Media access control for full duplex communications

Methods and apparatuses for asymmetric full duplex (FD) communications. Information about an uplink (UL) transmission opportunity (TXOP), including an indication of the TXOP, is sent by an access point (AP). The AP sends a downlink (DL) transmission to a receiving station. During the TXOP, an UL transmission is received from a transmitting station. The UL transmission at least partially overlaps in time with the DL transmission. Acknowledgement of the UL transmission is sent to the transmitting station, and acknowledgement of the DL transmission is received from the receiving station, at a synchronized time.

FIELD

The present disclosure is related to methods and systems for full duplex communications in Wi-Fi communications. In particular, the present disclosure is related to methods and systems suitable for asymmetric full duplex Wi-Fi communications.

BACKGROUND

In full duplex (FD) communications, downlink (DL) transmissions (e.g., from an access point (AP) to a station (STA)) and uplink (UL) transmissions (e.g., from a STA to an AP) can take place simultaneously.

In symmetric FD communications, the same two nodes are involved in both DL transmission and UL transmission. For example, an AP sends DL transmissions to a STA and the same STA sends UL transmissions to the AP. Because the same pair of nodes is involved in both the DL and UL transmissions, issues of synchronization of the DL and UL transmissions can be addressed in a relatively straightforward manner.

In asymmetric FD communications, DL transmission occurs between one pair of nodes (e.g., the AP and a first STA), but UL transmission involves a different third node (e.g., the AP and a second STA). The first STA and second STA may not be synchronized, and the DL transmission and UL transmission may interfere with each other. It would be desirable to provide an improved way to coordinate such FD communications, for example a way for the AP to coordinate timing of the DL and UL transmissions.

SUMMARY

In various examples described herein, methods and systems for carrying out FD communications are described. The AP may provide information about an UL transmission opportunity (TXOP) in the header of a DL frame, for example. The AP may also transmit a block acknowledgement request (BAR) frame, to synchronize acknowledgements (ACKs) of the DL and UL transmissions.

In some aspects, the present disclosure describes a method for asymmetric FD communications. The method includes sending information about an UL TXOP. The information about the TXOP includes an indication of the TXOP. The method also includes sending a DL transmission to at least one first receiving station. The method also includes, during the TXOP, receiving an UL transmission from at least one second transmitting station. The UL transmission at least partially overlaps in time with the DL transmission. The method also includes sending acknowledgement of the UL transmission to the at least one second transmitting station and receiving acknowledgement of the DL transmission from the at least one first receiving station, at a synchronized time.

In any of the preceding aspects/embodiments, the method may include: at a later one of end of the UL transmission or end of the DL transmission, sending a block acknowledgement request (BAR) frame. The synchronized time may be synchronized according to the BAR frame.

In any of the preceding aspects/embodiments, the indication of the TXOP may be sent in a header of the DL transmission.

In any of the preceding aspects/embodiments, the indication of the TXOP may be sent in a trigger frame broadcast ahead of the DL transmission.

In any of the preceding aspects/embodiments, the information about the TXOP may include one or more contention parameters to permit two or more stations to compete for UL channel access.

In any of the preceding aspects/embodiments, the one or more contention parameters may include an identification of the two or more stations to compete for channel access.

In any of the preceding aspects/embodiments, the DL transmission may be a multi-user (MU) DL transmission to two or more receiving stations over respective resource units (RUs). The information about the TXOP may include an indication of two or more RUs available for UL transmission by respective ones of two or more transmitting stations. Aknowledgement of the UL transmission may be a MU acknowledgement sent to the two or more transmitting stations.

In some aspects, the present disclosure describes an AP for FD communications. The AP includes a memory; an interface for wireless communication with at least one first receiving station and at least one second transmitting station; and a processing device. The processing device is configured to execute instructions stored in the memory to cause the AP to send information about an UL TXOP. The information about the TXOP includes an indication of the TXOP. The processing device is also configured to execute instructions to cause the AP to send a DL transmission to the at least one first receiving station. The processing device is also configured to execute instructions to cause the AP to, during the TXOP, receive an UL transmission from the at least one second transmitting station. The UL transmission at least partially overlaps in time with the DL transmission. The processing device is also configured to execute instructions to cause the AP to send acknowledgement of the UL transmission to the at least one second transmitting station and receive acknowledgement of the DL transmission from the at least one first receiving station, at a synchronized time.

