Beamforming training in orthogonal frequency division multiple access (OFDMA) communication systems

A beamforming training packet is transmitted from a first communication device to multiple second communication devices. A trigger frame is generated at the first communication device to trigger an uplink orthogonal frequency division multiple access (OFDMA) transmission of beamforming training feedback from at least some of the multiple second communication devices. After transmission of the beamforming training packet by the first communication device, the trigger frame is transmitted to the at least some of the multiple communication devices. The uplink OFDMA transmission is then received at the first communication device. The uplink OFDMA transmission includes respective beamforming training feedback packets generated based on the beamforming training packet by respective ones of the at least some of the multiple second communication devices. The respective beamforming training feedback packets are simultaneously transmitted by the at least some of the multiple second communication devices.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication networks and, more particularly, to wireless local area networks that utilize orthogonal frequency division multiplexing (OFDM).

BACKGROUND

When operating in an infrastructure mode, wireless local area networks (WLANs) typically include an access point (AP) and one or more client stations. WLANs have evolved rapidly over the past decade. Development of WLAN standards such as the Institute for Electrical and Electronics Engineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n Standards has improved single-user peak data throughput. For example, the IEEE 802.11b Standard specifies a single-user peak throughput of 11 megabits per second (Mbps), the IEEE 802.11a and 802.11g Standards specify a single-user peak throughput of 54 Mbps, the IEEE 802.11n Standard specifies a single-user peak throughput of 600 Mbps, and the IEEE 802.11ac Standard specifies a single-user peak throughput in the gigabits per second (Gbps) range. Future standards promise to provide even greater throughputs, such as throughputs in the tens of Gbps range.

These WLANs operate in either a unicast mode or a multicast mode. In the unicast mode, the AP transmits information to one client station at a time. In the multicast mode, the same information is concurrently transmitted to a group of client stations.

SUMMARY

In an embodiment, a method for beamforming training in a wireless communication network includes transmitting, from a first communication device, a beamforming training packet to multiple second communication devices. The method also includes generating, at the first communication device, a trigger frame to trigger an uplink orthogonal frequency division multiple access (OFDMA) transmission of beamforming training feedback from at least some of the multiple second communication devices. The method further includes transmitting, with the first communication device and after transmission of the beamforming training packet by the first communication device, the trigger frame to the at least some of the multiple communication devices. The method additionally includes receiving, at the first communication device, the uplink OFDMA transmission, wherein the uplink OFDMA transmission includes respective beamforming training feedback packets generated based on the beamforming training packet by respective ones of the at least some of the multiple second communication devices, and wherein the respective beamforming training feedback packets are simultaneously transmitted by the at least some of the multiple second communication devices.

In another embodiment, an apparatus comprises a network interface device having one or more integrated circuits configured to transmit a beamforming training packet to multiple communication devices. The one or more integrated circuits are also configured to generate a trigger frame to trigger an uplink orthogonal frequency division multiple access (OFDMA) transmission of beamforming training feedback from at least some of the multiple communication devices. The one or more integrated circuits are further configured to, after transmission of the beamforming training, transmit the trigger frame to the at least some of the multiple communication devices. The one or more integrated circuits are additionally configured to receive the uplink OFDMA transmission, wherein the uplink OFDMA transmission includes respective beamforming training feedback packets generated based on the beamforming training packet by respective ones of the at least some of the multiple communication devices, and wherein the respective beamforming training feedback packets are simultaneously transmitted by the at least some of the multiple communication devices.

