Integrated circuit

Abstract

To provide an integrated circuit.SOLUTION: An integrated circuit controls processing for receiving a sounding signal, processing for generating first beam forming feedback information based on the sounding signal, and processing for transmitting the first beam forming feedback information on the sounding signal. The first beam forming feedback information is transmitted together with second beam forming feedback information through multi-user transmission. The multi-user transmission is performed on a plurality of communication links including a first communication link and a second communication link. The first beam forming feedback information corresponds to the first communication link, and the second beam forming feedback information corresponds to the second communication link. The first beam forming feedback information and the second beam forming feedback information are subject to time division multiplexing in the multi-user transmission, and simultaneously transmitted.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates generally to communication networks, and more particularly to a sounding method in wireless local area networks based on OFDMA (Orthogonal Frequency Division Multiple Access) and MU-MIMO (Multi-User Multiple Input Multiple Output). [Background technology]

[0002] The IEEE (Institute of Electrical and Electronics Engineers) 802.11 Working Group is developing the 802.11ax HE (High Efficiency) WLAN (Wireless Local Area Network) air interface to achieve very substantial increases in the real-world throughput achieved by users in high-density scenarios while retaining backward compatibility with the previous 802.11a / g / n / ac standards. MU-MIMO (Multi-User Multiple Input Multiple Output) and OFDMA (Orthogonal Frequency Division Multiple Access) transmission are envisioned as the two most important features in 802.11ax. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2015 / 0146812 [Patent Document 2] US Patent Application Publication No. 2015 / 0146807 [Non-patent literature]

[0004] [Non-Patent Document 1] IEEE 802.11-15 / 0132r7, Specification Framework for TGax, July 2015 [Non-Patent Document 2] IEEE 802.11-15 / 0579r3, 802.11ax Preamble Design and Auto-detection, July 2015 [Non-Patent Document 3] IEEE Std 802.11ac-2013 [Non-Patent Document 4] Transmit Beamforming and Detection Design for Uplink Multiuser MIMO System, Proceedings of Fortieth Asilomar Conference on Signals, Systems and Computers, 2006 (ACSSC '06), Page 1593-1600 [Non-Patent Document 5] IEEE Std 802.11n-2009 Summary of the Invention [Problem to be solved by the invention]

[0005] Research is underway to perform efficient sounding in 802.11ax uplink (UL) multi-user (MU) communication, such as UL OFDMA communication or UL MU-MIMO communication. [Means for solving the problem]

[0006] An integrated circuit according to one embodiment of the present disclosure controls a process of receiving a sounding signal, a process of generating first beamforming feedback information based on the sounding signal, and a process of transmitting the first beamforming feedback information of the sounding signal, wherein the first beamforming feedback information is transmitted together with second beamforming feedback information by multi-user transmission, the multi-user transmission is performed on a plurality of communication links including a first communication link and a second communication link, the first beamforming feedback information corresponds to the first communication link, the second beamforming feedback information corresponds to the second communication link, and the first beamforming feedback information and the second beamforming feedback information are time-multiplexed in the multi-user transmission and transmitted simultaneously.

[0007] It should be noted that the general or specific disclosure may be embodied as a system, a method, an integrated circuit, a computer program, a storage medium, or any combination thereof. Effect of the Invention

[0008] With this disclosure, efficient sounding for UL MU transmissions can be achieved. [Brief description of the drawings]

[0009] [Figure 1] Diagram showing an example WLAN [Diagram 2] FIG. 1 shows an exemplary PPDU according to the prior art. [Diagram 3] FIG. 1 is a schematic timing diagram illustrating an example sounding procedure and an example UL MU-MIMO transmission based on the example sounding procedure, according to the prior art; [Figure 4] FIG. 1 is a schematic timing diagram illustrating an example sounding procedure and an example UL MU transmission based on the example sounding procedure according to a first embodiment of the present disclosure; [Diagram 5]FIG. 1 illustrates an example feedback frame according to a first embodiment of the present disclosure. [Figure 6] FIG. 1 is a schematic timing diagram illustrating an example sounding procedure and an example UL MU transmission based on the example sounding procedure according to Example 2 of the present disclosure; [Figure 7] FIG. 11 is a schematic timing diagram illustrating an example sounding procedure and an example UL MU transmission based on the example sounding procedure according to Example 3 of the present disclosure; [Figure 8] FIG. 11 is a schematic timing diagram illustrating an example sounding procedure and an example UL MU transmission based on the example sounding procedure according to a fourth embodiment of the present disclosure; [Figure 9] FIG. 11 is a schematic timing diagram illustrating an example sounding procedure and an example UL MU transmission based on the example sounding procedure according to a fifth embodiment of the present disclosure; [Figure 10] FIG. 11 is a schematic timing diagram illustrating an example sounding procedure and an example UL MU transmission based on the example sounding procedure according to a sixth embodiment of the present disclosure; [Figure 11] 1 is a flow chart illustrating a first example method performed by an AP to perform sounding with a STA for an UL MU transmission according to the present disclosure. [Figure 12] 1 is a flowchart illustrating a first example method performed by a STA to perform sounding with an AP for UL MU transmissions in accordance with the present disclosure. [Figure 13] 1 is a flow chart illustrating a second example method performed by an AP to perform sounding with a STA for cascaded DL and UL MU transmissions according to the present disclosure. [Figure 14] 1 is a flowchart illustrating a second example method performed by a STA to perform sounding with an AP for cascaded DL and UL MU transmissions according to the present disclosure. [Figure 15] FIG. 1 is a block diagram illustrating an example configuration of an AP according to the present disclosure. [Figure 16] FIG. 1 is a block diagram illustrating an example configuration of a STA according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, detailed descriptions of known functions and configurations are omitted for clarity and conciseness.

[0011] <Basic knowledge formation basis of this disclosure> 1 is a diagram of an example WLAN (wireless local area network) 100. The WLAN 100 includes an AP (access point) 102 and multiple STAs (stations) 104 associated with the AP 102. In the downlink (DL) of the WLAN 100, the AP 102 can be configured to simultaneously transmit respective data streams to the multiple STAs 104 via DL MU communication (i.e., DL MU-MIMO or DL ​​OFDMA communication). Similarly, in the uplink (UL) of the WLAN 100, the multiple STAs 104 can simultaneously transmit respective data streams to the AP 102 via UL MU communication (i.e., UL MU-MIMO or UL OFDMA communication).

[0012] For DL ​​or UL OFDMA communications, a data stream is transmitted simultaneously to or from a group of STAs in each of the subbands containing multiple subcarriers, a data stream is transmitted to or by a single STA on a particular subband using SU-MIMO (Single User MIMO) techniques, or a data stream is transmitted simultaneously to or by multiple STAs on a particular subband using MU-MIMO techniques.

[0013] For DL ​​or UL MU-MIMO communication, data streams are transmitted simultaneously to or by a group of STAs over the entire bandwidth using MU-MIMO techniques.

[0014] In SU-MIMO technology, a transmit beamforming matrix is ​​used to precode data for a particular STA, so that the link throughput can be maximized at the receiver output of the particular STA. In MU-MIMO technology, a respective transmit beamforming matrix is ​​used to precode each data stream for each STA of a group of STAs, so that the total throughput (e.g., sum performance or max-min fairness) is maximized. For a particular STA, the transmit beamforming matrices to use for MU-MIMO transmission are usually different from their counterparts for SU-MIMO transmission, because the former need to take into account the multi-user interference present in MU-MIMO transmission. In summary, before any DL or UL MU transmission, the AP 102 needs to interact with the STA 104 via a sounding procedure to perform the necessary preparations, such as user grouping, subband allocation, and deploying transmit beamforming matrices.

[0015] 2 is a diagram of an example physical layer protocol data unit (PPDU) 200 according to the prior art [see Non-Patent Document 1 and Non-Patent Document 2]. The PPDU 200 is an OFDMA PPDU including four OFDM data units 202-1, 202-2, 202-3 and 202-4 in a bandwidth of 80 MHz. For DL ​​MU transmission, the PPDU 200 is generated by the AP 102 of FIG. 1. Thereby, the OFDM data unit 202-1 is transmitted to the STA 104-1 on the first 10 MHz sub-band, the OFDM data unit 202-2 is transmitted to the STA 104-2 on the second 10 MHz sub-band, the OFDM data unit 202-3 is transmitted to the STA 104-3 on the 20 MHz sub-band, and the OFDM data unit 202-4 is transmitted to the STAs 104-4 and 104-5 on the 40 MHz sub-band. Meanwhile, for UL MU transmission, PPDU 200 is collectively generated by STAs 104, whereby OFDM data unit 202-1 is transmitted to AP 102 on the first 10 MHz sub-band by STA 104-1, OFDM data unit 202-2 is transmitted to AP 102 on the second 10 MHz sub-band by STA 104-2, OFDM data unit 202-3 is transmitted to AP 102 on the 20 MHz sub-band by STA 104-3, and OFDM data unit 202-4 is transmitted to AP 102 on the 40 MHz sub-band by STAs 104-4 and 104-5.

[0016] It should be noted that a PPDU is a DL or UL MU-MIMO PPDU if it only contains a single OFDM data unit transmitted by or to the AP 102 over the entire bandwidth using MU-MIMO technology, and a PPDU is a DL or UL SU PPDU if it only contains a single OFDM data unit transmitted by or to the AP 102 over the entire bandwidth using technology other than MU-MIMO.

[0017] 2, the PPDU 200 includes a legacy short training field (L-STF) 204, a legacy long training field (L-LTF) 206, a legacy signal field (L-SIG) 208, a repeated legacy signal field (RL-SIG) 210, a first high-efficiency signal field (HE-SIG-A) 212, a second high-efficiency signal field (HE-SIG-B) 214, a high-efficiency short training field (HE-STF) 216, a high-efficiency long training field (HE-LTF) 218, and a high-efficiency data portion (HE data) 220. The L-STF 204, the L-LTF 206, and the L-SIG 208 facilitate backward compatibility with legacy 802.11a / g / n / ac standards. The RL-SIG 210 is used for automatic detection of the frame format of the PPDU 200. The HE-SIG-A 212 and the HE-SIG-B 214 each convey control information, such as bandwidth, required to interpret the PPDU 200. Specifically, the HE-SIG-B 214 includes control information for the designated receiving STAs, especially for DL ​​MU transmissions. The HE-SIG-B 214 is split into two parts, HE-SIG-B1 and HE-SIG-B2, which convey different control signals. The HE-SIG-B 214 is not present in the PPDU 200 if it is a UL MU PPDU, DL SU PPDU or UL SU PPDU. The HE-STF 216 is used to train an AGC (automatic gain control) for receiving the HE data portion 220 of the corresponding OFDM data unit 202. The HE-LTF 218 includes a number of HE-LTF symbols and is used to generate a MIMO channel estimate for receiving and equalizing the HE data portion 220 of the corresponding OFDM data unit 202.

[0018] L-STF 204, L-LTF 206, L-SIG 208, RL-SIG 210, HE-SIG-A 212, and HE-SIG-B 214 occupy the smallest bandwidth (e.g., 20 MHz) supported by WLAN 100. If PPDU 200 occupies a bandwidth greater than the smallest bandwidth of WLAN 100, L-STF 204, L-LTF 206, L-SIG 208, RL-SIG 210, and HE-SIG-A 212 may be replicated and mapped in their respective smallest bandwidth portions of PPDU 200 (e.g., in their respective 20 MHz portions of PPDU 200). HE-SIG-B1 and HE-SIG-B2 of HE-SIG-B 214 may be replicated and mapped in their respective smallest bandwidth portions of PPDU 200 instead.

[0019] On the other hand, the HE-STF 216, the HE-LTF 218 and the HE data portion 220 occupy the entire bandwidth of the corresponding OFDM data unit 202. For example, the OFDM data unit 202-4 occupies 40 MHz, where the HE-STF 216, the HE-LTF 218 and the HE data portion 220 occupy all 40 MHz bandwidth of the OFDM data unit 202-4.

