM).

[0015] For example, a STA may be a laptop, desktop personal computer (PC), personal digital assistant (PDA), access point (AP) or Wi-Fi phone in a wireless local area network (WLAN) environment. A STA may be fixed or mobile. In a WLAN environment, the terms "STA", "wireless client", "user", "user device", and "node" are often used synonymously.

[0016] Similarly, an AP (also known synonymously as a wireless access point (WAP) in the context of IEEE 802.11 (Wi-Fi) technology) is a communications device that allows STAs in a WLAN to connect to a wired network. APs are usually connected to a router (through the wired network) as standalone devices, but can also be built into or used in a router.

[0017] As mentioned above, a STA in a WLAN may function as an AP in some cases, and vice versa, because a communication device in the context of IEEE 802.11 (Wi-Fi) technology may include both STA and AP hardware components. In this way, the communication device may switch between STA and AP modes based on the conditions and / or requirements of the actual WLAN.

[0018] In various embodiments of the present disclosure, a multi-link device (MLD) refers to a device that operates in two or more frequency bands or links (2.4 GHz, 5 GHz, or 6 GHz). An MLD can include two or more communication devices corresponding to two or more links, each communication device operating in a particular frequency band or link. For simplicity, each link of the MLD shown in this disclosure is associated with one of many communication devices belonging to that MLD, which operate in a particular frequency band (2.4 GHz, 5 GHz, or 6 GHz) and are primarily configured to transmit / receive signals to / from another communication device (operating in that particular frequency band) that does not belong to that MLD.

[0019] In various embodiments of the present disclosure, unless otherwise specified, non-MLD STA, 11n STA, 11ac STA, or 11ax STA refers to legacy (HE / VHT / HT) STA or EHT STA that does not belong to MLD. Similarly, non-MLD AP refers to EHT AP that does not belong to MLD.

[0020] In various embodiments of the present disclosure, a partial virtual bitmap (PVM) field refers to a bitmap of Traffic Indication Map (TIM) elements conveyed in frames transmitted on a link by an AP or AP MLD, and the terms "PVM" or "partial virtual bitmap" are used as synonyms for TIM bitmap.

[0021] A Traffic Indication Map (TIM) element is carried in a beacon frame to indicate buffered traffic (BU) for non-AP STAs operating in a power save (PS) mode. Figure 1 shows a TIM element and a Bitmap Control field of the TIM element 100. The TIM element 100 includes an Element identifier (ID) field, a Length field, a Delivery TIM (DTIM) Count field, a DTIM Period field, a Bitmap Control field 102, and a Partial Virtual Bitmap (PVB) field. The Bitmap Control field 102 includes a Traffic Indicator field and a Bitmap Offset field. The Length field is set to (N1+N2)+4, where N1 is the largest even number such that bits numbered 1 to (N1×8)−1 in the Traffic Indication Virtual Bitmap are all 0, and N2 is the smallest number such that bits numbered (N2+1)×8 to 2007 in the Traffic Indication Virtual Bitmap are all 0, and N1 and N2 are used to signal the actual range of the TIM bitmap conveyed in the PVB field when the TIM bits at both ends of the AID range are all set to 0. The PVB field is set to 1 for an AID to indicate that there are BUs buffered for that AID. The Traffic Indicator is set to 1 in a TIM element with the DTIM Count field set to 0 when one or more group-addressed Media Access Control (MAC) Service Data Units (MSDUs) / MAC Management Protocol Data Units (MMPDUs) are buffered at the AP.When one or more group-addressed MSDUs / MMPDUs are buffered at the AP, the DTIM Count field is set to 1 in TIM elements that have the DTIM Count field set to 0. The Bitmap Offset field contains the value N1 / 2.

[0022] In multi-link power management, each STA of a non-AP MLD operating on an active link maintains its own power management mode and power state. Each STA of a non-AP MLD can independently change its power management mode or power state. Figure 2 shows a schematic diagram 200 illustrating communication between an AP MLD 202 and a non-AP MLD 204 for multi-link power management and traffic direction. If the STAs (e.g., STA1, STA2) of the non-AP MLD 204 operating on an active link are operating in active mode or power save mode awake state (e.g., the value of the PM (Power Management Mode) field is set to 0), frame exchange is possible on the link, but if the AP MLD 202 has buffered traffic (BU) for the associated non-AP MLD 204 affiliated STAs (e.g., STA1, STA2) (the affiliated STAs are operating in power save mode doze state (e.g., the value of the PM (Power Management Mode) field is set to 1)), the corresponding affiliated AP (e.g., AP1, AP2) on the AP MLD 202 side uses the TIM element carried in the beacon frame to indicate the buffered traffic for the non-AP MLD 204.

[0023] TID-Link Mapping is a new mechanism introduced in 802.11be that allows AP MLD and non-AP MLD that performed multi-link setup to determine how TIDs are mapped to established links in downlink (DL) and uplink (UL). By default, all TIDs are mapped to all established links in both UL and DL. If a TID is mapped to a link in a particular direction (DL / UL), transmission of frames belonging to that TID is allowed in that direction.

[0024] An established link is defined as valid if at least one TID is mapped to it, and invalid if no TID is mapped to it. At any point in time, a TID is always mapped to at least one established link, unless admission control is used. By default, all TIDs are mapped to all established links, and therefore all established links are valid.

[0025] If a TID is mapped to a set of valid links for a non-AP MLD in the UL, the non-AP MLD can use any link in this set of valid links to transmit frames carrying MSDUs or A-MSDUs (aggregation MSDUs) with that TID. If a TID is mapped to a set of valid links for a non-AP MLD in the DL, the non-AP MLD can obtain buffered BUs corresponding to that TID on any link in this set of valid links, while the AP MLD can transmit frames carrying MSDUs or A-MSDUs with that TID using any link in this set of valid links, subject to existing restrictions on frame transmission that apply to those valid links.

[0026] Conventionally, the TIM element is used as is. For non-AP MLD, a TIM bit is assigned for each non-AP MLD regardless of the number of links established, i.e., one AID is assigned to the non-AP MLD across all links. The TIM bit of the non-AP STA / MLD is set to 0 if the AP MLD has no buffered frames to send to the non-AP STA / MLD, and is set to 1 if the AP MLD has one or more buffered frames to send to the non-AP STA / MLD on any link used. According to the IEEE 802.11-2020 specification, any value in the range of 1 to 2007 can be used as the AID of the associated STA, but in various examples used in this disclosure, the AP MLD assigns AIDs to the associated non-AP STAs and non-AP MLDs within the AID range of 1 to 255.

[0027] In addition to the traditional TIM element, another element carrying, for example, the LMB, is defined to indicate the buffered data to link mapping for each non-AP MLD that has its TIM bit set to 1.

[0028] FIG. 3 shows a TIM bitmap 300 and a set of LMBs 302 in a TIM element. Each bit in the TIM bitmap, except AID 0, corresponds to an AID of a non-AP STA / MLD. The TIM bits corresponding to AIDs 12, 28, 35, 57, and 77 are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to the corresponding STA / MLD associated with the AID. For each bit set to 1 in the TIM bitmap 300, there is one LMB. In this case, the non-AP MLD calculates the position of its LMB in the LMB set 302 based on the order of the bits set to 1 in the TIM bitmap 300. Conventionally, an LMB is also needed for legacy STAs so that the non-AP MLD can correctly find its LMB, because it cannot identify the legacy STAs based on the TIM bitmap 300. In one example, the number of bits for one LMB corresponds to the number of valid links of the non-AP MLD.

[0029] When the non-AP MLD sees in the TIM element that the TIM bit corresponding to its AID is set to 1, it further checks the LMB corresponding to that AID to identify the particular link(s) to which the buffered traffic is mapped. For example, the non-AP MLD with AID 28 sees that the AP MLD has buffered traffic on one of its enabled links because its TIM bit is set to 1. The non-AP MLD then sees that its LMB is second in order (second bit set to 1 in the TIM bitmap) and checks the second LMB in the set of LMBs 302. The non-AP MLD then sees that the second and third bits of its LMB are set to 1, indicating that the AP MLD has buffered traffic for the non-AP MLD on link 2 and link 3.

[0030] In another conventional example, AIDs are assigned to non-AP MLDs, and a TIM element indicates the BU status of each non-AP MLD. In the default TID-link mapping, the TID is mapped to all valid links. When the bit in the TIM element corresponding to the AID of a non-AP MLD is set to 1, the non-AP MLD can obtain buffered data through any of the valid links, but the AP MLD can indicate a recommended link(s) using the LR element. In the LR element, a bitmap is assigned to the non-AP MLD, and each bit in the bitmap corresponds to a link and indicates whether the link is recommended for use.

