Implicit channel tracking for simultaneous multi-user transmissions

Abstract

Embodiments of the present disclosure provide implicit channel tracking for simultaneous multi-user transmissions.Other embodiments are also described and claimed.

Description

Technical Field

[0001] Embodiments of the present invention generally relate to the technical field of wireless communications. Background Art

[0002] The Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard is expected to support efficient transmission of multi-user (MU) and single-user (SU) beamforming switches to signal different link conditions and quality of service (QoS) characteristics to a large number of stations.

[0003] Multi-User - Multiple Input Multiple Output (MU-MIMO) requires an accurate estimate of the channel from the access point transmitter to the user receiver. See, for example, IEEE 802.11ac-2013 - IEEE Standard for Information Technology - Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks - Specific Requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications - Amendment 4: Enhancements for Ultra-High Throughput in Bands Below 6 GHz (hereinafter referred to as "IEEE 802.11ac"). The transmitter needs this estimate of the channel to select weighting factors to reduce mutual interference between different user streams. Currently, channel knowledge is explicitly obtained from the user's receiver. This channel acquisition process has a high throughput overhead. In addition, the channel may change after a short period of time, which can increase mutual interference between users and deteriorate user reception.

[0004] To overcome the channel variation problem, some systems will allow the transmitter to explicitly acquire the wireless channel more frequently. However, these systems will increase the high overhead of the associated channel acquisition and thus impair system efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The embodiments will be easily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, the same reference numerals represent the same structural elements. The embodiments are illustrated in the accompanying drawings by way of example and not limitation.

[0006] Figure 1 A network according to some embodiments is shown.

[0007] Figure 2 A transmission diagram according to some embodiments is shown.

[0008] Figure 3A-3B An efficient package according to some embodiments is shown.

[0009] Figure 4 A signal processing circuit according to some embodiments is shown.

[0010] Figure 5 An operation flow / algorithm structure according to some embodiments is shown.

[0011] Figure 6 An operation flow / algorithm structure according to some embodiments is shown.

[0012] Figure 7 An operation flow / algorithm structure according to some embodiments is shown.

[0013] Figure 8 Example apparatus according to various embodiments are shown.

[0014] Fig. 9 is a block diagram illustrating components capable of reading instructions from a machine-readable or computer-readable medium (eg, a non-transitory machine-readable storage medium) and performing any one or more of the methodologies discussed herein, according to some example embodiments. DETAILED DESCRIPTION

[0015] The following detailed description refers to the accompanying drawings. The same reference numerals may be used in different drawings to identify the same or similar elements. In the following description, for the purpose of explanation rather than limitation, specific details such as specific structures, architectures, interfaces, technologies, etc. are set forth in order to provide a thorough understanding of various aspects of various embodiments. However, it is apparent to those skilled in the art who benefit from this disclosure that various aspects of the various embodiments may be implemented in other examples that depart from these specific details.

[0016] In some cases, descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the various embodiments with unnecessary detail.For purposes of this document, the phrases "A or B" and "A / B" mean (A), (B), or (A and B).

[0017] Figure 1A network 100 according to some embodiments is shown. The network 100 may include an AP 104, which is communicatively coupled to a plurality of stations (STAs) including, for example, STA A 108, STA B 112, STA C 116, and STA D 120. The network 100 may be a wireless local area network (WLAN) compatible with the IEEE 802.11 protocol. In some embodiments, the network 100 may also be referred to as a basic service set (BSS). In some embodiments, the AP 104 and the STAs may communicate based on, for example, the High Efficiency Wireless (HEW) protocol defined in the February 2019 IEEE 802.11ax D4.0-IEEE Draft Standard for Information Technology-Telecommunications and Information Exchange between System Local Area Networks and Metropolitan Area Networks-Specific Requirements Part 11: Enhancements to Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment for High Efficiency WLAN (hereinafter referred to as "IEEE 802.11ax"). STAs operating based on the High Efficiency Wireless (HEW) protocol may also be referred to as HEW or High Efficiency (HE) STAs.

[0018] In some embodiments, AP 104 may generate transmissions to multiple STAs of the network by multiplexing the transmissions in the frequency domain. AP 104 may include transmissions to multiple users in a multi-user packet, such as a MU High Efficiency - Physical Layer Convergence Procedure Protocol Data Unit (HE-PPDU) sent in a downlink transmission.

[0019] As briefly described above, multi-user / single-user (SU) beamforming relies on channel knowledge for selecting the weight vectors of the beamforming matrix. This channel knowledge can be obtained explicitly, for example, the receiver can measure the channel and send the channel information back to the transmitter. The wireless channel may change in a very short period of time, and as the channel knowledge ages, it becomes increasingly irrelevant. Relying on older channel knowledge may reduce throughput. The reduction in throughput is particularly significant in multi-user situations, where outdated channel knowledge can result in significantly increased mutual interference detected by stations. However, the need for frequent channel feedback can impose significant overhead. Embodiments of the present disclosure improve performance by tracking changes in the channel without relying on substantial channel feedback overhead.

[0020] Some embodiments provide implicit channel tracking for simultaneous multi-user transmissions. Embodiments may use differential measurements between consecutive transmissions in order to track changes in the channel (including interference) and may adapt transmission / reception parameters accordingly. The transmitter may use raw channel knowledge and information gleaned from transmissions returned from the receiver to implicitly update channel information without recalibrating the transmitter or receiver.

[0021] In some embodiments, the transmitter can use channel reciprocity and estimate channel changes based on the transmission returned from the receiver and the original channel knowledge. The returned transmission may include, but is not limited to, multi-user uplink confirmation information, multi-user uplink data, etc. The transmitter can use differential channel estimation to modify transmission / reception parameters (e.g., coding rate, transmit power allocation, beamforming matrix, etc.) for subsequent transmissions.

[0022] The AP 104 may use the channel information obtained from the sounding operation to accurately determine a first beamforming matrix, which is used to send a first MU packet to STA AD when STA AD is in a first position. STA AD may move to a different position (shown by a dotted line), and the AP 104 may implicitly update the channel information using subsequent uplink transmissions from STA AD at its new position. The AP 104 may then use the updated channel information to determine an updated second beamforming matrix, which may then be used to send a second MU packet to STA AD when STA AD is in a second position. This operation may be done without relying on other sounding operations (in UL or DL), and may also be done without recalibrating the receiver.

