Anchor channel switching mechanism for multi-radio device

Abstract

The disclosed station device of a Basic Service Set "BSS" having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondary channels being an anchor channel for non-primary channel access within the BSS. The station device comprises a first radio configured to operate over the overall operating channel and a second radio configured to operate over a subset of the operating channel including the anchor channel and not the primary channel. The station device is configured to perform access to the anchor channel, in response to receiving, using the second radio, a frame for switching channel access over the anchor channel.

Description

[0001] ANCHOR CHANNEL SWITCHING MECHANISM FOR MULTI-RADIO DEVICE

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to wireless communications and more specifically to management of transmission operation on a non-primary channel.

[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 the channel when it has data to send.

[0008] Efficient medium usage within one operating channel having an operation bandwidth (up to 320MHz in the latest 802.11 be D6.0 standard, but may be wider in future amendments) has evolved along the evolution of the IEEE 802.1 1 standards. For example, dynamic bandwidth signalling feature was introduced in the IEEE 802.11 ac amendment, preamble puncturing feature was introduced in the IEEE 802.11 ax standard and further evolved in the IEEE 802.11 be amendments. An operating band of 40, 80, 160 or 320MHz (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 only used when sending data at full speed. All of the known features for efficient medium usage assumes that the primary channel is idle. If the primary channel is busy for instance due to interference, stations are not allowed to send any frame even if the secondary channels are idle. It leads to a main drawback: if only the primary channel is busy, the secondary channels in the rest of the operating band remain unused during the occupancy time of the primary channel. So the bandwidth usage efficiency decreases a lot due to this rule.

[0009] The new task group 802.1 1 bn intends to solve this drawback by introducing a new feature: the non-primary channel access procedure also called NPCA mechanism, or SCA (for “Secondary Channel Access”). The principle of the NPCA procedure is detailed in Figure 2.

[0010] Usually, AP and STAs perform backoff procedure in the primary backoff 20 MHz channel only, also called the primary channel. By using the NPCA mechanism, a STA / AP can enable one or more backoff procedures in the secondary channels.

[0011] If the primary 20 MHz channel is busy because of a transmission from an AP / STA owning to a neighbour BSS (for “Basic Set Service”), also called OBSS, the AP / STA switches to one of the secondary channels owning to its operating band to run a backoff procedure. The selected new 20MHz channel will be called further as anchor channel. The frame exchanges in the anchor channel are done no later than the end of the TXOP of the OBSS interference. Then the AP / STA switches back to its primary channel.

[0012] However, those schemes still do not optimize the use of available spectrum in particular in case of hidden nodes, resulting in underutilization of network resources. As described in Figures 3a and 3b, several scenarios can lead to misunderstandings among AP and STA using NPCA mechanism.

[0013] The Figure 3a and 3b describe an example scenario such as:

[0014] The BSS 300 is composed of an AP1 310 and two STAs 301 and 302.

[0015] The BSS 320 (OBBS) is composed of an AP2 321 and a STA21 322.

[0016] For the Figure 3a, only the AP1 is in the range of the OBSS in such a manner that each medium access of the AP2 or STA21 is regarded as interference for the AP1 , so the AP1 must set its NAV (for “Network Allocation Vector”) during the length of the TXOP (for “Transmission Opportunity”) initiated by the AP2 or the STA21. The STA11 and STA12 are not disturbed by the medium access initiated by the AP2 or the STA21 , hence the AP2 or the STA21 are regarded as “hidden nodes” from the knowledge of STA11 and STA12. In such a case, if the NPCA mechanism is automatically applied, the AP1 switch to the anchor channel and the STA11 and STA12 stay on their primary channel. It entails a misalignment on the selection of the primary / anchor channel to be used to initiate a backoff procedure in the BSS 300. All transmissions between the AP and its associated STAs will thus fail.

[0017] For the Figure 3b, only the STA11 310 is in the range of the OBSS, so that the AP2 and STA21 are regarded as hidden nodes for the knowledge of AP1 and STA12. In the same way as for the Figure 3a, if the NPCA mechanism is automatically applied, the STA11 switch to the anchor channel and the AP1 and STA12 stay on their primary channel. It entails similarly a misalignment on the selection of the primary / anchor channel to be used to initiate a backoff procedure in the BSS 300. All transmissions between the AP and its associated STAs will thus also fail. Accordingly, there is a need for techniques which allow for improved NPCA mechanism, in particular regarding an optimized bandwidth usage efficiency as well as an optimized power consumption.

