WO2022266876A1

WO2022266876A1 - Indication of sequence number for groupcast frame

Info

Publication number: WO2022266876A1
Application number: PCT/CN2021/101793
Authority: WO
Inventors: Mika Kasslin; Zhijie Yang; Lorenzo GALATI GIORDANO
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2021-06-23
Filing date: 2021-06-23
Publication date: 2022-12-29
Also published as: CN117561730A

Abstract

Embodiments of the present disclosure relate to indication of sequence number for groupcast frame. A device generates information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to a second device; and transmit the information in a second available link to the second device. Based on the information, the second device performs a transition from the second available link to a first available link in the set of first available links. In this way, sequence numbers of the last groupcast frames on links may be indicated and a smooth transition among the links may be achieved.

Description

INDICATION OF SEQUENCE NUMBER FOR GROUPCAST FRAME

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication and, in particular, to a method, device and computer readable storage medium of communication among multi-link devices (MLDs) .

BACKGROUND

With the development of Wi-Fi 7, a multi-link (ML) is defined according to which an access point (AP) or a non-AP station (STA) that supports 802.11be multi-link can simultaneously manage multiple links working on different channels. A multi-link capable device is called MLD, a multi-link AP is called AP MLD and a multi-link non-AP STA is called non-AP MLD. An AP MLD and a non-AP MLD may establish multiple links which may operate simultaneously.

Per decisions made by IEEE 802.11 working group TGbe, groupcast frames may be duplicated on all links on AP MLD side so that non-AP MLD may receive them on any one of the links. The non-AP MLD may start experiencing problems with the current link such as weak signal level, increased occupancy level, collisions due to e.g. hidden STAs, increased interference, etc. and may want to select another available link to receive groupcast frames. Thus, it may be desirable to know how to transition from one available link to another available link without missing any groupcast frames.

SUMMARY

In general, example embodiments of the present disclosure provide an improved solution for a transition among links between an AP MLD and a non-AP MLD.

In a first aspect, there is provided a device. The device comprises: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the device to: generate information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the device to a second device; and transmit the information in a second available link to the second device.

In a second aspect, there is provided a device. The device comprises: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the device to: receive, from another device and in a second available link, information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the other device to the device; and perform, based on the information, a transition from the second available link to a first available link in the set of first available links.

In a third aspect, there is provided a method of communication. The method comprises: generating, at a first device, information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to a second device.

In a fourth aspect, there is provided a method of communication. The method comprises: receiving, at a second device and from a first device, information regarding a set of sequence numbers in a second available link carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to the second device; and performing, based on the information, a transition from the second available link to a first available link in the set of first available links.

In a fifth aspect, there is provided an apparatus of communication. The apparatus comprises: a first device having: means for generating, at a first device, information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to a second device; and means for transmitting the information in a second available link to the second device.

In a sixth aspect, there is provided an apparatus of communication. The apparatus comprises: a first device having: means for receiving from a second device, information regarding a set of sequence numbers in a second available link, the set of sequence numbers being carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to the second device; and means for performing, based on the information, a transition from the second available link to a first available link in the set of first available links.

In a seventh aspect, there is provided a non-transitory computer readable medium. The non-transitory computer readable medium comprises program instructions for causing an apparatus to perform the method according to the third aspect.

In an eighth aspect, there is provided a non-transitory computer readable medium. The non-transitory computer readable medium comprises program instructions for causing an apparatus to perform the method according to the fourth aspect.

It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings, where:

Fig. 1 illustrates an example communication network in which example embodiments of the present disclosure may be implemented;

Fig. 2A illustrates a diagram of a Sequence Control field according to some embodiments of the present disclosure;

Fig. 2B illustrates a diagram of a medium access control (MAC) header according to some embodiments of the present disclosure;

Fig. 3 illustrates a diagram of transmission of groupcast frames on links according to some embodiments of the present disclosure;

Fig. 4 illustrates a flowchart illustrating a process of communication according to some embodiments of the present disclosure;

Fig. 5 illustrates a diagram of a Reduced Neighbor Report element according to some embodiments of the present disclosure;

Fig. 6 illustrates a diagram of a Multi-Link element according to some embodiments of the present disclosure;

Fig. 7 illustrates a diagram of a link transition according to some embodiments of the present disclosure;

Fig. 8 illustrates a flowchart of a method of communication implemented at a first device according to example embodiments of the present disclosure;

Fig. 9 illustrates a flowchart of a method of communication implemented at a second device according to example embodiments of the present disclosure;

Fig. 10 illustrates a simplified block diagram of an apparatus that is suitable for implementing example embodiments of the present disclosure; and

Fig. 11 illustrates a block diagram of an example computer readable medium in accordance with example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and to help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as, but not limited to, fifth generation (5G) systems, Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) , WiFi and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) new radio (NR) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR NB (also referred to as a gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology. A RAN split architecture comprises a gNB-CU (Centralized unit, hosting RRC, SDAP and PDCP) controlling a plurality of gNB-DUs (Distributed unit, hosting RLC, MAC and PHY) . A relay node may correspond to DU part of the IAB node.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. The terminal device may also correspond to Mobile Termination (MT) part of the integrated access and backhaul (IAB) node (a.k.a. a relay node) . In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

IEEE 802.11 working group has task group TGbe developing the next major PHY&MAC release of the 802.11 specification which is going to be defined in the 802.11be amendment and which is expected to be the basis of Wi-Fi 7. One of the main features defined by the TGbe is multi-link according to which an AP or a non-AP STA that supports 802.11be multi-link can simultaneously manage multiple links working on different channels.

As mentioned above, an AP MLD and a non-AP MLD may establish multiple links which may operate simultaneously. Groupcast frames may be duplicated on all links on AP MLD side so that non-AP MLD may receive them on any one of the links. The non-AP MLD may start experiencing problems with the current link such as weak signal level, increased occupancy level, collisions due to e.g. hidden STAs, increased interference, etc. and may want to select another available link to receive groupcast frames. However, the non-AP MLD does not know how far the other APs have proceeded in a sequence number space applied to the groupcast frames and thus does not know which of the other available links would be such that the non-AP MLD would not miss any groupcast frames in the transition to the new link.