[0020] 3 is a schematic timing diagram illustrating an example sounding procedure 300 and an example UL MU-MIMO transmission based on the sounding procedure 300 according to the prior art [see Patent Document 1]. The sounding procedure 300 is an explicit sounding procedure in which the AP 102 derives a channel estimate corresponding to the communication channel from the STA to the AP 102 directly from a sounding frame transmitted by the STA to the AP 102.

[0021] The AP 102 transmits a sounding announcement frame 302-1 to the STA 104-1 during time interval 322-1 to request the STA 104-1 to transmit a sounding frame. The STA 104-1 transmits a sounding frame 304-1 to the AP 102 in response to receiving the sounding announcement frame 302-1 during time interval 324-1. The AP 102 obtains a channel estimate characterizing a communication channel from the STA 104-1 to the AP 102 based on a training signal included in the sounding frame 304-1. Furthermore, the AP 102 generates beamforming feedback information for the STA 104-1 based on the channel estimate characterizing a communication channel from the STA 104-1 to the AP 102. The AP 102 transmits a feedback frame 306-1 to the STA 104-1 including the beamforming feedback information for the STA 104-1 during time interval 326-1. The STA 104-1 uses the received beamforming feedback frame 306-1 to generate its transmit beamforming matrix for UL MU-MIMO transmission.

[0022] The AP 102 can sequentially cause other STAs (e.g., 104-2 and 104-3) to transmit sounding frames, can obtain channel estimates characterizing a communication channel from each of the other STAs to the AP 102, and can transmit beamforming feedback to each of the other STAs. For example, the AP 102 transmits a sounding announcement frame 302-2 to the STA 104-2 during time interval 322-2. In response to receiving the sounding announcement frame 302-2, the STA 104-2 transmits a sounding frame 304-2 to the AP 102 during time interval 324-2. The AP 102 obtains a channel estimate characterizing a communication channel from the STA 104-2 to the AP 102 based on a training signal included in the sounding frame 304-2, and further generates beamforming feedback information for the STA 104-2. The AP 102 transmits a feedback frame 306-2 including beamforming feedback information for the STA 104-2 to the STA 104-2 during time interval 326-2. The STA 104-2 uses the received beamforming feedback frame 306-2 to generate its transmit beamforming matrix for UL MU-MIMO transmission. The same sounding procedure is performed between the AP 102 and the STA 104-3 during the next time intervals 322-3, 324-3 and 326-3.

[0023] During time interval 328 of FIG. 3, the AP 102 selects a subset of STAs (e.g., STAs 104-1 and 104-2 in this example) for inclusion in a UL group for UL MU-MIMO transmission based on received sounding frames 304 (e.g., 304-1, 304-2, and 304-3) from the STAs 104. During time interval 332, the AP 102 transmits a trigger frame 308 to each STA of the UL group (e.g., STAs 104-1 and 104-2 in this example) for UL MU-MIMO transmission. The trigger frame 308 causes the STAs of the UL group to transmit data streams to the AP 102 simultaneously in a particular time interval. The STAs of the UL group (i.e., STAs 104-1 and 104-2 in this example) transmit their respective data streams 310 to the AP 102 simultaneously using their respective transmit beamforming matrices during time interval 334.

[0024] According to the prior art, for UL MU-MIMO transmission, the transmit beamforming matrix used by a particular STA is obtained based on the channel estimation for the particular STA, and does not consider the channel estimation of other STAs that belong to the same UL group as the particular STA. Thus, the transmit beamforming matrix may not be useful for mitigating multi-user interference in UL MU-MIMO transmission. As a result, even if an advanced receiver is used by the AP 102, it may not be able to sufficiently suppress the multi-user interference for the UL MU-MIMO transmission, and thus the total throughput for the UL MU-MIMO transmission may be impaired. In addition, the prior art as illustrated in FIG. 3 cannot efficiently handle subband-based UL OFDMA transmission. The present disclosure is made in view of the above knowledge.

[0025] Next, various embodiments for the sounding procedure of the present disclosure and corresponding UL MU transmissions will be described in further detail.

[0026] Example 1 4 is a schematic timing diagram illustrating an example sounding procedure 400 and an example UL MU transmission based on the sounding procedure 400 according to a first embodiment of the present disclosure. The sounding procedure 400 is an explicit sounding procedure in which the AP 102 derives channel state information and / or quality indicators corresponding to a communication channel from the STA to the AP 102 directly from a sounding frame transmitted by the STA to the AP 102.

[0027] The AP 102 transmits a sounding announcement frame 402-1 to the STA 104-1 during the time interval 422-1 to initiate the sounding procedure 400 and request the STA 104-1 to transmit a sounding frame. The STA 104-1 transmits a sounding frame 404-1 to the AP 102 during the time interval 424-1 in response to receiving the sounding announcement frame 402-1. The sounding frame 404-1 includes an appropriate training signal in a PHY (physical layer) preamble (e.g., HE-LTF field) to enable the AP 102 to obtain channel state information and / or quality indicators of the communication channel from the STA 104-1 to the AP 102. The sounding frame 404-1 may also include UL power control information (e.g., transmit power, power adjustment range and / or power headroom) for the STA 104-1 in the PHY preamble (e.g., HE-SIG-A field). The sounding frame may be a null data packet (NDP) that includes only a PHY preamble and omits a payload. The AP 102 obtains channel state information (e.g., gain, phase, SNR (signal-to-noise ratio), etc.) corresponding to the entire bandwidth of the communication channel from the STA 104-1 to the AP 102 based on the training signal included in the sounding frame 404-1. Additionally or alternatively, the AP 102 determines quality indicators (e.g., SNR, SNIR (signal-to-noise-plus-interference ratio), signal strength, etc.) corresponding to one or more subbands of the communication channel from the STA 104-1 to the AP 102. The AP 102 further identifies one or more candidate subbands for the STA 104-1 to be used for UL transmission based on the quality indicators corresponding to one or more subbands of the communication channel from the STA 104-1 to the AP 102.

[0028] The AP 102 can have the other STAs (e.g., 104-2 and 104-3) transmit sounding frames sequentially. The AP 102 obtains channel state information corresponding to the entire bandwidth of the communication channel from each of the other STAs to the AP 102 and / or quality indicators corresponding to one or more subbands of the communication channel from each of the other STAs to the AP 102 based on the training signal included in the sounding frame. The AP 102 determines one or more candidate subbands for each other STA to the AP 102 based on the quality indicators corresponding to one or more subbands of the communication channel from each of the other STAs to the AP 102. For example, the AP 102 transmits a sounding announcement frame 402-2 to the STA 104-2 during the time interval 422-2. The STA 104-2 transmits a sounding frame 404-2 to the AP 102 in response to receiving the sounding announcement frame 402-2 during the time interval 424-2. The AP 102 obtains channel state information corresponding to the entire bandwidth of the communication channel from the STA 104-2 to the AP 102. Additionally or alternatively, the AP 102 determines quality indicators corresponding to one or more subbands of the communication channel from the STA 104-2 to the AP 102. The AP 102 further identifies one or more candidate subbands for the STA 104-2 to be used for UL transmission. The same sounding procedure is performed between the AP 102 and the STA 104-3 in subsequent time intervals 422-3 and 424-3.

[0029] According to a first embodiment of the present disclosure, the AP 102 identifies an intended use of a transmission scheme for the entire bandwidth and / or each of the one or more candidate subbands for each STA based on the channel state information corresponding to the entire bandwidth of the communication channel from each STA to the AP 102 and / or the quality indicators corresponding to one or more candidate subbands of the communication channel from each STA to the AP 102. For example, the AP 102 determines whether the entire bandwidth or each of the one or more candidate subbands for each STA should be used for UL SU-MIMO transmission, UL MU-MIMO transmission, or both.

[0030] According to embodiment 1 of the present disclosure, if the AP 102 expects that only a single STA has buffered data to transmit on the entire bandwidth (e.g., only a single STA has indicated to the AP 102 that it has a large amount of buffered data to transmit), it can determine that the entire bandwidth should be used only for UL SU-MIMO transmissions.

[0031] According to embodiment 1 of the present disclosure, if the AP 102 expects that two or more STAs have buffered data to transmit over the entire bandwidth (e.g., two or more STAs have indicated to the AP 102 that they have a large amount of buffered data to transmit), the AP 102 can determine that the entire bandwidth should be used exclusively for UL MU-MIMO transmissions.

[0032] According to embodiment 1 of the present disclosure, the AP 102 can determine that the entire bandwidth must be used for UL SU-MIMO or UL MU-MIMO transmissions if it is not known how the entire bandwidth will be used for some time.

[0033] According to the first embodiment of the present disclosure, the AP 102 may determine that a candidate subband should be used only for UL SU-MIMO transmission if the candidate subband is dominated by a single STA.

[0034] According to embodiment 1 of the present disclosure, the AP 102 may determine that a candidate subband should be used only for UL SU-MIMO transmission if the candidate subband is shared by two or more STAs, but only one of the two or more STAs expects to have buffered data to transmit on the candidate subband (e.g., only one of the two or more STAs has indicated to the AP 102 that it has a large amount of buffered data to transmit).

[0035] According to embodiment 1 of the present disclosure, the AP 102 may determine that a candidate subband should be used only for UL MU-MIMO transmissions if the candidate subband is shared by two or more STAs and the AP 102 expects that two or more STAs have buffered data to transmit on the candidate subband (e.g., two or more STAs have indicated to the AP 102 that they have a large amount of buffered data to transmit).

[0036] According to embodiment 1 of the present disclosure, the AP 102 can determine that a candidate subband should be used for UL SU-MIMO or UL MU-MIMO transmission if the candidate subband is shared by two or more STAs, but the AP 102 does not know how the candidate subband will be used for some time.

[0037] According to the first embodiment of the present disclosure, if the AP 102 determines that the entire bandwidth or the candidate subbands should be used only for UL SU-MIMO transmission by the STA, the AP 102 deploys a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission on the entire bandwidth or the candidate subbands. For example, H k Let us assume that Q represents the channel matrix of the communication channel from the STA to the AP 102 for the k-th tone (subcarrier). Then, the transmit beamforming matrix Q specific to the UL SU-MIMO transmission for the k-th tone isk Q k =V k where V k is the channel matrix H k can be obtained by singular value decomposition (SVD) of

[0038] According to a first embodiment of the present disclosure, if the AP 102 determines that the entire bandwidth or the candidate subbands should be used only for UL MU-MIMO transmission by the group of STAs, it deploys a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmission on the entire bandwidth or the candidate subbands. For example, if a group of N STAs engages in UL MU-MIMO transmission on the entire bandwidth or the candidate subbands, and H k,i Let Q denote the channel matrix on the candidate subband for the i-th STA and k-th tone of the entire bandwidth or group. Then, the transmit beamforming matrix Q k,i , i=1,2..,N} can be selected using the method shown in equation (1) below.

[0039] (H k,i Q k,i ) H (H k,j Q k,j )=0 (1)

[0040] where i ≠ j and i,j = 1, 2 .. , N. As a result, multi-user interference in UL MU-MIMO transmissions is suppressed and a simpler receiver can be used by the AP 102 to receive the UL MU-MIMO transmissions. The transmit beamforming matrix {Q k,i For an example method for determining {i=1,2..,N}, see [Non-Patent Document 4].

[0041] According to embodiment 1 of the present disclosure, when the AP 102 determines that the entire bandwidth or a candidate subband should be used for UL SU-MIMO transmission by a STA or UL MU-MIMO transmission by a group of STAs, the AP 102 deploys both a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission and a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmission on the entire bandwidth or candidate subband.

[0042] During the time interval 426, the AP 102 transmits a feedback frame 406-1 to the STA 104-1. The AP 102 can then sequentially transmit feedback frames 406-2 and 406-3 to the other STAs 104-2 and 104-3, respectively. For example, the AP 102 transmits a feedback frame 406-2 to the STA 104-2. The STAs 104 directly derive their respective transmit beamforming matrices from the data of their respective feedback frames 406 for UL MU transmission.