DETAILED DESCRIPTION

In embodiments described below, a wireless network device such as an access point (AP) of a wireless local area network (WLAN) simultaneously transmits data to multiple client stations and/or receives data simultaneously transmitted by multiple client stations. In some embodiments, the AP transmits data for the multiple clients in different orthogonal frequency division multiplexing (OFDM) sub-channels of an orthogonal frequency division multiple access (OFDMA) transmission. Similarly, multiple client stations simultaneously transmit data to the AP, in particular, each client station transmits data in a different OFDM sub-channel of an OFDMA transmission, in an embodiment. The AP is configured to beamform or steer transmissions to client stations, using channel information obtained from the client stations, in some embodiments. For example, according to an embodiment, the AP implements an explicit beamforming technique in which the AP transmits a beamforming training packet, or a sounding packet, that allows each of the multiple client stations to determine or estimate characteristics of the channel (channel information) between the AP and the client station. In an embodiment, the AP also transmits a trigger frame to trigger multiple client stations to simultaneously (e.g., in respective frequency portions) transmit feedback that includes channel information, or steering information (e.g., a steering matrix) determined based on the channel information, to the AP. The AP transmits the trigger frame after transmitting the beamforming training packet, in an embodiment. Transmitting the trigger frame after transmitting the beamforming training packet ensures that the client stations will have sufficient amount of time to obtain channel information and to generate feedback based on the channel information before the feedback is to be transmitted by the client stations to the AP, in an embodiment.

The AP is configured to operate with client stations according to at least a first communication protocol. The first communication protocol is sometimes referred to herein as “high efficiency,” “high efficiency WiFi,” “high efficiency WLAN,” “HE,” “HEW,” or 802.11ax communication protocol. The first communication protocol supports OFDMA communication between the AP and the client stations. In some embodiments, different client stations in the vicinity of the AP are configured to operate according to one or more other communication protocols that define operation in the same frequency band as the HE communication protocol but with generally lower data throughputs. The lower data throughput communication protocols (e.g., IEEE 802.11a, IEEE 802.11n, and/or IEEE 802.11ac) are collectively referred herein as “legacy” communication protocols. The legacy communication protocols do not support OFDMA communication, in an embodiment.

FIG. 1is a block diagram of an example wireless local area network (WLAN)10, according to an embodiment. An AP14includes a host processor15coupled to a network interface16. In an embodiment, the network interface16includes one or more integrate circuits (ICs) configured to operate as discussed below. The network interface16includes a medium access control (MAC) processor18and a physical layer (PHY) processor20. The PHY processor20includes a plurality of transceivers21, and the transceivers21are coupled to a plurality of antennas24. Although three transceivers21and three antennas24are illustrated inFIG. 1, the AP14includes other suitable numbers (e.g., 1, 2, 4, 5, etc.) of transceivers21and antennas24in other embodiments. In some embodiments, the AP14includes a higher number of antennas24than transceivers21, and antenna switching techniques are utilized. In an embodiment, the MAC processor18is implemented on at least a first IC, and the PHY processor20is implemented on at least a second IC. In an embodiment, at least a portion of the MAC processor18and at least a portion of the PHY processor20are implemented on a single IC.

In various embodiments, the MAC processor18and the PHY processor20are configured to operate according to a first communication protocol (e.g., a High Efficiency, HE, or 802.11ax communication protocol). In some embodiments, the MAC processor18and the PHY processor20are also configured to operate according to a second communication protocol (e.g., according to the IEEE 802.11ac Standard). In yet another embodiment, the MAC processor18and the PHY processor20are additionally configured to operate according to the second communication protocol, a third communication protocol, and/or a fourth communication protocol (e.g., according to the IEEE 802.11a Standard and/or the IEEE 802.11n Standard).

The WLAN10includes a plurality of client stations25. Although four client stations25are illustrated inFIG. 1, the WLAN10includes other suitable numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations25in various scenarios and embodiments. At least one of the client stations25(e.g., client station25-1) is configured to operate at least according to the first communication protocol. In some embodiments, at least one of the client stations25is not configured to operate according to the first communication protocol but is configured to operate according to at least one of the second communication protocol, the third communication protocol, and/or the fourth communication protocol (referred to herein as a “legacy client station”).

The client station25-1includes a host processor26coupled to a network interface27. In an embodiment, the network interface27includes one or more ICs configured to operate as discussed below. The network interface27includes a MAC processor28and a PHY processor29. The PHY processor29includes a plurality of transceivers30, and the transceivers30are coupled to a plurality of antennas34. Although three transceivers30and three antennas34are illustrated inFIG. 1, the client station25-1includes other suitable numbers (e.g., 1, 2, 4, 5, etc.) of transceivers30and antennas34in other embodiments. In some embodiments, the client station25-1includes a higher number of antennas34than transceivers30, and antenna switching techniques are utilized. In an embodiment, the MAC processor28is implemented on at least a first IC, and the PHY processor29is implemented on at least a second IC. In an embodiment, at least a portion of the MAC processor28and at least a portion of the PHY processor29are implemented on a single IC.

