Patent ID: 12200529

It will be noted that throughout the appended drawings, like features are identified by like reference numerals.

DETAILED DESCRIPTION

As discussed earlier, in future systems (e.g., future wireless local area networks (WLANs)), the number of coordinated APs, the number of antennas at transmitters and receivers, and the operation bandwidth are likely to increase. In such environments, using existing sounding protocols, e.g., in 802.11, may result in relatively large airtime overhead for CSI feedback. Accordingly, using existing channel sounding protocols, in future WLANs, may further lead to increased overhead and complexity. For example, collection of CSI at the AP (e.g., when the CSI is estimated in STAs until the CSI is fully or almost fully collected in the AP), using existing channel sounding may cause increased overhead and require increased complexity.

CSI may reflect the wireless signal propagation characteristics for a channel between a transmitter and a receiver at certain carrier frequencies, as may be appreciated by a person skilled in the art. CSI may represent how an electromagnetic signal propagates from a transmitter to a receiver and the combined effect of scattering, fading, and power decay with distance of the signal.

Using existing channel sounding protocols for fast changing channels (e.g., channels with fast-changing signal environments) may lead to collection of CSI that are outdated or inaccurate, or both. Such outdated and inaccurate information may be problematic when the AP conducts further operations with the associated STAs.

In addition, existing channel sounding protocols may lack flexibility that may be needed under different channel conditions. For example, in Wi-Fi scenarios, some user STAs are semi-static, and thus, use of routine and static CSI feedback (based on existing channel sounding protocol) may be unnecessary.

Accordingly, enhanced channel sounding protocols are desired to obviate or mitigate one or more limitations described.

Embodiments described herein may provide for an enhanced channel sounding protocol that is adaptive to the dynamic and STA-specific channel conditions in Wi-Fi networks. Further, embodiment described herein may provide for an enhanced channel sounding protocol that can reduce signaling overhead of channel sounding while ensuring accuracy of CSI.

Embodiments described herein may provide for enhanced CSI gathering operations that consider channel-related information gathering at different levels based on latency tolerance of the information to be gathered. In some embodiments, delayed channel feature information (CFI) feedback can be piggybacked with a PPDU that carries data payload. Such embodiments may reduce signaling overhead.

Embodiment described herein may further consider multiple CSI compression schemes that may be needed for taking advantage of channel's feature, the details of which are described herein.

Embodiments described herein may provide for enhanced channel information gathering schemes that are based on the latency tolerance of channel information to be gathered. In some embodiments, the channel information gathering scheme can be based on an opportunistic CFI feedback. In opportunistic CFI feedback schemes, the sending of CFI feedback can be based on a trigger condition set by an AP. For example, when channel conditions satisfy the trigger condition, the STA subject to the trigger condition is to send the CFI feedback. In some embodiments, the trigger condition can be based on a substantial change of the channel conditions. In some embodiments, the trigger condition can be based on any appropriate change of the channel conditions.

In some embodiments, the channel information gathering scheme can be based on a delayed CFI feedback. For example, delayed CFI can be transmitted by piggybacking in the uplink data payload.

In 802.11be, CSI for single user (SU) multiple-input multiple-output (MIMO) or multi-user (MU) MIMO beamforming can be acquired through channel sounding protocols.

CSI gathering schemes can be is used to evaluate signal transmission environment. For example, CSI gathering schemes can be used for evaluating signal transmission environment for SU-MIMO or MU-MIMO OFDMA transmissions. Before downlink (DL) beamforming transmissions, an AP may need to have some knowledge of CSI of each active user STA. Upon obtaining such knowledge, the AP can then send a null data packet announcement (NDPA) frame followed by a null data packet (NDP).

FIG.1illustrates an EHT non-trigger-based (non-TB) sounding sequence procedure. The sounding sequence procedure100may be similar to the EHT non-TB sounding sequence in IEEE 802.11be D1.0, FIG. 35-17. The procedure100may comprise an EHT beamformer102initiating a sounding sequence (i.e., the procedure100) with a single EHT beamformee104. The EHT beamformer can be an AP, for example. The EHT beamformer102initiates the sounding sequence by sending an EHT NDPA frame106to the EHT beamformee104. The EHT beamformee can be a STA for example. The EHT NDPA frame106can indicate or carry the address information of a single STA (e.g., the EHT beamformee).