[0018] SUMMARY OF INVENTION

[0019] 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 band. It is achieved by enabling non-primary channel access operation, i.e. operations on secondary channels different from the primary channel, by AP or non-STA upon the detection of interferences on the primary channel.

[0020] Embodiments defined hereinbelow are providing an improved efficiency of secondary channel access, performing in particular a management of hidden nodes situations, with limited or no extra time and limited or no extra power consumption, and being capable to adapt to unexpected end instants (earlier of later than expected) of the interference communication.

[0021] According to an aspect of the invention, there is provided a station of a Basic Service Set “BSS” having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondary channels being an anchor channel for non-primary channel access within the BSS, the station comprising a first radio configured to operate over the overall operating channel and a second radio configured to operate over a subset of the operating channel including the anchor channel and not the primary channel.

[0022] The additional second radio operating over the anchor channel can thus be freely reached by an initiating station that encounters an interfering frame overlapping the primary channel, in order to initiate anchor channel access switch to the station that does not encounter the interference over the primary channel. Accordingly, the stations of a common BSS are kept aligned on the same channel for medium access, in case of a hidden node situation.

[0023] According to an embodiment, the station is configured to perform access to the anchor channel in response to receiving, using the second radio, a frame for switching channel access over the anchor channel.

[0024] According to an embodiment, the first radio includes a transmit chain and a receive chain, and the second radio includes a receive chain.

[0025] According to an embodiment, the station is configured to switch the first radio from the primary channel to the anchor channel, for performing the access to the anchor channel with the first radio.

[0026] According to an embodiment, the second radio includes a transmit chain and a receive chain, and the station is configured to perform the access to the anchor channel with the second radio.

[0027] According to an embodiment, the station is configured to switch the first radio from the operating channel to the anchor channel during a switching period overlapping a padding time provided in the frame for switching channel access. The frame for initiating a channel access switch may include or may be an initial control frame “ICF” added with the padding time. For example, the padding time duration may be specifically adapted for a radio to switch between channels.

[0028] According to an embodiment, the station is configured to limit in time the communication over the secondary channel at a maximum duration, the maximum duration information being provided in the frame for switching channel access.

[0029] According to another aspect of the invention, there is provided an initiating station of a Basic Service Set “BSS” having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondary channels being an anchor channel for non-primary channel access within the BSS, the initiating station being configured, in response to sensing an interfering frame from an OBSS, to switch to anchor channel access and to send a frame for switching channel access over the anchor channel to initiate anchor channel access switch to other stations of the BSS, the frame for switching channel access including an initial control frame with an additional padding time.

[0030] According to an embodiment, the additional padding time is of a duration adapted for a radio to switch between channels.

[0031] According to an embodiment, the initiating station is capable to read at least a duration field in a header of the interfering frame received from an interfering station over the primary channel, and configured to limit in time the communication over the secondary channel at a maximum duration based on the duration field content.

[0032] According to an embodiment, the initiating station is capable to read at least a duration field in a header of the interfering frame received from an interfering station over the primary channel, and configured to provide, in the frame for switching channel access, a maximum duration information based on the duration field content.

[0033] According to another aspect of the invention, there is provided a system comprising at least two stations of a Basic Service Set among which at least one station as defined above, and at least one initiating station as defined above

[0034] According to an implementation of the invention, there is provided a communication method for a station of a Basic Service Set “BSS” having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondary channels being an anchor channel for non-primary channel access within the BSS, the communication method comprising operating over the overall operating channel with a first radio, and operating over a subset of the operating channel including the anchor channel and not the primary channel with a second radio.

[0035] According to an implementation, the method comprises performing anchor channel access in response to receiving, using the second radio, a frame for switching channel access over the anchor channel. According to an implementation, operating over the overall operating channel comprises transmitting and receiving frames with the first radio, and operating over the subset of the operating channel comprises receiving frames with the second radio.

[0036] According to an implementation, the method comprises switching the first radio from the primary channel to the anchor channel to perform access to the anchor channel with the first radio.

[0037] According to an implementation, operating over the subset of the operating channel comprises transmitting and receiving frames with the second radio, and performing the access to the anchor channel uses the second radio.

[0038] According to an implementation, the method comprises switching the first radio from the operating channel to the anchor channel, during a switching period overlapping a padding time provided in the frame for switching channel access. For example, the padding time duration may be specifically adapted for a radio to switch between channels.

