Enhancing reliability through multi-link operation using repeat transmissions

Abstract

A method for redundant transmission on a first link and a second link includes receiving a first MAC service data unit (MSDU) via a service access point (SAP) on an upper MAC sublayer of a first multi-link device; forwarding the first copy of the first MSDU to a first station STA on a lower MAC sublayer of the first multi-link device; and forwarding a second copy of the first MSDU to a second site on a lower MAC sublayer of the first multi-link device; creating, by the first site, a first header of a first MAC protocol data unit (MPDU) having a MAC address of the first site, the first MPDU comprising a first copy; and creating, by the second site, a second header of a second MPDU having the MAC address of the second site, the second MPDU including the second copy.

Description

Technical Field

[0001] Wi-Fi is a family of wireless network protocols based on the IEEE 802.11 series of standards. It is commonly used for devices to network on a local area network and access the Internet, allowing nearby digital devices to exchange data via radio waves. Background Technology

[0002] In industrial plants, such as production facilities, deterministic wireless communication is required to guarantee worst-case latency and jitter and provide high reliability. Wi-Fi provides the technological foundation for deterministic transmission, but suffers from major problems such as nondeterministic channel access by devices and interference during ongoing transmissions. A solution to the channel access problem is proposed in European patent application EP23160772.2, which extends MU EDCA (Multi-User (MU) Enhanced Distributed Channel Access (EDCA)) to allow access points (APs) to access channels with an upper limit on latency (e.g., 55 μs). Furthermore, wireless communication is susceptible to interference from outside the Basic Service Set (BSS). This is caused by other wireless local area networks (WLANs) or alternative wireless access technologies (such as 5G, Bluetooth, or similar technologies) operating in the same frequency band. Summary of the Invention

[0003] This disclosure aims to mitigate the effects of interference, specifically for 802.11be Wi-Fi networks, i.e., those using Multi-Link Operation (MLO).

[0004] According to a first aspect, a method for redundant transmission on a first link and a second link is proposed. The method includes: receiving a first MAC Service Data Unit (MSDU) via a service access point on the upper MAC sublayer of a first multi-link device. The method further includes: forwarding a first copy of the first MSDU to a first station on the lower MAC sublayer of the first multi-link device, and forwarding a second copy of the first MSDU to a second station on the lower MAC sublayer of the first multi-link device. The method further includes: creating a first header for a first MAC Protocol Data Unit (MPDU) having the MAC address of the first station on the lower MAC sublayer, the first MPDU including the first copy; and creating a second header for a second MPDU having the MAC address of the second station, the second MPDU including the second copy.

[0005] According to a second aspect, a method for redundant reception on a first wireless link and a second wireless link is proposed. The method includes: receiving a first MPDU, preferably via the first link, from a third station on the lower MAC sublayer of the second multi-link device, having a MAC address with a first MLD and including a first copy of the first MSDU; and receiving a second MPDU, preferably via the second link, from a fourth station on the lower MAC sublayer of the second multi-link device, having a MAC address with a second MLD and including a second copy of the first MSDU.

[0006] According to the third aspect, a first multi-link device is proposed, preferably comprising a processor and a memory, operable to perform the method steps of the first aspect.

[0007] According to the fourth aspect, a second multi-link device is proposed, preferably comprising a processor and a memory, operable to perform the method steps of the second aspect.

[0008] According to the fifth aspect, a system for redundant transmission on a first link and a second link between a first multi-link device according to the third aspect and a second multi-link device according to the fourth aspect is proposed.

[0009] According to the sixth aspect, a computer program comprising program code is proposed, which, when executed, performs the steps according to the first and / or second aspects.

[0010] Therefore, a replication mechanism is proposed that transmits multiple copies (i.e., replicas) of the same data unit on different links via a transmission multi-link device (MLD), and / or eliminates the replicas at the receiving MLD. For example, if one of two or more independent links encounters interference during transmission and one or more data units (i.e., frames) are lost on that link, the second link may still successfully transmit the replicated data unit. The proposed multi-link operation replication and / or elimination mechanism increases the probability of successful transmission, for example, assuming non-overlapping spectrum resources, and thus increases the reliability of critical transmissions, such as in Wi-Fi 7 networks. Attached Figure Description

[0011] Figure 1 The illustration shows the first multilink device and the second multilink device in multilink operation.

[0012] Figure 2 A diagram illustrating the MAC architecture of a multi-link device is shown.

[0013] Figure 3 The diagram shows the Physical Layer Packet Data Unit (PPDU), the MAC Layer Packet Data Unit (MPDU), and the MAC Layer Service Data Unit (MSDU).

[0014] Figure 4 An illustration of an exemplary multi-link device and its associated sites is shown.

[0015] Figure 5 A diagram illustrating redundant transmission of repeated MAC packet data units in a multi-link device is shown.

[0016] Figure 6 A diagram illustrating the reception of duplicate MAC packet data units by a multi-link device is shown.

[0017] Figure 7 The diagram illustrates two multi-link devices that apply MAC packet data unit replication and elimination on two links and non-redundancy on a single link.

[0018] Figure 8 A diagram of the management frame is shown.

[0019] Figures 9 to 26 Exemplary method steps according to various implementations are shown. Detailed Implementation

[0020] To facilitate the continued evolution of Wi-Fi networks, the next-generation IEEE 802.11 Wireless Local Area Network (WLAN) technology has been named Extremely High Throughput (EHT). It is currently being developed by the IEEE 802.11be Task Force (TGbe) and is expected to be adopted by the Wi-Fi Alliance as Wi-Fi 7. EHT focuses on achieving a significant increase in peak throughput of up to 30 Gbps, three times that of Wi-Fi 6, while simultaneously reducing latency.

