Patent Description:
Advances in self-interference cancellation have led to the feasibility of full-duplex wireless (FDW) communications at the physical layer. However, conventional carrier sense mechanisms may not allow multiple stations (ST As) to access a contention based wireless medium simultaneously. For example, carrier sensing in the uplink/downlink will detect energy in the channel when a STA is transmitting in the downlink/uplink, which will prevent the system from full-duplex operation. Thus, channel access schemes that enable multiple STAs to access the medium with full- duplex radios are needed. <NPL> discloses self-interference cancellation related techniques in-band full-duplex (FD) transmission in which a wireless node can simultaneously transmit and receive in the same frequency band and highlights immediate challenges (both in the PHY and MAC layers) that need to be addressed in designing FD wireless systems. A qualitative comparison among the existing full-duplex MAC (FD-MAC) protocols is then provided. Finally, the primary requirements and research issues for the design of FD-MAC protocols are discussed, and implications of FD technology in cellular wireless networks are highlighted. <CIT> discloses a full-duplex communication method in a WLAN system. The method includes: obtaining, by an access point AP, use permission of a channel; determining, by the AP after obtaining the use permission of the channel, scheduling information for a station STA participating in full-duplex transmission, where the scheduling information includes information about a first station that performs uplink transmission on the channel and information about a second station that performs downlink transmission on the channel at the same time, or the scheduling information includes information about a third station that simultaneously performs uplink and downlink transmission on the channel; and sending, by the AP, a trigger frame, where the trigger frame includes the scheduling information.

Methods and apparatuses are described herein for multiple access schemes for Wireless Local Area Networks (WLANs) with full-duplex radios. According to the invention, there is provided a method for use in a full-duplex, FD, compatible access point, AP as defined by claim <NUM>, a full-duplex, FD, compatible access point, AP as defined by claim <NUM>, and another full-duplex, FD, compatible access point, AP as defined by claim <NUM>.

<FIG> is a diagram illustrating an example communications system <NUM> in which one or more disclosed embodiments are implemented.

The WTRU <NUM> includes 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 downlink (e.g., for reception) may be concurrent and/or simultaneous. The full-duplex radio may include an interference management unit <NUM> 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 <NUM>).

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. 11e DLS or an <NUM>.

The CN <NUM> shown in <FIG> 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.

In view of <FIG>, and the corresponding description of <FIG>, 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 <NUM>, SGW <NUM>, PGW <NUM>, gNB 180a-c, AMF 182a-ab, 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).

In some circumstances, wireless communications systems may be restricted to transmissions for the downlink and associated receptions in the uplink, or visa-versa, using any combination of time/frequency/space/polarization dimensions to separate the downlink/uplink transmissions. This restriction may be imposed by the capability of radio technology, which due to limitations in isolation capabilities may necessitate that a radio on a particular frequency and band can only either transmit or receive at a particular time instant. To address this issue, Frequency Division Duplex (FDD), or Time Division Duplex (TDD) transmissions schemes wherein separation of transmitted and received signals may be used to by using either frequency or time based separation.

<FIG> illustrates an example full-duplex transceiver or full-duplex wireless system (FWS) <NUM>, which may be used in combination with any of other embodiments described herein. As self-interference cancellation techniques advance, full-duplex at the physical layer feasibility may be seen. The example of <FIG> provides an overview of a typical FDW system <NUM>, and the corresponding aspects which may enable such systems. As illustrated in <FIG>, a FDW system <NUM> may comprise three functions: <NUM>) antenna isolation, <NUM>) analog cancellation, and <NUM>) digital cancellation. Each of these areas may provide a specific degree of transmission and reception isolation/cancellation, and each may do so with a unique set of design constraints and limitations. Using transmit and/or receive antennas <NUM>, antenna isolation methods may provide <NUM> to <NUM> dB of isolation between the transmit and receive signal paths. Analog cancellation may provide an additional <NUM> to <NUM> dB of isolation. For example, the analog cancellation circuit <NUM> may perform fixed delays <NUM> and programmable attenuation <NUM> on the analog signals to provide such isolation. Digital cancellation may provide another <NUM> to <NUM> dB of isolation. For example, the baseboard <NUM> may include a digital analog circuit <NUM> and an analog digital circuit <NUM>, and performs digital cancellation <NUM> to provide such isolation. Using the combination of these methods a FDW system may provide up to <NUM> dB of isolation between the transmit and receive signal paths, which may be the minimum necessary for a practical FDW system.

The first step to facilitate full-duplex transmission, or simultaneous transmission and reception, may be antenna isolation of the transmit and receive antennas <NUM>. Isolation may be accomplished using a number of different approaches including physical alignment, location, phase cancellation, and/or isolation using a circulator. Using methods such as these for antenna isolation, isolation results of approximately <NUM> dB may be accomplished.

Analog cancellation circuit <NUM> may address interference from the transmit path to the receive path through the use of a cancellation signal that is applied to the receive signal. Several methods for analog cancellation may be used, such as: use of a balun for coupling of a portion of the transmit signal, and inverted prior to cancellation in the receive path; use of an analog cancellation circuit to actively adjust the cancellation signal; and/or use of a branch line coupler to facilitate analog cancellation.

Digital cancellation <NUM> may be used to remove residual interference from the antenna isolation and RF cancellation stages of the transceiver. As discussed herein, digital cancellation <NUM> may provide <NUM> to <NUM> dB of isolation; however, this may not be sufficient without other elements of signal cancellation. Issues with achieving a higher degree of digital cancellation may be the result of quantization limitations for broadband digital converter technologies.

Digital cancellation <NUM> may have two components: estimating the self-interference of the received waveform; and using the channel estimate on the known transmit signal (e.g., derived from the preamble or full-duplex preamble) to generate digital reference samples for subtraction from the received signal. Given these components, the quality of digital cancellation may depend on the quality of channel estimation. If an FDW system is implemented in a WLAN system, channel estimation may be prone to interference due to STAs that cause interference during the training period of the reception. One approach to specifically use an interference-free period for channel estimation via carrier sense.

There may be more than one MAC design to support full-duplex operation in WLAN networks. For example, there may be pair-wise (symmetric) full-duplex and asymmetric full-duplex.

<FIG> illustrates a pair-wise (symmetric) type of full-duplex operation scenario. As shown in the pair-wise full-duplex scenario there may be two nodes involved in full-duplex operation. Both nodes (AP <NUM> and STA A) may be full-duplex capable and may transmit and receive at the same time.

<FIG> illustrates an asymmetric type of full-duplex operation scenario. In the asymmetric full-duplex scenario there may be three nodes involved in the full-duplex operation. Only node AP <NUM> may be required to be full-duplex capable since it may be the only node that is transmitting and receiving at the same time in this scenario; the other two nodes (STAs A and B) may be only half-duplex capable.

With either type of full-duplex operation scenarios, the first transmission in the full-duplex operation may be defined as the primary transmission, and the corresponding transmitter and receiver may be defined as the primary transmitter and receiver. The second transmission may be defined as the secondary transmission of the full-duplex operation, and the corresponding transmitter and receiver may be defined as the secondary transmitter and receiver. The uplink transmission may be either the primary or the secondary transmission (and vice versa).

The MAC design for full-duplex operation may include a number of parameters and specifications. In one example, the parameters and specifications may include one or more of the following: CSMA/CA-based algorithm(s); support for pair-wise and unrestricted STR scenarios; a requirement of modifying the current ACK by specifying the order of sending ACKs after full-duplex transmission; an additional feature of determining the destination of secondary transmission based on a history interfering table; an additional feature of a primary collision mechanism where secondary transmission is used as an implicit ACK; a requirement for all nodes to be STR-aware; and/or an inability to support legacy <NUM> devices.