[0043] According to a first embodiment of the present disclosure, the feedback frame 406 for the specific STA includes one or more of the following: (i) an indication of one or more candidate subbands for the specific STA; (ii) intended use of a transmission scheme corresponding to each of the one or more candidate subbands for the specific STA; (iii) one or more quality indicators corresponding to each of the one or more candidate subbands for the specific STA; (iv) beamforming feedback corresponding to each of the one or more candidate subbands for the specific STA; (v) intended use of a transmission scheme corresponding to the entire bandwidth for the specific STA; (vi) one or more quality indicators corresponding to the entire bandwidth for the specific STA; (vii) beamforming feedback information corresponding to the entire bandwidth for the specific STA; and (viii) UL power control information (e.g., a required power adjustment amount), etc.

[0044] According to the first embodiment of the present disclosure, what is included in the beamforming feedback information corresponding to the entire bandwidth or the candidate subband for a particular STA depends on the intended use of the transmission scheme for the entire bandwidth or the candidate subband for a particular STA. If the entire bandwidth or the candidate subband must be used only for UL SU-MIMO transmission, the beamforming feedback information corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL SU-MIMO transmission. If the entire bandwidth or the candidate subband must be used only for UL MU-MIMO transmission, the beamforming feedback information corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL MU-MIMO transmission. If the entire bandwidth or the candidate subband must be used for UL SU-MIMO or UL MU-MIMO transmission, the beamforming feedback information corresponding to the entire bandwidth or the candidate subband represents both a transmit beamforming matrix specific to the UL SU-MIMO transmission and a transmit beamforming matrix specific to the UL MU-MIMO transmission.

[0045] According to the first embodiment of the present disclosure, when a first STA (e.g., STA 104-1) and a second STA (e.g., STA 104-2) engage in UL MU-MIMO transmission over the entire bandwidth or a specific subband, a transmit beamforming matrix specific to the UL MU-MIMO transmission over the entire bandwidth or a specific subband represented in a feedback frame for the first STA (e.g., feedback frame 406-1 for STA 104-1) is based on the deployed transmit beamforming matrix. The transmit beamforming matrix specific to the UL MU-MIMO transmission is deployed not only in the sounding frame transmitted by the first STA (e.g., sounding frame 404-1 transmitted by STA 104-1) but also in the sounding frame transmitted by the second STA (e.g., sounding frame 404-2 transmitted by STA 104-2). In other words, the transmit beamforming matrix specific to UL MU-MIMO transmission represented in a feedback frame for a first STA (e.g., feedback frame 406-1 for STA 104-1) changes when channel conditions between the AP 102 and a second STA (e.g., STA 104-2) change, even if the channel conditions between the AP 102 and the first STA (e.g., STA 104-1) do not change.

[0046] Figure 5 illustrates an example feedback frame 500 that the AP 102 is configured to transmit to the STAs during the sounding procedure 400 of Figure 4. The feedback frame 500 corresponds to each of the feedback frames 406-1, 406-2, and 406-3 of Figure 4. The feedback frame 500 includes a MIMO control field 502, a full-band feedback portion 504, and a sub-band feedback portion 506.

[0047] The full band feedback portion 504 includes a power control unit information field 512, an average SNR field 514, an intended use field 516, and a beamforming feedback field 518. The full band feedback portion 504 includes feedback covering the entire bandwidth of the communication channel. Alternatively, the full band feedback portion 504 includes feedback covering the bandwidth of a sounding frame based on which the feedback was generated by the AP 102. The beamforming feedback field 518 includes some form of beamforming feedback over the entire bandwidth for a particular STA that is generated by the AP 102 based on a sounding frame transmitted by the particular STA. As mentioned above, the beamforming feedback over the entire bandwidth depends on the transmission scheme that is intended to be used for the entire bandwidth. The beamforming feedback field 518 includes compressed beamforming feedback similar to that defined in the IEEE 802.11ac standard. Alternatively, the beamforming feedback field 518 includes another suitable form of beamforming feedback, such as uncompressed beamforming feedback similar to that defined in the IEEE 802.11n standard.

[0048] The subband feedback portion 506 includes a number of candidate subband fields 522 and a number of subband-based feedback fields 524, each of which corresponds to a particular candidate subband. Each subband-based feedback field 524 includes a subband indication field 532, an average SNR per subband field 534, an intended use per subband field 536, and a beamforming feedback per subband field 538. The subband indication field 532 indicates a particular subband. The beamforming feedback per subband field 538 includes some form of beamforming feedback on a particular subband for a particular STA generated by the AP 102 based on a sounding frame transmitted by the particular STA. As mentioned above, the beamforming feedback on a particular subband depends on the transmission scheme intended to be used for the particular subband specified in the corresponding intended use per subband field 536. The beamforming feedback per subband field 538 includes compressed beamforming feedback similar to that defined in the IEEE 802.11ac standard. Alternatively, the beamforming feedback per subband field 516 comprises another suitable form of beamforming feedback, such as uncompressed beamforming feedback similar to that defined in the IEEE 802.11n standard.

[0049] 4, the AP 102 selects a subset of the STAs for inclusion in an UL group (e.g., STAs 104-1 and 104-2 in this example) for UL MU transmission based on channel state information corresponding to the entire bandwidth, quality indicators corresponding to one or more subbands of the communication channel, and / or data buffer status obtained for at least some of the STAs 104. The AP 102 also assigns respective transmission resources (e.g., subbands for UL OFDMA) to the STAs of the UL group, specifying respective transmission schemes.

[0050] For one example, if two or more STAs indicate to the AP 102 that they have a large amount of buffered data to transmit and the quality of the communication channel for each of the two or more STAs is acceptable (e.g., the SNR corresponding to the entire bandwidth exceeds a predetermined threshold), the AP 102 can select the two or more STAs for inclusion in a UL group and can schedule the two or more STAs in the UL group to perform UL MU-MIMO transmissions on the entire bandwidth.

[0051] For another example, if two or more STAs indicate to the AP 102 that they have buffered data to be transmitted and that the quality corresponding to one or more candidate subbands for each of the two or more STAs is acceptable (e.g., the SINR corresponding to the candidate subbands exceeds a predetermined threshold), the AP 102 may select the two or more STAs for inclusion in an UL group. The AP 102 may then assign respective subbands to the two or more STAs of the UL group and schedule the two or more STAs of the UL group to perform UL SU-MIMO transmissions on their respective assigned subbands.

[0052] According to the first embodiment of the present disclosure, the timing order of the feedback transmission (time interval 426) and the grouping and subband allocation (time interval 428) in FIG. 4 may be interchangeable. For example, the AP 102 may select a subset of STAs for inclusion in a UL group, specify respective transmission schemes, and initially allocate respective transmission resources to each STA in the UL group during time interval 426. The AP 102 then proceeds to transmit respective feedback frames 406 to the STAs 104 in the UL group during time interval 428.

[0053] The AP 102 transmits a trigger frame 408 to the STAs (e.g., STAs 104-1 and 104-2 in this example) included in the UL group for UL MU transmission during the time interval 432. The trigger frame 408 causes the STAs in the UL group to transmit data to the AP 102 simultaneously in the specific time interval. The trigger frame 408 also includes information regarding a designated transmission scheme and / or an assigned transmission resource for each STA in the UL group.

[0054] During the time interval 434, the STAs of the UL group (e.g., STAs 104-1 and 104-2 in this example) simultaneously transmit their respective data 410 to the AP 102 on the entire bandwidth using their respective transmit beamforming matrices specific to UL MU-MIMO transmission on the entire bandwidth if the trigger frame 408 initiates UL MU-MIMO transmission. The STAs of the UL group simultaneously transmit their respective data 410 to the AP 102 on the respective assigned subbands using their respective transmit beamforming matrices if the trigger frame 408 initiates UL OFDMA transmission. These transmit beamforming matrices may be generated from the respective feedback frames 406 according to the respective designated transmission schemes and the respective assigned subbands. For example, if the designated transmission scheme for the STA 104-1 is UL SU-MIMO, the transmit beamforming matrix specific to UL SU-MIMO transmission on the assigned subbands for the STA 104-1 is generated directly from the corresponding data of the feedback frame 406-1.

[0055] Example 2 6 is a schematic timing diagram illustrating an example sounding procedure 600 and an example UL MU transmission based on the sounding procedure 600 according to a second embodiment of the present disclosure. Similar to the sounding procedure 400 of FIG. 4, the sounding procedure 600 is also an explicit sounding procedure.

[0056] The AP 102 transmits a sounding announcement frame 602-1 to the STA 104-1 during time interval 622-1 to initiate the sounding procedure 600 and request the STA 104-1 to transmit a sounding frame. The STA 104-1 transmits a sounding frame 604-1 to the AP 102 in response to receiving the sounding announcement frame 602-1 during time interval 624-1. The sounding frame 604-1 includes an appropriate training signal in the PHY preamble (e.g., HE-LTF field). The sounding frame 604-1 may also include UL power control information (e.g., transmit power, power adjustment range and / or power headroom) for the STA 104-1 in the PHY preamble (e.g., HE-SIG-A field). The sounding frame 604-1 may be an NDP. The AP 102 obtains channel state information (e.g., gain, phase, SNR, etc.) corresponding to the entire bandwidth of the communication channel from the STA 104-1 to the AP 102 based on the training signal included in the sounding frame 604-1. Additionally or alternatively, the AP 102 determines quality indicators (e.g., SNR, SNIR, signal strength, etc.) corresponding to one or more subbands of the communication channel from the STA 104-1 to the AP 102. The AP 102 further identifies one or more candidate subbands for the STA 104-1 to be used for UL transmission.

[0057] The AP 102 can have the other STAs 104 transmit their respective sounding frames sequentially. The AP 102 obtains channel state information corresponding to the entire bandwidth of the communication channel from each of the other STAs 104 to the AP 102 and / or quality indicators corresponding to one or more subbands of the communication channel from each of the other STAs 104 to the AP 102 based on the received sounding frames. The AP 102 further identifies one or more candidate subbands for each of the other STAs 104. For example, the AP 102 transmits a sounding announcement frame 602-2 to the STA 104-2 during the time interval 622-2. The STA 104-2 transmits a sounding frame 604-2 to the AP 102 in response to receiving the sounding announcement frame 602-2 during the time interval 624-2. The AP 102 obtains channel state information corresponding to the entire bandwidth of the communication channel from the STA 104-2 to the AP 102. Additionally or alternatively, the AP 102 determines a quality indicator corresponding to each one or more subbands of the communication channel from the STA 104-2 to the AP 102. Furthermore, the AP 102 identifies one or more candidate subbands for the STA 104-2 to be used for UL transmission.

[0058] According to a second embodiment of the present disclosure, the AP 102 identifies an intended use of a transmission scheme for the entire bandwidth and / or each of the one or more candidate subbands for each STA 104 based on the channel state information corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 and / or the quality indicators corresponding to one or more candidate subbands of the communication channel from each STA 104 to the AP 102. For example, the AP 102 determines whether the entire bandwidth or each of the one or more candidate subbands for each STA 104 should be used for UL SU-MIMO transmissions, UL MU-MIMO transmissions, or both.

[0059] According to embodiment 2 of the present disclosure, if the AP 102 determines that the entire bandwidth or the candidate subbands should be used only for UL SU-MIMO transmission by the STA, it develops a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission on the entire bandwidth or the candidate subbands in a manner similar to embodiment 1.

[0060] According to embodiment 2 of the present disclosure, if the AP 102 determines that the entire bandwidth or candidate subbands should be used only for UL MU-MIMO transmissions by the group of STAs, it develops a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmissions on the entire bandwidth or candidate subbands in a manner similar to embodiment 1.

[0061] According to embodiment 2 of the present disclosure, when the AP 102 determines that the entire bandwidth or the candidate subbands should be used for UL SU-MIMO transmission by a STA or UL MU-MIMO transmission by a group of STAs, it deploys a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission and a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmission on the entire bandwidth or the candidate subbands.