[0021] Multilink Operation (MLO) is a mandatory feature of IEEE 802.11be devices; see Appendix B.4.3 of IEEE 802.11be D3.1. MLO is planned for IEEE 802.11be Version 1. The first devices supporting IEEE 802.11be will also be available at that time.

[0022] MLO allows a multi-link device (MLD) to create up to 16 links, which can be used as follows: Figure 1 The MLD is an independently coordinated device with multiple PHY interfaces that share the same logical link control LLC interface. A station STA is a logical entity that is a separate addressable instance of the Media Access Control (MAC) and Physical Layer (PHY) interfaces for the wireless medium.

[0023] IEEE 802.11be D3.1 defines standardized modifications to the IEEE Std 802.11 physical layer (PHY) and media access control layer (MAC) that enable at least one operating mode to support a maximum throughput of at least 30 Gbit / s measured at the MAC data service access point (SAP) with carrier frequencies between 1 GHz and 7.250 GHz, while ensuring backward compatibility and coexistence with legacy IEEE Std 802.11-compatible devices operating in the 2.4 GHz, 5 GHz, and 6 GHz bands. This amendment defines at least one operating mode that improves worst-case latency and jitter.

[0024] Typically, frame duplication and elimination improve the reliability of packet transmission by sending packet copies via disjoint links and eliminating packet copies at the receiving end. Notable examples of such duplication include IEEE 802.1CB Frame Duplication and Elimination (ERE), the (Industrial) Parallel Redundancy Protocol (i) PRP, broadcast frames in IEEE 802.11 mesh networks, and 3GPP PDCP, TS138 323-V16.2.0-5G. The current version of the standard IEEE 802.11be draft 3.1, available since March 2023, and examples of the prior art, do not provide specifications for packet duplication using multilink operation in 802.11be-compliant networks. More specifically, there is a lack of frame duplication mechanisms at the transmit MLD, a lack of frame identification for duplicated frames, and a lack of duplication elimination mechanisms at the receive MLD. Therefore, this paper proposes an extension to the IEEE 802.11be multilink operation mechanism that enables frame duplication. In the OSI model of computer networking, a frame is a protocol data unit at the data link layer. The data link layer is divided into two sublayers: Logical Link Control LLC and Media Access Control MAC.

[0025] Multilink Operation (MLO) is the simultaneous use of multiple radio links on different frequency channels / bands by a multilink device (such as an access point (AP), a client, or both). It is a MAC layer solution for the concurrent use of multiple links, and thus exposes a single MAC Service Access Point (SAP) to the upper sublayer of the data link layer (i.e., the Logical Link Control (LLC) layer). Therefore, the MAC SAP (function) provides one or more services to the LLC sublayer.

[0026] Each link in an MLD is treated as a regular single-link site STA, and the MLD is considered a device attached to more than one STA. A site STA can be an access point (AP) or a non-access point (non-AP) STA, providing link-specific lower-layer Media Access Control (MAC) and Physical Layer (PHY) services within the MLD. Therefore, based on the type of attached STAs, the MLD can be further classified into two types: First, AP MLD: Each of the attached STAs is an AP. Second, Non-AP MLD: Each of the attached STAs is a non-AP client STA.

[0027] To support multi-link operation (MLO), for example in IEEE 802.11be devices, the architecture has been modified to logically separate the MAC layer into two sub-layers, referred to as the upper MAC layer and the lower MAC layer, as follows: Figure 2 As shown. The upper MAC sublayer provides functionality common to all links, while the lower MAC sublayer is responsible for functionality bound to a specific link.

[0028] To allow multi-link devices (MLDs) to use multiple radios simultaneously, the IEEE 802.11be standard requires MLDs to support both individual MAC layer functionality for each interface (“lower-layer MAC”) and MAC layer functionality shared by all their interfaces (“upper-layer MAC”). Upper-layer MAC functionality includes, for example: - Authentication and Association - Select the MAC sublayer under MLD for transmission - Combine the reception of packets from two or more links - Coordination of EDCA parameter distribution and management on the MAC sublayer under the MLD of the link.

[0029] Lower-level MAC functionality includes, for example: - Link-specific control information exchange, such as RTS / CTS or ACKs - Power saving status and mode Some of the functionalities described above require joint processing between the upper and lower MAC layers. For successful transmission and / or reception of duplicate frames, the upper MAC layer primarily needs to integrate additional features.

[0030] Each associated STA of the MLD includes a PHY and a lower-level MAC component. On a set of associated STAs, the MLD has an upper-level MAC component that aggregates its set of associated STAs and provides a single MAC SAP to the LLC.

[0031] Go to Figure 3This illustrates the encapsulation of a MAC Service Data Unit (MSDU) into a MAC Packet Data Unit (MPDU) and an MPDU into a Physical Packet Data Unit (PPDU). The MSDU is a service data unit received from the Logical Link Control (LLC) sublayer, located above the MAC layer in the protocol stack. The LLC and MAC sublayers are collectively referred to as the Data Link Layer (DLL).

[0032] Now, when the LLC sublayer sends the MSDU to the MAC sublayer, MAC header information is added to the MSDU for identification. The MSDU is then encapsulated within a MAC Protocol Data Unit (MPDU). The MSDU can be considered the payload of the MPDU. The MSDU may contain IP packets and additional LLC data. Therefore, the payload of the MPDU can include layer 3 through 7 information referred to as the MSDU. Typically, the MPDU is also referred to as a frame or an 802.11 frame. The MPDU is a frame passed from the MAC layer to the PHY layer. In any case, the terms "frame" and "MPDU" are used interchangeably in this document.

[0033] MPDU can include the following three basic components: MAC header, frame body (including payload, i.e. MSDU, and frame check sequence or frame correction sequence FCS).