[0023] Although the movement of STA AD may be one reason for the channel change, the channel may also change due to a variety of other reasons. Regardless of the reason for the channel change, the embodiments of the present disclosure are equally applicable.

[0024] Figure 2 A transmission diagram 200 is shown in accordance with some embodiments. The transmission diagram 200 may describe messages and operations performed by the AP 104 and the station 204. The station 204 may include Figure 1 The STA ADs are similar and essentially interchangeable stations.

[0025] In some embodiments, the AP 204 may perform a sounding operation 208 to acquire a downlink channel for a transmission opportunity (TXOP) period. To perform the sounding operation 208, the AP 104 may send a null data packet announcement (NDPA) 212 to the station 204 and subsequently send a null data packet (NDP) to the station 204. The station 204 may measure the NDP and generate feedback information, which is sent to the AP 204 in a MU beamforming report 220. In various embodiments, the feedback information may include channel metrics, such as an indication of a weight vector to be used in a beamforming matrix and a signal-to-noise ratio (SNR) for different subcarriers. Subcarriers may also be referred to as "tones."

[0026] The AP 104 may determine a first beamforming (BF_1) matrix based on the feedback information. In some embodiments, the AP 104 may also determine many other transmission parameters related to downlink multi-user transmission. These other transmission parameters may include, for example, users / stations within a MU OFDMA group, resource unit (RU) allocations, modulation and coding schemes (MCS), and transmit power allocations.

[0027] At 228, the AP 104 may also determine reference channel values ​​based on the MU beamforming report 220. The determination of the reference channel values ​​may be performed by a receive chain decoding preamble of the MU beamforming report 220. These reference channel values ​​may provide information on the state of the uplink channel on which the MU beamforming report 220 is sent.

[0028] At 232, the AP 104 may correlate the reference channel values ​​with the BF_1 matrix. Although the BF_1 matrix is ​​generated based on the state of the downlink channel on which the NDPA / NDP message is sent, the temporal proximity of the NDP / beamforming reports may be sufficient to assume reciprocity between the uplink and downlink channels, thus supporting correlation of the reference channel values ​​with the BF_1 matrix.

[0029] The AP 104 may construct a MU packet based on the determined transmission parameters and may send the MU packet in a downlink transmission with the BF_1 matrix 236 .

[0030] STA 204 may send uplink transmissions at 240. These uplink transmissions may include acknowledgment information corresponding to the data sent in the MU packet at 236. Additionally or alternatively, the uplink transmissions may include uplink data.

[0031] At 244, the AP 104 may determine updated channel values ​​and calculate a second beamforming (BF_2) matrix. The updated channel values ​​may be performed by a receive chain decoding preamble of the uplink transmission sent at 240 and may provide information about the state of the uplink channel when the UL transmission is sent at 240. The AP 104 may infer changes in channel values ​​between reference channel values, and the updated channel values ​​may correspond to corresponding changes in the beamforming matrix. Thus, the BF_2 matrix may be calculated based on the BF_1 matrix and the relative changes between the updated channel values ​​and the reference channel values.

[0032] The AP 104 may construct a second multi-user group at 248 and transmit the second multi-user group in a downlink transmission with the BF_2 matrix. In some embodiments, the construction of the second multi-user group may be performed using a number of transmission parameters determined based on the sounding operation 208, including but not limited to users / stations within the MU OFDMA group, resource unit (RU) allocation, MCS, and transmit power allocation. However, in some embodiments, one or more of these parameters may also be updated based on a relative change between the updated channel value and the reference channel value.

[0033] Implicit channel updates as described herein may enable a transmitter to transmit for longer durations. For example, a transmission opportunity duration may be extended for a specific set of stations. This may be accomplished, for example, by requiring a user to resend channel information without explicitly acquiring the channel again. Embodiments may improve throughput by reducing protocol complexity and overhead; increasing downlink (DL) / uplink (UL) MU-MIMO throughput; or improving the accuracy of rate tracking by responding more quickly to channel changes.

[0034] The description of transmission diagram 200 is based on the assumption that the AP is performing implicit channel tracking. However, other embodiments may include stations that perform implicit channel tracking. In such embodiments, the sounding operation may be an uplink sounding operation, and the uplink / downlink portions may be reversed. For example, instead of implicitly tracking changes in the DL channel based on changes in the UL channel, changes in the UL channel may be implicitly tracked based on changes in the DL channel.

[0035] Figure 3A FIG. 3 shows a multi-user packet 300 that may be generated by AP 104 and sent in a downlink transmission, such as in FIG. Figure 2 The transmission at 228 or 248 is described.

[0036] In some embodiments, the multi-user packet 300 may be referred to as a MU HE-PPDU. The multi-user packet 300 may include a legacy preamble 304, a high efficiency (HE) preamble 308, and a data portion 312. The legacy preamble 304 and the HE preamble 308 may span a channel bandwidth. In some embodiments, the channel bandwidth may be 20 megahertz (MHz), 40 MHz, 80 MHz, 80+80 MHz, or 160 MHz.

[0037] The legacy preamble 304 may be used for backward compatibility and may be decoded by a legacy station. The legacy preamble 304 may include training fields, such as a legacy-short training field (L-STF) and a legacy-long training field (L-LTF), to synchronize the transmitter and the receiver. The legacy preamble 304 may further include a legacy signal field (L-SIG) to allow the receiving station to determine the transmission time of the multi-user packet. In some embodiments, the L-SIG field may have a length indicating that the packet is a HE packet with a MU preamble.

[0038] The HE preamble 308 may include a repeated legacy-signal field (RL-SIG) 316, a HE signal-A field (HE-SIG-A) 320, a HE signal-B field (HE-SIG-B) 324, and one or more training fields, such as a HE-STF 328 or a HE-LTF 332.

[0039] RL-SIG 316 may facilitate detection by providing a duplicate / L-SIG validity check.

[0040] The HE-SIG-A 320 may include common transmission parameters for users having data within the data portion 312 of the multi-user packet 300. In some embodiments, the HE-SIG-A 320 may provide information about the MCS, bandwidth, number of spatial streams, and other parameter information to allow a receiver to correctly decode the multi-user packet 300. The HE-SIG-A 320 may provide information about network color, remaining TxOP duration, whether the frame is UL or DL, and the like.