[0062] During the time interval 626, the AP 102 transmits each feedback frame 606 to the STAs 104 simultaneously in a DL MU PPDU by multiplexing the feedback frame with DL OFDMA or DL ​​MU-MIMO. In this example, the AP 102 transmits feedback frames 606-1, 606-2, and 606-3 to the STAs 104-1, 104-2, and 104-3, respectively, in a DL MU PPDU. It should be noted that the transmit beamforming matrix used by the AP 102 for each STA 104 in DL MU transmission is obtained in advance through a sounding procedure for DL ​​MU transmission (see, for example, Patent Document 2). The STAs 104 obtain their respective transmit beamforming matrices directly from the data of their respective feedback frames 606 for UL MU transmission.

[0063] According to the second embodiment of the present disclosure, the feedback frames 606 are transmitted by the AP 102 to the STAs 104 simultaneously, so that the channel efficiency is improved compared with the first embodiment in which the feedback frames 406 are transmitted by the AP 102 to the STAs 104 sequentially.

[0064] According to a second embodiment of the present disclosure, the feedback frame 606 for the specific STA includes one or more of the following: (i) an indication of one or more candidate subbands for the specific STA; (ii) intended use of a transmission scheme corresponding to each of the one or more candidate subbands for the specific STA; (iii) one or more quality indicators corresponding to each of the one or more candidate subbands for the specific STA; (iv) beamforming feedback corresponding to each of the one or more candidate subbands for the specific STA; (v) intended use of a transmission scheme corresponding to the entire bandwidth for the specific STA; (vi) one or more quality indicators corresponding to the entire bandwidth for the specific STA; (vii) beamforming feedback corresponding to the entire bandwidth for the specific STA; and (viii) power control information (e.g., a required power adjustment amount), etc.

[0065] According to the second embodiment of the present disclosure, what is included in the beamforming feedback corresponding to the entire bandwidth or the candidate subband for a particular STA depends on the intended use of the transmission scheme for the entire bandwidth or the candidate subband for a particular STA. If the entire bandwidth or the candidate subband is to be used only for UL SU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL SU-MIMO transmission. If the entire bandwidth or the candidate subband is to be used only for UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL MU-MIMO transmission. If the entire bandwidth or the candidate subband is to be used for UL SU-MIMO or UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL SU-MIMO transmission and a transmit beamforming matrix specific to the UL MU-MIMO transmission.

[0066] The AP 102 selects a subset of the STAs for inclusion in a UL group for UL MU transmission based on channel state information corresponding to the entire bandwidth, quality indicators corresponding to one or more subbands of the communication channel, and / or data buffer status obtained for at least some of the STAs 104 during the time interval 628. The AP 102 also assigns respective transmission resources (e.g., subbands for UL OFDMA) to the STAs of the UL group, specifying respective transmission schemes.

[0067] According to the second embodiment of the present disclosure, the timing order of feedback transmission (time interval 626) and grouping and subband allocation (time interval 628) in FIG. 6 may be interchangeable. For example, the AP 102 may select STAs for inclusion in the UL group, specify their respective transmission schemes, and allocate their respective transmission resources to the STAs of the UL group first during the time interval 626. The AP 102 then proceeds to transmit the respective feedback frames 606 to the STAs 104 of the UL group during the time interval 628.

[0068] The AP 102 transmits a trigger frame 608 to the STAs of the UL group for UL MU transmission (e.g., STAs 104-1 and 104-2 in this example) during the time interval 632. The trigger frame 608 causes the STAs of the UL group to transmit data to the AP 102 simultaneously at a specific time. The trigger frame 608 causes the STAs of the UL group to transmit data to the AP 102 simultaneously at a specific time. The trigger frame 608 also includes information regarding the designated transmission scheme and / or assigned transmission resources for each STA of the UL group.

[0069] During time interval 634, the STAs of the UL group (i.e., STAs 104-1 and 104-2 in this example) transmit their respective data 610 simultaneously on the entire bandwidth to the AP 102 using their respective transmit beamforming matrices specific to UL MU-MIMO transmission on the entire bandwidth when the trigger frame 608 initiates UL MU-MIMO transmission. The STAs of the UL group transmit their respective data 610 simultaneously to the AP 102 on the respective assigned subbands using their respective transmit beamforming matrices, which may be generated from the respective feedback frames 606 according to their respective designated transmission schemes and their respective assigned subbands when the trigger frame 608 initiates UL OFDMA transmission. For example, if the designated transmission scheme for STA 104-1 is UL SU-MIMO, the transmit beamforming matrix specific to UL SU-MIMO transmission on the assigned subbands for STA 104-1 is generated directly from the corresponding data of the feedback frame 606-1.

[0070] Example 3 7 is a schematic timing diagram illustrating an example sounding procedure 700 and an example UL MU transmission based on the sounding procedure 700 according to a third embodiment of the present disclosure. Similar to the sounding procedure 400 of FIG. 4, the sounding procedure 700 is also an explicit sounding procedure.

[0071] The AP 102 initiates the sounding procedure 700 by transmitting a sounding announcement frame 702 to the STAs 104 during a time interval 722. In other words, a single sounding announcement frame 702 is multicast to all the STAs 104. The sounding announcement frame 702 includes information for coordinating the timing at which the STAs 104 transmit their respective sounding frames. For example, the payload of the sounding announcement frame 702 may indicate a ranking of the STAs 104 that are requested to transmit sounding frames.

[0072] According to the third embodiment of the present disclosure, since the sounding announcement frame 702 is multicast to the STAs 104, channel efficiency is improved compared to the second embodiment in which the sounding announcement frame 602 is individually transmitted by the AP 102 to the STAs 104.

[0073] In response to receiving the sounding announcement frame 702 during the time interval 724, the STAs 104 sequentially transmit their respective sounding frames 704 to the AP 102 according to timing information included in the sounding announcement frame 702. In this example, the STA 104-1 transmits a sounding frame 704-1 to the AP 102, followed by the STAs 104-2 and 104-3 transmitting sounding frames 704-1 to the AP 102. Each sounding frame 704 includes an appropriate training signal in the PHY preamble (e.g., HE-LTF field). Each sounding frame 704 may also include UL power control information for the STA 104 transmitting the sounding frame (e.g., transmit power, power adjustment range and / or power headroom) in the PHY preamble (e.g., HE-SIG-A field). Each sounding frame 704 may be an NDP. The AP 102 obtains channel state information (e.g., gain, phase, SNR, etc.) corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 based on the training signal included in each sounding frame 704. Additionally or alternatively, the AP 102 determines quality indicators (e.g., SNR, SNIR, signal strength, etc.) corresponding to each of one or more subbands of the communication channel from each STA 104 to the AP 102. The AP 102 further identifies one or more candidate subbands for each STA 104 to be used for UL transmission.

[0074] According to a third embodiment of the present disclosure, the AP 102 identifies an intended use of a transmission scheme for the entire bandwidth and / or each of the one or more candidate subbands for each STA 104 based on the channel state information corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 and / or the quality indicators corresponding to one or more candidate subbands of the communication channel from each STA 104 to the AP 102. For example, the AP 102 determines whether the entire bandwidth or each of the one or more candidate subbands for each STA 104 should be used for UL SU-MIMO transmission, UL MU-MIMO transmission, or both.

[0075] According to embodiment 3 of the present disclosure, if the AP 102 determines that the entire bandwidth or the candidate subbands should be used only for UL SU-MIMO transmission by the STA, it develops a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission on the entire bandwidth or the candidate subbands in a manner similar to embodiment 1.

[0076] According to embodiment 3 of the present disclosure, if the AP 102 determines that the entire bandwidth or candidate subbands should be used only for UL MU-MIMO transmission by the group of STAs, it develops a transmit beamforming matrix for each STA in the UL group specific to UL MU-MIMO transmission on the entire bandwidth or candidate subbands in a manner similar to embodiment 1.

[0077] According to embodiment 3 of the present disclosure, when the AP 102 determines that the entire bandwidth or a candidate subband should be used for UL SU-MIMO transmission by a STA or UL MU-MIMO transmission by a group of STAs, it deploys both a transmit beamforming matrix specific to UL SU-MIMO transmission for the STA and a transmit beamforming matrix specific to UL MU-MIMO transmission for each STA in the group over the entire bandwidth or candidate subband.

[0078] During the time interval 726, the AP 102 transmits the respective feedback frames 706 to the STAs 104 simultaneously in a DL MU PPDU. In this example, the AP 102 transmits feedback frames 706-1, 706-2, and 706-3 to the STAs 104-1, 104-2, and 104-3, respectively, in the DL MU PPDU. Note that the transmit beamforming matrix used by the AP 102 for each STA 104 for DL ​​MU transmission is obtained in advance via a sounding procedure for DL ​​MU transmission. The STAs 104 obtain their respective transmit beamforming matrices directly from the data of the respective feedback frames 706 for UL MU transmission.

[0079] According to a third embodiment of the present disclosure, the feedback frame 706 for the specific STA includes one or more of the following: (i) an indication of one or more candidate subbands for the specific STA; (ii) intended use of a transmission scheme corresponding to each of the one or more candidate subbands for the specific STA; (iii) one or more quality indicators corresponding to each of the one or more candidate subbands for the specific STA; (iv) beamforming feedback corresponding to each of the one or more candidate subbands for the specific STA; (v) intended use of a transmission scheme corresponding to the entire bandwidth for the specific STA; (vi) one or more quality indicators corresponding to the entire bandwidth for the specific STA; (vii) beamforming feedback corresponding to the entire bandwidth for the specific STA; and (viii) power control information (e.g., a required power adjustment amount), etc.

[0080] According to the third embodiment of the present disclosure, what is included in the beamforming feedback corresponding to the entire bandwidth or the candidate subband for a particular STA depends on the intended use of the transmission scheme for the entire bandwidth or the candidate subband for a particular STA. If the entire bandwidth or the candidate subband is to be used only for UL SU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL SU-MIMO transmission. If the entire bandwidth or the candidate subband must be used only for UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL MU-MIMO transmission. If the entire bandwidth or the candidate subband must be used for UL SU-MIMO or UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents both a transmit beamforming matrix specific to the UL SU-MIMO transmission and a transmit beamforming matrix specific to the UL MU-MIMO transmission.

[0081] The AP 102 selects STAs for inclusion in a UL group for UL MU transmission based on channel state information corresponding to the entire bandwidth and / or quality indicators corresponding to one or more subbands of the communication channel obtained for at least some of the STAs 104 during time interval 728. The AP 102 also assigns respective transmission resources (e.g., subbands for UL OFDMA) to the STAs of the UL group, specifying respective transmission schemes.

[0082] According to the third embodiment of the present disclosure, the timing order of feedback transmission (time interval 726) and grouping and subband allocation (time interval 728) in FIG. 7 may be interchangeable. For example, the AP 102 may select STAs for inclusion in a UL group, specify their respective transmission schemes, and initially allocate their respective transmission resources to the STAs of the UL group during the time interval 726. Then, the AP 102 transmits the respective feedback frames 706 to the STAs 104 in succession during the time interval 728.

[0083] The AP 102 transmits a trigger frame 708 to the STAs of the UL group (e.g., STAs 104-1 and 104-2 in this example) for UL MU transmission during the time interval 732. The trigger frame 708 causes the STAs of the UL group to transmit data to the AP 102 simultaneously at a specific time. The trigger frame 708 also includes information regarding the designated transmission scheme and / or assigned transmission resources for each STA of the UL group.

[0084] During time interval 734, the STAs of the UL group (i.e., STAs 104-1 and 104-2 in this example) transmit their respective data 710 simultaneously on the entire bandwidth to the AP 102 using their respective transmit beamforming matrices specific to UL MU-MIMO transmission on the entire bandwidth if the trigger frame 708 initiates UL MU-MIMO transmission. The STAs of the UL group transmit their respective data 710 simultaneously on their respective assigned subbands to the AP 102 using their respective transmit beamforming matrices, which may be generated from their respective feedback frames 706 according to their respective designated transmission schemes and their respective assigned subbands, if the trigger frame 708 initiates UL OFDMA transmission. For example, if the designated transmission scheme for STA 104-1 is UL SU-MIMO, the transmit beamforming matrix specific to UL SU-MIMO transmission on the assigned subbands for STA 104-1 is generated directly from the corresponding data of the feedback frame 706-1.