[0034] On the physical layer PHY, the MPDU becomes the Physical Layer Service Data Unit (PSDU). The Physical Layer Protocol Data Unit (PPDU) contains a preamble and one or more data fields. The preamble field contains transport vector format information. The data fields contain the PPDU payload, such as, among other things, higher-layer headers, such as Media Access Control (MAC) fields and Cyclic Redundancy Check (CRC) fields. The transport vector format and PPDU structure have varied between versions of 802.11.

[0035] Figure 4 An example of an AP MLD with two subordinate APs communicating on Link 1 and Link 2 is shown.

[0036] MLO defines a set of procedures that allow communication on multiple links between MLDs. The MLD manages such communication on multiple links. Communication on links using different frequency bands or channels can occur simultaneously or asynchronously, depending on the capabilities of both the AP MLD and the non-AP MLD.

[0037] The MLO procedure allows a pair of MLDs to discover, synchronize, (de-)authenticate, (re)associate, unassociate, and manage links and other resources on any public frequency band or channel supported by both MLDs.

[0038] Each MLD has a single MAC-SAP. Each AP attached to an AP MLD has a different MAC address than any other AP attached to an AP MLD, and each non-AP STA attached to a non-AP MLD has a different MAC address than any other non-AP STA attached to a non-AP MLD. The MLD MAC address of an MLD may be the same as the MAC address of one (attached) STA, or it may be different from the MAC address of any (attached) STA.

[0039] Figure 4 The diagram illustrates an AP MLD with MLD MAC address M and two associated APs (AP1 with MAC address w and AP2 with MAC address x) forming a MAC sublayer under the MLD. The AP MLD is associated with a non-AP MLD with MLD MAC address P, and the diagram also shows two associated STAs (STA1 with MAC address y and STA2 with MAC address z) forming a MAC sublayer under the MLD. Link 1 is established between AP1 and STA1, and link 2 is established between AP2 and STA2. Typically, the MAC address of the MLD is different from the MAC addresses of the STAs associated with it (e.g., M, P, w, x, y, and z have different values). However, this architecture supports an implementation where M can be equal to w or x, and P can be equal to y or z.

[0040] For simplicity, Figure 4 This describes a scenario with two links, whereas typically, an MLD can support more than two links. The MAC-SAP of an AP MLD can be identified by the same AP MLD MAC address.

[0041] The MAC sublayer is further divided into the MLD upper MAC sublayer and the MLD lower MAC sublayer. The MLD upper MAC sublayer performs functionality common to all links, while the MLD lower MAC sublayer (shared with APs or non-AP STAs attached to the MLD) performs link-specific functionality. Some functionalities require joint processing by both the MLD upper and lower MAC sublayers. The APMLD always operates in conjunction with one or more attached APs, one AP per link. The MLD lower MAC sublayer components implement link-specific functions that are independent of the lower-level MAC operations in other attached APs. The use of these MLD lower-level MAC functions is shared by the APMLD upper MAC sublayer and the upper MAC sublayers of the attached APs. For example, Figure 4 MLD 1 in the context can be a transmission MLD and Figure 4 The MLD in the MLD can be a receiving MLD or a second MLD, used for redundant transmission and / or redundant reception on the first and second links.

[0042] The illustration of frame copying in the first MLD is shown in Figure 5 As shown in the diagram. This MLD includes a frame replication mechanism on the transmitting MLD (MLD1) and a copy elimination mechanism on the receiving MLD (MLD2) as needed, such as... Figure 6 As shown.

[0043] Therefore, it is proposed to repeat frames on two or more separate links of a single MLD. Furthermore, it is proposed to mark duplicate frames based on the sequence number FSID added to the frame header, i.e., using the same sequence number for duplicate frames on different lower-layer MACs, and / or to filter received frames and remove all copies except the first received frame.

[0044] On the upper-layer MAC, the MLD MLD1 can include the following functionalities, for example, implemented by a path management entity. An instance is required on the upper-layer MAC to trigger link establishment and / or teardown of links using frame replication. The MAC SAP provides an interface for the upper-layer MAC to configure and / or manage the lower-layer MAC of the MLD attached to the STA. A mapping mechanism is proposed that maps services (i.e., one or more MSDUs) to individual links. For example, priority-based / service category mapping can be used. Priority-based / service category mapping can include, for example, mapping service identifiers (TIDs) to multiple links according to IEEE 802.11be D3.1. Alternatively, flow-based mapping can be used. Flow-based mapping can include one or more management frame extensions for MLO-based frame replication. Such management frame extensions can include new multi-link element types, such as "replicated multi-link element" for flow-based or TID-based replicated link setups.

[0045] A Traffic Identifier (TID) is an identifier used to classify frames. When the MLD receives an 802.11 frame with a TID, for example, set for audio, it is given higher priority than data frames intended for best-effort purposes. Therefore, based on priority, the proposed replication mechanism for redundant transmission can be used. The Traffic Identifier (TID) can be any of the identifiers used by higher-layer entities in the MAC data service to distinguish MAC Service Data Units (MSDUs) from MAC entities supporting Quality of Service (QoS). There are 16 possible TID values; eight identify the Traffic Category (TC), and another eight identify the Parameterized Traffic Flow (TS). TIDs are assigned to MSDUs in the layer above the MAC layer. By default, MSDU transmission is based on best-effort. However, QoS facilities use the Traffic Identifier (TID) to specify differentiated services based on each MSDU.

[0046] A stream can be understood as a flow of one or more data packets (such as MPDUs) and can be identified by a stream ID (i.e., a stream identifier). Therefore, based on a specific stream ID, the proposed replication mechanism for redundant transmission can be used.

