Dynamic subband operation with independent TXOP sharing procedures

Abstract

In a BSS, an AP triggers a DSO to better use the BSS operating channel when some of its associated stations are camped on a primary subchannel forming a subpart of the BSS operating channel. Those stations switch to one or more secondary subchannels of the BSS operating channel to perform communication over the secondary subchannel(s) simultaneously to other associated stations remained on the primary subchannel and performing communication over that primary subchannel. The AP organizes independent TXOP sharing (TXS) procedures on each of the primary and secondary subchannels by signalling separate time-sharing schemes. This aims at providing more flexibility in stations' communications over the subchannels. A first MU-RTS TXS Trigger frame is used to trigger the DSO, while two or more second MU-RTS TXS Trigger frames are transmitted over the primary subchannel and each secondary subchannel respectively to separately signal the time-sharing schemes for the respective subchannels.

Description

[0001] DYNAMIC SUBBAND OPERATION WITH INDEPENDENT TXOP SHARING PROCEDURES

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to wireless communications and more specifically to wireless communications sharing a transmission opportunity (TXOP) under Dynamic Subband Operation.

[0004] BACKGROUND OF THE INVENTION

[0005] The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. Furthermore, all embodiments are not necessarily intended to solve all or even any of the problems brought forward in this section.

[0006] Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.

[0007] The WLAN (Wireless Local Area Network) technology based on the IEEE (Institute of Electrical and Electronics Engineers - RTM) 802.11 family standards provides a very simple distributed channel access mechanism. Distributed channel access means that a device, in IEEE 802.11 terminology known as a station (STA), either access point (AP) or a non-access point (non-AP), tries to access an operating channel when it has data to send.

[0008] An operating channel of 40, 80, 160 or 320MHz width (or even more in the future) is usually made of a primary channel and one or more secondary channels (each channel being 20MHz or a multiple thereof). The primary channel is used for signalling (including channel access procedure such as the contention-based channel access method called Enhanced Distributed Channel Access - EDCA) and backwards compatibility, while the secondary channels are used to obtain higher throughput.

[0009] Due to hardware constraints, there are situations where an AP has a wider operating channel than its associated STAs. For example, the AP operates over a 320MHz bandwidth while its STAs operates on 20MHz to 160MHz, due to their radios.

[0010] The Dynamic Subband Operation or Dynamic Subchannel Operation (DSO) mechanism has been recently introduced by the task group IEEE 802.11 bn, to take into account of these situations, in order to increase network efficiency. The principle of the DSO procedure is the following one. A STA that can only operate on a subpart of the operating channel of its AP (e.g., only over the 160 MHz primary channel of the AP) can switch its own operating channel to a subchannel (or subband) of the operating channel of its AP (e.g. the 160 MHz secondary channel of the AP), which subchannel is out of the STA’s initial operating channel. Next, the STA can perform Downlink (DL) / Uplink (UL) OFDMA exchanges over the switched subchannel, after which it switches back to its initial operating channel.

[0011] Without the DSO mechanism, the secondary 160MHz channel would not be used at all and would be wasted. With the DSO mechanism, some STAs can switch their own operating channel to the secondary 160MHz channel and use it to perform DL / UL OFDMA, while other STAs can simultaneously use the primary 160MHz channel. As a consequence, the whole 320MHz operating channel is used effectively.

[0012] However, the DSO mechanism is limited to DL / UL OFDMA exchanges under the control of the AP.

[0013] SUMMARY OF INVENTION

[0014] It is a broad objective of the present invention to overcome some of the foregoing concerns. An aim of the invention is to improve the use of the medium within the operating channel of the AP, in particular to improve bandwidth usage flexibility and efficiency.

[0015] It is proposed to include TXOP sharing within the primary and secondary channels of the DSO mechanism. Such approach is referred below as DSO TXS procedure (or DSO TXS operations or DSO TXS mechanism). As a result, STAs obtaining shared TXOP timeslots are free to use them independently to the other stations (including the AP). Furthermore, the AP may organise the TXOP sharing independently on each DSO channel.

[0016] In this respect, the disclosure proposes a communication method in a wireless network, comprising, at an access point (AP) operating on an operating channel including a primary subchannel and a non-overlapping secondary subchannel - these subchannels representing the DSO channels sending, to stations, at least one frame to organise a time-sharing of a transmission opportunity (TXOP) gained by the AP, wherein the at least one frame signals a channel switch from the primary subchannel to the secondary subchannel for at least one ofthe stations that is initially operating on the primary subchannel, and signals time-sharing schemes of the TXOP on the primary subchannel and of the TXOP on the secondary subchannel, respectively. The time-sharing scheme on the secondary subchannel defines an allocation over time of the secondary subchannel. It aims at providing some opportunities to the switching station to perform frame exchanges.

[0017] Correspondingly, a communication method in a wireless network, comprises, at a station operating on a primary subchannel of an operating channel of a Basic Service Set (BSS), the operating channel including the primary subchannel and a non-overlapping secondary subchannel: receiving, from an access point (AP) of the BSS, at least one frame that organises a time-sharing of a transmission opportunity (TXOP) gained by the AP, wherein the at least one frame signals a channel switch of the station from the primary subchannel to the secondary subchannel and signals a time-sharing scheme of the TXOP on the secondary subchannel, responsive to the at least one frame, switching to the secondary subchannel, and performing a frame exchange over the secondary channel based on the time-sharing scheme.

[0018] The time-sharing scheme may be implemented using the Triggered TXOP sharing (TXS) procedure as introduced in the IEEE 802.11 be D6.0 amendment. This procedure allows an AP to allocate a portion of an obtained TXOP to one associated non-AP EHT STA for transmitting one or more non-TB PPDUs. The AP sends an MU-RTS TXS Trigger frame, which is a variant of MU-RTS Trigger frame, to a STA to share the TXOP. Two different TXS modes exist: Mode 1 wherein the non-AP EHT STA is allowed to send UL (uplink) frames, which means the frame is destined to the AP; and Mode 2 wherein the non-AP EHT STA is allowed to send P2P (peer to peer) frames - which means the frame is destined to the other STA than AP - or UL frames. The TXS procedure may be extended to a multi-AP TXS where the AP allocates a portion of the obtained TXOP to another AP.

[0019] In the methods above, the station is preferably a non-AP station belonging to the BSS. However, in variants, it may be an AP managing another BSS. Hence, in some embodiments, the TXS over the multiple subchannels allows providing transmission timeslots to stations of the BSS as well as to another BSS.

[0020] Optional features are defined below with reference to methods, while they can be transposed into device features.

[0021] In some embodiments, the channel switch signalling and the time-sharing scheme or schemes are provided within one single frame. All the stations (STAs) therefore obtain all the information for frame exchanges at once. These embodiments minimize the signalling overhead.

[0022] In other embodiments, the channel switch signalling is provided within a first frame and the time-sharing scheme or schemes are respectively provided in multiple second and separate frames. The first frame can be made short to have earlier switching from the concerned stations, while the second frames split the time-sharing information over multiple simultaneous frames, hence also reducing their transmission time. Network efficiency is therefore improved. These embodiments advantageously allow the AP to dynamically adjust the time-sharing schemes to responses to the first frame, in order to reduce risks of losing / wasting timeslots by stations not ready.

[0023] In embodiments, at least one second frame providing a time-sharing scheme includes padding to have the same length as another second frame providing another time- sharing scheme. Aligning the frames providing the time-sharing schemes ensures correct reception, by the AP, of (synchronized) responses to these two frames from stations.

[0024] In some embodiments, the first frame is transmitted over the primary and secondary subchannels, whereas the second and separate frames are transmitted over their respective subchannel only. Hence, the station receives the second and separate frame over the secondary subchannel only.

[0025] In some embodiments, the first frame signals a first subpart of the secondary subchannel over which the station has to respond to the first frame and signals a second and distinct subpart of the secondary subchannel over which another station has to respond to the first frame. The station therefore sends to the AP a response to the first frame overthe first subpart only of the secondary channel. The other station does the same over its subpart. This enables the AP to know whether each station has successfully switched or remained in the indicated subchannel and is now ready for communications.

[0026] In particular embodiments, the AP builds the time-sharing schemes on the primary and secondary subchannels based on responses to the first frame received from stations on the primary and secondary subchannels respectively. If the AP does not receive a response from a station, it can omit it from scheduling in the time-sharing scheme, because the station is not ready to communicate.

[0027] In some embodiments, the AP receives a response to the at least one frame from the station over the secondary subchannel and another response from another station over the primary subchannel. From the station perspective, after switching to the secondary subchannel, it sends to the AP a response to the at least one frame over the secondary subchannel.

[0028] In some embodiments, the at least one frame defines multiple TXOP timeslots within the TXOP and signals different time-sharing schemes for the primary and secondary subchannels over the multiple TXOP timeslots. In such a manner, the AP can flexibly schedule multiple TXOP sharing over multiple frequency subchannels.

[0029] In specific embodiments, one of the time-sharing schemes gives back the primary and secondary subchannels to the AP during one of the multiple timeslots. This gives the AP to have the opportunity to conduct own communications (DL traffic or to open the operating channel to random access usage) amongst timeslots offered to its associated stations over the multiple DSO subchannels.

[0030] In some embodiments, a time-sharing scheme on the secondary subchannel allocates the secondary subchannel to the station for peer-to-peer (P2P) exchange with another station of the BSS. This keeps the primary subchannel available for intra-BSS communications with those stations of the BSS that are unable to switch to the secondary subchannel (e.g., due to hardware capabilities).

[0031] For example, the time-sharing scheme signals an Associated Identifier (AID) of the station or an identifier of a P2P Group to which the station belongs. Hence, the AP is able to provide a timeslot to a specific STA for it to transmit allowed traffics, or to provide the timeslot to a P2P group for its peer STAs to organize how they can transmit P2P traffic in the more flexible way.

[0032] In some embodiments, a time-sharing scheme on the primary subchannel allocates the primary subchannel to a second station of the BSS for peer-to-peer exchange with a station not belonging to the BSS. With this, the AP guarantees that the peer stations can perform P2P traffic exchanges although it cannot control the un-associated station (e.g. to switch to the secondary subchannel).

[0033] For example, the time-sharing scheme signals an Associated Identifier (AID) of the second station or an identifier of a P2P Group to which the second station belongs

[0034] In some embodiments, the at least one frame is a MU-RTS TXS Trigger frame (Trigger Type subfield set to MU-RTS and TXS Mode subfield not set to 0, in the Common Info field). In particular, a TXS Mode subfield of the MU-RTS TXS Trigger frame may be set to value 3 in order to define a new TXS mode dedicated for example to DSO TXS procedures.

[0035] In some embodiments, the AP may use one of the primary and secondary subchannels for a frame exchange (whatever its role, frame sender or receiver), wherein a resource unit of the used subchannel in the vicinity of the other subchannel remains unused during the frame exchange. Similarly, the station may perform the frame exchange over the secondary channel not using a resource unit of the secondary subchannel in the vicinity of the primary subchannel. A guard RU is therefore defined to avoid or reduce risks of interference between the primary and secondary subchannels.

[0036] In some embodiments, the AP sends a frame prior to the at least one frame in order to reserve the medium for the TXOP. This allows the TXOP to be safely obtained using a short frame, before sharing it with multiple stations using one or more longer frames. Hence, network efficiency is improved.

[0037] In some embodiments, the station switches back to the primary subchannel at the end of a time-sharing duration signalled in the at least one frame.