[0041] The HE-SIG-B field may include RU allocation information and per-user signaling parameters for users having data in the data portion 314. The per-user signaling parameters may include MCS per resource unit, number of streams, and the like.

[0042] HE-STF 328 and HE-LTF 332 may be used to tune a transmitter / receiver for MIMO transmissions. HE-STF 328 may be used to improve automatic gain control estimation in MIMO transmissions, and HE-LTF 332 may allow a receiver to estimate a MIMO channel between a set of constellation mapper outputs and a receive chain.

[0043] The data portion 312 may include RUs of stations assigned to the OFDMA group. In this embodiment, the OFDMA group determined by the AP 104 may include Figure 1For example, STA A 108 may be allocated RU_A 336, STA B 112 may be allocated RU_B 340, STA C 116 may be allocated RU_C 344, and STA D 120 may be allocated RU_D 348.

[0044] Figure 3B It is shown that a signal may be generated by a station and transmitted in an uplink, e.g. Figure 2 During the transmission at 232 or 240, packet 352 is sent.

[0045] Packet 352 may include legacy preamble 356, HE preamble 360, and data portion 364. HE preamble 360 ​​may include RL-SIG 368, HE-SIG A 372, HE-STF 376, and HE-LTF 380. In general, the fields within packet 352 may be similar to the fields of the same name described with respect to multi-user packet 300. Data portion 364 may include acknowledgment information or uplink data.

[0046] In some embodiments, the receiver of AP 104 may use HE-LTF 380 as a basis for determining a reference channel value at 228 and an updated channel value at 244.

[0047] Figure 4 A signal processing circuit 400 is shown in accordance with some embodiments. According to some embodiments, the signal processing circuit 400 may be included in the AP 104 or a station.

[0048] Signal processing circuit 400 may include control circuit 404 including processor / memory circuits to execute elements of a protocol stack including, for example, physical (PHY) and medium access control (MAC) layer functions. Control circuit 404 may be coupled to receive circuit 408 and transmit circuit 412.

[0049] As used herein, the term "circuit" may refer to a hardware component configured to provide the above-mentioned functions, such as an electronic circuit, a logic circuit, a processor (shared, dedicated or group) and / or a memory (shared, dedicated or group), an application-specific integrated circuit (ASIC), a field programmable device (FPD) (e.g., a field programmable gate array (FPGA), a programmable logic device (PLD), a complex PLD (CPLD), a high-capacity PLD (HCPLD), a structured ASIC or a programmable SoC), a digital signal processor (DSP), etc., a part thereof, or including the above-mentioned hardware components. In some embodiments, the circuit may execute one or more software or firmware programs to provide at least some of the functions described. In addition, the term "circuit" may also refer to a combination of one or more hardware elements (or a combination of circuits used in an electrical or electronic system) and a program code for executing the functions of the program code. In these embodiments, the combination of hardware elements and program code may be referred to as a specific type of circuit.

[0050] The receive circuit 408 may include analog / digital components designed to extract control / data from the signals received by the signal processing circuit 400. These components may include, but are not limited to, decoders, demodulators, filters, low noise amplifiers (LNAs), switches, receive beamforming circuits, processing circuits, etc.

[0051] Receive circuit 408 may be coupled to receive controller 422 of control circuit 404. Receive controller 422 may include feedback / channel analyzer 418 and memory 424 for storing receive parameters 426. In some embodiments, receive circuit 408 and receive controller 422 may be collectively referred to as a "receiver."

[0052] The receive parameters 426 may configure the components of the receive circuit 408 to be in a first receive state for receiving a signal. For example, the receive parameters 426 may set the gain of a low noise amplifier (LNA), provide a receive beamforming matrix for a beamforming component of the receive circuit 408, and so on.

[0053] The feedback / channel analyzer 418 may extract feedback information from the received signal from the receive circuit 408. For example, the signal received by the feedback / channel analyzer 418 may be a beamforming report, such as the MU beamforming report 220, which may include feedback information including information regarding the state of the channel over which the corresponding sounding signal was sent.

[0054] Feedback / channel analyzer 418 may provide feedback information to transmit controller 430. Transmit controller 430 may determine transmit parameters 434 and store them in memory 436. Transmit parameters 434 may be used to configure transmit circuitry 412 for signal transmission. In some embodiments, transmit parameters 434 may include users / stations within a MU OFDMA group, RU allocation, MCS, transmit power allocation, and beamforming matrix.

[0055] The transmit controller 430 may include a digital beamforming block (DBF) 438 that employs a digital signal processing algorithm to process the channel information and calculate a beamforming matrix stored in the transmit parameters 434. The channel information may include explicit channel information (e.g., information about a channel acquired through a sounding operation) or implicit channel information (e.g., information about changes in channel values ​​corresponding to a reversible channel). The beamforming matrix may be provided to a beamforming component in the transmit circuit 412. The beamforming component may apply the beamforming matrix to the transmitted signal to improve reception at a designated receiver. This may be achieved by combining elements in a phased antenna array in a manner that exploits constructive and destructive signal interference experienced by the receiver.

[0056] In addition to the beamforming components, the transmit circuitry 412 may include additional analog / digital components (e.g., encoders, modulators, mappers, filters, power amplifiers, switches, processing circuits, etc.) to generate and transmit signals. In some embodiments, the transmit circuitry 412 and the transmit controller 430 may be collectively referred to as a "transmitter."

[0057] The feedback / channel analyzer 418 may additionally / alternatively determine a channel value indicating a state of a channel on which an AP / STA implementing the signal processing circuit 400 receives a signal. The signal may include, for example, a MU beamforming report 220 or a UL transmission 240. In some embodiments, the feedback / channel analyzer 418 may decode a preamble of a received signal (e.g., a HE-LTF field of an uplink packet) to determine a channel value, which may include a reference channel value or an updated channel value, as described herein.

[0058] The receive controller 422 may provide the channel values ​​determined by the feedback / channel analyzer 418 to the tracking manager 442. The tracking manager 442 may include an implicit channel difference analyzer (ICDA) 446. The ICDA 446 may compare the updated channel values ​​with the reference channel values ​​to determine a change in the state of the channel. The ICDA 446 may provide an indication of the change in the channel state as channel information to the transmit controller 430. The DBF 438 may then update the beamforming matrix within the transmit parameters 434 to reflect the estimate of the changed channel.