[0047] On the upper-layer MAC, the MLD can include functionality such as, implemented by a tagging entity, for tagging frames based on the Frame Sequence ID (FSID). The FSID can be stored in the Copy List (DLO) on the upper-layer MAC of the MLD1. Since current solutions (e.g., solutions defined for mesh networks, see section 9.2.4.4.1, Sequence Control Field Structure, in IEEE 802.11-2020, which defines the sequence number of mesh data frames as part of the QoS control subfield) cannot be applied to MLO frame replication because the MAC addresses of the replicated frames (i.e., the associated STA / AP of the MLD device) are different, and therefore the sequence number of the replicated frames varies across links, an extension to the existing header field formats H1 and H2 is proposed to support the identification of replicated packets. This newly proposed header field (one or more) can be, for example, an additional field (part of) the QoS control subfield of the header (format) H1 or H2 (e.g., the header of a data frame). For example, the following header field information can be used for frame identification: Link ID, which is the identifier of the link in the MLO setting; Stream ID, which is the identifier of the stream transmitted on two or more links (if stream-based link mapping is used); and / or Frame Sequence ID, which is the identifier of duplicate frames (e.g., frames belonging to a stream or TID).

[0048] MAC sublayer entities can determine the user priority of an MSDU based on the TID value provided along with those MSDUs. Therefore, the (upper-layer) MAC attempts to deliver the MSDU belonging to that TID according to its configuration for that TID. When QoS-enabled STAs / APs transmit data frames, they include a QoS control field in the WiFi header, which includes the TID (Service Identifier) ​​field. This field contains 3 bits called the user priority (or UP) value, and it determines the priority of the WiFi frame during airborne transmission. Since WiFi has four different service classes, two UP values ​​are mapped to each access class. Note that the UP value 0 maps to Best-effort (BE) so that packets without QoS tags are processed with best-effort priority.

[0049] The main business is categorized into four different access types (voice, video, best-effort & background).

[0050] At the upper-layer MAC, the MLD can include a frame-based replication mechanism. For this purpose, the upper-layer MAC can forward copies of the MSDU (i.e., the links corresponding to the transmission of copies) to lower-layer MACs configured for frame replication. The frame sequence ID can then be incremented by the upper-layer MAC for subsequent frames to be replicated. The copies of the MSDU can then be encapsulated at the lower-layer MAC by stations STA1 and STA2. For this purpose, the MAC address of the first station STA1 can be inserted into the header (field) H1 of the first MPDU (MPDU1) including the first copy. Furthermore, the MAC address of the second station STA2 can be inserted into the header (field) H2 of the second MPDU (MPDU2) including the second copy.

[0051] Then, the duplicate frames MPDU1 and MPDU2 are forwarded from the lower-layer MAC stations STA and STA2 to the corresponding physical layer PHY for transmission of the corresponding link. For this purpose, MPDU1 is encapsulated in PPDU1 and MPDU2 is encapsulated in PPDU2.

[0052] At the upper-layer MAC, the MLD can include synchronous channel access across multiple links. For this purpose, different channel access strategies can be used for different links of the MLD. Distributed channel access makes synchronous transmission on different links less likely, i.e., each link manages its own EDCA queue, as both links need to compete for their respective channels before synchronous transmission can begin. Therefore, in frame replication scenarios, channel access can be coordinated using, for example, one of the following methods. For instance, the replica can be synchronously transmitted by waiting for all links (on which the replica should be transmitted) to access the channel individually. Alternatively and / or alternatively, the solution for MU EDCA proposed in European patent application EP23160772.2 can be used to guarantee channel access for the MLD on individual links, for example, by making OFDMA transmission only used on the link (on which the replica should be transmitted). Therefore, it may be necessary to synchronize channel access between different links, i.e., the lower-layer MAC can be synchronized via the upper-layer MAC. In any case, the replica can be transmitted asynchronously using an independent EDCA queue on each link.

[0053] The synchronous transmission scheduling of one or more lower-layer MACs can be managed or controlled by the upper-layer MAC. Such management or control may include setting a protection time for forwarding or waiting for all STAs to access the common / successful channel, with the upper-layer MAC providing the scheduling and the lower-layer MAC having guaranteed access time.

[0054] Figure 6A schematic diagram is shown of a second multi-link device, MLD2, receiving duplicate MAC packet data units, i.e., the receive MLD. Replica elimination may be required at the receive MLD. The receive MLD may include an upper-layer MAC and / or a lower-layer MAC for performing the following functions: The upper-layer MAC and / or lower-layer MAC of the receive MLD can be used to identify frames, for example, via frame ID, and / or to eliminate replicas. For example, the frame first received by the lower-layer MAC (which can be identified by the frame sequence ID FSID) will be forwarded to the upper-layer MAC sublayer. This may occur when there is no corresponding FSID in the replica list DL1 of the receive MLD MLD2.

[0055] The upper-layer MAC can manage a replica list DL3, which contains all FSIDs that have been received and / or processed by the receiving MLD. Replica lists DL1, DL2, and DL3 can be efficient shared memory between the upper-layer MAC and lower-layer MAC, for example, the receiving MLD. For instance, information about the received frame can be available in replica lists DL1, DL2, and DL3 as long as the latency requirement of the corresponding MPDU or associated stream is not exceeded. Therefore, the frame's transmission timestamp and / or the frame's latency requirement can be stored in replica lists DL1, DL2, and DL3 (along with the frame's FSID).

[0056] The following options are proposed for detecting replicas at the receiving MLD (MLD2). In the first option, the lower-layer MAC can perform a lookup in the replica list DL1 and, if the lookup is successful (i.e., the FSID of the received frame is found in the replica list DL1), discard or drop the frame. However, replicas received simultaneously at different lower-layer MACs can be forwarded to the upper-layer MAC and eventually to a higher layer.