[0031] 4 illustrates a TIM bitmap 400 and an LR element 402. In the TIM bitmap 400, the TIM bits (bit 1 and bit 3) associated with the AID of non-AP MLD 1 and the AID of non-AP MLD 3 are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to non-AP MLD 1 and non-AP MLD 3. The LR element 402 includes a bitmap for each bit set to 1 in the TIM bitmap 400, where bitmap 1 and bitmap 3 indicate the recommended links for non-AP MLD 1 and non-AP MLD 3, respectively. In one example, the number of bits in the LR bitmap corresponds to the number of valid links for the non-AP MLD. Bitmap 1 has values ​​"1", "0", "0", indicating that the first link is recommended for non-AP MLD 1 to obtain buffered frames from the AP MLD. Bitmap 3 has values ​​"0", "0", and "1", indicating that the third link is recommended for non-AP MLD 3 to retrieve buffered frames from the AP MLD.

[0032] Besides the default TID-link mapping, more than one link can be grouped into one link set and different TIDs can be mapped to different link sets. A new Multi-Link (ML) TIM element can be used to indicate the BU status of different link sets. A bitmap in the ML TIM element is assigned to non-AP MLDs. Each bit in the bitmap is mapped to a link set to indicate the BU status, e.g., set to 1 if one or more BUs exist for the link set and set to 0 if no BUs exist. The LR element can also be used to indicate the recommended link in a link set.

[0033] 5 illustrates a TIM bitmap 500, an ML-TIM element 502, and an LR element 504. TIDs 0-3 are mapped to a first link set consisting of link 1 and link 2, while TIDs 4-7 are mapped to a second link set consisting of link 3. The TIM bits (bit 1 and bit 2) corresponding to the AIDs of non-AP MLD 1 and non-AP MLD 2 are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to non-AP MLD 1 and non-AP MLD 2. The ML-TIM element 502 includes a bitmap for each bit set to 1 in the TIM element, where bitmap 1 and bitmap 2 indicate the BU state of the different link sets for non-AP MLD 1 and non-AP MLD 2, respectively. The number of bits in the ML-TIM bitmap 502 corresponds to the number of link sets. Bitmap 1 has values ​​"1" and "0", indicating that the first link set has a BU for non-AP MLD 1, and bitmap 2 has values ​​"0" and "1", indicating that the second link set has a BU for non-AP MLD 2.

[0034] LR element 504 further includes bitmaps indicating the recommended links in the link sets, where Bitmap 1 has values ​​"0", "1", indicating that the second link in Link Set 1 (i.e., Link 2 for non-AP MLD 1) is the recommended link. Bitmap 2 indicates a second link set for non-AP MLD 2, and because the second link set contains only one link (Link 3), Link 3 is recommended for non-AP MLD 2 and no separate LR element is required.

[0035] In yet another conventional example, non-AP MLDs are assigned AIDs and the TIM element indicates the BU status of each non-AP MLD. The TID bitmap (8 bits per TID) for each bit set to 1 for a non-AP MLD in the TIM element indicates the TIDs for which the AP MLD has one or more BUs for the non-AP MLD. Each bit in the TID bitmap represents one TID starting from TID 0, and a bit set to 1 indicates that there are buffered frames in the AP MLD that belong to the corresponding TID. The STA uses the TID-link mapping to determine which link to wake up to retrieve the buffered MPDUs (MAC Protocol Data Units). In this example, it is assumed that different TIDs are mapped to different links.

[0036] FIG. 6 shows a TIM bitmap 600 and a TID bitmap 602 in a TIM element. In the TIM bitmap 600, the TIM bits corresponding to one non-AP STA assigned AID 27 and five non-AP MLDs assigned AIDs 12, 28, 35, 57, 77 are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to the corresponding STA and MLD, respectively. For each non-AP MLD's TIM bit set to 1 in the TIM element, there is an 8-bit TID. In this case, the TID bitmap 602 includes five 8-bit TIDs for each of the five non-AP MLDs for which the AP MLD has one or more buffered frames to transmit. The 8-bit TIDs are used to determine which link(s) each non-AP MLD should wake up to get the buffered MPDUs from the AP MLD. However, in this example, it is not clear whether a TID indication is also required for legacy non-AP STAs with AID 27. However, without this TID indication, non-AP MLDs with AIDs greater than 27 cannot identify their correct TID indication.

[0037] Alternatively, the AP signals a single TID using 3 bits instead of the 8-bit TID bitmap 602. Figure 7 shows the TIM bitmap 700 and the TID 702 in the TIM element. The 3-bit TID is signaled to each STA / MLD with an AID corresponding to the TIM bit set to 1, and if frames belonging to multiple TIDs are buffered in the AP MLD for non-AP MLD, the signaled TID can be based on a criterion specific to a particular implementation. The AP delivers the MPDU belonging to the indicated TID on the link that the STA / MLD wakes up, and in the MPDU, an A-Control (TID control) field is carried in which the AP signals additional TIDs with BU for non-AP MLD. It should be noted that even if the legacy STA does not recognize the TID indication, the TID indication is also required for the legacy STA so that the non-AP MLD can find the correct TID indication.

[0038] As mentioned above, regardless of the method used to signal additional information about the buffered BUs (e.g., link mapping, link set indication with link recommendation, and TID indication as shown in Figures 3-7), an additional bitmap is required for each bit set to 1 in the TIM element in order for non-AP MLDs to correctly understand their position in the link / TID information set (including legacy STAs and non-MLD EHT STAs). Therefore, there is a need for a communication device and communication method that supports a multilink traffic indication map to solve the above-mentioned problems and reduce the overhead required to signal additional information about the buffered BUs in a WLAN network including MLD.

[0039] According to the present disclosure, two solutions are proposed. Specifically, a presence bitmap is carried in a beacon / TIM / FILS discovery / OPS frame to indicate whether corresponding link / TID / AC information related to a buffered BU for a non-AP STA / MLD exists in the link / TID / AC information set. The presence bitmap can still carry implicit information about the link even if the bit is set to 0.

[0040] Additionally, a "Starting AID" field is carried in the Beacon / TIM / FILS discovery / OPS frame to indicate the smallest AID (e.g., the AID of the first non-AP MLD) associated with the non-AP MLD for which the Link / TID / AC information set contains the Link / TID / AC information. To further reduce the overhead of the Link / TID / AC information set, different portions (e.g., the AID space) can be reserved for allocation of AIDs to legacy STAs / non-MLD Very High Throughput (EHT) STAs and for allocation of AIDs to non-AP MLDs.

[0041] FIG. 8 shows a schematic diagram illustrating an example configuration of a communication device 800 according to the present disclosure. The communication device 800 can be implemented as an AP and a STA and can be configured to support a multi-link traffic indication map according to the present disclosure. As shown in FIG. 8, the communication device 800 can include a circuit 814, at least one wireless transmitter 802, at least one wireless receiver 804, and at least one antenna 812 (only one antenna is depicted in FIG. 8 for illustrative purposes for simplicity). The circuit 814 can include at least one controller 806, which is used to perform, with the assistance of software and hardware, the tasks that the at least one controller 806 is designed to perform, including controlling communications with one or more other communication devices in a multiple-input multiple-output (MIMO) wireless network. The circuit 814 can further include at least one transmit signal generator 808 and at least one receive signal processor 810. The at least one controller 806 can control at least one transmit signal generator 808 to generate MAC frames (e.g., data frames, management frames, and action frames) to be transmitted via the at least one wireless transmitter 802, and can further control at least one receive signal processor 810 to process MAC frames (e.g., data frames, management frames, and action frames) received via the at least one wireless receiver 804 from one or more other communication devices. The at least one transmit signal generator 808 and the at least one receive signal processor 810 can be independent modules of the communication device 800 that communicate with the at least one controller 806 for the functions described above, as shown in FIG. 8. Alternatively, the at least one transmit signal generator 808 and the at least one receive signal processor 810 can be included in the at least one controller 806. It will be understood by those skilled in the art that the arrangement of these functional modules is flexible and may be changed according to actual needs and / or requirements.Data processing, storage, and other associated control devices may be provided on an appropriate circuit board and / or chipset. In various embodiments, in operation, at least one wireless transmitter 802, at least one wireless receiver 804, and at least one antenna 812 may be controlled by at least one controller 806.

[0042] The communication device 800, in operation, provides the functionality required for a multilink traffic indication map. For example, the communication device 800 may be an AP among a plurality of APs belonging to an AP MLD (each of the plurality of APs operates on a corresponding link of the AP MLD), and the circuit (e.g., at least one transmit signal generator 808 of the circuit 814), in operation, generates a frame including a traffic indication map (TIM) element and a presence bitmap. The TIM element includes a partial virtual bitmap (PVM) indicating the presence of one or more buffered units for one of the non-AP STAs or non-AP MLDs associated with the AP or AP MLD, and the presence bitmap indicates whether additional information related to one or more BUs is present in the frame intended for one of the non-AP STAs or non-AP MLDs. The wireless transmitter 802, in operation, may transmit the frame on the link.