[0059] Figure 5 An operation flow / algorithm structure 500 according to some embodiments is shown. The operation flow / algorithm structure 500 may be implemented by an access point (e.g., access point 104) or a component thereof (e.g., signal processing circuit 400). In some embodiments, the operation flow / algorithm structure 500 may be modified to be performed by a STA or a component thereof.

[0060] At 504, the operation flow / algorithm structure 504 may include calculating the BF_1 matrix based on the feedback information. The feedback information may be obtained when acquiring the channel. For example, the feedback information may include the beamforming vector and SNR sent by STA AD in the MU beamforming report 220.

[0061] At 508, the operational flow / algorithm structure 500 may further include transmitting the first multi-user packet using the BF_1 matrix. In some embodiments, the transmission of the first multi-user packet using the BF_1 matrix may include DBF that controls a beamforming component in the transmit chain to provide directional transmission to stations having data in the first multi-user packet.

[0062] At 512, the operational flow / algorithm structure 500 may further include receiving an uplink transmission. The receiver of the access point may receive and process the uplink transmission as described herein. The uplink transmission received at 512 may include a first uplink transmission, which may be used as a basis for determining a reference channel value. In some embodiments, the receiver may determine the reference channel value by decoding / measuring a preamble of the first uplink transmission. The first uplink transmission may be a transmission sent during a sounding operation (e.g., a MU beamforming report 220) or other UL transmission including, for example, data or confirmation information. The reference channel value may correspond to a first state of an uplink channel on which the first uplink transmission is sent.

[0063] The uplink transmission received at 512 may further include a second uplink transmission, which may be received after a time period has passed since the first uplink transmission was received. The second uplink transmission may be used as a basis for determining an updated channel value. The receiver may determine the updated channel value in a manner similar to that described above with respect to the reference channel value. The second uplink transmission may include data or confirmation information. The updated channel value may correspond to a second state of the uplink channel on which the second uplink transmission is sent.

[0064] At 516, the operational flow / algorithm structure 500 can further include calculating a BF_2 matrix based on the uplink transmission. The calculation of the BF_2 matrix can be based on the change in channel values ​​determined from the received uplink transmission at 512. In particular, the access point can infer that a change in the uplink channel (determined by comparing the updated channel value to the reference channel value) can correspond to a similar change in the downlink channel. The access point can then use this change in the downlink channel as a basis for updating the beamforming matrix from the BF_1 matrix to the BF_2 matrix.

[0065] At 520, the operational flow / algorithm structure 500 may further include transmitting a second multi-user packet using the BF_2 matrix. In some embodiments, the transmission of the second multi-user packet using the BF_2 matrix may include a DBF that controls a beamforming component in the transmit chain to provide directional transmission to a station having data in the second multi-user packet.

[0066] Figure 6 An operation flow / algorithm structure 600 according to some embodiments is shown. The operation flow / algorithm structure 600 may be implemented by an access point (e.g., access point 104) or a component thereof (e.g., signal processing circuit 400). In some embodiments, the operation flow / algorithm structure 600 may be modified to be performed by a STA or a component thereof.

[0067] At 604, the operational flow / algorithm structure 604 may include storing first channel information in a memory. In some embodiments, the first channel information may include a channel metric obtained from feedback information sent during a sounding operation for acquiring a downlink channel for a transmission opportunity. In some embodiments, the first channel information may include a weight vector, SNR information, etc.

[0068] At 608, the operational flow / algorithm structure 600 may further include sending a first multi-user packet based on the first channel information. In some embodiments, the first channel information may be used as a basis for determining first transmission parameters including a first beamforming matrix, a coding rate, etc. The first transmission parameters may then be used to complete the transmission of the first multi-user packet.

[0069] At 612, the operational flow / algorithm structure 600 may further include receiving uplink transmissions. The uplink transmissions may include a first uplink transmission and a second uplink transmission from a station including the station to which the first multi-user packet is sent. In some embodiments, receiving the uplink transmissions may be performed by setting a component of the receive chain to be in a first receive state to receive both the first and second uplink transmissions. For example, when the access point receives the first and second uplink transmissions, the receive controller 422 may set the receive parameters 426 to be the same. Therefore, the receiver may not be recalibrated between the reception of the uplink transmissions.

[0070] At 616, the operational flow / algorithm structure 600 may further include storing the second channel information in a memory. In some embodiments, the second channel information may be determined based on an uplink transmission.

[0071] The second channel information can be determined by the access point implicitly tracking the downlink channel based on the uplink channel state change. The uplink channel state change can be determined based on the first / second uplink transmission. For example, the access point can determine the first UL channel state based on the first uplink transmission, and can determine the second UL channel state based on the second uplink transmission. The access point can then determine the uplink channel state change based on the first and second UL channel states. The access point can infer the reciprocity between the first UL channel state and the DL channel state, and can further infer the reciprocity between the second UL channel state and the DL channel state. Therefore, the access point can infer a DL channel state change similar to the UL channel state change. The access point can then determine the second channel information based on the DL channel state change and the first channel information.

[0072] At 620, the operational flow / algorithm structure 600 may further include sending a second multi-user packet based on the second channel information. In some embodiments, the second channel information may be used as a basis for determining second transmission parameters including a second beamforming matrix, a coding rate, etc. The second transmission parameters may then be used to complete the transmission of the second multi-user packet.

[0073] Figure 7 An operation flow / algorithm structure 700 according to some embodiments is shown. The operation flow / algorithm structure 700 may be implemented by an access point (e.g., access point 104) or a component thereof (e.g., signal processing circuit 400). In some embodiments, the operation flow / algorithm structure 700 may be modified to be performed by a STA or a component thereof.

[0074] At 704, the operational flow / algorithm structure 704 may include acquiring a downlink channel. Acquisition of the downlink channel may be achieved by performing a sounding operation. The sounding operation may include sending an NPD packet and receiving feedback information in an MU beamforming report. The feedback information may include information from the stations based on their reception of the NPD packet. The information may provide an indication of the first DL channel state.