[0039] According to an implementation, the method comprises limiting in time the communication over the secondary channel at a maximum duration, the maximum duration information being provided in the frame for switching channel access.

[0040] According to another aspect of the invention, there is provided an initiating method for switching channel access for a station of a Basic Service Set “BSS” having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondary channels being an anchor channel for non-primary channel access within the BSS, the method including, in response to sensing an interfering frame from an OBSS, to switch to anchor channel access and to send a frame for switching channel access over the anchor channel to initiate anchor channel access switch to other stations of the BSS, the frame for switching channel access including an initial control frame with an additional padding time.

[0041] According to an implementation, the additional padding time is of a duration adapted for a radio to switch between channels.

[0042] According to an implementation, the method includes reading at least a duration field in a header of the interfering frame received from an interfering station over the primary channel, and limiting in time the communication over the secondary channel at a maximum duration based on the duration field content.

[0043] According to an implementation, the method includes reading at least a duration field in a header of the interfering frame received from an interfering station over the primary channel, and providing, in the frame for switching channel access, a maximum duration information based on the duration field content.

[0044] According to another aspect of the invention, there is provided a switching channel access communication method of stations of a Basic Service Set among implementing a communication method as defined above, and an initiating method for switching channel access as defined above. 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.

[0045] 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 “device”, "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.

[0046] 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.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Embodiments of the invention will now be described, by way of example only, and with reference to the following drawings in which:

[0049] Figure 1 illustrates an exemplary network environment in which embodiments of the present disclosure can be implemented;

[0050] Figure 2 illustrates an exemplary timeline, of a STA employing non-primary channel access medium access;

[0051] Figure 3a and 3b illustrates an exemplary network illustrating the different detection level of interference in which embodiments of the present disclosure can be implemented;

[0052] Figure 4 schematically illustrates an Multi-radio capable architecture for an MLD to implement embodiments of the invention;

[0053] Figure 5 illustrates an exemplary timeline, of a STA in which embodiments of the present disclosure can be implemented;

[0054] Figure 6 illustrates, using a flowchart, general steps at a station initiating NPCA mechanism according to embodiments of the invention;

[0055] Figure 7 illustrates, using a flowchart, general steps at a station receiving data transmission thanks to NPCA mechanism according to embodiments of the invention;

[0056] Figure 8a and 8b shows a schematic representation of a wireless communication device in accordance with embodiments of the present invention. DETAILLED DESCRIPTION OF EMBODIMENTS

[0057] 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.

[0058] 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 station or STA).

[0059] 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.

[0060] 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 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 or video 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.

[0061] 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.

[0062] The 802.11 family of standards define various media access control (MAC) mechanisms to drive access to the wireless medium.

[0063] For example, 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, published on May 2019.

[0064] 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.

[0065] 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.

[0066] 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 signaled 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. 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 16-bit 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).

[0067] 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.

[0068] 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. An Access Point Multi-Link Device (or AP MLD) then corresponds to a MLD where each STA affiliated with the MLD is an AP, hence referred to as “affiliated AP”. A non-Access Point Multi-Link Device (or non-AP MLD) corresponds to a MLD where each STA affiliated with the MLD is a non-AP STA, referred to as “affiliated non-AP STA”. Depending on the literature, “multilink device”, “ML Device” (MLD), “multilink logical entity”, “ML logical entity” (MLE), “multilink set” and “ML set” are synonyms to designate the same type of ML Device.

[0069] 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.

[0070] The links established (or “enabled links”) for MLDs are theoretically independent, meaning that the channel access procedure (to the communication medium) and the communication are performed independently on each link. Hence, different links may have different data rates (e.g., due to different bandwidths, number of antennas, etc.) and may be used to communicate different types of information (each over a specific link).

[0071] 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.

[0072] 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. 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.

[0073] 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.

[0074] Figure 1 illustrates an exemplary network environment in which embodiments of the present disclosure can be implemented.

[0075] 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).

[0076] A first wireless network (or Basic Service Set) BSS1 comprises an access point (AP) 110 and three non-AP stations (STAs) 111 , 112 and 113 associated with the AP 110 (i.e., registered with it). A second wireless network BSS2 comprises an AP 120 and three associated non-AP STAs 121 , 122 and 123. In the following, BSSx represents any of the wireless networks, while 1x1 , 1x2 and 1x3 any of the non-AP stations. Of course, another number of wireless networks and any number of non-AP stations per wireless network can be contemplated. In the present disclosure, APs 1 10, 120 are also referred to, respectively, as AP1 , AP2. 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.