[0038] The disclosure also proposes a Trigger frame signalling a channel switch from a primary subchannel to a secondary subchannel for at least one receiving station that is operating on the primary subchannel.

[0039] The frame may have a padding field after a frame check sequence (FCS) field. This is to offer enough time for any receiving station to fully switch its operating channel to the secondary subchannel when appropriate. Indeed, the post-FCS padding allows the station to start the channel switch operation without validating the padding field.

[0040] In some embodiments, the frame signals a MU-RTS Trigger type, wherein a TXS Mode subfield of a Common Info field is set to 3. A new MU-RTS TXS Trigger frame can therefore be defined, dedicated to DSO TXS procedures.

[0041] In some embodiments, the frame comprises at least one subfield in a Common Info field to define multiple TXOP timeslots within the TXOP in which to apply different time-sharing schemes. For example, the at least one subfield comprises a first subfield signalling the number of TXOP timeslots in the multiple TXOP timeslots and second subfields signalling the durations of the multiple TXOP timeslots respectively.

[0042] In some embodiments, the frame further signals separate time-sharing schemes of a TXOP on the primary subchannel and of the TXOP on the secondary subchannel, respectively. For example, it comprises multiple User Info fields defining the time-sharing schemes respectively. This contrasts with the conventional MU-RTS TXS Trigger frame which can carry only one User Info field. In particular, each User Info field may comprise: a subfield signalling the primary or secondary subchannel, a subfield including an Associated Identifier (AID) of a station to which the signalled primary or secondary subchannel is allocated or an identifier of a peer-to-peer (P2P) Group to which the signalled primary or secondary subchannel is allocated. This subfield may be used to indicate to the STA whether to switch its STA operating channel to the secondary subchannel or not during the following TXOP sharing procedure, a subfield signalling a transmission mode in the allocated primary or secondary subchannel, optionally, a subfield signalling a TXOP timeslot from amongst multiple TXOP timeslots within the TXOP.

[0043] In embodiments, the transmission mode subfield takes a value from the following set of values: a first value signalling the TXOP or corresponding TXOP timeslot is allocated back to an owner of the TXOP, a second value signalling the allocated station can only transmit MPDU(s) addressed to its associated AP, a third value signalling the allocated station can transmit MPDU(s) addressed to its associated AP or transmit P2P MPDU(s), a fourth value signalling the allocated station or P2P Group can only transmit P2P MPDU(s).

[0044] In some embodiments, the frame signals a Trigger type with a value comprised between 9 and 15. A new Trigger frame variant can therefore be defined dedicated to the DSO TXS procedure of the present disclosure.

[0045] Correlatively, the invention also provides a wireless communication device comprising at least one microprocessor configured for carrying out any method as described above.

[0046] Another aspect of the invention relates to a non-transitory computer-readable medium storing a program which, when executed by a microprocessor or computer system in a wireless device, causes the wireless device to perform any method as described above.

[0047] At least parts of the methods according to the invention may be computer implemented. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit", "module" or "system". Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer usable program code embodied in the medium.

[0048] Since the present invention can be implemented in software, the present invention can be embodied as computer readable code for provision to a programmable apparatus on any suitable carrier medium. A tangible carrier medium may comprise a storage medium such as a hard disk drive, a magnetic tape device or a solid-state memory device and the like. A transient carrier medium may include a signal such as an electrical signal, an electronic signal, an optical signal, an acoustic signal, a magnetic signal or an electromagnetic signal, e.g., a microwave or RF signal.

[0049] BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Embodiments of the invention will now be described, by way of example only, and with reference to the following drawings in which:

[0051] Figure 1 illustrates an exemplary network environment in which embodiments of the present disclosure can be implemented;

[0052] Figure 2 illustrates, using a timeline, a Dynamic Subchannel Operation (DSO;

[0053] Figure 3 illustrates, using a flowchart, general operations at an AP to provide DSO TXS opportunities to STAs, e.g. to its associated non-AP STAs;

[0054] Figure 4 illustrates, using a flowchart, general operations at STAs to use DSO TXS opportunities provided by an AP;

[0055] Figures 5, 6, 7, 8 and 9 illustrate, using timelines, various scenarios of communications involving DSO TXS procedures, according to embodiments of the present disclosure;

[0056] Figures 10a and 10b illustrate, using flowcharts, steps at an AP to conduct DSO TXS operations according to embodiments of the disclosure;

[0057] Figures 10c and 10d illustrate, using flowcharts, steps at a STA performing DSO TXS operations under the control of an AP, preferably its AP, according to embodiments of the disclosure;

[0058] Figures 11a, 11b, 11c and 11d illustrate an exemplary frame format for a frame signalling both channel switches for STAs and time-sharing schemes;

[0059] Figures 12a, 12b, 12c, 12d and 12e illustrate exemplary frame formats for a frame signalling channel switches for the STAs and a second frame signalling time-sharing schemes; and

[0060] Figures 13a and 13b show schematic representations of a wireless communication device in accordance with embodiments of the present invention.

[0061] DETAILLED DESCRIPTION OF EMBODIMENTS The application discloses, in a BSS, an AP that triggers a Dynamic Subchannel Operation (DSO) to better use the BSS operating channel when some of its associated stations are camped on a primary subchannel forming a subpart of the BSS operating channel. Those stations switch to one or more secondary subchannels of the BSS operating channel to perform communication over the secondary subchannel(s) simultaneously to other associated stations remained on the primary subchannel and performing communication over that primary subchannel. The AP organizes independent TXOP sharing (TXS) procedures on each of the primary and secondary subchannels by signalling separate time-sharing schemes. This aims at providing more flexibility in stations’ communications over the subchannels. A first MU-RTS TXS Trigger frame is used to trigger the DSO, while two or more second MU-RTS TXS Trigger frames are transmitted over the primary subchannel and each secondary subchannel respectively to separately signal the time-sharing schemes for the respective subchannels.

[0062] The techniques described herein may be used for various broadband wireless communication systems, including communication systems that are based on an orthogonal multiplexing scheme. Examples of such communication systems include Spatial Division Multiple Access (SDMA) system, Time Division Multiple Access (TDMA) system, Orthogonal Frequency Division Multiple Access (OFDMA) system, and Single-Carrier Frequency Division Multiple Access (SC-FDMA) system. An SDMA system may utilize sufficiently different directions to simultaneously transmit data belonging to multiple user terminals, i.e., wireless devices or stations. A TDMA system may allow multiple user terminals to share the same frequency channel by dividing the transmission signal into different time slots or resource units, each time slot being assigned to different user terminal. An OFDMA system utilizes orthogonal frequency division multiplexing (OFDM), which is a modulation technique that partitions the overall system bandwidth into multiple orthogonal sub-carriers or resource units. These sub-carriers may also be called tones, bins, etc. With OFDM, each sub-carrier may be independently modulated with data. An SC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit on sub-carriers that are distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on a block of adjacent sub-carriers, or enhanced FDMA (EFDMA) to transmit on multiple blocks of adjacent sub-carriers.

[0063] The teachings herein may be incorporated into (e.g., implemented within or performed by) a variety of apparatuses (e.g., stations). In some aspects, a wireless device or station implemented in accordance with the teachings herein may comprise an access point (so- called AP) or not (so-called non-AP STA (station)). STA includes both AP and non-AP STA.

[0064] An AP may comprise, be implemented as, or known as a Node B, Radio Network Controller (“RNC”), evolved Node B (eNB), 5G Next generation base station (gNB), Base Station Controller (“BSC”), Base Transceiver Station (“BTS”), Base Station (“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver, Basic Service Set (“BSS”), Extended Service Set (“ESS”), Radio Base Station (“RBS”), or some other terminology. A non-AP station may comprise, be implemented as, or known as a subscriber station, a subscriber unit, a mobile station (MS), a remote station, a remote terminal, a user terminal (UT), a user agent, a user device, user equipment (UE), a user station, or some other terminology. In some implementations, a non-AP STA may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (“SIP”) phone, a wireless local loop (“WLL”) station, a personal digital assistant (“PDA”), a handheld device having wireless connection capability, or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or smart phone), a computer (e.g., a laptop), a tablet, a portable communication device, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music orvideo device, or a satellite radio), a global positioning system (GPS) device, or any other suitable device that is configured to communicate via a wireless or wired medium. In some aspects, the non-AP station may be a wireless node. Such wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link.

[0065] An AP manages a set of STAs (registered to it or associated with it) that together organize their accesses to the wireless medium for communication purposes. The STAs (including the AP to which they register) form a service set, here below referred to as basic service set, BSS (although other terminology can be used). A same physical STA acting as an access point may manage two or more BSSs (and thus corresponding WLANs): each BSS is thus uniquely identified by a specific basic service set identification, BSSID and managed by a separate virtual AP implemented in the physical AP. Each STA is identified within a BSS thanks to an identifier, AID, assigned to it by the AP upon registration.

[0066] The 802.11 family of standards define various media access control (MAC) mechanisms to drive access to the wireless medium.

[0067] Each BSS defines a main elementary channel of the wireless medium (known as a primary channel, usually a 20 MHz channel or a multiple of 20 MHz channel) on which the stations (including the AP) perform EDCA contention using generally legacy EDCA parameters (defined in an EDCA Parameter Set provided by the AP). To increase bandwidth for the forthcoming transmission, the stations can simultaneously contend for additional 20 MHz channels, known as secondary channels. The communication channel thus granted for transmission comprises the primary channel and optionally secondary channels.

[0068] An AP can therefore define an operating channel for the BSS, which operating channel is made of a N 20 MHz channels (N>=2), e.g., with a total of 40 MHz, 80 MHz, 160 MHz, 80+80 MHz, 320 MHz bandwidth. The half of the operating channel comprising the primary 20 MHz channel is known as the primary NxI OMHz channel, while the other half is known as the secondary NxI OMHz channel. For example, the primary 40 MHz (resp. 80 MHz, 160 MHz) channel is the 40 MHz channel (resp. 80 MHz, 160 MHz) in a 80 MHz (resp. 160 MHz, 320 MHz) operating channel, formed by the primary channel (20 MHz) and one or more adjacent and aggregated secondary channels (20 MHz each), that is used to transmit 40 MHz (resp. 80 MHz, 160 MHz) physical layer (PHY) protocol data units (PPDUs). Similarly, the secondary 40 MHz (resp. 80 MHz, 160 MHz) channel is the other 40 MHz half (resp. 80 MHz, 160 MHz) in a 80 MHz (resp. 160 MHz, 320 MHz) operating channel. More generally, an operating channel includes a primary channel (whatever its bandwidth) and a secondary channel (whatever its bandwidth) that do not overlap.

[0069] In order to address the issue of increasing bandwidth and decreasing latency requirements that are demanded for wireless communications systems in high-density environments, multi-user (MU) schemes have been developed to allow a single access point (AP) managing a Basic Service Set (BSS) to schedule MU transmissions, i.e., multiple simultaneous transmissions to or from non-AP stations of the BSS, in the wireless network. A MU scheme has been adopted in the 802.11 ax-2021 standard.

[0070] Thanks to the MU feature, a non-AP station has the opportunity to gain access to the wireless medium via two access schemes: the MU scheme and the conventional Enhanced Distributed Channel Access - EDCA (Single User) scheme.