In another example, the parameters and specifications may include one or more of the following: a focus on pair-wise STR-scenario; a requirement of modifying the current ACK by modifying the priority of sending ACKs to be a higher than waiting for ACKs; a requirement for modifying an overhearing behavior, where after one successful full-duplex transmission, every node waits for Extended Interframe Space (EIFS) to start next contention; an additional feature of pair-wise secondary transmission, where the initiation of the secondary transmission is embedded in RTS-CTS exchange; compatibility with <NUM> devices with higher contention overhead (EIFS).

In another example, the parameters and specifications may include one or more of the following: an AP-centralized algorithm(s); support for pair-wise and unrestricted scenarios; a requirement of a new centralized medium access mechanism; a requirement that all nodes be STR-aware; and/or an inability to support legacy <NUM> devices. The new centralized medium access mechanism may further include the parameters that the AP controls and is operated in a <NUM>-step cycle, the AP collects information about data-length and interference relationships from STAs, the AP broadcasts the scheduling decision packet and initiates data transmissions, and/or the sending of ACKs in the predefined order embedded in the scheduling decision packet.

In order to utilize spectrum more efficiently, in-band full-duplex may be considered for <NUM> (e.g., <NUM>. 11ax HEW SG). Specifically, a high level design for an in-band full-duplex MAC may include the addition of an STR preamble. The STR preamble to support in-band full-duplex may further include: partial association ID (AID) in the VHT-SIGA1 that indicates a recipient(s) of a PPDU; group ID / partial AID of STA2 that indicates the STA2 should also transmit; STA2 should end PPDU transmission before L_LENGTH duration; in-band STR capable AP that can transmit and receive ACK simultaneously; and/or where STA feedbacks the status of a transmit buffer at STAs to the AP to enable scheduling of UL transmission.

In a conventional Carrier-Sense Multiple-Access with Collision Avoidance (CSMA/CA) based channel access methodology, channel access may not work well for full-duplex operation. Given that full-duplex requires that multiple STAs access the medium simultaneously, a legacy carrier sense mechanism in the uplink, or downlink, may detect energy in the channel when the downlink, or uplink, is transmitting. Therefore, a new channel access mechanism is needed to address this issue.

<FIG> illustrates an example of a channel access issue <NUM> for full-duplex operation. As shown in the example, AP <NUM><NUM> may start transmission to STA C 502c (which is the primary transmission). Then, STAs A 502a and B 502b may both detect this primary transmission and may decide to take advantage of full-duplex operation and subsequently may desire to start a secondary transmission to AP <NUM><NUM>. However, due to the on-going primary transmission (AP <NUM><NUM> to STA C 502c) on the same channel, the conventional CSMA/CA mechanisms may not work as STA C 502c occupies the medium and consequently, when STAs A 502a and B 502b perform listen before talk, they will sense the medium is busy. Additionally, STAs A 502a and B 502b cannot know if other STAs have attempted a secondary transmission to AP <NUM><NUM> as well.

In order to enable full-duplex operation in WLAN, methods and apparatuses that allow the configuration of full-duplex transmission that avoids the potential for unresolved contention of secondary transmission attempts are needed. In addition, or alternatively, methods and apparatuses for the channel access mechanism to resolve the contention of secondary transmission attempts is needed.

Also shown in the example of <FIG>, STA A 502a may start an uplink transmission to AP <NUM><NUM> (which is the primary transmission). If AP <NUM><NUM> desires to transmit a downlink transmission to STA C 502c using full-duplex (the secondary transmission), AP <NUM><NUM> may be unable to use conventional CSMA/CA to evaluate the medium and also to find out if STA C 502c is able to receive data. A mechanism is needed to enable the AP <NUM><NUM> to opportunistically transmit data to STA C 502c in the downlink when it receives data from STA A 502a in the uplink.

Also shown in the example of <FIG>, AP <NUM><NUM> may decide to start a full-duplex with a transmission from STA A 502a and a transmission to STA C 502c that commences at the same time. In this case, both the uplink and downlink may be classified as primary. A mechanism is needed to (a) identify that STA A 502a has data to send in the uplink, (b) identify that STA C 502c is ready to receive in the downlink and (c) identify when the synchronized full-duplex transmission takes place.

<FIG> illustrates an example of a contention fairness issue <NUM> for full-duplex operation. A conventional back-off scheme may not work well for full-duplex operation for unintended STAs that can receive both the primary and secondary transmissions. For example, a simple pair-wise full-duplex operation scenario may have the following issues: STA <NUM>602b can receive from both AP <NUM><NUM> and STA <NUM>602a; STA <NUM>602a receives packet A successfully and AP <NUM><NUM> receives packet B successfully, but STA <NUM>602b receives a corrupted packet (overlapped version of packets A and B); and/or AP <NUM><NUM> and STA <NUM>602a back off after Distributed Coordination Function Interframe Spacing (DIFS) but STA <NUM>602b back offs after Extended Interframe Space (EIFS), which is may be unfair for STA <NUM>602b. This means that STAs (i.e. STA1 602a and AP <NUM><NUM>) can hear only one STA or one AP may have advantage to other STAs (i.e. STA <NUM>602b) that can hear multiple STAs in terms of decoding packets. It is because if a STA can hear only one and decode the received packets, the STA may back off after DIFS duration. However, if a STA can hear multiple STAs but cannot decode the received packets, the STA may back off after EIFS duration. In order to overcome the aforementioned contention fairness issues and support efficient full-duplex operation in WLAN, it may be desirable to design a channel access mechanism after full-duplex transmission to allow unintended STA of the full-duplex transmission to access the channel in a fair manner.

To enable analog and digital cancellation, it may be necessary for a full-duplex STA to be able to estimate the self-interference of its transmitter in the absence of interference from any additional STAs. Methods are needed to ensure that there is no external interference from other STAs and that there is a way that the STA may be able to transmit a suitable estimation sequence to able to estimate the self-interference and design the cancellation circuits (e.g. analog and digital cancellation circuits).

In one embodiment, a full-duplex frame structure and preamble may be implemented. <FIG> illustrate examples frame structures <NUM> for full-duplex training, which may be used in combination with any of other embodiments described herein. To enable the design and estimation of full-duplex filters, equalizers, or cancellation circuits for self-interference cancellation, it may be necessary that a full-duplex STA/AP acquire the medium to prevent external interference and then transmit a full-duplex training sequence. The full-duplex training sequence for example, may take one or more forms.

For example, <FIG> illustrates an example frame structure <NUM> for full-duplex training as a standalone frame, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, the frame <NUM> may include a legacy frame <NUM> and an FD preamble <NUM>. The legacy frame <NUM> may include, for example, a short training field that includes one training sequence and a long training field that includes the other training sequence. The FD preamble <NUM> may include one or more training sequences and FD parameters. The one or more training sequences may include, but are not limited to, a time domain sequence for the analog domain and a frequency domain sequence for the digital domain. The one or more training sequences included in the FD preamble <NUM> may be referred to as a FD training sequence. As illustrated in <FIG>, shows that the training sequence may be a standalone frame where the frame may be comprised of a legacy preamble then a full-duplex preamble.