The procedure may further include, short interframe spacing (SIFS) time units after sending the EHT NDPA106, EHT beamformer102sending an EHT sounding NDP108to the EHT beamformee104. SIFS time units after receiving the EHT sounding NDP108, the EHT beamformee104can send a channel quality information (CQI) feedback110(EHT compressed beamforming/CQI) to the EHT beamformer102.

FIG.2illustrates an EHT TB sounding sequence procedure. The sounding sequence procedure200may be similar to the EHT TB sounding sequence in IEEE 802.11be D1.0,FIG.35-18. The sounding sequence procedure200may apply to the case of DL MU-MIMO. The procedure200may involve soliciting feedback from multiple STAs204(e.g., a plurality of EHT beamformees). The procedure200may include, sending, by the EHT beamformer102, an EHT NDPA frame206to each of the plurality of EHT beamformees204. The EHT NDPA frame206can include more than one STA Info fields for indicating the address information of each of the plurality of EHT beamformees204. The EHT NDPA frame206can further include an RA field set to the broadcast address.

The procedure my further include, short interframe spacing (SIFS) time units after sending the EHT NDPA206, EHT beamformer102can send an EHT sounding NDP208to each of the plurality of EHT beamformees204. SIFS time units thereafter, the EHT beamformer102can send a Beamforming Report Poll (BFRP) trigger frame210to each of the plurality of EHT beamformees. In response to receiving the BFRP trigger frame210, SIFS time units thereafter, each of the plurality of the EHT beamformee204can send its compressed beamforming reports (e.g., EHT compressed beamforming/CQI) to the EHT beamformer102. A person skilled in the art may appreciated that the sending of the BFRP trigger frame210and the receiving of the compressed beamforming reports may involve one or more sequences.

As described herein, existing sounding protocols may be inadequate for future systems (e.g., future WLANs) as these protocols have a number of limitations. Embodiments may provide enhanced channel sounding protocols that obviate or mitigate one or more limitation of prior arts.

Embodiments described herein may provide for an adaptive channel sounding mechanism or protocol that may allow one or more beamformees to feedback channel information based on latency tolerance of the channel information (or channel-related information) to be gathered. Embodiments described herein may provide an enhanced channel sounding protocol that improves the accuracy and timeliness of channel information gathering at the AP side while minimizing the overhead of channel sounding.

In some Wi-Fi scenarios, change in channel information can occur over a large timescale (e.g., hundreds of milliseconds). The change in channel information can be substantial or of substantial nature. Such ‘slow-changing’ channel information can be viewed as having relatively high tolerance with respect to feedback delay, indicating that the channel information has not undergone a substantial change or a change of substantial nature.

Based on the tolerance nature of the channel information with respect to feedback delay, channel information can be categorized as long-term channel information or real-time channel information. The long-term channel information can be referred to as delayed CFI (e.g., channel information that have high tolerance with respect to feedback delay (i.e., slow changing channel information). The real-time channel information may refer to information, such as channel state information (CSI), that needs to be fed back immediately or soon after channel sounding, which may be referred to as real-time CSI.

In some embodiments described herein, channel feature information can be collected by delayed feedback, in which, one or more STAs can opportunistically piggyback the CFI in the uplink payload (to the AP) once a trigger condition is satisfied. CFI that is collected by delayed feedback can be referred to as delayed CFI. As may be appreciated by a person skilled in the art, CFI can include information indicative of one or more of: CQI, CSI, channel frequency response (CFR) in frequency domain, channel impulse response (CIR) in time domain, channel feature parameters, and other channel-related information. Channel feature parameters can include information indicative of one or more of: a level of channel variation, a level of frequency-domain correlation, and a temporary sparsity level of CIR.

On the other hand, real-time CSI can be fed back, by one or more STAs to the AP, using any appropriate channel sounding protocol.