[0071] The 802.11 ax standard allows a MU downlink (DL) transmission to be performed by the AP when gaining access to the wireless medium for a transmission opportunity (TXOP). During the MU DL transmission on the granted communication channel, the AP performs multiple simultaneous elementary transmissions, over so-called resource units (RUs), to various non-AP stations. As an example, the resource units split the communication channel of the wireless network in the frequency domain, based for instance on Orthogonal Frequency Division Multiple Access (OFDMA) technique. The assignment of the RUs to the non-AP stations is signalled at the beginning of the MU Downlink frame, by providing an association identifier (AID) of a non-AP station (individually obtained by each station during its association procedure with the AP) for each RU defined in the transmission opportunity.

[0072] The 802.11 ax standard also allows a MU uplink (UL) transmission to be triggered by the AP when gaining access to the wireless medium. During the MU UL transmission, various non-AP stations can simultaneously transmit data to the AP over the resource units forming the communication channel. To control the MU UL transmission by the non-AP stations, the AP previously sends a control frame, known as a Trigger Frame (TF). The Trigger Frame allocates the resource units to the non-AP stations of the same BSS, using Association IDentifiers (AIDs) assigned to them upon registration to the AP and / or using reserved AIDs designating a group of non-AP stations. The TF also defines the start of the MU UL transmission by the non-AP stations as well as the length thereof. After a non-AP station makes an MU UL transmission, it performs EDCA contention on the medium using temporarily a different (from the legacy ones) set of EDCA parameters, known as MU EDCA parameters (defined in a Multi-User (MU) EDCA Parameter Set provided by the AP).

[0073] The current discussions in the task group 802.11 be, as illustrated by draft IEEE P802.11 be / D6.0, introduce the Multi-Link Operation (MLO) when it comes to MAC layer operation. The MLO allows multi-link devices to establish or setup multiple links and operate them simultaneously.

[0074] A Multi-Link Device (MLD) is a logical entity and has more than one affiliated STA (STA) and has a single medium access control (MAC) service access point (SAP) to logical link control (LLC), which includes one MAC data service. Multiple affiliated non-AP STAs of a non-AP MLD can then setup communication links with multiple affiliated APs of an AP MLD, hence forming a multi-link channel.

[0075] A communication link or “link” thus corresponds to a given channel (e.g. , 20 MHz, 40 MHz, and so on) in a given frequency band (e.g., 2.4 GHz, 5 GHz, 6 GHz) between an AP affiliated with the AP MLD and a non-AP STA affiliated with the non-AP MLD.

[0076] The affiliated APs and non-AP STAs operate on their respective channels in accordance with one or more of the IEEE 802.11 standards (a / b / g / n / ac / ad / af / ah / aj / ay / ax / be / bn) or other wireless communication standards.

[0077] Thanks to the multi-link aggregation, traffic associated with a single MLD can theoretically be transmitted across multiple parallel communication links, thereby increasing network capacity and maximizing utilization of available resources.

[0078] The description below mostly concentrates on a single link for ease of explanation. However, similar considerations can be made with respect to each link forming a multiple link set for MLD devices. Therefore, the term STA or “station” may refer to one affiliated STA of a non- AP MLD (non-AP STAs of a non-AP MLD), and AP may refer to one affiliated AP of an AP MLD.

[0079] Figure 1 illustrates an exemplary network environment in which embodiments of the present disclosure can be implemented.

[0080] The illustrated wireless network environment comprises a group of neighbouring wireless networks that operate over a common communication channel or wireless medium. The common communication channel may correspond to a part (e.g., 20 MHz) or all of an operating channel (e.g., 20 MHz, 40 MHz, 80 MHz, 160 MHz or 320 MHz).

[0081] A first wireless network (or Basic Service Set) BSS1 101 comprises an access point (AP) 1 10 and four STAs 1 11 , 112, 113 and 114 associated with the AP 110 (i.e., registered with it).

[0082] A STA is typically a non-AP station. However, in embodiments, an AP can also be included as a STA. Indeed, in the current IEEE 802.1 1 specification, an AP cannot associate with other AP. However, in the IEEE 802.11 bn Working Group, a Multi-AP Coordination scheme is discussed and APs may have a relationship for this coordination. In the present document, it is therefore considered that an AP may be “associated” with another AP when having such kind of coordination relationship is setup and a communicate can take place with each other.

[0083] A second wireless network P2P (Peer to Peer) Groupl 102 comprises a STA 112 and a peer STA 114.

[0084] A third wireless network P2P Group2 103 comprises a STA 113 and a peer STA 121 . A P2P Group is a group that is formed according to any P2P protocol, e.g., those defined in the IEEE 802.11 such as TDLS (Tunnelled Direct Link Setup) or in the Wi-Fi Alliance such as WiFi Direct or Wi-Fi Aware. One STA may activate a soft AP or mobile AP function and create a P2P connection with other STAs. These are just examples and other P2P protocols are also applicable.

[0085] STA 112 and STA 114 belongs both to BSS1 101 and P2P Groupl 102. STA 113 belongs both to BSS1 101 and P2P Group2 103. STA 121 belonging to P2P Group2 103 is not associated to AP 110.

[0086] Of course, another number of wireless networks and any number of STAs per wireless network can be contemplated.

[0087] In the present disclosure, AP 110 is also referred to as AP1. STA 111 , STA 112, STA 113, STA 114 and STA 121 are also referred to, respectively, as STAn, STA12, STA13, STA14 and STA21. A device may act as an AP of one wireless network and at the same time may belong to another wireless network as an associated STA.

[0088] AP 110 broadcasts management frames, such as beacon frames, to share parameters to be used for the functioning of its BSS 101 .

[0089] The stations (AP and non-AP) of each wireless network exchange data frames over the communication channel 100. A primary channel, usually 20 MHz channel, is defined per wireless network on which the management frames are exchanged. The other 20 MHz channels of the communication channel, if any, are known as secondary channels. Wireless networks 101 , 102, 103 use the same primary channel.

[0090] The stations (including the AP) compete one against another over the communication channel (including the primary channel and optionally secondary channels to increase bandwidth) using EDCA (Enhanced Distributed Channel Access) contention to access the communication channel in order to be granted a transmission opportunity (TXOP). The TXOP may then be used to transmit (single-user, SU) data frames or to implement multi-user (MU) transmissions. In the MU scheme, a single station, usually the AP of the BSS, is allowed to schedule a MU transmission, i.e. , multiple simultaneous transmissions to or from other stations of the wireless network. One implementation of such a MU scheme has been for example adopted in IEEE 802.11 ax amendment standard, known as the Multi-User Uplink and Downlink OFDMA (MU UL and DL OFDMA) procedures. In the MU scheme, resources are defined over the 20 MHz channel or channels used, known as resource units.

[0091] More generally, the resources may include space, frequency and time resources and may be obtained according to different multiplexing schemes. Examples of those schemes include Spatial Division Multiple Access (SDMA) system, Time Division Multiple Access (TDMA) system, Orthogonal Frequency Division Multiple Access (OFDMA) system, and Single-Carrier Frequency Division Multiple Access (SC-FDMA) system.

[0092] Although the description of embodiments of the invention is given in the context of IEEE 802.11 , the embodiments are not limited thereto and they may apply to other types of wireless networks and protocols. AP 110 may define an operating channel for its BSS 101 over 320 MHz (however, any other bandwidth 40 MHz, 80 MHz, 160 MHz may be set). This operating channel is referred below to as BSS operating channel (or bandwidth). Due to hardware capabilities or configuration reasons, some or all of its associated STAs have a narrower operating channel (referred below as STA operating channel (or bandwidth)), for example 160 MHz (or 20 MHz, 40 MHz, 80 MHz).

[0093] STA11 may operate over the entire BSS operating channel, while STA12, STA13, STA14 operate on a narrower operating channel.

[0094] Today's Wi-Fi, including versions up to 11 be (Wi-Fi 7), generally does not allow any STA to transmit frames outside its STA operating channel. For example, in a scenario where the BSS operating channel is 320MHz and one or more STAs are operating over a 160MHz BSS operating channel, the STA only communicates with the AP using the primary 160MHz channel that is in common with the BSS operating channel. The secondary 160MHz channel of the BSS operating channel (which 160MHz channel is outside of the STA operating channel) is not used even if it is idle. The secondary 160MHz channel can only be used by the STA also supporting 320MHz (e.g., STAn).

[0095] The Dynamic Subband Operation or Dynamic Subchannel Operation (DSO) mechanism is used to take advantage of the entire BSS operating channel despite narrower STA operating channels.

[0096] As shown in the exemplary scenario of Figure 2, AP1 110 operates on an 80MHz operating bandwidth (S1) and STAn 111 , STA12 112 operate on a 40MHz operating bandwidth (S1 a and S1 b) which is the lower half of the BSS operating bandwidth (hence the primary 40MHz channel).

[0097] Usually, the AP and its associated STAs perform frame exchanges in the common operating bandwidth (i.e., at most the lower 40MHz channel in this case). By using the DSO mechanism, a STA can perform frame exchanges outside of its STA operating bandwidth (i.e., over the upper 40MHz channel in this case).

[0098] AP1 first gains the medium and obtains the TXOP 200 by sending ICF (Initial Control Frame) 210 to the STAs (STAn and STA12).

[0099] ICF 210 indicates the subchannels the STAs have to use during the TXOP 200. In particular, in ICF 210, AP1 indicates to STAn to switch its operating bandwidth to the upper 40MHz channel (S2a - secondary 40MHz channel of the BSS operating channel) during the TXOP 200. In parallel, AP1 indicates to STA12 to remain on the lower 40MHz (S1 b) during the TXOP 200.

[0100] By receiving ICF 210, STAn switches its STA operating channel to the upper 40MHz channel (S2a - secondary 40MHz channel). This is the “channel switch procedure”. Channel switch procedure may take time as shown by references 221 a or 224a and the duration, which is called “channel switch delay”, differs among the STAs depending on its performance. For example, high-end stations may have shorter channel switch delay and low-end stations may have longer channel switch delay. The channel switch delay of each STA may be shared between the STAs and the AP before the DSO operation, for example during the association procedure.

[0101] ICF 210 may include enough padding to let all the STAs complete their channel switch procedure before they transmit ICR (Initial Control Response) 222a / 222b in response to ICF 210. In embodiments, the length of ICF 210 is adjusted by AP1 with adding post-FCS (Frame Check Sequence) padding to accommodate all the channel switch delay of the STAs involved in the DSO during the TXOP. The post-FCS padding is made of padding bits that are added after the FCS field within the Common Info field of a Trigger frame used as ICF 210. For example, a MU-RTS TXS Trigger frame can be used, or BSRP Trigger frame, BQRP Trigger frame or any other control frame including a new frame which can be defined in the IEEE 802.11 bn amendment for the ICF purpose. The post-FCS padding allows the STAs to start the channel switch operation without validating the padding field.

[0102] ICR may be sent a SIFS (Short Interframe Space) time after ICF 210. ICR 222a / 222b aims at notifying AP1 that the STAs are successfully located (hence are ready) on their indicated subchannel, either after switching or not. ICR may be one of the existing Control Frame such as a CTS frame or a BA (Block Ack) frame. Alternatively, it can be extension of those frames or a new frame which can be defined in the IEEE 802.11 bn amendment.

[0103] After the ICR - typically a SIFS after ICR -, AP1 and the STAs may perform DL / UL OFDMA frame exchange 211 / 223a / 223b among the entire BSS operating channel, here 80MHz bandwidth. STAn uses the secondary 40MHz channel S2a while STA12 uses the primary 40MHz channel S1 a / b. After the frame exchange and no later than the duration of the TXOP 200, STAn switches back to its initial STA operating channel by the channel switch procedure 224a.