[0043] For example, the communication device 800 may be a STA among a plurality of STAs belonging to a non-AP MLD associated with an AP MLD (each of the plurality of STAs operates on a corresponding link of the non-AP MLD), and the wireless receiver 804 receives a frame on the link in operation. The frame includes a traffic indication map (TIM) element and a presence bitmap, where the TIM element includes a partial virtual bitmap (PVM) indicating the presence of one or more buffered units for the non-AP MLD, and the presence bitmap indicates whether additional information related to one or more BUs is present in the frame intended for the non-AP MLD. The circuit (e.g., at least one receive signal processor 810 of the circuit 814) can process the frame in operation.

[0044] In one embodiment, the frame transmitted / received by the communication device 800 further includes a starting AID (association identifier) ​​indicating the smallest AID for which additional information related to one or more BUs is present in the frame. In yet another embodiment, a first part of the PVM of the TIM element is associated with AIDs assigned to legacy STAs and non-MLD EHT STAs, and a second part of the PVM of the TIM element is associated with AIDs assigned to non-AP MLDs, and the first and second parts of the TIM element do not overlap.

[0045] 9 shows a flowchart 900 illustrating a communication method for a multi-link traffic map according to various embodiments of the present disclosure. In step 902, a step of generating a frame including a traffic indication map (TIM) element and a presence bitmap is performed, where the TIM element includes a partial virtual bitmap (PVM) indicating the presence of one or more buffered units for one of non-AP STAs or non-AP MLDs associated with an AP or AP MLD, and the presence bitmap indicates whether additional information related to one or more BUs is present in the frame intended for one of non-AP STAs or non-AP MLDs. In step 904, a step of transmitting the frame on the link is performed.

[0046] 10 illustrates an exemplary beacon / TIM frame 1000. Although a beacon / TIM frame format is shown, it will be understood that the same format can be applied to a Fast Initial Link Setup (FILS) Discovery frame or an Operation (OPS) frame. The beacon / TIM frame 1000 conveys a TIM element 1002 that includes a partial virtual bitmap (PVM) 1008, a link / TID / AC information presence bitmap 1004, and a link / TID / AC information set 1006 that includes link / TID / AC information for each of the associated MLDs. The presence bitmap 1004 indicates whether corresponding link / TID / AC information associated with a buffered BU for a non-AP MLD is present in the presence bitmap 1004.

[0047] Link / TID / AC information presence bitmap 1004 contains one bit for every bit set to one in TIM element 1002, in the same order as PVB 1008. A bit in presence bitmap 1004 is set to one if a corresponding entry of link / TID / AC information is present in link / TID / AC information set 1006, and is set to zero otherwise.

[0048] The bit corresponding to the legacy STA is always set to 0. Meanwhile, the bit corresponding to the MLD is set to 1 if the link / TID / AC information for the MLD exists in the link / TID / AC information set 1006, for example, if the AP MLD buffers BUs for the non-AP MLD on other links, or if the AP MLD recommends the non-AP MLD to obtain BUs on other links, or if the AP MLD needs to signal BUs of TIDs that are mapped to other links. Otherwise, it is set to 0. For example, if the AP MLD is buffering BUs for a non-AP MLD on the same link (referred to herein as the "current link" but which may also be referred to as the "transmitting link") on which the TIM frame / beacon frame 1000 carrying the TIM element is transmitted, or if the AP MLD recommends the non-AP MLD to acquire BUs on the current link, or if all BUs for the non-AP MLD belong to a TID that is exclusively mapped to the current link, or for a single-link EHT STA or single-link non-AP MLD that listens to beacons on only one link, the bit is set to 0 on all links. Advantageously, the bit set to 0 still conveys implicit information about the current link, and the link / TID / AC information is only present for MLDs that need the information. Using the presence bitmap 1004 in the beacon frame / TIM frame 1000, the non-AP MLD is configured to check its corresponding bit in the presence bitmap 1004 if its corresponding bit in the PVB 1008 is set to 1, and if its bit in the presence bitmap 1004 is set to 1, further check the corresponding entry in the link / TID / AC information set 1006 to obtain further information about the BU associated with the link / TID / AC.

[0049] According to the present disclosure, the same AID is assigned to MLD across all links, but legacy is assigned a unique AID on each link, i.e., different legacy STAs may be assigned the same AID on different links. Advantageously, there is no restriction on how AIDs are assigned by AP MLD.

[0050] FIG. 11 illustrates an exemplary AID assignment and three exemplary TIM bitmaps 1100, 1110, 1120 transmitted by the AP-MLD on three links, respectively. MLDs 1, 2, 3 operating on all three links (Link 1, Link 2, Link 3) and single-link MLD 4 are assigned the same AIDs 12, 28, 57, 77 across the three links, respectively, and legacy STAs are assigned unique AIDs on their respective operational links. It is notable that the same AID 35 is assigned to different legacy STAs (Legacy 1 and Legacy 2) on Link 1 and Link 2, but no AID 35 is assigned on Link 3. Various embodiments of the present disclosure described below with reference to accompanying FIGS. 12-16 are based on the exemplary AID assignment used in the exemplary TIM bitmap 1100.

[0051] In one embodiment, the presence bitmap 1004 shown in FIG. 10 can be a link mapping bitmap (LMB), the link / TID / AC information set 1006 shown in FIG. 10 is an LMB set, and the presence bitmap indicates whether a corresponding LMB exists in the LMB set. The bit corresponding to a legacy STA is always set to 0. Meanwhile, the bit corresponding to an MLD is set to 0 if the BU is only available on the link on which the TIM frame / beacon frame carrying the TIM element is transmitted, e.g., due to TID-link mapping or because the MLD operates only on that link, and is set to 1 if the BU is also available on other links. The LMB presence bitmap contains one bit for every bit set to 1 in the TIM bitmap, in the same order as the TIM bitmap, and the LMB set contains one LMB for every bit set to 1 in the LMB presence bitmap, in the same order as the LMB presence bitmap. Advantageously, a bit set to 0 in the LMB presence bitmap indicates that the corresponding non-AP MLD only needs to acquire a BU on the current link, and no LMB is required in the LMB set, reducing the overhead of link / TID / AC information.

[0052] 12 illustrates an exemplary TIM bitmap 1200, an exemplary LMB presence bitmap 1202, and an exemplary LMB set 1204 in a TIM frame / beacon frame. In the TIM bitmap 1200, the TIM bits corresponding to AIDs 12, 28, 35, 57, and 77 assigned to MLD 1, MLD 2, Legacy 1, MLD 3, and Single-Link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to these STAs / MLDs. The LMB presence bitmap 1202 contains one bit for every bit set to 1 in the TIM bitmap 1200, in the same order as the TIM bitmap 1200, and thus the LMB presence bitmap 1202 has a total size of 5 bits.

[0053] In this example, the AP MLD transmitting the TIM frame / beacon frame operates on three links (Link 1, Link 2, Link 3), and the TIM frame / beacon frame transmitted on Link 1 (referred to herein as the current link) is shown. MLD 1 has only BUs of TIDs mapped to Link 1, while MLD 4 operates only on Link 1 in this example. Since the BUs of TIDs of MLD 1 and MLD 4 are mapped to the current link (Link 1), no additional information is needed for MLD 1 and MLD 4, and only LMBs for MLD 2 and MLD 3 are present or needed in the LMB set. The first and fifth bits of the LMB presence bitmap 1202 corresponding to MLD 1 and MLD 4 are set to 0, indicating that the BUs are available only on the current link (Link 1). Meanwhile, the second and fourth bits of the LMB presence bitmap 1202 corresponding to MLD 2 and MLD 3 are set to 1, indicating that the BUs of MLD 2 and MLD 3 are also available on other links (Link 2, Link 3). Legacy 1 is a legacy STA, and therefore the third bit of the LMB presence bitmap 1202 corresponding to Legacy 1 is always set to 0.

[0054] The LMB set 1204 contains one LMB for every bit set to 1 in the LMB presence bitmap 1202, in the same order as the LMB presence bitmap 1202. In this case, each LMB contains three bits corresponding to three different links (Link 1, Link 2, Link 3), so the LMB set 1204 has a total size of 6 bits. The bit of the LMB corresponding to the MLD is set to 1 to indicate that BUs are available on the corresponding link. In this case, the first LMB in the LMB set 1204 corresponding to MLD 2 has its second and third bits set to 1, indicating that BUs for MLD 2 are available on Link 2 and Link 3. In this example, the total overhead of the link / TID / AC information using the LMB presence bitmap 1202 (5 bits) and the LMB set 1204 (6 bits) is 11 bits.