In any of the preceding aspects/embodiments, the processing device may be further configured to execute instructions to cause the AP to: at a later one of end of the UL transmission or end of the DL transmission, send a BAR frame. The synchronized time may be synchronized according to the BAR frame.

In any of the preceding aspects/embodiments, the indication of the TXOP may be sent in a header of the DL transmission.

In any of the preceding aspects/embodiments, the indication of the TXOP may be sent in a trigger frame broadcast ahead of the DL transmission.

In any of the preceding aspects/embodiments, the information about the TXOP may include one or more contention parameters to permit two or more stations to compete for UL channel access.

In any of the preceding aspects/embodiments, the one or more contention parameters may include an identification of the two or more stations to compete for channel access.

In any of the preceding aspects/embodiments, the DL transmission may be a MU DL transmission to two or more receiving stations over respective RUs. The information about the TXOP may include an indication of two or more RUs available for UL transmission by respective ones of two or more transmitting stations. Acknowledgement of the UL transmission may be a MU acknowledgement sent to the two or more transmitting stations.

In some aspects, the present disclosure describes a method for asymmetric FD communications. The method includes receiving, in a frame header of a DL transmission sent from an AP to at least one other DL receiving station, information about an UL TXOP. The information about the TXOP includes an indication of the TXOP. The method also includes sending an UL transmission to the AP, using the information about the TXOP. The UL transmission at least partly overlaps in time with the DL transmission. The method also includes receiving acknowledgement of the UL transmission from the AP.

In any of the preceding aspects/embodiments, the method may include receiving a BAR frame. The acknowledgement of the UL transmission may be received at a synchronized time that is synchronized according to the BAR frame.

In any of the preceding aspects/embodiments, the method may include competing for channel access to send the UL transmission. The competing may be carried out in accordance with one or more contention parameters included in the information about the TXOP.

In any of the preceding aspects/embodiments, the one or more contention parameters may include an identification of two or more stations to compete for channel access.

In some aspects, the present disclosure describes a STA for participating in FD communications. The STA includes a memory; an interface for wireless communication with an AP; and a processing device. The processing device is configured to execute instructions stored in the memory to cause the STA to: receive, in a frame header of a DL transmission sent from the AP to at least one other DL receiving station, information about an UL TXOP. The information about the TXOP includes an indication of the TXOP. The processing device is also configured to execute instructions to cause the STA to send an UL transmission to the AP, using the information about the TXOP. The UL transmission at least partly overlaps in time with the DL transmission. The processing device is also configured to execute instructions to cause the STA to receive acknowledgement of the UL transmission from the AP.

In any of the preceding aspects/embodiments, the processing device may be further configured to execute instructions to cause the STA to: receive a BAR frame. The acknowledgement of the UL transmission may be received at a synchronized time that is synchronized according to the BAR frame.

In any of the preceding aspects/embodiments, the processing device may be further configured to execute instructions to cause the STA to: compete for channel access to send the UL transmission. The competing may be carried out in accordance with one or more contention parameters included in the information about the TXOP.

In any of the preceding aspects/embodiments, the one or more contention parameters may include an identification of two or more stations to compete for channel access

In some aspects, the present disclosure describes a method for asymmetric FD communications. The method includes receiving a DL transmission from an AP. The method also includes receiving a BAR frame from the AP. The method also includes sending acknowledgement of the DL transmission to the AP at a synchronized time that is synchronized according to the BAR frame.