[0077] All or part of the APs may be affiliated APs to the same AP MLD. They also can be separate devices. Any AP broadcasts management frames, such as beacon frames, to share parameters to be used for the functioning of its BSS.

[0078] The stations (AP and non-AP) of each wireless network exchange data frames over the communication channel 100, under the management of the AP. 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.

[0079] The APs may also communicate one with each other, either using a communication channel of their BSS that is common to the other BSSs or using separate communication links (such as a separate wireless network or channel, an Ethernet backhaul connecting all the APs, direct links, and so on).

[0080] The stations (including the AP) may 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 wireless network BSSx, 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 802.11ax 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.

[0081] 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.

[0082] In the IEEE 802.11 wireless local area networking standards, the multi-AP system 100 may correspond to an extended service set (ESS) and each of the wireless networks to a basic service set (BSS).

[0083] Figure 2 illustrates an exemplary timeline, of a STA employing non-primary channel access NPCA medium access;

[0084] In the IEEE 802.11 wireless local area networking standards, typically implemented by the certification named Wi-Fi, including versions up to 11 be (Wi-Fi 7), generally does not allow for the use of the secondary channel while the primary channel is busy. In standard 802.11 practice, transmissions typically utilize 20 / 40 / 80 / 160 / 320 MHz channels, with one dedicated 20 MHz channel functioning as the primary channel. Regardless of whether secondary channels are idle or busy, these channels remain inaccessible if the primary channel is occupied.

[0085] In the example, the BSS operating band, which may be announced by the AP1 110 includes two subchannels (S1 , S2), which are a 80 MHz channel S1 and a 40 MHz channel S2, and where each subchannel includes multiple 20 MHz channels and has one backoff 20 MHz channel. The first channel S1 may cover the overall operating band of the BSS, and can be called later “overall operating channel”.

[0086] The first 80MHz channel S1 is composed of a set of four 20MHz channels and a primary channel P1 . The second 40MHz channel S2 is composed of a set of two 20MHz channels and an anchor channel P2.

[0087] Typically, AP and STAs perform backoff procedure in the primary backoff 20 MHz channel only. By using the NPCA mechanism, a STA / AP can enable one or more backoff procedures.

[0088] If the primary 20 MHz channel P1 is busy because of an OBSS transmission, the AP / STA switches from the primary channel P1 to the anchor channel P2. The frame exchanges in the second 40MHz channel S2 are done no later than the end of the TXOP that uses the primary channel P1 . On the 80MHz first channel S1 , when the STA or AP does a backoff, an overlapping BSS (OBSS) starts a TXOP. The AP and the STA switch to the 40MHz second channel S2 for the possible frame exchanges on the 40MHz channel S2. On the anchor channel, the STA performs CCA (for “Clear Channel Assessment”) for PPDU (for “Preamble and header Protocol Data Unit”) detection and does the backoff. The STA transmits an initial control frame (ICF) 201 after its backoff counter becomes null (0). The initial control frame may be an RTS (for “Request To Send”) frame or MU-RTS frame. The AP responds with an ACK (for “acknowledgment”) frame 202 after the AP receives the ICF frame. The ACK frame may be a CTS (for “Clear To Send”) frame. The STA transmits a data frame 21 1 after receiving the ACK frame. The AP may respond with an acknowledgement ACK frame (not shown) after receiving the data frame.

[0089] After the end of the OBSS interference, the STA can switch back to its primary channel P1 and its operating band S1. The STA can initiate new transmissions through the complete operating band S1.

[0090] Figure 4 schematically illustrates an exemplary Multi-radio capable architecture for an MLD to implement embodiments of the invention;

[0091] This example takes the structure of two affiliated non-AP STAs sharing their antenna resources. The Multi-radio capable architecture for an MLD presented in this example is for illustrative purpose only and other alternative architectures may be contemplated.

[0092] The architecture comprises two radio stacks, a first radio stack 400a-405a-415a- 420a and a second radio stack 400b-405b-415b-420b.

[0093] At least one of the two radio stacks, for instance the first radio stack, comprises a transmitter and receiver 802.11 be MAC module 400a (exchanging data with higher layers), a transmitter and receiver 802.11 be PHY module 405a connected with the MAC module 400a, a transmitter and receiver radio-frequency chain 415a connected with the PHY module 405a and the transmitter and receiver antennas 420a connected with the transmitter and receiver RF chain 415a, possibly through a switch 410.

