Procedures for soft preemption-based secondary channel access in WI-FI system

Abstract

Methods and devices are disclosed for performing secondary channel access (SCA) in a wireless network. In one method, a station (STA), e.g., an access point (AP) STA, determines that a primary channel is busy and sends a secondary channel access (SCA) request channel switch (RCS) frame to one or more target STAs to switch to a designated secondary channel. The STA receives a channel confirmation switch (CCS) message from at least one of the one or more target STAs and sends or receives one or more physical layer protocol data units (PPDUs) over the designated secondary channel. The STA switches back to the primary channel after a period of time, e.g., a SCA transmit opportunity (TXOP). Additional embodiments are disclosed.

Description

PROCEDURES FOR SOFT PREEMPTION-BASED SECONDARY CHANNEL ACCESS IN WI-FI SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 554,690, filed February 16, 2024, the contents of which are incorporated herein by reference.BACKGROUND

[0002] Secondary channel access (SCA) mechanisms allow an access point (AP) or non-AP stations (STA(s)) of a basic service set (BSS) to transmit or receive frames on one or more secondary subchannels when the primary subchannel is busy or occupied as observed or measured at either the transmitter side or receiver side or both sides by an OBSS (overlapping basic service set) transmission.

[0003] Switching the target STAs (potential transmitters and receivers of frames) to the secondary channel when the primary channel is busy may be more effective and efficient. However, informing the target STA(s) to switch to the secondary channel(s) is challenging since the primary channel is already busy, i.e., the primary channel is busy with one or more transmissions taking place in one or more OBSSs. A mechanism to request the target STAs to switch to the secondary channel(s) is an open problem.SUMMARY

[0004] Aspects of the disclosure may address the problem in cases when the primary channel is occupied by an OBSS transmission, to switch to a secondary channel (a k.a., an anchor channel) that may be triggered by a secondary channel access (SCA) initiator causing one or more SCA responders to switch to the anchor channel during the transmission opportunity (TXOP) in which the primary channel is busy (a.k.a., SCA TXOP).

[0005] In one aspect, the SCA initiator may negotiate with the SCA responder(s) certain service periods (ahead of time) in which they may expect the SCA initiator to initiate a SCA switching procedure. In another aspect the SCA initiator may negotiate with the SCA responder(s) for certain availability windows (ahead of time) in which they may expect the SCA initiator to initiate the procedure. These aspects may be referred to as soft-preemption-based SCA.

[0006] According to one aspect, a general procedure for soft preemption-based SCA is disclosed including five phases of SCA, definitions of behaviors for a SCA initiator, a SCA responder and OBSS APs enabling the procedure. Additional aspects relate to different switching operations for spatial reuse, soft preemption-based and transmission gaps-based SCA.

[0007] Additional aspects may relate to defining an ultra high reliability (UHR) physical layer protocol data unit (PPDU) carrying a request channel switch (RCS) frame and / or a procedure of switching to multiple secondary channels, referred to as a cascade procedure.

[0008] In one example, a method for a station (STA) may include determining that a primary channel is busy and sending a secondary channel access (SCA) request channel switch (RCS) message to one or more target STAs to switch to a designated secondary channel. The STA may send a request-to-send (RTS) message and receive a clear-to-send (CTS) message on the designated secondary channel to confirm a target STA of the one or more target STAs switched to the designated secondary channel. The STA may then send and / or receive one or more physical layer protocol data units (PPDUs) over the designated secondary channel with the confirmed target STA and switches back to the primary channel after a period of time. In one example, the STA receives a channel confirmation switch (CCS) message on the designated secondary channel from one of the one or more target STAs.

[0009] In an example, the period of time includes one of a SCA transmit opportunity (TXOP), a time after the SCA TXOP to send or receive an acknowledgement (ACK) of the one or more PPDUs, or a time shorter than the SCA TXOP to monitor the primary channel until the primary channel is not busy. In one example, the SCA request message comprises a trigger frame including a user info field specifying target SCA responders and resources on the designated secondary channel for target SCA responders to send the CCS message. In one example, prior to sending the SCA request, the method further includes the STA negotiating with the one or more target STAs one or more service periods or availability windows in which the one or more target STAs may expect to receive the SCA request. Additional embodiments are disclosed.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, wherein like reference numerals in the figures indicate like elements, and wherein:

[0011] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented;

[0012] FIG. 1 B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG 1A according to an embodiment;

[0013] FIG. 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0014] FIG. 1D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG 1A according to an embodiment;

[0015] FIG. 2 is a timing diagram showing an example of individual target wake time (TWT) operation;

[0016] FIG. 3 is a flow chart showing a general procedure of soft preemption-based secondary channel switching;

[0017] FIG. 4 is a message sequence diagram showing an example scenario 1 for soft preemption-based secondary channel access (SCA);

[0018] FIG. 5 is a message sequence diagram showing an example scenario 2 for soft preemption-based SCA;

[0019] FIG. 6 is a message sequence diagram showing an example scenario 3 for soft preemption-based secondary channel access with early switch back according to an embodiment;

[0020] FIG. 7 is a message sequence diagram showing an example scenario 4 for soft preemption-based secondary channel access with switch back just after a SCA transmit opportunity (TXOP) according to an embodiment;

[0021] FIG. 8 is a message sequence diagram showing an example scenario 5 for soft preemptionbased SCA for extended transmission using late switch back according to an embodiment;

[0022] FIG. 9 is message sequence diagram showing an example scenario 6 for soft preemption-based SCA using basic service set physical packet data units (BSS PPDUs) on the anchor channel and acknowledgement (ACK) on the primary channel according to an embodiment;

[0023] FIG. 10 is a message sequence diagram showing an example scenario 7 for soft preemptionbased SCA identifying successfully switched responders for downlink (DL) PPDUs according to an embodiment;

[0024] FIG. 11 is a message sequence diagram showing an example scenario 8 for soft preemptionbased SCA identifying successfully switched responders for uplink (UL) trigger-based (TB) PPDUs according to an embodiment;

[0025] FIG. 12 is a message sequence diagram showing an example scenario 9 for soft preemptionbased SCA with two-way handshaking according to an embodiment;

[0026] FIG. 13 is a flow diagram showing a method for a non-access point (AP) STA as a SCA initiator for UL single user (SU) PPDU anchor transmissions using three-way handshaking according to an embodiment;

[0027] FIG. 14 is a flow diagram showing a method for a non-AP STA as a SCA initiator for anchor channel UL SU PPDU transmission based on two-way handshaking according to an embodiment;

[0028] FIG. 15 is a flow diagram showing a method for a non-AP STA acting as a SCA responder and APSTA as a SCA initiator using three-way handshaking in anchor channel DL transmission SU / multi-user (MU)PPDUs according to an embodiment;

[0029] FIG. 16 is a flow diagram showing a method for a non-AP STA as a SCA responder in anchor channel DL transmission of SU / MU PPDU based on two-way handshaking according to an embodiment;

[0030] FIG. 17 is a diagram showing an example of transmit power adjustment of overlapping basic service set (OBSS) packet detection (PD)-based spatial reuse (SR) operation of an embodiment;

[0031] FIG. 18 is a network diagram showing an exemplary scenario for the favorable conditions to perform the soft preemption procedure according to one embodiment;

[0032] FIG. 19 is a message sequence diagram showing an exemplary illustration of the transmission gaps in the OBSS PPDUs which may be used for SCA changing according to an embodiment;

[0033] FIG. 20 is a message sequence diagram showing an exemplary scenario for soft preemptionbased SCA in a multiple secondary channel scenario when the SCA initiator senses a first secondary channel is busy according to an embodiment; and

[0034] FIG. 21 is a message sequence diagram showing an exemplary scenario for soft preemptionbased SCA in the multiple secondary channel scenario when the SCA responder(s) senses a first secondary channel is busy according to another embodiment.DETAILED DESCRIPTION

[0035] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), singlecarrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S- OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0036] As shown in FIG. 1A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (ON) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though itwill be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a station (STA), may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operatingon commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a UE.

[0037] The communications systems 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the Internet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an eNode B (eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as a gNode B (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0038] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, and the like. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0039] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0040] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed Uplink (UL) Packet Access (HSUPA).

[0041] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0042] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access , which may establish the air interface 116 using NR.

[0043] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g , an eNB and a gNB).

[0044] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e , Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0045] The base station 114b in FIG 1A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106.