In another example, (b) of <FIG> shows a second preamble (full-duplex preamble) sent after the legacy preamble but before the data transmission. This frame may be comprised of a legacy preamble, a full-duplex preamble, and data. The presence or absence of the full-duplex preamble may be signaled in the legacy preamble, such as the SIG field. In another example, (c) of <FIG> shows a mid-amble sequence that may be transmitted at desired intervals within the transmitted frame. This frame may be comprised of a legacy preamble, a full-duplex preamble, and multiple full-duplex mid-ambles to enable the dynamic modification of the parameters of the full-duplex filters/equalizers. In another example, (d) of <FIG> shows a control trailer.

In one solution, a single full-duplex training sequence may be used to design both analog and digital cancellation circuits. Alternatively, separate full-duplex training sequences may be used to design each analog and digital cancellation circuit. As such, the full-duplex STA (or AP) may choose to transmit the analog training sequence, the digital training sequence, or both. This may be especially important since the analog cancellation may be performed by multiple methods that may not need explicit training.

<FIG> illustrates an example full-duplex preamble. The full-duplex preamble may be a fixed number of symbols or may have the number of symbols configurable. In one case, the number of symbols to be used may be configured prior to transmission or may be signaled in a PHY domain field (e.g., the preamble or SIG field). As shown in <FIG>, there may be several fields any appropriate order.

There may be a full-duplex Preamble Parameters field that signals information about whether the full-duplex preamble is analog only, digital only or both. It may also signal the size or duration of the analog and digital preamble fields. It may signal the specific digital domain numerology to be used (e.g. <NUM> subcarriers per <NUM> for <NUM>. 11a, <NUM>. 11n, and <NUM>. 11ac; <NUM> subcarriers per <NUM> for <NUM>.

There may be a full-duplex Time Domain Preamble field that may be used for the full-duplex analog filter design. There may be a full-duplex Frequency Domain Preamble field that may be used for the full-duplex digital filter design. There may be a full-duplex Parameter field <NUM> may be used for parameters for the full-duplex transmission. This full-duplex parameters field <NUM> may include, but are not limited to, information on the start time of the full-duplex transmission, and the specific STAs to transmit.

The STA or AP performing the full-duplex filter design may use the full-duplex preamble parameters <NUM> to identify the duration of the training sequences for the analog filter and the digital filter. The STA or AP may then communicate information to other STAs or APs on the parameters necessary to start the full-duplex transmission.

The transmit and receive address of this frame may be addressed to the full-duplex capable STA (e.g., the AP in the asymmetric full-duplex architecture).

To prevent any external interference, the full-duplex preamble <NUM> may be transmitted in scenarios when the full-duplex AP/STA have acquired the channel.

In one embodiment, there may be channel access procedures for addressing asymmetric full-duplex scenarios. In this embodiment, the STA may have half-duplex capability, but the AP may have full-duplex capability. Further, in one example, a procedure for channel access may be AP controlled (i.e. the AP determines when data to and from STAs may be expected to be transmitted).

<FIG> illustrates an example overall procedure <NUM> for synchronized full-duplex transmission, which may be used in combination with any of other embodiments described herein. The example overall procedure <NUM> may address asymmetric full-duplex scenarios. In this example, an AP <NUM> may have full-duplex capability and STAs 902a, 902b, 902c may have half-duplex capability. To enable full-duplex transmission controlled by the AP <NUM> to occur at synchronized, predetermined times, the AP <NUM> may transmit a full-duplex trigger frame <NUM> or a full-duplex scheduling frame such as a full-duplex CTS. The full-duplex trigger frame <NUM> and/or the full-duplex scheduling frame may indicate: (<NUM>) STA(s) to which the AP <NUM> is transmitting in the downlink (e.g., STA C 902c); and (<NUM>) STA(s) from which it expects to receive in the uplink (e.g., STA A 902a). After STA A 902a and STA C 902c receive the full-duplex trigger frame <NUM> (or the full-duplex scheduling frame), STA A 902a and the AP <NUM> may initiate the full-duplex transmissions (e.g., downlink data transmission <NUM> and uplink data transmission <NUM>) at the same time. For example, the downlink transmission <NUM> from the AP <NUM> to STA C 902c may commence at a fixed duration (e.g. SIFS, PIFS, EIFS) after the full-duplex trigger frame <NUM> or full-duplex scheduling frame is received. Alternatively or additionally, the commencement of the downlink transmission <NUM> may be configured by the full-duplex trigger frame <NUM> or full-duplex scheduling frame. Similarly, the uplink transmission <NUM> from STA A 902a to the AP <NUM> may commence at a fixed duration (e.g. SIFS, PIFS, EIFS) after the reception of the full-duplex trigger frame <NUM> or full-duplex scheduling frame. Alternatively or additionally, the commencement of the uplink transmission <NUM> may be configured by the full-duplex trigger frame <NUM> or full-duplex scheduling frame. The full-duplex trigger frame is a trigger frame dedicated to triggering the full-duplex transmission. The full-duplex trigger frame may include one or more fields, parameters, or information to enable the full-duplex transmission. The full-duplex scheduling frame is a frame that includes or is aggregated with one or more full-duplex scheduling elements/subframes. The one or more full-duplex scheduling elements/subframes may include parameters that are needed for the full-duplex transmission.

As illustrated in <FIG>, if the packet size of the UL data transmission <NUM> is less than the packet size of the DL data transmission <NUM>, STA A 902a may add pad information <NUM> to the UL data to make the duration of full-duplex transmission the same. Although it is not illustrated in <FIG>, if the packet size of the DL data transmission <NUM> is less than the packet size of the UL data transmission <NUM>, the AP <NUM> may append pad information to the DL data to make the duration of the full-duplex transmission the same. After the AP <NUM> successfully receives the UL data from STA A 902a (i.e. the UL transmission <NUM>), the AP <NUM> may respond a DL full-duplex acknowledgement <NUM> to STA A 902a. Similarly, after the STA C 902c successfully receives the DL data from the AP <NUM> (i.e. the DL transmission <NUM>), STA c 902c may respond a UL full-duplex acknowledgement <NUM> to the AP <NUM>.

<FIG> illustrates an example STA procedure <NUM> for synchronized full-duplex transmission, which may be used in combination with any of other embodiments described herein. A procedure to enable synchronized full-duplex transmission may include first identifying STAs (e.g., STA A, STA B, and STA C) as full-duplex compatible. This may mean that a DL transmission to STA C will not be interfered with by an UL transmission from STA A or STA B. Then, STA A or STA B may be identified as having data to transmit to the AP.

The full-duplex transmission may be initiated by using a full-duplex preamble (i.e., to estimate the full-duplex filters), full-duplex trigger, or full-duplex scheduling frame (i.e., to schedule the STAs for full-duplex transmission). The full-duplex trigger, for example, may be a separate frame, may be combined with the downlink data, or may be combined with the frames identifying that there may be traffic to send (e.g., the CTS). After the transmission, a full-duplex ACK may be sent to enable both STAs to acknowledge receipt of the information.

In an embodiment, there may be a procedure for the AP to identify full-duplex stations with information to send in the uplink. The AP may receive an RTS frame from a STA A and send a frame (e.g., a full-duplex RTS/CTS frame) or a series of frames (e.g., a CTS {e.g., a full-duplex CTS frame} to STA A and a RTS {e.g., a full-duplex RTS frame} to STA C) to STA A and STA C indicating that it will be scheduling STA A and STA C for a full-duplex uplink transmission.

In one example, a two-hop RTS-CTS scheme may be used to identify the STAs to transmit. The full-duplex RTS and full-duplex CTS frames may be sent in a manner that ensures the medium is reserved and in a manner where the STAs that will be transmitting in the full-duplex transmission indicate that the medium is available for them to transmit. The full-duplex RTS and full-duplex CTS frames may be specific types of RTS and CTS frames, respectively.

