Devices and methods for non co-located multi-link operation in a WLAN

Abstract

A Multi-Link Device, MLD, (110) with a plurality of affiliated stations, i.e. access points, APs, or non-AP stations, (113a-c) for Non Co-Located Multi-Link Operation communication via a plurality of links (130a-c) with a further peer MLD (120) with a plurality of further affiliated stations (123a-c) is disclosed. The MLD (110) comprises processing circuitry (111) configured to assign a global packet number, PN, but no sequence number, SN, to a MAC Service Data Unit, MSDU, payload, wherein the MSDU payload comprises a MSDU, an aggregate MSDU, A-MSDU, or a MAC Management Protocol Data Unit, MMPDU, irrespective of whether the MSDU payload is further cryptographically encapsulated or not. The processing circuitry (111) may be further configured to cryptographically encapsulate the MSDU payload.

Description

[0001] DEVICES AND METHODS FOR NON CO-LOCATED MULTI-LINK OPERATION IN A WLAN

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to wireless communications. More specifically, the present disclosure relates to devices and methods for Non Co-Located Multi -Link Operation, NC MLO, in a wireless local area network, WLAN, in particular a WLAN (also referred to as Wi-Fi network) according to the IEEE 802.11 framework of standards.

[0004] BACKGROUND

[0005] Wireless Local Area Network (WLAN) technology as defined by the IEEE 802.11 framework of standards is being enhanced with an objective of improving both throughput and reliability. IEEE 802.1 Ibe has introduced multi -link operation (MLO) that allows a multi-link device (MLD), for instance, an access point, AP, MLD, to communicate with a peer MLD, for instance, a non-AP MLD, through affiliated stations using one or multiple setup links simultaneously. An AP MLD has one or more affiliated APs, where each affiliated AP is operating on a different link. Similarly, a non-AP MLD has one or more affiliated non-AP STAs, where each affiliated non-AP STA is operating on a different link. Functionality-wise, an MLD can be also viewed as composed of an Upper MAC sublayer and a Lower MAC sublayer, where the affiliated STAs are implemented in the Lower MAC sublayer.

[0006] An MLD as defined in IEEE 802.1 Ibe is assumed to operate as a co-located MLD, where the Upper MAC sublayer and the Lower MAC sublayer reside in the same device. Thus, for a co-located MLD there are no communication delays between layers, no limitations on the information that can be exchanged, and static (i.e. non- dynamic) fragmentation is not permitted.

[0007] A further standards amendment, IEEE 802.1 Ibn builds on IEEE 802.1 Ibe and is looking to define Non Co-Located, NC, MLO, where the MLD Upper MAC sublayer and the MLD Lower MAC sublayer are considered as different entities / components that can be at different physical locations (i.e. non-co-located entities). However, NC MLO is limited, for instance, by tight operational timing requirements defined for co-located MLO. Therefore, improved devices and methods are required for facilitating NC MLD operation without fundamentally changing data traffic management defined by the IEEE 802.11 framework of standards.

[0008] SUMMARY

[0009] It is an objective of the present disclosure to provide improved devices and methods for Multi-Link Operation; MLO, in a wireless local area network, WLAN, in particular a WLAN according to the IEEE 802.11 framework of standards.

[0010] The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

[0011] According to a first aspect a Multi-Link Device, MLD, is provided with a plurality of affiliated stations, i.e. access points, APs, or non-AP stations, for Non-Collocated, N C, Multi -Link Operation, MLO, communication via a plurality of links with a further peer MLD with a plurality of further affiliated stations, i.e. non-AP stations or APs. The MLD, in particular an upper MAC sublayer of the MLD comprises processing circuitry configured to assign a global packet number, PN, but not a sequence number, SN, to a MAC Service Data Unit, MSDU, payload, wherein the MSDU payload comprises a MSDU, an aggregate MSDU, A-MSDU, ora MAC Management Protocol Data Unit, MMPDU, irrespective of whetherthe MSDU payload is further cryptographically encapsulated or not. As defined by the IEEE 802.11 framework of standards, the PN may be generated and communicated in a PN field.

[0012] In a further possible implementation form, the processing circuitry is further configured to cryptographically encapsulate the MSDU payload.

[0013] In a further possible implementation form, the MLD further comprises a communication interface configured to distribute the MSDU pay load or the cryptographically encapsulated MSDU payload to one or more of the plurality of NC MLD Lower MAC sublayers implemented by the affiliated stations. Each of the one or more affiliated stations is configured to assign a respective local SN to the MSDU pay load or the cryptographically encapsulated MSDU payload and to generate one or more MPDUs based on the MSDU payload or the cryptographically encapsulated MSDU payload. As defined by the IEEE 802.11 framework of standards, the SN may be generated and communicated in an SN field.

[0014] In a further possible implementation form, each of the one or more affiliated stations is further configured to transmit a data or management frame including the one or more MPDUs including the MSDU payload or the cryptographically encapsulated MSDU pay load to one or more of the plurality of further affiliated stations of the further peer MLD.

[0015] In a further possible implementation form, in case of a MPDU reception failure, e.g. no Block ACK frame is received for the corresponding MDSU payload (or part of thereof), the communication interface of the MLD is configured to distribute the MSDU pay load or the cryptographically encapsulated MSDU pay load to one or more other affiliated stations of the plurality of affiliated stations, wherein each of the one or more other affiliated stations of the plurality of affiliated stations is configured to generate, based on the MSDU payload or the cryptographically encapsulated MSDU payload, one or more further Management Protocol Data Units, MMPDUs, to assign a respective local SN to the one or more further MPDUs, including the MSDU payload or the cryptographically encapsulated MSDU payload, and to transmit the one or more further MPDUs, including the MSDU pay load or the cryptographically encapsulated MSDU pay load, to one or more of the plurality of further affiliated stations of the further peer MLD.

[0016] In a further possible implementation form, each of the one or more of the plurality of affiliated stations is further configured to setup a Block ACK agreement for each TID with the corresponding further affiliated station (i.e. that is operating on the same link) in order to transmit A-MPDU and receive a respective block acknowledgment, BA, frame from the corresponding further affiliated station of the plurality of further affiliated stations of the further MLD and to maintain a scoreboard indicative of the successfully and unsuccessfully transmitted one or more MPDUs, wherein each of the one or more of the plurality of affiliated stations is further configured to perform a retransmission of any unsuccessfully transmitted MPDUs based on the scoreboard.

[0017] In a further possible implementation form, the BA frame comprises the SNs of the successfully and unsuccessfully transmitted one or more MPDUs.

[0018] In a further possible implementation form, each of the plurality of affiliated stations is further configured to encrypt at least a respective portion of the one or more MPDUs with one or more per-link encryption keys both group and pairwise and to transmit the one or more at least partially encrypted MPDUs to the one or more of the plurality of further affiliated stations of the further peer MLD. These one or more per-link encryption keys may be group keys or pairwise keys.