[0057] In the second option, replicas can be detected at the upper-layer MAC. In this case, one or more received frames (including one or more replicas) can be forwarded from one or more lower-layer MACs to the upper-layer MAC of the receiving MLD. The upper-layer MAC can then perform a lookup and / or removal of one or more frames already in the replica list DL3. To do this, a comparison can be performed between the FSID of the received frame and one or more FSIDs in the replica list DL3.

[0058] A third option can be used to address potential bottlenecks at the upper MAC layer, such as when all replicas must be processed there. In this third option, the upper and lower MAC layers can interact when detecting and / or discarding one or more replicas. To do this, a first lookup can be performed at the lower MAC layer in replica lists DL1 and DL2, for example, to discard one or more replicas. A second lookup can be performed at the upper MAC layer in replica list DL3, where replicas that were not detected at the lower MAC layer are detected and / or discarded.

[0059] Go to Figure 7 An exemplary implementation is shown for repeated transmission and / or repeated reception between a first MLD MLDA and a second MLD MLDB.

[0060] Assume that the first MLD MLDA and the second MLD MLDB are configured for frame replication, and thus an MLO with redundant transmission and / or redundant reception is successfully established. One or more frames with a first TID (i.e., TID 7) will be replicated on links 1 and 2, while frames with another TID (i.e., TID 5) will be transmitted on a single link (i.e., link n). Furthermore, assume that the TID-to-link mapping has been established. The frames will then be mapped or forwarded to the corresponding STAs, STA1, STA2, STAn, for transmission on the corresponding links. For example, the TID-to-link mapping can be established by negotiating (a single) TID to multiple links, for example, according to IEEE 802.11be D3.1.

[0061] Combination Figure 7The transmission of the replicated frame is described further. At the upper MAC sublayer of the MLD MLDA, the frame for replication (with TID 7) is received by the MAC-SAP. The frame for replication (with TID 7) is marked with a unique frame ID 01, also known as the FSID. The frame for replication (i.e., the frame with TID 7 and frame ID 01) is forwarded to multiple lower-layer MACs and thus replicated. Channel access can be synchronized between link 1 and link 2 to initiate the synchronous transmission of the replica (of the frame with TID 7 and frame ID 01), and the replicated frame is transmitted on both links. The reception of the replicated frame by the receiving MLD (MLDB) will be described below. In this implementation, only the lower-layer MAC performs deduplication checking and / or deduplication dropping; however, another option as described herein can also be used. The frame with frame ID 01 is received by STA1 of the second MLD MLDB. After the second MLD MLDB site STA3 performs a lookup for frame ID 01 in the replica list (e.g., at the lower MAC layer) and does not find FSID frame ID 01 in the list, the frame with FSID frame ID 01 is added to the replica list and forwarded to the upper MAC sublayer, and finally forwarded to the MAC-SAP endpoint of the second MLD MLDB.

[0062] When the replica elimination mechanism is performed at the upper MAC layer of the second MLD MLDB, the upper MAC layer of the second MLD adds FSID 01 to the replica list of the fourth site (located at the lower MAC layer of the fourth site STA 4).

[0063] The fourth station STA4 of the second MLD receives a frame with frame ID 01 and performs a lookup in its replica list (located at the lower MAC of STA4). It finds frame ID 01 in its (local) replica list and therefore discards, eliminates or drops the identified replica frame at the lower MAC of STA4, i.e. does not forward the identified replica to the upper MAC of the second MLD MLDB.

[0064] The upper-layer MAC of the second MLD (MLDB) can coordinate the removal of FSIDs from the local replica list of the lower-layer MAC, for example, when the information has been stored in the replica list for longer than the frame's latency requirements. Assume the latency requirements of the critical real-time stream are known.

[0065] It should be understood that a flow ID to link mapping can be used instead of a TID to link mapping. In this case, the flow ID to link mapping can be set by the (multi)link control element of the management frame (MMPDU). Therefore, the MSDU can then be mapped to one or more corresponding links based on its flow ID.

[0066] The proposed implementation enables deterministic communication in IEEE 802.11be Wi-Fi networks and later. Reduced average latency and jitter are achieved by replicating frames on disjoint paths, allowing for a higher probability of successful packet transmission. Furthermore, frame replication across multiple links improves reliability by reducing the probability of retransmissions due to link failures or interference. Compared to existing solutions, the proposed implementation requires less hardware to transmit copies. Generally, using MLO for redundant transmission reduces hardware costs and simplifies network setup.

[0067] Go to Figure 8 The image shows a management frame for setting up an MLO with redundant transmissions in an MLD. This management frame includes a header, information elements, and a Frame Check Sequence (FCS). IEEE 802.11 MAC distinguishes five different MAC addresses: Basic Service Set Identifier (BSSID), Destination Address (DA), Source Address (SA), Receive Address (RA), and Transmit Address (TA). Management frames can be used to set up an MLO with the redundant transmissions shown in the image. The 802.11 management frame has… Figure 8 The structure is shown below. Management frames use information elements to transmit information to other systems. Management frames use a fixed-length field called a fixed field and a variable-length field called an information element. Information elements can have different sizes. The information element is a variable-length component of the management frame. A general information element has an ID number, length, and a variable-length component.

[0068] The Information Element (IE) contained in the management frame allows MLDs to exchange their capabilities and / or operating parameters. For this purpose, 802.11be defines the Multilink Element (MLE). This MLE can be used to discover and / or configure one or more MLDs.