In some aspects, the present disclosure describes a STA for participating in FD communications. The STA includes a memory; an interface for wireless communication with an AP; and a processing device. The processing device is configured to execute instructions stored in the memory to cause the STA to receive a DL transmission from the AP. The processing device is also configured to execute instructions to cause the STA to receive a BAR frame from the AP. The processing device is also configured to execute instructions to cause the STA to send acknowledgement of the DL transmission to the AP at a synchronized time that is synchronized according to the BAR frame.

In any of the preceding aspects/embodiments, the BAR frame may include identification of a RU for sending the acknowledgement. The acknowledgement may be sent using the identified RU.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Examples described herein provide methods and systems for carrying out asymmetric FD communications. The AP may provide information about an UL transmission opportunity (TXOP) in the header of a DL frame, for example. The AP may also transmit a block acknowledgement request (BAR) frame, to synchronize acknowledgements (ACKs) of the DL and UL transmissions.

FIG. 1Ais a schematic diagram of an example system100in which methods described herein may be implemented. The system100illustrates a Wi-Fi infrastructure, where transmissions all go through an access point (AP)102, which has full duplex (FD) capabilities. The AP102may be also referred to as a principal control point (PCP) or a base station. The AP102may be implemented as a router, for example. Multiple stations (STAs)104are associated with the AP102. Each STA104may operate independently of each other, with different capabilities. For example, each STA104may or may not have FD capabilities. In the example shown, there are 6 STAs, each labeled STA1to STA6(individually,104-1to104-6; generally referred to as STAs104). The STAs104may also be referred to as terminals, user devices, user equipment (UE) or clients, for example. Each STA104may be any suitable device capable of wireless communication, including mobile or stationary devices such as smartphones, laptops, mobile phones or tablet devices, for example, and the STAs104need not be the same as each other.

The system100may support communication between the AP102and each STA104, as well as communication directly between STAs104(also referred to as device-to-device communication). The AP102may also carry out multi-user transmissions (e.g., transmissions from the AP102to multiple STAs104simultaneously), for example by using directional antennas.

FIG. 1Bis a block diagram illustrating an example processing system150, which may be used to implement the methods and systems disclosed herein, for example the AP102and/or one or more of the STAs104. Other processing systems suitable for implementing the present disclosure may be used, which may include components different from those discussed below. AlthoughFIG. 1Bshows a single instance of each component, there may be multiple instances of each component in the processing system150.

The processing system150includes one or more processing devices152, such as a processor, a microprocessor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a dedicated logic circuitry, or combinations thereof. The processing system150may also include one or more input/output (I/O) interfaces154, which may enable interfacing with one or more appropriate input devices164and/or output devices166. The processing system150includes one or more network interfaces156for wired or wireless communication with a network (e.g., an intranet, the Internet, a P2P network, a WAN, a LAN, and/or a Radio Access Network (RAN)), including one or more nodes of the network. The network interface(s)156may include wired links (e.g., Ethernet cable) and/or wireless links for intra-network and/or inter-network communications. The network interface(s)156may provide wireless communication via one or more transmitters/receivers or transceiver antennas168, for example. The antennas168may act together as an antenna array, in which case each antenna168may be referred to as an antenna element or radiating element of the antenna array. There may be a plurality of such antenna arrays. The processing system150may also include one or more storage units158, which may include a mass storage unit such as a solid state drive, a hard disk drive, a magnetic disk drive and/or an optical disk drive.

The processing system150may include one or more memories160, which may include a volatile or non-volatile memory (e.g., a flash memory, a random access memory (RAM), and/or a read-only memory (ROM)). The non-transitory memory(ies)160may store instructions (e.g., in the form of software modules) for execution by the processing device(s)152, such as to carry out the methods described in the present disclosure. The memory(ies)160may include other software instructions, such as for implementing an operating system and other applications/functions. In some examples, one or more data sets and/or module(s) may be provided by an external memory (e.g., an external drive in wired or wireless communication with the processing system150) or may be provided by a transitory or non-transitory computer-readable medium. Examples of non-transitory computer readable media include a RAM, a ROM, an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a flash memory, a CD-ROM, or other portable memory storage.