[0104] Embodiments below implement TXOP sharing within the two subchannels managed through DSO (the primary and secondary 40MHz channels in the example) to provide more bandwidth usage flexibility and network efficiency. Reversely, an existing TXOP sharing procedure is extended to allow the AP to allocate a portion of an obtained TXOP to more than one station simultaneously, utilizing separated subchannels thanks to the DSO mechanism. Depending on the ability (e.g., hardware capability) of the AP, the AP may be able to perform multiple independent frame exchanges (UL and / or DL) inside its BSS operating channel. For example, the AP may receive one UL frame in the lower 40MHz subchannel and another UL frame in the upper 40MHz subchannel without the synchronization among the two UL frames. Thanks to such independence, P2P traffics may also be conducted by benefiting STAs over their shared subchannel.

[0105] An exemplary TXOP sharing mechanism is the Triggered TXOP sharing (TXS) procedure as introduced in the IEEE 802.11 be amendment. It allows an AP to allocate a portion of an obtained TXOP to one associated non-AP EHT STA for transmitting one or more non-TB PPDUs. There are two modes defined for this TXS procedure:

[0106] Mode 1 : allows the STA to send UL traffic during the shared TXOP, Mode 2: allows the STA to send UL or P2P traffic during the shared TXOP. The AP sends an MU-RTS TXS Trigger frame to trigger the TXS procedure. The MU-RTS TXS Trigger frame is a variant of MU-RTS Trigger frame (Trigger Type subfield set to 3 for “MU-RTS”), which has a non-zero value in the TXS Mode subfield of the Common Info field. The value of the TXS Mode subfield indicates the TXS mode (Mode 1 or Mode 2 above) triggered by the MU-RTS TXS Trigger frame. A single User Info field is provided in the MU-RTS TXS Trigger frame, which User Info field indicates the information for the STA involved in the TXS procedure: AID12 field identifies the STA concerned, RU Allocation field signals the channel where the STA transmits a CTS frame as a response to the MU-RTS TXS Trigger frame, Allocation Duration field informs the time allocated to the STA within the TXOP obtained by the AP, in units of 16us.

[0107] When a STA receives the MU-RTS TXS Trigger frame having the AID12 field of the User Info field set to its own AID, the STA is allowed to use the shared TXOP as specified in the other subfields of the User Infor field (duration and channel bandwidth).

[0108] In other words, the MU-RTS TXS Trigger frame provides a time-sharing scheme of the TXOP to the STA.

[0109] It is apparent that the TXS procedure can be extended to APs, providing that the sharing AP is able to identify another AP through the AID12 field or another field.

[0110] Although the description mainly concentrates on two subchannels for DSO on which separate time-sharing schemes (or schedules) are defined, the invention may be extended to a higher number of subchannels. The skilled person is able to extend the teachings below to multiple STAs that switch to different subchannels, and to an AP that can signal the three of more subchannels and respective time-sharing schemes.

[0111] Figure 3 illustrates, using a flowchart, general operations at the AP (e.g. AP1) to provide DSO TXS opportunities to STAs (including its associated STAs of its BSS or “associated” APs with which it has setup a Multi-AP coordination).

[0112] At step 300, the AP sends, to all or part of the STAs, at least one frame to organise a time-sharing of a transmission opportunity (e.g. TXOP 200) gained by the AP.

[0113] The at least one frame signals a channel switch from the primary subchannel to the secondary subchannel for at least one of the STAs that is initially operating on the primary subchannel only. The targeted subchannel for each STA may be specified.

[0114] The at least one frame also signals separate time-sharing schemes of the TXOP on the primary subchannel and of the TXOP on the secondary subchannel, respectively. Contrary to the conventional use of the time-sharing (TXS) procedure, the AP applies two or more timesharing schemes simultaneously over different frequency bands: the AP organizes independently the time-sharing of the primary subchannel and the time-sharing of the secondary subchannel. As a result, the frame exchanges occurring on the two subchannels can be independent, while simultaneous.

[0115] Next at step, 305, the AP may participate to frame exchanges within the TXOP, either because it keeps timeslots of the TXOP for itself, or because some STAs to which a timeslot has been allocated through the time-sharing schemes exchange frame with the AP. The frame exchanges with the AP may take place on either of the two subchannels or on both simultaneously.

[0116] Figure 4 illustrates, using a flowchart, general operations at the STAs (e.g. STAn, STA12, STA , STA14) to use DSO TXS opportunities provided by the AP.

[0117] At step 400, the STA receives, from the AP, the at least one frame that organises the time-sharing of the transmission opportunity (TXOP 200) gained by the AP.

[0118] At step 405, the STA determines whether a channel switch is required. The STA may check whether the at least one frame signals a channel switch of the STA from the primary subchannel to the secondary subchannel.

[0119] In the affirmative, responsive to the at least one frame, the STA switches at step 410 to the secondary subchannel, i.e., it switches its STA operating channel to the secondary subchannel as signalled in the frame. It is now ready to perform frame exchanges over the secondary subchannel, and then goes to step 415.

[0120] In the negative, the STA remains on its STA operating channel (the primary subchannel) as signalled in the frame. It is now ready to perform frame exchanges over the secondary subchannel, and then goes to step 415.

[0121] At step 415, the STA performs a frame exchange over the secondary channel based on the time-sharing scheme as signalled in the at least one frame.

[0122] For example, the AP may set a TXS mode for the STA allowing it to only perform UL transmissions to the AP (Mode 1) or to have the choice between UL transmissions and P2P transmission (Mode 2), during the timeslot allocated to the STA. Of course, other TXS modes may be defined.

[0123] Figures 5, 6, 7, 8 and 9 each illustrates an exemplary timeline, of a STA in which embodiments of the present disclosure can be implemented. The proposed scenarios use the same BSS operating channel and same primary and secondary subchannels as in Figure 2. Of course, other bandwidths may be used. For example, the AP may have a wider BSS operating channel such as a 160MHz or 320MHz channel and one of the STAs may have different STA operating channel such as a 20MHz or 80MHz channel and so on. In general, new DSO mechanism is implemented and enabled on all of the STAs (including AP1) in these examples.

[0124] The proposed scenarios use a single secondary subchannel in addition to the primary subchannel on which the STAs are initially camped. The invention may be extended to multiple subchannels where STAs can operate simultaneously following the teachings provided through the described scenarios.

[0125] Figure 5 illustrates a first exemplary scenario wherein the channel switch signalling and the time-sharing schemes are provided within one single frame, referenced ICF1 in the Figure. All the STAs therefore obtain all the information at once, for them to decide to switch their STA operating channel to the secondary subchannel S2a or to remain on the first subchannel S1 a / b, and for them to know when they can conduct their own frame exchanges. In this scenario also, a time-sharing scheme on the secondary subchannel allocates the secondary subchannel to an associated STA for peer-to-peer (P2P) exchange with another STA of the same BSS. The AP being able to reach both peer stations, it is worth switching their P2P exchange over the secondary subchannel in order to keep the primary subchannel - on which the other STAs of the BSS are - for intra-BSS communications. This is particularly beneficial for intra-BSS communications with STAs of the BSS that are unable to switch to the secondary subchannel.

[0126] As shown in the Figure, AP1 obtains a TXOP 500 and share it to STAn for UL communications and to STA12 or STA14 (forming P2P Groupl 102) for P2P communication. The obtention of TXOP 500 can be made through ICF1 510 discussed below or, in variants, with a prior frame. In these variants, the AP therefore sends a frame prior to the at least one frame in order to reserve the medium for the TXOP. An exemplary prior frame is the CTS-to-self frame.

[0127] ICF1 510 includes both the information for the channel switching of the concerned stations and the information for time-sharing on each subchannel (e.g., TXS procedure on each subchannel).

[0128] In the scenario, AP1 , via ICF1 510, indicates the channel switch to the upper 40MHz channel S2a for STA12 and STA14 and no channel switch for STAn. AP1 also indicates the timesharing schemes (TXS mode and duration - here the entire TXOP duration) to each STA: e.g., Mode 1 to STA11 to allow UL communications and Mode 2 to STA12 / STA14 to allow P2P communications. In variants, in particular to force STA12 / STA14 to perform P2P communications (Mode 2 allows both P2P and UL communications), a third mode (e.g., Mode 3 with TXS Mode subfield set to ‘3’) dedicated to P2P traffic only can be defined.

[0129] As apparent from the description below, in particular with reference to Figures 11a to 11 d, ICF1 510 may include multiple User Info fields that each signals to a specific STA the subchannel on which to operate. In that way, if it is different from the STA operating channel (as for STA12), the signalling corresponds to an indication to switch channel. If it is the same as the STA operating channel (as for STAn), the STA remains on its STA operating channel without switching.

[0130] Responsive to the indication, both STA12 and STA14 switch (521 b / 521 c) to the same secondary subchannel S2a to be able to perform their P2P communications over the secondary subchannel. As apparent from the description below, in particular with reference to Figures 11a to 11d, padding fields are provided in ICF1 , preferably after a frame check sequence (FCS) subfield in the Common Info field, to give enough time to switching STAs (STA12 and STA14) to effectively switch to the secondary subchannel.

[0131] On the other hand, STAn does not have to switch, and remains active on the primary subchannel S1 a.

[0132] From now then, the STAs are ready to perform their communications.

[0133] However, to warn the AP they are ready, they may respond to ICF1 in embodiments. For instance, after switching to the secondary subchannel, STA12 and STA14 may send to AP1 a response ICR 522b / 522c to ICF1 over the allocated secondary subchannel - i.e. the subchannel over which they intend to communicate. Similarly, STAn can send to AP1 a response ICR 522a to ICF1 over the primary subchannel. The responses ICR may be a CTS frame, ACK frame, a BA (Block-Acknowledgement) frame or any other control frame including any new control frame that could be defined in the forthcoming IEEE 802.11 bn amendment. They are sent e.g., a SIFS after ICF1 . Correspondingly, the AP receives a response from one or more STAs over the secondary subchannel and another response from another STA over the primary subchannel.

[0134] The communications then take place e.g., a SIFS after ICR (or ICF1 in case no response ICR is required): UL communications 523a for STAn over the primary subchannel S1 a and P2P communications 523b / c between STA12 and STA14 over the secondary subchannel S2a.

[0135] Since the UL traffic 523a and the P2P traffic 523b / 523c are not pre-corrected in a way such as done for the TB-PPDUs sent in UL OFDMA, they may interfere one each other especially near the boundary between the primary and secondary subchannels. To avoid or reduce the risks of interference, one or more RUs near the boundary may be unused to form guard RUs which are used for protection purposes. In other words, whatever the station (AP or STA) using one of the primary and secondary subchannels for a frame exchange, a resource unit of the used subchannel in the vicinity of the other subchannel remains unused during the frame exchange. As an example, performing the frame exchange (P2P communication in the scenario) over the secondary channel S2a includes not using a resource unit of the secondary subchannel in the vicinity of the primary subchannel. Of course, the guard RU or RUs may be in the primary subchannel or in the secondary subchannel or spread over both subchannels.

[0136] To illustrate, the upper 20MHz channel of the primary subchannel S1 a used for UL communications 523a or the lower 20MHz channel of the secondary subchannel S2a used for P2P communications 523b / 523c may be reserved as a guard 20MHz band. Alternatively, a subpart (adjacent to the boundary) of the 20MHz channel can be used as guard RU, to avoid losing an entire 20MHz bandwidth.

[0137] Alternatively to the guard RUs, AP1 may require pre-correction of transmission time, frequency, sampling symbol clock, and power (as usually applied for PPDUs in response to a trigger frame) to be applied by the STAs for UL and P2P traffics during the TXOP sharing.