[0055] In another embodiment, the presence bitmap 1004 can be a link recommendation (LR) presence bitmap, and the link / TID / AC information set 1006 is an LR bitmap set. For the default TID-link mapping where a TID is mapped to all valid links, the LR presence bitmap indicates whether a corresponding LR bitmap is present in the LR bitmap set. The bit corresponding to the MLD is set to 0 if the link on which the TIM frame / beacon frame carrying the TIM element is transmitted is recommended or if the AP MLD has no link recommendation, and is set to 1 if a link other than the current link is recommended.

[0056] The LR presence bitmap contains one bit for every bit set to 1 in the TIM bitmap, in the same order as the TIM bitmap, and the LR bitmap set contains one LR bitmap for every bit set to 1 in the LR presence bitmap, in the same order as the LR presence bitmap. Unlike LMB, the current link is excluded from the LR bitmap, because the current link can be promoted by setting the corresponding bit in the LR presence bitmap to 0. Advantageously, a bit set to 0 in the LR presence bitmap indicates that the corresponding non-AP MLD only needs to obtain BUs on the current link, and no LR bitmap is needed in the LR bitmap set, reducing the overhead of link / TID / AC information.

[0057] 13 illustrates an exemplary TIM bitmap 1300, an exemplary LR presence bitmap 1302, and an exemplary LR bitmap set 1304 in a TIM frame / beacon frame. In the TIM bitmap 1300, the TIM bits corresponding to AIDs 12, 28, 35, 57, and 77, which are assigned to MLD 1, MLD 2, Legacy 1, MLD 3, and Single Link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to these STAs / MLDs. The LR presence bitmap 1302 contains one bit for every bit set to 1 in the TIM bitmap 1300, in the same order as the TIM bitmap 1300, so that the LR presence bitmap 1302 has a total size of 5 bits.

[0058] In this example, the AP MLD transmitting the TIM frame / beacon frame operates on three links (Link 1, Link 2, Link 3) and the TIM frame / beacon frame is transmitted on Link 1 (referred to herein as the current link). MLD 1 only has BUs of TIDs mapped to Link 1, while MLD 4 only operates on Link 1. Since the BUs of TIDs of MLD 1 and MLD 4 are mapped to the current link (Link 1), no additional information is needed for MLD 1 and MLD 4 and only LR bitmaps for MLD 2 and MLD 3 are present or needed in the LR bitmap set 1304. The first and fifth bits of the LR presence bitmap 1302 corresponding to MLD 1 and MLD 4 are set to 0, indicating that the BUs are available only on the current link (Link 1), while the second and fourth bits of the LR presence bitmap 1302 corresponding to MLD 2 and MLD 3 are set to 1, indicating that the BUs of MLD 2 and MLD 3 are also available on other links (Link 2, Link 3). Legacy 1 is a legacy STA, and therefore the third bit of the LR presence bitmap 1302 corresponding to Legacy 1 is always set to 0.

[0059] The LR bitmap set 1304 contains one LR for every bit set to 1 in the LR presence bitmap 1202, in the same order as the LR presence bitmap 1202. In this case, each LR bitmap contains two bits corresponding to two different links (Link 2, Link 3) other than the current link (Link 1), and thus the LR bitmap set 1304 has a total size of 4 bits. When a bit in an LR bitmap corresponding to an MLD is set to 1, it indicates that a BU on a link other than the current link is recommended. In this case, the first LR bitmap in the LR bitmap set 1304 is associated with MLD 2 and has its first bit set to 1, indicating that Link 2 is recommended for MLD 2. The second LR bitmap in the LR bitmap set 1304 is associated with MLD 3 and has its second bit set to 1, indicating that Link 3 is recommended for MLD 3. The total overhead for link / TID / AC information using the LR presence bitmap 1302 (5 bits) and the LR set 1304 (4 bits) is 9 bits.

[0060] Besides being used in the default TID-link mapping, the LR presence bitmap and the LR bitmap set can also be used when different TIDs are mapped to different link sets, where a link set is one or more of the active links that are grouped into one link set. In such a case, the presence bitmap can be a link set presence bitmap, and the link / TID / AC information set is a link set bitmap set. The link set presence bitmap indicates whether a corresponding link set bitmap exists in the link set bitmap set. The bit corresponding to MLD is set to 0 if the link on which the TIM frame / beacon frame carrying the TIM element is transmitted is the only link in the link set and only this link set has a BU, and is set to 1 if the other link sets have a BU.

[0061] The linkset present bitmap contains one bit for every bit set to 1 in the TIM bitmap, in the same order as the TIM bitmap, and the linkset bitmap set contains one linkset bitmap for every bit set to 1 in the linkset present bitmap, in the same order as the linkset present bitmap. The LR bitmap set may further use bits set to 1 in the linkset bitmap set to indicate which links in the linkset have a BU present.

[0062] 14 illustrates an exemplary TIM bitmap 1400, an exemplary linkset present bitmap 1402, an exemplary linkset bitmap set 1404, and an exemplary LR bitmap set 1406. In the TIM bitmap 1400, the TIM bits corresponding to AIDs 12, 28, 35, 57, and 77, which are assigned to MLD 1, MLD 2, Legacy 1, MLD 3, and Single Link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to these STAs / MLDs. The linkset present bitmap 1402 contains one bit for every bit set to 1 in the TIM bitmap 1400, in the same order as the TIM bitmap 1400, so that the linkset present bitmap 1402 has a total size of 5 bits.

[0063] In this example, the AP MLD transmitting the TIM frame / beacon frame operates on three links (Link 1, Link 2, Link 3) and the TIM frame / beacon frame is transmitted on Link 3 (referred to herein as the current link or current link set). TIDs 0-3 are mapped to Link 1 and Link 2, and therefore Link 1 and Link 2 can be classified into a link set (Link Set 1), and TIDs 4-7 are mapped to Link 3, which is classified as another link set (Link Set 2). MLD 1 and MLD 2 only have BUs of TIDs mapped to Link Set 2 (i.e., Link 3), while MLD 4 operates only on Link 3. Since the BUs of TIDs of MLD 1, MLD 2, MLD 4 are mapped to the current link set (Link Set 2 or Link 3), no additional information is needed for MLD 1, MLD 2, and MLD 4, and only the link set bitmap for MLD 3 is present or needed in the link set bitmap set 1404. The first, second, and fifth bits of linkset presence bitmap 1402 corresponding to MLD 1, MLD 2, and MLD 4 are set to 0, indicating that the BU is available only on the current linkset, while the fourth bit of linkset presence bitmap 1402 corresponding to MLD 3 is set to 1, indicating that the BU is also available on the other linkset (linkset 1). Legacy 1 is a legacy STA, and therefore the third bit of linkset presence bitmap 1402 corresponding to Legacy 1 is always set to 0.

[0064] The linkset bitmap set 1404 contains one linkset bitmap for every bit set to 1 in the linkset present bitmap 1402, in the same order as the linkset present bitmap 1402. In this case, each linkset bitmap contains two bits corresponding to two different linksets (linkset 1, linkset 2), so the linkset bitmap set 1404 (which contains only one linkset bitmap) has a total size of 2 bits. When a bit in a linkset bitmap corresponding to an MLD is set to 1, it indicates that a BU is present in that linkset. In this case, the first bit in the linkset bitmap set associated with MLD 3 is set to 1, indicating that a BU for MLD 3 is present in linkset 1. The LR bitmap set 1406 contains one LR bitmap for every bit set to 1 in the linkset bitmap set 1404. The bit in the LR bitmap corresponding to a link in the linkset indicates whether a BU is present in that link in the linkset. In this case, the LR bitmap in LR bitmap set 1406 associated with MLD 3 has its second bit set to 1, indicating that a BU is present on link 2 of linkset 1. The total overhead for the link / TID / AC information using linkset presence bitmap 1402 (5 bits), linkset bitmap set 1404 (2 bits), and LR bitmap set 1406 (2 bits) is 9 bits.

[0065] In one embodiment, the presence bitmap 1004 shown in Fig. 10 can be a TID information presence bitmap, and the link / TID / AC information set 1006 is a TID information bitmap set, where the TID information presence bitmap indicates whether corresponding TID information exists in the TID information bitmap set. The bit corresponding to MLD is set to 0 if the buffered BU belongs only to the TID mapped to the link on which the TIM frame / beacon frame carrying the TIM element is transmitted, and is set to 1 if BUs of TIDs mapped to other links are also buffered.

[0066] The TID information present bitmap contains one bit for every bit set to 1 in the TIM bitmap, in the same order as the TIM bitmap, and the TID information bitmap set contains one TID information bitmap for every bit set to 1 in the TID information present bitmap, in the same order as the TID information present bitmap. Advantageously, if a bit in the TID information present bitmap is set to 0 for a non-AP MLD, that non-AP MLD only needs to acquire BUs on the current link and no TID information bitmap is needed in the TID information bitmap set, reducing the overhead of link / TID / AC information.