There may be a bus162providing communication among components of the processing system150, including the processing device(s)152, I/O interface(s)154, network interface(s)156, storage unit(s)158and/or memory(ies)160. The bus162may be any suitable bus architecture including, for example, a memory bus, a peripheral bus or a video bus.

InFIG. 1B, the input device(s)164(e.g., a keyboard, a mouse, a microphone, a touchscreen, and/or a keypad) and output device(s)166(e.g., a display, a speaker and/or a printer) are shown as external to the processing system150. In other examples, one or more of the input device(s)164and/or the output device(s)166may be included as a component of the processing system150. In other examples, there may not be any input device(s)164and output device(s)166, in which case the I/O interface(s)154may not be needed.

The AP102and STAs104may each include multiple antenna elements168forming antenna arrays, and may carry out appropriate beamforming and beam steering controls (e.g., using beamsteering circuits and/or beamsteering control modules implemented by the processing device152and processing system150), in order to carry out directional wireless communication.

Returning toFIG. 1A, the AP102initiates a downlink (DL) transmission110to STA1104-1. The DL transmission110may include a frame (e.g., data frame), with a frame header (e.g., a physical layer (PHY) header or media access control (MAC) header) providing information about an uplink (UL) transmission opportunity (TXOP) (e.g., an indication of the TXOP). This is described in further detail below.

The other STAs104associated with the AP102may also receive this TXOP information (e.g., overhear on the DL transmission110). A STA104may be able to take advantage of the TXOP to send an UL transmission to the AP102. In the example shown, a UL transmission120is sent from STA5104-5to the AP102, overlapping in time with the DL transmission110. In some examples, the AP102may further indicate (e.g., in the TXOP information provided in the header of the DL transmission110) a maximum transmit power level or a permitted range of transmit power level for the UL transmission120, so as to avoid or reduce possible interference with the ongoing DL transmission110.

If multiple STAs104wish to send an UL transmission, the AP102may select a particular STA104for the UL transmission. Alternatively, two or more STAs104(which may or may not be selected by the AP102) may compete for accessing the channel for the UL transmission.

In the case that the AP102selects a particular STA104for UL transmission, this may be referred to as the “scheduled” case. The AP102may have information about the geographical or spatial location of each associated STA104, and may use this information to select a particular STA104for UL transmission120that is not expected to significantly interfere with the other STA104receiving the DL transmission110. In the example ofFIG. 1A, the AP102has selected STA5104-5for the UL transmission120, where the spatial location of STA5104-5is such that the UL transmission120is not expected to interfere with STA1104-1receiving the DL transmission110(e.g., STA5104-5and STA1104-1are located in different transmission sectors).

In the case that the STAs104compete for access to the channel for UL transmission, this may be referred to as the “contention” case. The AP102may select the group of two or more STAs104that may compete for channel access. For example, the AP102may determine that there are two or more STAs104in one or more transmission sectors that would not significantly interfere with the DL transmission110, and select those two or more STAs104to compete for channel access. Any suitable contention protocol for channel access may be used. For example, contention could be implemented using a random access mechanism, in which each competing STA104generates a random number and counts down to zero. The count may optionally be decremented only when the STA104detects that the channel is below a certain power threshold (e.g., less than the maximum transmit power level indicated by the AP102in the header). By decrementing the count only when the channel is below a certain power threshold, this may help to ensure that the channel is accessed for the UL transmission120only when the transmit power level of the UL transmission120is low enough to reduce or avoid interference with the DL transmission110.

Further details of the TXOP information are now described.FIG. 2illustrates an example timing diagram for the contention case. The DL transmission110includes a frame having a header112, which includes the PHY header and the MAC header of the transmission frame. The TXOP information114may be carried in the PHY header, the MAC header, or both (e.g., some TXOP information carried in the PHY header and the remaining TXOP information carried in the MAC header). In some examples, the TXOP information114may be carried in the PHY header, which may help to place the TXOP information114earlier in the DL transmission110. Providing the TXOP information114earlier may allow competing STAs to begin contention sooner, if contention is used.