The full-duplex CTS frame sent by the AP to STA A may be transmitted jointly with a full-duplex RTS frame to another STA B, for example as a full-duplex RTS/CTS frame indicating that the AP wants to find out if a second STA B is available to receive information while STA A is transmitting.

In one example, a single frame that contains information needed for both the full-duplex RTS and full-duplex CTS may be used (e.g. full-duplex RTS/CTS frame). In another example, the full-duplex RTS/CTS frame may be comprised of individual (full-duplex) RTS and (full-duplex) CTS frames aggregated together. In another example, the full-duplex RTS/CTS frame may indicate the time that STA A should initiate transmission either based on a full-duplex trigger or based on a pre-configured time duration from when the full-duplex CTS is received. In another example, a full-duplex training sequence may be appended to the full-duplex CTS/RTS frame to enable estimation of the full-duplex filters.

The RTS (e.g., full-duplex RTS) sent by the AP to another STA C may be transmitted a fixed duration (e.g., a SIFS or an EIFS) after the CTS (e.g., full-duplex CTS) response to STA A, indicating that the AP wants to find out if a second STA C is available to receive information while at the same time indicating that it is available to receive information from STA A. In one example, a full-duplex CTS may be sent to STA A indicating the time at which STA A may commence transmitting. The AP may then send an RTS frame to STA C (and any other frames needed to set up the full-duplex transmission). On receipt of the full-duplex CTS from the AP, the STA C may respond with a CTS to the AP.

The AP may use an NDP Feedback Report Poll Trigger to solicit NDP feedback reports from multiple STAs in which the STAs indicate any resource requests. The NDP Feedback Report Poll Trigger may include a list of eligible STAs based on the STAs that have data to be transmitted in the downlink. This may ensure that all the STAs are full-duplex compatible. The list may be explicit (e.g., the STA IDs of the eligible STAs are listed). Alternatively, the list may be implicit. In one example, the STA IDs of the STAs to be transmitted to in the DL are listed. A previous mapping may have identified the STAs that are allowed based on a full-duplex downlink transmission to a specific STA. In another example, a group ID may be used to identify the list of eligible STAs.

On identifying STAs with both uplink and downlink data, the AP may initiate full-duplex transmission.

There may be a procedure for AP synchronized asymmetric full-duplex transmission comprising of one or more phases. The phases may occur in any order. One phase may relate to full-duplex STA compatibility, where groups of STAS are identified as full-duplex compatible (i.e., as groups that can simultaneously transmit and receive from the AP).

In another phase, the full-duplex filter may be setup, where the AP may transmit a full-duplex training sequence to setup the full-duplex filters. The full-duplex training sequence may be transmitted as a separate full-duplex preamble. The full-duplex sequence may be transmitted as a full-duplex mid-amble, in which case the periodicity of the mid-amble may need to be signaled (e.g., in the full-duplex trigger so that the STA in the full-duplex uplink transmission may insert quiet periods in which it does not transmit). The transmission of the full-duplex preamble or mid-amble may be optional based on a PHY layer signal (e.g., a full-duplex signal where the full-duplex filters are already set).

In another phase, there may be FA STA identification where specific STAs may be identified for the full-duplex transmission using a full-duplex trigger or A-control frame.

In another phase, there may be full-duplex transmission which includes sending/receiving the full-duplex data. In another phase, there may be a full-duplex ACK, which includes sending DL and uplink ACKs. If the STAs are not full-duplex capable, a delayed block ACK mechanism may be used to ensure that the packets do not collide.

In one example, on receipt of the CTS from STA A, the AP may transmit a full-duplex frame to STA A. In another example, the full-duplex frame may contain a full-duplex preamble, full-duplex trigger, and data to STA A. The STA B may receive the full-duplex trigger and then start transmission at the appropriate time.

In one example, the full-duplex frame may include the full-duplex trigger and data with the full-duplex training sequence concatenated as a Controller Trailer (CT) to the CTS/RTS frame.

In one example, on receipt of the CTS, the AP may transmit the full-duplex trigger frame as a separate stand-alone frame. The STAs then transmit/receive at the appropriate time.

<FIG> illustrates an example process <NUM> for synchronized asymmetric full-duplex channel access where a full-duplex trigger is a standalone frame, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, the example process <NUM> may comprise channel access setup procedure and channel access procedure. During the channel access setup procedure, an AP <NUM> may identify whether: (<NUM>) STAs 1102a, 1102c are full-duplex compatible; and (<NUM>) STAs 1102a, 1102c have data to transmit/receive to/from the AP <NUM>. The AP may also train its full-duplex transceiver (or FD filter) using FD preamble <NUM>, but this may occur any stage of the example process <NUM> and is not limited to the channel access procedure. During the channel access procedure, the AP <NUM> may initiate FD transmission using a FD trigger frame or FD scheduling frame and transmit/receive acknowledgement signals to/from STAs 1102a, 1102c.

For example, the AP <NUM> may receive an RTS frame <NUM> from STA A 1102a. Based on the RTS frame <NUM>, the AP <NUM> may find that STA A 1102a has data to send and STA A 1102a is full-duplex compatible. The AP <NUM> may determine whether the AP <NUM> may transmit data to STA C 1102c at the same time while the AP <NUM> receives data from STA A 1102a. The AP <NUM> may transmit an FD CTS/RTS frame <NUM> to STA A 1102a and STA C 1102c to indicate that the AP <NUM> will schedule the full-duplex transmissions. The FD CTS/RTS frame <NUM> may be one frame comprising an FD CTS and FD RTS, or separated frames such as an FD CTS and FD RTS. The FD RTS may be directed to STA A 1102a to indicate that the AP <NUM> will schedule the full-duplex uplink transmission. The FD CTS may be directed to STA C 1102c to find whether STA C 1102c has data to send or receive. The FD CTS/RTS frame <NUM> may enable the AP <NUM> to send the FD CTS while requesting a CTS <NUM> from STA C 1102c. It is assumed that the AP <NUM> sets up its FD filter by sending an FD preamble <NUM> to the AP <NUM> itself. The FD preamble <NUM> may include all the training information to enable the AP <NUM> to perform the FD filter estimation. Once the AP <NUM> receives a CTS <NUM> from STA C 1102c, the AP may recognize that: (<NUM>) STA C 1102c can receive data from the AP <NUM>; and (<NUM>) STA C is FD compatible. The AP <NUM> may also recognize by this point that: (<NUM>) STA A 1102a has data to send; and (<NUM>) STA A 1102a is FD compatible.

The AP <NUM> may then send an FD trigger frame <NUM> to STA A 1102a and STA C 1102c to enable the synchronized start for UL data transmission <NUM> (i.e. STA A 1102a to AP <NUM>) and the DL data transmission <NUM> (i.e. AP <NUM> to STA C 1102c). The FD trigger frame <NUM> may indicate the STAs 1102a, 1102c that: (<NUM>) the AP <NUM> is expected to receive data from STA A 1102a at time t; and (<NUM>) the AP <NUM> is expected to transmit data to STA C 1102c at time t. The FD trigger frame <NUM> may include, but are not limited to, time and channel information for the FD transmissions from STA A 1102a and to STA C 1102c. For example, the time information may indicate STA A 1102a when to initiate the UL data transmission <NUM> to the AP <NUM> and when to end the UL data transmission <NUM>. The time information may also indicate STA C 1102c when to initiate the DL data transmission <NUM> from the AP <NUM> and when to end the DL data transmission <NUM>. The time information may include duration for the UL and DL transmissions (i.e. FD transmissions) <NUM>, <NUM>. The channel information may indicate which channel STA A 1102a and STA C 1102c may use for the FD transmissions. The FD trigger frame <NUM> may also include data packet size, MCS to be used by the STAs 1102a, 1102c or any parameters to be used for the FD transmissions.