According to an embodiment, the client station25-4is a legacy client station, i.e., the client station25-4is not enabled to receive and fully decode a data unit that is transmitted by the AP14or another client station25according to the first communication protocol. Similarly, according to an embodiment, the legacy client station25-4is not enabled to transmit data units according to the first communication protocol. On the other hand, the legacy client station25-4is enabled to receive and fully decode and transmit data units according to the second communication protocol, the third communication protocol, and/or the fourth communication protocol.

In an embodiment, one or both of the client stations25-2and25-3, has a structure that is the same as or similar to the client station25-1. In an embodiment, the client station25-4has a structure similar to the client station25-1. In these embodiments, the client stations25structured the same as or similar to the client station25-1have the same or a different number of transceivers and antennas. For example, the client station25-2has only two transceivers and two antennas (not shown), according to an embodiment.

In various embodiments, the MAC processor18and the PHY processor20of the AP14are configured to generate data units conforming to the first communication protocol and having formats described herein. In an embodiment, the MAC processor18is configured to implement MAC layer functions, including MAC layer functions of the first communication protocol. In an embodiment, the PHY processor20is configured to implement PHY functions, including PHY functions of the first communication protocol. For example, in an embodiment, the MAC processor18is configured to generate MAC layer data units such as MPDUs, MAC control frames, etc., and provide the MAC layer data units to the PHY processor20. In an embodiment, the PHY processor20is configured to receive MAC layer data units from the MAC processor18and encapsulate the MAC layer data units to generate PHY data units such as PHY protocol data units (PPDUs) for transmission via the antennas24. Similarly, in an embodiment, the PHY processor20is configured to receive PHY data units that were received via the antennas24, and extract MAC layer data units encapsulated within the PHY data units. In an embodiment, the PHY processor20provides the extracted MAC layer data units to the MAC processor18, which processes the MAC layer data units.

The transceiver(s)21is/are configured to transmit the generated data units via the antenna(s)24. Similarly, the transceiver(s)21is/are configured to receive data units via the antenna(s)24. The MAC processor18and the PHY processor20of the AP14are configured to process received data units conforming to the first communication protocol and having formats described hereinafter and to determine that such data units conform to the first communication protocol, according to various embodiments.

In various embodiments, the MAC processor28and the PHY processor29of the client device25-1are configured to generate data units conforming to the first communication protocol and having formats described herein. In an embodiment, the MAC processor28is configured to implement MAC layer functions, including MAC layer functions of the first communication protocol. In an embodiment, the PHY processor29is configured to implement PHY functions, including PHY functions of the first communication protocol. For example, in an embodiment, the MAC processor28is configured to generate MAC layer data units such as MPDUs, MAC control frames, etc., and provide the MAC layer data units to the PHY processor29. In an embodiment, the PHY processor29is configured to receive MAC layer data units from the MAC processor28and encapsulate the MAC layer data units to generate PHY data units such as PPDUs for transmission via the antennas34. Similarly, in an embodiment, the PHY processor29is configured to receive PHY data units that were received via the antennas34, and extract MAC layer data units encapsulated within the PHY data units. In an embodiment, the PHY processor29provides the extracted MAC layer data units to the MAC processor28, which processes the MAC layer data units.

The transceiver(s)30is/are configured to transmit the generated data units via the antenna(s)34. Similarly, the transceiver(s)30is/are configured to receive data units via the antenna(s)34. The MAC processor28and the PHY processor29of the client device25-1are configured to process received data units conforming to the first communication protocol and having formats described hereinafter and to determine that such data units conform to the first communication protocol, according to various embodiments.