[0138] STA12 and STA14 can switch back (524b / c) to the primary subchannel at the end of the TXOP sharing, e.g., after a time-sharing duration signalled in ICF1 510.

[0139] Figure 6 illustrates a second exemplary scenario similar to the one of Figure 5, except that the channel switch signalling is provided within a first frame, referenced ICF1 in the Figure, and the time-sharing schemes are respectively provided in multiple second and separate frames, referenced ICF2a and ICF2b in the Figure. The same references throughout the Figures correspond to the same steps.

[0140] AP1 divides the ICF of Figure 5 into two ICFs: ICF1 610 and ICF 2 which further consists of ICF2a 611 a and ICF2b 61 1 b. By dividing the ICF into two ICFs, AP can divide the contents included in the ICF into two. ICF1 contains the information for the channel switch while ICF2a / b split the information about the time-sharing schemes (e.g., for TXS procedure). Note that more than two ICF2x can be sent in case there are multiple secondary subchannels that are used in addition to the primary subchannel.

[0141] ICF1 is transmitted over the primary and secondary subchannels. ICF1 610 from AP1 indicates different channels for each STA where to reply to ICF1. An exemplary ICF1 610 is described below with reference to Figures 12a and 12b. A variant of ICF1 610 is described below with reference to Figures 12e.

[0142] In the scenario of the Figure, ICF1 610 signals a first subpart of the secondary subchannel S2a over which a first STA has to respond to ICF1 (e.g. upper 20MHz channel for STA12) and signals a second and distinct subpart of the secondary subchannel over which a second STA has to respond to ICF1 (e.g. second upper 20MHz channel for STA14) and signals the primary subchannel S1 a over which a third STA has to respond to ICF1 (e.g. lower 40MHz channel for STAn).

[0143] The signalling of these “responding” channels forms an indication of channel switching (or not), if the responding channel is not included in the STA operating channel (as for STA12), the signalling corresponds to an indication to switch channel. If it is included (as for STA11), the STA remains on its STA operating channel without switching.

[0144] The STAs targeted by ICF1 610 therefore respond (e.g., a SIFS after ICF1 610) with ICR1 over their allocated responding channel: STAn over primary subchannel S1 a (622a), STA12 (after channel switching 521 b) over upper 20MHz channel (622b) and STA14 (after channel switching 521 c) over second upper 20MHz channel (622c).

[0145] This responding scheme enables AP1 to know whether each STA has successfully switched or remained in the indicated subchannel and is now ready for the sequential TXS procedure. Indeed, the AP can build the time-sharing schemes on the primary and secondary subchannels based on responses to ICF1 610 received from the STAs on the primary and secondary subchannels respectively. Where a targeted STA does not respond, AP1 may not schedule it for communication through the time-sharing schemes.

[0146] In embodiments, in case a STA does not response, AP1 can transmit another ICF1 to that missing STA to retry.

[0147] The responding scheme is optional, meaning ICF2 (below) may directly follow ICF1 . After the ICF1 / ICR1 exchange, STAs are camped on the indicated subchannels: STA11 on the primary subchannel S1 a, STA12 and STA14 on the secondary subchannel S2a. Thanks to this, AP1 can divide the content of ICF2 into two: ICF2a 61 1 a on the primary subchannel, dedicated to STAn and ICF2b 611 b on the secondary subchannel, dedicated to STA12 and STA14. This can reduce the length of ICF2 frames since the User Info fields only for those STAs camped on the corresponding subchannel (where ICF2 is sent) are included. For example, ICF2a 611 a contains one User Info field of STAn and ICF2b 611 b contains two User Info fields, one for STA12 and the other for STA14. An exemplary ICF2a / b 61 1 a / b is described below with reference to Figures 12c and 12d. ICF2a 61 1a and ICF2b 611 b are transmitted over their respective subchannel only.

[0148] ICF2a 611 a and ICF2b 611 b does not have the same frame length due to the difference of content. Padding bits or a dummy User Info field (which can be assimilated to padding bits) may be added to ICF2a (or ICF2b) to align its length with the one of ICF2b (or ICF2a). In other words, at least one ICF2 frame providing a time-sharing scheme includes padding to have the same length as another ICF2 frame providing another time-sharing scheme.

[0149] The STAs may respond to their ICF2 frame by sending an ICR2 frame over their respective subchannel: STA12 and STA14 send ICR2 622b / 622c over allocated secondary subchannel S2a while STAn sends its response ICR2 622a over the primary subchannel S1 a.

[0150] Figure 7 illustrates a third exemplary scenario similar to the one of Figure 5, except that the ICF1 frame defines multiple TXOP timeslots within the TXOP and signals different timesharing schemes for the primary and secondary subchannels over the multiple TXOP timeslots, rather than a single timeslot. The same references throughout the Figures correspond to the same steps.

[0151] The scenario of Figure 7 can be extended to the multiple ICF scheme of Figure 6 without difficulties. However, for conciseness reasons, the description below only considers the single ICF scheme.

[0152] The multiple TXOP sharing timeslots can be assigned to different purposes. For example, TXOP 500 is divided, by ICF1 710, into three TXOP sharing timeslots TXOP1 701 , TXOP2 702 and TXOP3 703.

[0153] AP1 can allocate, via ICF1 710, different traffics for each TXOP sharing timeslot. In such a manner, AP1 can flexibly schedule multiple TXOP sharings with one ICF1 710. For example, TXOP1 701 is allocated for UL traffic 523a for STAn in the primary subchannel S1 a and for P2P traffics 523b / 523c in the secondary subchannel S2a. TXOP2 702 is allocated back to AP1 for DL traffic or for random access usage 711 . Here, one of the time-sharing schemes gives back the primary and secondary subchannels to the AP during one of the multiple timeslots. TXOP3 703 is allocated for two UL traffics 725a and 725b. One UL traffic is allocated to STAn in the primary subchannel S1 a, while the other UL traffic is allocated to STA12 in the secondary subchannel S2a. Of course, another order between the timeslots as well as a different number of timeslots and different allocated traffics can be implemented.

[0154] Figures 11a and 12c provide exemplary signalling of the multiple TXOP sharing timeslots, in particular in the Common Info field of a trigger frame.

[0155] Figure 8 illustrates a fourth exemplary scenario similar to the one of Figure 5, except that the P2P group involved is no longer the P2P Groupl 102 but the P2P Group2 103 comprising STA21 which does not belong to BSS1 101 (i.e., AP1 cannot control STA21, which may not be within its communication range). The same references throughout the Figures correspond to the same steps. The scenario of Figure 8 can be extended to the multiple ICF scheme of Figure 6 as well as the multiple TXOP timeslot scheme of Figure 7. However, for conciseness reasons, the description below only considers the single ICF / single TXOP timeslot scheme.

[0156] As P2P Group2 103 involves P2P traffic where one of the peer STA is not associated to AP1 , AP1 decides to allocate (via ICF1 810) the P2P traffic to the primary subchannel S1 b of STA as it is not possible for AP1 to know whether STA21 has transmission capabilities on the secondary subchannel and it is not possible for AP1 to signal to STA21 to switch to the secondary subchannel S2a. In other words, a time-sharing scheme on the primary subchannel allocates the primary subchannel to a STA of the BSS for peer-to-peer exchange with a STA not belonging to the BSS. As a result, STA13 and STA21 can perform P2P traffic exchanges 823b / 823c.

[0157] AP1 therefore allocate the other traffic (UL traffic for STAn in this case. However, it could be P2P traffic for example through P2P Groupl 102) to the secondary subchannel S2a. The concerned station switches (821 a) to the secondary subchannel to perform its own frame exchange 823a, before switching back (824a) to its initial STA operating channel (here primary subchannel S1 a).

[0158] The responses 822a / 822b to ICF1 810 are optional.

[0159] Figure 9 illustrates a fifth exemplary scenario similar to the one of Figure 8, wherein the two P2P groups, P2P Groupl 102 and P2P Group2 103, are involved for P2P exchanges over the primary and secondary subchannels respectively. The same references throughout the Figures correspond to the same steps.

[0160] As for Figure 8, the scenario of Figure 9 can be extended to the multiple ICF scheme and / or the multiple TXOP timeslot scheme, although the description below only considers the single ICF / single TXOP timeslot scheme.

[0161] As for Figure 8, P2P Group2 103 comprising un-associated STA21 is allocated the primary subchannel S1 b, while P2P Groupl 102 comprising only associated STAs is allocated the secondary subchannel S2a since all these associated STAs can be controlled by AP1 (via ICR1) to switch their operating channel.

[0162] In the preceding scenarios, AP1 may individually notify the STAs (STAn, STA12, STA13, STA14) and allocate them TXOP sharing timeslots for transmission. In these scenarios, the time-sharing scheme may therefore signal an Associated Identifier (AID) of each STA concerned, typically in the User Info field corresponding, more specifically in the AID12 subfield therein.

[0163] In the present scenario of Figure 9, AP1 allocates a TXOP sharing timeslot not only for one STA but for a P2P Group. The time-sharing scheme may therefore signal an identifier of the P2P Group concerned.

[0164] Indeed, in the TXS procedure in IEEE 802.11 be D6.0 amendment, when a STA is allocated a TXOP sharing for Mode 2, the STA is only allowed to send UL or P2P traffic to the other STA. However, it sounds more flexible to allocate the TXOP sharing timeslot to the P2P Group rather than the STA, and let the STA inside the P2P Group share the TXOP among them rather than being forced to send P2P traffic.

[0165] The response ICR 822a / 822b can then be sent from at least one of the STAs involved in the P2P Group concerned.

[0166] A Stream Classification Service (SCS) Request frame or any other frame can be further extended to include information on whether all the peer STAs inside the P2P Group are associated to the same AP (that sends ICF1 820) or not.

[0167] Figures 10a and 10b illustrate, using flowcharts, steps at an AP to conduct DSO TXS operations according to embodiments of the disclosure. Figure 10a shows a flowchart when using two ICF frames (ICF1 and ICF2), while Figure 10b shows a flowchart when using a single ICF frame (ICF1). Dashed blocks show optional steps.

[0168] The processes start with step 1000a / 1000b during which the AP gathers information about the stations, in particular its associated STAs. All or part of this step can be performed early in advance to the other steps.

[0169] Exemplary information the AP can gather include one or more of the following information:

[0170] DSO capability of the STA(s),

[0171] Traffic Characteristics of the STA(s), Subchannel status.

[0172] The DSO capability of a STA may include several information. For example, whether the STA supports DSO itself or not, which subchannels the STA can switch to, the channel switch delay of the STA. These items of information may be exchanged between the AP and the STA during the association procedure and may be updated after the association.

[0173] Basic capabilities such as the support of the DSO mechanism itself may be indicated in a capability element such as an UHR Capabilities element which may be included in the Management frames such as Beacon / Probe Request / Probe Response / (Re)association Request / Response / Action frames.

[0174] Further details of the DSO capability such as the supported subchannels for channel switch and / or the channel switch delay can be also included in the same UHR Capabilities element, or can be indicated in a different element such as dedicated DSO element, included in the Management frames as well.

[0175] An update of the DSO capability and associated details may be notified using the same elements, for example exchanged through Action frames. Alternatively, the update can be indicated in a field in the MAC header such as the A-Control field to notify the updates in a more dynamic manner.