[0075] At 708, the operational flow / algorithm structure 700 may further include determining a BF_1 matrix based on the first DL channel state. In some embodiments, information received from the station during the sounding operation may include a weight vector that may form the BF_1 matrix.

[0076] At 712, the operational flow / algorithm structure 700 may further include generating and transmitting a first MU packet using the BF_1 matrix. In some embodiments, the transmission of the first MU packet using the BF_1 matrix may include a DBF that controls a beamforming component in a transmit chain to provide directional transmission to a station having data in the first MU packet.

[0077] At 716, the operational flow / algorithm structure 700 may further include determining a change in the state of the uplink channel and the second downlink channel. In some embodiments, the change in the uplink channel may be determined based on receiving a plurality of uplink transmissions from a station in the network. The first uplink transmission from the station may be measured by a receiver in the access point to establish a reference channel state. The access point may receive the first uplink transmission as part of a sounding operation or after a sounding operation. The second uplink transmission from the station may be measured by a receiver in the access point to establish an updated channel state. The change in the uplink channel may be determined by comparing the updated channel state with the reference channel state.

[0078] When determining a change in the uplink channel, the access point may determine a second downlink channel state by inferring a corresponding change in the downlink channel with reference to the first DL channel state.

[0079] At 720, the operational flow / algorithm structure 700 may further include determining a BF_2 matrix based on the second DL channel state. In some embodiments, the BF_2 matrix may be generated using a weight vector that is more suitable for the second DL channel state.

[0080] At 724, the operational flow / algorithm structure 700 may further include generating and transmitting a second multi-user packet using the BF_2 matrix. In some embodiments, the transmission of the second MU packet using the BF_2 matrix may include a DBF that controls a beamforming component in the transmit chain to provide directional transmission to a station having data in the second MU packet. In this way, the access point can change the direction of the transmission beam to more accurately target a station that may have moved since the sounding operation occurred.

[0081] Figure 8 An example of an apparatus 800 according to various embodiments is shown. The apparatus 800 may be an AP (eg, AP104) or a STA (eg, Figure 1 The apparatus 800 may include one or more of an application circuit 805, a baseband circuit 810, one or more radio front-end modules 815, a memory circuit 820, a power management integrated circuit (PMIC) 825, and a network controller circuit 835.

[0082] The terms "application circuitry" and / or "baseband circuitry" may be considered synonymous with "processor circuitry" and may be referred to as "processor circuitry". As used herein, the term "processor circuitry" may refer to, a portion of, or include a circuit capable of sequentially and automatically performing a series of arithmetic or logical operations or recording, storing, and / or transmitting digital data. The term "processor circuitry" may refer to one or more application processors, one or more baseband processors, a physical central processing unit (CPU), a single-core processor, a dual-core processor, a triple-core processor, a quad-core processor, and / or any other device capable of executing or otherwise running computer-executable instructions (such as program code, software modules, and / or functional processes).

[0083] The application circuit 805 may include one or more central processing unit (CPU) cores, as well as cache, low dropout regulator (LDO), interrupt controller, serial interface such as SPI, I2C or general programmable serial interface module, real-time clock (RTC), timer including interval timer and watchdog timer, general input / output (I / O or IO), memory card controller such as secure digital (SD) multimedia card (MMC) or similar products, universal serial bus (USB) interface, mobile industry processor interface (MIPI) interface and joint test access group (JTAG) test access port. As an example, the application circuit 805 may include one or more Intel or Processor; Advanced Micro Devices (AMD) Processor, Accelerated Processing Unit (APU) or processor; etc. In some embodiments, AP 84 may not utilize application circuitry 805, but may instead include a dedicated processor / controller to process, for example, IP data received from a network core.

[0084] Additionally or alternatively, the application circuit 805 may include circuits such as, but not limited to, one or more field programmable devices (FPDs), such as field programmable gate arrays (FPGAs), etc.; programmable logic devices (PLDs), such as complex PLDs (CPLDs), high capacity PLDs (HCPLDs), etc.; ASICs, such as structured ASICs, etc.; programmable SoCs (PSoCs); etc. In such embodiments, the circuits of the application circuit 805 may include logic blocks or logic structures, and other interconnected resources that may be programmed to perform various functions, such as the processes, methods, functions, etc. of the various embodiments discussed herein. In such embodiments, the circuits of the application circuit 805 may include storage units (e.g., erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, static memory (e.g., static random access memory) (SRAM), anti-fuses, etc.) for storing logic blocks, logic structures, data, etc. in a lookup table (LUT), etc.

[0085] The baseband circuit 810 can be implemented as, for example, a lower solder substrate including one or more integrated circuits, an integrated circuit of a single package soldered to a main circuit board, or a multi-chip module containing two or more integrated circuits. Although not shown, the baseband circuit 810 can include one or more digital baseband systems, which can be coupled to the CPU subsystem, the audio subsystem, and the interface subsystem via an interconnect subsystem. The digital baseband subsystem can also be coupled to a digital baseband interface and a mixed signal baseband subsystem via another interconnect subsystem. Each interconnect subsystem can include a bus system, a point-to-point connection, a network on chip (NOC) structure, and / or some other suitable bus or interconnect technology, such as those discussed herein. The audio subsystem can include a digital signal processing circuit, a buffer memory, a program memory, a voice processing accelerator circuit, a data converter circuit (such as an analog-to-digital and digital-to-analog converter circuit), an analog circuit including one or more amplifiers and filters and / or other similar components. In one aspect of the present disclosure, the baseband circuit 810 may include a protocol processing circuit (e.g., the signal processing circuit 400) having one or more instances of a control circuit (not shown) to provide control functionality for the digital baseband circuit and / or the radio frequency circuit (e.g., the radio front end module 815).

[0086] The radio front end module (RFEM) 815 may include a radio frequency integrated circuit (RFIC), amplifiers (eg, power amplifiers and low noise amplifiers), and antenna elements to enable over-the-air transmission. The RFEM 815 may include beamforming circuitry to improve transmission / reception directivity.

[0087] The memory circuit 820 may include one or more of the following: a volatile memory including a dynamic random access memory (DRAM) and / or a synchronous dynamic random access memory (SDRAM), and a non-volatile memory (NVM) including a high-speed electrically erasable memory (commonly referred to as a flash memory), a phase change random access memory (PRAM), a magnetoresistive random access memory (MRAM), etc., and may and The memory circuit 520 may be implemented as one or more of an integrated circuit in a solder-down package, a socket memory module, and a plug-in memory card.