[0046] The RAN 104 may be in communication with the CN 106, which may be any type of network configured to provide voice, data, applications, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104 and / or the CN 106 may be in direct or indirect communicationwith other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may be utilizing a NR radio technology, the ON 106 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0047] The CN 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and / or the internet protocol (IP) in the TCP / IP internet protocol suite. The networks 112 may include wired and / or wireless communications networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0048] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1 A may be configured to communicate with the base station 114a, which may employ a cellularbased radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0049] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0050] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0051] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0052] Although the transmit / receive element 122 is depicted in FIG. 1 B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0053] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit / receive element 122 and to demodulate the signals that are received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11 , for example.

[0054] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit) The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0055] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li- ion), etc.), solar cells, fuel cells, and the like.

[0056] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated thatthe WTRU 102 may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment

[0057] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a handsfree headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and / or Augmented Reality (VR / AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors. The sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor and the like.

[0058] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e g., associated with particular subframes for both the UL (e.g., for transmission) and DL (e.g. , for reception) may be concurrent and / or simultaneous. The full duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e g., for transmission) or the DL (e g., for reception)).

[0059] FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0060] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0061] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, and the like. As shown in FIG. 1 C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0062] The CN 106 shown in FIG. 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0063] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA

[0064] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0065] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0066] The CN 106 may facilitate communications with other networks For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0067] Although the WTRU is described in FIGS. 1A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0068] In representative embodiments, the other network 112 may be a WLAN.

[0069] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example,where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA The traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. The peer-to- peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad-hoc” mode of communication.

[0070] When using the 802.11 ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example in 802.11 systems. For CSMA / CA, the STAs (e.g., every STA), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0071] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0072] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two noncontiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0073] Sub 1 GHz modes of operation are supported by 802.11 af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11af and 802.11ah relative to those used in 802.11n, and 802.11ac. 802.11 af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type Control / Machine- Type Communications (MTC), such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g , only support for) certain and / or limitedbandwidths The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0074] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802 11 n, 802.11ac, 802.11af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode) transmitting to the AP, all available frequency bands may be considered busy even though a majority of the available frequency bands remains idle.

[0075] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah is 6 MHz to 26 MHz depending on the country code.

[0076] FIG. 1 D is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0077] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0078] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wirelesstransmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing a varying number of OFDM symbols and / or lasting varying lengths of absolute time).

[0079] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with / connect to gNBs 180a, 180b, 180c while also communicating with / connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non- standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for servicing WTRUs 102a, 102b, 102c.

[0080] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, DC, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0081] The CN 106 shown in FIG. 1 D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0082] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of non-access stratum (NAS) signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, and the like The AMF 182a, 182b may provide a control plane function forswitching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0083] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 106 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 106 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet-based, and the like.

[0084] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, and the like.

[0085] The CN 106 may facilitate communications with other networks For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local DN 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0086] In view of FIGs. 1A-1 D, and the corresponding description of FIGs. 1A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0087] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network The emulation device maybe directly coupled to another device for purposes of testing and / or performing testing using over-the-air wireless communications.

[0088] The one or more emulation devices may perform the one or more, including all, functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0089] Overview of WLAN Systems. A WLAN in Infrastructure Basic Service Set (BSS) mode has an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP typically has access or interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in and out of the BSS. Traffic to STAs that originates from outside the BSS arrives through the AP and is delivered to the STAs. Traffic originating from STAs to destinations outside the BSS is sent to the AP to be delivered to the respective destinations. Traffic between STAs within the BSS may also be sent through the AP where the source STA sends traffic to the AP and the AP delivers the traffic to the destination STA. Such traffic between STAs within a BSS is really peer-to-peer traffic. Such peer-to-peer traffic may also be sent directly between the source and destination STAs with a direct link setup (DLS) using an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode has no AP, and / or STAs, communicating directly with each other. This mode of communication is referred to as an “ad-hoc” mode of communication.

[0090] Using the 802 11ac infrastructure mode of operation, the AP may transmit a beacon on a fixed channel, usually the primary channel This channel may be 20 MHz wide, and is the operating channel of the BSS. This channel is also used by the STAs to establish a connection with the AP. The fundamental channel access mechanism in an 802.11 system is Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA). In this mode of operation, every STA, including the AP, will sense the occupancy or vacancy of the primary channel. If the channel is detected to be busy, the STA backs off. Hence only one STA may transmit at any given time in a given BSS.

[0091] In 802.11n, High Throughput (HT) STAs may also use a 40 MHz wide channel for communication. This is achieved by combining the primary 20 MHz channel, with an adjacent 20 MHz channel to form a 40 MHz wide contiguous channel

[0092] In 802.11 ac, Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and 160 MHz wide channels. The 40 MHz, and 80 MHz, channels are formed by combining contiguous 20 MHz channels similar to 802.11 n described above. A160 MHz channel may be formed either by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, this may also be referredto as an 80+80 configuration. For the 80+80 configuration, at the transmitter, the data, after channel encoding, is passed through a segment parser that divides it into two streams. IFFT and time domain processing are done on each stream separately. The streams are then mapped on to the two channels, and the data is transmitted. At the receiver, this mechanism is reversed, and the combined data is sent to the MAC.

[0093] Sub 1 GHz modes of operation are supported by 802.11 af, and 802.1 1 ah. For these specifications the channel operating bandwidths, and carriers, are reduced relative to those used in 802.11 n, and 802.11 ac. 802.1 1 af supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.1 1 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. A possible use case for 802.11 ah is support for Meter Type Control (MTC) devices in a macro coverage area. MTC devices may have limited capabilities including only support for limited bandwidths, but also include a requirement for a very long battery life.

[0094] WLAN systems which support multiple channels, and channel widths, such as 802.11n, 802.11 ac, 802.1 1 af, and 802 11 ah, include a channel which is designated as the primary channel. The primary channel may, but not necessarily, have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel is therefore limited by the STA, of all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.1 1 ah, the primary channel may be 1 MHz wide if there are STAs (e.g MTC type devices) that only support a 1 MHz mode even if the AP, and other STAs in the BSS, may support a 2 M Hz, 4 M Hz, 8 MHz, 16 M Hz, or other channel bandwidth operating modes. All carrier sensing, and NAV settings, depend on the status of the primary channel; i.e., if the primary channel is busy, for example, due to a STA supporting only a 1 MHz operating mode is transmitting to the AP, then the entire available frequency bands are considered busy even though majority of it stays idle and available.

[0095] In the United States, the available frequency bands which may be used by 802.1 1 ah are from 902 MHz to 928 MHz. In Korea it is from 917.5 MHz to 923.5 MHz; and in Japan, it is from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.1 1 ah is 6 MHz to 26 MHz depending on the country code.

[0096] Existing Solutions for Secondary Channel Access include Subchannel Selective Transmission (SST). Starting from 802 1 1 ax, an SST mechanism is defined to allow a STA to transmit and receive on a secondary channel. A high efficiency (HE) SST non-AP STA and an HE SST AP may set up SST operation by negotiating a trigger enabled Target Wake Time (TWT) using individual TWT agreements. Referring to FIG. 2, an example of individual TWT operation 200 is shown .

[0097] The TWT element is shown in in TABLE 1 .TABLE 1 : TWT element

[0098] The Control field of the TWT element defined in 802.11 be is shown in TABLE 2.

[0099] The Broadcast subfield in the Negotiation Type subfield indicates whether the TWT element is for broadcast TWT or individual TWT. If the Broadcast field of the Negotiation Type subfield is 0 (the TWT element is for individual TWT), then only one Individual TWT parameter set is contained in the TWT element.

[0100] The Individual TWT Parameter Info field defined in 802.11 be is shown in TABLE 3. The TWT Channel subfield in the Individual TWT Parameter Set field indicates the subchannels the STA may need to monitor.TABLE 3: Individual TWT Parameter Set field defined in 802.11 be

[0101] The SST operation allows a non-AP STA to operate on a secondary 20MHz subchannel or a secondary 80MHz subchannel in the negotiated TWT service period (SP). The non-AP STA shall be available at the TWT start time and shall not access the medium in the subchannel using distributed coordination function (DCF) or enhanced distributed channel access (EDCAF). Instead, the channel access for non-AP STA during the SST operation is trigger based (TB), meaning that the AP grants uplink resources for the non-AP STAs to perform uplink transmission A non-AP STA may include a Channel Switch Timing element in (Re)Association Request frames it transmits to an AP to indicate the time required by the STA to switch between different subchannels.