FIG. 2is a diagram of an example transmission sequence200in a WLAN, such as the WLAN10ofFIG. 1, according to an embodiment, in which an AP, such as the AP14, performs beamforming training with multiple client stations, such as multiple ones of the client stations25. The AP14transmits an announcement frame202to multiple client stations25. The announcement frame202is a downlink (DL) frame because the announcement frame204is transmitted in the downlink direction from the AP14to the client stations25, in an embodiment. In an embodiment, the announcement frame202identifies client stations25that are to participate in the beamforming training. For example, the announcement frame204includes a respective identifier, such as an association identifier (AID) or a partial AID (PAID), associated with each client station25that is an intended participant of the beamforming training, in an embodiment. In an embodiment, the announcement frame202is a null data packet announcement (NDPA) frame. In an embodiment, the announcement frame202is a broadcast control frame that occupies the entire bandwidth of the communication channel in which the beamforming training is being performed. Thus, for example, in an embodiment in which the beamforming training is being performed in an 80 MHz-wide communication channel, the announcement frame202occupies an 80 MHz bandwidth. As another example, in an embodiment in which the beamforming training is being performed in a 40 MHz-wide communication channel, the announcement frame202occupies a 40 MHz bandwidth. In another embodiment, in which the beamforming training is being performed in a communication channel of another suitable width, the announcement frame202occupies a corresponding bandwidth of the other suitable width.

After transmitting the announcement frame202, the AP14transmits a beamforming training packet204, such as a null data packet (NDP), to sound the communication channel. The beamforming training packet204is a DL packet, in an embodiment. The beamforming training packet204occupies the bandwidth of the communication channel in which the beamforming training is being performed (i.e., the communication channel being sounded), in an embodiment. The beamforming training packet204includes one or more training signals, such as one or more training fields (e.g., long training fields (LTFs)), that allow each of the multiple client stations25to estimate the channel between the AP14and the client station25, in an embodiment. In an embodiment, the AP14initiates transmission of the beamforming training packet204upon expiration of a predetermined time interval after the end of transmission of the announcement frame202. In an embodiment, the predetermined time interval is a time interval corresponding to a short inter-frame space (SIFS) defined by the first communication protocol (e.g., IEEE 802.11ax) and/or by a legacy communication protocol (e.g., the IEEE 802.11n/ac). In another embodiment, the predetermined time interval is a suitable time interval different from SIFS time interval. In another embodiment, the predetermined time interval is a suitable time interval different from a SIFS time interval.

After transmitting the beamforming training packet204, the AP14transmits a trigger frame206to trigger transmission of beamforming feedback from at least some of the multiple client stations25, which are participating in the beamforming training, to the AP14. The trigger frame206is a DL frame, in an embodiment. In an embodiment, the AP14initiates transmission of the trigger frame206upon expiration of a predetermined time interval after the end of transmission of the beamforming training packet204. In an embodiment, the predetermined time interval is a time interval corresponding to the SIFS time interval defined by the first communication protocol (e.g., IEEE 802.11ax) and/or by a legacy communication protocol (e.g., the IEEE 802.11n/ac). In another embodiment, the predetermined time interval is a suitable time interval different from a SIFS time interval. In an embodiment, the trigger frame206triggers the at least some of the multiple client stations25to transmit respective feedback packets simultaneously, using different frequency portions of an uplink OFDMA transmission from the at least some of the client stations25to the AP14. The trigger frame206includes one or more fields for specifying one or more of i) a trigger type (e.g., that the trigger frame206is a beamforming trigger, ii) one or more PHY parameters that are to be utilized for transmission of feedback, iv) resource unit allocations indicating which frequency portions correspond with which client stations, etc., according to various embodiments. The trigger frame206has a suitable format, such as a format described in U.S. patent application Ser. No. 14/961,380 and/or U.S. patent application Ser. No. 14/961,635, or another suitable format, according to various embodiments.

In response to receiving the trigger frame206, the at least some of the multiple client stations25triggered by the trigger frame206transmit beamforming feedback (e.g., feedback packets) in an OFDMA transmission208to the AP14. The OFDMA transmission208is an uplink (UL) transmission because OFDMA transmission208is transmitted in the uplink direction from the client stations25to the AP14, in an embodiment. In an embodiment, each client station25initiates transmission of the feedback (e.g., a feedback packet) upon expiration of a predetermined time interval, such as, for example, a time interval corresponding to SIFS, after completion of reception of the trigger frame206. Because, in the transmission sequence200, the beamforming training packet204is transmitted by the AP14before the trigger frame206is transmitted by the AP14, the client stations25have sufficient amount of time to perform channel estimation based on the beamforming training packet204, and to generate the feedback based on the channel estimation, in an embodiment. Accordingly, transmission of the feedback packets by the client stations25as parts of the uplink OFDMA transmission208can begin upon expiration of a relatively short time interval after the end of reception of the trigger frame204by the client stations25, such as the time interval corresponding to SIFS, in an embodiment.