[0067] 15 illustrates an exemplary TIM bitmap 1500, TID information present bitmap 1502, and TID information bitmap set 1506 in a TIM frame / beacon frame. In TIM bitmap 1500, the TIM bits corresponding to AIDs 12, 28, 35, 57, and 77 assigned to MLD 1, MLD 2, Legacy 1, MLD 3, and Single-Link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to these STAs / MLDs. TID information present bitmap 1502 contains one bit for every bit set to 1 in TIM bitmap 1500, in the same order as the TIM bitmap, so that the TID information present bitmap has a total size of 5 bits.

[0068] In this example, the AP MLD transmitting the TIM frame / beacon frame operates on three links (Link 1, Link 2, Link 3), and the TIM frame / beacon frame is transmitted on Link 1 (referred to as the current link in this specification). MLD 1 has only BUs of TIDs mapped to Link 1, while MLD 4 operates only on Link 1. Since the BUs of TIDs of MLD 1 and MLD 4 are mapped to the current link, no additional information is needed for MLD 1 and MLD 4, and only TID information bitmaps for MLD 2 and MLD 3 are present or needed in the TID information bitmap set 1504. The first and fifth bits of the TID information presence bitmap 1502 corresponding to MLD 1 and MLD 4 are set to 0, indicating that the buffered BUs for MLD 1 and MLD 4 belong only to TIDs mapped to the current link (Link 1). In contrast, the second and fourth bits of the TID information present bitmap 1502 corresponding to MLD 2 and MLD 3 are set to 1, indicating that the respective BUs of TIDs mapped to other links (Link 2 and Link 3) are also buffered. Legacy 1 is a legacy STA, and therefore the third bit of the TID information present bitmap corresponding to Legacy 1 is always set to 0.

[0069] The TID information bitmap set 1504 includes one TID information bitmap for every bit set to 1 in the TID information presence bitmap 1502, in the same order as the TID information presence bitmap 1502. In this case, each TID information bitmap includes 8 bits corresponding to 8 TIDs (TIDs 0-7), and thus the TID information bitmap set 1504 has a total size of 16 bits. The bit of the TID information bitmap corresponding to the MLD is set to 1 if the BUs of the respective TIDs mapped to other links (Link 2, Link 3) are also buffered. In this case, the TID information bitmaps in the TID information bitmap set 1504 are associated with MLD 2 and MLD 3, and their second to seventh bits (corresponding to TIDs 1-6) are set to 1, indicating that the BUs of TIDs 1-6 mapped to other links are also buffered. The total overhead for link / TID / AC information in this case using TID information present bitmap 1502 (5 bits) and TID information bitmap set 1504 (16 bits) is 21 bits.

[0070] Alternatively, instead of the TID information bitmap (8 bits), a single TID (3 bits) may be signaled, similar to the method described in FIG. 7, but only for those bits of the MLDs (MLD 2 and MLD 3 in this case) that are set to 1 in the TID information present bitmap 1502.

[0071] Also, in one embodiment, the TID-link mapping is per Access Category (AC), i.e., two TIDs of an AC are always mapped to a link together, and never separately. In such an embodiment, the presence bitmap can be an AC information presence bitmap, the link / TID / AC information set is an AC information bitmap set, and the AC information presence bitmap indicates whether the corresponding AC information is present in the AC information bitmap set. The bit corresponding to an MLD is set to 0 if only BUs of TIDs of ACs mapped to the link on which the TIM frame / beacon frame carrying the TIM element is transmitted (referred to as the current link in this specification) are buffered, and is set to 1 if BUs of TIDs of ACs mapped to other links are also buffered. Advantageously, if the bit of the AC information presence bitmap for a non-AP MLD is set to 0, that non-AP MLD only needs to acquire BUs on the current link.

[0072] The AC information present bitmap contains one bit for every bit set to 1 in the TIM bitmap, in the same order as the TIM bitmap, and the AC information bitmap set contains one AC information bitmap for every bit set to 1 in the AC information present bitmap, in the same order as the AC information present bitmap. Advantageously, if a bit in the AC information present bitmap for a non-AP MLD is set to 0, that non-AP MLD only needs to acquire BUs on the current link, and no AC information bitmap is needed in the AC information bitmap set, reducing link / TID / AC information overhead.

[0073] 16 illustrates an exemplary TIM bitmap 1600, an exemplary AC information present bitmap 1602, and an exemplary AC information bitmap set 1604 in a TIM frame / beacon frame. In the TIM bitmap 1600, the TIM bits corresponding to AIDs 12, 28, 35, 57, and 77 assigned to MLD 1, MLD 2, Legacy 1, MLD 3, and Single-Link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to these STAs / MLDs. The AC information present bitmap 1602 includes one bit for every bit set to 1 in the TIM bitmap 1600, in the same order as the TIM bitmap 1600, so that the TID information present bitmap 1602 has a total size of 5 bits.

[0074] In this example, the AP MLD transmitting the TIM / Beacon frame operates on three links (Link 1, Link 2, Link 3) and the TIM / Beacon frame is transmitted on Link 1 (referred to as the current link herein). There are four ACs, namely AC_BK, AC_BE, AC_VI, and AC_VO. Two TIDs are mapped to each of the four ACs. An example of AC-TID mapping is shown in Table 1 below. The two TIDs of each AC are always mapped to a link. In this example, AC_VO and AC_VI are mapped to Link 1 and Link 2, and AC_BE and AC_BK are mapped to Link 3.

[0075] MLD 1 only has BUs of ACs mapped to link 1, while MLD 4 only operates on link 1. Since BUs of ACs of MLD 1 and MLD 4 are mapped to the current link, no additional information is needed for MLD 1 and MLD 4, and only AC information bitmaps for MLD 2 and MLD 3 are present or needed in AC information bitmap set 1604. The first and fifth bits of AC information presence bitmap 1602 corresponding to MLD 1 and MLD 4 are set to 0, indicating that only BUs of TIDs of ACs mapped to the current link (link 1) are buffered. Meanwhile, the second and fourth bits of AC information presence bitmap 1602 corresponding to MLD 2 and MLD 3 are set to 1, indicating that those BUs of ACs mapped to other links (link 2 and link 3) are also buffered. Legacy 1 is a legacy STA, and therefore the third bit of AC information presence bitmap 1602 corresponding to Legacy 1 is always set to 0. [Table 1]

[0076] The AC information bitmap set 1604 contains one AC information bitmap for every bit set to 1 in the AC information present bitmap 1602, in the same order as the AC information present bitmap 1602. In this case, each AC information bitmap contains 4 bits corresponding to the four ACs (AC_BK, AC_BE, AC_VI, AC_VO), and thus the AC information bitmap set 1604 has a total size of 8 bits. The total overhead of the link / TID / AC information using the AC information present bitmap 1602 (5 bits) and the AC information bitmap set 1604 (8 bits) in this case is 13 bits.

[0077] According to the present disclosure, different portions of the TIM bitmap (e.g., AID space) can be reserved for allocation of AIDs to legacy STAs / non-MLD very high throughput (EHT) STAs and for allocation of AIDs to non-AP MLDs, where the different portions do not overlap.

[0078] 17 shows an exemplary AID allocation and three exemplary TIM bitmaps 1700, 1710, 1720 transmitted from the AP MLD on three links, respectively. In this example, 255 consecutive AIDs (out of a maximum of 2007) are used by the AP MLD, with the first AID (0) being used to indicate group-addressed frames and not assigned to a STA. The next 30 AIDs (1-30) are reserved for legacy STAs and single-link EHT STAs, and the remaining AIDs (31-255) are used for non-AP MLD.

[0079] Each TIM bit is mapped to an AID. Thus, following the first TIM bit associated with AID 0, the next portion of the TIM bitmap (in this case associated with AIDs 1-30) is reserved for legacy and non-MLD EHT STAs (referred to herein as the non-MLD STA AID space), and the remaining portion of the TIM bitmap is used for non-AP MLD (referred to herein as the non-AP MLD AID space). Advantageously, such AID allocation can reduce the overhead of link / TID / AC information.

[0080] Thus, due to the AID assignment, the link / AID / AC information associated with the buffered BU is present in the link / AID / AC information set only for the non-AP MLD. The Starting AID field can be used to indicate the first non-AP MLD AID (e.g., the smallest AID) in the non-AP MLD AID space whose link / AID / AC information is included in the link / TID / AC information set. Various embodiments of the present disclosure described below with reference to accompanying Figures 19 and 21 are based on the exemplary AID assignment used in the exemplary TIM bitmap 1710.