[0094] The first radio stack 400a / 405a / 415a is accordingly a full radio resource allowing reception and transmission of any IEEE802.11 frames. In particular, it includes encoding and decoding modules to encode and decode any IEEE802.11 frames.

[0095] In one embodiment, the other one of the two radio stacks, for instance the second radio stack, is a receiver-only chain, also called “receive chain”, meaning this radio stack is only able to receive frames transmitted with low modulation scheme (for instance control frame).

[0096] The second radio stack accordingly comprises a receiver (-only) 802.11 be MAC module 400b (exchanging data with higher layers), a receiver (-only) 802.11 be PHY module 405b connected with the receiver (-only) MAC module 400b, a receiver (-only) radio-frequency chain 415b connected with the receiver (-only) PHY module 405b and the antennas 420b connected with the receiver (-only) RF chain through the switch 410. In this embodiment, the second’s radio receive chain 400b / 405b / 415b is a reduced function (or “light”) radio resource which only allows reception and transmission of specific IEEE802.11 frames. In particular, it only includes encoding and decoding modules to encode and decode specific frames (e.g. non-HT (duplicate) PPDU using a rate of 6 Mbps, 12 Mbps, or 24 Mbps and 1 Spatial Stream). It has to be noticed that the receive chain 400b / 405b / 415b consumes less power than a transmit and receive chain.

[0097] In another embodiment, the second radio stack 400b-405b-415b-420b comprises a transmit and receive chain, as the first radio stack. In other words, the second radio stack comprises a transmitter and receiver 802.11 be MAC module 400b (exchanging data with higher layers), a transmitter and receiver 802.11 be PHY module 405b connected with the MAC module 400b, a transmitter and receiver radio-frequency chain 415b connected with the PHY module 405b and the transmitter and receiver antennas 420b connected with the transmitter and receiver RF chain 415b, possibly through a switch 410.

[0098] The second radio stack 400b / 405b / 415b is accordingly a full radio resource allowing reception and transmission of any IEEE802.11 frames. In particular, it includes encoding and decoding modules to encode and decode any IEEE802.11 frames.

[0099] In such an embodiment where both first and second radio stacks comprise transmit and receive chain, the antennas 420a, 420b may be directly connected with the transmitter and receiver RF chain 415a, 415b, with no switch.

[0100] In the embodiment where the first radio stack comprises a transmit and receive chain and the second radio stacks comprise a receive(-only) chain, the antennas 420a, 420b are advantageously connected with the transmitter and receiver RF chain 415a, 415b, through the shared switch 410 configured to switch antenna allocation scheme.

[0101] Taking advantage of the architecture, it is interesting to apply this architecture for each device AP and non-AP STA to implement this invention. For instance, the first radio chain 400a / 405a / 415a can be setup to operate on the operating band S1 with the primary channel P1 and the second radio chain 400b / 405b / 415b can be setup to operate on the operating band S2 with the anchor channel P2 as primary channel. In another embodiment the second chain 400b / 405b / 415b can be setup to operate only on the anchor channel to optimize power consumption.

[0102] This architecture allows to detect any activities and to decode any ICF frames transmitted on the anchor channel prior to switching from the primary channel to the anchor channel.

[0103] This configuration solves the main issues described in relation with the Figure 3a and 3b. Indeed, if any AP or non-AP STA does not detect OBSS interference, this AP or non-AP STA can detect the initial control frame (ICF) sent by other STA that has detected OBSS interferences and would like to initiate NPCA mechanism. Global issues related to misalignment about OBSS interference detection are now solved thanks to this architecture. Figure 5 illustrates an exemplary timeline, of a STA in which embodiments of the present disclosure can be implemented;

[0104] In the same way as the scenario described in relation with the Figure 2, where the non-primary channel access NPCA mechanism basically comprises steps of: Reception of ICF overthe anchor channel; Switching to the anchor channel; Transmission overthe anchor channel; Switching back to the primary channel, the timeline describes how the invention implements the new NPCA mechanism. Two operating channels are defined: one first 80MHz channel S1 composed of a set of four 20MHz channels and a primary channel P1 to perform PCA (hence S1 is a PCA operating channel) and a second 40MHz channel S2 composed of a set S2 of four 20MHz channels and an anchor channel P2 to perform NPCA (hence S2 is a NPCA operating channel). The second channel set S2 is included in the first channel set S1 . S2 may be reduced to P2 in some embodiments. Similarly, S1 may be reduced to P1 and P2 in some embodiments.