[0019] In a further possible implementation form, each of the plurality of affiliated stations is configured to implement a protocol stack including a lower MAC layer, wherein the lower MAC layer is configured to assign the respective local SN to the one or more MPDUs, including the MSDU pay load or the cryptographically encapsulated MSDU pay load. In a further possible implementation form, the processing circuitry of the MLD is configured to implement a protocol stack including an upper MAC layer, wherein the upper MAC layer is configured to assign the packet number, PN, to the MSDU payload.

[0020] In a further possible implementation form, the processing circuitry is configured to add Counter Mode Cipher Block Chaining Message Authentication Code Protocol, CCMP, or Galois Counter Mode Protocol, GCMP, header information to the MSDU payload or the cryptographically encapsulated MSDU payload, wherein the CCMP or GCMP header information comprises the packet number.

[0021] According to a second aspect a method is provided of operating a Multi-Link Device, MLD, with a plurality of affiliated stations, i.e. access points, APs, or non-AP stations, for NC MLO communication via a plurality of links with a further peer MLD with a plurality of further affiliated stations, i.e. non-AP stations or APs. The method comprises assigning by a processing circuitry of the MLD a global packet number, PN, but not a sequence number, SN, to a MAC Service Data Unit, MSDU, payload, wherein the MSDU payload comprises a MSDU, an aggregate MSDU, A-MSDU, or a MAC Management Protocol Data Unit, MMPDU, irrespective of whether the MSDU pay load is further cryptographically encapsulated or not.

[0022] The method according to the second aspect can be performed by the MLD according to the first aspect. Thus, further features of the method according to the second aspect result directly from the functionality of the MLD according to the first aspect as well as its different implementation forms described above and below.

[0023] According to a third aspect a Multi-Link Device, MLD, with a plurality of affiliated stations, i.e. access points, APs, or non- AP stations, is provided for NC MLO communication via a plurality of links with a further peer MLD with a plurality of further affiliated stations, i.e. non-AP stations or APs. Each affiliated station is configured to receive one or more MAC Protocol Data Units, MPDUs, from one or more of the plurality of further affiliated stations, and derive an MSDU payload or a cryptographically encapsulated MSDU payload based on the one or more MPDUs. The MLD comprises a communication interface configured to receive from one more of the plurality of affiliated stations the MSDU payload or the cryptographically encapsulated MSDU pay load, wherein the MLD further comprises processing circuitry configured to extract a packet number, PN, from the MSDU payload or the cryptographically encapsulated MSDU pay load, i.e. assigned to the MSDU pay load or the cryptographically encapsulated MSDU payload, and to verify based on the extracted PN whether the MSDU payload or the cryptographically encapsulated MSDU pay load is a duplicate, i.e. already has been received by the MLD through another link.

[0024] In a further possible implementation form, each affiliated station is configured to extract an SN from each of the one or more MPDUs received from the affiliated station of the transmitting MLD and to determine, based on the respective SN, whether the respective MPDU is a duplication, i.e. already has been received by the respective station.

[0025] In a further possible implementation form, each affiliated station is further configured to maintain a Block ACK agreement for each TID with the corresponding further affiliated station (i.e. that is operating on the same link and has initiated the Block ACK agreement for each TID) in order to respond with a respective block acknowledgment, BA, frame to the corresponding further affiliated STA of the plurality of further affiliated stations of the further peer MLD for maintaining a scoreboard indicative of the successfully and unsuccessfully transmitted one or more MPDUs in the initiating further affiliated STA.

[0026] According to a fourth aspect a method is provided of operating a Multi -Link Device, MLD, with a plurality of affiliated stations, i.e. access points, APs, or non-AP stations, for NC MLO communication via a plurality of links with a further peer MLD with a plurality of further affiliated stations, i.e. non-AP stations or APs. The method according to the fourth aspect comprises the following steps performed by an affiliated station: receiving one or more MAC Protocol Data Units, MPDUs, from one or more of the plurality of further affiliated stations; and deriving an MSDU pay load or a cryptographically encapsulated MSDU pay load based on the one or more MPDUs.

[0027] Moreover, the method comprises the following steps performed by the MLD: receiving from one more of the plurality of affiliated stations the MSDU payload or the cryptographically encapsulated MSDU payload; extracting a packet number, PN, from the MSDU payload or the cryptographically encapsulated MSDU pay load, i.e. assigned to the MSDU pay load or the cryptographically encapsulated MSDU pay load; and verifying based on the extracted PN whether the MSDU payload or the cryptographically encapsulated MSDU payload is a duplicate, i.e. already has been received by the MLD through another link.

[0028] The method according to the fourth aspect can be performed by the MLD according to the third aspect. Thus, further features of the method according to the fourth aspect result directly from the functionality of the MLD according to the third aspect as well as its different implementation forms described above and below.

[0029] According to a fifth aspect a computer program product is provided, comprising program code which causes a computer or a processor to perform the method according to the second aspect or the method according to the fourth aspect, when the program code is executed by the computer or the processor.

[0030] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:

[0033] Fig. 1 shows a schematic diagram illustrating an MLD according to an embodiment with a plurality of affiliated APs in communication via a plurality of links with a further MLD according to an embodiment with a plurality of affiliated non-AP stations;

[0034] Fig. 2 shows a schematic diagram illustrating a conventional co-located AP MLD with a plurality of affiliated APs in communication via a plurality of links with a further conventional co-located, associated non-AP MLD according to an embodiment with a plurality of affiliated non-AP stations;

[0035] Fig. 3 shows a schematic diagram illustrating the conventional IEEE 802.1 Ibe MLD operation of data frame transmission for the assignment of sequence numbers;

[0036] Fig. 4 shows a schematic diagram illustrating in more detail an NC AP MLD according to an embodiment with a plurality of NC affiliated APs; Fig. 5 shows a schematic diagram illustrating an NC AP MLD according to an embodiment with a plurality of affiliated APs in communication via a plurality of links with a further NC non-AP MLD according to an embodiment with a plurality of affiliated non-AP stations;

[0037] Fig. 6 shows a schematic diagram illustrating an NC AP MLD according to an embodiment with a plurality of affiliated APs in communication via a plurality of links with a further co-located (UHR) non-AP MLD according to an embodiment with a plurality of affiliated non-AP stations;

[0038] Fig. 7 shows a schematic diagram illustrating an NC MLD according to an embodiment with a plurality of affiliated APs in communication via a plurality of links with a further NC MLD according to an embodiment with a plurality of affiliated non- AP stations;

[0039] Fig. 8 shows a schematic diagram illustrating a frame processing protocol stack implemented in the upper MAC sublayer by an NC MLD or UHR (Co-located) non-AP MLD according to an embodiment for transmitting or receiving an MSDU payload;

[0040] Fig. 9 shows a schematic diagram illustrating a frame processing protocol stack implemented in the lower MAC sublayer by an STA affiliated with an NC MLD according to an embodiment for transmitting or receiving an MPDU;

[0041] Fig. 10 shows a flow diagram illustrating steps of a method of operating an NC MLD in a transmit direction according to an embodiment; and

[0042] Fig. 11 shows a flow diagram illustrating steps of a method of operating an NC MLD in a receive direction according to an embodiment.