[0102] The IEEE 802.11 Ultra High Reliability (UHR) Study Group was formed in September 2022. UHR is considered as the next major revision to IEEE 802 11 standards following 802.11be, which is currently in the Working Group Letter Ballot Stage UHR is formed to explore the possibility to improve reliability, support low latency traffic and further increase peak throughput and improve efficiency of the IEEE 802.11 networks. Secondary channel access was discussed in 802.11 bn and UHR SG.

[0103] As mentioned previously, Secondary Channel Access (SCA) is an issue requiring improved solutions. Secondary channel access mechanisms allow an AP or non-AP STA(s) to transmit or receive frames on one or more secondary subchannels when the primary subchannel is busy or occupied, observed or measured, either at the transmitter side, the receiver side or both sides, by an overlapping basic service set (OBSS) transmission.

[0104] Switching the target STAs (potential transmitters and receivers of frames) to the secondary channel when the primary channel is busy may be more effective and efficient. However, informing target STA(s) toswitch to the secondary channel(s) is challenging since the primary channel is already busy, i.e., the primary channel is busy with one or more transmissions taking place in one or more OBSSs. A mechanism to request the target ST As to switch to the secondary channel(s) is an open problem.

[0105] Embodiments for preemption-based secondary channel access terminology are disclosed. The following descriptions are presented as example terminology..

[0106] Soft Preemption-refers to a transmission using the resources that are the same as, or part of, the ones used by an ongoing transmission (preempted transmission). The preempting transmission may cause interference to the ongoing transmission.

[0107] SCA Initiator-refers the STA that initiates the switching to an anchor channel by sending Request Channel Switch (RCS) frame on a busy primary channel.

[0108] SCA Responder-refers to the STA that receives the RCS frame that initiates switching to the anchor channel and responds to it by switching to the anchor channel.

[0109] Anchor Channel-refers to a designated non-primary channel that is announced to the STAs in a BSS by the associated AP to be used to access the available secondary channels when the primary channel is occupied, e.g., by an OBSS transmission.

[0110] SCA transmit opportunity (TXOP)-refers to the TXOP duration in which the primary channel is occupied by an OBSS transmission and provides a potential opportunity for the STAs in a BSS to switch to the secondary channel(s).

[0111] Basic service set (BSS) physical layer protocol data unit (PPDU)-refers to a PPDU that is transmitted by the SCA initiator to the SCA responder or vice versa.

[0112] Embodiments for a soft preemption procedure for secondary channel access using a single anchor channel are disclosed. In cases when the primary channel is occupied by an OBSS transmission, switching to a secondary channel (a.k.a., anchor channel) may be triggered by a SCA initiator, causing one or more SCA responders to switch to the anchor channel during the TXOP in which the primary channel is busy (a.k.a., SCA TXOP), as illustrated in FIG 4.

[0113] In one embodiment, as illustrated in FIG. 3, a procedure 300 for a STA switching to the secondary channel may include five main phases (1 )-(5) below.

[0114] (1) Primary Channel Assessment (305)- in this phase the SCA initiator performs clear channel assessment (CCA) and determines that the primary channel is busy.

[0115] (2) Switching to a Secondary Channel (310)- in this phase the SCA initiator requests one or more target STAs (SCA responders) to switch to the designated secondary channel (a.k.a., anchor channel).

[0116] (3) Confirmation of Switching (315)- in this phase the SCA initiator may perform a frame exchange with the SCA responder(s) to confirm that the switching has been performed successfully.

[0117] (4) Transmission of PPDUs (320)- in this phase the SCA initiator and / or the SCA responder(s) may transmit and / or receive one or more PPDUs using the anchor channel, e.g., as a temporary primary channel. These PPDU may carry data, management, control, or action frames.

[0118] (5) Switching Back to Primary Channel (325)- in this phase the SCA initiator and / or the SCA responder(s) switch from the anchor channel back to the primary channel.

[0119] During the clear channel assessment (CCA) in phase 1 (i.e., Primary Channel Assessment 305), the SCA initiator may perform one or both Energy Detection (ED) and Preamble Detection (PD) on the primary channel to determine that the primary channel is busy. As an example, the primary channel may be busy due to a transmission from non-Wi-Fi technology or Wi-Fi technology. An assumption considered in this disclosure is that the SCA initiator may be able to determine that the primary channel is occupied by a transmission from an OBSS. The SCA initiator may be able to determine that the current transmission is from the OBSS by, for example, decoding the BSS Color and TXOP fields in the preamble of the PPDU occupying the primary channel (e g., in case of 11 ax / .11 be OBSSs).

[0120] In one method, the general procedure 300 illustrated in FIG. 3 may also be applied in cases where the primary channel is determined busy due to non-Wi-Fi interference. In one example, the SCA initiator and / or the SCA responder(s) may start a countdown timer once they switch successfully to the anchor channel, and they may start switching back to the primary phase once the timer expires / resets to zero In another example, the countdown timer may start with any one of the transmission of the RCS frame, the reception of the RCS frame, the transmission of the CCS, or the reception of the CCS.

[0121] In one embodiment, the SCA responder(s) that implement the capability to perform the procedure 300 in FIG. 3 may negotiate the conditions under which they may stay awake when they determine that the primary channel is busy. In one method, the SCA initiator may negotiate with the SCA responder(s) certain service periods (SPs) (ahead of time) in which they may expect the SCA initiator to initiate the procedure. In another method, the SCA initiator may negotiate with the SCA responder(s) certain availability windows (ahead of time) in which they may expect the SCA initiator to initiate the procedure.

[0122] Referring to FIG. 4, an example method 400 is shown for one embodiment in which the SCA initiator may be the transmitter of a PPDU 430, to the SCA responder(s) which is the intended receiver of this PPDU. In one example, the SCA initiator may be the AP and the SCA responder(s) may be one or more non-AP STAs (e g., using downlink single user (SU) PPDU and / or downlink multi-user (MU) PPDU). In another example, the SCA initiator may be the non-AP STA and the SCA responder may be the AP (e.g., in the case of uplink SU PPDU).

[0123] Referring to FIG. 5, an example method 500 is shown for an embodiment in which the SCA initiator may be the receiver of a PPDU from the SCA responder, which is the intended transmitter of this PPDU. In one example, the SCA initiator may be the AP and the SCA responder(s) may be one or more non-AP STA(s)(e g., uplink SU PPDU or uplink trigger-based (TB) PPDU). Various different combinations of SCA initiator / responder roles are listed in TABLE 4 below.

[0124] In certain embodiments, the SCA initiator (e.g. , the AP) may trigger one or more non-AP STAs (SCA responders) to switch to the anchor channel, then the SCA initiator may transmit a PPDU in the downlink to the SCA responder(s) or trigger the SCA responder(s) to transmit a PPDU in the uplink. In other embodiments, the SCA initiator (e.g., a non-AP STA) may trigger the AP (SCA responder) to switch to the anchor channel, then the SCA initiator (non-AP STA) may transmit a PPDU in the uplink.

[0125] In various embodiments, the target transmitters / receivers of PPDUs (i.e., FIG. 4 PPDU 430 / FIG. 5 PPDU 530) are triggered to switch to the anchor channel during the TXOP in which the primary channel may be occupied by an OBSS transmission. This TXOP may be referred to as SCA TXOP.TABLE 4: Potential PPDU Types for Different Combinations of SCA Initiator / Responder Roles

[0126] Example behavior of the STAs (i.e., AP STA and non-AP STA) according to example embodiments are now described. Referring back to the example FIG 4 method 400, the SCA initiator may initiate the procedure of switching from the primary channel 401 to the secondary channel (a.k.a., anchor channel 403) by sending 405 a Request Channel Switch (RCS) frame addressed to one or more SCA responders (i e., target STAs for transmitting or receiving potential PPDUs). At step 410, the SCA initiator may then switch to the anchor channel and the SCA responders may switch to the anchor channel if the RCS frame from the initiator is received successfully. The SCA initiator may then perform a full clear channel assessment (CCA) on the anchor channel. In example embodiments, a full CCA may include physical CCA 415 by listening to the channel and virtual CCA by sending a request to send (RTS)Zmulti-user request to send (MU-RTS) 420 on the anchor channel and waiting for a clear to send (CTS) response 425 from the SCA responder(s). The SCA initiator may then send one or more PPDUs 430 to the one or more SCA responders. The SCA responder(s) may then send an acknowledgement (ACK) 435 to the SCA initiator on the anchor channel. Additionally, or alternatively, the SCA responders may send the ACK on the primary channel (not shown in FIG. 4) after switching 440 back to the primary channel (see, e.g., FIG. 9 method 900).