[0085] Example 4 8 is a schematic timing diagram illustrating an example sounding procedure 800 and an example UL MU transmission based on the sounding procedure 800 according to a fourth embodiment of the present disclosure. Similar to the sounding procedure 400 of FIG. 4, the sounding procedure 800 is also an explicit sounding procedure.

[0086] The AP 102 initiates the sounding procedure 800 by transmitting a sounding announcement frame 802 to the STAs 104 during a time interval 822. The sounding announcement frame 802 includes information that coordinates the timing of when the STAs 104 transmit their respective sounding frames. For example, the payload of the sounding announcement frame 802 may indicate an ordering of the STAs 104 that are required to transmit sounding frames.

[0087] In response to receiving the sounding announcement frame 802 during the time interval 824, the STAs 104 sequentially transmit their respective sounding frames 804 to the AP 102 according to timing information included in the sounding announcement frame 802. In this example, the STA 104-1 transmits a sounding frame 804-1 to the AP 102. Then, the STAs 104-2 and 104-3 transmit sounding frames 804-1 to the AP 102 in succession. Each sounding frame 804 includes an appropriate training signal in the PHY preamble (e.g., HE-LTF field). Each sounding frame 804 may also include UL power control information for the STA 104 transmitting the sounding frame (e.g., transmit power, power adjustment range and / or power headroom) in the PHY preamble (e.g., HE-SIG-A field). Each sounding frame 804 may be an NDP. The AP 102 obtains channel state information (e.g., gain, phase, SNR, etc.) corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 based on the training signal included in each sounding frame 804. Additionally or alternatively, the AP 102 determines quality indicators (e.g., SNR, SNIR, signal strength, etc.) corresponding to each of one or more subbands of the communication channel from each STA 104 to the AP 102. The AP 102 further identifies one or more candidate subbands for each STA 104 to be used for UL transmission.

[0088] According to a fourth embodiment of the present disclosure, the AP 102 identifies an intended use of a transmission scheme for the entire bandwidth and / or each of the one or more candidate subbands for each STA 104 based on the channel state information corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 and / or the quality indicators corresponding to one or more candidate subbands of the communication channel from each STA 104 to the AP 102. For example, the AP 102 determines whether the entire bandwidth or each one or more candidate subbands for each STA 104 should be used for UL SU-MIMO transmissions, UL MU-MIMO transmissions, or both.

[0089] According to embodiment 4 of the present disclosure, if the AP 102 determines that the entire bandwidth or the candidate subbands should be used only for UL SU-MIMO transmission by the STA, it develops a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission on the entire bandwidth or the candidate subbands in a manner similar to embodiment 1.

[0090] According to embodiment 4 of the present disclosure, if the AP 102 determines that the entire bandwidth or candidate subbands should be used only for UL MU-MIMO transmissions by the group of STAs, it develops a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmissions on the entire bandwidth or candidate subbands in a manner similar to embodiment 1.

[0091] According to embodiment 4 of the present disclosure, when the AP 102 determines that the entire bandwidth or a candidate subband should be used for UL SU-MIMO transmission by a STA or UL MU-MIMO transmission by a group of STAs, it deploys both a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission and a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmission on the entire bandwidth or candidate subband.

[0092] The AP 102 selects STAs for inclusion in a UL group for UL MU transmission based on channel state information corresponding to the entire bandwidth and / or quality indicators corresponding to one or more subbands of the communication channel obtained for at least some of the STAs 104 during the time interval 826. The AP 102 also specifies respective transmission schemes and allocates respective transmission resources (e.g., subbands for UL OFDMA) to the STAs of the UL group.

[0093] The AP 102 transmits the respective feedback frames 806 to the STAs 104 of the UL group simultaneously in a DL MU PPDU during the time interval 828. The AP 102 also transmits the respective trigger frames 808 to the STAs of the UL group (e.g., STAs 104-1 and 104-2 in this example) in the same DL MU PPDU. In this example, the AP 102 transmits a set of feedback frames 806-1 and trigger frames 808-1, a set of feedback frames 806-2 and trigger frames 808-2, and a feedback frame 806-3 to the STAs 104-1, 104-2, and 104-3, respectively, in the DL MU PPDU. It should be noted that the transmit beamforming matrix used by the AP 102 for each STA 104 of DL MU transmission is obtained in advance via a sounding procedure of DL MU transmission. The STAs 104 obtain their respective transmit beamforming matrices directly from the data of the respective feedback frames 806 for UL MU transmission.

[0094] According to embodiment 4 of the present disclosure, the trigger frame 808 and the feedback frame 806 are transmitted to the STAs of the UL group in the same DL MU PPDU, thereby improving channel efficiency compared to embodiment 3 in which the trigger frame 708 and the feedback frame 706 are transmitted separately by the AP 102 to the STAs of the UL group.

[0095] According to a fourth embodiment of the present disclosure, each trigger frame 808 causes a particular STA of the UL group to transmit data at a particular time to the AP 102. Each trigger frame 808 also includes information regarding a designated transmission scheme and / or assigned transmission resources for the particular STA of the UL group.

[0096] According to a fourth embodiment of the present disclosure, the feedback frame 806 for the specific STA includes one or more of the following: (i) an indication of one or more candidate subbands for the specific STA; (ii) intended use of a transmission scheme corresponding to each of the one or more candidate subbands for the specific STA; (iii) one or more quality indicators corresponding to each of the one or more candidate subbands for the specific STA; (iv) beamforming feedback corresponding to each of the one or more candidate subbands for the specific STA; (v) intended use of a transmission scheme corresponding to the entire bandwidth for the specific STA; (vi) one or more quality indicators corresponding to the entire bandwidth for the specific STA; (vii) beamforming feedback corresponding to the entire bandwidth for the specific STA; and (viii) power control information (e.g., a required power adjustment amount), etc.

[0097] According to the fourth embodiment of the present disclosure, what is included in the beamforming feedback corresponding to the entire bandwidth or the candidate subband for a particular STA depends on the intended use of the transmission scheme for the entire bandwidth or the candidate subband for a particular STA. If the entire bandwidth or the candidate subband must be used only for UL SU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL SU-MIMO transmission. If the entire bandwidth or the candidate subband must be used only for UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL MU-MIMO transmission. If the entire bandwidth or the candidate subband must be used for UL SU-MIMO or UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents both a transmit beamforming matrix specific to the UL SU-MIMO transmission and a transmit beamforming matrix specific to the UL MU-MIMO transmission.

[0098] During the time interval 832, the STAs of the UL group (i.e., STAs 104-1 and 104-2 in this example) transmit their respective data 810 to the AP 102 simultaneously on the entire bandwidth using their respective transmit beamforming matrices specific to UL MU-MIMO transmission on the entire bandwidth if the trigger frame 808 initiates UL MU-MIMO transmission. The STAs of the UL group transmit their respective data 810 to the AP 102 simultaneously on their respective assigned subbands using their respective transmit beamforming matrices if the trigger frame 808 initiates UL OFDMA transmission. These transmit beamforming matrices may be generated from the respective feedback frames 806 according to their respective designated transmission schemes and their respective assigned subbands. For example, if the designated transmission scheme for the STA 104-1 is UL SU-MIMO, the transmit beamforming matrix specific to UL SU-MIMO transmission on the assigned subbands for the STA 104-1 is generated directly from the corresponding data of the feedback frame 806-1.

[0099] Example 5 9 is a schematic timing diagram illustrating an example sounding procedure 900 and an example UL MU transmission based on the sounding procedure 900 according to a fifth embodiment of the present disclosure. Similar to the sounding procedure 400 of FIG. 9, the sounding procedure 900 is also an explicit sounding procedure.

[0100] The AP 102 initiates the sounding procedure 900 by transmitting a sounding announcement frame 902 to the STAs 104 during a time interval 922. The sounding announcement frame 902 includes information that coordinates the timing of when the STAs 104 transmit their respective sounding frames. For example, the payload of the sounding announcement frame 902 may indicate an ordering of the STAs 104 that are required to transmit sounding frames.

[0101] In response to receiving the sounding announcement frame 902 during the time interval 924, the STAs 104 sequentially transmit their respective sounding frames 904 to the AP 102 according to timing information included in the sounding announcement frame 902. In this example, the STA 104-1 transmits a sounding frame 904-1 to the AP 102. Then, the STAs 104-2 and 104-3 transmit their sounding frames 904-1 to the AP 102 in succession. Each sounding frame 904 includes an appropriate training signal in the PHY preamble (e.g., HE-LTF field). Each sounding frame 904 may also include UL power control information for the STA 104 transmitting the sounding frame (e.g., transmit power, power adjustment range and / or power headroom) in the PHY preamble (e.g., HE-SIG-A field). Each sounding frame 904 may be an NDP. The AP 102 obtains channel state information (e.g., gain, phase, SNR, etc.) corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 based on the training information included in each sounding frame 904. Additionally or alternatively, the AP 102 determines quality indicators (e.g., SNR, SNIR, signal strength, etc.) corresponding to each of one or more subbands of the communication channel from each STA 104 to the AP 102. The AP 102 further identifies one or more candidate subbands for each STA 104 to be used for UL transmission.

[0102] According to a fifth embodiment of the present disclosure, the AP 102 identifies an intended use of a transmission scheme for the entire bandwidth and / or each of one or more candidate subbands for each STA 104 based on the channel state information corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 and / or the quality indicators corresponding to one or more subbands of the communication channel from each STA 104 to the AP 102. For example, the AP 102 determines whether the entire bandwidth or each of the one or more candidate subbands for each STA 104 should be used for UL SU-MIMO transmission, UL MU-MIMO transmission, or both.

[0103] According to embodiment 5 of the present disclosure, if the AP 102 determines that the entire bandwidth or candidate subbands of the communication channel from the STA to the AP 102 should be used by the STA only for UL SU-MIMO transmission, the AP 102 calculates a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission on the entire bandwidth or candidate subbands in a manner similar to embodiment 1.

[0104] According to embodiment 5 of the present disclosure, if the AP 102 determines that the entire bandwidth or candidate subbands should be used only for UL MU-MIMO transmission by a group of STAs, it calculates a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmission on the entire bandwidth or candidate subbands in a manner similar to embodiment 1.

[0105] According to embodiment 5 of the present disclosure, when the AP 102 determines that the entire bandwidth or a candidate subband should be used for UL SU-MIMO transmission by a STA or UL MU-MIMO transmission by a group of STAs, it calculates both a transmit beamforming matrix for the STA specific to UL SU-MIMO transmission and a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmission on the entire bandwidth or candidate subband.

[0106] The AP 102 selects STAs for inclusion in a UL group for UL MU transmission based on channel state information corresponding to the entire bandwidth, quality indicators corresponding to one or more subbands, and / or data buffer status of the communication channel obtained for at least some of the STAs 104 during time interval 926. The AP 102 also specifies respective transmission schemes and allocates respective transmission resources (e.g., subbands for UL OFDMA) to the STAs of the UL group.

[0107] The AP 102 transmits the respective feedback frames 906 to the STAs 104 of the UL group simultaneously in a DL MU PPDU during time interval 928. In this example, the AP 102 transmits feedback frames 906-1, 906-2, and 906-3 to the STAs 104-1, 104-2, and 104-3, respectively, in a DL MU PPDU. Note that the transmit beamforming matrix used by the AP 102 for each STA 104 for DL ​​MU transmission is obtained in advance via a sounding procedure for DL ​​MU transmission. The STAs 104 obtain their respective transmit beamforming matrices directly from the data of the respective feedback frames 906 for UL MU transmission.