[0043] In the following, identical reference signs refer to identical or at least functionally equivalent features.

[0044] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

[0046] For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and / or aspects described herein may be combined with each other, unless specifically noted otherwise. Figure 1 shows a Multi-Link Device, AP MLD, 110 with a plurality of affiliated access points, APs, 113a-c communicating via a plurality of setup links 130a, b (for instance a 2.4 GHz link 130a and a 5 GHz link 130b) with a plurality of the corresponding non-AP stations 123a, b affiliated with a further associated MLD 120 in a wireless local area network, WLAN, 100 in particular an IEEE 802.11 based WLAN (also referred to as Wi-Fi network 100), using a Multi-Link Operation, MLO, mode. The MLD 110 with the affiliated APs 113a-c is herein also referred to as AP MLD 110, while the further or peer MLD

[0047] 120 with the affiliated non-AP stations 123a, b is referred to as non-AP MLD 120 or MLD station 120. For the most part, data and most management traffic may be exchanged directly between the MLDs 110, 120 through on or more of the affiliated APs 113a,b. Control traffic, however, is usually exchanged between the affiliated non-AP STAs 123a, b and the affiliated APs 113a,b on a given link 130a or 130b. In the MLO mode communications between the two MLDs 110, 120 may use either one of the independently operating radio links 130a,b.

[0048] As will be appreciated, MLO at the MAC layer together with a multi-link device (MLD), such as the AP MLD 110 and the non-AP MLD 120, has been introduced in IEEE 802.1 Ibe. MLO provides requirements for MLDs to maintain multiple WLAN connections across multiple links. A multiple link may also include a single radio STA that is able to multiplex between different frequency bands providing multiple logical WLAN connections. It allows traffic to flow on multiple links and provides a performance gain of using multiple channels. As already described above, each link, such as the links 130a, b shown in figure 1, is established during an ML setup procedure between STAs affiliated with the MLDs.

[0049] In an embodiment, the MLDs 110, 120 may each comprise processing circuitry 111, 121, for instance, one or more processors or CPUs for processing data as well as implementing a respective Upper MAC Layer 111, 121. The processing circuitry 111,

[0050] 121 may be implemented in hardware and / or software and may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The MLDs 110, 120 may further each comprise a memory configured to store executable program code which, when executed by the processing circuitry 111, 121, causes the respective MLD 110, 120 to perform the functions and methods described herein.

[0051] Before describing detailed embodiments of the AP MLD AP 110 and the non-AP MLD 120, in the following some technical background as well as terminology will be introduced making use of one or more of the following abbreviations and / or acronyms:

[0052] AAD Additional Authentication Data

[0053] AP Access Point

[0054] BA Block Acknowledgement

[0055] BSS Basic Service Set

[0056] CCMP Counter Mode Cipher Block Chaining Message Authentication Code Protocol

[0057] EHT Extremely High Throughput

[0058] FN Fragment Number

[0059] GCMP Galois Counter Mode Protocol

[0060] LCP Link Control Protection

[0061] LLC Logical Link Control

[0062] MAC Medium Access Control

[0063] ML Multi-link

[0064] MLD Multi-Link Device

[0065] MLO Multi-Link Operation

[0066] MMPDU MAC Management Protocol Data Unit

[0067] MPDU MAC Protocol Data Unit MSDU MAC Service Data Unit

[0068] MU Multi User

[0069] NC Non-Co-located

[0070] PN Packet Number

[0071] RSNA Robust Security Network Association

[0072] SN Sequence Number

[0073] STA Station

[0074] TID Traffic Identifier

[0075] WLAN Wireless Local Area Network

[0076] UHR Ultra High Reliability

[0077] As used herein, an access point (AP) is a special type of wireless station (STA) that provides access to other networks. An AP can support many connected non-AP STAs. APs use control information to control traffic flow over the wireless medium among all associated non-AP STAs within a BSS.

[0078] As used herein, there are three main types of frames communicated between WLAN STAs, namely data, management, and control frames. Data traffic is exchanged between the AP and one or more stations (STAs) in a WLAN to facilitate communication. The data frames are either generated by the one or more non-AP MLDs or by an external network. This traffic is delivered in a secured manner over the WLAN when the AP and the corresponding non-AP STAs negotiate a cryptographic encapsulation method and keys to encrypt the data traffic. Management traffic is exchanged between the AP and one or more non-AP STAs in a BSS to establish and maintain state of data communications. Security can be negotiated to encrypt or sign management traffic. Control traffic is exchanged between the AP and the non-AP STAs in a BSS to control the flow of the data frame exchange.

[0079] As defined in the IEEE 802.11 framework of standards and as used herein, a MAC Service Data Unit, MSDU, refers to data information that is exchanged with the logical link control (LLC) to higher protocol layers, or to a bridge port.

[0080] An MAC Protocol Data Unit, MPDU, takes the MSDU and maps the information to an 802.11 Data frame by including header information such as address information, a sequence number (SN), QoS information, and CRC checksum, as well as the data payload itself. If secure communication is negotiated between peer MACs, the MPDU is cryptographically encapsulated. A cryptographically encapsulated MPDU also includes a packet number (PN) that is used to perform replay detection for the received data and during the operation of data encryption / decryption.

[0081] Another form of pay load of the MPDU is an MMPDU (MAC Management Protocol Data Unit) which is transported in one or more management frames. The MMPDU occupies a position in the management plane similar to that of the MSDU in the data plane. In WLAN network communications, data can be aggregated using either MSDUs or MPDUs.

[0082] When MSDU aggregation is negotiated, several MSDUs are grouped into a single A-MSDU (aggregate-MSDU). The A-MSDU is used to form the pay load of an MPDU.

[0083] When, MAC peers establish a block ack (acknowledgement) agreement per TID, transmission of A-MPDUs (aggregated MPDUs) that contain MPDUs of that TID can be applied. An A-MPDU consist of several MPDUs that are transmitted for a specific STA within a single PHY protocol data unit (PPDU). A Block acknowledgement (BA) is used to efficiently communicate the status of the reception of the transmitted A-MPDUs.

[0084] IEEE 802.1 Ibe has introduced a multi-link device (MLD), such as the AP MLD 110 and the non-AP MUD 120 illustrated in figure 1. The MLDs 110, 120 communicate over multiple WLAN radio links 130a, b that have been setup between the AP MLD 110 and its associated non-AP MLD 120. The ML setup allows traffic to flow on multiple setup links and provides a performance gain of using multiple channels. The AP MLD 110 has one or more affiliated APs 113a-c, where each affiliated AP 113a-c is operating on a different channel 130a-c. Similarly, the non-AP MLD 120 has one or more affiliated non-AP STAs 123a, b, where each affiliated non-AP STA 123a, b is operating on a different setup link 130a, b.

[0085] In Figure 1, the AP MLD 110 has 3 different links. The non-AP MLD 120 has been associated with the AP MLD 110 by setting up 2 links 13 Oa,b with the AP MLD 110, on which the frames exchanged between the AP MLD 110 and the non-AP MLD 130 can be transmitted.