[0088] PMIC 825 may include a voltage regulator, a surge protector, a power alarm detection circuit, and one or more backup power supplies such as a battery or capacitor. The power alarm detection circuit may detect one or more of insufficient voltage (brownout) and surge (overvoltage) conditions.

[0089] The network controller circuit 835 may provide connectivity to a network using a standard network interface protocol such as Ethernet, Ethernet over GRE tunnels, Ethernet over Multi-Protocol Label Switching (MPLS), or some other suitable protocol. Network connectivity may be provided to / from the device 800 using a physical connection, which may be electrical (commonly referred to as a "copper interconnect"), optical, or wireless. The network controller circuit 835 may include one or more dedicated processors and / or FPGAs to communicate using one or more of the above-described protocols. In some embodiments, the network controller circuit 835 may include multiple controllers to provide connectivity to other networks using the same or different protocols.

[0090] Figure 8The components shown can use interface circuits to communicate with each other. As used herein, the term "interface circuit" may refer to a circuit, a part of the circuit, or including the circuit that provides information exchange between two or more components or devices. The term "interface circuit" may refer to one or more hardware interfaces, such as a bus, an input / output (I / O) interface, a peripheral component interface, a network interface card, etc. Any suitable bus technology can be used in various embodiments, and these technologies can include many technologies, including industrial standard architecture (ISA), extended ISA (EISA), peripheral component interconnect (PCI), peripheral component interconnect extension (PCIx), PCI Express (PCIe) or many other technologies. The bus can be a dedicated bus, such as a bus used in a system based on SoC. Other bus systems can be included, such as I2C interface, SPI interface, point-to-point interface, and power bus, etc.

[0091] Fig. 9 A block diagram is provided to illustrate components capable of reading instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and executing any one or more of the methods discussed herein according to some example embodiments. Specifically, Fig. 9 A graphical representation of hardware resources 900 is shown including one or more processors (or processor cores) 910, one or more memory / storage devices 920, and one or more communication resources 930, each of which may be communicatively coupled via a bus 940. As used herein, the terms "computing resources," "hardware resources," and the like may refer to physical or virtual devices, physical or virtual components within a computing environment, and / or physical or virtual components within a particular device such as a computer device, a mechanical device, memory space, processor / CPU time and / or processor / CPU usage, processor and accelerator load, hardware time or usage, power, input / output operations, ports or network sockets, channel / link allocation, throughput, memory usage, storage, network, database, and application, etc. For embodiments utilizing node virtualization (e.g., NFV), a hypervisor 902 may be executed to provide an execution environment for one or more network slices / subslices to utilize hardware resources 900. "Virtual resources" may refer to computing, storage, and / or network resources provided by a virtualization infrastructure to an application, device, system, etc.

[0092] Processor 910 (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP) (such as a baseband processor), an application specific integrated circuit (ASIC), a radio frequency integrated circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, processor 1012 and processor 914.

[0093] The memory / storage device 920 may include a main memory, a disk storage device, or any suitable combination thereof. The memory / storage device 920 may include, but is not limited to, any type of volatile or non-volatile memory, such as a dynamic random access memory (DRAM), a static random access memory (SRAM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), flash memory, a solid-state storage device, etc.

[0094] The communication resources 930 may include interconnect or network interface components or other suitable means to communicate with one or more peripheral devices 904 or one or more databases 906 via the network 908. For example, the communication resources 1030 may include wired communication components (e.g., for coupling via a universal serial bus (USB)), cellular communication components, NFC components, Parts (e.g. Low power consumption), Components and other communication components. As used herein, the term "network resource" or "communication resource" may refer to a computing resource accessible to a computer device via a communication network. The term "system resource" may refer to any kind of shared entity that provides a service, and may include computing and / or network resources. System resources may be considered a set of coherent functions, network data objects, or services accessible through a server, where such system resources reside on a single host or multiple hosts and can be clearly identified.

[0095] The instructions 950 may include software, a program, an application, an applet, an app, or other executable code for causing at least any one of the processors 910 to perform any one or more of the methods discussed herein. For example, the instructions 950 may cause the one or more processors 910 to implicitly track a channel for updating a transmission during a transmission opportunity duration, as described herein.

[0096] The instructions 950 may reside, in whole or in part, within at least one of the processor 910 (e.g., within a cache of the processor), the memory / storage device 920, or any suitable combination thereof. In addition, any portion of the instructions 950 may be transferred to the hardware resources 900 from any combination of the peripheral device 904 or the database 906. Thus, the memory of the processor 910, the memory / storage device 920, the peripheral device 904, and the database 906 are examples of computer-readable and machine-readable media.

[0097] For one or more embodiments, at least one of the components described in one or more of the foregoing figures may be configured to perform one or more operations, techniques, processes and / or methods described in the following example section. For example, the baseband circuit as described above in conjunction with one or more of the foregoing figures may be configured to operate according to one or more examples described below. For another example, the circuit associated with the UE, base station, network element, etc. as described above in conjunction with one or more of the foregoing figures may be configured to operate according to one or more examples described below in the example section.

[0098] Example

[0099] Example 1 includes a method of operating an access point, the method comprising: calculating a first beamforming matrix based on feedback information received from a sounding operation; sending a first multi-user packet using the first beamforming matrix, the first multi-user packet including data to be sent to multiple stations in an orthogonal frequency division multiple access (OFDMA) group; receiving uplink transmissions from multiple stations; calculating a second beamforming matrix based on the uplink transmissions; and sending a second multi-user packet using the second beamforming matrix.

[0100] Example 2 may include the method of Example 1 or some other examples herein, wherein the uplink transmission includes confirmation information regarding the data within the first multi-user packet.

[0101] Example 3 may include the method of Example 1 or some other examples herein, wherein the method further includes performing a probing operation to acquire a channel for a transmission opportunity duration.

[0102] Example 4 may include the method of Example 3 or some other examples herein, wherein the sending the second multi-user packet is within a transmission opportunity duration.