[0108] According to a fifth embodiment of the present disclosure, the feedback frame 906 for the specific STA includes one or more of the following: (i) an indication of one or more candidate subbands for the specific STA; (ii) intended use of a transmission scheme corresponding to each of the one or more candidate subbands for the specific STA; (iii) one or more quality indicators corresponding to each of the one or more candidate subbands for the specific STA; (iv) beamforming feedback corresponding to each of the one or more candidate subbands for the specific STA; (v) intended use of a transmission scheme corresponding to the entire bandwidth for the specific STA; (vi) one or more quality indicators corresponding to the entire bandwidth for the specific STA; (vii) beamforming feedback corresponding to the entire bandwidth for the specific STA; and (viii) power control information (e.g., a required power adjustment amount), etc.

[0109] According to embodiment 5 of the present disclosure, each feedback frame (e.g., 906-1 or 906-2 in this example) for a STA in the UL group includes trigger information to cause a particular STA in the UL group to transmit data to AP 102 at a particular time and to inform the particular STA in the UL group of a specified transmission scheme and / or assigned transmission resources.

[0110] According to embodiment 5 of the present disclosure, since separate trigger frames are not transmitted to the STAs of the UL group, channel efficiency is improved compared to embodiment 4 in which separate trigger frames 808 are transmitted by AP 102 to the STAs of the UL group.

[0111] According to the fifth embodiment of the present disclosure, what is included in the beamforming feedback corresponding to the entire bandwidth or the candidate subband for a particular STA depends on the intended use of the transmission scheme for the entire bandwidth or the candidate subband for a particular STA. If the entire bandwidth or the candidate subband must be used only for UL SU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL SU-MIMO transmission. If the entire bandwidth or the candidate subband must be used only for UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL MU-MIMO transmission. If the entire bandwidth or the candidate subband must be used for UL SU-MIMO or UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents both a transmit beamforming matrix specific to the UL SU-MIMO transmission and a transmit beamforming matrix specific to the UL MU-MIMO transmission.

[0112] During time interval 932, the STAs of the UL group (i.e., STAs 104-1 and 104-2 in this example) transmit their respective data 910 to the AP 102 simultaneously on the entire bandwidth using respective transmit beamforming matrices specific to UL MU-MIMO transmission on the entire bandwidth when trigger information included in the feedback frame 906 activates UL MU-MIMO transmission. The STAs of the UL group transmit their respective data 910 to the AP 102 simultaneously on the respective assigned subbands using respective transmit beamforming matrices that may be generated from the respective feedback frames 906 according to the respective designated transmission schemes and the respective assigned subbands when trigger information included in the feedback frame 906 activates UL OFDMA transmission. For example, if the designated transmission scheme for STA 104-1 is UL SU-MIMO, the transmit beamforming matrix specific to UL SU-MIMO transmission on the assigned subbands for STA 104-1 is generated directly from the corresponding data of the feedback frame 906-1.

[0113] Example 6 10 is a schematic timing diagram illustrating an example sounding procedure 1000 and an example cascaded DL and UL MU transmission based on the sounding procedure 1000 according to a sixth embodiment of the present disclosure. Unlike the first five embodiments that address only explicit UL sounding, the sounding procedure 1000 is an explicit bidirectional sounding procedure in which explicit DL sounding and explicit UL sounding are performed jointly in an efficient manner.

[0114] During time interval 1022, the AP 102 transmits a sounding announcement frame 1002 to the STAs 104 to initiate the sounding procedure 1000. The sounding announcement frame 1002 includes information identifying the STAs 104 that are intended participants in the sounding procedure 1000. For example, the sounding announcement frame 1002 identifies the STAs 104 by including an appropriate identifier, such as at least a portion of an association identifier (AID) corresponding to each STA 104 identified as an intended participant.

[0115] During the time interval 1024, the AP 102 transmits a sounding frame 1004, which may be an NDP, including a suitable training signal in the PHY preamble (e.g., HE-LTF field) as part of the explicit DL sounding. Each STA 104 identified by the sounding announcement frame 1002 obtains DL channel state information (e.g., gain, phase, SNR, etc.) corresponding to the entire bandwidth of the communication channel from the AP 102 and the STA 104 based on the training signal included in the sounding frame 1004. Additionally or alternatively, each STA 104 determines a DL quality indicator (e.g., SNR, SNIR, signal strength, etc.) corresponding to each of one or more sub-bands of the communication channel from the AP 102 and the STA 104. The STA 104 further identifies one or more preferred sub-bands and determines a priority order of the identified preferred sub-bands for DL ​​transmission.

[0116] The STA 104-1, which is first identified in the sounding announcement frame 1002, transmits its feedback frame 1006-1 as part of the explicit DL sounding during time interval 1026. The AP 102 receives the feedback frame 1006-1 from the STA 104-1 and subsequently transmits a respective feedback poll frame 1008 to each of the remaining STAs 104 identified by the sounding announcement frame 1002 as participants in the sounding procedure 1000. Each of the remaining STAs 104 transmits its feedback frame 1006 accordingly.

[0117] The feedback frame 1006 from the particular STA includes one or more of: (i) an indication of one or more preferred subbands identified by the particular STA; (ii) an indication of a priority order of the one or more preferred subbands identified by the particular STA; (iii) one or more DL quality indicators corresponding to each of the one or more preferred subbands identified by the particular STA; (iv) DL beamforming feedback corresponding to each of the one or more preferred subbands identified by the particular STA; (v) DL channel state information corresponding to an entire bandwidth of a communication channel between the AP 102 and the particular STA; (vi) one or more DL quality indicators corresponding to an entire bandwidth of a communication channel from the AP 102 to the particular STA; and (vii) DL beamforming feedback corresponding to an entire bandwidth of a communication channel from the AP 102 to the particular STA, etc. The beamforming feedback may be compressed beamforming feedback similar to that defined in the IEEE 802.11ac standard. Alternatively, the beamforming feedback may be another suitable form of beamforming feedback, such as uncompressed beamforming feedback.

[0118] According to the sixth embodiment of the present disclosure, the feedback frame 1006 for explicit DL sounding also serves as a sounding frame for explicit UL sounding. In other words, in addition to the training signal included in the PHY preamble (e.g., HE-LTF field) used by the receiver to demodulate the data portion of the feedback frame 1006, the feedback frame 1006 needs to include an appropriate additional training signal in the PHY preamble (e.g., a new field immediately after the HE-LTF field) to provide an additional reference for UL sounding, thereby allowing the receiver to form an estimate of additional dimensions of the channel beyond those used by the data portion of the feedback frame 1006. Also, each feedback frame 1006 can include UL power control information for the STA transmitting the feedback frame (e.g., transmit power, power adjustment range and / or power headroom) in the PHY preamble (e.g., HE-SIG-A field).

[0119] The AP 102 obtains one or more DL quality indicators and DL transmit beamforming matrices corresponding to the entire bandwidth and / or one or more subbands of the communication channel from the AP 102 to each STA 104 based on the feedback frames 1006 received by the AP 102 during the time interval 1026. For example, the AP 102 obtains the one or more DL quality indicators and / or transmit beamforming matrices for a particular STA 104 directly from the feedback frames 1006 received from the particular STA 104. Alternatively, the AP 102 determines the one or more DL quality indicators and / or transmit beamforming matrices for a particular STA 104 based on data included in the feedback frames 1006 received from the particular STA 104, e.g., based on DL channel condition information included in the feedback frames 1006 received from the particular STA 104.

[0120] Meanwhile, the AP 102 obtains UL channel state information (e.g., gain, phase, SNR, etc.) corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 based on the training signal and the additional training signal included in each feedback frame 1006. Additionally or alternatively, the AP 102 determines a UL quality indicator (e.g., SNR, SNIR, signal strength, etc.) corresponding to each of one or more subbands of the communication channel from each STA 104 to the AP 102. The AP 102 further identifies one or more candidate subbands for each STA 104 to be used for UL transmission.

[0121] According to a sixth embodiment of the present disclosure, the AP 102 identifies an intended use of a transmission scheme for the entire bandwidth and / or each of the one or more candidate subbands for each STA 104 based on the UL channel condition information corresponding to the entire bandwidth of the communication channel from each STA 104 to the AP 102 and / or the UL quality indicator corresponding to one or more candidate subbands of the communication channel from each STA 104 to the AP 102. For example, the AP 102 determines whether the entire bandwidth or each of the one or more candidate subbands for each STA 104 should be used for UL SU-MIMO transmission, UL MU-MIMO transmission, or both.

[0122] According to embodiment 6 of the present disclosure, if the AP 102 determines that the entire bandwidth or the candidate subbands should be used only for UL SU-MIMO transmission by the STA, it develops a UL transmit beamforming matrix for the STA specific to UL SU-MIMO transmission on the entire bandwidth or the candidate subbands in a manner similar to embodiment 1.

[0123] According to embodiment 6 of the present disclosure, if the AP 102 determines that the entire bandwidth or candidate subbands should be used only for UL MU-MIMO transmissions by the group of STAs, it develops a transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmissions on the entire bandwidth or candidate subbands in a manner similar to embodiment 1.

[0124] According to embodiment 6 of the present disclosure, when the AP 102 determines that the entire bandwidth or a candidate subband should be used for UL SU-MIMO transmission by a STA or UL MU-MIMO transmission by a group of STAs, it deploys both a UL transmit beamforming matrix for the STA specific to UL SU-MIMO transmission and a UL transmit beamforming matrix for each STA in the group specific to UL MU-MIMO transmission on the entire bandwidth or candidate subband.

[0125] During the time interval 1028, the AP 102 selects STAs for inclusion in a DL group for DL ​​MU transmission based on DL channel state information corresponding to an overall bandwidth and / or DL ​​quality indicator corresponding to one or more subbands of a communication channel acquired during explicit DL sounding for at least some of the STAs 104. The AP 102 also assigns respective transmission resources (e.g., subbands for DL ​​OFDMA) to the STAs 104 including the STAs of the DL group, specifying respective transmission schemes. Meanwhile, the AP 102 selects STAs for inclusion in a UL group for UL MU transmission based on UL channel state information corresponding to an overall bandwidth and / or UL quality indicator corresponding to one or more subbands of a UL communication channel acquired during explicit UL sounding for at least some of the STAs 104. The AP 102 also assigns respective transmission resources (e.g., subbands for UL OFDMA) to the STAs of the UL group, specifying respective transmission schemes.

[0126] During the time interval 1030, the AP 102 transmits the respective feedback frames 1010 to the STAs 104 simultaneously on the respective transmission resources via the DL MU PPDU using the respective transmit beamforming matrices that may be generated from the feedback frame 1006 according to the respective designated transmission schemes. For example, if the designated transmission scheme for the STA is DL SU-MIMO, the transmit beamforming matrix specific to the DL SU-MIMO transmission on the assigned subbands for the STA is generated directly or indirectly from the corresponding data of the feedback frame 1006. The DL MU PPDU includes information on the designated transmission scheme and / or the assigned transmission resource for each STA 104 in the PHY preamble (e.g., HE-SIG-B field). The AP 102 also transmits the respective data 1012 to the STAs 104 of the DL group (e.g., STAs 104-1 and 104-3 in this example) and transmits the respective trigger frames 1014 to the STAs of the UL group (e.g., STAs 104-1 and 104-2 in this example) in the same DL MU PPDU. In this example, the AP 102 transmits a set of a feedback frame 1010-1, a data 1012-1, and a trigger frame 1014-1, a set of a feedback frame 1010-2 and a trigger frame 1014-2, and a set of a feedback frame 1010-3 and a data 1012-3 to the STAs 104-1, 104-2, and 104-3, respectively, in a DL MU PPDU. The STAs 104 derive their respective transmit beamforming matrices for UL MU transmissions directly from the data of their respective received feedback frames 1010.

[0127] According to a sixth embodiment of the present disclosure, the feedback frame 1010 for a particular STA includes one or more of the following: (i) an indication of one or more candidate subbands for the particular STA; (ii) intended use of a transmission scheme corresponding to each of the one or more candidate subbands for the particular STA; (iii) one or more quality indicators corresponding to each of the one or more candidate subbands for the particular STA; (iv) beamforming feedback corresponding to each of the one or more candidate subbands for the particular STA; (v) intended use of a transmission scheme corresponding to the entire bandwidth for the particular STA; (vi) one or more quality indicators corresponding to the entire bandwidth for the particular STA; (vii) beamforming feedback corresponding to the entire bandwidth for the particular STA; and (viii) power control information (e.g., a required power adjustment amount), etc.