[0127] In various embodiments, and Indication To Switch (ITS) and Request Channel Switch (RCS) may be used interchangeably, both referring to the same frame. Additionally, anchor channel(s) and secondary channel(s) may be used interchangeably, referring to a channel other than the primary channel.

[0128] In certain embodiments (e.g., FIG. 4, FIG. 5, and FIG. 7), the SCA initiator and / or the SCA responder(s) may stay in the anchor channel for the duration of the SCA TXOP and then switch back to the primary channel. Additionally, or alternatively, the SCA initiator and / or the SCA responder(s) may stay in the anchor channel for a longer time than the SCA TXOP to complete the ongoing transmission and send the ACK response (see, e.g., FIG. 8). Additionally, or alternatively, the SCA initiator and / or the SCA responder(s) may stay in the anchor channel for shorter time than the SCA TXOP, and then switch back and continue monitoring the primary channel until the primary channel gets released (see, e.g., FIG. 6).

[0129] In one embodiment, the SCA initiator, after successfully switching to the anchor channel, may send a trigger frame on the anchor channel addressed to the SCA responders to solicit a response from each SCA responder confirming which SCA responder has switched to the anchor channel successfully. The trigger frame may include a User Info list in which each target SCA responder has a User Info field to specify a resource on the anchor channel in which the SCA responder may send a response to indicate that it has switched to the anchor channel successfully, as illustrated by the example embodiment of FIG. 10. The response from each SCA responder may also include a list of secondary channels that are accessible or available by the responder via an indication format, e.g , in a bit map format,.

[0130] In one embodiment, the trigger frame (sent by the SCA initiator) may be a Polling trigger frame and the response (solicited from the SCA responders) may be a CTS-To-Self frame. In another example, the trigger frame may be a null-data packet (NDP) Feedback Report Poll (NFRP) trigger frame and the response may be a NDP Feedback Report (NFR).

[0131] In one embodiment, the SCA initiator may send the BSS PPDUs to all the SCA responders indicated in a RCS frame, which may be a RTS frame including SCA information, whether they responded or not to the RCS / RTS frame with a confirm channel switch (CCS) frame, which in some examples, may be a CTS frame.

[0132] In one embodiment, the SCA initiator may trigger all the SCA responders indicated in the RCS frame to send BSS TB PPDUs whether they responded or not to the RTS frame with a CTS / CCS frame.

[0133] In one embodiment, the SCA initiator may send the BSS PPDUs to all the SCA responders indicated in the RCS frame, only if it received a CTS frame from one or more of the SCA responders. If the SCA initiator did not receive a response from any of the SCA responders, it may refrain from transmitting any PPDUs on the anchor channel.

[0134] In one embodiment, the SCA initiator may trigger all the SCA responders indicated in the RCS frame to transmit BSS trigger-based (TB) PPDUs only if it received a CTS frame from one or more of the SCA responders If the SCA initiator did not receive a response from any of the SCA responders, it may refrain from triggering any of the SCA responders.

[0135] In one example, the SCA initiator may send the BSS PPDUs only to the SCA responders who responded to a trigger frame soliciting a response to indicate the successful switching to the anchor channel. In one example, the SCA initiator may send the BSS PPDUs to the SCA responders who transmitted a CTS- To-Self (CTS2S) as a response to the Polling trigger frame. In another example, the SCA initiator may send the BSS PPDUs to the SCA responders who transmitted an NFR as a response to the NFRP trigger frame.

[0136] In one embodiment, the SCA initiator may trigger only the SCA responders who responded to a trigger frame soliciting a response to indicate the successful switching to the anchor channel to send TB PPDUs on the anchor channel. In one example, the SCA initiator may trigger transmitting BSS TB PPDUs from the SCA responders who transmitted a CTS-To-Self as a response to the Polling trigger frame. In another example, the SCA initiator may trigger transmitting BSS TB PPDUs from the SCA responders who transmitted an NFR as a response to the NFRP trigger frame, as shown in the example embodiment of FIG. 11

[0137] In one embodiment, the SCA initiator may switch to the anchor channel and wait for a Confirm Channel Switch (CCS) frame sent by the SCA responder(s) to confirm the successful switching to the anchor channel. The SCA initiator may then send BSS PPDUs to the SCA responder or trigger the SCA responders to transmit BSS TB PPDUs, e.g., as shown in the example embodiment of FIG. 12.

[0138] Referring back to FIG. 4 method 400, an exemplary scenario 1 is shown where the SCA initiator is the transmitter of the potential BSS PPDUs 430 and the SCA responder(s) are the receivers. The transmission of the BSS PPDUs 430 is preferably managed such that the transmission occupies most of the SCA TXOP 402 and allows the ACK(s) to be received on the anchor channel 403 just before the SCA TXOP 402 is elapsed. In this scenario, the switch 440 back to the primary channel 401 starts just after the SCA TXOP is elapsed.

[0139] Referring to FIG. 5 method 500, an exemplary scenario 2 is shown, which is similar to scenario 1 of FIG. 4, except that the SCA initiator is the receiver of the potential BSS PPDUs 530 and the SCA responder is the transmitter. FIG. 5 method 500, as well as for other subsequent FIGs., may be similar to FIG. 4 method 400 and description of related elements and steps may be omitted as duplicative.

[0140] Referring to FIG. 6 an example scenario 3 is shown for method 600 where the transmission of the BSS PPDUs 630 and the receiving of the ACK 635 finish earlier than the SCA TXOP 602 and the switch back 640 to the primary channel starts early before the SCA TXOP is elapsed. This example embodiment may be referred to as SCA with early switch back.

[0141] In one embodiment, referring to FIG. 7, an example scenario 4 is shown for a method 700 where the transmission of the BSS PPDUs 730 and the receiving of the ACK 735 finish earlier than the SCA TXOP 702, but the switch back 740 to the primary channel waits until the SCA TXOP 702 is elapsed.

[0142] In one embodiment, referring to FIG. 8, an example scenario 5 is shown for method 800, where the transmission of the BSS PPDUs 830 and the receiving of the ACK 835 finish later than the SCA TXOP 802 and then the switch back 840 to the primary channel starts after the ACK 835. This example embodiment may be referred to a SCA with late switch back.

[0143] In one embodiment, referring to FIG. 9 an example scenario 6 is shown in method 900 where the transmission of the BSS PPDUs 930 finishes later than the SCA TXOP 902, then the switch back 940 to the primary channel starts, then the ACK 935 is sent / received on the primary channel In an example, the SCA responder performs a CCA 937 on the primary channel before sending ACK 935.

[0144] In one embodiment, referring to FIG. 10, an example scenario 7 is shown in method 1000 where the SCA initiator transmits a trigger frame 1027 on the anchor channel to solicit confirmations from the SCA responder(s) who switched successfully to the anchor channel (e.g., a Polling / CTS-to-Self (CTS-TS) or NFRP / NFR). The SCA initiator then either transmits one or more BSS PPDUs 1030 to the SCA responders or, as shown in FIG. 11 method 1100, trigger frame 1127 solicits the SCA responder to transmit one or more BSS TB PPDUs 1130.

[0145] In one embodiment, referring to FIG. 12, an example scenario 9 is shown in method 1200 which represents a two-way handshaking alternative. In scenario 9, the SCA initiator transmits the Request Channel Switch (RCS) 1205 on the primary channel, switches to the anchor channel, and monitors the anchor channel to receive a Confirm Channel Switch (CCS) 1225 before starting the transmission of the BSS PPDUs 1230.

[0146] Referring to FIG. 13, an example method 1300 is shown for a non-AP STA acting as a SCA initiator and AP STA as responder using three-way handshaking for UL single user (SU) transmission of PPDUs on an anchor channel. It is noted for this example embodiment, the SCA initiator sends an ITS / RTS to change channels, then solicits an indication of channel change on the new channel from the SCA responder and receives a confirmation of channel change from the SCA responder, i.e., three-way handshaking. It is worth noting that Indication To Switch (ITS) and Request Channel Switch (RCS) may be used interchangeably, both referring to the same frame.

[0147] As with any method disclosed herein, steps and / or elements of method 1300 may be omitted, modified, performed in different orders and / or combined with other example embodiments disclosed herein.