[0069] Therefore, information elements (such as Figure 8 The multi-link element (MLD) can be used to set and / or indicate changes to the mapping of frames (e.g., between TID values ​​and links). For example, all TIDs can be assigned to all links by the multi-link element, allowing for a full adaptive load balancing strategy as traffic can move partially or completely between multiple links. Furthermore, information elements such as the multi-link element can be used to assign TIDs to two or more links for redundant transmission and / or redundant reception. Thus, once an MLD is set or configured, a frame can be transmitted on two or more links based on its TID. Similarly, an MLD can be configured by the MLE in a management frame to receive frames via two or more links. That is, two or more links for an MLD can be used for redundant transmission and / or redundant reception.

[0070] As mentioned in this document, a mapping from flow ID to link can be performed instead of a mapping from TID to link. Data flows can be established between sites receiving and / or sending MLDs. Data flows can be identified by their flow IDs. A data flow can be understood as a set of Media Access Control (MAC) Service Data Units (MSDUs) to be delivered (constrained by the provided Quality of Service (QoS) parameter values). The MAC entity can determine the appropriate link for delivering MSDUs belonging to a specific data flow based on the flow IDs provided at the MAC Service Access Point (MAC SAP) along with those MSDUs.

[0071] Figures 9 to 26 Exemplary method steps according to various implementations are shown.

[0072] like Figure 9 As shown, in step S1, the first MSDU is received by the first MLD via the SAP on the upper MAC sublayer of the first MLD. In step S2, a first copy of the first MSDU is forwarded to the first STA on the lower MAC sublayer of the first MLD. In step S3, a second copy of the first MSDU is forwarded to the second STA on the lower MAC sublayer of the first MLD.

[0073] like Figure 10 As shown, in step S4, a first header of a first MPDU with the MAC address of the first STA is created, and the first MPDU includes a first copy. In step S5, a second header of a second MPDU with the MAC address of the second STA is created, and the second MPDU includes a second copy.

[0074] In step S6, as Figure 11 As shown, a first STA on the lower MAC sublayer of the first multi-link device is determined. In step S7, a second station on the lower MAC sublayer of the first multi-link device is determined. Steps S7 and / or S7 can be performed during setup, i.e., during MLD configuration or during the processing of one or more MSDUs by the MLD.

[0075] In step S8, the first station transmits a first MPDU via a first link in at least one first physical layer protocol data unit (PPDU), and in step S8, the second station transmits a second MPDU including a second copy via a second link in at least one second PPDU.

[0076] In step S10, as Figure 12As shown, the first and second sites of the first multi-link device provide link-specific lower-layer media access control (MAC) and one or more physical layer (PHY) services. In step S11, a single MAC service access point (SAP) is provided from the upper MAC sublayer of the first multi-link device to, for example, the logical link control (LLC) sublayer of the host device.

[0077] like Figure 13 As shown, in step S12, a QoS value is determined, such as a service identifier value or a flow ID associated with the first MSDU. In step S13, a first site and a second site are determined based on the QoS value or the flow ID, for example, by mapping a first copy to the first site and a second copy to the second site.

[0078] like Figure 14 As shown in step S12, the (multi)link control element of the management frame (e.g., MMPDU) can be determined; in step S15, the first and second sites can be determined based on the (multi)link control element. The multi-link control element can be used to implement TID-to-link mapping or flow ID-to-link mapping as described herein. Therefore, in step S16, the upper MAC sublayer can be configured to forward the MPDU to the first and second sites, for example, based on the configuration information provided in the multi-link control element.

[0079] like Figure 15 As shown in step S17, the sequence number FSID can be assigned to the first MPDU, preferably to the header field element of the first MPDU, and most preferably to the QoS field element. In step S18, the same sequence number is assigned to the second MPDU, preferably to the header field element of the second MPDU, and most preferably to the QoS field element. In step S19, after forwarding the first and second copies, the sequence number (FSID) is incremented.

[0080] according to Figure 16 In step S20, the first station accesses the first transmission channel associated with the first link. In step S21, the second station accesses the second transmission channel associated with the second link. Therefore, in step S22, the first PPDU and the second PPDU are transmitted synchronously on the first link and the second link. The first PPDU includes a first MPDU, and the second PPDU includes a second MPDU.

[0081] like Figure 17As shown, in step S23, the first station uses a first channel access mechanism to access the first transmission channel. The second station uses a second channel access mechanism to access the second transmission channel, as shown in step S24. As shown in step S25, the first channel access mechanism may be the same as or different from the second channel access mechanism.

[0082] It should be understood that, in combination Figures 9 to 17 The described steps are preferably performed by the first MLD, i.e., the sending MLD, but the sending MLD can become the receiving MLD, i.e., when one or more PPDUs are received from a sending MLD.

[0083] like Figure 18 As shown, in step S26, a first MPDU including a first copy of the first MSDU is received by a third station on the lower MAC sublayer of the second multi-link device.

[0084] In step S27, the fourth station on the lower MAC sublayer of the second multi-link device preferably receives the second MPDU, which includes a second copy of the first MSDU, via the second link. It should be understood that the first MPDU and the first MSDU may correspond to those of the first MLD already transmitted as described herein, in order to establish redundant transmission of the MSDU. Therefore, one of the redundantly received PPDU or MPDU needs to be eliminated or discarded, for example, to avoid congestion or redundant information.

[0085] like Figure 19 As shown in step S28, the first MPDU is forwarded by the third station on the lower MAC sublayer of the second multi-link device to the service access point on the upper MAC sublayer of the second multi-link device. In step S29, the second MPDU is forwarded by the fourth station on the lower MAC sublayer of the second multi-link device to the service access point on the upper MAC sublayer of the second multi-link device.

[0086] As shown in step S30 of Figure 30, the third station receives the first MPDU in at least one first PPDU packet via the first link. In step S31, the fourth station receives the second MPDU in at least one second PPDU via the second link. In step S32, therefore, the first and second copies can be received synchronously or asynchronously.