[0176] The Traffic Characteristics of a STA may include information regarding characteristics of the UL / DL / P2P traffic the STA is involved in. One means to share this information from the STA to the AP is the (EHT) SCS procedure defined in the IEEE 802.11 be D6.0 amendment. The EHT SCS procedure allows an EHT STA to inform its associated AP for the QoS characteristics of UL or P2P traffics. This is informed through the QoS Characteristics element included in the SCS Request frame sent by the STA. QoS Characteristics element includes information such as: a direction of the traffic: UL / DL / P2P in the Direction subfield of the Control Info field, a requested service interval by signalling the minimum value and the maximum value respectively in the Minimum Service Interval field and the Maximum Service Interval field, a requested lowest data rate signalled in the Minimum Data Rate field, a target delay bound (maximum amount of allowed time till the completion of the successful transmission) signalled in the Delay Bound field, and so on.

[0177] The STA sends a SCS Request frame to its associated AP. Next, if the AP accepts the request, the AP sends a SCS Response frame with its Status field set to SUCCESS. With this SCS Request / Response negotiation, the AP can know the characteristics of the STA traffics which helps the scheduling of the DSO TXS procedure, i.e., the preparation of the time-sharing schemes.

[0178] However, the SCS Request frame may lack information about the peer STA that the STA wants to exchange P2P traffic with. An identity of the peer STA, such as its MAC address or the information whether the STA is associated to the same AP (that sends the ICF1 frame) or not, can be provided to the AP by extending the SCS Request frame or any other frames.

[0179] Of course, any other means to share the traffic characteristic, for example an information exchange using the application layer, are also applicable and not limited to the SCS Request / Response discussed above. Also, similar information may be exchanged between APs participating in the same Multi-AP coordination.

[0180] As far as the subchannel status is concerned, the AP may monitor each subchannel dynamically or may have some knowledge for an upcoming or a static unavailability of the subchannel. The subchannel may be predefined (e.g. primary 40MHz channel and secondary 40MHz channel) or result from the declaration of the supported subchannels by the STAs, e.g., during their association to the AP.

[0181] A conventional CCA (Clear Channel Assessment) function may be used to dynamically monitor the BSS operating channel. If the AP obtains the access for the whole bandwidth, the AP may reserve the TXOP for the entire BSS operating channel by sending the first ICF among the entire channel (whole bandwidth).

[0182] Even if the AP obtains the TXOP, there may be some interference from hidden nodes on STA side. In this case, the STAs may not have access to the target DSO subchannel. To avoid this issue, the AP may obtain further subchannel status information from the STA(s) themselves. This can be an implicit information obtained by the AP from its STA(s). For example, if the candidate subchannel for DSO for a specific STA does not work under certain conditions (e.g., X times in sequential Y trials), the AP may inferthatthe STA is facing interference on the subchannel and it is better to allocate a different subchannel to that STA. Alternatively, preferred subchannels or some unavailability information for some subchannels can be reported from the STA(s) to the AP. As for the DSO capability exchange, such reporting information can be included in the UHR Capabilities element or in the other element such as dedicated DSO element and be negotiated during the association procedure or be updated using an Action frames or Control fields in the MAC header as well.

[0183] When the necessary information has been gathered at step 1000a / 1000b, the AP determines at step 1001 a / 1001 b which STA(s) to involve in the next TXOP based on the gathered information and the respective subchannel the STA(s) will operate on. This determination based on the gathered information is optional, meaning any other way to assign the STA(s) to the subchannels, e.g., a predefined assignment scheme, may be used.

[0184] Next, at step 1002a / 1002b, the AP sends ICF1 to the STA(s). ICF1 may be broadcast to the STA(s) or multicast to the specific targeted STA(s).

[0185] ICF1 may initiate the TXOP. In variants, the AP may send a prior frame (for example a CTS-to-self frame) before ICF1 to obtain the TXOP. In this case, the ICFs are not required to initiate the TXOP.

[0186] As apparent from the scenarios discussed above, ICF1 sent at step 1002a indicates which STA(s) to operate on which subchannel, hence signals a channel switch from the primary subchannel to the secondary subchannel for some of these STAs.

[0187] As apparent from the scenarios discussed above, ICF1 sent at step 1002b further indicates the TXOP sharing schedules (hence time-sharing schemes) organizing the time-sharing of the subchannels after the ICF during the TXOP (or TXOP timeslots).

[0188] Next at step 1003a / 1003b, the AP receives the ICR frames from all or part of the targeted STA(s) to confirm whether they have successfully switched to their subchannel (where applicable) and are now ready for the following TXOP sharing on their respective subchannel. Step 1003a / 1003b can be omitted when the TXOP sharing on the subchannels start without STA confirmation, to reduce the overhead.

[0189] However, in preferred embodiments, the ICR is expected by the AP. Indeed, the ICR transmission from the STA side also functions to set the NAV at the hidden nodes, hence to protect the medium. Especially for the process of Figure 10a (use case with ICF1 and ICF2), the AP can adjust the TXOP sharing scheduling (transmitted in ICF2) based on the ICR received, in particular to avoid scheduling a STA that has not positively responded to ICF1 .

[0190] Next, at step 1004a (use case with ICF1 and ICF2), the AP sends the ICF2 frames, e.g. ICF2a and ICF2b, that each comprises the time-sharing scheme (TXOP sharing schedule) for the corresponding DSO subchannel (i.e. , the subchannel over which ICF2 is sent).

[0191] As mentioned above, the AP may prepare the time-sharing schemes based on the ICR responses received from the targeted STA(s). Next, at step 1005a (still use case with ICF1 and ICF2), the AP optionally receives responses (ICR2) from the allocated STA(s) to confirm the successful reception of ICF2 on STA side. This step is optional and the ICR2 responses may be skipped to reduce the overhead.

[0192] At this point, all the stations in both methods are camped on their subchannels and know when they are allowed to perform a frame exchange.

[0193] Then, at step 1006a / 1006b, the AP may participate to frame exchanges based on the time-sharing schemes shared at step 1004a or 1002b. Indeed, the AP may be involved in UL transmissions over the primary channel (523a in Figure 5 or 6 or 7, 725a in Figure 7) or over the secondary channel (725b in Figure 7, 823a in Figure 8), in DL transmissions (71 1 in Figure 7), or may not be involved at all during the TXOP or TXOP timeslot (Figure 9).

[0194] Figures 10c and 10d illustrate, using flowcharts, steps at a STA performing DSO TXS operations under the control of an AP, according to embodiments of the disclosure. Figure 10c shows a flowchart when using two ICF frames (ICF1 and ICF2), while Figure 10d shows a flowchart when using a single ICF frame (ICF1). Dashed blocks show optional steps.

[0195] First at steps 1001 c / 1001 d , the STA may provide supportive information to assist the DSO TXS scheduling by the AP. This corresponds to the exchange of steps 1000a / 1000b discussed above. For example, the STA may provide one or more information related to the DSO capability of the STA, traffic characteristics of the STA, subchannel status around the STA.

[0196] Next, at step 1002c / 1002d, the STA receives ICF1 from the AP.

[0197] At test 1003c / 1003d, the STA determines whether it has to perform a channel switch of its STA operating channel from the primary subchannel to the secondary subchannel. This determination is based on the channel switch signalling of received ICF1.

[0198] For example, the STA determines it has to switch if ICF1 allocates it a responding channel in the secondary subchannel S2a or if ICF1 includes a User Info field having an AID12 set to the AID of the STA and a RU Allocation field targeting the secondary subchannel.

[0199] In the affirmative, the STA proceeds to step 1004c / 1004d where it performs the channel switch. After that, the STA is camped on the secondary subchannel and the STA goes to step 1005c / 1005d.

[0200] In the negative (e.g., the STA remains on the primary subchannel), the STA proceeds with step 1005c / 1005d.

[0201] At test 1005c / 1005d, the STA checks whether it is ready for the following DSO TXS procedure.

[0202] This test may include two subtests.

[0203] First, the STA checks whether the channel switch operated at step 1004c / 1004d is successfully completed or not. This is only applicable for STAs that resulted yes in test 1002c / 1002d. If the channel switch has failed for any reason, the STA is not ready for following DSO TXS procedure so the process goes to step 101 1 c / 1011d to not respond (ICR) to the AP.

[0204] Otherwise (successful channel switch or no channel switch), the STA further checks its Basic NAV (Network Allocation Vector) on the concerned subchannel (primary or secondary subchannel) and / or performs the CCA in the concerned subchannel, in particular in each of its 20MHz channels (if indicated in ICF1). If the Basic NAV or the subchannel is not idle, the STA is not ready for the following DSC TXS so the process goes to step 1011 c / 1011d. Otherwise, the STA is ready for the concerned subchannel and the process goes to step 1006c / 1006d.

[0205] In particular, in case of no channel switch, the STA may first check its Basic NAV for the primary subchannel, and perform the CCA using energy detect on the 20MHz channels of the primary subchannel (allocated by ICF1) only in case the Basic NAV is idle. Hence, if the primary subchannel has been idle for a SIFS duration after ICF1 , the STA is ready for the subchannel.

[0206] In case of channel switch, the STA is usually not aware of its Basic NAV for the secondary subchannel. Therefore, the STA only checks the CCA using energy detect for the all the 20MHz channels of the secondary subchannel allocated by ICF1. Lower ED threshold (than the default threshold) such as -72dBm may be applied here due to the blindness of the switched subchannel. If the secondary subchannel has been idle for a SIFS duration after ICF1 for the secondary subchannel, the STA is ready forthe following DSC TXS procedure forthe subchannel.

[0207] At step 1006c / 1006d, the STA sends response frame ICR / ICR1 to the AP. This response may indicate the readiness of the STA as determined at test 1005c / 1005d for each 20MHz channel forming the concerned (primary of secondary) subchannel.

[0208] Next, at step 1007c (use case with ICF1 and ICF2), the STA receives ICF2 (either ICF2a or ICF2b depending on which subchannel it is camped) from the AP. ICF2 includes the time-sharing scheme (TXS schedule information) applicable forthe subchannel on which the STA camps.

[0209] At test 1008c, the STA optionally checks if the scheduled DSO TXS procedure is acceptable for the STA and the STA is ready for the following DSO TXS procedure. The STA may reject the schedule for any reason. Or, the STA may observe unexpected interference or unexpected issue so that the scheduled DSO TXS procedure is no more ready. In this case, the process goes to step 1011 c not to respond to the AP. In variants, the process goes to step 1009c where the STA sends a response (ICR2) to ICF2 to indicate the rejection of the time-sharing scheme (TXS schedule) proposed in ICF2 before proceeding to step 1011 c. In ICR2, the STA may include the rejection reason in a Status Code field.

[0210] If the STA is ready at test 1008c, the process goes to step 1009c where the STA sends ICR2 to the AP to acknowledge ICF2 and to declare its readiness of the following DSO TXS procedure. This means the STA accepts the proposed time-sharing scheme.

[0211] At this point, all the stations in both methods are camped on their subchannels, are ready for DSO TXS procedure and know when they are allowed to perform a frame exchange.

[0212] Then, at step 1010c / 101 Od, the STA performs the frame exchanges based on the appropriate time-sharing scheme (TXS schedule) provided by ICF1 (Figure 10d) or ICF2 (Figure 10c). Next, when the TXOP or timeslot allocated to the STA ends, at step 1011 c / 101 1 d, the STA performs a channel switch back to its initial STA operating channel, e.g., primary subchannel Sl a in the scenarios above, if it had switched at step 1004c / 1004d.

[0213] Figures 11a, 11 b, 11c and 11d illustrate an exemplary frame format for a frame signalling both channel switches for the STAs and time-sharing schemes, i.e. , a frame such as ICF1 in the single-ICF scenarios.