[0081] 18 illustrates an exemplary Beacon / TIM frame 1800. Although a Beacon / TIM frame format is shown, it will be understood that the same format can be applied to a Fast Initial Link Setup (FILS) Discovery frame or an Operations (OPS) frame. The Beacon / TIM frame 1800 conveys a TIM element 1802 that contains a Partial Virtual Bitmap (PVM) 1808, a Starting AID field 1804, and a Link / TID / AC information set 1806 that contains the Link / TID / AC information for each of the associated MLDs.

[0082] 19 illustrates an exemplary TIM bitmap 1900 and LMB set 1904 in a beacon / TIM frame. In the TIM bitmap 1900, if the AP MLD has one or more buffered frames to send to non-AP STAs / MLDs on any of the links used, the TIM bit is set to 1. The TIM bits corresponding to AIDs 11, 12, 35, 57, 77, 255 assigned to Legacy 2, Single-Link EHT STAs, MLD 1, MLD 2, MLD 3, and Single-Link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to send to these STAs / MLDs.

[0083] The Starting AID field 1902 indicates the lowest AID assigned to the non-AP MLD that has the TIM bit set to 1 (i.e., link / TID / AC information present in the frame). In this case, the Starting AID is 35. The allocation of the non-AP MLD's AID space in the TIM bitmap and the Starting AID eliminates the need for a presence bitmap, thus reducing the overhead of link / TID / AC information.

[0084] A non-AP MLD can locate its corresponding link / TID / AC information in the link / TID / AC information set based on the starting AID in the Starting AID field 1902 and the TIM bitmap 1900. Specifically, a starting AID of 35 indicates that the first entry in the link / TID / AC information set is associated with the non-AP MLD assigned to AID 35 (MLD 1 in this case).

[0085] 20 illustrates another exemplary Beacon / TIM frame 2000. A Link / TID / AC Information Present Bitmap 2005 can be used together with a Starting AID field 2004 to further reduce the overhead of the Link / TID / AC information.

[0086] 21 illustrates an exemplary TIM bitmap 2100, an exemplary TID information present bitmap 2104, and an exemplary TID information bitmap set 2106 in a beacon / TIM frame. In the TIM bitmap 2100, the TIM bits corresponding to AIDs 11, 12, 35, 57, 77, 255 assigned to Legacy 2, Single Link EHT STA, MLD 1, MLD 2, MLD 3, and Single Link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to these STAs / MLDs. In this example, the TIM is transmitted on Link 2, and the Starting AID field 2102 is set to the beginning of the non-AP MLD AID space (AID 31). The TID information present bitmap contains one bit for every bit in the TIM bitmap that is set to 1, starting with the AID pointed to by the Starting AID field (i.e., 31). Through the allocation of non-AP MLD AID space in the TIM bitmap 2100 and the starting AID 2102, the TID information present bitmap 2104 for the non-MLD STA's AID space (AIDs 1-30) is omitted, thus reducing the link / TID / AC information overhead.

[0087] In this example, MLD 1 only has BUs for TIDs mapped to link 2, while MLD 4 only operates on link 1, and therefore no TID information for MLD 4 is included in link 2. No additional information of buffered BUs for MLD 1 and MLD 4 is needed, and only TID information bitmaps for MLD 2 and MLD 3 are present or needed in the TID information bitmap set 2106. The second and third bits of the TID information present bitmap 2104 corresponding to MLD 2 and MLD 3 are set to 1, indicating that those BUs for TIDs mapped to other links are also buffered.

[0088] The TID information bitmap set contains one TID information bitmap for every bit set to 1 in the TID information present bitmap 2104, in the same order as the TID information present bitmap 2104. In this case, a single TID (3 bits) is signaled for each of MLD 2 and MLD 3, and thus the TID information bitmap set 2106 has a total size of 6 bits. The 3-bit TIDs 101 and 111 signal that BUs of TID 5 and TID 7 are buffered for MLD 2 and MLD 3, respectively. If BUs of other TIDs exist, they are signaled in the A control field of the following data frame belonging to the indicated TID.

[0089] In one embodiment, for an AP that is a member of a multiple BSSID set (i.e., a virtual AP), bits 1-(2) of the TIM bitmap are nThe bits 0x10 ...

[0090] 22 shows an example TIM bitmap 2200 transmitted on a link from an AP MLD, and an example format of an AC information present bitmap 2202 and an AC information bitmap set 2204. In this example, 255 consecutive AIDs (out of a maximum of 2008) are used by the AP MLD, with the first four AIDs (0-3) used to indicate group-addressed frames corresponding to four virtual APs, the next 200 AIDs (4-203) reserved for non-AP MLDs operating on multiple links, and the remaining AIDs (204-255) used for legacy STAs and single-link EHT STAs.

[0091] Each TIM bit is mapped to an AID. Thus, the beginning portion 2211 of the TIM bitmap 2200 (in this case, the TIM bits associated with AIDs 0-3) is reserved for AP MLD (referred to herein as the AP MLD AID space). Following the AP MLD AID space 2211, the next portion 2212 of the TIM bitmap (in this case, the portion associated with AIDs 11-203) is reserved for non-AP MLD (referred to herein as the non-AP MLD AID space), and the remaining portion 2213 of the TIM bitmap is reserved for legacy STAs and non-MLD EHT STAs (referred to herein as the non-MLD STA AID space).

[0092] The non-AP MLD AID space 2212 starts immediately (additionally) after the AID space 2211 reserved for APs in the TIM bitmap 2200. Single-link MLDs (e.g., single-link MLD 4 in FIG. 22) can also be assigned AIDs from the non-MLD STA AID space, and thus the non-AP MLD AID space 2212 is reserved exclusively for non-AP MLDs operating on multiple links. Instead of a fixed AID space, it is also possible that the boundaries of the AID space are not clearly defined. For example, non-AP MLDs operating on multiple links are assigned AIDs consecutively starting from the first available AID (e.g., 4, 5, 6, ...), while legacy STAs and single-link EHT STAs are assigned AIDs consecutively starting from the last AID in the AP's AID space (e.g., 255, 254, 253, ...). Advantageously, since the AID space reserved for the AP (eg, the NonTxBSS ID) is known to all associated STAs, the starting AID is known and can be omitted in this scheme.

[0093] Returning to FIG. 22, with this AID assignment, the presence bitmap only needs bits for non-AP MLDs since link / AID / AC information related to buffered BUs is present for non-AP MLDs only, while legacy STAs and non-MLD EHT STAs are not included in the link / AID / AC information set. The TIM bits corresponding to AIDs 12, 28, 35, 56, 204, 227, 225 assigned to MLD 1, MLD 2, MLD 3, and single-link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to send to these STAs / MLDs. In this example, the TIM is sent on link 3. No AC information is included for MLD 4 since MLD 1 only has BUs with TIDs mapped to link 3, while MLD 4 only operates on link 1. No additional information of buffered BUs for MLD 1 and MLD 4 is needed; only AC information bitmaps for MLD 2 and MLD 3 are present or needed in the AC information bitmap set 2204. The second and third bits of the AC information presence bitmap 2202 corresponding to MLD 2 and MLD 3 are set to 1, indicating that those BUs of ACs mapped to other links are also buffered.

[0094] The AC information bitmap set 2204 contains one AC information bitmap for every bit set to 1 in the AC information present bitmap 2202, in the same order as the AC information present bitmap 2202. In this case, each AC information bitmap contains four bits corresponding to the four ACs (AC_BK, AC_BE, AC_VI, AC_VO), and thus the AC information bitmap set 2204 has a total size of 8 bits. The total overhead of the link / TID / AC information using the AC information present bitmap (3 bits) and the AC information bitmap set (8 bits) is 11 bits.

[0095] In yet another embodiment, even if there is no restriction on AID assignment, the overhead of link / TID / AC information can be reduced by excluding STAs with AIDs smaller than the starting AID, for example by using the Starting AID field to indicate the starting AID. The excluded STAs can be legacy STAs, non-MLD EHT STAs, and even MLDs where no link / TID / AC information exists.

[0096] FIG. 23 illustrates an example TIM bitmap 2300, an example TID information present bitmap 2304, and an example TID information bitmap set 2306 in a beacon / TIM frame. The TIM bits corresponding to AIDs 11, 12, 35, 57, 77, and 255 assigned to Legacy 2, Single Link EHT STA, MLD 1, Legacy 7, MLD 3, and Single Link MLD 4, respectively, are set to 1, indicating that the AP MLD has one or more buffered frames to transmit to these STAs / MLDs. In the absence of any restrictions on the assignment of AIDs, AIDs of legacy STAs (e.g., Legacy 7) and AIDs of non-AP MLDs may be mixed. The Starting AID field 2302 may indicate the AID of the first non-AP MLD whose link / TID / AC information is included in the link / TID / AC information set (i.e., the smallest AID associated with a non-AP MLD). In this case, the Starting AID field 2302 indicates 35 as the starting AID. This easily excludes Legacy 2 and single-link EHT STAs from the TID information bitmap set. Legacy and non-MLD EHT STAs are still included in the Link / TID / AC information set, but only those STAs with AIDs higher than the Starting AID (e.g., Legacy 7).