[0087] like Figure 21 As shown, in step S33, the third and fourth stations of the second multi-link device provide link-specific lower-layer media access control (MAC) and one or more physical layer (PHY) services. In step S34, the upper MAC sublayer (entity) of the second multi-link device provides a single MAC service access point (SAP) to, for example, the logical link control (LLC) sublayer of the host device.

[0088] like Figure 21 As shown, a third station and a fourth station on the lower MAC sublayer of the second multi-link device are determined. This can occur during the configuration of the second multi-link device or during MPDU forwarding. In step S36, the third and fourth stations on the lower MAC sublayer of the second multi-link device are caused to forward the MPDU to the upper MAC sublayer of the second multi-link device.

[0089] exist Figure 23 In step S37, the sequence number FSID of the first copy is preferably determined in the header field element of the first MPDU, and most preferably in the QoS field element. In step S38, the sequence number FSID of the second copy is preferably determined in the header field element of the second MPDU, and most preferably in the QoS field element.

[0090] exist Figure 24 In step S39, at least one sequence number (FSID) of the first copy and / or the second copy or MPDU received by the second multi-link device is stored in at least one of the upper MAC sublayer, the third station on the lower MAC sublayer, and the fourth station on the lower MAC sublayer. In step S40, the second multi-link device compares the sequence number (FSID) of the received first copy and / or the second copy or MPDU with the stored sequence number. In step S41, if the sequence number is equal to the stored sequence number, the first copy and / or the second copy or MPDU is eliminated or discarded.

[0091] like Figure 25 As shown in step S42, the second multi-link device stores at least one sequence number (FSID) of the received first copy and / or second copy or MPDU in at least one of the upper MAC sublayer, the third station on the lower MAC sublayer, and the fourth station on the lower MAC sublayer. In step S43, the sequence number of the received first copy and / or second copy or MPDU is compared with the stored sequence number. In step S44, if the sequence number is not equal to the stored sequence number, the first copy and / or second copy is forwarded.

[0092] like Figure 26 As shown in step S45, at least one sequence number (FSID) of the first and / or second replicas received by the second multi-link device is stored in at least one of the upper MAC sublayer, the third station on the lower MAC sublayer, and the fourth station on the lower MAC sublayer. In step S46, the sequence numbers of the received first and / or second replicas or MPDUs are stored at predetermined time intervals, wherein the duration preferably corresponds to the delay requirement of the first MSDU or MPDU.

[0093] The steps described herein can be executed by a first MLD and a second MLD, respectively, and by a system including the first MLD and the second MLD. Furthermore, the steps described herein can be implemented by a computer program including program code that, when executed, performs the steps described herein, for example, by the first MLD and / or the second MLD as described herein.

Claims

1. A method for redundant transmission on a first link and a second link, comprising: The first MAC service data unit (MSDU) is received via the service access point SAP on the upper MAC sublayer of the first multi-link device (MLD1); Forward the first copy (MPDU1) of the first MSDU to the first station (STA1) STA on the lower MAC sublayer of the first multi-link device (MLD1); as well as Forward the second copy (MPDU2) of the first MSDU to the second station (STA) on the lower MAC sublayer of the first multi-link device (MLD1). A first MAC Protocol Data Unit (MPDU1) with the MAC address of the first station (STA1) is created. The first MPDU (MPDU1) includes the first copy. as well as The second site (STA2) creates a second header (H2) of a second MPDU (MPDU2) having the MAC address of the second site (STA2), the second MPDU (MPDU2) including the second copy.

2. The method according to the preceding claims, determining the first station (STA1) on the lower MAC sublayer of the first multi-link device (MLD1) and determining the second station (STA2) on the lower MAC sublayer of the first multi-link device (MLD1).

3. The method according to any one of the preceding claims, wherein the first station (STA1) transmits the first MPDU (MPDU1) in at least one first physical layer protocol data unit (PPDU1) via the first link, and the second station transmits the second MPDU in at least one second PPDU (PPDU2) via the second link.

4. The method according to any one of the preceding claims, wherein the first station and the second station (STA2) of the first multi-link device (MLD1) provide link-specific lower-layer media access control (MAC) and one or more physical layer (PHY) services; A single MAC service access point (SAP) is provided from the upper MAC sublayer of the first multi-link device (MLD1) to the logical link control (LLC) sublayer.

5. The method according to any one of the preceding claims, wherein, The step of determining the first station (STA1) and the second station (STA2) on the lower MAC sublayer of the first multi-link device (MLD1) includes: Determine a QoS value, such as a service identifier value, or a flow identifier associated with the first MSDU (MSDU1); The first site (STA1) and the second site (STA2) are determined based on the QoS value or flow ID, for example, by mapping the first copy and / or the first MPDU (MPDU1) to the first site (STA1) and mapping the second copy and / or the second MPDU (MPDU2) to the second site (STA).

6. The method according to any one of the preceding claims, wherein, The steps for determining the first station (STA1) and the second station (STA2) on the lower MAC sublayer of the first multi-link device (MLD1) include: Determine the (Multi)Link Control Element (MLE) of the Management Frame (MMPDU); The first site and the second site (STA1, STA2) are determined based on the (Multi) Link Control Element (MLE); and The upper MAC sublayer is configured to forward MPDUs to the first station and the second station (STA1, STA2).

7. The method according to any one of the preceding claims, wherein, Forwarding the first copy of the first MSDU to the first site (STA1) and forwarding the second copy of the first MSDU to the second site (STA2) includes: Assign a sequence number (FSID) to the first MPDU, preferably to a header field element of the first MPDU, and most preferably to a QoS field element; and The same sequence number is assigned to the second MPDU, preferably to the header field element of the second MPDU, and most preferably to the QoS field element.