Compared with the real-time CSI feedback, the overhead in the delayed feedback (comprising CFI) may be lower since the feedback information in the delayed feedback can be carried with an uplink (UL) data payload.

FIG.3illustrates a procedure for adaptive channel sounding feedback, according to an embodiment of the present disclosure. The CSI gathering procedure300can comprise an immediate or a real-time CSI feedback portion330which may be based on collecting real-time CSI, at time t, for example. The procedure300can further comprise a delayed CFI feedback portion335, which may be based on collecting CFI. In some embodiments, the procedure300can further comprise a second immediate or real-time CSI feedback portion340, at time t+T.

As further described herein, in the real-time CSI feedback portion330, in response to receiving the BFRP trigger frame310from the AP302, each of one or more STAs304can send real-time CSI to the AP302using a beamforming report (BR) frame (e.g., one or more BF frames312).

Similarly, in the delayed CFI feedback portion335, in response to receiving the BFRP trigger frame310from the AP302, one or more of the STAs304can further feedback CFI by piggybacking the CFI in an uplink PPDU.

In an embodiment, the adaptive channel sounding procedure300includes, initiating, by the AP302, the channel sounding procedure. The AP302can initiate the channel sounding procedure by sending an NDPA306to one or more STAs304. The NDPA frame306can include information indicative of address of one or more target STAs (e.g., the one or more STAs304) for channel measurement.

The procedure300further includes, SIFS time units after sending the NDPA306, sending, by the AP302, an NDP frame308to the one or more STAs304. The NDP frame308can indicate to each one of the one or more STAs304to estimate the downlink channels between the STA and the AP302.

In some embodiments, each STA of the one or more STAs304can leverage the preamble in the NDP frame308to estimate the complex-valued channel vectors between the AP302and itself.

The measured Channel Frequency Response (CFR) between an AP (e.g., AP302) and STA m (e.g., a STA of the one or more STAs304) on the kthsubcarrier can be denoted as Hm,k∈NT×NRwhere NTand NRare the number of transmit antennas and the number of receive antennas, respectively.

The channel impulse response (CIR) of the channel between the xthreceiver antenna of STA m and the ythtransmitter antenna of the AP can be denoted as: hm,x,yCIR(τ)=Σl=1Lαm,x,y,l·δ(τ−τm,x,y,l), where L is the number of channel paths, αm,x,y,land τm,x,y,lare the attenuation factor and the path delay of the lthpath, respectively.

In practice, CIR can be obtained by taking an inverse Fourier transform (IFFT) of CFR. The CIR of channel between the xthreceiver antenna of STA m and the ythtransmitter antenna of the AP can be represented as a vector according to the following equation:

hm,x,yC⁢I⁢R=[βm,x,y,1,…,βm,x,y,l,…,βm,x,y,K]T∈ℂK×1(1)where,βm,x,y,l={αm,x,y,l,ifk=⌊τm,x,y,l/TS⌋,0,otherwises,

In equation (1), TSis the time interval of signal sampling and └⋅┘ is the floor function (i.e., rounding up the input to the nearest integer less than or equal to that input).

After CSI (e.g., real-time CSI) measurement, since reporting the full measured raw channel vectors Hm,kto the AP302may include significant overhead, in some embodiments, the relevant one or more STAs (e.g., one or more STAs304) that intend to feedback real-time CSI can employ tone grouping to compress the estimated channel vectors.

In an embodiment, the AP302can send a beamforming report poll (BFRP) trigger frame310to coordinate a group of one or more STAs (e.g., one or more STAs304) to send their compressed real-time CSI in beamforming report (BR) frames through uplink MU-MIMO. Accordingly, in an embodiment, SIFS time units after sending the NDP frame308, the AP302can send a BFRP Trigger frame310to one or more of STAs304. In response to the BFRP trigger frame310, SIFS time units after receiving the BFRP Trigger frame310, each of the one or more STAs304can send one or more BR frames312to the AP302. Each BR frame of the BR frames312may indicate real-time CSI associated with the AP302and the corresponding STA of the one or more STAs304.