[0086] An MLD as defined in IEEE 802.1 Ibe is assumed to operate as a co-located MLD, as will be detailed hereinafter. Figure 2 illustrates a conventional co-located AP MLD 10 in communication with a conventional co-located non-AP MLD 20 via three different links. The LLCs 5, 25 provide a respective interface to an external network or a part of a protocol stack of the respective co-located MLD 10, 20.

[0087] As will be appreciated, for the co-located MLDs 10, 20 illustrated in figure 2 the affiliated APs 13a-c and STAs 23a-c as part of a respective Lower MAC sublayer 12, 22 are co-located with the respective processing circuitry 11, 21 implementing the respective Upper MAC sublayer 11, 21, i.e. are integrated within the same device. Consequently, there is no communication delay between layers, there is no limitation on the information that can be exchanged, and static (i.e. non- dynamic) fragmentation is not permitted.

[0088] A further amendment IEEE 802.1 Ibn builds on IEEE 802.1 Ibe and is looking to define NC MLO, where the MLD Upper MAC sublayer and the MLD Lower MAC sublayer are considered as different components that can be at different physical locations (i.e. NC components or entities) of an MLD.

[0089] In the standard amendment IEEE 802.1 Ibe, an SN is assigned to MSDU (if not in A-MSDU), A-MSDU or MMPDU prior to cryptographic encapsulation, whereas PNs are assigned to MPDUs as part of the cryptographic encapsulation prior to encryption (as illustrated by 301 in figure 3). When A-MPDU aggregation is used, traffic over multiple links is aggregated per TID (traffic identifier) at the MLD Upper MAC sublayer using a block ACK agreement for that TID. This mechanism is designed to be backwards compatible with legacy STA operation (e.g. pre-IEEE 802.1 Ibe). On receipt of an MPDU or A- MPDU, replay detection (handled by Packet Numbers, PNs), duplicate detection (handled by Sequence Numbers, SNs) are handled at the MLD Upper MAC sublayer.

[0090] The standard amendment IEEE 802.1 Ibe, defines that an established Block ACK agreement (for specific TID) between MLDs applies to all links that have been setup between the MLDs. Thus, all links are using the same running sequence number space and all affiliated STAs operating on the setup links between the MLDs must merge their (local) BA scoreboard in real time with the MLD for both transmission and reception.

[0091] Although IEEE 802.1 Ibe does not explicitly define an MLD as co-located, the architecture that it describes forces it to be colocated (limiting many future (IEEE 802.1 Ibn) applications) for the following reasons. The MLD upper MAC sublayer assigns SNs to MSDUs, assigns PNs to MPDUs and encapsulates MPDUs. The conventional MLO procedures require the handling of the BA (per TID) globally, i.e. by the MLD, for all the links. Since the MPDUs corresponding to the same TID as well as Block ACK frames may be transmitted and received through different links, it imposes tight timing requirements and dependencies on the information exchanged between the MLD and the affiliated STAs. The timing of acknowledgement procedures and retry procedures requires that the MLD has to be co-located with the affiliated STAs to meet synchronization and performance requirements. This architecture limits a number of improvements that could be made, including: duplication of traffic across multiple links to improve reliability; increasing the number of STAs affiliated with an MLD (i.e. a large virtual MLD) to improve coverage; reducing transition times for a mobile device as it traverses a network to improve mobility.

[0092] The new standards amendment project IEEE 802.1 Ibn is looking to define NC MLD behavior but is limited by this tight operational timing. As will be described in detail in the following embodiments disclosed herein facilitate NC MLD operation, without fundamentally changing 802.11 data traffic management.

[0093] Generally, embodiments disclosed herein provide an NC Multi -Link procedure for frame processing by an NC MLD according to an embodiment, such as the NC AP MLD 110 and the NC non-AP MLD 120 of figure 1. According to an embodiment, the NC Multi-Link procedures may be negotiated between MLDs that support the NC MLO feature during association. To this end, a new UHR capability bit may be added to the association related messages.

[0094] Figure 4 is a schematic diagram illustrating in more detail an NC AP MLD 110 according to an embodiment with a plurality of affiliated APs 113a-c. The NC AP MLD 110 is configured to communicate via the plurality of links 130a-c with a further MLD with a plurality of further affiliated stations. The NC AP MLD 110 comprises processing circuitry 111 configured to assign a global packet number, PN, but no sequence number, SN, to a MAC Service Data Unit, MSDU, payload (which may be provided by a LLC layer 105), wherein the MSDU payload comprises a MSDU, an aggregate MSDU, A-MSDU, or a MAC Management Protocol Data Unit, MMPDU, irrespective of whether the MSDU payload is further cryptographically encapsulated or not. In other words, the processing circuitry 111 of the NC AP MLD 110 implements an Upper MAC sublayer 111 configured to assign a PN (but no SN) to all MSDU payloads that are destined to be transmitted through any of the APs affiliated with the non-AP MLD 113a-c that are part of the setup links with the destination non-AP MLD. As will be described in more detail in the following, this allows to perform replay detection (i.e. management of PNs as currently defined in 802.11) at the MLD Upper MAC sublayer.

[0095] In an embodiment, the processing circuitry implementing the MLD Upper MAC sublayer 111 may further cryptographically encapsulate the MSDU payload having been assigned a PN, provided that Robust security network association, RSNA, has successfully negotiated between the AP MLD and the non-AP MLD. An affiliated station 113a-c receives the encapsulated MSDU payload from the NC MLD 111 (via the interfaces 112 and 114a-c) and creates an MPDU based on the encapsulated MSDU pay load. In an embodiment, the processing circuitry 111 of the MLD 110 may allocate blocks of MSDU payloads to the NC affiliated STAs 113a-c. As will be described in more detail below, the MSDU payload duplicate detection is done through the management of PNs at the NC MLD Upper MAC sublayer of the receiving MLD 120, while the MPDU duplicate detection is performed at the MLD Lower MAC sublayer, decoupling this behavior from the MLD Upper MAC sublayer.

[0096] A local SN is assigned to an MSDU payload (or any part of thereof) in the Lower MAC sublayer by an affiliated STA 113a-c (through which the MPDU is transmitted). More specifically, the MSDU payload (or any part of thereof) is converted to an MPDU and transmitted to the corresponding peer affiliated STA 113a-c. If supported, dynamic Fragmentation may be applied to the MSDU payload prior to the MPDU conversion. Reassembly as well as MPDU duplicate detection may be done by the respective MLD Lower MAC sublayer of the STA affiliated with MLD 120. Afterthe establishment of a Block ACK agreement per TID, A-MPDU can be applied for MPDUs pertain to that TID by the MLD Lower MAC sublayer of the STA affiliated with MLD 110. Additionally, a Block ACK frame can be transmitted by the respective MLD Lower MAC sublayer of the STA affiliated with MLD 120. In an embodiment, per-link encryption keys (both group and pairwise) may be derived for the affiliated STA 113a-c to protect management traffic between the affiliated STA and affiliated AP when management frame protection is applied. As will be appreciated, from an implementation point of view, the lower MAC procedures at the affiliated APs 113a-c do not have to be modified, as they are essentially unchanged from legacy AP operation when security is not negotiated. Therefore, no hardware change is necessary. TID to link mapping stays the same. MPDU fragmentation becomes cleaner, as it just fragments encrypted MSDU pay loads.