After receiving the FD trigger frame <NUM>, STA A 1102a may initiate the UL data transmission <NUM> to the AP <NUM> at the time indicated in the FD trigger frame <NUM> (e.g., at time t). The AP <NUM> may initiate the DL data transmission <NUM> to STA C 1102c and STA C 1102c may receive the DL data <NUM> from the AP <NUM> at the time indicated in the FD trigger frame <NUM> (e.g., at time t). It is noted that the FD transmissions <NUM>, <NUM> may be an AP initiated transmissions based on STA A 1102a request. If the packet size of the UL data <NUM> is less than the packet size of the DL data <NUM>, STA A 1102a may append pad information bits <NUM> to the UL data <NUM> to make the duration of the UL data transmission <NUM> the same as the duration of the DL data transmission <NUM>. Although it is not illustrated in <FIG>, if the packet size of the DL data <NUM> is less than the packet size of the UL data <NUM>, the AP <NUM> may append pad information bits to the DL data <NUM> to make the duration of the DL data transmission <NUM> the same as the duration of the UL data transmission <NUM>.

Once the AP <NUM> successfully received the UL data <NUM> from STA A 1102a, the AP <NUM> may transmit a DL ACK signal <NUM> to STA A 1102a to indicate the successful completion of the UL data <NUM>. Once STA C 1102c successfully received the transmission of DL data <NUM> from the AP <NUM>, STA C 1102c may transmit an UL ACK signal <NUM> to the AP <NUM> to indicate the successful completion of the DL data <NUM>.

<FIG> illustrates another example process <NUM> for synchronized asymmetric full-duplex channel access where a full-duplex trigger is a standalone frame, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, the AP <NUM> may receive an RTS frame <NUM> from STA B 1202b. Based on the RTS frame <NUM>, the AP <NUM> may find that STA B 1202b has data to send and STA B 1202b is full-duplex compatible. The AP <NUM> may determine whether the AP <NUM> can transmit data to STA A 1202a at the same time while the AP <NUM> receives data from STA B 1202b. The AP <NUM> may transmit an FD CTS/RTS frame <NUM> to STA A 1202a and STA B 1202b to indicate that the AP <NUM> will schedule the full-duplex transmissions. The FD CTS/RTS frame <NUM> may be one frame comprising an FD CTS and FD RTS, or separated frames such as an FD CTS and FD RTS. The FD CTS may be directed to STA B 1202b to indicate that the AP <NUM> will schedule the full-duplex uplink transmission <NUM>. The FD RTS may be directed to STA A 1202a to find whether STA A 1202a has data to send or receive. The FD CTS/RTS frame <NUM> may enable the AP <NUM> to send the FD CTS while requesting a CTS <NUM> from STA A 1202a. It is assumed that the AP <NUM> sets up its FD filter by sending an FD preamble <NUM> to the AP <NUM> itself. The FD preamble <NUM> may include all the training information to enable the AP <NUM> to perform the FD filter estimation. Once the AP <NUM> receives a CTS <NUM> from STA A 1202a, the AP may recognize that: (<NUM>) STA A 1202a can receive data from the AP <NUM>; and (<NUM>) STA A is FD compatible. The AP <NUM> may also recognize by this point that: (<NUM>) STA B 1202b has data to send; and (<NUM>) STA B 1202b is FD compatible.

The AP <NUM> may then send an FD trigger frame <NUM> to STA A 1202a and STA B 1202b to enable the synchronized start for UL data transmission <NUM> (i.e. STA B 1202b to AP <NUM>) and the DL data transmission <NUM> (i.e. AP <NUM> to STA A 1202a). The FD trigger frame <NUM> may indicate the STAs 1202a, 1202b that: (<NUM>) the AP <NUM> is expected to receive data from STA B 1202b at time t; and (<NUM>) the AP <NUM> is expected to transmit data to STA A 1202a at time t. The FD trigger frame <NUM> may include, but are not limited to, time and channel information for the FD transmissions from STA B 1202b and to STA A 1202a. For example, the time information may indicate STA B 1202b when to initiate the UL data transmission <NUM> to the AP <NUM> and when to end the UL data transmission <NUM>. The time information may also indicate STA A 1202a when to initiate the DL data transmission <NUM> from the AP <NUM> and when to end the DL data transmission <NUM>. The time information may include duration for the UL and DL transmissions (i.e. FD transmissions) <NUM>, <NUM>. The channel information may indicate which channel STA A 1202a and STA B 1202b may use for the FD transmissions. The FD trigger frame <NUM> may also include data packet size, MCS to be used by the STAs 1202a, 1202b or any parameters to be used for the FD transmissions.

After receiving the FD trigger frame <NUM>, STA B 1202b may initiate the UL data transmission <NUM> to the AP <NUM> at the time indicated in the FD trigger frame <NUM> (e.g., at time t). The AP <NUM> may initiate the DL data transmission <NUM> to STA A 1202a and STA A 1202a may receive the DL data <NUM> from the AP <NUM> at the time indicated in the FD trigger frame <NUM> (e.g., at time t). It is noted that the FD transmissions <NUM>, <NUM> may be an AP initiated transmissions based on STA B 1202b request. If the packet size or duration of the UL data <NUM> is less than the packet size of the DL data <NUM>, STA B 1202b may append pad information bits <NUM> to the UL data <NUM> to make the duration of the UL data transmission <NUM> the same as the duration of the DL data transmission <NUM>. Although it is not illustrated in <FIG>, if the packet size of the DL data <NUM> is less than the packet size of the UL data <NUM>, the AP <NUM> may append pad information bits to the DL data <NUM> to make the duration of the DL data transmission <NUM> the same as the duration of the UL data transmission <NUM>.

Once the AP <NUM> successfully received the UL data <NUM> from STA B 1202b, the AP <NUM> may transmit a DL ACK signal <NUM> to STA B 1202b to indicate the successful completion of the UL data <NUM>. Once STA A 1202a successfully received the DL data <NUM> from the AP <NUM>, STA A may transmit an UL ACK signal <NUM> to the AP <NUM> to indicate the successful completion of the DL data <NUM>.

<FIG> illustrates a claimed synchronized full-duplex transmission process <NUM>, which may be used in combination with any of other embodiments described herein. At step <NUM>, an access point (AP) receives an RTS frame from a first STA. At step <NUM>, in response to the received RTS frame, the AP transmits a full-duplex clear to send (FD CTS) to the first STA and a full-duplex request to send (FD RTS) to a second STA. At step <NUM>, the AP transmits an FD preamble to the AP itself to enable the AP to perform its FD filter estimation. At step <NUM>, in response to the transmitted FD RTS, the AP receives a clear to send (CTS) from the second STA. Based on the received RTS, the AP determines that the first STA is expected to transmit the UL data to the AP. Similarly, based on the received CTS, the AP determines that the second STA is expected to receive the DL data from the AP. At step <NUM>, the AP transmits, to both the first STA and the second STA, a full-duplex (FD) trigger frame that includes scheduling information that enables FD communication with the first STA for uplink (UL) data and the second STA for downlink (DL) data at the same time. The scheduling information in the FD trigger frame may include timing information and channel information for the FD communication. The AP may perform the FD communication with the first STA for the UL data and the second STA for the DL data, using the FD filter estimation. The FD trigger fame may be aggregated with at least one of a legacy preamble, a FD preamble, or UL/DL data. Based on the scheduling information, at step <NUM>, the AP may receive the UL data from the first STA while simultaneously transmitting DL data to the second STA. If the packet size of the DL data is less than the packet size of the UL data, the AP may append pad information to the DL data to equalize the packet size of the DL data to the packet size of the UL data. If the packet size of the UL data is less than the packet size of the DL data, the first STA may append pad information to the UL data to equalize the packet size of the UL data to the packet size of the DL data. After the FD communication is completed, the AP may transmit a DL ACK to the first STA at step <NUM> and receive an UL ACK from the second STA at step <NUM>.