[0103] Example 5 may include the method of Example 3 or some other examples herein, wherein the first beamforming matrix corresponds to a first state of the channel within a first portion of the transmission opportunity duration, and the second beamforming matrix corresponds to a second state of the channel within a second portion of the transmission opportunity duration.

[0104] Example 6 may include the method of Example 1 or some other examples herein, wherein the uplink transmission includes a first uplink transmission and a second uplink transmission, wherein calculating the second beamforming matrix includes: determining a reference channel value based on the first uplink transmission; determining an updated channel value based on the second uplink transmission; and calculating the second beamforming matrix based on the updated channel value.

[0105] Example 7 may include the method of Example 6 or some other examples herein, wherein the method further includes controlling the receive chain to receive the first uplink transmission and the second uplink transmission in a first receive state.

[0106] Example 8 may include the method of Example 6 or some other examples herein, further comprising: correlating the reference channel value with the first beamforming matrix; and further calculating the second beamforming matrix based on the correlation of the reference channel value with the first beamforming matrix.

[0107] Example 9 may include the method of Example 8 or some other examples herein, further comprising: calculating a second beamforming matrix based on an inference that a change from a reference channel value to an updated channel value corresponds to a change from a first beamforming matrix to a second beamforming matrix.

[0108] Example 10 may include a method comprising: storing first channel information based on feedback from multiple stations of a wireless local area network in response to one or more reference signals; sending a first multi-user packet to the multiple stations based on the first channel information; processing uplink transmissions received from the multiple stations; storing second channel information based on the uplink transmissions; and sending a second multi-user packet based on the second channel information, wherein the first channel information corresponds to a downlink channel within a first part of a transmission opportunity, and the second channel information corresponds to a downlink channel within a second part of the transmission opportunity.

[0109] Example 11 may include the method of Example 10 or some other examples herein, further comprising performing a probing operation to acquire a downlink channel for a transmission opportunity.

[0110] Example 12 may include the method of Example 10 or some other examples herein, wherein the uplink transmission includes user uplink data or includes confirmation information about the data sent in the first multi-user packet.

[0111] Example 13 may include the method of Example 10 or some other examples herein, wherein the uplink transmission includes a first uplink transmission and a second uplink transmission, and the method further includes: determining a first uplink (UL) channel state based on the first uplink transmission; determining a second UL channel state based on the second uplink transmission; determining a UL channel state change based on the first UL channel state and the second UL channel state; determining a downlink (DL) channel state change based on the UL channel state change; and determining second channel information based on the DL channel state change.

[0112] Example 14 may include the method of Example 13 or some other examples herein, further comprising setting a component of the receive chain in a first receive state to receive the first uplink transmission and the second uplink transmission.

[0113] Example 15 may include the method of Example 10 or some other examples herein, further comprising: generating a first transmission parameter based on the first channel information; and generating a second transmission parameter based on the second channel information.

[0114] Example 16 may include the method of Example 15 or some other examples herein, wherein the first transmission parameter comprises a first beamforming matrix or a coding rate, and the second transmission parameter comprises a second beamforming matrix or a coding rate.

[0115] Example 17 may include a method comprising: generating application data to be sent to multiple stations; acquiring a downlink channel for a transmission opportunity; determining a first beamforming matrix based on a first state of the downlink channel as indicated by feedback information in a multi-user beamforming report received during acquisition of the downlink channel; using the first beamforming matrix to generate a first multi-user packet to be sent; determining a change in the uplink channel based on multiple uplink transmissions; determining a second state of the downlink channel based on the change in the uplink channel; determining a second beamforming matrix based on the second state of the downlink channel; generating a second multi-user packet to be sent using the second beamforming matrix; and sending the first and second multi-user packets within the transmission opportunity.

[0116] Example 18 may include the method of Example 16 or some other examples herein, wherein the multiple uplink transmissions include a first uplink transmission and a second uplink transmission, and the method further includes: determining a reference channel value based on the first uplink transmission; determining an updated channel value based on the second uplink transmission; and determining a change in the uplink channel based on a comparison of the reference channel value with the updated channel value.

[0117] Example 19 may include the method of Example 16 or some other examples herein, further comprising: controlling a receive chain of the radio front end module to receive the first and second uplink transmissions in a first receive state.

[0118] Example 20 may include the method of Example 16 or some other examples herein, further comprising: correlating the reference channel value with the first beamforming matrix; and further calculating the second beamforming matrix based on the correlation of the reference channel value with the first beamforming matrix.

[0119] Example 21 may include the method of Example 16 or some other examples herein, wherein the multiple uplink transmissions include a first uplink transmission and a second uplink transmission, and the method further includes: determining a reference channel value based on the first uplink transmission; determining an updated reference channel value based on the second uplink transmission; and determining a change in the uplink channel based on a comparison of the updated channel value with the reference channel value.

[0120] Example 22 may include the method of Example 21 or some other examples herein, wherein the first uplink transmission comprises a multi-user beamforming report.

[0121] Example 23 may include an apparatus comprising an apparatus for performing one or more elements of a method described in or related to any of Examples 1 to 22, or any other method or process described herein.

[0122] Example 24 may include one or more non-transitory computer-readable media comprising instructions for causing the electronic device to perform one or more elements of a method described in or related to any of Examples 1 to 22 or any other method or process described herein when one or more processors of the electronic device execute the instructions.

[0123] Example 25 may include: an apparatus comprising logic, modules, or circuits to perform one or more elements of a method described in or related to any of Examples 1 to 22, or any other method or process described herein.

[0124] Example 26 may include a method, technique, or process as described or related to any of Examples 1 to 22, or a portion or part thereof.

[0125] Example 27 may include a device comprising: one or more processors and one or more computer-readable media, the computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform a method, technique, or process, or portion thereof, described in or related to any one of Examples 1 to 22.

[0126] Example 28 may include a signal as described in or related to any of Examples 1 to 22, or a portion or part thereof.

[0127] Example 29 may include signals in a wireless network as shown and described herein.

[0128] Example 30 may include a method of communicating in a wireless network as shown and described herein.

[0129] Example 31 may include a system for providing wireless communications as shown and described herein.

[0130] Example 32 may include an apparatus for providing wireless communications as shown and described herein.