FIG. 3is a diagram of an example transmission sequence300in a WLAN, such as the WLAN10ofFIG. 1, according to an embodiment, in which an AP, such as the AP14, performs beamforming training with multiple client stations, such as multiple ones of the client stations25. The transmission sequence300is similar to the transmission sequence200ofFIG. 2except that the announcement frame202in the transmission sequence200is replaced with an announcement frame302. Unlike the announcement frame202which occupies an entire bandwidth of the channel in which the beamforming training is being performed, the announcement frame302is a duplicate frame that is duplicated in each of a plurality of subchannels of the channel in which the beamforming training is being performed. Thus, for example, in an embodiment in which the beamforming training is being performed in an 80 MHz-wide communication channel, the announcement frame202is duplicated in each of four 20 MHz-wide subchannels of the 80 MHz-wide communication channel, in an embodiment. As another example, in an embodiment in which the beamforming training is being performed in a 40 MHz-wide communication channel, the announcement frame202is duplicated in each of two 20 MHz-wide subchannels of the 40 MHz-wide communication channel, in an embodiment. The announcement frame202is duplicated in another suitable number of subchannels of the communication channel in which the beamforming training is being performed, in another embodiment.

In an embodiment, the announcement frame302has a format the same as or similar to a beamforming announcement frame defined by a legacy communication protocol, such as the IEEE 802-11n/ac Standard. In an embodiment, a legacy communication device is configured to receive, decode, and at least partially understand information included in the announcement frame302. Such format of the announcement frame302allows one or more legacy client stations, such as the legacy client station25-4, along with one or more non-legacy client stations, such as the client stations25-1,25-2,15-3, to participate in the beamforming training, in an embodiment. In an embodiment, however, such format of the announcement frame302is used even when the plurality of client stations that are intended participants of the beamforming training being announced by the announcement frame does not include any legacy client stations.

FIG. 4is a diagram of an example transmission sequence400in a WLAN, such as the WLAN10ofFIG. 1, according to an embodiment, in which an AP, such as the AP14, performs beamforming training with multiple client stations, such as multiple ones of the client stations25. The transmission sequence400is similar to the transmission sequence300ofFIG. 3, except that the transmission sequence400includes transmission of feedback by a legacy client station, such as the legacy client station25-4, in an embodiment. For example, the multiple client stations25that are participating in the beamforming training include a legacy client station that is not configured to operate according to the first communication protocol, in an embodiment. The legacy client station is not configured for OFDMA communication, in an embodiment.

In an embodiment, in the scenario illustrated inFIG. 4, the announcement frame302identifies the legacy client station among the multiple client stations that are intended participants in the beamforming training being announced by the announcement frame302. The legacy client station is able to receive and decode the announcement frame302and to determine, based on the announcement frame302, that the legacy client station is to participate in the beamforming training being announced by the announcement frame302, in an embodiment. The legacy client station then receives the beamforming training packet204, transmitted by the AP14to the multiple of client stations25that include the legacy client station, and generates feedback based on the beamforming training packet204, in an embodiment.

The trigger frame206triggers at least some of the non-legacy client stations to transmit feedback from at least some of non-legacy client stations25of the plurality of client stations25that are participating in the beamforming training announced by the announcement frame302, in an embodiment. After receiving the uplink OFDMA transmission208that includes respective feedback packets from the at least some of the non-legacy client stations25triggered by the trigger frame302, the AP14transmits a poll frame410. The poll frame410is a duplicate frame that is duplicated in each of a plurality of subchannels of the communication channel in which the beamforming training is being performed, in an embodiment. In an embodiment, the poll frame410has a beamforming feedback poll frame format defined by the legacy communication protocol according to which the legacy client station is configured to operate, such the IEEE 802.11n/ac Standard. In an embodiment, the AP14initiates transmission of the poll frame410upon expiration of a predetermined time interval, such as for example a time interval corresponding to SIFS, after completion of reception of the OFDMA transmission208.