[0148] The SCA initiator (e.g., non-AP STA) performs 1305 full CCA on the primary channel (Physical CCA + Virtual CCA) and finds out that the primary BSS channel is occupied by an OBSS transmission If 1310 the SCA initiator (non-AP STA) has queued packets to send to the SCA responder (AP), the SCA initiator (non-AP STA) may initiate 1320 switching to the anchor channel by sending an indication to switch (ITS) channels to a second channel, e.g., an RCS frame on the primary channel, and then switches 1365 to the second channel, a.k.a., an anchor channel If 1310, the SCA initiator (non-AP STA) has no queued packets it may set the NAV 1315 and go in a doze mode. In one example, the SCA initiator adjusts the transmit power of the PPDU carrying the ITS / RCS frame such that the SCA responder can receive 1325 the PPDU successfully.

[0149] If 1325 the RCS frame is received successfully by the SCA responder (AP), the SCA responder switches 1335 to the anchor channel, performs CCA and monitors the anchor channel waiting for an RTS frame from the SCA initiator.

[0150] If 1325 the SCA responder did not receive the PPDU carrying the RCS, it may keep monitoring the primary channel or it may set 1330 the network allocation vector (NAV) and may go in a dose mode. At step 1365, the SCA initiator sends an RTS frame or other indication soliciting confirmation of channel change by the SCA responder, e.g., a polling frame, a trigger frame, etc., and monitors the channel waiting for the SCA responder to respond with an indication confirming channel change, e g., a CTS frame.

[0151] If 1340 the SCA responder receives the RTS frame successfully it responds 1350 with the CTS frame. If 1340 the SCA responder did not receive the RTS frame successfully, it may switch back 1345 to the primary channel, wait for another RTS, or wait until the SCA TXOP is elapsed and then switch back to the primary channel If 1370 the SCA initiator receives the CTS frame successfully, it transmits 1380 one or more BSS PPDUs to the SCA responder, monitors the channel to receive the ACK, and then switches back 1385 to the primary channel, e.g., after a period o time If 1370 the SCA initiator does not receive the CTS frame successfully, at step 1375 it may switch back to the primary channel, send another RTS on the anchor channel, or wait until the SCA TXOP is elapsed and then switch back to the primary channel.

[0152] After completing the successful reception of one or more BSS PPDUs at step 1355, the SCA responder may respond 1360 with an ACK on the anchor channel and switch back to the primary channel, switch back to the primary channel and then respond with ACK on the primary channel, and / or wait until SCA TXOP is elapsed and switch back to the primary channel.

[0153] Referring to FIG. 14, an example method 1400 is shown for a non-AP STA acting as a SCA initiator and AP STA as responder using two-way handshaking for UL single user (SU) transmission of PPDUs) on an anchor channel. As with any method disclosed herein, steps and / or elements of method 1400 may be omitted, modified, performed in different orders and / or combined with other example embodiments disclosed herein.

[0154] In this example, the SCA initiator (e.g., non-AP STA) performs 1405 full CCA (i.e., Physical CCA + Virtual CCA) on a first BSS channel, e.g., primary channel, and finds out that the primary channel is occupied by an OBSS transmission. If 1410 the SCA initiator (non-AP STA) has queued packets to send to the SCA responder (AP), the SCA initiator (non-AP STA) may initiate 1415 switching to a second BSS channel, e.g , the anchor channel, by sending an indication to switch / ( I TS) / req uest channel switch (RCS) frame on the primary channel, and then switches 1420 to a second BSS channel, e.g., an indicated / designated anchor channel. In an example, the SCA initiator adjusts the transmit power of the PPDU carrying the RCS frame such that the SCA responder can receive the PPDU successfully. If 1410 the SCA initiator (non-AP STA) has no queued packets it may set 1425 the NAV and go in a doze mode.

[0155] If 1430 the RCS frame is received successfully by the SCA responder (AP), the SCA responder switches 1435 to the anchor channel, performs CCA on the anchor channel and transmits an indication of channel change, e.g., a clear to send (CTS) / confirm channel switch (CCS) frame to the SCA initiator. If 1430 the SCA responder did not receive the PPDU carrying the ITS / RCS, it may keep monitoring the primary channel or it may set 1440 the NAV and go in a dose mode.

[0156] At step 1445, if the SCA initiator receives the CCS frame successfully, it transmits 1450 one or more BSS PPDUs to the SCA responder, monitors 1455 the channel to receive the ACK, and then switches back to the primary channel. If 1445 the SCA initiator does not receive the CCS frame successfully, it may switch 1460 back to the primary channel, wait for another CCS, or wait until the SCA TXOP is elapsed and then switch back to the primary channel.

[0157] If 1465 the SCA responder receives PPDUs having its address, the AP STA receives 1470 the PPDUs. In one example, the PPDUs are received x interframe spacing (xlFS) after the CTS is sent, here x corresponds to a type of IFS. After completing the successful reception of one or more BSS PPDUs, the SCA responder may respond 1475 with ACK on the anchor channel and switch back to the primary channel, switch back to the primary channel and then respond with ACK on the primary channel, and / or wait until SCA TXOP is elapsed and switch back to the primary channel Otherwise, if 1465 the SCA responder does not receive PPDUs addressed to it, the responder may switch 1480 back to the primary channel immediately, send another CCS or wait for the SCA TXOP to elapse and switch back to the primary channel.

[0158] Referring to FIG. 15, an example method 1500 for a non-AP STA acting as a SCA responder and AP STA as a SCA initiator is shown using three-way handshaking in anchor channel DL single user (S U) / multi- user (MU) transmission of PPDUs As with any method disclosed herein, steps and / or elements of method 1500 may be omitted, modified, performed in different orders and / or combined with other example embodiments disclosed herein.

[0159] At step 1505, the SCA initiator (e g., AP STA) may perform full CCA (Physical CCA + Virtual CCA) on a first channel, i.e the primary BSS channel and finds out that the primary channel is occupied by an OBSS transmission. If 1510 the SCA initiator has queued packets to send to the SCA responder (e.g., non-AP STA), the SCA initiator (AP STA) may initiate 1515 switching to the anchor channel by sending an ITS / RCS frame on the primary channel, and then switch 1520 to the anchor channel. If 1510 the SCA initiator (AP STA) has no queued packets it may set 1525 the NAV and go in a doze mode. In one example, the SCA initiator adjusts the transmit power of the PPDU carrying the RCS frame such that the SCA responder can receive the PPDU successfully, e.g., using spatial reuse (SR) parameters.

[0160] At step 1530, if the ITS / RCS frame is received successfully by the SCA responder (non-AP STA), the SCA responder switches 1535 to the anchor channel, may perform CCA and monitors the anchor channel for an indication soliciting channel change confirmation, e.g., an RTS frame, from the SCA initiator (sent at step 1520, where the SCA initiator sends an RTS frame on the anchor channel and monitors the channel waiting for the SCA responder to respond with a confirmation of channel change indication, e.g., a CTS frame). If 1530 the SCA responder did not receive the PPDU carrying the RCS, it may continue monitoring the primary channel or it may set 1540 the NAV and go in a dose mode.

[0161] If 1537 the SCA responder receives the RTS frame successfully it responds 1545 with a CTS frame. If 1537 the SCA responder did not receive the RTS frame successfully, it may switch back 1539 to the primarychannel, wait for another RTS, or wait until the SCA TXOP is elapsed and then switch back to the primary channel.

[0162] At step 1550 if the SCA initiator receives the CTS frame successfully, it transmits 1555 one or more BSS PPDUs to the SCA responder, monitors 1560 the channel to receive the ACK, and then switches back to the primary channel. As an alternative, the SCA initiator may switch back to the primary channel as the ACK may be sent by the SCA responder on the primary channel. If 1550 the SCA initiator does not receive the CTS frame successfully, at step 1565, it may switch back 1565 to the primary channel, send another RTS, or wait until the SCA TXOP is elapsed and then switch back to the primary channel.

[0163] After completing the successful reception of one or more BSS PPDUs at step 1570, the SCA responder may respond 1575 with an ACK on the anchor channel and switch back to the primary channel, switch back to the primary channel and then respond with ACK on the primary channel, and / or wait until SCA TXOP is elapsed and switch back to the primary channel.

[0164] Referring to FIG. 16, an example method 1600 for a non-AP STA acting as a SCA responder and an AP STA acting as an SCA initiator using two-way handshaking in anchor channel DL single user (SU)Zmulti- user (MU) transmission of PPDUs As with any method disclosed herein, steps and / or elements of method 1600 may be omitted, modified, performed in different orders and / or combined with other example embodiments disclosed herein.