[0131] Unless explicitly stated otherwise, any of the above examples may be combined with any other example (or combination of examples). The foregoing description of one or more embodiments provides illustration and description, but is not intended to exhaust the scope of the embodiments or to limit the scope of the embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be obtained from the practice of the various embodiments.

Claims

1. One or more non-transitory computer-readable media having instructions for multi-user communication, which instructions, when executed by one or more processors, cause an access point to: calculating a first beamforming matrix based on feedback information received from the probing operation; transmitting a first multi-user packet using the first beamforming matrix, the first multi-user packet comprising data to be transmitted to a plurality of stations in an orthogonal frequency division multiple access group; receiving uplink transmissions from the plurality of stations; Based on the uplink transmission, calculating a second beamforming matrix; as well as transmitting a second multi-user packet using the second beamforming matrix; The uplink transmission includes a first uplink transmission and a second uplink transmission, and to calculate the second beamforming matrix, the access point is used to: determining a reference channel value based on the first uplink transmission; determining an updated channel value based on the second uplink transmission; and The second beamforming matrix is ​​calculated based on the updated channel values.

2. One or more non-transitory computer-readable media according to claim 1, wherein: The uplink transmission includes acknowledgment information regarding data within the first multi-user packet.

3. One or more non-transitory computer-readable media according to claim 1, wherein: The instructions, when executed, further cause the access point to: The probing operation is performed to acquire a channel for a transmission opportunity duration.

4. One or more non-transitory computer-readable media according to claim 3, wherein: The transmission of the second multi-user packet is within the transmission opportunity duration.

5. The one or more non-transitory computer-readable media of claim 3, wherein: The first beamforming matrix corresponds to a first state of the channel during a first portion of the transmission opportunity duration, and the second beamforming matrix corresponds to a second state of the channel during a second portion of the transmission opportunity duration.

6. The one or more non-transitory computer-readable media of claim 1, wherein: When executed, the instructions further cause the access point to: control a receive chain to receive the first uplink transmission and the second uplink transmission in a first receive state.

7. The one or more non-transitory computer-readable media of claim 1, wherein: The instructions, when executed, further cause the access point to: correlating the reference channel value with the first beamforming matrix; and The second beamforming matrix is ​​further calculated based on a correlation between the reference channel value and the first beamforming matrix.

8. One or more non-transitory computer-readable media according to claim 7, wherein: The instructions, when executed, further cause the access point to calculate the second beamforming matrix based on an inference that a change from the reference channel value to the updated channel value corresponds to a change from the first beamforming matrix to the second beamforming matrix.

9. An apparatus for multi-user communication, comprising: Memory; as well as a processing circuit, the processing circuit being coupled to the memory, the processing circuit being configured to: storing first channel information in the memory based on feedback from a plurality of stations of the wireless local area network in response to one or more reference signals; sending a first multi-user packet to the plurality of stations based on the first channel information; processing uplink transmissions received from the plurality of stations; storing second channel information in the memory based on the uplink transmission; as well as sending a second multi-user packet based on the second channel information; wherein the first channel information corresponds to a downlink channel within a first portion of a transmission opportunity, and the second channel information corresponds to a downlink channel within a second portion of the transmission opportunity; The uplink transmission includes a first uplink transmission and a second uplink transmission, and the processing circuit is further used for: determining a first uplink channel state based on the first uplink transmission; determining a second uplink channel state based on the second uplink transmission; determining an uplink channel state change based on the first uplink channel state and the second uplink channel state; determining a downlink channel state change based on the uplink channel state change; and The second channel information is determined based on the downlink channel state change.

10. The device according to claim 9, wherein: The processing circuit is further configured to perform a sounding operation to acquire the downlink channel for the transmission opportunity.

11. The device according to claim 9, wherein: The uplink transmission includes user uplink data or includes confirmation information about data sent in the first multi-user packet.

12. The device according to claim 9, wherein: The processing circuitry places components of a receive chain in a first receive state to receive the first uplink transmission and the second uplink transmission.

13. The device according to any one of claims 9 to 12, wherein: The processing circuit is further configured to: generating a first transmission parameter based on the first channel information; and Based on the second channel information, a second transmission parameter is generated.

14. The device according to claim 13, wherein: The first transmission parameter comprises a first beamforming matrix or a coding rate, and the second transmission parameter comprises a second beamforming matrix or a coding rate.

15. An access point for multi-user communication, comprising: an application circuit for generating application data to be sent to a plurality of stations; A baseband circuit coupled to the application circuit, the baseband circuit being configured to: Acquire a downlink channel for a transmission opportunity; determining a first beamforming matrix based on a first state of the downlink channel indicated in feedback information in a multi-user beamforming report received during acquisition of the downlink channel; generating a first multi-user packet to be transmitted using the first beamforming matrix; determining a change in an uplink channel based on the plurality of uplink transmissions; determining a second state of the downlink channel based on the change in the uplink channel; determining a second beamforming matrix based on a second state of the downlink channel; as well as generating a second multi-user packet to be transmitted using the second beamforming matrix; as well as A radio front end module is configured to send the first multi-user packet and the second multi-user packet within the transmission opportunity.

16. The access point according to claim 15, wherein: The plurality of uplink transmissions include a first uplink transmission and a second uplink transmission, and the baseband circuit is configured to: determining a reference channel value based on the first uplink transmission; determining an updated channel value based on the second uplink transmission; as well as The change in the uplink channel is determined based on a comparison of the reference channel value and the updated channel value.

17. The access point according to claim 16, wherein: The baseband circuit is further configured to control a receive chain of the radio front end module to receive the first uplink transmission and the second uplink transmission in a first receive state.

18. The access point according to claim 16, wherein: The baseband circuit is also used for: correlating the reference channel value with the first beamforming matrix; and The second beamforming matrix is ​​further calculated based on a correlation between the reference channel value and the first beamforming matrix.

19. The access point according to any one of claims 15 to 18, wherein: The plurality of uplink transmissions include a first uplink transmission and a second uplink transmission, and the baseband circuit is configured to: determining a reference channel value based on the first uplink transmission; determining an updated reference channel value based on the second uplink transmission; as well as The change in the uplink channel is determined based on a comparison of the updated channel value with the reference channel value.

20. The access point of claim 19, wherein: The first uplink transmission includes the multi-user beamforming report.

Images