In response to receiving the poll frame410, the legacy client station transmits a feedback packet412to the AP14. In an embodiment, if more than one client legacy station is participating in the beamforming training, the AP14transmits additional poll frames after receiving the BF feedback412from the legacy client station polled by the poll frame410. Thus, for example, the transmission sequence400includes one or more additional frame exchanges410,412via which the AP14obtains feedback from one or more additional In an embodiment, the one or more additional poll frames transmitted by the AP14trigger, one by one, trigger additional legacy client station(s) to transmit feedback packets to the AP14as defined by the by the legacy communication protocol according to which the legacy client stations are configured to operate, such the IEEE 802.11n/ac Standard.

FIG. 5Ais a block diagram of an announcement frame500, according to an embodiment. In an embodiment, the announcement frame500corresponds to the announcement frame202ofFIG. 2or the announcement frame302ofFIGS. 3 and 4. The announcement frame500includes a plurality of fields, including a frame control field502, a duration/ID field504, a first address field (e.g., a receiver address (RA) field)506, a second address field (e.g., a transmitter address (TA) field)508, a frame body field510and a frame check field512.

In an embodiment, the duration/ID field504includes an indication of a duration until the end of a transmission opportunity (TXOP) for the beamforming training initiated by the announcement frame500. The first address field (RA field)506includes a broadcast MAC address to indicate that the announcement frame500is being broadcast to a plurality of client stations25, in an embodiment. The second address field (TA field)508includes the address of the AP14, in an embodiment. In an embodiment, the frame body510includes identifies client station25that are to participate in the beamforming training procedure, and also indicates beamforming control information to the identified client stations25. Referring toFIG. 5B, in an embodiment, the frame body510includes a sounding token field520and per-STA information fields522. The frame body510also includes padding bits524, in some embodiments and scenarios. In an embodiment, padding bits524include one or more bits to ensure that the frame body510includes a number of bits that is an integer multiple of an octet. In another embodiment, padding bits524include one or more bits to provide sufficient time for a receiving device (e.g., a client station) to generate the uplink transmission being triggered by the trigger frame500. In some embodiments and/or scenarios, the frame body510omits the padding bits524.

FIG. 5Cis a diagram of the per-STA information fields522, according to an embodiment. The per-STA information fields522includes a plurality of subfields530, each subfield530corresponding to a particular client station or to a particular client station25, in an embodiment. As illustrated inFIG. 5D, each per-STA information field530includes an STAID subfield532and a feedback control information subfield534. In an embodiment, the STAID subfield532identifies a particular client station25that is an intended participant in the beamforming training procedure. In an embodiment, the STAID subfield532is the same as or similar to the STAID subfield702-4described above with respect toFIG. 7A. The feedback control information subfield534indicates feedback information such as a feedback type, a beamforming bandwidth (e.g., a bandwidth of the beamforming training packet that follows the announcement frame500), an Nc index that indicates a number of columns in a feedback matrix to be provided by the corresponding client station25to the AP14, etc., in an embodiment.

In an embodiment in which a legacy client station is a participant in the beamforming training, such as the embodiment described above with reference toFIG. 4, the legacy client station is configured to automatically transmit feedback after reception of a beamforming training packet, such as the beamforming training packet204, if the legacy client station is identified by the per-STA information subfield530-2corresponding to STA0. For example, the legacy communication protocol according to which the legacy client station is configured to operate specifies that the client station that is identified as STA0in a beamforming announcement frame should automatically transmit its feedback upon expiration of a predetermined time interval (e.g., SIFS) after reception of a beamforming training packet that follows the beamforming announcement frame, in an embodiment. In an embodiment, the AP14is configured to suppress automatic transmission of feedback by the legacy client station to avoid collision of the feedback with the trigger frame206. For example, the AP14is configured to set the per-STA information subfield530-2corresponding to STA0to a reserved value (e.g., 0), or a value of an STAID that is not associated with any client station25in the WLAN10, in an embodiment.