After receiving the one or more BR frames312, the AP302can decode the BR frames312and identify the intended one or more STAs by using the MAC address in the corresponding BR frames. Thus, for STA m, its decoded CSI in the kthsubcarrier at the AP side can be denoted as {tilde over (H)}m,k. After receiving and decoding all intended STAs' BR frames, the AP302can obtain information required for downlink MU-MIMO transmission.

In some embodiments, after channel estimation as described herein, each STA of the one or more STAs304can calculate or obtain the CFI. In some embodiments, the calculation or obtaining the CFI may comprise analyzing both time and frequency domain features of the wireless channel associated with said STA and the AP302.

As further described herein, the one or more STA's304can send, to the AP302, CFI based on one or more thresholds. As described herein, the one or more STA's304can send CFI by piggybacking or attaching the CFI to an uplink data (e.g., PPDU314).

The one or more threshold may indicate trigger conditions associated with CFI, such that when the trigger conditions are met (i.e., the threshold is satisfied), the one or more STA's304can feedback the CFI associated with the satisfied threshold.

In some embodiments, the one or more thresholds can be set or determined by the one or more STA's304, in which, the one or more STA's defines thresholds associated with CFI, and when obtaining CFI, the one or more STA's304can determine if the one or more thresholds are satisfied.

In some embodiments, the one or more thresholds can be set or determined by the AP302. The AP302can indicate one or more thresholds for CFI via a subfield in the enhanced trigger frame format as described in reference toFIG.7. Accordingly, in an embodiment, the AP302can indicate one or more CFI feedback thresholds via a subfield (e.g., delayed CFI feedback threshold720) in the trigger frame (e.g., BFRP trigger frame310). The one or more STA's can feedback, via uplink data, e.g., PPDU314, the CFI corresponding to one or more threshold that are satisfied.

In some embodiments, CFI includes information indicative of a level of channel variation.

The level of channel variation (e.g., variation of CFR) of the fthResource Unit (RU) experienced by STA m between current channel sounding at time instance t and the last channel sounding at instance tlastcan be represented according to the following:

Vk,f[t]=1E⁢∑m=fE(f+1)⁢E-1⁢1t-tlast·(1-|v⁢e⁢c⁡(Hm,klast)⁢v⁢e⁢c⁡(Hm,k)H||v⁢e⁢c⁡(Hm,klast)|·|vec⁡(Hm,k)|)(2)

where Hm,klastis the measured CFR in the last channel sounding and vec(⋅) is the vectorization function of a matrix, which converts the matrix into a column vector.

In equation (2), Vk,f[t] can be inversely proportional to the correlation of channel vectors and directly proportional to the time duration between two channel sounding. This metric can reflect the channel variation speed and help AP (e.g., AP302) determine how frequently the one or more STAs304can or should feedback the real-time CSI in the channel sounding process.

In some embodiments, CFI includes information indicative of a level of frequency-domain correlation.

The frequency-domain correlation may be based at least in part on the CIR. In the current channel sounding, at time instance t, the frequency-domain correlation of the channel between the xthreceiver antenna of STA m and the ythtransmitter antenna of AP302can be represented as follows:
Ck,x,y[t]=1/sqrt(τ2−(τ)2)  (3)
where parameterτcan represent the mean excess delay (i.e., the first moment of the power delay profile) according to the following:

τ¯=∑l=1L|αm,x,y,l|·τm,x,y,l/∑l=1L|αm,x,y,l|(4)
and parameterτ2can represent the second central moment according to the following:

τ2_=∑l=1L|αm,x,y,l|τm,x,y,l2/∑l=1L|αm,x,y,l|(5)

In equation (3), Ck,x,y[t] can be inversely proportional to Root Mean Square (RMS) delay spread, which can be a quantification of coherence bandwidth. This metric can help AP302to determine how many tones (subcarriers) a STA can group in the CSI feedback.

In some embodiments, CFI includes information indicative of a temporary sparsity level of CIR.