[0097] The TID information present bitmap 2304 contains one bit for every bit set to 1 in the TIM bitmap, in the same order as the TIM bitmap 2300, so that the TID information present bitmap 2304 has a total size of 4 bits. In this case, the first and third bits corresponding to MLD 1 and MLD 3 are set to 1 in the TID information present bitmap 2304. The TID information bitmap set 2306 contains one TID information bitmap (in this case a single TID of 3 bits) for every bit set to 1 in the TID information present bitmap 2304, in the same order as the TID information present bitmap 2304. In this case, the first and third bits corresponding to MLD 1 and MLD 3 are set to 1 in the TID information present bitmap, so that the TID information bitmap set 2306 has a size of 6 bits. The total overhead for link / TID / AC information in this case using TID information present bitmap 2304 (4 bits) and TID information bitmap set 2306 (6 bits) is 10 bits.

[0098] 24 illustrates an example format of a Multi-link TIM 2400. The Multi-link TIM 2400 can be a new element or a Multi-link element with the Type field set to "Multi-link TIM" defined to carry a presence bitmap and a Link / TID / AC information set. The Multi-link TIM element includes an Element field, a Length field, an Element ID Extension field, a Multi-link Control field containing a Type field (set to "Multi-link TIM") and a presence bitmap, a Common Info field, and a Link Info field.

[0099] The Presence Bitmap field of the Multi-link Control field further includes a Starting AID Present field and a Presence Bitmap Size Present field, which are used to indicate the presence of the Starting AID field and the Presence Bitmap Size field in the Common Info field. The Common Info field further includes a Link / TID / AC Information Type field, a Starting AID field, and a Presence Bitmap Size field. The Link Info field further includes a Link / TID / AC Information Presence Bitmap Present field, a Link / TID / AC Information Presence Bitmap field, and a Link / TID / AC Information Set field. The Link / TID / AC Information Type field indicates what kind of information is conveyed in the Link / TID / AC Information Set field, as shown in Table 2 below. The Presence Bitmap Size field indicates the size of the Link / TID / AC Information Presence Bitmap.

[0100] The Link / TID / AC Information Presence Bitmap field indicates whether there is further information about the buffered BUs in the Link / TID / AC information and is set for non-AP MLDs. The Link / TID / AC Information Set field conveys further information about the buffered BUs for each of the non-AP MLDs.

[0101] According to the present disclosure, assuming that different AID spaces are reserved for the allocation of AIDs to legacy STAs (11n, 11ac, 11ax STAs) and for the allocation of AIDs to EHT devices (non-MLD EHT non-AP STAs and non-AP MLD), a separate TIM element (e.g., existing baseline TIM element) can be used only to signal buffered BUs for legacy STAs, while a new Multi-link TIM bitmap is included in the Multi-link TIM element only to signal buffered BUs for EHT devices. The AIDs used to indicate group addresses BUs (e.g., AID 0, NonTxBSS ID, or AID space of AP MLD) are overlapped in both the TIM bitmap for legacy STAs and the Multi-link TIM bitmap for EHT devices. [Table 2]

[0102] 25 shows an example TIM bitmap 2500, an example multilink TIM bitmap 2510, an example AC information presence bitmap, and an example AC information bitmap set in a beacon / TIM frame. In this example, 1020 consecutive AIDs (out of a maximum of 2008) are used by the AP MLD. 510 consecutive AIDs (1-510) are reserved for legacy STAs, and the remaining AIDs (511-1020) are used for EHT devices. Thus, the TIM bitmap 2500 is dedicated to indicate buffered BUs for legacy devices (in this case Legacy 1 and Legacy 2, which are assigned to AIDs 34 and 76, respectively), and the multilink TIM bitmap 2510 is dedicated to indicate buffered BUs for EHT devices such as MLD 1, MLD 2, non-MLD EHT STA 1, MLD 3, and single-link MLD 4, which are assigned to AIDs 512, 528, 535, 557, and 577, respectively. The AID used to indicate group address BUs (AID 0 in this case) is duplicated in the multilink TIM bitmap, as shown by 2505.

[0103] Legacy STAs only need to decode the TIM bitmap 2500, while EHT STAs only need to decode the multilink TIM bitmap 2510. In the multilink bitmap, the bit immediately following the overlapping bit(s) 2505 used to indicate group / broadcast addressed frames corresponds to the first AID in the AID space reserved for EHT devices. To avoid overlapping bits in the TIM bitmap, different AID spaces can be reserved for allocation of AIDs to legacy STAs and for allocation of AIDs to EHT devices.

[0104] As a variation, all non-MLD STAs can be assigned AIDs from the AID space of legacy STAs and the baseline TIM can be used to indicate buffered BUs for non-MLD STAs, which refers to legacy STAs and EHT STAs that do not belong to MLD.

[0105] As a further variation, single-link MLDs can be assigned AIDs from the legacy STA AID space, so that the legacy STA AID space is reserved exclusively for not only legacy STAs but all EHT devices operating on a single link, and the buffered BUs for single-link MLDs can also be indicated using the baseline TIM. In this case, the multi-link TIM bitmap is used exclusively to indicate the buffered BUs for non-AP MLDs.

[0106] The AC information present bitmap 2502 contains one bit for every bit set to 1 in the multilink TIM bitmap 2510, in the same order as the multilink TIM bitmap 2510, so that the AC information present bitmap 2502 has a total size of 5 bits. The AC information bitmap set 2504 contains one AC information bitmap for every bit set to 1 in the AC information present bitmap 2502, in the same order as the AC information present bitmap 2502. Each AC information bitmap contains 4 bits corresponding to 4 ACs. In this case, the second and fourth bits corresponding to MLD 2 and MLD 3 are set to 1 in the AC information present bitmap 2502, so that the AC information bitmap set has a size of 8 bits. In this case, the total overhead of the link / TID / AC information using the separate TIM elements for the EHT device, i.e., the AC information present bitmap 2502 (5 bits) and the AC information bitmap set 2504 (8 bits), is 13 bits.

[0107] 26 illustrates an example format of a Multi-link TIM element 2600 that includes a Multi-link TIM bitmap. The Multi-link TIM 2600 includes an Element field, a Length field, an Element ID Extension field, a Multi-link Control field that includes a Type field set to "Multi-link TIM" and a Presence Bitmap field, a Common Info field, and a Link Info field.

[0108] The Presence Bitmap field of the Multi-link Control field further includes a Starting AID Present field, a Multi-link TIM Information Present field, and a Presence Bitmap Size Present field, which are used to indicate the presence of the Starting AID field, the Multi-link TIM Information field, and the Presence Bitmap Size field of the Common Info field. The Common Info field further includes a Link / TID / AC Information Type field, a Starting AID field, a Multi-link TIM Information field, and a Presence Bitmap Size field. The Link Info field further includes a Link / TID / AC Information Presence Bitmap Present field, a Link / TID / AC Information Presence Bitmap field, and a Link / TID / AC Information Set field. The Multi-Link TIM Information field further includes a Bitmap Control field, a Bitmap Length field, and a Multi-link TIM Bitmap field.The Bitmap Control field has the same function as the Bitmap Control field in the legacy TIM element described and illustrated in Figure 24. The Bitmap Length field indicates the length of the multi-link bitmap in octets. The Multi-Link TIM Bitmap field indicates the buffered BUs for EHT devices or non-AP MLD only. The Link / TID / AC Information Type field indicates what kind of information is conveyed in the Link / TID / AC Information Set field, similar to Table 2 above. The Link / TID / AC Information Presence Bitmap field indicates whether there is more information about the buffered BUs in the Link / TID / AC information and is set for non-AP MLD. The Link / TID / AC Information Set field conveys further information about the buffered BUs for each non-AP MLD.

[0109] FIG. 27 illustrates an exemplary configuration of a communication device 2700 and three communication units 2712, 2722, 2732 belonging to the communication device 2700. The communication device 2700 is implemented as an AP MLD, and each of the communication units 2712, 2722, 2732 belonging to the communication device 2700 can be implemented as an AP configured to support a multi-link traffic indication map according to various embodiments of the present disclosure. The communication device 2700 includes a multi-TIM element generator 2702 configured to perform multi-link traffic indication mapping according to the above-mentioned embodiments, such as using a Starting AID field to generate a Multi-link TIM element and a presence bitmap, where the Multi-link TIM element includes a partial virtual bitmap (PVM) indicating the presence of one or more buffered units for an external communication device / device associated with the communication device, and the presence bitmap indicates whether additional information (e.g., link / TID / AC information) related to one or more BUs for the associated external communication device / device is present.