FIG. 6is a flow diagram of an example method600for beamforming training in a wireless communication network, according to an embodiment. In some embodiments, the method600is implemented by the AP14(FIG. 1). For example, in some embodiments, the network interface device16(e.g., the PHY processor20and/or the MAC processor18) is configured to implement the method600. In other embodiments, another suitable network interface device is configured to implement the method600.

At block602, a beamforming training packet is transmitted to multiple communication devices. In an embodiment, the beamforming training packet204ofFIGS. 2, 3, 4is transmitted. In another embodiment, another suitable beamforming training packet is transmitted. In an embodiment, the beamforming training packet includes one or more training fields that allow the multiple communication devices to obtain measures of respective communication channels associated with the communication devices.

At block604, a trigger frame is generated. In an embodiment, the trigger frame206ofFIGS. 2, 3, 4, is generated. In another embodiment, another suitable trigger frame is generated. In an embodiment, the trigger frame is generated to trigger an uplink OFDMA transmission from at least some of the multiple communication devices. In an embodiment, the trigger frame includes information to indicate respective frequency portions of the uplink OFDMA transmission, the respective frequency portions corresponding with respective ones of the at least some of the multiple communication devices.

At block606, after the beamforming training packet is transmitted at block602, the trigger frame generated at block606is transmitted to the at least some of the multiple communication devices.

At block608, the uplink OFDMA transmission is received. In an embodiment, the uplink OFDMA transmission includes respective beamforming training feedback packets from respective ones of the at least some of the multiple communication devices. In an embodiment, the respective beamforming training feedback packets are simultaneously transmitted by the at least some of the multiple communication devices. In an embodiment, the respective beamforming feedback packets are transmitted, by the at least some of the multiple communication device, in the respective frequency portions corresponding with the at least some of the multiple communication devices.

In an embodiment, each of the multiple communication devices receives the beamforming training packet transmitted at block602, and generates beamforming feedback based on the received beamforming training packet. Each of the at least some of the multiple communication devices being triggered by the trigger frame transmitted at block606receives the trigger frame and determines, based on the received trigger frame, that the communication device is being triggered to transmit the feedback generated based on the beamforming training packet transmitted at block602, in an embodiment. In response to receiving the trigger frame, each of the at least some of the multiple communication devices transmits the feedback generated based on the beamforming training packet transmitted at block602, in an embodiment. In an embodiment, because the trigger frame is transmitted at block606after the beamforming training packet is transmitted at block602, each of the at least some multiple communication devices that is to transmit the feedback in response to receiving the trigger frame at block606has sufficient amount of time to generate the feedback based on the beamforming training packet transmitted at block602and to transmit the feedback upon expiration of a relatively short time interval after receiving the trigger frame transmitted at block606. For example, each of the at least some of the multiple communication devices transmits the feedback upon expiration of a time interval corresponding to SIFS after receiving the trigger frame, in an embodiment.

In an embodiment, a method for beamforming training in a wireless communication network includes transmitting, from a first communication device, a beamforming training packet to multiple second communication devices. The method also includes generating, at the first communication device, a trigger frame to trigger an uplink orthogonal frequency division multiple access (OFDMA) transmission of beamforming training feedback from at least some of the multiple second communication devices. The method further includes transmitting, with the first communication device and after transmission of the beamforming training packet by the first communication device, the trigger frame to the at least some of the multiple communication devices. The method additionally includes receiving, at the first communication device, the uplink OFDMA transmission, wherein the uplink OFDMA transmission includes respective beamforming training feedback packets generated based on the beamforming training packet by respective ones of the at least some of the multiple second communication devices, and wherein the respective beamforming training feedback packets are simultaneously transmitted by the at least some of the multiple second communication devices.

In other embodiments, the method includes any suitable combination of one or more of the following features.

Transmitting the trigger frame comprises transmitting the trigger frame upon expiration of a first predetermined time interval after transmission of the beamforming training packet.

The first predetermined time interval corresponds to a short inter-frame spacing (SIFS) time interval.