8. The method according to any one of the preceding claims, wherein the upper MAC sublayer increments the sequence number (FSID) after forwarding the first copy and / or the second copy and / or the first MPDU and / or the second MPDU.

9. The method according to any one of the preceding claims, The first transmission channel associated with the first link is accessed by the first station (STA1); as well as The second transmission channel associated with the second link is accessed by the second station (STA2); as well as Transmit the first PPDU and the second PPDU (PPDU1, PPDU2) synchronously (asynchronously).

10. The method according to any one of the preceding claims, wherein the first station (STA1) accesses the first transmission channel using a first channel access mechanism and the second station (STA2) accesses the second transmission channel using a second channel access mechanism, wherein, The first channel access mechanism is the same as the second channel access mechanism.

11. The method according to any one of the preceding claims, wherein the first station (STA1) accesses the first transmission channel using a first channel access mechanism and the second station (STA2) accesses the second transmission channel using a second channel access mechanism, wherein, The first channel access mechanism is different from the second channel access mechanism.

12. A method for redundant reception on a first wireless link and a second wireless link, comprising: The first MPDU (MPDU1) is received by a third station (STA3) on the lower MAC sublayer of the second multi-link device (MLD2), preferably via the first link. The first MPDU includes a first copy of the first MSDU. as well as The second MPDU, which includes a second copy of the first MSDU, is received by the fourth station (STA4) on the lower MAC sublayer of the second multi-link device (MLD2), preferably via the second link.

13. The method according to the preceding claim, The first MPDU (MPDU1) is forwarded by the third station (STA1) on the lower MAC sublayer of the second multi-link device (MLD2) to the service access point on the upper MAC sublayer of the second multi-link device (MLD2); and / or The second MPDU (MPDU2) is forwarded by the fourth station (STA4) on the lower MAC sublayer of the second multi-link device (MLD2) to the service access point on the upper MAC sublayer of the second multi-link device (MLD2).

14. The method according to any one of claims 12 to 13, wherein the third station (STA3) receives the first MPDU (MPDU1) via a first link in at least one first PPDU (PPDU1), and the fourth station (STA4) receives the second MPDU (MPDU2) via a second link in at least one second PPDU (PPDU2).

15. The method according to any one of claims 12 to 14, The third and fourth stations of the second multi-link device (MLD2) provide link-specific lower-layer media access control (MAC) and one or more physical layer (PHY) services. The upper MAC sublayer (entity) of the second multi-link device (MLD2) provides a single MAC service access point (SAP) to, for example, the logical link control (LLC) sublayer of the host device.

16. The method according to any one of claims 12 to 15, The third station (STA3) and the fourth station (STA4) on the lower MAC sublayer of the second multi-link device (MLD2) are determined, preferably by determining the (multi)link control element of the management frame (MMPDU), and most preferably based on the (multi)link control element. The third and fourth stations on the lower MAC sublayer of the second multi-link device (MLD2) are configured to forward MPDUs to the upper MAC sublayer of the second multi-link device (MLD2).

17. The method according to any one of claims 12 to 16, wherein, The forwarding of the first MPDU (MPDU1) by the third station (STA3) and the forwarding of the second MPDU (MPDU2) by the fourth station (STA4) includes: Preferably, the sequence number (FSID) of the first copy and / or the first MPDU (MPDU1) is determined in the header field element of the first MPDU (MPDU1), most preferably in the QoS field element; and Preferably, the sequence number (FSID) of the second copy or the second MPDU (MPDU2) is determined in the header field element of the second MPDU (MPDU2), and most preferably in the QoS field element.

18. The method according to any one of claims 12 to 17, wherein the first copy and the second copy and / or the first MPDU (MPDU1) and / or the second MPDU (MPDU2) are received synchronously (asynchronously).

19. The method according to any one of claims 12 to 18, wherein at least one sequence number (FSID) of the first copy and / or the second copy and / or the first MPDU and / or the second MPDU (MPDU1, MPDU2) received by the second multi-link device (MLD2) is stored in at least one of the upper MAC sublayer, the third station (STAS) on the lower MAC sublayer, and the fourth station (STA4) on the lower MAC sublayer, for example, in a copy list (DL1, DL2, DL3).

20. The method according to any one of claims 12 to 19, The sequence number (FSID) of the first copy and / or the second copy and / or the first MPDU and / or the second MPDU (MPDU1, MPDU2) received by the second multi-link device (MLD2) is compared with the stored sequence number. If the serial number is equal to the stored serial number, discard the first copy and / or the second copy and / or the first MPDU and / or the second MPDU (MPDU1, MPDU2).

21. The method according to any one of claims 12 to 20, Compare the sequence numbers of the received first copy and / or second copy and / or first MPDU and / or second MPDU (MPDU1, MPDU2) with the stored sequence numbers; If the sequence number is not equal to the stored sequence number, forward the first copy and / or the second copy and / or the first MPDU and / or the second MPDU (MPDU1, MPDU2).

22. The method according to any one of claims 12 to 21, wherein the sequence numbers of the received first copy and / or second copy and / or first MPDU and / or second MPDU (MPDU1, MPDU2) are stored at predetermined time intervals, wherein, The duration preferably corresponds to the delay requirement of the first MPDU.

23. A first multi-link device, preferably comprising a processor and a memory, operable to perform the steps of the method according to any one of claims 1 to 11.

24. A second multi-link device, preferably comprising a processor and a memory, operable to perform the steps of the method of any one of claims 12 to 22.

25. A system for redundant transmission and / or redundant reception on a first link and a second link between a first multi-link device (MLD1) according to claim 23 and a second multi-link device (MLD2) according to claim 24.

26. A computer program comprising program code that, when executed, performs the steps of any one of claims 1 to 11 and / or any one of claims 12 to 22.

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