In some examples, at least some of the TXOP information114(e.g., indication of the TXOP, to inform other STAs of the opportunity for UL transmission) may be provided using a special purpose frame, such as a trigger frame. The trigger frame, which may also contain other information, may provide the indication of the TXOP, with other TXOP information114being carried in the header112of the DL transmission110. In other examples, the TXOP trigger frame may carry some or all of the TXOP information114.

The TXOP information114may include an indication of one or more STAs104(e.g., selected by the AP102) for the UL transmission120. In the scheduled case, the TXOP information114may include an indication (e.g., user equipment identifier (UEID)) of the STA104selected by the AP102for UL transmission120. In the contention case, the TXOP information114may include an indication (e.g., UEID) of the group of two or more STAs104selected by the AP102to compete for channel access.

The TXOP information114may also include indication of a maximum or permitted range of power level for transmitting a communication, receiving a communication, or both. The TXOP information114may also include quality of service (QoS) information, for example the TXOP information114may indicate that the UL transmission is limited to the priority of one or more specified access categories, or at lower priority than a specified access category. Where multiple STAs104are to compete for channel access (e.g., where there are two or more STAs104indicated in the TXOP information114), contention parameters may also be included in the TXOP information114. Contention parameters may include, for example, a minimum (Wmin) and maximum (Wmax) value between which a random number is to be chosen by a STA104for random access contention. The TXOP information114may also include indication of a maximum PHY Layer Convergence Procedure (PLCP) protocol data unit (PPDU) length for the UL transmission120. The maximum PPDU length may be determined by the AP102based on the length of the DL transmission110. Indication of the maximum PPDU length may be used by the STA104sending the UL transmission120to help ensure that the UL transmission120ends at the same time as the DL transmission110(e.g., to cut off the UL transmission120or pad the UL transmission120, as appropriate). Other information may be included in the TXOP information114.

In the contention case, as illustrated byFIG. 2, when the AP102sends a DL transmission110to a first STA104(in this example, STA1104-1), other STAs104associated with the AP102may overhear the TXOP information114contained in the header112of the DL transmission110, or otherwise receive indication of the TXOP. InFIG. 2, other STAs104receive the TXOP information114during a first time period116. In the contention case, two or more competing STAs104(e.g., two or more STAs104selected by the AP102, as indicated in the TXOP information114) may then compete for channel access during a second time period, which may also be referred to as the contention period118. InFIG. 2, STA4104-4and STA5104-5compete for channel access during the contention period118. The winner of the contention (in this example, STA5104-5has a shorter contention period118and thus wins over STA4104-4) may then send the UL transmission120to the AP102after winning the contention.

FIG. 2illustrates the timing diagram in the contention case. The timing diagram may be similar for the scheduled case, with the difference that the contention period118may be omitted. That is, the UL transmission120by the selected STA104may begin immediately following the first time period116.

Another challenge in asymmetric FD communications is the transmission of acknowledgement (ACK) frames. According to the IEEE 802.11 standard, an ACK should be sent by the receiving device short interframe spacing (SIFS) time units after the end of a received transmission. However, in asymmetric FD communications the receiving device for DL transmission may not be involved in the UL transmission, so the ACK transmission for the UL transmission may interfere with or be blocked by an ongoing DL transmission or vice versa. A mechanism for coordinating ACK transmissions is therefore described below for asymmetric FD communications.

FIGS. 3 and 4illustrate two cases of asymmetric FD communications. For simplicity, no contention period is shown inFIGS. 3 and 4; however, it should be understood that the examples ofFIGS. 3 and 4may be implemented with or without contention.

InFIG. 3, the DL transmission110from the AP102to STA1104-1ends earlier than the UL transmission120from STA5104-5to the AP102. Conventionally, STA1104-1should send an ACK to the AP102after the SIFS time period following reception of the DL transmission110; that is, STA1104-1should send an ACK at202as indicated in dashed lines. However, the UL transmission120is still ongoing and hence an ACK cannot be sent by STA1104-1at202without an undesirable amount of interference. In order to coordinate or synchronize ACK transmissions, the AP102transmits a block ACK request (BAR) frame210to STA1104-1after the UL transmission120(e.g., after the SIFS time period). The BAR frame210is received by STA1104-1and is used to synchronize the ACK212from STA1104-1to the AP102and the ACK214from the AP102to STA5104-5. The ACK212from STA1104-1and the ACK214from the AP102are then sent at the same synchronized time, according to the BAR frame210.