In order to solve the above and other potential problems, embodiments of the present disclosure provide an improved solution. In the solution, an AP MLD indicates, with a transmission in current link to a non-AP MLD, information regarding a sequence number carried in the last groupcast frame transmitted in another available link. The non-AP MLD receives the information on the current link and uses the information to determine which of the other available links could be used to receive groupcast frames without missing any groupcast frames. In this way, a smooth link transition may be facilitated. Principles and implementations of the present disclosure will be described in detail below with reference to the figures.

EXAMPLE OF COMMUNICATION NETWORK

Fig. 1 illustrates an example communication system 100 in which embodiments of the present disclosure can be implemented. As shown in Fig. 1, the system 100 includes a first device 110 and a second device 120. In this example, the first device 110 is an AP MLD, and the second device 120 is a non-AP MLD. The first device 110 has

APs

111, 112 and 113, and the second device 120 has STAs 121, 122 and 123.

A link 131 is established between AP 111 and STA 121, a link 132 is established between AP 112 and STA 122, and a link 133 is established between AP 113 and STA 123. In this example, all the

links

131, 132 and 133 are enabled, in other words, all the

links

131, 132 and 133 are available. In some alternative embodiments, only a part of the

links

131, 132 and 133 may be enabled. The

links

131, 132 and 133 may operate in different frequency bands. For example, the link 131 operates in 2.4GHz, the link 132 operates in 5GHz, and the link 133 operates in 6GHz. This is merely an example, any other suitable frequency band is also feasible. Of course, a part or all of these links may also operate in the same frequency band.

It is to be understood that the number of first and second devices as shown in Fig. 1 is only for the purpose of illustration without suggesting any limitations. The system 100 may include any suitable number of first and second devices adapted for implementing embodiments of the present disclosure. It is also to be understood that the number of APs in the first device, the number of STAs in the second device and the number of links as shown in Fig. 1 is only for the purpose of illustration without suggesting any limitations. The system 100 may include any suitable number of APs and STAs in the first and second devices and any suitable number of links among the APs and STAs adapted for implementing embodiments of the present disclosure.

Merely for illustration purpose and without suggesting any limitations as to the scope of the present disclosure, some embodiments will be described in the context where the first device 110 is an AP MLD and the second device 120 is a non-AP MLD. It is to be understood that, in other embodiments, the first device 110 may be a non-AP MLD and the second device 120 may be an AP MLD.

As shown in Fig. 1, the first device 110 and the second device 120 may communicate with each other. The first device 110 may have multiple antennas for communication with the second device 120. The second device 120 may also have multiple antennas for communication with the first device 110. It is to be understood that each of the first device 110 and the second device 120 may provide any suitable number of antennas adapted for implementing embodiments of the present disclosure.

The communications in the system 100 may conform to any suitable standards for wireless local area network or a cellular network, including, but not limited to, Wi-Fi, LTE, LTE-evolution, LTE-advanced (LTE-A) , wideband code division multiple access (WCDMA) , code division multiple access (CDMA) and global system for mobile communications (GSM) and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, Wi-Fi 7, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) , 5G-advanced, and the sixth generation (6G) communication protocols.

In some scenarios, the first device 110 may duplicate groupcast frames such as group addressed data frames on all of the

links

131, 132 and 133 so that the second device 120 may receive them on any one of the

links

131, 132 and 133.

Duplicate frame detection and recovery is one of the basic procedures specified in the 802.11 specification to deal with frames which may be received more than once. It is desired to filter out these duplicates. Duplicate frame filtering is facilitated through the inclusion of a Sequence Control field within Data, Management, and Extension frames. Fig. 2A illustrates a diagram of a Sequence Control field 200A according to some embodiments of the present disclosure. As shown in Fig. 2A, the Sequence Control field 200A may consist of a fragment number 210 and a sequence number 220. Fig. 2B illustrates a diagram of a MAC header 200B according to some embodiments of the present disclosure. As shown in Fig. 2B, Each of the Data, Management, and Extension frames may have a Sequence Control field 230 in the MAC header 200B. The Sequence Control field 230 may be implemented in a manner as shown in Sequence Control field 200A. Of course, any other suitable manners are also feasible.

A STA may maintain one or more sequence number spaces that are used when transmitting a frame to determine the sequence number for the frame. When multiple sequence number spaces are supported, the appropriate sequence number space may be determined by information from the Sequence Control field in the MAC header of the frame to be transmitted. Each sequence number space may be represented by a modulo 4096 counter, starting at 0 and incrementing by 1, for each MAC service data unit (MSDU) or MAC management protocol data unit (MMPDU) transmitted using that sequence number space.

Currently, the 802.11 specification requires a baseline sequence number space as shown in Table 1 below to be used when transmitting groupcast frames. The multi-link operations which are currently under development in TGbe are expected to change the duplicate frame detection and recovery procedure and specifically the requirements and rules related to the sequence number spaces. The changes are currently planned for individually addressed frames for which MLD level sequence number spaces are proposed.

Table 1 An example of baseline sequence number space

No changes are currently planned to use of sequence number space applied to groupcast frames but the baseline sequence number space is still assumed in the latest 802.11be draft, D1.0, which was released in May 2021. The TGbe has been, however, discussing proposals to apply MLD level sequence number space also with groupcast frames.

Should the TGbe decide to apply MLD level sequence number space as shown in Table 2 below to groupcast frames transmitted without any changes to the approach of duplicating groupcast frames to all available links, an AP MLD ends up transmitting groupcast frames in all its links with the sequence number subfield indicating the value which may be used as the unique identifier of the groupcast frame transmitted by the AP MLD.