[0165] At step 1605, the SCA initiator (AP STA) performs full CCA (e.g., Physical CCA + Virtual CCA) on a first channel of the BSS, e.g., the primary channel, and finds out that the primary channel is occupied by / busy from an OBSS transmission. If 1610 the SCA initiator (AP STA) has queued packets to send to the SCA responder (non-AP STA), the SCA initiator (AP STA) may initiate 1615 switching to the anchor channel by sending an ITS / RCS frame on the primary channel, and then switch 1620 to a second BSS channel, e.g , the anchor channel. If 1610 the SCA initiator (AP STA) has no queued packets it may set 1625 the NAV and go in a doze mode. As in other embodiments, the SCA initiator may adjust the transmit power, e g., using spatial reuse parameters, of the PPDU carrying the ITS / RCS frame such that the SCA responder can receive the PPDU successfully, despite the primary channel being detected busy from the OBSS transmission(s).

[0166] At step 1630, if the ITS / RCS frame is received successfully by the SCA responder (non-AP), the SCA responder switches 1635 to the anchor channel, performs CCA and transmits, to the SCA initiator, an indication to confirm channel change to the anchor channel, e.g., a Confirm Channel Switch (CCS) frame, a CTS, a CTS to self (CTSTS) etc If 1630 the SCA responder did not receive the PPDU carrying the ITS / RCS, it may keep monitoring the primary channel or it may set 1640 the NAV and go in a dose mode.

[0167] At step 1645, if the SCA initiator receives the CCS frame successfully, it transmits 1650 one or more BSS PPDUs to the SCA responder then monitors 1655 the anchor channel to receive the ACK, and then switches back to the primary channel. Alternatively, the SCA initiator may switch back to the primary channel and receive the ACK and / or other options as described herein. At step 1645, if the SCA initiator does notreceive the CCS frame successfully, it may switch back 1660 to the primary channel, wait for another CCS, send an RTS soliciting the indication from the SCA responder, or wait until the SCA TXOP is elapsed and then switch back to the primary channel It is noted for this example embodiment, there may be no transmission by the SCA initiator soliciting an indication of channel change by the SCA responder. That is only the ITS / RCS is transmitted and the SCA responder indicates that it has switched to the anchor channel, i.e., two-way handshaking.

[0168] At step 1665, if the SCA responder dos not receive the PPDUs from the SCA initiator, e.g., after xlFS of sending the CCS, the SCA responder my switch back 1670 to the primary channel, send another CCS or wait until the SCA TXOP has elapsed and then switch back to the primary channel Otherwise, after completing the successful reception of one or more BSS PPDUs shown by steps 1665 and 1670, the SCA responder may respond 1680 with an ACK on the anchor channel and switch back to the primary channel, switch back to the primary channel and then respond with the ACK on the primary channel, and / or wait until SCA TXOP is elapsed and switch back to the primary channel.

[0169] Referring to FIG. 17, example methods of channel switching operations with spatial reuse (SR)- based SCA are disclosed. In one embodiment , the SCA initiator may transmit the RCS frame following the same procedure of the OBSS packet detect (PD)-based spatial reuse operation illustrated in diagram 1700. The SCA initiator may measure the received signal strength 0BSS_PDlevei) 1705 of the OBSS PPDU occupying the primary channel. If the (OBSS_PDlevei) 1705 is in the range [0BSS_PDmin, 0BSS_PDmax], the SCA initiator adjusts the transmit power of the PPDU carrying the RCS frame (TX_PWR) 1 10 according to the transmit power adjustment rule for allowable OBSS_PDieveiand TX_PWR 1715 as illustrated in FIG. 17 diagram 1700.

[0170] In one embodiment, the SCA initiator may satisfy all the conditions of OBSS PD spatial reuse (SR) operation before transmitting the RCS frame on the primary channel. The transmission of the RCS frame on the primary channel resembles a spatial reuse transmission but with the exception that it does not include the transmission of data PPDUs on the primary channel by the SCA initiator. In procedure 1700, a primary purpose of following the OBSS packet detection (PD) spatial reuse operation is to send the RCS frame by the SCA initiator to the SCA responder over the primary channel (i.e., during detected OBSS transmission), to initiate switching to an anchor channel. It is noted that FIG. 17 illustrates an example transmit power adjustment in the normal OBSS PD-based spatial reuse operation as defined in 802.11ax, although other similar operations could be utilized.

[0171] Alternatively or additionally, in one embodiment, the SCA initiator may send the RCS frame following the same procedure of the parametrized spatial reuse (PSR)-based spatial reuse operation. The SCA initiator may satisfy all the conditions of PSR spatial reuse operation before transmitting the RCS frame on the primary channel. The transmission of the RCS frame on the primary channel resembles a spatial reuse transmission but with the exception that it does not include the transmission of data PPDUs on the primary channel by theSCA initiator. In this procedure, a primary purpose of following the PSR spatial reuse operation is to send the RCS frame by the SCA initiator to the SCA responder to initiate switching to the anchor channel.

[0172] In one embodiment, the parameters of the OBSS packet detection (PD)-based spatial reuse can be changed to relax the conditions required for the OBSS PD spatial reuse operation. In one example, the OBSS_PDmaxmay be increased allowing the SCA initiator to send the RCS frame even with a higher level of interference on the primary channel.

[0173] In one embodiment, the parameters of the PSR-based spatial reuse can be changed to relax the conditions required for the PSR spatial reuse operation. In one example, the maximum Acceptable Receiver Interefrence LevelAPmay be increased allowing the SCA initiator to send the RCS frame even with a higher level of interference on the primary channel.

[0174] In various embodiments, soft preemption based SCA is utilized with SR type of parameters. In one embodiment, the RCS frame may be transmitted on the primary 20 MHz channel during the transmission of the OBSS. This transmission may interfere with the ongoing transmission on the primary channel in the OBSS. This transmission may follow the spatial reuse operation where there are certain conditions that shall be followed to protect the ongoing OBSS transmission on the primary channel. In another method, this transmission may follow the soft preemption operation as discussed in this section in which no coordination is required with the transmitting STA(s) (AP or non-AP STAs) in the OBSS who occupy the primary channel.

[0175] In one embodiment, soft preemption in the above embodiment refers to transmitting a PPDU during an ongoing transmission without the need to stop the ongoing transmission partially or entirely (which might be referred to as hard preemption). Soft preemption represents a short-term interference to the OBSS and can be used to trigger one or more STAs to switch to the anchor channel.

[0176] In one embodiment, the transmit power of the PPDU containing the RCS frame in the previous embodiments may be calculated to minimize the interference impact on the ongoing transmission in the OBSS while maintaining an adequate level of SINR (Signal-to-lnterference-plus-Noise ratio) for the transmitted PPDU such that the receiving STA can decode the PPDU successfully.

[0177] In one method, the SCA initiator adjusts the transmit power of the PPDU carrying the RCS frame such that the SCA responder can receive the PPDU successfully according to the following equation 1 ::TX_PWR(TX_PWRref — (OBSS_PDtevel- OBSS_PDmax), OBSS_PDtevel- OBSS_PDmax< Threshold(. 0, OBSS_PDlevet— OBSS_PDmax> Threshold(Eq. 1)

[0178] The TX_PWRref and Threshold values may be chosen to compromise increasing the probability of the successful reception of the PPDU carrying the RCS frame and the amount of interference impacting the OBSS transmission.

[0179] It is noted that other parameters of the above equation may be defined in the normal spatial reuse operation of 11 ax and / or 11be (See FIG. 17).

[0180] In one embodiment, as illustrated in FIG 18 diagram 1800, the PPDU carrying the RCS / ITS frame (shown by line 1812 transmitted in BSS 1810 between the SCA initiator 1815 and SCA responder 1830 may interfere with the ongoing transmission 1862 in the OBSS 1850 and may cause interruption to the OBSS PPDU. Also, the OBSS PPDU 1862 may interfere with the PPDU carrying the RCS / ITS frame 1812 causing unsuccessful reception of this frame by the SCA responder 1830. In order to guarantee a successful reception of the RCS frame with a limited impact on the ongoing transmission a set of conditions is desirable. Example of these conditions may include one, or any combination of the following conditions (1 )-(5).

[0181] (1) The OBSS AP 1860 may indicate that soft preemption of its PPDUs is allowed by setting a field(e g. a new field named Soft Preemption Allowed field) in the Beacon frame 1870 or any other management, control, or action frame Additionally, or alternatively, the Soft Preemption Allowed field may be included in the UHR-SIG field or UHR-USIG field of the OBSS PPDUs 1862 The Soft Preemption Allowed field may be set to a value (such as 1) to indicate that soft preemption of the OBSS PPDUs is allowed. The Soft Preemption Allowed field may be set to a value (such as 0) to indicate that soft preemption of the OBSS PPDUs is not allowed.