[0105] For this example, the AP or non-AP STA implements the architecture described in the Figure 4. In consequence, each AP or non-AP STA has a first radio (e.g. transmit and receive chains) operating on the set S1 of subchannels, and a second radio (e.g. receive chain only. However full radio is also possible) operating on the set S2 of subchannels.

[0106] If the primary 20 MHz channel is busy because of the OBSS transmission 220, the station (AP / STA) switches from the primary channel P1 to the anchor channel P2. In another embodiment, the AP / STA can take the decision to switch its primary channel depending on some conditions. If the duration of the OBSS interference is too short, the AP / STA can decide not to switch its primary channel. Another condition could be to save power. In that case, the station can decide not to switch its primary channel.

[0107] Upon the detection of the OBSS interference, the initiating station switches its primary channel to the anchor channel and sends an extended ICF frame 230 to solicit its intended destined station. The extended ICF frame 230 may be an RTS frame or MU-RTS frame with some padding as described in the subclause 35.5.2.2.3 of the 802.11 be amendment (draft 6.0). The padding overhead lets enough time for the solicited destined station to switch its antenna resources and to configure the first radio to operate on anchor channel P2 and set S2 of subchannels, in case they have not yet detected the OBSS transmission. Then the solicited destination station may switch if needed, and then acknowledge the extended ICF frame 230 and some data transmissions follows the acknowledgment frame 202.

[0108] In another embodiment, when the initiating station operates with its first radio on the operating band S2 with the anchor channel P2 as primary channel, its second radio chain can be configured to operate on the initial primary channel P1. It allows to detect (listen) any change of medium status (also called medium synchronization) while transmitting, especially when the OBSS TXOP is truncated and when the medium on the initial primary channel becomes free. Such embodiment is performed thanks to the antenna resources remaining available for driving the second radio chain. Once the data transmission 211 is ended, the initiating station and the solicited station switches back to the initial configuration: the first radio chain switches back to the operating band S1 with the initial primary channel P1 and the second radio chain switches back to the operating band S2 with the anchor channel P2. In another embodiment, the second radio chain switches back to only the anchor channel P2.

[0109] Figure 6 illustrates, using a flowchart, general steps at a station initiating NPCA mechanism of the communication method according to the present disclosure.

[0110] An OBSS interference for any station owning to the BSS1 is characterized by the reception of frame from a station that is not associated with the AP1 . This frame can be a control frame such a RTS frame or a MU-RTS frame. It could be also a QoS data frame. The interest of this frame is that any station from the BSS1 can decoded the MAC header of this OBSS interference specially to read the Duration field that enables the station to estimate the duration of the OBSS interference. The value of the Duration field is typically used by the station to set its basic NAV meaning that the station is not allowed to content the medium for the duration indicated in the Duration field.

[0111] The value of the Duration field may also be used by the station to limit in time the communication over the second channel at a maximum duration. In other words, the switching from the primary channel P1 to the anchor channel P2 lasts at maximum the duration of the OBSS interference.

[0112] Upon the detection of an OBSS interference 600, the initiating station (AP / STA) is configured to switch its primary channel P1 to the anchor channel P2 for the duration of the OBSS interference. And the NPCA mechanism is launched by implementing steps 610, 620, 630, (640, 650).

[0113] At step 610, the initiating station reconfigures its full radio chain on the operating band S2 with the anchor channel P2 as primary channel to optimize the bandwidth usage.

[0114] At step 620, the extended initial control frame (ICF) is sent to one or more destined stations. In one embodiment the ICF is sent on the anchor channel P2. If the extended ICF frame is only sent on the P2 channel, the initiating station sends another a control frame such as a MU- RTS / RTS frame to reserve and to extend the transmission on the operating channel S2. In another embodiment, it is sent on all the operating band S2. The extended ICF frame could be a MU-RTS control frame (as described in the subclause 9.3.1 .22.9 of the draft 6.0 of the 802.1 1 be amendment) or a RTS frame (as described in the subclause 9.3.1.2 of the draft 6.0 of the 802.11 be amendment) enhanced with some padding (as described in the subclause 35.5.2.2.3 of the draft 6.0 of the 802.11 be amendment). The Duration field is set to the remaining time in relation to the value of the OBSS interference so as to provide, in the channel access initiating frame (extended ICF), a maximum duration information intended to limit in time the communication on the destined station side. Optionally, the initiating station can configure its second radio chain to operate on the initial primary channel. It allows to detect any change of medium status, especially when the OBSS TXOP is truncated and when the medium on the initial primary channel becomes free. In that case, the initiating station can release the NPCA mechanism by sending for instance a CF- END frame and switches back to its common operating band S1 with the primary channel P1.