Table 2 An example of MLD level sequence number space

Each STA of a non-AP MLD that is operating on an available link maintains its own power management mode and power state as specified in the IEEE 802.11 specification. There is no MLD level power management scheme, but power management mode and power state transitions are on the link level and taken care of by the STAs/APs of the MLDs. No interconnections between links in terms of power management mode or power state transitions but links are independent from this perspective, and an AP of an AP MLD serves non-AP STAs from power saving perspective as if they were legacy STAs. On the other hand, a non-AP MLD is not expected to monitor Beacon frames in all the links, but it is enough to receive Beacon frames in one link only for e.g. traffic indication message (TIM) field reception and to determine whether there are frames buffered in the AP MLD targeted to the non-AP MLD.

Groupcast frame duplicates transmitted in different links of an AP MLD carry the same sequence number value in the Sequence Control field. However, each AP of the AP MLD transmits the groupcast frames independently and asynchronously. That means that the latest sequence numbers of groupcast frames transmitted by the APs are expected to differ by at least a bit. Each AP has its own timing related e.g. to Beacon frame transmission and timing synchronization function (TSF) and has its own capability, and all APs operate in different channels which have different channel conditions and occupancy levels. All these are expected to have an impact on timing of individual groupcast frame duplicate transmissions. An example of this is illustrated in Figure 3.

Fig. 3 illustrates a diagram of transmission 300 of groupcast frames on links according to some embodiments of the present disclosure. For convenience, Fig. 3 will be described in connection with the example of Fig. 1. In this example, a case in which groupcast frames are transmitted in all three links is described. As shown in Fig. 3, the link 131 starts with a sequence number equal to ‘5’ and the last frame illustrated in the link 131 has a sequence number equal to ‘8’ . The link 132 starts with a sequence number equal to ‘3’ and the last frame illustrated in the link 132 has a sequence number equal to ‘7’ . The link 133 starts with a sequence number equal to ‘6’ and the last frame illustrated in the link 133 has a sequence number equal to ‘9’ . It can be seen that timings of individual groupcast frame duplicate transmissions may be different.

MLD-level sequence numbers also on groupcast frames makes it possible for a non-AP MLD to detect duplicate groupcast frames and identify possibly missing frames. This works all fine as long as the link it uses to receive groupcast frames works properly. However, if the non-AP MLD starts experiencing problems with the current link, such as for example weak signal level, increased occupancy level, collisions due to e.g. hidden STAs, increased interference, etc., the non-AP MLD may want to select another available link to receive groupcast frames. The non-AP MLD should be able to move from one available link to another available link without missing any groupcast frames. However, the non-AP MLD does not know how far the other APs have proceeded in the sequence number space applied to the groupcast frames and thus does not know which of the other available links would be such that the non-AP MLD would not miss any groupcast frames in the transition to the new link.

With reference to Fig. 3, assuming that the second device 120 uses originally the link 131 to receive groupcast frames. At time point t1, the second device 120 would like to start using one of the two other

available links

132 and 133 to receive groupcast frames.

According to the features and procedures specified in 802.11 or proposed for 802.11be, a non-AP MLD does not have a knowledge on how far the other APs have proceeded in the sequence number space applied to the groupcast frames and thus does not know which of the other available links would be such that the non-AP MLD would not miss any groupcast frames in the transition to the new link. The non-AP MLD needs to perform reassociation when performing basic service set (BSS) transition and for that case there is no support for detection of duplicate or missing groupcast frames in BSS transition.

Embodiments of the present disclosure provide an improved solution. In the solution, the first device 110 indicates, in the current link 131 to the second device 120, information regarding sequence numbers carried in the last groupcast frames transmitted in other

available links

132 and 133. Thus, at time point t1, the second device 120 may know that link 132 is the link which runs with a smaller sequence number than the current link 131, and may select the link 132 as the new link. In this way, it can be ensured that any groupcast frames is not missed. The solution will be described below with reference to Fig. 4. Herein, the term “last” as used in conjunction with the groupcast frames refers to the most recent groupcast frames that were transmitted in the other available links, prior to a time point at which the current link is to be switched.

EXAMPLE IMPLEMENTATION OF INDICATION OF SEQUENCE NUMBER

Fig. 4 illustrates a flowchart illustrating a process 400 of communication according to some embodiments of the present disclosure. For the purpose of discussion, the process 400 will be described with reference to Fig. 1 and Fig. 3. The process 400 may involve the first and

second devices

110 and 120 as illustrated in Fig. 1. It would be appreciated hat although the process 400 has been described in the communication system 100 of Fig. 1, this process may be likewise applied to other communication scenarios. For convenience, the current link is also referred to as a second available link herein, and other link is also referred to as a first available link herein. In this example, assuming that all the

links

131, 132 and 133 are available links and the current link is the link 131.

As shown in Fig. 4, the first device 110 generates 410 information regarding a set of sequence numbers, the sequence numbers being carried in the last groupcast frames transmitted in a set of first available links (for example, the links 132 and 133) from the first device 110 to the second device 120. For example, in the time point t1 as shown in Fig. 3, the last groupcast frame in the link 132 has a sequence number equal to ‘4’ , and the last groupcast frame in the link 133 has a sequence number equal to ‘7’ . In this case, the first device 110 may generate information regarding sequence number “4” in the link 132 and sequence number “7” in the link 133.

In some embodiments, the first device 110 may generate the set of sequence numbers as the information. A sequence number in the set of sequence numbers may be assigned from a sequence number space common for all the links. For example, the sequence numbers may be assigned from the sequence number space as shown in Table 2. It is to be noted that any other suitable sequence number spaces existing or future developed are also feasible, and the present disclosure does not limit this aspect.

In some alternative embodiments, the first device 110 may generate an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link. In some embodiments, the first device 110 may generate the offset based on an equation (1) below.

ΔSNS _[L1-L2] = SNS _[L1] -SNS _[L2] (1)

where ΔSNS _[L1-L2] denotes the offset (also referred to as delta sequence number space (SNS) herein) between the first available link and the second available link, SNS _[L1] denotes the latest SNS of groupcast frame in the first available link, and SNS _[L2] denotes the latest SNS of groupcast frame in the second available link. In some embodiments, ΔSNS _[L1-L2] may be a negative or positive value. In some embodiments, ΔSNS _[L1-L2] may be set to FFF if indicating an unavailable value.