[0128] According to the sixth embodiment of the present disclosure, what is included in the beamforming feedback corresponding to the entire bandwidth or the candidate subband for a particular STA depends on the intended use of the transmission scheme for the entire bandwidth or the candidate subband for a particular STA. If the entire bandwidth or the candidate subband is to be used only for UL SU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL SU-MIMO transmission. If the entire bandwidth or the candidate subband is to be used only for UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents a transmit beamforming matrix specific to the UL MU-MIMO transmission. If the entire bandwidth or the candidate subband is to be used for UL SU-MIMO or UL MU-MIMO transmission, the beamforming feedback corresponding to the entire bandwidth or the candidate subband represents both a transmit beamforming matrix specific to the UL SU-MIMO transmission and a transmit beamforming matrix specific to the UL MU-MIMO transmission.

[0129] According to the sixth embodiment of the present disclosure, each trigger frame 1014 causes a specific STA of the UL group to transmit data to the AP 102 at a specific time, and each trigger frame 1014 includes information regarding a designated transmission scheme and / or an assigned transmission resource for the specific STA of the UL group.

[0130] During the time interval 1032, the STAs of the UL group (i.e., STAs 104-1 and 104-2 in this example) simultaneously transmit their respective data 1016 to the AP 102 on the entire bandwidth using their respective transmit beamforming matrices specific to UL MU-MIMO transmission on the entire bandwidth if the trigger frame 1014 initiates UL MU-MIMO transmission. The STAs of the UL group simultaneously transmit their respective data 1016 to the AP 102 on the respective assigned subbands using their respective transmit beamforming matrices that may be generated directly from the respective feedback frames 1010 according to their respective designated transmission schemes and their respective assigned subbands if the trigger frame 1014 initiates UL OFDMA transmission. For example, if the designated transmission scheme for the STA 104-1 is UL SU-MIMO, the transmit beamforming matrix specific to UL SU-MIMO transmission on the assigned subbands for the STA 104-1 is generated directly from the corresponding data of the feedback frame 1010-1.

[0131] According to the sixth embodiment of the present disclosure, the sounding procedure 1000 starts with an explicit DL sounding, and then an explicit UL sounding follows. The feedback frame 1006 sent by the STA 104 to the AP 102 during the explicit DL sounding also serves as a sounding frame for the explicit UL sounding. Since a dedicated sounding frame is not required for the explicit UL sounding, the sounding procedure 1000 as an explicit bidirectional sounding has better channel efficiency than the sounding procedure in which the explicit DL sounding and the explicit UL sounding are performed separately.

[0132] According to the present disclosure, the WLAN 100 can support multiple sounding procedures to increase the flexibility of the system. For example, the WLAN 100 can support three kinds of sounding procedures: DL sounding procedure, UL sounding procedure, and bidirectional sounding procedure. As a result, the sounding announcement frame transmitted by the AP 102 to the STA 104 initiating the sounding procedure can include information indicating the type of the sounding procedure. In the example of FIG. 4, FIG. 6, FIG. 7, FIG. 8, or FIG. 9, the sounding announcement frame 402, 602, 702, 802, or 902 can include information to indicate that the sounding procedure 400, 600, 700, 800, or 900 is a UL sounding procedure. In the example of FIG. 10, the sounding announcement frame 1002 can include information to indicate that the sounding procedure 1000 is a bidirectional sounding procedure.

[0133] <Wireless communication method> 11 is a flow chart illustrating a first example method 1100 performed by a first communication device for performing sounding with a plurality of second communication devices for UL MU transmissions in accordance with the present disclosure. For illustrative purposes only, the method 1100 is described with respect to FIGS. 4, 6, 7, 8, and 9 and is described in the context of the first communication device as an AP and the second communication device as a STA. However, the first communication device may be any suitable communication device other than an AP, such as a node of a peer-to-peer network, while the second communication device may be any suitable communication device other than a STA, such as a node of a peer-to-peer network.

[0134] In step 1102, the AP obtains, for each of the plurality of STAs, channel state information and one or more quality indicators corresponding to the entire bandwidth and / or each of one or more sub-bands of an OFDM communication channel associated with the STA. Step 1102 includes transmitting one or more sounding announcement frames to the plurality of STAs, receiving a sounding frame from each of the plurality of STAs, and obtaining channel state information and one or more quality indicators corresponding to the entire bandwidth and / or each of one or more sub-bands for each of the plurality of STAs based on the sounding frame received from the STA. In the example of FIG. 4 or FIG. 6, the AP 102 transmits a respective sounding announcement frame 402 or 602 to request the STAs 104-1, 104-2, and 104-3 to transmit a respective sounding frame 404 or 604. In the example of FIG. 7, 8 or 9, the AP 102 transmits a single sounding announcement frame 702, 802 or 902 requesting the STAs 104-1, 104-2 and 104-3 to transmit their respective sounding frames 704, 804 or 904.

[0135] In step 1104, the AP identifies one or more candidate subbands for the STA based on the quality indicator obtained for each STA of the multiple STAs.

[0136] In step 1106, the AP develops a transmit beamforming matrix corresponding to the entire bandwidth and / or each of the one or more candidate subbands for each of the multiple STAs based on the channel state information and quality indicators obtained for the multiple STAs. Step 1106 includes identifying a transmission scheme for the entire bandwidth and / or each of the one or more candidate subbands for each of the multiple STAs based on the quality indicators obtained for the multiple STAs, and developing a transmit beamforming matrix for each of the one or more candidate subbands determined by an intended use of the entire bandwidth and / or each of the multiple STAs based on the channel state information and quality indicators obtained for the multiple STAs. Step 1106 may also include calculating a required power adjustment for each of the multiple STAs.

[0137] According to method 1100, if the entire candidate subband or bandwidth is to be used only for UL SU-MIMO transmissions, a transmit beamforming matrix specific to SU-MIMO transmissions is deployed for the entire candidate subband or bandwidth. If the entire candidate subband or bandwidth is to be used only for UL MU-MIMO transmissions, a transmit beamforming matrix specific to MU-MIMO transmissions is deployed for the entire candidate subband or bandwidth. If the entire candidate subband or bandwidth is to be used for UL SU-MIMO or MU-MIMO communications, a transmit beamforming matrix specific to SU-MIMO transmissions and a transmit beamforming matrix specific to MU-MIMO transmissions are deployed for the entire candidate subband or bandwidth.

[0138] In step 1108, the AP selects a group of STAs for inclusion in a UL group for UL MU communication based on the quality indicators obtained for at least some of the plurality of STAs, and transmits respective feedback information to the plurality of STAs and respective trigger information to the STAs of the UL group. A group includes two or more STAs of the plurality of STAs. In the example of FIG. 4, FIG. 6, FIG. 7, FIG. 8 or FIG. 9, the AP 102 selects STAs 104-1 and 104-2 for inclusion in the UL group. The feedback information is described above with respect to FIG. 5. The trigger information for the STAs of the UL group causes the STAs to transmit to the AP with other STAs of the UL group at the same time at a particular time. The trigger information for the STAs of the UL group includes information regarding a designated transmission scheme and / or an assigned transmission resource.

[0139] According to the method 1100, in one embodiment, feedback information for each STA is included in a feedback frame sent to the STA, and trigger information for each STA of the UL group is included in a feedback frame sent to the STA. The feedback frames are transmitted to multiple STAs by the AP simultaneously via a DL MU PPDU. In the example of FIG. 9, the AP 102 simultaneously transmits a feedback frame 906-1 including feedback information and trigger information for the STA 104-1, a feedback frame 906-2 including feedback information and trigger information for the STA 104-2, and a feedback frame 906-3 including feedback information and trigger information for the STA 104-3.

[0140] According to the method 1100, in one embodiment, feedback information for each STA is included in a feedback frame sent to the STA, and trigger information for the STAs of the UL group is included in a trigger frame. The feedback frame is transmitted simultaneously to multiple STAs by the AP via a DL MU PPDU before transmitting the trigger frame to the STAs of the UL group. In the example of FIG. 4, the AP 102 transmits feedback frames 406 to the STAs 104 sequentially. In the example of FIG. 6 or FIG. 7, the AP 102 transmits feedback frames 606 or 706 to the STAs 104 simultaneously. Then, the AP 102 transmits trigger frames 408, 608 or 708 to the STAs of the UL group.

[0141] According to the method 1100, in one embodiment, feedback information for each STA is included in a feedback frame sent to the STA, and trigger information for each STA of the UL group is included in a trigger frame sent to the STA. A set of feedback frames and trigger frames sent to each STA of the UL group and feedback frames sent to each of the STAs not in the UL group are simultaneously transmitted to the multiple STAs via a DL MU PPDU. In the example of FIG. 8, the AP 102 simultaneously transmits a set of feedback frames 806-1 and trigger frames 808-1 to STA 104-1, a set of feedback frames 806-2 and trigger frames 808-2 to STA 104-2, and a feedback frame 806-3 to STA 104-3.

[0142] In step 1110, the AP receives simultaneous transmissions from the STAs of the UL group in response to the trigger information transmitted in step 1108. The simultaneous transmissions received in step 1110 are transmitted by the STAs of the UL group using a transmit beamforming matrix generated directly from data included in the feedback information transmitted by the AP to the STAs of the UL group in step 1108. FIG. 12 is a flow chart illustrating a first exemplary method 1200 performed by one of a plurality of second communication devices to perform sounding with the first communication device for UL MU transmission according to the present disclosure. For illustrative purposes only, the method 1200 is described with respect to FIGS. 4, 6, 7, 8 and 9 and is described in the context of the first communication device as an AP and the second communication device as a STA. However, the first communication device may be any suitable communication device other than an AP, such as a node of a peer-to-peer network, while the second communication device may be any suitable communication device other than a STA, such as a node of a peer-to-peer network.

[0143] In step 1202, the STA transmits a sounding frame to the AP. Step 1202 includes receiving a sounding announcement frame from the AP and transmitting a sounding frame to the AP in response to the received sounding announcement frame. For example, in the example of FIG. 4, FIG. 6, FIG. 7, FIG. 8 or FIG. 9, the STA 104-1 transmits a sounding frame 404-1, 604-1, 704-1, 804-1 or 904-1 to the AP 102 in response to receiving the sounding announcement frame 402-1, 602-1, 702, 802 or 902.

[0144] In step 1204, the STA receives feedback information and trigger information from the AP. The feedback information is described above with respect to FIG. 5. The trigger information for the STA causes the STA to transmit simultaneously to the AP with one or more other STAs at a particular time. The trigger information for the STA also includes information regarding a designated transmission scheme and / or an assigned transmission resource.

[0145] According to the method 1200, in one embodiment, the feedback information for the STA is included in a feedback frame sent to the STA that also includes trigger information for the STA. The STA receives the feedback information and the trigger information simultaneously. In the example of FIG. 9, the STA 104-1 receives the feedback frame 906-1 that includes the feedback information and the trigger information.

[0146] According to the method 1200, in one embodiment, feedback information for the STA is included in a feedback frame sent to the STA, and trigger information for the STA is included in a trigger frame sent to the STA. The feedback frame and the trigger frame are received separately by the STA. In the example of FIG. 4, FIG. 6, or FIG. 7, the feedback frame 406-1, 606-1, or 706-1 is received by the STA 104-1 before the trigger frame 408, 608, or 708. Alternatively, a set of feedback frames and trigger frames is received by the STA. In the example of FIG. 8, the STA 104-1 receives a set of feedback frame 806-1 and trigger frame 808-1.

[0147] In step 1206, the STA generates a transmit beamforming matrix for the UL MU transmission based on the received feedback information and the trigger information. Step 1206 includes identifying a designated transmission scheme and an assigned transmission resource based on the received trigger information, and generating a transmit beamforming matrix for the UL MU transmission directly from the corresponding data of the received feedback information based on the designated transmission scheme and the assigned transmission resource.