<FIG> illustrates an example process <NUM> for synchronized asymmetric full-duplex channel access where a full-duplex preamble and full-duplex trigger are aggregated with downlink data, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, the AP <NUM> may transmit a legacy frame <NUM> before transmitting the FD preamble <NUM> and the FD trigger frame <NUM>. The FD preamble <NUM> and the FD trigger <NUM> may be aggregated with downlink data transmission <NUM> to STA A 1402a to enable synchronized FD transmissions. The contents of the FD preamble <NUM> and the FD trigger <NUM> are similar to or the same as those described in <FIG> and <FIG>. Details of the FD preamble <NUM> and the FD trigger <NUM> are not described for brevity. In addition, the channel access procedure using the RTS <NUM>, FD CTS/RTS <NUM>, and the CTS <NUM>, FD transmissions (i.e. DL data transmission <NUM> and UL data transmission <NUM>), and DL/UL ACK <NUM>, <NUM> are similar to or the same as those described in <FIG> and <FIG>. Details of those are not described for brevity.

<FIG> illustrates an example process <NUM> for synchronized asymmetric full-duplex channel access where a full-duplex trigger is aggregated with downlink data and the full-duplex preamble is separate, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, the AP <NUM> may transmit the FD preamble <NUM> separated from the FD trigger <NUM>. For example, the FD preamble <NUM> may be aggregated with the FD CTS/RTS frame <NUM>. Similar to <FIG>, the FD trigger <NUM> may be aggregated with downlink data transmission <NUM> to STA A 1502a to enable synchronized FD transmissions. The contents of the FD preamble <NUM> and the FD trigger <NUM> are similar to or the same as those described in <FIG> and <FIG>. Details of the FD preamble <NUM> and the FD trigger <NUM> are not described for brevity. In addition, the channel access procedure using the RTS <NUM>, FD CTS/RTS <NUM>, and the CTS <NUM>, FD transmissions (i.e. DL data transmission <NUM> and UL data transmission <NUM>), and DL/UL ACK <NUM>, <NUM> are similar to or the same as those described in <FIG> and <FIG>. Details of those are not described for brevity.

<FIG> illustrates an example process <NUM> for synchronized asymmetric full-duplex channel access with delayed CTS, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, the AP <NUM> may transmit an FD CTS <NUM> and an FD RTS <NUM> separately. Specifically, the AP <NUM> may transmit the FD CTS <NUM> with delay time T to STA C 1602c in response to the RTS <NUM>. The FD CTS <NUM> with delay time T may indicate STA C 1602c that the AP <NUM> will not transmit an FD trigger frame and STA C is allowed to transmit automatically after time T is expired. After time T is passed, STA C 1602c may transmit UL data <NUM> to the AP <NUM> while the AP <NUM> transmits DL data <NUM> to STA A 1602a. Other than the delayed access using the FD CTS <NUM> described above, details of the channel access procedures using the RTS <NUM>, FD CTS <NUM>, FD RTS <NUM>, CTS <NUM>, FD transmissions (i.e. DL data transmission <NUM> and UL data transmission <NUM>), and DL/UL ACK <NUM>, <NUM> are similar to or the same as those described in <FIG> and <FIG>. Details of those are not described for brevity.

In one embodiment, there may be procedures for opportunistic asymmetric full-duplex downlink transmission. In this embodiment there may be an asymmetric full-duplex system in which the STAs may be half-duplex but the AP has full-duplex capability. The procedures may be AP controlled. For example, an AP may respond opportunistically to UL transmission and send a DL full-duplex transmission to compatible STA(s) during the UL transmission. In one example, the AP may detect an incoming packet first and then decide to transmit to a suitable DL STA based on full-duplex compatibility. Alternatively or additionally, the AP may schedule an uplink grant/transmission opportunity (TXOP) for a STA, and when there is an arrival of data for a full-duplex compatible STA, the AP may then allocate a full-duplex DL transmission. In this example, because this is an opportunistic scenario, it may be necessary for the AP to set up full-duplex filters before the receipt of data from the uplink STA to be able to dynamically switch to full-duplex transmission.

<FIG> illustrates an example process <NUM> for opportunistic downlink full-duplex transmission, which may be used in combination with any of other embodiments described herein. Such an example procedure <NUM> may start with an AP <NUM> defining or setting up a full-duplex TXOP <NUM> in which the AP and STAs in the BSS may expect a full-duplex transmission to occur. In one example, a two-hop RTS/CTS procedure may be used. In another example, a Restricted Access Window dedicated to full-duplex transmission may be set up.

The AP may then transmit a full-duplex preamble <NUM> to estimate full-duplex equalizers/filters. The AP may then identify the full-duplex compatible STAs, for example, identify STAs A 1702a, B 1702b and C 1702c as full-duplex compatible. This may mean that an UL transmission from STA A or STA B will not interfere with a DL transmission to STA C. The identification of full-duplex compatibility on the STAs 1702a, 1702b, 1702c may be performed, for example, by RTS/CTS frames as described above.

STA A 1702a may acquire a channel, where the AP <NUM> may know the duration. Upon identifying the UL transmission <NUM>, the AP <NUM> may opportunistically initiate the full-duplex transmission. Specifically, the AP <NUM> may initiate the full-duplex transmission by sending a simultaneous transmission (i.e. DL data <NUM> to STA C 1702c) to STA C 1702c while receiving UL data <NUM> from STA A 1702a using its full-duplex capability. In one example, on the setup of the full-duplex TXOP <NUM>, the AP <NUM> may signal a STA (e.g., STA B 1702b, or STA C 1702c) or a group of STAs 1702b, 1702c (e.g., by a group ID) to indicate to the STAs 1702b, 1702c in the group that there is a possibility that they may receive an opportunistic DL transmission <NUM>. In another example, if the UL STA (e.g., STA A 1702a) sends an RTS request to the AP <NUM>, the AP <NUM> may send a CTS that explicitly signals a STA (e.g., STA B 1702b, or STA C 1702c) or a group of STAs (e.g., STA B 1702b, and STA C 1702c) to expect an opportunistic DL transmission <NUM> or implicitly informs a STA (e.g., STA B 1702b, or STA C 1702c) or a group of STAs (e.g., STA B 1702b, and STA C 1702c) to expect an opportunistic DL transmission <NUM> based on the address of the STA (e.g., STA B 1702b, or STA C 1702c) where the CTS is sent to.

Once STA A 1702a acquires a channel and finishes the UL data transmission <NUM>, the AP <NUM> may send an ACK <NUM> to STA A 1702a. and the AP <NUM> may expect a delayed ACK <NUM> from STA C <NUM> once the DL data transmission <NUM> is finished. Although it is not illustrated in <FIG>, the STA may also expect to receive an ACK <NUM> from STA C 1702c and transmit a delayed ACK <NUM> to STA A 1702a.