For example, in the time point t1 as shown in Fig. 3, the last groupcast frame in the link 131 has a sequence number equal to ‘6’ , the last groupcast frame in the link 132 has a sequence number equal to ‘4’ , and the last groupcast frame in the link 133 has a sequence number equal to ‘7’ . In this case, the first device 110 may generate an offset of sequence number of the last groupcast frame in the link 132 with respect to that in the link 131 as ‘-2’ , and an offset of sequence number of the last groupcast frame in the link 133 with respect to that in the link 131 as ‘1’ .

It is to be noted that the above examples are merely for illustration, any other suitable ways are also feasible to indicate a sequence number carried in the last groupcast frame transmitted in the first available link.

Returning to Fig. 4, upon generation of the information, the first device 110 transmits 420 the information to the second device 120. In some embodiments, the first device 110 may transmit the information in a beacon frame. In some embodiments, the first device 110 may transmit the information in a reassociation response frame or an association response frame. In some embodiments, the first device 110 may transmit the information in a probe response frame or a ML probe response frame. Of course, any other suitable control frames may also be used for transmitting the information, and the present disclosure does not limit this aspect.

The latest 802.11be draft (802.11be D1.0) specifies novel signaling means to support multi-link operations. The draft specifies extensions to elements and sub-elements defined in the 802.11 specification including, as an example, a Reduced Neighbor Report element. Thus, in some embodiments, the first device 110 may cause the information to be comprised in the Reduced Neighbor Report element. In some embodiments, an AP of the first device 110 may be allowed to carry information related to the other APs of the first device 110 in the target beacon transmission time (TBTT) information field that may be carried in a Neighbor AP Information field of the Reduced Neighbor Report element. In some embodiments, the first device 110 may cause the information to be comprised in a MLD Parameters subfield of the Reduced Neighbor Report element.

Fig. 5 illustrates a diagram of a Reduced Neighbor Report element 500 according to some embodiments of the present disclosure. As shown in Fig. 5, the Reduced Neighbor Report element 500 may comprise a neighbor AP Information field 501. The Neighbor AP Information field 501 may comprise a TBTT Information Set subfield 511. The TBTT Information Set subfield 511 may comprise a MLD Parameters subfield 521. For example, the MLD Parameters subfield 521 may be extended to include a new subfield (denoted as a Sequence Number subfield 531 for convenience) to indicate the information regarding the sequence number.

In some embodiments, the Reduced Neighbor Report element may be carried in a beacon frame. In some embodiments, the Reduced Neighbor Report element may be carried in a probe response frame. In this way, an AP of the first device 110 may indicate, with the Reduced Neighbor Report element, information related to other APs of the first device 110. Such information may contain, as an example, the sequence number used by the other APs in their groupcast frame transmissions. In some additional or alternative embodiments, a new request/response protocol may be specified for use between the first device 110 and the second device 120. Such a new protocol may be built upon use of Action frames with which a non-AP MLD or an affiliated STA could request the AP MLD or the affiliated AP to provide up to date information about the sequence number used by the APs of the AP MLD in their groupcast frame transmissions.

The latest 802.11be draft (802.11be D1.0) also specifies, as an example, a new Multi-Link element which is designed to be used in discovery of an AP MLD and in multi-link (re) setup. Thus, in some alternative embodiments, the first device 110 may cause the information to be comprised in the Multi-Link element. In some embodiments, the first device 110 may cause the information to be comprised in an extended subfield in a Per-STA profile subelement of the Multi-Link element, and cause an indication to be comprised in a STA Control subfield of the Per-STA profile subelement, the indication indicating a presence of the extended subfield.

Fig. 6 illustrates a diagram of a Multi-Link element 600 according to some embodiments of the present disclosure. As shown in Fig. 6, the Multi-Link element 600 may comprise a Link Info field 601. The Link Info field 601 may comprise a Per-STA profile subelement (for example, Per-STA profile x) 611. For example, the Per-STA profile subelement 611 may be extended to include a new subfield (not shown) to indicate the information regarding the sequence number. In some embodiments, the extended subfield may be included in a STA Info field 621 of the Per-STA profile subelement 611.

The Per-STA profile subelement 611 may comprise a STA Control subfield 631. For example, one of the Reserved bits 641 of the STA Control subfield 631 may be specified for use to indicate whether the extended subfield is present in the STA Info field 621. The new bit in the STA Control subfield 631 may be called Sequence NumberPresent subfield (or Delta SNS Present subfield) . In some embodiments, the bit may be set to 1 if the Sequence Number subfield (or Delta SNS subfield) is present in the STA Info field 621. Otherwise, the bit would be set to 0. The Sequence Numbersubfield (or Delta SNS subfield) may be similar 12-bit subfield 531 as illustrated in Figure 5.

In some embodiments, the Per-STA profile subelement may be carried in a beacon frame. In some embodiments, the Per-STA profile subelement may be carried in a probe response frame or a ML probe response frame. In this way, an AP of the first device 110 may indicate, with the Per-STA profile subelement, information related to other APs of the first device 110.

Although the above description is made on the information regarding the set of sequence numbers is transmitted in Reduced Neighbor Report element or Multi-Link element, the information also may be transmitted in any other suitable elements existing or to be developed. The present disclosure does not limit this aspect.

In some alternative embodiments, the first device 110 may transmit the information in an action frame without a Reduced Neighbor Report element or a Multi-Link element. In some alternative embodiments, the first device 110 may transmit the information in an aggregated control (A-control) field of a frame without a Reduced Neighbor Report element or a Multi-Link element.

EXAMPLE IMPLEMENTATION OF LINK TRANSITION

Still with reference to Fig. 4, upon receipt of the information regarding the set of sequence numbers from the second available link (for example, the link 131) , the second device 120 performs 430 a transition from the second available link to a first available link (for example, the link 132 or 133) in the set of first available links based on the information.