[0097] In the following an example of a conventional Block Ack, BA, agreement as defined in IEEE 802.11 will be described in more detail. In addition to the current IEEE 802.1 Ibe MLO architecture, by way of example, a transmission window of 5 frames is assumed which applies to both encryption, transmission, score boarding, and re-ordering.

[0098] An AP MLD 10 has 2 links and 10 MPDUs with SNs 1 - 10. The AP MLD has established BA agreements for the corresponding TIDs (of the above MPDUs) with the non-AP MLD 20:

[0099] (a) MPDUs 1 - 5 are distributed to affiliated API 13a (transmission window);

[0100] (b) MPDUs 6 - 10 wait;

[0101] (c) Affiliated API 13a transmits MPDUs 1-5;

[0102] (d) Affiliated API 13a receives Block ACK frame from affiliated STA 1 23a indicating that MPDU with SN=3 was not successfully received by non-AP MLD 20;

[0103] (e) Scoreboard in affiliated API 13a is updated to indicate reception of MPDUs 1,2, 4, 5;

[0104] (f) Scoreboard is passed up to the AP MLD 10 (1,2, 4, 5), which has to be done for each BA;

[0105] (g) MLD 10 decides to re -transmit MPDU 3 using affiliated API 13a;

[0106] (h) MLD 10 encrypts the remaining MPDUs 6, 7, 8, 9,

[0107] (i) MLD 10 queues (3 retried, 6, 7, 8, ) on API 13a;

[0108] (j) API 13a transmits (3 ,6, 7, 8, 9) to affiliated STA1 23a;

[0109] (k) Affiliated API 13a receives Block ACK frame indicating that (3, 6, 7, 8, 9) have been successfully received by the non-AP MLD 20,

[0110] (l) Scoreboard in affiliated API 13a is updated to indicate the reception of MPDUs 3, 6, 7, 8, 9;

[0111] (m) Scoreboard is passed up to the AP MLD 10;

[0112] (n) MLD 10 still needs to coordinate transmission of MPDU 10 on a link.

[0113] As will be appreciated, the above steps (a), (f), (g), (i), (m), (n) are affected by communication delay between the affiliated AP 13a and the conventional AP MLD 10.

[0114] The above example for the Block Ack agreement will be performed by the MLDs 110, 120 according to an embodiment in the following way. As for the example above, a width of 5 frames for transmission and score boarding (can be different values on different links) and a width of 10 frames for encryption and re-ordering is assumed.

[0115] The AP MLD 110 maintains a re-ordering window for encrypted frames and has 2 links and 10 MSDU payloads with PNs 1 - 10:

[0116] (a) AP MLD 110 encrypts all MSDU payloads 1-10 (no limit from the transmission window parameter);

[0117] (b) MSDU pay loads 1 - 10 are distributed to affiliated API 113a;

[0118] (c) API 113a assigns, by way of example, SNs 17-26 to encrypted MSDUs;

[0119] (d) The corresponding MPDUs 17, 18, 19, 20, 21 are transmitted to STA1 123a (transmission window is applied);

[0120] (e) API 113a receives a Block ACK frame indicating the successful reception of MPDUs 17, 18, 20, 21 (19 is lost);

[0121] (f) Scoreboard in affiliated API 113a is updated to indicate reception of MPDUs 17, 18, 20, 21;

[0122] (g) Affiliated API 113a advances the transmission window to include the following MPDUs 19, 22, 23, 24, 25 (MPDUs 19 is retransmitted); (h) API 113a transmits 19, 22, 23, 24, 25 to STA1 123a;

[0123] (i) API 113a receives Block ACK frame for the successful reception of MPDUs 19, 22, 23, 24, 25;

[0124] (j) API 113a transmits MPDU 26;

[0125] (k) API 113a receives Block ACK frame for MPDU 26;

[0126] (l) API 113a acknowledges transmission of MSDU payloads with PNs 1-10 to AP MLD 110.

[0127] As will be appreciated, only the above steps (b) and (1) are affected by communication delay between the affiliated AP 113a and the AP MLD 111. Thus, embodiments disclosed herein allow to significantly decrease the number of transactions between NC AP MLD entities as well as their dependency on the transmission and reception of frames over the wireless medium, thus improving both efficiency and throughput.

[0128] In an embodiment, the NC MLO procedure applies to data or management frames sent between the NC MLDs 110, 120, e.g. the AP MLD 110 and non-AP MLD 120 that support NC AP operation. As already described above in the context of figure 5, the processing circuitry implementing the Upper MAC sublayer 111 of the transmitting NC MLD 110 assigns a Packet Number (PN) to an MSDU payload. The processing circuitry 111 of the NC-MLD 110 then distributes the MSDU payload, identified by its PN, to one of the affiliated STAs 113a-c for transmission. In an embodiment, the processing circuitry 111 of the NC AP MLD 110 may distribute a block of MSDU payloads to an affiliated STA 113a-c in the NC MLD Lower MAC sublayer 115a- c, as illustrated in figure 4. On receipt of an A-MPDU, the receiving affiliated STA 113a-c may distribute the corresponding MSDU pay load to the peer NC-MLD for processing (in particular via the interfaces 114a-c and 112).

[0129] In an embodiment, on indication of a MPDU reception failure by the receiving affiliated STA, the processing circuitry 111 of the originating NC MLD 110 may distribute the corresponding MSDU pay load, identified by a PN, to another of its affiliated stations 113a-c. When the MSDU payload is distributed to a different affiliated STA 113a-c, the PN assigned for the MSDU payload will remain the same.

[0130] As will be appreciated, by assigning a PN to the MSDU payload in the Upper MAC sublayer 111, the NC AP MLD 110 no longer has to manage block ACK agreements and OTA (over the air) transmission-related errors.

[0131] In an embodiment, the processing circuitry 111 of the NC AP MLD 110 is further configured to add Counter Mode Cipher Block Chaining Message Authentication Code Protocol, CCMP, or Galois Counter Mode Protocol, GCMP, header information to the MSDU payload or the cryptographically encapsulated MSDU payload, wherein the CCMP or GCMP header information comprises the PN. In other words, according to an embodiment, the CCMP or GCMP header will be used, between the NC non-AP MLD 120 and the NC AP MLD 110. At the originating NC MLD 110 the encapsulation header (CCMP or GCMP) may always be present and contain the PN. More specifically, if RSNA is negotiated, the MSDU pay load is cryptographically encapsulated and a GCMP / CCMP header is constructed with all fields are present. The SN is not assigned and is set to 0 in the AAD field for CCMP / GCMP encapsulation. If RSNA was not negotiated, the cryptographic encapsulation header is still present and would contain valid value in only the PN field. In the receiver NC MLD 120, the encapsulation header (CCMP or GCMP) is always present and contains the PN. As will be appreciated, this embodiment allows a CCMP / GCMP header to be added to the MSDU payload prior to the assignment of an SN. This allows cryptographic encapsulation to be decoupled from SN assignment and BA operation, minimizing the interaction between the Upper MAC sublayer 111 of the NC MLD 110 and an affiliated STA 113a-c.