The sparsity level of a channel can be evaluated using a sparseness metric in matrix theory. In the current channel sounding, at time instance t, the sparsity level of the channel between the xthreceiver antenna of STA m and the ythtransmitter antenna, in sparseness metric, can be represented as follows:

Tm,x,y[t]=M-(∑l=1K|βm,x,y,l|)/sqrt⁡(∑l=1K|βm,x,y,l|2)M-1(6)
where βm,x,y,lcan represent the kthelement in Equation (1).

Referring to equation (6), this metric can quantify the sparsity of CIR and can help AP302determine whether a STA should feedback CIR to the AP. If the CIR has high level of sparsity, less overhead to feedback CSI can be used. For example, if CIR is sparse, a more efficient transmission of a few samples of CIR in the time domain rather than full number of subcarriers of CSI in the frequency domain may be sufficient.

Embodiments described herein may provide for an opportunistic channel sounding with combined two types of channel information feedback (i.e., long-term channel information (CFI) and real-time CSI). Embodiments described herein may provide for an opportunistic transmission of CFI via piggybacking such information with traffic data in a data frame. The CFI can be determined based on some evaluated parameters, such as, the level of channel variations, the level of frequency-domain correlation and temporary sparsity level of CIR as described herein.

As described herein, adaptive delayed channel feature response feedback can be transmitted by a STA based on whether or not the predefined threshold(s) (i.e., trigger condition) on CFI, is satisfied.

In some embodiments, when a STA of the one or more STAs304receives a request to perform channel sounding, in response to the request, the one or more STAs can calculate, determine or obtain channel feature parameters including one or more of: level of channel variation (e.g., channel variation speed), the level of frequency-domain correlation, and temporary sparsity level of CIR. After determining the CFI, the STA can send the CFI to the AP302through the UL data payload if a trigger condition is satisfied. Based on the received feedback information (e.g., the CFI), the AP302can perform opportunistic channel sounding by providing instructions to the STA on which type of CSI feedback is preferred for the CSI feedback.

FIG.4illustrates a trigger frame format. The trigger frame format400may be similar to the trigger frame format in 802.11ax, sec 9.3.1.22 (High efficiency (HE)). The trigger frame format400can refer to the BFRP frame310and320. As illustrated the trigger frame format400can comprise fields indicating one or more of: a medium access control (MAC) header402, common info field404, user info field406, padding408and frame check sequence (FCS)410. Each field of the trigger frame format can have appropriate size as illustrated.

In some embodiments, the channel sounding procedure300may comprise, after sending NDPA308and NDP308frames, AP302can set a feasible ThrV, which can be carried in the delayed CFI feedback threshold subfield720in an extension of HE variant User Info field of the BFRP trigger frame (e.g., BFRP trigger frame310), as illustrated inFIG.7and further described herein.

FIG.5illustrates trigger type subfield encoding. The trigger type table500may be similar to the trigger type subfield encoding in Sec. 9.3.1.22 of 802.11ax. The BFRP trigger frame variant can be indicated or identified by the trigger type subfield in the Common Info field (e.g., common info404) of the trigger frame (e.g., trigger frame format400).

FIG.6Aillustrates a user info field format of a trigger frame. The user info field format600may be a field format for the user Info field (e.g., user info406) of a BFRP trigger frame. The user info field format600may be an HE variant User Infor field format, which may be similar to the User Info field format defined in Sec. 9.3.1.22, 802.11ax.

As illustrated the user info field format600can comprise one or more subfields indicating one or more of: association identifier (AID)12602, RU allocation604, UL forward error correction (FEC) coding type606, UL HE-modulation and coding scheme (MCS)608, UL dual carrier modulation (DCM)610, spatial streams (SS) allocation/random access resource unit (RA-RU) information612, UL target receive power614, a reserved subfield616, and trigger dependent user info618. Each field of the user info field format600can have appropriate size as illustrated.

FIG.6Billustrates a trigger dependent user info subfield format. The format620can be the format for the trigger dependent user info subfield in an HE BFRP trigger frame. The format620may be similar to the trigger dependent user info subfield format in the HE BFRP trigger frame in Sec. 9.3.1.22, 802.11ax. The format620may comprise a field indicating a feedback segment retransmission bitmap.