In some embodiments, the second device 120 may determine 431 a target link in the set of first available links. In some embodiments, the second device 120 may determine a candidate link in the set of first available links so that no groupcast frame is missed. For example, the second device 120 may select, as the candidate link, a link in which the last groupcast frame has a sequence number lower than that in the current link. If a channel of the candidate link is available, the second device 120 may determine the candidate link as the target link. If the channel of the candidate link is unavailable, the second device 120 may select a further link in the set of first available links as the target link. This will be described in detail with reference to Fig. 7.

Fig. 7 illustrates a diagram of a link transition 700 according to some embodiments of the present disclosure. For convenience, this example is described with reference to Fig. 1. In this example, the

links

131, 132 and 133 are available, and the second device 120 uses the link 131 to receive groupcast frames transmitted by the first device 110. The second device 120 keeps on receiving Beacon frames from the AP 111 corresponding to the link 131. Since the AP 111 causes the information regarding the set of sequence numbers to be comprised in the frames, the second device 120 (for example, the STA 121 corresponding to the link 131) is aware of the sequence numbers used for groupcast frames transmissions by all the APs of the first device 110.

When the second device 120 decides to select one of the other available links for use in groupcast frame transmission, the second device 120 may prefer the links that run behind in the sequence number space to avoid missing any groupcast frames. As shown in Fig. 7, the second device 120 wishes to change the groupcast link at time point t1 and then selects the link 132 so as not to miss any groupcast frames. If the link 132 is not proper e.g. due to low signal level in receive or channel occupancy, the second device 120 may select another proper link (for example, the link 133) as the target link.

Upon determination of the target link, the second device 120 may perform 432 the transition from the second available link to the target link. In some embodiments, if a sequence number carried in the last groupcast frames transmitted in the target link is equal to or smaller than a further sequence number carried in the last groupcast frame transmitted in the second available link, the second device 120 may receive groupcast frames on the target link while stopping receiving groupcast frames on the second available link.

With reference to Fig. 7, the second device 120 wishes to change the groupcast link at time point t1 and determines the link 132 as the target link. Since the last groupcast frame in the link 132 has a sequence number equal to ‘4’ that is lower than the sequence number ‘6’ of the last groupcast frame in the link 131, the second device 120 may directly transition from the link 131 to the link 132 at time point t1. That is, the second device 120 may start receiving groupcast frames on the link 132 while stopping receiving groupcast frames on the link 131.

In some embodiments, if the sequence number carried in the last groupcast frames transmitted in the target link is larger than the further sequence number carried in the last groupcast frame transmitted in the second available link, the second device 120 may receive groupcast frames on both the target link and the second available link. When a groupcast frame transmitted with the highest sequence number that is missed on the target link is received on the second available link, the second device 120 may stop receiving groupcast frames on the second available link.

With reference to Fig. 7, the second device 120 wishes to change the groupcast link at time point t1 and determines the link 133 as the target link. Since the last groupcast frame in the link 133 has a sequence number equal to ‘7’ that is larger than the sequence number ‘6’ of the last groupcast frame in the link 131, the second device 120 may receive groupcast frames both on the link 131 and the link 133 in parallel until the second device 120 has received in the “old link” (i.e., the link 131) those groupcast frames which were transmitted in the “new link” (i.e., the link 133) before the transition (i.e., before the time point t1) .

In other words, the second device 120 may receive groupcast frames both on the link 131 and the link 133 in parallel until the second device 120 receives the groupcast frame transmitted with the highest sequence number (i.e., sequence number ‘7’ ) that was missed in the link 133 ( “new link” ) . As shown in Fig. 7, the second device 120 may receive groupcast frames on both the link 131 and the link 133 from time point t1 until time point t2. After that, the second device 120 may discontinue receiving groupcast frames on the link 131 and continue on the link 133 only.

It is to be noted that the above example is merely for illustration, and the link transition may be implemented in any other suitable ways based on the information regarding the set of sequence numbers. With the process of Fig. 4, information of sequence numbers carried in the last groupcast frames transmitted in other available links is indicated on the current link and a smooth link transition may be facilitated.

EXAMPLE IMPLEMENTATION OF METHODS

Corresponding to the above process, some example embodiments of the present disclosure will now be described in detail with reference to the figures. However, those skilled in the art would readily appreciate that the detailed description given herein with respect to these figures is for explanatory purpose as the present disclosure extends beyond theses limited embodiments.

Fig. 8 illustrates a flowchart of a method 800 of communication implemented at a first device according to example embodiments of the present disclosure. The method 800 can be implemented at the first device 110 shown in Fig. 1. For the purpose of discussion, the method 800 will be described with reference to Fig. 1. It is to be understood that method 800 may further include additional blocks not shown and/or omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

As shown in Fig. 8, at block 810, the first device 110 generates information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links (for example, the

links

132 and 133 in Fig. 1) from the first device 110 to the second device 120.

In some embodiments, the first device 110 may generate, as the information, an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link. In some embodiments, the first device 110 may generate the set of sequence numbers as the information, a sequence number in the set of sequence numbers being assigned from a sequence number space common for the set of first available links and the second available link.

At block 820, the first device 110 transmits the information in a second available link (for example, the link 132 in Fig. 1) to the second device 120. In some embodiments, the first device 110 may transmit the information in at least one of a beacon frame, a reassociation response frame, an association response frame, a probe response frame or a ML probe response frame.

In some embodiments, the first device 110 may transmit the information by at least one of the following: causing the information to be comprised in a reduced neighbor report element; or causing the information to be comprised in a multi-link element. In some embodiments, the first device 110 may cause the information to be comprised in a multi-link device parameters subfield of the reduced neighbor report element. In some embodiments, the first device 110 may cause the information to be comprised in an extended subfield in a per-station subelement of the multi-link element, and cause an indication to be comprised in a station control subfield of the per-station subelement, the indication indicating a presence of the extended subfield.

In some embodiments, the first device 110 may transmit the information in at least one of an action frame or an aggregated control field of a frame without a Reduced Neighbor Report element or a Multi-Link element.

The operations in the method of Fig. 8 correspond to that in the process described in Fig. 4, and thus other details are omitted here for conciseness. With the method of Fig. 8, information of sequence numbers carried in the last groupcast frames transmitted in other available links is indicated on the current link.