[0182] (2) Additionally, or alternatively, the OBSS AP may announce soft preemption periods in which the soft preemption of its PPDUs is allowed The soft preemption periods may be indicated in the Beacon frame or may be negotiated using a coordination procedure.

[0183] (3) Additionally, or alternatively, the OBSS may indicate the maximum acceptable interference it can handle in case the Soft Preemption Allowed is set to 1

[0184] (4) The SCA initiator may measure the signal strength of the OBSS PPDU and identify whether thePPDU is uplink or downlink PPDU. The SCA initiator may also measure the signal strength of the OBSS Beacon frame to estimate the relative pathloss to the OBSS AP. The SCA initiator may use these measurements to identify whether the ongoing transmission is transmitted by the OBSS AP or received by the OBSS AP. The SCA initiator may determine based on these measurements the transmit power of the PPDU carrying the RCS frame and may determine whether the interference caused by the transmission of the PPDU carrying he RCS frame is within acceptable limits or not.

[0185] (5) The SCA initiator may transmit the RCS frame using the lowest MCS to increase the probability of successful reception of this frame by SCA responder 1830.

[0186] Referring to FIG 19, an example method 1900 of utilizing OBSS transmission gaps for SCA is shown. In method 1900, a BSS (the OBSS AP 1910 in this scenario) may announce certain periods in the transmission of a PPDU(s) having transmission gaps 1912, which may be left vacant, filled with padding symbol(s), or used to transmit training fields such that the SCA initiator 1950 may transmit the RCS 1955 during these gaps 1912 to initiate the SCA switching procedure as discussed in previous embodiments . These gaps1912 may be announced in the beacon frame, probe request / response frame, (re)association request / response frame, and / or any other management, control, or action frame that may be used to negotiate the availability of OBSS gaps 1912 which may be used by a BSS to send the RCS 1955 and initiate the switching SCA.

[0187] In one method, the OBSS 1910 may indicate that it allows the transmission of short PPDUs from other BSSs during the transmission of its PPDU in these gaps by indicating this in the USIG field or the SIG field.

[0188] The RCS frame 1955 may be transmitted in different ways, in on example, it may be a specialized Null Data Packet (NDP), a MAC frame carried in a UHR PPDU or in a non-UHR PPDU, an existing short MAC frame (e.g. QoS Null frame) carried in a UHR PPDU or in a non-UHR PPDU, or a short new MAC frame carried in a UHR PPDU or in a non-UHR PPDU. In what follows different options of the RCS frame will be discussed.

[0189] In one method, switching to the anchor channel may be initiated by transmitting a special form of the null data packet (NDP) (referred to as a RCS-NDP). The NDP may be carried in a ultra-high reliability (UHR) PPDU or a non-UHR PPDU (e.g., EHT PPDU, HE PPDU, VHT PPDU, HT PPDU, or non-HT PPDU, or non-HT DU P PPDU). In one embodiment, the RCS-NDP may be transmitted by the SCA initiator on the primary channel and all STAs that can receive it successfully may switch to the anchor channel. In this method, the SCA responders are not addressed in the RCS-NDP, the SCA responders are the STAs who can successfully receive the RCS-NDP and switch to the anchor channel

[0190] In one method, the RCS frame may be a trigger frame carried in a UHR PPDU or a non-UHR PPDU addressed to the target SCA responders in which information of the SCA responders are listed. In another example, the RCS frame may be a short frame (e.g., quality of service (QOS) Null, RTS, Null, PS-Poll, etc.) addressed to a group of STAs identified with a group ID. In another example, the RCS frame may be a newly created short medium access control (MAC) frame addressed to a group of STAs identified with a group ID.

[0191] In one embodiment, the SCA initiator may transmit the PPDU carrying the RCS frame using distributed tone resource units (DRUs) such that the interference impact on the OBSS PPDU is minimized The SCA initiator may indicate the type of the PPDU carrying the RCS frame in the UHR-SIG field or the UHR-USIG field.

[0192] UHR PPDU. In one embodiment, the SCA initiator may initiate switching to the anchor channel by transmitting the RCS frame in a UHR PPDU to the SCA responder(s). The U-SIG field of this UHR PPDU may contain a field named Switch to Anchor as illustrated in TABLE 5. The Switch to Anchor field may be set to a value (such as 1) to indicate that the STA(s) addressed in the RCS frame shall switch to the anchor channel.U-SIGSymbol 1TABLE 5: Exemplary Illustration of the UHR U-SIG field

[0193] In another method, the Switch To Anchor field may be included in the common field of the UHR-SIG field as shown in TABLE 5.

[0194] In one embodiment, the SCA responder may not be able to decode the RCS frame addressed to itself correctly but the preamble of the PPDU carrying the RCS frame may be decoded successfully and the SCA responder may be able to learn the Switch To Anchor field indication. In this scenario, the SCA responder may switch to the anchor channel waiting for RTS, MU-RTS, or a trigger frame addressed to itself on the anchor channel. The SCA responder may switch back to the primary channel if it does not receive an RTS, MU-RTS, or a trigger frame addressed to itself on the anchor channel.

[0195] In one embodiment, the UHR U-SIG field, the UHR-SIG, or any other signaling field may comprise a field (may be named Anchor Channel Index). The Anchor Channel Index may indicate the specific index of the anchor channel that will be used in the switching to secondary phase. The list of available secondary channels to be used in this phase may be announced in the beacon frame, probe request / response frame, (re)association request / response frame, and / or any other management, control, or action frame that may be used to negotiate the availability of secondary channels to perform the switching to secondary phase.

[0196] In one embodiment, the indication of which anchor channel may be used to perform the switching procedure may be communicated from the MAC to the PHY through the PHY service interface , e.g., the TXVECTOR.

[0197] In one embodiment, the CCS frame may be a short frame sent by the SCA responder to the SCA initiator on the anchor channel in a UHR PPDU or a non-UHR PPDU to confirm completing the switching operation successfully. In one method, the CCS may be sent on a dedicated resource unit allocated to each SCA responder and indicated in the RCS frame in the User Info field corresponding to each SCA responder. The CCS may be a known frame such as CTS, CTS-To-Self, etc. or a newly defined frame specific to this purpose.

[0198] Examples of operation on the anchor channel are described. In one embodiment, the SCA initiator and the SCA responders may negotiate the requirements for successful operation on the anchor channel. The SCA initiator may exchange parameters indicating the relative switch time needed to switch to the anchor channel to guarantee that the SCA responders may switch relatively at the same time to be able to synchronize on the anchor channel successfully.

[0199] In one embodiment, the SCA initiator may transmit a synchronization frame on the anchor channel to synchronize the SCA responders. The synchronization frame may be a basic trigger frame, buffer status report poll (BSRP) trigger frame, bandwidth query report poll (BQRP) trigger frame, Polling trigger frame, null data packet feedback report poll (NFRP) trigger frame, RTS, multi-user (MU)-RTS, or any other frame.

[0200] Referring to FIG. 20, an example method 2000 of soft preemption for secondary channel access (i.e., using multiple anchors channels is shown. In a dense environment where there are multiple OBSSs or even other technologies simultaneously operating across the unlicensed spectrum, the first secondary channel(or the anchor channel) may still be found busy after making the switch according to the various methods described previously In some scenarios, to meet low latency requirements, the SCA initiator may have the need to make a subsequent switch to a second secondary channel, and if the second secondary channel is still busy, this process may be repeated until a more accessible secondary channel is found or the SCA TXOP on the primary channel has expired.

[0201] The BSS of the SCA initiator / responders may keep a list of multiple potential secondary channels to switch to. The generation of the list could be determined by factors such as the priority of technology users on a given channel, the operating bandwidth capabilities of the AP and STAs, and polling from the AP and STAs based on their past observations of the channel conditions on a secondary channel including but not limited to the interference strength and frequency, the maximum allowed transmit power, and the received signal strength indicator (RSSI) measurement. The secondary channels in the list may be ranked and indexed according to the above factors. In one method, the SCA initiator may pick a random secondary channel from the list to switch to, while in another method, the SCA initiator may make secondary channel switches one channel at a time, according to the ranking and index of the list, till a more accessible secondary channel is found for operation.