[0115] Upon the reception of the ACK frame from the destined station at step 630, data transmission may be performed at step 640. If no ACK frame is received, the initiating station switches back to its common operating band S1 with the primary channel P1 at step 650.

[0116] When the data transmission is ended and the duration of the OBSS interference is elapsed, the initiating station switches back to its common operating band S1 with the primary channel P1 at step 650. In another embodiment, if no data are to be transmitted or it is sensed that the OBSS interference ends before the maximum duration set, the initiating station can release the NPCA mechanism by sending for instance a CF-END frame and switches back to its common operating band S1 with the primary channel P1.

[0117] Figure 7 illustrates, using a flowchart, general steps at a station receiving data transmission thanks to NPCA switch mechanism of the communication method according to the present disclosure.

[0118] Upon the reception of an extended ICF frame at step 700, a destined station may use the padding time added to the ICF frame to reconfigure its radio chains depending on the information in the ICF frame, at step 710. If the extended ICF frame indicates that the operating band is set to S2 with the anchor channel P2 as "primary channel", the destined station reconfigures its full radio chain consequently.

[0119] As the communication method comprises operating over a subset S2 of the operating channel including the anchor channel P2 and not the primary channel P1 with the second radio (comprising at least a receive chain), the extended ICF frame communicated at step 700 over the anchor channel P2 is indeed received using the second radio’s receive chain. The extended ICF frame received at step 700 is advantageously transmitted at step 620 described above with reference to figure 6.

[0120] Then in response to receiving the extended ICF at step 700, the destined device switches to the operating channel S2, during a switching period. The switching period advantageously overlaps the the padding time intendedly provided within the extended ICF frame, and performs channel access (NPCA) using the anchor channel, at step 710.

[0121] The destined station may acknowledge the extended ICF frame by sending an ACK frame to the initiating station at step 720. Data frames from the initiating station can then be received at step 730.

[0122] For instance, the communication over the second channel, i.e. the remaining time for the data transmission step 730, may be limited in time at the maximum duration provided in the channel access initiating frame. The maximum duration corresponds to the Duration field that is typically used to set the basic NAV.

[0123] At the end of the duration of the OBSS interference, the destined station can finally switch back to its common operating band S1 with the primary channel P1 at step 740.

[0124] Figure 8a schematically illustrates a communication device 800 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.

[0125] The communication device 800 may preferably be a device such as a microcomputer, a workstation or a light portable device. The communication device 800 comprises a communication bus 813 to which there are preferably connected: a central processing unit 801 , such as a processor, denoted CPU; a memory 803 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 802 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 804.

[0126] Preferably the communication bus provides communication and interoperability between the various elements included in the communication device 800 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 800 directly or by means of another element of the communication device 800.

[0127] 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 802, in order to be stored in the memory of the communication device 800 before being executed.

[0128] 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).

[0129] Figure 8b is a block diagram schematically illustrating the architecture of the communication device 800, adapted to carry out, at least partially, the invention. As illustrated, device 800 comprises a physical (PHY) layer block 823, a MAC layer block 822, and an application layer block 821 .

[0130] The PHY layer block 823 (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.

[0131] The MAC layer block or controller 822 preferably comprises a MAC 802.11 layer 824 implementing conventional 802.1 1 be MAC operations, and additional block 825 for carrying out, at least partially, the invention. The MAC layer block 822 may optionally be implemented in software, which software is loaded into RAM 803 and executed by CPU 801 .

[0132] Preferably, the additional block 825, referred to as NPCA managing module which has different operations to implement parts of the invention, depending on the role played by the communication device 800.

[0133] MAC 802.11 layer 824 and NPCA Managing module 825 interact one with the other in order to process accurately communications over the medium, e.g., over secondary channels addressed to multiple BSSs according to embodiments of the invention.

[0134] On top of the Figure, application layer block 821 runs an application that generates and receives data packets, for example data packets such as a video stream. Application layer block 821 represents all the stack layers above MAC layer according to ISO standardization.

[0135] 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.

[0136] For example, although the description of embodiments of the invention has been 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.

[0137] 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.