Correspondingly, embodiments of the present disclosure also provide a method of communication implemented at a second device. Fig. 9 illustrates a flowchart of a method 900 of communication implemented at a second device according to example embodiments of the present disclosure. The method 900 can be implemented at the second device 120 shown in Fig. 1. For the purpose of discussion, the method 900 will be described with reference to Fig. 1. It is to be understood that method 900 may further include additional blocks not shown and/or omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

As shown in Fig. 9, at block 910, the second device 120 receives, from the first device 110, information regarding a set of sequence numbers in a second available link (for example, the link 131 in Fig. 1) , the set of sequence numbers being carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links (for example, the

links

132 and 133 in Fig. 1) from the first device 110 to the second device 120.

In some embodiments, the second device 120 may receive, as the information, an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link. In some embodiments, the second device 120 may receive the set of sequence numbers as the information, a sequence number in the set of sequence numbers being assigned from a sequence number space common for the set of first available links and the second available link.

In some embodiments, the second device 120 may receive the information in at least one of a beacon frame, a reassociation response frame, an association response frame, a probe response frame or a ML probe response frame. In some embodiments, the second device 120 may receive the information by at least one of the following: receiving the information in a reduced neighbor report element; or receiving the information in a multi-link element.

In some embodiments, the second device 120 may receive the information in the reduced neighbor report element by obtaining the information from a multi-link device parameters subfield of the reduced neighbor report element. In some embodiments, the second device 120 may receive the information in the multi-link element by: determining whether an indication in a station control subfield of a per-station subelement of the multi-link element indicates a presence of an extended subfield in the per-station subelement; and in accordance with a determination that the indication indicates the presence of the extend subfield, obtaining the information from the extended subfield.

In some embodiments, the second device 120 may receive the information in at least one of an action frame or an aggregated control field of a frame without a Reduced Neighbor Report element or a Multi-Link element.

At block 920, the second device 120 performs, based on the information, a transition from the second available link to a first available link in the set of first available links. In some embodiments, the second device 120 may determine a target link in the set of first available links, and perform the transition from the second available link to the target link.

In some embodiments, the second device 120 may determine a candidate link in the set of first available links so that no groupcast frame is missed. If a channel of the candidate link is available, the second device 120 may determine the candidate link as the target link. If a channel of the candidate link is unavailable, the second device 120 may select a further link in the set of first available links as the target link, where a channel of the further link is available.

In some embodiments where a sequence number carried in the last groupcast frames transmitted in the target link is equal to or smaller than a further sequence number carried in the last groupcast frame transmitted in the second available link, the second device 120 may receive groupcast frames on the target link while stopping receiving groupcast frames on the second available link. In some embodiments where the sequence number carried in the last groupcast frames transmitted in the target link is larger than the further sequence number carried in the last groupcast frame transmitted in the second available link, the second device 120 may receive groupcast frames on both the target link and the second available link; in accordance with a determination that a groupcast frame transmitted with the highest sequence number that is missed on the target link is received on the second available link, stopping receiving groupcast frames on the second available link.

The operations in the method of Fig. 9 correspond to that in the process described in Fig. 4, and thus other details are omitted here for concise. With the method of Fig. 9, a smooth link transition may be facilitated.

EXAMPLE IMPLEMENTATION OF APPARATUS , DEVICES AND MEDIUM

In some embodiments, an apparatus (for example, the first device 110) capable of performing the method 800 may comprise means for performing the respective steps of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus may comprise: means for generating, at a first device, information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to a second device; and means for transmitting the information in a second available link to the second device.

In some embodiments, the means for generating may comprise means for generating, as the information, an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link. In some embodiments, the means for generating may comprise means for generating the set of sequence numbers as the information, a sequence number in the set of sequence numbers being assigned from a sequence number space common for the set of first available links and the second available link.

In some embodiments, the means for transmitting may comprise means for transmitting the information in at least one of a beacon frame, a reassociation response frame, an association response frame, a probe response frame or a ML probe response frame. In some embodiments, the means for transmitting may comprise means for at least one of the following: causing the information to be comprised in a reduced neighbor report element; or causing the information to be comprised in a multi-link element.

In some embodiments, the means for transmitting may comprise means for causing the information to be comprised in a multi-link device parameters subfield of the reduced neighbor report element. In some embodiments, the means for transmitting may comprise: means for causing the information to be comprised in an extended subfield in a per-station subelement of the multi-link element; and means for causing an indication to be comprised in a station control subfield of the per-station subelement, the indication indicating a presence of the extended subfield.

In some embodiments, the means for transmitting may comprise means for transmitting the information in at least one of an action frame or an aggregated control field of a frame without a Reduced Neighbor Report element or a Multi-Link element.

In some embodiments, an apparatus (for example, the second device 120) capable of performing the method 900 may comprise means for performing the respective steps of the method 900. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus may comprise: means for receiving, at a second device and from a first device, information regarding a set of sequence numbers in a second available link, the set of sequence numbers being carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to the second device; and means for performing, based on the information, a transition from the second available link to a first available link in the set of first available links.

In some embodiments, the means for receiving may comprise: means for receiving, as the information, an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link. In some embodiments, the means for receiving may comprise: means for receiving the set of sequence numbers as the information, a sequence number in the set of sequence numbers being assigned from a sequence number space common for the set of first available links and the second available link.

In some embodiments, the means for receiving may comprise: means for receiving the information in at least one of a beacon frame, a reassociation response frame, an association response frame, a probe response frame or a ML probe response frame. In some embodiments, the means for receiving may comprise: means for at least one of the following: receiving the information in a reduced neighbor report element; or receiving the information in a multi-link element.

In some embodiments, the means for receiving may comprise: means for obtaining the information from a multi-link device parameters subfield of the reduced neighbor report element. In some embodiments, the means for receiving may comprise: means for determining whether an indication in a station control subfield of a per-station subelement of the multi-link element indicates a presence of an extended subfield in the per-station subelement; and means for, in accordance with a determination that the indication indicates the presence of the extend subfield, obtaining the information from the extended subfield.