<FIG> illustrates illustrating an example STA procedure <NUM> for opportunistic downlink full-duplex transmission, which may be used in combination with any of other embodiments described herein. For example, an AP may define or set up a full-duplex TXOP in the BSS where the AP and STAS are located. At steps <NUM> and <NUM>, STAs A, B and C may receive indications for the FD TxOP from the AP at time t0. The AP and STAs A, B, and C in the BSS may expect a full-duplex transmission to occur during the TXOP. At step <NUM>, STA A may send an RTS to the AP at time t1. At steps <NUM> and <NUM>, STA A receives a CTS from the AP at time t2 and STA C may receive a CTS frame from the AP at time t2. The CTS directed to STA C may prepare STA C for the opportunistic DL transmission from the AP. At step <NUM>, in response to the received CTS frame, STA C may send a CTS frame to the AP at time t3. Based on these RTS/CTS frame exchanges, the AP may identify whether STA A and C are full-duplex compatible and determine whether an UL transmission from STA A or STA B will not interfere with a DL transmission to STA C.

At step <NUM>, STA A may acquire a channel and send UL data to the AP at time t4. The AP may know the duration of the UL data transmission from STA A. At step <NUM>, the AP may initiate a full-duplex transmission by sending a simultaneous transmission (i.e. DL data) to STA C while receiving the UL data from STA A. The full-duplex transmission (i.e. DL data transmission from the AP to STA C) may occur at any time during the duration of the UL data transmission from STA A to the AP. Once STA A finishes the UL data transmission, at step <NUM>, STA A may receive an ACK from the AP at time t5. At step <NUM>, STA C may send a delayed ACK to the AP when the DL data transmission from the AP is finished at time t6. Although it is not illustrated in <FIG>, STA C may transmit an ACK to the AP at time t5 and STA A may receive a delayed ACK from the AP at time t6. It is noted that the AP may transmit a full-duplex preamble to estimate full-duplex equalizers/filters at any time before the full-duplex transmission occurs.

In one embodiment, there may be procedures for opportunistic asymmetric full-duplex uplink transmission. In this embodiment, the STAs may be half-duplex but the AP may have full-duplex capability.

In one scenario, the procedure may be AP controlled where the AP sends a DL transmission to a STA (e.g., STA C) and multiple STAs may desire to send data opportunistically to the uplink due to the full-duplex capabilities of the AP. Because of the opportunistic nature of the scenario, it may be necessary for the AP to set up the full-duplex filters before transmission of data to the uplink STA to be able to dynamically switch to full-duplex transmission.

<FIG> illustrates an example process <NUM> for opportunistic asymmetric full-duplex uplink transmission for a pre-configured station (STA), which may be used in combination with any of other embodiments described herein. This example procedure <NUM> may start with an AP <NUM> defining or setting up a full-duplex TXOP <NUM> in which the AP <NUM> and STAs 1902a, 1902b, 1902c in the BSS may expect a full-duplex transmission to occur. In one example, a two-hop RTS RTS/CTS procedure may be used. In another example, a Restricted Access Window dedicated to full-duplex transmission may be set up. The AP <NUM> may transmit a full-duplex preamble <NUM> to estimate full-duplex equalizers/filters before the full-duplex transmission occurs.

In this example, the STA(s) (e.g., STA A 1902a) that opportunistically transmit (e.g., UL Data transmission <NUM> from STA A 1902a) may be pre-configured. As illustrated in <FIG>, the AP <NUM> may initiate a full-duplex transmission by sending a DL data <NUM> to STA C 1902c. In one example, during the setup of the full-duplex TXOP <NUM>, the AP <NUM> may configure a STA (e.g., STA A 1902a) or a group of STAs (e.g., by a group ID) to transmit opportunistically to the AP <NUM>. In another example, the AP <NUM> may send an RTS or a CTS to configure a STA (e.g., STA A 1902a) or a group of STAs to transmit opportunistically to the AP <NUM>. For example, if the AP <NUM> transmits DL data <NUM> to STA C 1902c, only STA A 1902a may be allowed to transmit UL data <NUM> simultaneously to the AP <NUM>.

Once STA A 1902a finishes the opportunistic UL data transmission <NUM> to the AP <NUM>, the AP <NUM> may send an ACK <NUM> to STA A 1902a. The AP <NUM> may expect to receive a delayed ACK <NUM> from STA C 1902c after the DL data transmission <NUM> is finished. Although it is not illustrated in <FIG>, the AP <NUM> may receive an ACK first from STA C 1902c and transmit a delayed ACK to STA A 1902a.

In one scenario, a contention gap may be set within the DL transmission to allow the uplink STAs to contend for the channel.

<FIG> illustrates an example process <NUM> for opportunistic asymmetric full-duplex uplink transmission for a single DL contention period, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, after the AP <NUM> transmit an RTS frame <NUM> to STA C 2002c for the DL data transmission <NUM>, the STA A 2002a and STA B 2002b may have contention period for opportunistic UL data transmission <NUM>. During this contention period, STA A 2002a and STA B 2002b may compete with each other to access a channel. If STA A 2002a obtains the channel access, STA A <NUM> may initiate the UL data transmission <NUM> at any time during the DL data transmission <NUM> to STA C 2002c. In this case, the contention gap or contention period may be initiated during or after the CTS <NUM> is transmitted to the AP <NUM> from STA C 2002c. As described above, STA A 2002a and STA B 2002b may contend for the channel in that duration. The details of the FD TXOP setup <NUM>, FD preamble <NUM>, an ACK <NUM> transmitted to STA A 2002a, and a delayed ACK <NUM> transmitted to the AP <NUM> may be similar to or the same as those described in <FIG>, <FIG>, and <FIG> and are not described in <FIG> for brevity.

<FIG> illustrates an example process <NUM> for opportunistic asymmetric full-duplex uplink transmission for periodic DL contention periods, which may be used in combination with any of other embodiments described herein. In this example, multiple contention gaps or contention periods may be initiated at a configurable duration after the commencement of the downlink transmissions <NUM>, <NUM>, <NUM> to STA C 2102c or a set of configurable durations after the commencement of the downlink transmissions <NUM>, <NUM>, <NUM> to STA C 2102c. Similar to <FIG>, during these contention periods, STA A 2002a and STA B 2002b may compete with each other to access the channel. If STA A 2002a obtains the channel access, STA A 2002a may initiate the UL data transmission <NUM> to the AP <NUM>. The UL data transmission <NUM> from STA A 2102a may or may not overlap one or more DL data transmissions <NUM>, <NUM>, <NUM> to STA C 2102c. The contention gaps or contention periods may function as a quiet mid-amble during the downlink transmission. The details of the FD TXOP setup <NUM>, FD preamble <NUM>, an ACK <NUM> transmitted to STA A 2002a, and a delayed ACK <NUM> transmitted to the AP <NUM> may be similar to or the same as those described in <FIG>, <FIG>, and <FIG> and are not described in <FIG> for brevity.