[0110] The communication device 2700 comprises a storage module for storing its MLD MAC MLD address 2701. The communication device 2700 further comprises a MAC SAP 2740 used for communicating with the Internet layer and / or the DS. Each of the communication units 2712, 2722, 2732 belonging to the communication device provides links 2718, 2728, 2738 which are associated with and capable of transmitting to another external communication device / device and / or DS (e.g. transmitting a frame including a Multi-link TIM element and a presence bitmap using an Initiation AID related field related to the Initiation AID) or receiving another signal from another external communication device / device and / or DS. Each of the participating communication apparatuses 2712, 2722, 2732 includes a MAC layer 2714, 2724, 2734 and a PHY (physical) layer 2716, 2726, 2736, which connects to a radio transmitter, radio receiver, and antenna used to transmit / receive signals to / from another communication apparatus / device via a corresponding link 2718, 2728, 2738. In one embodiment, the MAC layer includes a storage module that stores its AP MAC address 2715, 2725, 2735, and an optional AP MAC SAP for direct communication with the Internet layer for traffic to / from legacy STAs.

[0111] FIG. 28 illustrates an exemplary configuration of a communication device 2800 and three communication units 2812, 2822, and 2832 belonging to the communication device 2800. The communication device 2800 is implemented as a non-AP MLD, and each of the communication units 2812, 2822, and 2832 belonging to the communication device 2800 can be implemented as a STA configured to correspond to a multi-link traffic indication map according to various embodiments of the present disclosure. The communication device 2800 further includes a multi-TIM element parser 2802 configured to perform multi-link traffic indication mapping according to the above-mentioned embodiments, such as receiving and processing a Multi-link TIM element and a presence bitmap using a Starting AID field, where the Multi-link TIM element includes a partial virtual bitmap (PVM) indicating the presence of one or more buffered units for the communication device 2700, and the presence bitmap indicates whether additional information (e.g., link / TID / AC information) related to one or more BUs for the communication device 2800 is present.

[0112] The communication device 2800 comprises a storage module for storing its MLD MAC MLD address 2801. The communication device 2800 further comprises a MAC SAP 2840 used for communicating with the Internet layer and / or DS. Each of the communication units 2812, 2822, 2832 belonging to the communication device provides a link 2818, 2828, 2838 which is associated with and can perform steps of receiving / transmitting other signals from another external communication unit / device and / or DS. Each of the communication units 2812, 2822, 2832 belonging to the communication device comprises a MAC layer 2814, 2824, 2834 and a PHY (physical) layer 2816, 2826, 2836 which connects with a radio transmitter, a radio receiver and an antenna used for transmitting / receiving signals to / from another communication unit / device via the corresponding link 2818, 2828, 2838. In one embodiment, the MAC layer includes a storage module that stores its STA MAC addresses 2815, 2825, 2835, and an optional STA MAC SAP for communicating directly with the Internet layer for traffic to and from legacy APs / STAs.

[0113] The present disclosure can be realized by software, hardware, or software cooperating with hardware. Each functional block used in the description of each embodiment above can be realized in part or in whole by an LSI (large scale integrated circuit) such as an integrated circuit, and each process described in each embodiment can be controlled in part or in whole by the same LSI or a combination of LSIs. The LSI may be formed as an individual chip, or a single chip may be formed to include some or all of the functional blocks. The LSI may include a data input / output unit coupled to it. The LSI referred to here may be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. However, the technology for implementing the integrated circuit is not limited to the LSI, and may be realized using a dedicated circuit, a general-purpose processor, or a special-purpose processor. Furthermore, a field programmable gate array (FPGA) that can be programmed after the manufacture of the LSI, or a reconfigurable processor that can change the connection and settings of the circuit cells arranged inside the LSI may be used. The present disclosure can be realized as digital processing or analog processing. If future integrated circuit technology replaces LSI due to advances in semiconductor technology and other derived technologies, it may be possible to integrate functional blocks using that future integrated circuit technology. Biotechnology can also be applied.

[0114] The present disclosure may be implemented by any type of apparatus, device, or system having communication capabilities, referred to as a communications device.

[0115] Some non-limiting examples of such communications devices include phones (e.g., cellular phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), gaming consoles, e-book readers, telemedicine equipment, vehicles providing communications capabilities (e.g., automobiles, airplanes, ships), and various combinations thereof.

[0116] The communications devices are not limited to being portable or mobile, but may also include any type of apparatus, device, or system that is non-portable or stationary, such as smart home devices (e.g., appliances, lights, smart meters, control panels), vending machines, and any other "things" in the Internet of Things (IoT) network.

[0117] Communications may include, for example, exchanging data through cellular systems, wireless LAN systems, satellite systems, and various combinations thereof.

[0118] The communications device may include devices such as controllers and sensors coupled to the communications apparatus to perform the communications functions described in this disclosure. For example, the communications device may include a controller or sensor that generates control or data signals used by the communications apparatus to perform the communications functions of the communications device.

[0119] The communications device may further include infrastructure facilities, such as base stations, access points, and any other apparatus, devices, or systems that communicate with or control apparatuses such as the apparatuses in the non-limiting examples above.

[0120] A non-limiting example of a station may be a station included in a first plurality of stations belonging to a multi-link station logical entity (i.e., MLD, etc.), where as part of the first plurality of stations belonging to the multi-link station logical entity, the stations of the first plurality of stations share a common Medium Access Control (MAC) data service interface to higher layers, where the common MAC data service interface is associated with a common MAC address or traffic identifier (TID).

[0121] It can therefore be seen that embodiments of the present disclosure provide communication devices and methods operating on multiple links to fully realize the throughput gains of multi-link communication, particularly in multi-link secure retransmission.

[0122] In the above detailed description of the present embodiment, an exemplary embodiment has been presented, but it should be understood that a vast number of variations exist. Furthermore, it should be understood that the exemplary embodiment is an example, and is not intended to limit the scope, applicability, operation, or configuration of the present disclosure in any way. Rather, the above detailed description provides those skilled in the art with a convenient guide for implementing the exemplary embodiment. It should be understood that various changes can be made in the function and organization of the steps and methods of operation described in the exemplary embodiment, and in the modules and structures of the devices described in the exemplary embodiment, without departing from the scope of the subject matter described in the appended claims.

Claims

1. A non-access point (AP) multi-link device (MLD) including a plurality of stations (STAs), a receiving unit for receiving a frame including a traffic indication map (TIM) element and a start associated identifier (AID) field, the TIM element including a partial virtual bitmap (PVM) indicating the presence or absence of one or more buffered units (BUs) for each of a plurality of non-AP MLDs including the non-AP MLD, and the start associated identifier field indicating a minimum AID for which a link information bitmap indicating the presence or absence of traffic for each link exists among the AIDs corresponding to the plurality of non-AP MLDs; a circuit for determining, based on the starting AID field and the link information bitmap, a link on which the one or more BUs for said circuit are present; Non-AP MLD with

2. The PVM includes a first portion associated with AIDs assigned to a plurality of legacy STAs and a second portion associated with AIDs assigned to the plurality of non-AP MLDs, and a starting position of the second portion is specified by a starting AID indicated by the starting AID field. The non-AP MLD of claim 1.

3. The frame is a beacon frame. The non-AP MLD of claim 1.

4. A PVM indicating the presence or absence of one or more BUs for each of a plurality of non-AP STAs belonging to each non-AP MLD is included in a TIM element different from the TIM element; The non-AP MLD of claim 1.

5. A communication method for a non-access point (AP) multi-link device (MLD) including a plurality of stations (STAs), comprising: receiving a frame including a Traffic Indication Map (TIM) element and a Start Associated Identifier (AID) field, the TIM element including a Partial Virtual Bitmap (PVM) indicating the presence or absence of one or more Buffered Units (BUs) for each of a plurality of non-AP MLDs including the non-AP MLD, and the Start AID field indicating a smallest AID among the AIDs corresponding to the plurality of non-AP MLDs for which a link information bitmap indicating the presence or absence of traffic for each link exists; determining, based on the starting AID field and the link information bitmap, a link on which the one or more BUs for itself exist; A communication method including:

6. The PVM includes a first portion associated with AIDs assigned to a plurality of legacy STAs and a second portion associated with AIDs assigned to the plurality of non-AP MLDs, and a starting position of the second portion is specified by a starting AID indicated by the starting AID field. The communication method according to claim 5.

7. The frame is a beacon frame. The communication method according to claim 5.

8. A PVM indicating the presence or absence of one or more BUs for each of a plurality of non-AP STAs belonging to each non-AP MLD is included in a TIM element different from the TIM element; The communication method according to claim 5.

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