[0138] 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

CLAIMS1 . A station of a Basic Service Set “BSS” having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondary channels being an anchor channel for non-primary channel access within the BSS, the station comprising a first radio configured to operate over the overall operating channel and a second radio configured to operate over a subset of the operating channel including the anchor channel and not the primary channel.

2. The station according to claim 1 , wherein the station is configured to perform access to the anchor channel, in response to receiving, using the second radio, a frame for switching channel access over the anchor channel.

3. The station according to claim 1 , wherein the first radio includes a transmit chain and a receive chain, and the second radio includes a receive chain.

4. The station according to claim 2, configured to switch the first radio from the primary channel to the anchor channel for performing the access to the anchor channel with the first radio.

5. The station according to claim 2, wherein the second radio includes a transmit chain and a receive chain, and the station is configured to perform the access to the anchor channel with the second radio.

6. The station according to claim 2, configured to switch the first radio from the operating channel to the anchor channel during a switching period overlapping a padding time provided in the frame for switching channel access.

7. The station according to claim 1 , configured to limit in time the communication over the secondary channel at a maximum duration, the maximum duration information being provided in the frame for switching channel access.

8. An initiating station of a Basic Service Set “BSS” having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondary channels being an anchor channel for non-primary channel access within the BSS, the initiating station being configured, in response to sensing an interfering frame from an overlapping BSS, OBSS, to switch to anchor channel access and to send a frame for switching channel access over the anchor channel to initiate anchor channel access switch to other stations of the BSS, the frame for switching channel access including an initial control frame “ICF” with an additional padding time.

9. The initiating station according to claim 8, wherein the additional padding time is of a duration adapted for a radio to switch between channels.

10. The initiating station according to claim 8, capable to read at least a duration field in a header of the interfering frame received from an interfering station over the primarychannel, and configured to limit in time the communication over the anchor channel at a maximum duration based on the duration field content.

11. The initiating station according to claim 8, capable to read at least a duration field in a header of the interfering frame received from an interfering station over the primary channel, and configured to provide, in the frame for switching channel access, a maximum duration information based on the duration field content.

12. A system comprising at least two stations of a Basic Service Set among which at least one station according to claim 1 and at least one initiating station according to claim 8.

13. A communication method for a station of a Basic Service Set “BSS” having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondary channels being an anchor channel for non-primary channel access within the BSS, the communication method comprising operating over the overall operating channel with a first radio, and operating over a subset of the operating channel including the anchor channel and not the primary channel with a second radio.

14. The method according to claim 13, comprising performing access to the anchor channel in response to receiving, using the second radio, a frame for switching channel access over the anchor channel.

15. The method according to claim 13, wherein operating over the overall operating channel comprises transmitting and receiving frames with the first radio, and operating over the subset of the operating channel comprises receiving frames with the second radio.

16. The method according to claim 14, comprising switching the first radio from the primary channel to the anchor channel to perform the access to the anchor channel with the first radio.

17. The method according to claim 14, wherein operating over the subset of the operating channel comprises transmitting and receiving frames with the second radio, and performing the access to the anchor channel uses the second radio.

18. The method according to claim 14, comprising switching the first radio from the operating channel to the anchor channel during a switching period overlapping during a padding time provided in the frame for switching channel access.

19. The method according to claim 13, comprising limiting in time the communication over the secondary channel at a maximum duration, the maximum duration information being provided in the frame for switching channel access.

20. An initiating method for switching channel access for a station of a Basic Service Set “BSS” having an operating channel made of a primary channel for primary channel access within the BSS and one or more secondary channels, one of the secondarychannels being an anchor channel for non-primary channel access within the BSS, the method including, in response to sensing an interfering frame from an overlapping BSS, OBSS, to switch to anchor channel access and to send a frame for switching channel access over the anchor channel to initiate NPCA switch to other stations of the BSS, the frame for switching channel access including an initial control frame with an additional padding time.

21. The method according to claim 20, wherein the additional padding time is of a duration adapted for a radio to switch between channels.

22. The method according to claim 21 , including reading at least a duration field in a header of the interfering frame received from an interfering station over the primary channel, and limiting in time the communication over the secondary channel at a maximum duration based on the duration field content.

23. The method according to claim 20, including reading at least a duration field in a header of the interfering frame received from an interfering station over the primary channel, and providing, in the frame for switching channel access, a maximum duration information based on the duration field content.

24. A switching channel access communication method of stations of a Basic Service Set among implementing a method according to claims 13 and 20.

25. 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 according to claim 13 and / or 20.

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