InFIG. 4, the DL transmission from the AP102to STA1104-1ends later than the UL transmission120from STA5104-5to the AP102. Conventionally, STA5104-5expects an ACK from the AP102when the UL transmission120ends (after a SIFS time period). However, the AP102is still sending the DL transmission110and cannot send an ACK to STA5104-5. Instead, STA5104-5waits for the BAR frame210that the AP102sends to STA5104-5after the DL transmission110. The BAR frame210is also received by STA1104-1, and is used to synchronize the ACK212from STA1104-1to the AP102and the ACK214from the AP102to STA5104-5. The ACK212from STA1104-1and the ACK214from the AP102are then sent at the same synchronized time, according to the BAR frame210.

When the ACKs are synchronized in this manner, the STAs are configured to not send ACKs and not expect ACKs following a FD transmission until a BAR frame is received. For example, the TXOP information may indicate to the STAs that asymmetric FD communications are expected and that ACKs are to be synchronized according to a BAR frame.

In some examples, other methods of synchronizing ACKs may be used in asymmetric FD communications. For example, the TXOP information may include an indication of the maximum PPDU length, as described above, so that the DL and UL transmissions end at the same time. In such a case, it may not be necessary to use a BAR frame to synchronize ACKs.

FIG. 5illustrates an example method500that may be performed by a AP102for in an asymmetric FD communication.

At502, optionally, the AP102may send a trigger frame that includes TXOP information, such as an indication of TXOP. Other TXOP information, as discussed above, may be included in the trigger frame.

At504, the AP102sends the DL transmission110to a first STA (e.g., STA1104-1). If no trigger frame was sent at502, or if the trigger frame did not include all TXOP information, the DL transmission110may include TXOP information (e.g., an indication of the TXOP) in its header (e.g., PHY header, MAC header or both), as discussed above.

At506, the AP102receives a UL transmission120from a second STA (e.g., STA5104-5) during the TXOP. The UL transmission120at least partially overlaps in time with the DL transmission110.

At508, at the later of the end of the DL transmission110or the end of the UL transmission120, the AP102sends a BAR frame210. The BAR frame210may be directed to the first and second STAs involved in the DL and UL transmissions, respectively. In some examples, the BAR frame210may be broadcast to all associated STAs. Any STA not involved in the DL and UL transmissions may ignore the BAR frame210.

At510, the AP102sends an ACK of the UL transmission and receives an ACK of the DL transmission at the same synchronized time, according to the BAR frame210. For example, the synchronized time may be defined by information contained in the BAR frame210, or may be simply at a SIFS time period immediately following the BAR frame210.

In some examples, the BAR frame210may not be needed to synchronize ACKs (e.g., where the TXOP information includes information about the PPDU length, so that the UL transmission and the DL transmission ends at the same time). In that case,508may be omitted, and the ACKs may be sent at510without waiting for the BAR frame210.

FIG. 6illustrates an example method600that may be performed by a first STA (e.g., STA1104-1) receiving a DL transmission110from the AP102in an asymmetric FD communication.

At602, the first STA receives the DL transmission110from the AP102.

At604, the first STA receives the BAR frame210from the AP102. The BAR frame210may or may not immediately follow the end of the DL transmission110.

At606, the first STA sends ACK back to the AP102at the synchronized time, according to the BAR frame210.

In some examples, the BAR frame210may not be needed to synchronize ACKs (e.g., where the TXOP information includes information about the PPDU length, so that the UL transmission and the DL transmission ends at the same time). In that case,604may be omitted, and the ACK may be sent at606without waiting for the BAR frame210.