[0132] As already described above, the processing circuitry 111 of the NC AP MLD 110 distributes MSDU payloads to one or more of its affiliated STAs 113a-c for transmission. For increasing traffic reliability, the processing circuitry 111 implementing the Upper MAC sublayer 111 of the NC AP MLD 110 may be configured to distribute the same block of MSDU payloads for transmission to multiple of its affiliated STAs 113a-c for transmission redundancy. The receiving NC MLD 120 or the non-AP MLD 120 that support NC MLD operation may use MSDU payload duplicate detection to reorder the received MSDU pay loads from different affiliated STAs, and remove any duplicates prior to their delivery to the upper layer. The peer NC MLD 120 may process the received MSDU Pay loads using the PN contained in the CCMP / GCMP header, removing any duplicates, and re-ordering if necessary, prior to cryptographic decapsulation.

[0133] Figure 5 shows a schematic diagram illustrating in more detail the NC AP MLD 110 according to an embodiment in communication via the plurality of links 130a, b with the NC non-AP MLD 120 according to an embodiment. As illustrated in figure 5 and already described above, for communication between the Upper MAC sublayer 111 of the NC AP MLD 110 and the multiple remote APs 113a, b the NC AP MLD 110 (as well as the NC non-AP MLD 120) may comprise interfaces 112 and 114a, b. They could be physically separated over a wired or wireless network. The non co-located interfaces (NC i / f) 112 and 114a, b allow the remote (affiliated) AP to be logically / physically separated from the NC AP MLD Upper MAC sublayer 111. The non co-located interfaces (NC-i / f) 122 and 124a, b allow the remote (affiliated) STAs to be logically / physically separated from the NC non-AP MLD Upper MAC sublayer 122.

[0134] Figure 6 illustrates a further embodiment, where the NC AP MLD 110 with its plurality of affiliated APs 113a-c is configured to communicate via the plurality of links 130a-c with the MLD 120 implemented in the form of a co-located MLD 120. In an embodiment, the UHR (Co-located) Non-AP MLD 120 is configured to support the operation of both (Co-located) EHT AP MLD and NC AP MLD.

[0135] Figure 7 provides a summary of the operation of the NC AP MLD 110 and the NC non-AP MLD 120. As illustrated in figure 7, MSDU duplicate detection, replay detection and encryption for individually addressed MSDU payloads occur at the upper MLD level between the MLDs 110, 120, while the MPDU duplicate detection, block ACK agreement, fragmentation / reassembly, encryption for group addressed MSDU payloads and the like, occur at the lower MLD level between the affiliated STAs 113a,b, 123a, b.

[0136] Figure 8 shows a schematic diagram illustrating a frame processing protocol stack 1000 implemented by the processing circuitry 111 of the NC AP MLD 110 according to an embodiment for transmitting or receiving a frame. As already described above, frame processing at the NC MLD Upper MAC sublayer 111 is applied to an MSDU payload. More specifically, frame processing for the transmitting NC MLD Upper MAC sublayer 111 may comprises the following stages:

[0137] • Power save deferred queuing is performed at the NC MLD Upper MAC sublayer 111, similar to Power Save deferred queuing for an MLD .

[0138] • If all the STAs affiliated with the peer non-AP MLD, through which the MPDU(s) corresponding to the MSDU Payload can be received, are in power-save mode, the MSDU payloads are buffered (i.e. not queued) at the NC MLD Upper MAC sublayer.

[0139] • Any MSDU payload that is destined for transmission is assigned a PN.

[0140] • The encapsulation header (CCMP or GCMP) for the MSDU payload is always present and contains the value of a PN.

[0141] • In case of successful RSNA negotiation, the individually addressed MSDU Payload is cryptographically encapsulated.

[0142] • The MSDU payload / encrypted MSDU pay load is distributed to one or more affiliated STAs for transmission. Frame processing for the receiving NC MLD Upper MAC sublayer 121 is as follows:

[0143] • An MSDU payload, associated with a PN, is received by the processing circuitry 111 of the NC MLD 120 from one or more of its affiliated STAs 123a-c.

[0144] • PNs contained in the GCMP / CCMP header are used to re-order the buffers of MSDU Pay loads and are used to perform MSDU pay load duplicate detection across links.

[0145] • If RSNA is negotiated, each individually addressed MSDU payload is cryptographically decapsulated and replay detection is done based on the PN.

[0146] Figure 9 shows a schematic diagram illustrating a frame processing protocol stack 1100 implemented by an affiliated station 113a-c of the NC AP MLD 110 according to an embodiment for transmitting or receiving a frame. As illustrated in figure 9 and already described above, when an MSDU payload is distributed to an affiliated STA 113a-c implementing the NC MLD Lower MAC sublayer 115a-c by the NC MLD Upper MAC sublayer 111, for transmission, the affiliated STA 113a-c performs the following actions:

[0147] • Assigns an SN to an MSDU payload that is not dynamically fragmented.

[0148] • For a dynamically fragmented MSDU payload assign the same SN to each fragmented MSDU Payload and assign a fragment number, FN, for each fragmented MSDU payload.

[0149] • In case of successful RSNA negotiation, the group addressed MSDU Payload is cryptographically encapsulated.

[0150] • Adds an MPDU header with the appropriate affiliated STA addresses (i.e. RA / TAZBSSID) and trailer.

[0151] • Performs MPDU aggregation for MPDUs corresponding to the same TID based on a negotiated block ACK agreement per TID between affiliated STAs.

[0152] • The transmitting affiliated STA, includes the SN in the MPDU header on transmission and retransmission based on existing 802.11 acknowledgment procedures.

[0153] When the affiliated STA 113a-c receives an MPDU, the receiving affiliated STA 113a-c performs the following actions:

[0154] • Follow the existing 802.11 acknowledgment procedures.

[0155] • Reassemble the MSDU payload fragments if necessary.

[0156] • MPDU Duplicate detection.

[0157] • If RSNA is negotiated, each group addressed MSDU pay load is cryptographically decapsulated.

[0158] • Replace the Address 1-4 field with the appropriate MLD DA / SA addresses.

[0159] • The affiliated STA then passes the MSDU payload to the NC MLD.

[0160] In an embodiment, protection for group addressed frames for NC MLO may be handled in the same manner as MLO. For group-addressed frames, per link keys are still required, so PNs are still required at the link level for the group keys. For NC MLO, each affiliated STA has a different set of group keys so cryptographic encapsulation needs to be performed at the affiliated STA. To allow the receiving NC MLD to perform duplicate detection for a group addressed MSDU payload, each affiliated STA will need to use the same PN for cryptographic encapsulation.