[0148] According to method 1200, if the receiving trigger information indicates UL MU-MIMO transmission on the entire bandwidth, a transmit beamforming matrix specific to the UL MU-MIMO transmission on the entire bandwidth is generated directly from the corresponding data of the receiving feedback information. If the receiving trigger information indicates UL MU-MIMO transmission on the assigned subbands, a transmit beamforming matrix specific to the UL MU-MIMO transmission on the assigned subbands is generated directly from the corresponding data of the receiving feedback information. If the receiving trigger information indicates UL SU-MIMO transmission on the assigned subbands, a transmit beamforming matrix specific to the UL SU-MIMO transmission on the assigned subbands is generated directly from the corresponding data of the receiving feedback information.

[0149] In step 1208, in response to the trigger information, the STA transmits data of the assigned transmission resource simultaneously with one or more other STAs according to the AP using the transmit beamforming matrix generated in step 1206.

[0150] 13 is a flow chart illustrating a second example method 1300 performed by a first communication device to perform sounding with multiple second communication devices for cascaded DL and UL MU transmissions according to the present disclosure. For illustrative purposes only, the method 1300 is described with reference to FIG. 10 and in the context of the first communication device as an AP and the second communication device as a STA. However, the first communication device may be any suitable communication device other than an AP, such as a node of a peer-to-peer network, while the second communication device may be any suitable communication device other than a STA, such as a node of a peer-to-peer network.

[0151] In step 1302, the AP transmits the sounding announcement frame to the STAs before transmitting the sounding frame to them as part of the explicit DL sounding. In the example of FIG. 10, the AP 102 transmits a sounding announcement frame 1002 to the STAs 104-1, 104-2, and 104-3, followed by a sounding frame 1004.

[0152] In step 1304, the AP receives respective feedback frames for explicit DL sounding from the STAs that also serve as respective sounding frames for explicit UL sounding. In the example of FIG. 10, the AP 102 receives respective feedback frames 1006 from the STAs 104-1, 104-2, and 104-3. From the feedback frame data, the AP obtains DL channel state information and one or more DL quality indicators corresponding to the entire bandwidth and / or each of one or more preferred subbands for each of the multiple STAs.

[0153] In step 1306, as part of the explicit UL sounding, the AP obtains UL channel state information and one or more UL quality indicators corresponding to the entire bandwidth and / or each of one or more subbands for each of the multiple STAs based on the training signal and additional training signals included in the feedback frame received from the STAs.

[0154] In step 1308, the AP identifies one or more candidate subbands for the STAs based on the UL quality indicators obtained for each STA of the multiple STAs.

[0155] In step 1310, the AP develops a transmit beamforming matrix for the entire bandwidth and / or each of one or more candidate subbands for each of the multiple STAs based on the UL channel state information and UL quality indicators obtained for the multiple STAs. Step 1310 includes identifying an intended use of a transmission scheme for the entire bandwidth and / or each of one or more candidate subbands for each of the multiple STAs based on the UL quality indicators obtained for the multiple STAs, and developing a transmit beamforming matrix for each of the one or more candidate subbands determined by the intended use of the entire bandwidth and / or each of the transmission schemes for each of the multiple STAs based on the UL channel state information and UL quality indicators obtained for the multiple STAs. Step 1310 may also include calculating a required power adjustment for each of the multiple STAs.

[0156] According to method 1300, if the entire candidate subband or bandwidth is to be used only for UL SU-MIMO transmissions, a transmit beamforming matrix specific to SU-MIMO transmissions is deployed for the entire candidate subband or bandwidth. If the entire candidate subband or bandwidth is to be used only for UL MU-MIMO transmissions, a transmit beamforming matrix specific to MU-MIMO transmissions is deployed for the entire candidate subband or bandwidth. If the entire candidate subband or bandwidth is to be used for UL SU-MIMO or MU-MIMO communications, both a transmit beamforming matrix specific to SU-MIMO transmissions and a transmit beamforming matrix specific to MU-MIMO transmissions are deployed for the entire candidate subband or bandwidth.

[0157] In step 1312, the AP selects a group of STAs for inclusion in a UL group for UL MU transmission based on the UL quality indicators obtained for at least some of the plurality of STAs. The AP also selects a group of STAs for inclusion in a DL group for DL ​​MU transmission based on the DL quality indicators obtained for at least some of the plurality of STAs. A DL or UL group includes two or more STAs of the plurality of STAs. The AP transmits respective feedback information to the plurality of STAs, respective DL data to the STAs of the DL group, and respective trigger information to the STAs of the UL group. In the example of FIG. 10, the AP 102 selects STAs 104-1 and STA 104-3 for inclusion in the DL group and selects STAs 104-1 and STA 104-2 for inclusion in the UL group. The feedback information is described above with respect to FIG. 5. The trigger information for the STAs of the UL group causes the STAs to transmit simultaneously to the AP with other STAs of the UL group at a particular time. The trigger information for the STAs of the UL group also includes information regarding a designated transmission scheme and / or assigned transmission resources.

[0158] According to the method 1300, in one embodiment, feedback information for each STA is included in a feedback frame sent to the STA, and trigger information for each STA in the UL group is included in a trigger frame sent to the STA. The set of feedback frames, DL data and trigger frames sent to each STA in the DL and UL groups, feedback frames and DL data sent to each STA in the DL group but not in the UL group, and feedback frames sent to each STA that is not in the UL or DL ​​group are simultaneously transmitted to multiple STAs via a DL MU PPDU. In the example of FIG. 10, the AP 102 simultaneously transmits a set of feedback frame 1010-1, DL data 1012-1 and trigger frame 1014-1 to STA 104-1, a set of feedback frame 1010-2 and trigger frame 1014-2 to STA 104-2, and a set of feedback frame 1010-3 and DL data 1012-3 to STA 104-3.

[0159] In step 1314, the AP receives simultaneous transmissions from the STAs of the UL group in response to the trigger information transmitted in step 1312. The simultaneous transmissions received in step 1314 were transmitted by the STAs of the UL group using transmit beamforming matrices that were generated directly from data included in the feedback information transmitted by the AP to the STAs of the UL group in step 1314.

[0160] 14 is a flow chart illustrating a second example method 1400 performed by one of a plurality of second communication devices to perform sounding with a first communication device for UL MU transmission according to the present disclosure. For illustrative purposes only, the method 1400 is described with respect to FIG. 10 and in the context of the first communication device as an AP and the second communication device as a STA. However, the first communication device may be any suitable communication device other than an AP, such as a node of a peer-to-peer network, while the second communication device may be any suitable communication device other than a STA, such as a node of a peer-to-peer network.

[0161] In step 1402, the STA receives a sounding frame from the AP for explicit DL sounding after receiving a sounding announcement frame from the AP initiating the sounding procedure. In the example of FIG. 10, the STA 104-1 receives a sounding frame 1004 from the AP 102 after receiving a sounding announcement frame 1002.

[0162] In step 1404, the STA transmits a feedback frame for explicit DL sounding to the AP in response to receiving the sounding frame that also serves as the sounding frame for explicit UL sounding in step 1402. For example, in the example of FIG. 10, STA 104-1 transmits feedback frame 1006-1 to AP 102 that is used for both explicit DL sounding and explicit UL sounding.

[0163] In step 1406, the STA receives feedback information for explicit UL sounding and trigger information from the AP. The feedback information is described above with respect to FIG. 5. The trigger information for the STA causes the STA to transmit to the AP simultaneously with one or more other STAs at a particular time. The trigger information for the STA also includes information regarding a designated transmission scheme and / or assigned transmission resources.

[0164] According to the method 1400, in one embodiment, the feedback information for the STA is included in a feedback frame sent to the STA, and the trigger information for the STA is included in a trigger frame sent to the STA. The set of feedback frames, trigger frames and / or DL ​​data is received by the STA. In the example of FIG. 10, the STA 104-1 receives the set of feedback frame 1010-1, DL data 1012-1 and trigger frame 1014-1.

[0165] In step 1408, the STA generates a transmit beamforming matrix for the UL MU transmission based on the received feedback information and the trigger information. Step 1408 includes identifying a designated transmission scheme and an assigned transmission resource based on the received trigger information, and generating a transmit beamforming matrix for the UL MU transmission directly from corresponding data of the received feedback information based on the designated transmission scheme and the assigned transmission resource.

[0166] According to method 1400, if the receiving trigger information indicates UL MU-MIMO transmission on the entire bandwidth, a transmit beamforming matrix specific to the UL MU-MIMO transmission on the entire bandwidth is generated directly from the corresponding data of the receiving feedback information. If the receiving trigger information indicates UL MU-MIMO transmission on the assigned subbands, a transmit beamforming matrix specific to the UL MU-MIMO transmission on the assigned subbands is generated directly from the corresponding data of the receiving feedback information. If the receiving trigger information indicates UL SU-MIMO transmission on the assigned subbands, a transmit beamforming matrix specific to the UL SU-MIMO transmission on the assigned subbands is generated directly from the corresponding data of the receiving feedback information.

[0167] In step 1410, in response to the trigger information, the STA transmits UL data of the assigned transmission resource simultaneously with one or more other STAs according to the AP using the transmit beamforming matrix generated in step 1408.

[0168] <Access point configuration> FIG. 15 is a block diagram showing an exemplary configuration of AP102 according to the present disclosure. AP102 includes a host processor 1502 coupled to a network interface 1504. The network interface 1504 includes a MAC (Media Access Control) processor 1506 and a PHY processor 1508. The PHY processor 1508 is coupled to a plurality of antennas 1510. The network interface 1504 (e.g., MAC processor 1506 and / or PHY processor 1508) is configured to perform a sounding procedure with the STA104 and communicate data to the STA104 according to the above-described embodiments.

[0169] <Configuration of STA> FIG. 16 is a block diagram showing an exemplary configuration of STA104 according to the present disclosure. STA104 includes a host processor 1602 coupled to a network interface 1604. The network interface 1604 includes a MAC processor 1606 and a PHY processor 1608. The PHY processor 1608 is coupled to one or more antennas 1610. The network interface 1604 (e.g., MAC processor 1606 and / or PHY processor 1608) is configured to perform a sounding procedure with the AP102 and communicate data to the AP102 according to the above-described embodiments.

Industrial Applicability

[0170] The present disclosure can be applied to a method of performing sounding for UL MU transmission in a wireless communication system.

Description of Reference Numerals

[0171] 1502 Host processor 1504 Network interface 1506 MAC processor 1508 PHY processor 1510 Antenna 1602 Host processor 1604 Network interface 1606 MAC Processor 1608 PHY Processor 1610 Antenna

Claims

1. receiving a sounding signal; generating first beamforming feedback information based on the sounding signal; transmitting the first beamforming feedback information of the sounding signal; The first beamforming feedback information is transmitted together with the second beamforming feedback information by multi-user transmission; the multi-user transmission is performed over a plurality of communication links, including a first communication link and a second communication link; the first beamforming feedback information corresponds to the first communication link, and the second beamforming feedback information corresponds to the second communication link; The first beamforming feedback information and the second beamforming feedback information are time-multiplexed in the multi-user transmission and transmitted simultaneously. Integrated circuits.

2. The first beamforming feedback information includes subband indication information; The first beamforming feedback information corresponds to an entire bandwidth or one or more subbands, and the one or more subbands are indicated by the subband indication information.

10. The integrated circuit of claim 1.

3. The first beamforming feedback information includes first power control information.

10. The integrated circuit of claim 1.

4. The first beamforming feedback information corresponds to a plurality of subbands including the one or more subbands, and the subband indication information indicates the plurality of subbands.

3. The integrated circuit of claim 2.

5. The first beamforming feedback information includes a plurality of subfields including the subband indication information, the plurality of subfields indicating one or more tones corresponding to frequency domain positions of the plurality of subbands.

5. The integrated circuit of claim 4.

6. the one or more tones correspond to a width of the one or more subbands.

6. The integrated circuit of claim 5.

7. the one or more subbands being resource units of orthogonal frequency division multiple access (OFDMA) transmission.

3. The integrated circuit of claim 2.

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