[0202] As illustrated in FIG. 20 method 2000 begins in a first BSS channel, e.g , in the primary channel that is occupied by an OBSS1 transmission. The SCA initiator 2010 may initiate the switching to the secondary channel by sending an indication to switch (ITS)Zrequest channel switch (RCS) frame 2012, e.g, in primary channel 2001, which may for example be a UHR PPDU carrying RTS frame, MU-RTS frame or any other frame addressed to one or more SCA responders 2020. The SCA initiator 2010 and the SCA responder(s) 2020 may switch 2014 to a second BSS channel, e.g, a first secondary channel 2002. SCA initiator 2010 may perform a full clear channel assessment (CCA) in the first secondary channel 2002. As previously described, a full CCA may include physical CCA 3026 by listening to the channel and virtual CCA by sending another RTS / MU-RTS on the first secondary channel and waiting for a CTS response from the SCA responder(s). If the SCA responder(s) sends back CCS / CTS responses, the case and the henceforth procedure are already described previously.

[0203] If the SCA initiator 2010 senses the first secondary channel 2002 is also occupied through physical CCA 2016 as is shown in FIG. 20, the SCA initiator 2010 may initiate the switching procedure to a third BSS channel, e.g, a second secondary channel 2003 by sending yet another RCS 2018 to the SCA responder(s) 2020. Then, the SCA initiator and the SCA responder(s) may switch to the second secondary channel 2003. On the other hand, if the SCA initiator senses a clear first secondary channel as illustrated in FIG. 21 , the SCA initiator may have several options depending on if all or some of the SCA responders send back the CTS response in the virtual CCA procedure. In one method, the SCA initiator cannot identify which SCA responders responded with CTS but does know some of them responded, then the SCA initiator 2010 may proceed with transmitting and receiving on the secondary channel as if all SCA responders responded.

[0204] Referring to FIG. 21 , in another method 2100, the SCA initiator can identify which SCA responders responded with CCS / CTS, then the SCA initiator may proceed with transmitting and receiving on the secondarychannel with the subset of the SCA responders that responded with CCS / CTS. In yet another method, the SCA initiator can determine not all the SCA responders sent back CCS / CTS 2125 or none of the SCA responders did, then it immediately sends another RCS frame 2118 to indicate the next channel switching to the second secondary channel as illustrated in FIG. 21. Then the same aforementioned full CCA procedure is performed by both the SCA initiator and responder(s) yet again in the second secondary channel. If CCA is not clear or in some partially clear scenarios as described above, the SCA initiator may initiate yet another switch to a fourth BSS channel, e.g., another secondary channel by repeating the switching procedure as descried above. The switching procedure may stop when the SCA TXOP in the primary channel has expired, or it will continue till an available secondary channel is found regardless of the SCA TXOP duration in the primary channel.

[0205] In one method, the SCA initiator may initiate switching to a secondary channel by transmitting an RCS frame in a UHR PPDU to the SCA responder(s). The U-SIG (or UHR-SIG) field of this UHR PPDU may contain a field named Secondary Channel Information as illustrated in TABLE 6 below. The Secondary Channel Information field may be set to a multiple-bit value to indicate if the STA(s) addressed in the RCS frame shall switch to a secondary channel and if yes which secondary channel to switch to. The Secondary Channel Information field may also contain only a single-bit indicator of staying or switching, for the latter of which all AP and STAs automatically switch to the next secondary channel in the list of potential secondary channels.U-SIGSymbol 1U-SIGSymbol 2TABLE 6: Exemplary Illustration of the UHR U-SIG field for multiple secondary channels

[0206] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magnetooptical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

CLAIMSWhat is Claimed:

1. A method for a station (STA), the method comprising: communicating with a target STA on a first channel of a basic service set (BSS); determining that the first channel is busy due to a first overlapping BSS (OBSS) STA transmission; initiating a change to a second channel of the BSS by sending, to the target STA on the first channel, an indication to switch channels; sending, to the target STA on the second channel, a message soliciting confirmation of channel change; in response to sending the message soliciting confirmation of channel change, receiving from the target STA on the second channel, an indication confirming channel change; sending to, or receiving from, the target STA confirming the channel change, one or more BSS physical layer protocol data units (PPDUs); and switching back to the first channel after a period of time.

2. The method of claim 1 , wherein prior to sending or receiving the one or more BSS PPDUs, the method further comprises: determining the second channel is busy due a second OBSS STA transmission; initiating a change to a third channel of the BSS by sending to the target STA on the second channel, the indication to switch channels; sending, to the target STA on the third channel, the message soliciting confirmation of channel change; and in response to sending the message soliciting confirmation of channel change, receiving from the target STA on the third channel, the indication confirming channel change.

3. The method of claim 2, wherein the first channel is a primary BSS channel, the second channel is a first secondary BSS channel and the third channel is a second secondary BSS channel.

4. The method of any one of claims 1-3, wherein the indication to switch channels comprises a request channel switch (RCS) frame carried in a ultra-high reliability (UHR) PPDU addressed to a plurality of target STAs.

5. The method of any one of claims 1-4, wherein the message soliciting confirmation of channel change comprises one of a request to send (RTS) frame or a trigger frame.

6. The method any one of claims 1-4, wherein the message soliciting confirmation of channel change comprises a polling trigger frame or a null data packet feedback report poll (NFRP).

7. The method of any one of claims 1-6, wherein the indication confirming channel change comprises one of a clear to send (GTS), CTS to self (CTSTS), a null data packet feedback report (NFR) or a channel confirmation switch (CCS) message.

8. The method of any one of claims 1-7, wherein the period of time comprises one of a secondary channel access transmit opportunity (SCA TXOP), a time after the SCA TXOP to send or receive an acknowledgement (ACK) of the one or more BSS PPDUs, or a time shorter than the SCA TXOP to monitor the first channel until the first channel is not busy.

9. The method of any one of claims 1-8, wherein prior to sending the indication to switch channels, the method further comprises: negotiating with the target STA, one or more service periods or availability windows in which the target STA may expect to receive the indication to switch channels.

10. The method of any one of claims 1-8, wherein the STA comprises an access point (AP) and wherein the target STA comprises a non-AP STAs11. A station (STA) comprising: a transceiver; and a processor communicatively coupled to the transceiver, wherein the transceiver and the processor are configured to: communicate with a target STA on a first channel of a basic service set (BSS); determine that the first channel is busy due to a first overlapping BSS (OBSS) STA transmission; initiate a change to a second channel of the BSS by sending, to the target STA on the first channel, an indication to switch channels; send, to the target STA on the second channel, a message soliciting confirmation of channel change; in response to sending the message soliciting confirmation of channel change, receive from the target STA on the second channel, an indication confirming channel change; send to, or receive from, the target STA confirming the channel change, one or more BSS physical layer protocol data units (PPDUs); and switch back to the first channel after a period of time.

12. The STA of claim 11 , wherein prior to sending or receiving the one or more BSS PPDUs, the transceiver and the processor are further configured to: determine the second channel is busy due a second OBSS STA transmission; initiate a change to a third channel of the BSS by sending to the target STA on the second channel, the indication to switch channels;send, to the target STA on the third channel, the message soliciting confirmation of channel change; and in response to sending the message soliciting confirmation of channel change, receive from the target STA on the third channel, the indication confirming channel change.

13. The STA of claim 12, wherein the first channel is a primary BSS channel, the second channel is a first secondary BSS channel and the third channel is a second secondary BSS channel.

14. The STA of any one of claims 11-13, wherein the indication to switch channels comprises a request channel switch (RCS) frame carried in a ultra-high reliability (UHR) PPDU addressed to a plurality of target STAs.

15. The STA of any one of claims 11-14, wherein the message soliciting confirmation of channel change comprises one of a request to send (RTS) frame or a trigger frame.

16. The STA any one of claims 11-14, wherein the message soliciting confirmation of channel change comprises a polling trigger frame or a null data packet feedback report poll (NFRP).

17. The STA of any one of claims 11-16, wherein the indication confirming channel change comprises one of a clear to send (GTS), CTS to self (CTSTS), a null data packet feedback report (NFR) or a channel confirmation switch (CCS) message.

18. The STA of any one of claims 11-17, wherein the period of time comprises one of a secondary channel access transmit opportunity (SCA TXOP), a time after the SCA TXOP to send or receive an acknowledgement (ACK) of the one or more BSS PPDUs, or a time shorter than the SCA TXOP to monitor the first channel until the first channel is not busy.

19. The STA of any one of claims 11-18, wherein prior to sending the indication to switch channels, the transceiver and the processor are further configured to: negotiate with the target STA, one or more service periods or availability windows in which the target STA may expect to receive the indication to switch channels.

20. The STA of any one of claims 11-19, wherein the STA comprises an access point (AP) and wherein the target STA comprises a non-AP STA.

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