In some embodiments, the means for receiving may comprise means for receiving the information in at least one of an action frame or an aggregated control field of a frame without a Reduced Neighbor Report element or a Multi-Link element.

In some embodiments, the means for performing may comprise: means for determining a target link in the set of first available links; and means for performing the transition from the second available link to the target link. In some embodiments, the means for determining may comprise: means for determining a candidate link in the set of first available links so that no groupcast frame is missed; means for, in accordance with a determination that a channel of the candidate link is available, determining the candidate link as the target link; and means for, in accordance with a determination that a channel of the candidate link is unavailable, selecting a further link in the set of first available links as the target link, where a channel of the further link is available.

In some embodiments, the means for determining may comprise: means for, in accordance with a determination that a sequence number carried in the last groupcast frames transmitted in the target link is equal to or smaller than a further sequence number carried in the last groupcast frame transmitted in the second available link, receiving groupcast frames on the target link and stopping receiving groupcast frames on the second available link; and means for, in accordance with a determination that the sequence number carried in the last groupcast frames transmitted in the target link is larger than the further sequence number carried in the last groupcast frame transmitted in the second available link, receiving groupcast frames on both the target link and the second available link; and means for, in accordance with a determination that a groupcast frame transmitted with the highest sequence number that is missed on the target link is received on the second available link, stopping receiving groupcast frames on the second available link.

FIG. 10 is a simplified block diagram of a device 1000 that is suitable for implementing embodiments of the present disclosure. The device 1000 may be provided to implement the first device or the second device, for example the first device 110 or the second device 120 as shown in Fig. 1. As shown, the device 1000 includes one or more processors 710, one or more memories 1020 coupled to the processor 1010, and one or more communication modules 1040 (such as, transmitters and/or receivers) coupled to the processor 1010.

The communication module 1040 is for bidirectional communications. The communication module 1040 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

The processor 1010 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1000 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 1020 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 1024, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 1022 and other volatile memories that will not last in the power-down duration.

A computer program 1030 includes computer executable instructions that are executed by the associated processor 1010. The program 1030 may be stored in the ROM 1024. The processor 1010 may perform any suitable actions and processing by loading the program 1030 into the RAM 1022.

The embodiments of the present disclosure may be implemented by means of the program 1030 so that the device 1000 may perform any process of the disclosure as discussed with reference to Fig. 4. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some embodiments, the program 1030 may be tangibly contained in a computer readable medium which may be included in the device 1000 (such as in the memory 1020) or other storage devices that are accessible by the device 1000. The device 1000 may load the program 1030 from the computer readable medium to the RAM 1022 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. FIG. 11 shows an example of the computer readable medium 1100 in form of CD or DVD. The computer readable medium has the program 1030 stored thereon.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the

methods

800 and 900 as described above with reference to Figs. 8 and 9. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A device comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the device to:

generate information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the device to a second device; and

transmit the information in a second available link to the second device.
The device of claim 1, wherein the device is caused to generate the information by:

generating, as the information, an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link.
The device of claim 1, wherein the device is caused to generate the information by:

generating the set of sequence numbers as the information, a sequence number in the set of sequence numbers being assigned from a sequence number space common for the set of first available links and the second available link.
The device of claim 1, wherein the device is caused to transmit the information by:

transmitting the information in at least one of a beacon frame, a reassociation response frame, an association response frame, a probe response frame or a multi-link probe response frame.
The device of claim 4, wherein the device is caused to transmit the information by at least one of the following:

causing the information to be comprised in a reduced neighbor report element; or

causing the information to be comprised in a multi-link element.
The device of claim 5, wherein the information is comprised in the reduced neighbor report element by:

causing the information to be comprised in a multi-link device parameters subfield of the reduced neighbor report element.
The device of claim 5, wherein the information is comprised in the multi-link element by:

causing the information to be comprised in an extended subfield in a per-station profile subelement of the multi-link element; and

causing an indication to be comprised in a station control subfield of the per-station profile subelement, the indication indicating a presence of the extended subfield.
The device of claim 1, wherein the device is caused to transmit the information by:

transmitting the information in at least one of an action frame or an aggregated control field of a frame without a reduced neighbor report element or a multi-link element.
The device of claim 1, wherein the device is an access point multi-link device, and the second device is a non-access point multi-link device.
A device comprising:

at least one processor; and

at least one memory including computer program code;

the at least one memory and the computer program code configured to, with the at least one processor, cause the device to:

receive, from another device and in a second available link, information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the other device to the device; and

perform, based on the information, a transition from the second available link to a first available link in the set of first available links.
The device of claim 10, wherein the device is caused to receive the information by:

receiving, as the information, an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link.
The device of claim 10, wherein the device is caused to receive the information by:

receiving the set of sequence numbers as the information, a sequence number in the set of sequence numbers being assigned from a sequence number space common for the set of first available links and the second available link.
The device of claim 10, wherein the device is caused to receive the information by:

receiving the information in at least one of a beacon frame, a reassociation response frame, an association response frame, a probe response frame or a multi-link probe response frame.
The device of claim 13, wherein the device is caused to receive the information by at least one of the following:

receiving the information in a reduced neighbor report element; or

receiving the information in a multi-link element.
The device of claim 14, wherein the device is caused to receive the information in the reduced neighbor report element by:

obtaining the information from a multi-link device parameters subfield of the reduced neighbor report element.
The device of claim 14, wherein the device is caused to receive the information in the multi-link element by:

determining whether an indication in a station control subfield of a per-station profile subelement of the multi-link element indicates a presence of an extended subfield in the per-station profile subelement; and

in accordance with a determination that the indication indicates the presence of the extend subfield, obtaining the information from the extended subfield.
The device of claim 10, wherein the device is caused to receive the information by:

receiving the information in at least one of an action frame or an aggregated control field of a frame without a reduced neighbor report element or a multi-link element.
The device of claim 10, wherein the device is caused to perform the transition by:

determining a target link in the set of first available links; and

performing the transition from the second available link to the target link.
The device of claim 18, wherein the device is caused to determine the target link by:

determining a candidate link in the set of first available links so that no groupcast frame is missed;

in accordance with a determination that a channel of the candidate link is available, determining the candidate link as the target link; and

in accordance with a determination that a channel of the candidate link is unavailable, selecting a further link in the set of first available links as the target link, a channel of the further link is available.
The device of claim 18, wherein the device is caused to perform the transition by:

in accordance with a determination that a sequence number carried in the last groupcast frames transmitted in the target link is equal to or smaller than a further sequence number carried in the last groupcast frame transmitted in the second available link, receiving groupcast frames on the target link and stopping receiving groupcast frames on the second available link; and

in accordance with a determination that the sequence number carried in the last groupcast frames transmitted in the target link is larger than the further sequence number carried in the last groupcast frame transmitted in the second available link,

receiving groupcast frames on both the target link and the second available link; and

in accordance with a determination that a groupcast frame transmitted with the highest sequence number that is missed on the target link is received on the second available link, stopping receiving groupcast frames on the second available link.
The device of claim 10, wherein the other device is an access point multi-link device, and the device is a non-access point multi-link device.
A method of communication, comprising:

generating, at a first device, information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to a second device; and

transmitting the information in a second available link to the second device.
The method of claim 22, wherein generating the information comprises:

generating, as the information, an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link.
The method of claim 22, wherein generating the information comprises:

generating the set of sequence numbers as the information, a sequence number in the set of sequence numbers being assigned from a sequence number space common for the set of first available links and the second available link.
The method of claim 22, wherein transmitting the information comprises:

transmitting the information in at least one of a beacon frame, a reassociation response frame, an association response frame, a probe response frame or a multi-link probe response frame.
The method of claim 25, wherein transmitting the information comprises at least one of the following:

causing the information to be comprised in a reduced neighbor report element; or

causing the information to be comprised in a multi-link element.
The method of claim 26, wherein causing the information to be comprised in the reduced neighbor report element comprises:

causing the information to be comprised in a multi-link device parameters subfield of the reduced neighbor report element.
The method of claim 26, wherein causing the information to be comprised in the multi-link element comprises:

causing the information to be comprised in an extended subfield in a per-station subelement of the multi-link element; and

causing an indication to be comprised in a station control subfield of the per-station subelement, the indication indicating a presence of the extended subfield.
The method of claim 22, wherein transmitting the information comprises:

transmitting the information in at least one of an action frame or an aggregated control field of a frame without a reduced neighbor report element or a multi-link element.
The method of claim 22, wherein the first device is an access point multi-link device, and the second device is a non-access point multi-link device.
A method of communication, comprising:

receiving, at a second device and from a first device, information regarding a set of sequence numbers in a second available link carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to the second device; and

performing, based on the information, a transition from the second available link to a first available link in the set of first available links.
The method of claim 31, wherein receiving the information comprises:

receiving, as the information, an offset of a sequence number in the set of sequence numbers with respect to a further sequence number carried in the last groupcast frame transmitted in the second available link.
The method of claim 31, wherein receiving the information comprises:

receiving the set of sequence numbers as the information, a sequence number in the set of sequence numbers being assigned from a sequence number space common for the set of first available links and the second available link.
The method of claim 31, wherein receiving the information comprises:

receiving the information in at least one of a beacon frame, a reassociation response frame, an association response frame, a probe response frame or a multi-link probe response frame.
The method of claim 34, wherein receiving the information comprises at least one of the following:

receiving the information in a reduced neighbor report element; or

receiving the information in a multi-link element.
The method of claim 35, wherein receiving the information in the reduced neighbor report element comprises:

obtaining the information from a multi-link device parameters subfield of the reduced neighbor report element.
The method of claim 35, wherein receiving the information in the multi-link element comprises:

determining whether an indication in a station control subfield of a per-station subelement of the multi-link element indicates a presence of an extended subfield in the per-station subelement; and

in accordance with a determination that the indication indicates the presence of the extend subfield, obtaining the information from the extended subfield.
The method of claim 31, wherein receiving the information comprises:

receiving the information in at least one of an action frame or an aggregated control field of a frame without a reduced neighbor report element or a multi-link element.
The method of claim 31, wherein performing the transition comprises:

determining a target link in the set of first available links; and

performing the transition from the second available link to the target link.
The method of claim 39, wherein determining the target link comprises:

determining a candidate link in the set of first available links so that no groupcast frame is missed;

in accordance with a determination that a channel of the candidate link is available, determining the candidate link as the target link; and

in accordance with a determination that a channel of the candidate link is unavailable, selecting a further link in the set of first available links as the target link, a channel of the further link is available.
The method of claim 39, wherein performing the transition comprises:

in accordance with a determination that a sequence number carried in the last groupcast frames transmitted in the target link is equal to or smaller than a further sequence number carried in the last groupcast frame transmitted in the second available link, receiving groupcast frames on the target link while stopping receiving groupcast frames on the second available link; and

in accordance with a determination that the sequence number carried in the last groupcast frames transmitted in the target link is larger than the further sequence number carried in the last groupcast frame transmitted in the second available link,

receiving groupcast frames on both the target link and the second available link; and

in accordance with a determination that a groupcast frame transmitted with the highest sequence number that is missed on the target link is received on the second available link, stopping receiving groupcast frames on the second available link.
The method of claim 31, wherein the first device is an access point multi-link device, and the second device is a non-access point multi-link device.
An apparatus of communication, comprising:

a first device having:

means for generating information regarding a set of sequence numbers carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to a second device; and

means for transmitting the information in a second available link to the second device.
An apparatus of communication, comprising:

a first device having:

means for receiving from a second device, information regarding a set of sequence numbers in a second available link, the set of sequence numbers being carried in the last groupcast frames transmitted respectively in a first available link from a set of first available links from the first device to the second device; and

means for performing, based on the information, a transition from the second available link to a first available link in the set of first available links.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform the method according to any of claims 22 to 30.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform the method according to any of claims 31 to 42.