The trigger frame causes the second communication devices to transmit the respective beamforming training feedback packets upon expiration of a second predetermined time interval after reception of the trigger frame by the second communication devices.

The second predetermined time interval corresponds to a short inter-frame spacing (SIFS) time interval.

The trigger frame includes information to indicate respective frequency portions of the uplink OFDMA transmission, the respective frequency portions corresponding with respective ones of the at least some of the multiple second communication devices.

The respective beamforming training feedback packets simultaneously transmitted by the least some of the multiple second communication devices are transmitted in the respective frequency portions corresponding with the at least some of the multiple second communication devices.

The method further comprises, prior to transmitting the beamforming packet, transmitting, with the first communication device, an announcement frame to the multiple second communication devices, wherein the announcement frame identifies the multiple second communication devices.

The announcement frame occupies an entire bandwidth of the communication channel.

The announcement frame is duplicated in each of a plurality of subchannels of the communication channel.

The multiple second communication devices include a legacy communication device that is not configured for OFDMA communication.

The method further comprises, after receiving the uplink OFDMA transmission, transmitting a polling frame to trigger transmission of feedback from the legacy communication device.

The method further comprises including, in the announcement frame, an indication to suppress automatic feedback by the legacy second communication device.

In another embodiment, an apparatus comprises a network interface device having one or more integrated circuits configured to transmit a beamforming training packet to multiple communication devices. The one or more integrated circuits are also configured to generate a trigger frame to trigger an uplink orthogonal frequency division multiple access (OFDMA) transmission of beamforming training feedback from at least some of the multiple communication devices. The one or more integrated circuits are further configured to, after transmission of the beamforming training, transmit the trigger frame to the at least some of the multiple communication devices. The one or more integrated circuits are additionally configured to receive the uplink OFDMA transmission, wherein the uplink OFDMA transmission includes respective beamforming training feedback packets generated based on the beamforming training packet by respective ones of the at least some of the multiple communication devices, and wherein the respective beamforming training feedback packets are simultaneously transmitted by the at least some of the multiple communication devices.

In other embodiments, the apparatus includes any suitable combination of one or more of the following features.

The one or more integrated circuits are configured to transmit the trigger frame upon expiration of a first predetermined time interval after transmission of the beamforming training packet.

The first predetermined time interval corresponds to a short inter-frame spacing (SIFS) time interval.

The trigger frame causes the second communication devices to transmit the respective beamforming training feedback packets upon expiration of a second predetermined time interval after reception of the trigger frame by the multiple communication devices.

The second predetermined time interval corresponds to a short inter-frame spacing (SIFS) time interval.

The trigger frame includes information to indicate respective frequency portions of the uplink OFDMA transmission, the respective frequency portions corresponding with respective ones of the at least some of the multiple communication devices.

The respective beamforming training feedback packets simultaneously transmitted by the least some of the multiple communication devices are transmitted in the respective frequency portions corresponding with the at least some of the multiple communication devices.

The one or more integrated circuits are further configured to, prior to transmitting the beamforming packet, transmit an announcement frame to the multiple communication devices, wherein the announcement frame identifies the multiple communication devices.

The announcement frame occupies an entire bandwidth of the communication channel.

The announcement frame is duplicated in each of a plurality of subchannels of the communication channel.

The multiple communication devices include a legacy communication device that is not configured for OFDMA communication, and wherein the method further comprises, after receiving the uplink OFDMA transmission, transmitting a polling frame to trigger transmission of feedback from the legacy communication device.

The one or more integrated circuits are further configured to include in the announcement frame an indication to suppress automatic feedback by the legacy second communication device.

At least some of the various blocks, operations, and techniques described above may be implemented utilizing hardware, a processor executing firmware instructions, a processor executing software instructions, or any combination thereof. When implemented utilizing a processor executing software or firmware instructions, the software or firmware instructions may be stored in any computer readable memory such as on a magnetic disk, an optical disk, or other storage medium, in a RAM or ROM or flash memory, processor, hard disk drive, optical disk drive, tape drive, etc. The software or firmware instructions may include machine readable instructions that, when executed by one or more processors, cause the one or more processors to perform various acts.