[0214] In embodiments, ICF1 is a Trigger frame in the meaning of the IEEE 802.11 family of standards. The Trigger frame is indeed a good candidate for ICF1 since it is sent from the AP to one or more STA(s) to trigger procedures, here DSO TXS procedures.

[0215] This exemplary frame format proposed in these Figures is therefore based on a Trigger frame format.

[0216] As shown in Figure 11a, an extended MU-RTS TXS Trigger frame is proposed.

[0217] In the IEEE 802.11 be amendment, the MU-RTS TXS Trigger frame is introduced as a variant of MU-RTS Trigger frame (Trigger Type subfield set to value 3, corresponding to MU- RTS), wherein the TXS Mode subfield in the Common Info field is not set to 0.

[0218] The top of Figure 11a shows, under reference 1100, the basic format of a Trigger frame wherein a padding field 1108 is added after the frame check sequence (FCS) field 1107. Padding field 1108 may replace existing Padding field 1106. In variants, Padding field 1106 may be kept but unused (or limited to its minimum size).

[0219] Fields 1101 to 1 107 are already introduced in the IEEE 802.11 be D6.0 amendment. To be noted that Duration field 1102 indicates the length / duration of TXOP 500.

[0220] Padding field 1108 is located after the FCS (Frame Check Sequence) field 1107 to allow the STA(s) to perform their channel switch to the secondary subchannel without waiting for the reception of Padding field 1108. Indeed, without Padding field 1108, the STA(s) have to check the validity of the received packet using all the fields till FCS field 1107 including Padding field 1106. So the STA(s) cannot start their channel switch as long as they have not received Padding field 1 106 and FCS field 1107.

[0221] Trigger frame also includes Common Info field 1110 which is common for all STAs that are involved in the triggered procedure, and User Info List field 1105 which includes two or more User Info fields to indicate dedicated information for each concerned STA. At least one User Info field is for a STA (or P2P Group) that has to remain on its initial STA operating channel (the primary subchannel). At least one User Info field is for a STA (or P2P Group) that has to switch its STA operating channel to the secondary subchannel. The User Info fields provide the indication (signalling) regarding the channel switch (e.g., through a target subchannel for each STA) and the time-sharing schemes.

[0222] As proposed in the Figure, Common Info field 1110 comprises:

[0223] Trigger Type field 11 11 set to 3 to indicate a MU-RTS Trigger frame,

[0224] Triggered TXOP Sharing (TXS) Mode field 1118 set to a non-zero value to indicate the MU-RTS Trigger frame is a MU-RTS TXS Trigger frame. In the IEEE 802.1 1 be D6.0 amendment, Mode 1 and Mode 2 are defined as TXS modes. In embodiments as shown in Figure 11 b, a third mode, Mode 3, is proposed with value 3 in the TXS Mode field, to declare the frame as a new Extended MU-RTS TXS Trigger frame, in particular a DSO TXS trigger frame,

[0225] TXOP duration present field 1112 to indicate the presence of TXOP duration fields 1 119. For example, if it is set to 1 , it indicates the presence of TXOP duration fields. If set to 0, it indicates no TXOP duration field is provided, Number of TXOP duration fields field 1113. If the TXOP duration present field 1112 is set to 0, field 1113 is reserved. Otherwise, it indicates the number of TXOP duration fields 11 19. For example, if it is set to a (0 <= a <= n - 1), it indicates a + 1 TXOP duration fields 1 119. The bit size of the Number of TXOP duration fields field 1 113 is designed to be long enough to express the predefined maximum number n - 1 . In other words, this field signals the number of TXOP timeslots 701-703 in the multiple TXOP timeslots (Figure 7);

[0226] TXOP duration fields 1119. Each TXOP duration field 1119 indicates the allocated time of each TXOP sharing timeslot in a sequential manner. It can be a nine-bit field and the time indicated therein can be in units of 16 ps (of course other bit sizes and / or time units are applicable). In other words, these fields signal the durations of the multiple TXOP timeslots respectively. For example, in the scenario of Figure 7, the first TXOP duration field 1 119 indicates the duration of the first TXOP sharing timeslot TXOP1 701 , the second TXOP duration field 1119 indicates the duration of TXOP2 702, and the third TXOP duration field 1119 indicates the duration of TXOP3 703. The interval between two successive TXOP sharing timeslots can be a predefined value (e.g., a SIFS or 0), or can be further indicated as an additional field in the Common Info field. In this way, Common Info field indicates the time information of the TXS schedule.

[0227] Therefore, TXOP duration present field 1112, Number of TXOP duration fields field 1113 and TXOP duration fields 11 19 together allow, in Common Info field 1110, to define multiple TXOP timeslots within the TXOP and signal different time-sharing schemes for the primary and secondary subchannels over the multiple TXOP timeslots.

[0228] The other fields 1114, 1115, 1116 and 1117 are of less interest and keep their usual meaning (i.e., from the 802.11 family of standards).

[0229] As shown in Figure 11d, a User Info field 1130 of the User Info List field 1105 provides the target subchannel for a concerned STA as well as time-sharing scheme information. Format 930a shows a HE variant User Info field format while format 930b shows an EHT variant User Info field format. An UHR variant User Info field format (corresponding to the forthcoming IEEE 802.11 bn amendment) may also include the subfields discussed below.

[0230] AID12 subfield 1131 a / 1131 b identifies the STA concerned by the User Info field 1130a / 1130b, or it indicates the allocation for Random Access RUs for associated or unassociated STAs. It can further indicate the Unallocated RU or the start of padding field: for example, AID12 subfield set to 4095 may signal that the remaining subfields in the User Info field are not present and padding field 1106 immediately follows.

[0231] RU Allocation field 1132a / 1132b is reused to indicate the allocation of the resource units to the STA indicated in the AID12 field 1131 a / 1131 b during the TXOP or TXOP sharing timeslot concerned by the User Info field (specified in TXOP ID subfield 1133a / 1 133b discussed below). RU Allocation field 1132a / 1132b is therefore used to indicate the STA whether to switch its STA operating channel to a secondary subchannel or not during the following TXS procedure. If the allocated RU is inside its initial STA operating bandwidth, the STA does not have to switch. Otherwise, the STA performs the channel switch to the secondary subchannel that includes the allocated RU. In other words, RU Allocation field 1132a / 1132b signals the primary or secondary subchannel on which the concerned STA has to operate.

[0232] PS160 field 1137b is used to indicate the 320MHz allocation as it is in IEEE 802.11 be D6.0 amendment.

[0233] Compared to the conventional (IEEE 802.11 be D6.0 amendment) User Info field of a MU-RTS TXS Trigger frame, the following three subfields are added to convey more information about the DSO TXS procedure:

[0234] TXOP ID subfield 1 133a / 1133b to indicate the ID of the TXOP sharing timeslots (if multiple) concerned by the User Info field, from amongst multiple TXOP timeslots within the TXOP. For example, using the example of Figure 7, if this User Info field informs about TXOP1 701 , the TXOP ID subfield is set to 0. If it informs about TXOP2 702, the TXOP ID subfield is set to 1 . If it informs about TXOP3 703, the TXOP ID subfield is set to 2. The size of the TXOP ID subfield 1133a / 1133b may be identical to size of Number of TXOP duration fields field 1113 (x) to express the maximum number of the TXOP sharing timeslots.

[0235] Extended Sharing Mode subfield 1134a / 1134b to indicate a DSO TXS mode for the TXOP sharing timeslot. This subfield signals a transmission mode in the allocated primary or secondary subchannel. As shown in Figure 11c, exemplary DSO TXS modes include: o Mode 0 wherein the concerned TXOP sharing timeslot is allocated back to the TXOP holder so that the TXOP holder can send DL link frames using the allocated resources during the TXOP sharing timeslot, o Mode 1 wherein the concerned TXOP sharing timeslot is allocated as it is in the TXS Mode 1 of IEEE 802.11 be amendment: the allocated STA (specified in AID12 field 1 131 a / 1131 b) can send uplink traffics during the timeslot using the allocated resources, o Mode 2 wherein the concerned TXOP sharing timeslot is allocated as it is in the TXS Mode 2 of IEEE 802.11 be amendment: the allocated STA can send uplink traffics or peer-to-peer traffics during the timeslot using the allocated resources, o Mode 3 wherein the concerned TXOP sharing timeslot is allocated only for peer-to-peer traffics. The allocated STA can send peer-to-peer traffics during the timeslot using the allocated resources. o Mode 4 to 7 may be reserved.

[0236] Trigger dependent User Info subfield 1136a / 1 136b to further provide detail information of the TXS procedure.

[0237] In this way, the User Info fields 1130a / 1130b inform the STAs about their resource allocation (hence whether they have to perform a channel switch or not) and the extended TXS mode to use for the specific TXOP sharing timeslot.

[0238] Figures 12a, 12b, 12c, 12d and 12e illustrate exemplary frame formats for a frame signalling channel switches for the STAs and a second frame signalling time-sharing schemes, i.e. , frames such as ICF1 and ICF2 in the two-ICF scenarios. The same explanations as above (Figures 11a-d) apply except for specific indications below.

[0239] As ICF1 only aims at signalling the required channel switches, the proposed frame format for ICF1 1200 (still as a Trigger frame, in particular a MU-RTS TXS Trigger frame as in Figures 11a-d) no longer includes TXOP duration present field 1112, Number of TXOP duration fields field 11 13, TXOP duration fields 11 19. All those fields are reserved as 1212 and 1217 as shown in Figure 12a.

[0240] To indicate that the Trigger frame signals channel switches to the STA(s), a new Trigger frame variant can be defined such as Channel Switch Trigger frame with a new Trigger Type subfield value such as 9 indicated in Trigger Type field 1011. Alternatively, the MU-RTS Trigger frame type (Trigger Type subfield value equal to 3) can be reused and one of the reserved bit 1212 or 1217 can be used to indicate the Channel Switch Trigger frame as a variant of the MU-RTS Trigger frame.

[0241] RU allocation field 1232 is used to indicate where the STA is supposed to send the ICR back to the AP. This field 1232 therefore indicate the target subchannel, hence whether the STA has to switch its STA operating channel or not.

[0242] Figure 12b shows an exemplary format of a User Info field 1050 / 1060 of the User Info List 1205. AID12 field 1231 and PS160 field 1238 are used as it is in the IEEE 802.11 be D6.0 amendment. RU allocation field 1232 and Trigger dependent User Info 1237 are used as explained above (Figure 11 d). Allocation Duration field 1235 may be used to indicate the overall duration of the TXOP. For example, it indicates the length of TXOP 500.

[0243] Figure 12c shows an exemplary format for ICF2. The same format as shown in Figure 11a is reused. The difference compared to the single-ICF mode comes from the User Info field as shown in Figure 12d wherein RU allocation field 1132a / 1132b is omitted because the information of the allocated subchannel is already indicated in ICF1. Figure 12e shows a variation of the User Info field format of Figure 12b (i.e., for ICF1 in the two-ICF scenarios). The User Info field includes here an additional Subchannel Info field 1246 to specify the target subchannel for DSO TXS operations. Indeed, as RU allocation field 1232 only to indicate the channel / RU where the STA is supposed to send the ICR back to the AP, the STA may need further information to know which subchannel is needed for DSO TXS operation (in case it is not predefined). For instance, as shown in Figure 6, the AP can allocate a specific 20MHz band to let the STA send back the ICR (e.g. RU is allocated in the lower 20MHz of the secondary subchannel for STA14) while a 40MHz subchannel is expected for the DSO TXS operations. The 40MHz subchannel (or any other subchannel) may be specified in Subchannel Info field 1246.