[0161] When a group-addressed frame is received from higher layer at the NC MLD, it assigns a PN and creates an MSDU payload. The NC MLD constructs the CCMP / GCMP header including the PN and distributes the frame to all relevant affiliated STAs for transmission. The NC MLD does not cryptographically encapsulate the frame. The affiliated STA assigns an SN and uses the PN to cryptographically encapsulate the frame using a group key. It then transmits the encapsulated frame.

[0162] When an affiliated STA receives a group-addressed frame, it cryptographically decapsulates the frame, uses the SN to perform MPDU duplicate detection, extracts the PN, and sends the group-addressed frame (including the PN) to the NC MLD. The mechanism is consistent with legacy operation so that if an affiliated AP has associated legacy STAs, they are able to receive group-addressed frames.

[0163] In an embodiment, management frame transmissions between MLDs 110, 120, such as Authentication, (Re-)Association, Disassociation, and Deauthentication frames, may use the procedures defined for MSDU Payloads described for previous embodiments. Management frame transmissions between affiliated STAs and affiliated APs may be cryptographically encapsulated when security is negotiated, and transmitted at the affiliated AP layer using conventional mechanisms. During NC MLD association between the non-AP NC MLD 120 and AP NC MLD 120, the peers may mutually derive per-link keys to protect management traffic. The PN and SNs for affiliated STA management frames are processed at the affiliated STA. This embodiment allows management frames to be processed by the affiliated STAs for communication between affiliated STAs and at the NC MLD 110, 120 and affiliated STAs when the management frames are exchanged between NC MLDs 110, 120.

[0164] In an embodiment, a Block ACK agreement will be applied per traffic identifier (TID) and per link on which the affiliated STA link is operating. The Block ACK agreement may be negotiated between peer STAs affiliated with MLD, even for a disabled link. A link is disabled, if no TID is mapped to this link, using either a negotiated or advertised TTLM (TID To link mapping) mechanisms (as defined in 802.1 Ibe specification).

[0165] Block ACK agreements are negotiated between the affiliated STA peers. The starting SN field value setting is link-specific. SN spaces are maintained by each affiliated STA. Scoreboarding is done at the affiliated STA layer.

[0166] Block ACK and (MU) Block ACK Request frames have to be transmitted only on the link to which they apply. For example: The Block ACK frame of Link 1 can’t be transmitted by an affiliated STA operating on Link 2 of the same MLD.

[0167] An NC Agreement parameter may be added to the Block ACK agreement or a new flow for NC Block ACK agreement may be defined, including PN SSN, NC Block ACK window, NC Block ACK timeout. Once the NC MLD is performing the reordering and not the MAC, the “rescue” functionality must be shifted to it. A Block ACK Retry mechanism may be implemented to overcome missing packets. Alternatively, a self-contained working mode may be implemented, in which the receiver continues after missing packets if the Tx exceeds the NC Block ACK window or timeout. This embodiment allows Block ACKs to operate on a per link basis.

[0168] As will be appreciated, embodiments of the NC AP MLD 110 and the NC non-AP MLD 120 disclosed herein implement a new IEEE 802.11 frame processing scheme that relaxes timing constraints between an AP MLD and its affiliated STAs. If facilitates NC MLO. Moreover, NC MLD frame processing is decoupled from affiliated STA processing allowing more flexible deployment. PN processing on MSDUs is assigned to the MLD, while SN processing on MSDUs, aggregation, fragmentation and assembly is assigned to the affiliated STAs. Embodiments disclosed herein allow for the same set of frames to be transmitted and received on multiple links simultaneously.

[0169] Figure 10 shows a flow diagram illustrating steps of a method 1200 for operating an MLD, such as the NC AP MLD 110 with its plurality of affiliated stations 113a-c for communication via the plurality of links 130a-c with the NC non-AP MLD 120 with its plurality of affiliated stations 123a-c. The method 1200 comprises a step 1201 of assigning by the processing circuitry 111 of the MLD 110 a packet number, PN, to a MAC Service Data Unit, MSDU, payload, wherein the MSDU payload comprises a MSDU, an aggregate MSDU, A-MSDU, or a MAC Management Protocol Data Unit, MMPDU, irrespective of whether the MSDU pay load is further cryptographically encapsulated or not.

[0170] In an embodiment, the method 1200 may further comprise cryptographically encapsulating the MSDU pay load and distributing the MSDU pay load or the cryptographically encapsulated MSDU pay load to one or more of the plurality of affiliated stations 113a-c of the NC AP MLD 110. The method 1200 may further comprise assigning by each of the one or more of the plurality of affiliated stations 113a-c of the NC AP MLD 110 a respective SN to the MSDU payload or the cryptographically encapsulated MSDU payload and generating one or more MPDUs based on the MSDU payload or the cryptographically encapsulated MSDU pay load. In an embodiment, the method 1200 may further comprise transmitting the one or more MPDUs to a corresponding further affiliated station of the plurality of further affiliated stations 123a-c of the NC non-AP MLD 120.

[0171] As the method 1200 can be implemented by the NC AP MLD 110 and the NC non-AP MLD 120, further features of the method 1200 result directly from the functionality of the NC AP MLD 110 and the NC non-AP MLD 120 as well as their different embodiments described above and below.

[0172] Figure 11 shows a flow diagram illustrating steps of a method 1300 for operating an MLD, such as the NC non-AP MLD 120 with its plurality of affiliated stations 123a-c for communication via the plurality of links 130a-c with the NC AP MLD 110 with its plurality of affiliated stations 113a-c. The method 1300 comprises the following steps performed by an affiliated station 123a-c: receiving 1301 one or more MAC Protocol Data Units, MPDUs, from a corresponding further affiliated station of the plurality of further affiliated stations 113a-c of the NC AP MLD 110; and deriving 1303 a MSDU pay load or a cryptographically encapsulated MSDU pay load from the one or more MPDUs.

[0173] The method 1300 further comprises the following steps performed by the NC non-AP MLD 120: receiving 1305 from one more of the plurality of affiliated stations 123a-c the MSDU payload orthe cryptographically encapsulated MSDU pay load; extracting 1307 a packet number, PN, from the MSDU pay load or the cryptographically encapsulated MSDU pay load; and verifying 1309 based on the extracted PN whether the MSDU payload orthe cryptographically encapsulated MSDU payload is a duplicate.

[0174] As the method 1300 can be implemented by the NC non-AP MLD 120 and the NC AP MLD 110, further features of the method 1300 result directly from the functionality of the NC non-AP MLD 120 and the NC AP MLD 110 as well as their different embodiments described above and below. The person skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step). In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely logical function division and may be another division in an actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

[0175] The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments. In addition, functional units in the embodiments of the disclosure may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.