<FIG> illustrates an example process <NUM> for opportunistic asymmetric full-duplex uplink transmission with a periodic trigger frame, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, one or more full-duplex trigger frames <NUM>, <NUM> may be inserted (or transmitted) in multiple DL data transmissions <NUM>, <NUM>, <NUM>. The periodic full-duplex trigger frames <NUM>, <NUM> may be directed to STA A 2202a or STA B 2202b. If STA A 2202a receives the full-duplex trigger frame <NUM>, STA A 2202a may transmit the UL data <NUM> simultaneously until the AP <NUM> finishes its DL data transmissions <NUM>, <NUM>, <NUM> to STA C 2202c. The full-duplex trigger frames <NUM>, <NUM> may schedule specific STAs in specific Resource Units (RUs) or may allow for random access within each RU. The details of the FD TXOP setup <NUM>, FD preamble <NUM>, an ACK <NUM> transmitted to STA A 2202a, and a delayed ACK <NUM> transmitted to the AP <NUM> may be similar to or the same as those described in <FIG>, <FIG>, and <FIG> and are not described in <FIG> for brevity.

In an embodiment, a procedure for opportunistic asymmetric full-duplex uplink transmission may be used by opportunistic STAs (STA A and STA B). The STAs, STA A and STA B, may receive the full-duplex TXOP setup frame from the AP. The FD TXOP frame may setup the full-duplex TXOP duration. The STAs, STA A and STA B, may receive the full-duplex preamble that is used by the AP to set up the full-duplex filter or full-duplex cancellation circuits (for example, the analog and/or digital cancellation circuits).

The STAs (e.g., STA A, STA B, and STA C) may receive a frame indicating the parameters of the uplink opportunistic transmission. In one example, the frame may identify the STA(s) to receive the downlink transmission, where the STAs that perform opportunistic full-duplex uplink may be implicitly identified. In another example, the frame may identify a single STA or a group of STAs that may access the channel opportunistically, where this group of STAs may be identified, for example, individually by their STA IDs or by a group ID.

The received frame may identify the specific method of opportunistic uplink. In one example, the method may indicate that one or more STAs are allowed specific resources to transmit on. In another example, the method may indicate one or more contention gaps or contention periods for the STAs during which the STAs may contend for the channel, where in the event of multiple contention gaps, the gaps may be periodic or the frame may identify when they will be active (i.e., the timing). In another example, the method may indicate one or more mid-frame full-duplex triggers during which the STA may be assigned to one or more resource units (RUs) within the uplink or may contend for one or more RUs within the uplink; when an RU spans the entire bandwidth, this method may also include the ability to transmit across the entire band.

The received frame for setup may also be sent as a standalone frame, with the full-duplex preamble or may be sent when the downlink transmission is scheduled.

Once the frame is received, STA A and STA B may receive information from the AP identifying that STA C will be receiving a data transmission and the duration of the transmission. Afterwards, STA A and B may send an opportunistic uplink transmission during the DL transmission to STA C based on the specific method that is defined.

<FIG> illustrates an example taxonomy of channel access schemes for asymmetric full-duplex transmission, which may be used in combination with any of other embodiments described herein. As illustrated in <FIG>, the asymmetric full-duplex transmission <NUM> may be categorized as synchronized full-duplex transmission <NUM>, opportunistic downlink full-duplex transmission <NUM>, and opportunistic uplink full-duplex transmission <NUM>. The synchronized full-duplex transmission <NUM> may be initiated by an FD trigger frame <NUM> or an FD RTS/CTS frames <NUM> without the FD trigger frame <NUM>. The opportunistic downlink full-duplex transmission <NUM> may occur during FD TXOP <NUM> and based on FD DL group <NUM> or STAs that are preconfigured <NUM>. The opportunistic uplink full-duplex transmission <NUM> may be initiated based on periodic contention periods <NUM> or periodic FD trigger frames <NUM>.

In one embodiment, a device or a system may adaptively switch between half-duplex and full-duplex transmission. A full-duplex trigger frame may be used by the AP to enable the system to adaptively switch between half-duplex and full-duplex. In this example, the device or the system may default to a half-duplex transmission system and switch to full-duplex upon receipt or transmission of a full-duplex trigger frame that defines one or more parameters, such as the STA(s) to be transmitted to/from in the full-duplex transmission; the start and end of the full-duplex transmission; the time duration/periodicity of the full-duplex mid-amble; the time-frequency resources for STA full-duplex preamble transmission, to enable the STA to estimate full-duplex filters for symmetric full-duplex transmissions; and/or the resources assigned to each STA.

For the resources assigned to each STA, in an OFDMA transmission, the full-duplex trigger frame may assign some RU resources as full-duplex or half-duplex depending on transmission conditions (e.g., the traffic available, or the full-duplex filter effectiveness for different resources). In a non-OFDMA transmission, the full-duplex trigger frame may assign channel bands (e.g., on a <NUM>, <NUM>, <NUM>, <NUM> or <NUM> granularity) as full-duplex or half-duplex depending on transmission conditions (e.g., the traffic available, or the full-duplex filter effectiveness for different resources).

In an adaptively switching procedure, the STA may receive a full-duplex trigger frame. On receipt of the trigger, the STA may read the receive resource allocation field. If the STA identifies resources for reception, the STA may commence reception of the downlink full-duplex packet at a fixed duration (e.g., a SIFS) from the end of the full-duplex trigger frame.

Also on receipt of the full-duplex trigger frame, the STA may receive the transmit resource allocation field. If the STA identifies resources for transmission, the STA may commence transmission of the uplink full-duplex packet at a fixed duration (e.g., a SIFS) from the end of the full-duplex trigger frame.

Also on receipt of the trigger, the STA may receive the AP full-duplex preamble-midamble field. If a preamble/mid-amble is identified, the STA may cease transmission/reception for the duration of the pre-amble-midamble field.

For this procedure, if the architecture is a symmetric full-duplex system, the full-duplex trigger may signal time duration for the STA full-duplex preamble transmission.

In one embodiment, there may be procedures for SIG detection based back off. This embodiment may address issues with the unfairness for STA <NUM> to use a Preamble plus SIG based back off procedure. Such a procedure may be used by STA <NUM> to determine whether to expect a corrupted packet due to the subsequent full-duplex operation of the AP with STA <NUM>, since prior to initiation of full-duplex operation the AP may coordinate with the STA the parameters for subsequent full-duplex operation using the SIG.

In one procedure a device, such as an AP or STA, may perform a clear channel assessment (CCA) of the medium using a standard half-duplex transmission prior to initiating full-duplex operation. The device may send a RTS to STA <NUM>, and wait for ACK after SIFS. The STA <NUM> may overhear the preamble plus SIG of the RTS and determine the RTS is for full-duplex operation. The STA <NUM> may then modify its back-off procedure to use DIFS instead of EIFS for receipt of a corrupted packet.

In an additional or alternative scenario, the STA <NUM> may also overhear a CF-Poll frame to determine that full-duplex operation may have begun by the AP with STA <NUM>.

Claim 1:
A method (<NUM>) performed
in a full-duplex, FD, compatible access point, AP, the method
comprising:
in response to receiving (<NUM>) a request to send, RTS, frame from a first station, STA, transmitting (<NUM>) a full-duplex clear to send, FD CTS, frame to the first STA and a full-duplex request to send, FD RTS, frame to a second STA;
sending (<NUM>), to the FD compatible AP itself,
an FD preamble to set up an FD filter, wherein the FD preamble includes training information to enable the FD compatible AP to perform FD filter estimation;
in response to transmitting (<NUM>) the FD RTS frame to the second STA, receiving a clear to send (CTS) frame from the second STA; and
transmitting (<NUM>), to both the first STA and the second STA, a full-duplex, FD, trigger frame that includes scheduling information to trigger FD communication with the first STA for uplink, UL, data and the second STA for downlink, DL, data at a same time.