[0244] The ICR (not shown) may be a BA frame. In some embodiments, the ICR may include the TA (transmitter address) field to indicate the identity of the STA transmitting the response to the AP. In this case, to avoid the collision between multiple ICRs simultaneously sent from multiple STAs, the ICRs are sent in UL OFDMA using an RU allocation separately assigned to each STA by the RU allocation field 1232 in ICF1 .

[0245] As explained with Figure 6, ICF2 can be separated to two or more sub ICFs (e.g., ICF2a, ICF2b) which respectively contains the information for the STA that is operating on the subchannel where ICF2 is sent.

[0246] Figure 13a schematically illustrates a communication device 1300 configured to implement at least one embodiment of the present invention, for instance any of the (AP and non- AP) stations shown in Figure 1.

[0247] The communication device 1300 may preferably be a device such as a microcomputer, a workstation or a light portable device. The communication device 1300 comprises a communication bus 1313 to which there are preferably connected: a central processing unit 1301 , such as a processor, denoted CPU; a memory 1303 for storing an executable code of methods or steps of the methods according to embodiments of the invention as well as the registers adapted to record variables and parameters necessary for implementing the methods; and at least one communication interface 1302 connected to a wireless communication network, for example a communication network according to one of the IEEE 802.11 family of standards, via transmitting and receiving antennas 1304.

[0248] Preferably the communication bus provides communication and interoperability between the various elements included in the communication device 1300 or connected to it. The representation of the bus is not limiting and in particular the central processing unit is operable to communicate instructions to any element of the communication device 1300 directly or by means of another element of the communication device 1300.

[0249] The executable code may be stored in a memory that may either be read only, a hard disk or on a removable digital medium such as for example a disk. According to an optional variant, the executable code of the programs can be received by means of the communication network, via the interface 1302, in order to be stored in the memory of the communication device 1300 before being executed.

[0250] In an embodiment, the device is a programmable apparatus which uses software to implement embodiments of the invention. However, alternatively, embodiments of the present invention may be implemented, totally or in partially, in hardware (for example, in the form of an Application Specific Integrated Circuit or ASIC).

[0251] Figure 13b is a block diagram schematically illustrating the architecture of the communication device 1300, adapted to carry out, at least partially, the invention. As illustrated, device 1300 comprises a physical (PHY) layer block 1323, a MAC layer block 1322, and an application layer block 1321.

[0252] The PHY layer block 1323 (here an 802.11 standardized PHY layer) has the task of formatting, modulating on or demodulating from any 20MHz channel or the common communication channel, and thus sending or receiving frames over the wireless radio medium used, such as 802.1 1 frames, for instance medium access trigger frames TF to reserve a transmission slot, MAC data and management frames based on a 20MHz width to interact with legacy 802.11 stations, as well as of MAC data frames of OFDMA type having smaller width than 20MHz legacy (typically 2 or 5 MHz) to / from that radio medium.

[0253] The MAC layer block or controller 1322 preferably comprises a MAC 802.11 layer 1324 implementing conventional 802.11 be MAC operations, and additional block 1325 for carrying out, at least partially, the invention. The MAC layer block 1322 may optionally be implemented in software, which software is loaded into RAM 1303 and executed by CPU 1301.

[0254] Preferably, the additional block 1325, referred to as DSC managing module which has different operations to implement parts of the invention, depending on the role played by the communication device 1300.

[0255] MAC 802.11 layer 1324 and DSC Managing module 1325 interact one with the other in order to process accurately communications over the medium, e.g., over subbands according to embodiments of the invention.

[0256] On top of the Figure, application layer block 1321 runs an application that generates and receives data packets, for example data packets such as a video stream. Application layer block 1321 represents all the stack layers above MAC layer according to ISO standardization.

[0257] Although the present invention has been described hereinabove with reference to specific embodiments, the present invention is not limited to the specific embodiments, and modifications will be apparent to a skilled person in the art which lie within the scope of the present invention.

[0258] Many further modifications and variations will suggest themselves to those versed in the art upon referring to the foregoing illustrative embodiments, which are given by way of example only and which are not intended to limit the scope of the invention, that being determined solely by the appended claims. In particular the different features from different embodiments may be interchanged, where appropriate. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be advantageously used.

Claims

34CLAIMS1 . A communication method in a wireless network, comprising, at an access point (AP) operating on an operating channel including a primary subchannel and a non-overlapping secondary subchannel: sending, to stations, at least one frame to organise a time-sharing of a transmission opportunity (TXOP) gained by the AP, wherein the at least one frame signals a channel switch from the primary subchannel to the secondary subchannel for at least one of the stations that is initially operating on the primary subchannel, and signals time-sharing schemes of the TXOP on the primary subchannel and of the TXOP on the secondary subchannel, respectively.

2. The method of Claim 1 , wherein the channel switch signalling and the time-sharing schemes are provided within one single frame.

3. The method of Claim 1 , wherein the channel switch signalling is provided within a first frame and the time-sharing schemes are respectively provided in multiple second and separate frames.

4. The method of Claim 3, wherein at least one second frame providing a time-sharing scheme includes padding to have the same length as another second frame providing another time-sharing scheme.

5. The method of Claim 3, wherein the first frame is transmitted over the primary and secondary subchannels, whereas the second and separate frames are transmitted over their respective subchannel only.

6. The method of Claim 3, wherein the first frame signals a first subpart of the secondary subchannel over which the station has to respond to the first frame and signals a second and distinct subpart of the secondary subchannel over which another station has to respond to the first frame.

7. The method of Claim 3, wherein the AP builds the time-sharing schemes on the primary and secondary subchannels based on responses to the first frame received from stations on the primary and secondary subchannels respectively.

8. The method of Claim 1 , wherein the AP receives a response to the at least one frame from the station over the secondary subchannel and another response from another station over the primary subchannel.

9. The method of Claim 1 , wherein the at least one frame defines multiple TXOP timeslots within the TXOP and signals different time-sharing schemes for the primary and secondary subchannels over the multiple TXOP timeslots.

10. The method of Claim 9, wherein one of the time-sharing schemes gives back the primary and secondary subchannels to the AP during one of the multiple timeslots.3511 . The method of Claim 1 , wherein a time-sharing scheme on the primary subchannel allocates the primary subchannel to a second station of the BSS for peer-to-peer exchange with a station not belonging to the BSS.

12. The method of Claim 11 , wherein the time-sharing scheme signals an Associated Identifier (AID) of the second station or an identifier of a P2P Group to which the second station belongs.

13. The method of Claim 1 , wherein the AP uses one of the primary and secondary subchannels for a frame exchange, wherein a resource unit of the used subchannel in the vicinity of the other subchannel remains unused during the frame exchange.

14. The method of Claim 1 , wherein the AP sends a frame prior to the at least one frame in order to reserve the medium for the TXOP.

15. A communication method in a wireless network, comprising, at a station operating on a primary subchannel of an operating channel of a Basic Service Set (BSS), the operating channel including the primary subchannel and a non-overlapping secondary subchannel: receiving, from an access point (AP) of the BSS, at least one frame that organises a time-sharing of a transmission opportunity (TXOP) gained by the AP, wherein the at least one frame signals a channel switch of the station from the primary subchannel to the secondary subchannel and signals a time-sharing scheme of the TXOP on the secondary subchannel, responsive to the at least one frame, switching to the secondary subchannel, and performing a frame exchange over the secondary channel based on the time-sharing scheme.

16. The method of Claim 15, wherein the channel switch signalling and the time-sharing scheme are provided within one single frame.

17. The method of Claim 15, wherein the channel switch signalling is provided within a first frame and the time-sharing scheme is provided in a second and separate frame.

18. The method of Claim 17, wherein the first frame is transmitted over the primary and secondary subchannels, whereas the second and separate frame is received over the secondary subchannel only.

19. The method of Claim 17, wherein the first frame signals a first subpart of the secondary subchannel over which the station has to respond to the first frame, and the station sends to the AP a response to the first frame over the first subpart only of the secondary channel.

20. The method of Claim 15, wherein the station, after switching to the secondary subchannel, sends to the AP a response to the at least one frame over the secondary subchannel.

21. The method of Claim 15, wherein performing the frame exchange over the secondary channel includes not using a resource unit of the secondary subchannel in the vicinity of the primary subchannel.

22. The method of Claim 15, wherein the station switches back to the primary subchannel at the end of a time-sharing duration signalled in the at least one frame.

23. The method of Claim 1 or 15, wherein a time-sharing scheme on the secondary subchannel allocates the secondary subchannel to the station for peer-to-peer (P2P) exchange with another station of the BSS.

24. The method of Claim 23, wherein the time-sharing scheme signals an Associated Identifier (AID) of the station or an identifier of a P2P Group to which the station belongs.

25. The method of Claim 1 or 15, wherein the at least one frame is a MU-RTS TXS Trigger frame.

26. The method of Claim 25, wherein a TXS Mode subfield of the MU-RTS TXS Trigger frame is set to value 3.

27. The method of Claim 1 or 15, wherein the primary and secondary subchannels are distinct subchannels.

28. The method of Claim 1 or 15, wherein the station is a non-AP station belonging to the BSS or an AP managing another BSS.

29. A Trigger frame signalling a channel switch from a primary subchannel to a secondary subchannel for at least one receiving station that is operating on the primary subchannel.

30. The frame of Claim 29, having a padding field after a frame check sequence (FCS) field.

31. The frame of Claim 29, signalling a MU-RTS Trigger type, wherein a TXS Mode subfield of a Common Info field is set to 3.

32. The frame of Claim 29, comprising at least one subfield in a Common Info field to define multiple TXOP timeslots within the TXOP in which to apply different time-sharing schemes.

33. The frame of Claim 32, wherein the at least one subfield comprises a first subfield signalling the number of TXOP timeslots in the multiple TXOP timeslots and second subfields signalling the durations of the multiple TXOP timeslots respectively.

34. The frame of Claim 29, further signalling separate time-sharing schemes of a TXOP on the primary subchannel and of the TXOP on the secondary subchannel, respectively.

35. The frame of Claim 34, comprising multiple User Info fields defining the time-sharing schemes respectively.

36. The frame of Claim 35, wherein each User Info field comprises: a subfield signalling the primary or secondary subchannel, a subfield including an Associated Identifier (AID) of a station to which the signalled primary or secondary subchannel is allocated or an identifier of a peer-to-peer (P2P) Group to which the signalled primary or secondary subchannel is allocated, a subfield signalling a transmission mode in the allocated primary or secondary subchannel, optionally, a subfield signalling a TXOP timeslot from amongst multiple TXOP timeslots within the TXOP.

37. The frame of Claim 36, wherein the transmission mode subfield takes a value from the following set of values: a first value signalling the TXOP or corresponding TXOP timeslot is allocated back to an owner of the TXOP, a second value signalling the allocated station can only transmit MPDU(s) addressed to its associated AP, a third value signalling the allocated station can transmit MPDU(s) addressed to its associated AP or transmit P2P MPDU(s), a fourth value signalling the allocated station or P2P Group can only transmit P2P MPDU(s).

38. The frame of Claim 29, signalling a Trigger type with a value comprised between 9 and 15.

39. A wireless communication device comprising at least one microprocessor configured for carrying out the method of Claim 1 or 15.

40. A non-transitory computer-readable medium storing a program which, when executed by a microprocessor or computer system in a wireless device, causes the wireless device to perform the method of Claim 1 or 15.

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