Claims

CLAIMS1. A Multi-Link Device, MLD, (110) with a plurality of affiliated stations (113a-c) for communication via a plurality of links (130a-c) with a further MLD (120) with a plurality of further affiliated stations (123a-c), wherein the MLD (110) comprises processing circuitry (111) configured to: assign a packet number, PN, to a MAC Service Data Unit, MSDU, payload, wherein the MSDU payload comprises a MSDU, an aggregate MSDU, A-MSDU, or a MAC Management Protocol Data Unit, MMPDU, irrespective of whether the MSDU pay load is further cryptographically encapsulated or not.

2. The MLD (110) of claim 1, wherein the processing circuitry (111) is further configured to cryptographically encapsulate the MSDU payload.

3. The MLD (110) of claim 1 or 2, wherein the MLD (110) further comprises a communication interface (112) configured to distribute the MSDU payload or the cryptographically encapsulated MSDU payload to one or more of the plurality of affiliated stations (113a-c); wherein each of the one or more of the plurality of affiliated stations (113a-c) is configured to assign a respective sequence number, SN, to the MSDU payload or the cryptographically encapsulated MSDU payload and to generate one or more MPDUs based on the MSDU pay load or the cryptographically encapsulated MSDU pay load.

4. The MLD (110) of claim 3, wherein each of the one or more of the plurality of affiliated stations (113a-c) is further configured to transmit the one or more MPDUs to a corresponding further affiliated station of the plurality of further affiliated stations (123a-c) of the further MLD (120).

5. The MLD (110) of claim 4, wherein, in case of a MPDU(s) reception failure, the communication interface (112) of the MLD ( 110) is configured to distribute the MSDU payload or the cryptographically encapsulated MSDU payload to one or more other affiliated stations of the plurality of affiliated stations (113a-c), wherein each of the one or more other affiliated stations of the plurality of affiliated stations (113a-c) is configured to generate, based on the MSDU pay load or the cryptographically encapsulated MSDU pay load, one or more further MAC Protocol Data Units, MPDUs, to assign a respective SN to the one or more further MPDU s and to transmit the one or more further MPDU s to one or more of the plurality of further affiliated stations (123a-c) of the further MLD (120).

6. The MLD (110) of claim 4 or 5, wherein each of the one or more of the plurality of affiliated stations (113a-c) is further configured to setup a Block ACK agreement for each TID with the corresponding further affiliated station in order to transmit A-MPDU and receive a Block Ack frame from the corresponding further affiliated station of the plurality of further affiliated stations (123a-c) of the further MLD (120) and to maintain a scoreboard indicative of the successfully and unsuccessfully transmitted one or more MPDUs, wherein each of the one or more of the plurality of affiliated stations (113a-c) is further configured to perform a retransmission of any unsuccessfully transmitted MPDUs based on the scoreboard for the corresponding link (130a-c).

7. The MLD (110) of claim 6, wherein the Block Ack frame comprises the SNs of the successfully and unsuccessfully transmitted one or more MPDUs.

8. The MLD (110) of claim any one of claims 4 to 7, wherein each of the plurality of affiliated stations (113a-c) is further configured to encrypt at least a respective portion of the one or more MPDUs with one or more per-link encryption keys and to transmit the one or more at least partially encrypted MPDUs to the corresponding further affiliated station of the plurality of further affiliated stations (123a-c) of the further MLD (120).

9. The MLD (110) of any one of claims 3 to 8, wherein each of the plurality of affiliated stations (113a-c) is configured to implement a protocol stack including a lower MAC layer (115a-c), wherein the lower MAC layer (115a-c) is configured to assign the respective SN to the one or more MPDUs.

10. The MLD (110) of any one of the preceding claims, wherein the processing circuitry (111) of the MLD (110) is configured to implement a protocol stack including an upper MAC layer, wherein the upper MAC layer is configured to assign the PN to the MSDU payload.

11. A method (1200) of operating a Multi-Link Device, MLD, (110) with a plurality of affiliated stations (113a-c) for communication via a plurality of links (130a-c) with a further MLD (120) with a plurality of further affiliated stations (123a- c), wherein the MLD (110) comprises processing circuitry (111) and wherein the method (1200) comprises: assigning (1201) by the processing circuitry (111) of the MLD (110) a packet number, PN, to a MAC Service Data Unit, MSDU, payload, wherein the MSDU payload comprises a MSDU, an aggregate MSDU, A-MSDU, or a MAC Management Protocol Data Unit, MMPDU, irrespective of whether the MSDU payload is further cryptographically encapsulated or not.

12. A Multi-Link Device, MLD, (120) with a plurality of affiliated stations (123a-c) for communication via a plurality of links (130a-c) with a further MLD (110) with a plurality of further affiliated stations (113a-c), wherein each affiliated station (123a-c) is configured to: receive one or more MAC Protocol Data Units, MPDUs, from a corresponding further affiliated station of the plurality of further affiliated stations (113a-c); and derive a MSDU payload or a cryptographically encapsulated MSDU pay load from the one or more MPDUs; wherein the MLD (120) comprises a communication interface (122) configured to receive from one more of the plurality of affiliated stations (123a-c) the MSDU payload or the cryptographically encapsulated MSDU payload, wherein the MLD (120) further comprises processing circuitry (121) configured to extract a packet number, PN, from the MSDU payload or the cryptographically encapsulated MSDU payload and to verily, based on the extracted PN, whether the MSDU payload or the cryptographically encapsulated MSDU pay load is a duplicate.

13. The MLD (120) of claim 12, wherein each affiliated station (123a-c) is configured to extract a sequence number, SN, from each of the one or more MPDUs and to determine, based on the respective SN, whether the respective MPDU is a duplication.

14. The MLD (120) of claim 12 or 13, wherein each affiliated station (123a-c) is further configured to maintain a Block ACK agreement for each TID with the corresponding further affiliated station (i.e. that is operating on the same link and has initiated the Block ACK agreement for each TID) in order to respond with a Block Ack frame to the corresponding furtheraffiliated STA of the plurality of further affiliated stations (113a-c) of the further MLD (110) for maintaining a scoreboard indicative of the successfully and unsuccessfully transmitted one or more MPDUs in the initiating further affiliated STA.

15. A method (1300) of operating a Multi-Link Device, MLD, (120) with a plurality of affiliated stations (123a-c) for communication via a plurality of links (130a-c) with a further MLD (110) with a plurality of further affiliated stations (113a- c), wherein the method (1300) comprises the following steps performed by an affiliated station (123a-c): receiving (1301) one or more MAC Protocol Data Units, MPDUs, from a corresponding further affiliated station of the plurality of further affiliated stations (113a-c) of the further MLD (110); and deriving (1303) anMSDU pay load or a cryptographically encapsulated MSDU pay load from the one or more MPDUs; wherein the method (1300) further comprises the following steps performed by the MLD (120): receiving (1305) from one more of the plurality of affiliated stations (123a-c) the MSDU payload or the cryptographically encapsulated MSDU payload; extracting (1307) a packet number, PN, from the MSDU pay load or the cryptographically encapsulated MSDU payload; and verifying (1309) based on the extracted PN whether the MSDU payload or the cryptographically encapsulated MSDU pay load is a duplicate.

Images