FIG. 7illustrates an example method700that may be performed by a second STA (e.g., STA5104-5) sending a UL transmission120to the AP102in an asymmetric FD communication.

At702, the second STA receives TXOP information. The TXOP information may be received in a trigger frame sent by the AP102and/or contained in a header of a DL transmission110(e.g., data frame or other DL frame) from the AP102to another STA.

At704, optionally, the second STA may compete for channel access with one or more other STAs. The contention may be carried out in accordance with contention parameters contained in the TXOP information.

At706, the second STA (after winning the contention, if necessary) sends a UL transmission120to the AP102. At least part of the UL transmission120overlaps in time with the DL transmission110.

At708, the second STA receives the BAR frame210from the AP102. The BAR frame210may or may not immediately follow the end of the UL transmission120.

At710, the second receives ACK from the AP102at the synchronized time, according to the BAR frame210.

In some examples, the BAR frame210may not be needed to synchronize ACKs (e.g., where the TXOP information includes information about the PPDU length, so that the UL transmission and the DL transmission ends at the same time). In that case,708may be omitted, and the ACK may be received at710without waiting for the BAR frame210.

The above examples may be implemented in multi-user (MU) transmission formats as well (e.g., using frequency multiplexing techniques such as orthogonal frequency division multiple access (OFDMA), or spatial multiplexing techniques such as multi-user multiple input multiple output (MU-MIMO)). An example of this is shown inFIG. 8. In this example, the DL and UL transmissions are MU frames (or PPDUs), represented inFIG. 8as stacked resource units (RUs).

The MU DL transmission310may be similar to the DL transmission110described previously, including a header312similar to the header112described previously to provide some or all of the TXOP information. The MU DL transmission310in the example shown includes four RUs transmitted to four different DL receiving STAs. Although not shown, in some examples a trigger frame may be sent (e.g., broadcast) by the AP102, as discussed previously, to provide some or all of the TXOP information, instead of or in addition to TXOP information provided in the header312. The TXOP information (whether provided by the header312or a trigger frame or both) may include an indication of the MU UL TXOP. The indication of MU UL TXOP may also include an indication of which MU resource and the number of MU resources available for UL transmission.

The UL transmitting STAs may be selected by the AP102, in a scheduled case, similarly to the previous description of the scheduled case. In the MU implementation, the AP102may assign a particular MU resource to each respective selected STA, and this information may be transmitted in the TXOP information (e.g., including an identifier of each selected STA and information relating each selected STA to a particular MU resource).

In the contention case, multiple STAs may compete for each MU resource during the contention period318. Contention may be carried out in accordance with contention parameters defined in the TXOP information (e.g., as discussed previously). The AP102may specify, in the TXOP information, which two or more STAs may compete for a particular MU resource.

In some examples, the scheduled case and the contention case may be used in combination. For example, the AP102may assign a specific UL transmitting STA for one RU and allow two or more UL transmitting STAs to compete for another RU.

The UL transmitting STAs assigned to each respective RU (in the scheduled case) or that won contention for each respective RU (in the contention case) may then send a UL transmission320to the AP102over the respective RU. In the example shown, three RUs are used for UL transmission by three different UL transmitting STAs.

Similarly to the examples ofFIGS. 3 and 4discussed above, a BAR frame330may be sent by the AP102, after the later of the end of the DL transmission310or the UL transmission320, to synchronize ACKs. In the MU implementation, the BAR frame330sent by the AP102may include identification of the RUs assigned to the respective DL receiving STAs for transmitting their respective ACKs332to the AP102. The AP102sends a multi-STA BlockAck (M-BA)334to the UL transmitting STAs to acknowledge receipt of the UL transmission320. The M-BA334and the ACKs332from the DL receiving STAs are sent at the same synchronized time, according to the BAR frame330.

The above examples describe ways of coordinating FD communications, where the AP has FD capabilities. In some cases, the above examples may be similarly implemented for a STA having FD capabilities, for example an FD-capable STA may engage in STA-to-STA FD communications with two other STAs, using the mechanisms described above.