Embodiments described herein may provide for an enhanced user info field format in the BFRP trigger frame. The enhanced user info field format can be based on an extension of 802.11ax user info field. The enhanced user info field format may allow transmission of delayed CFI feedback threshold for adaptive delayed CFI feedback.

FIG.7illustrates an enhanced user info field format in the BFRP trigger frame, according to an embodiment of the present disclosure.

In an embodiment, the enhanced user info field format700can comprise one or more subfields indicating one or more of: AID12702(can be allocated 12 bits), RU allocation704(can be allocated 8 bits), UL FEC coding type706(can be allocated 1 bit), UL MCS708(can be allocated 4 bits), UL DCM710(can be allocated 1 bit), SS allocation/RA-RU information712(can be allocated 6 bits), UL target receive power714(can be allocated 7 bits), an extension indication (can be allocated 1 bit), feedback segment retransmission bitmap718(can be allocated 8 bits), and delayed CFI feedback threshold720(can be allocated 8 or more bits).

In an embodiment, comparing the enhanced format700with the format600, the extension indication subfield716in the format700replaces the Reserved subfield616in the format600. The inclusion or presence of the extension indication subfield716can be accomplished by setting the reserved subfield616to ‘1’, which can further indicate the inclusion or presence of the delayed CFI feedback threshold subfield720in the BFRP trigger frame.

The delayed CFI feedback threshold subfield720can indicate one or more thresholds related to CFI. As discussed herein, CFI comprises, among other related channel information, channel feature parameters indicative of one or more of: level of channel variations, level of frequency-domain correlation, and temporary sparsity level of CIR.

In an embodiment, after completing or performing channel measurement, STA m, of the one or more STAs304, can calculate or determine the CFI and determine if the one or more trigger conditions are satisfied. The one or more trigger conditions may refer to one or more thresholds related to CFI as indicated in the delayed CFI feedback threshold720in the enhanced user info field format700in the BFRP trigger frame.

In an embodiment, if the one or more trigger conditions is not satisfied, STA m may not feedback the CFI to AP302.

In an embodiment, if the one or more trigger conditions described above is satisfied, STA m may send the CFI associated with the one or more trigger conditions to AP (e.g., AP302). In an embodiment, STA m may send the associated CFI via piggybacking said information in the data payload of UL physical layer (PHY) protocol data unit (PPDU), as shown inFIG.8. Accordingly, when the STA m has an opportunity to send the UL data to the AP, the STA m can piggyback the associated channel information in the data payload of the UL data.

FIG.8illustrates a physical layer (PHY) protocol data unit (PPDU) format comprising CFI, according to an embodiment of the present disclosure. The PPDU format800may comprise one or more fields indicating one or more of: legacy preamble802, HE preamble804and data payload806. In an embodiment, the data payload806can comprise one or more of traffic data and CFI. The PPDU format800illustrates piggybacking of CFI in the UL data payload.

Embodiments described herein may provide for an enhanced user info field (e.g., user info field format700) that allows for the inclusion of the delayed CFI feedback threshold subfield720in the extension of HE variant User Info field in the BFRP trigger frame. In some embodiments, the delayed CFI feedback threshold subfield720may indicate one or more trigger conditions being one or more threshold associated with CFI. In some embodiments, the presence of the delayed CFI feedback threshold may indicate or signal that a STA (e.g., one or more STAs304) is to transmit to the AP302CFI (delayed CFI feedback) based the one or more trigger conditions. In some embodiments, the STA of the one or more STAs304can feedback the relevant CFI to AP via including the relevant CFI in the uplink PPDU.

In the channel sounding procedure (e.g., channel sounding procedure300), after collecting and analyzing the CFI sent from one or more STAs304, AP302may then have knowledge of the pattern of the one or more relevant wireless channels.

Referring to channel sounding procedure300, the AP may have knowledge of the pattern of the one or more relevant wireless channels associated with the one or more STAs304after the real-time CSI feedback portion330and the delayed CFI feedback portion335. In such embodiments, the channel sounding at time t, which involves the real-time CSI feedback portion330and the delayed CFI feedback portion335may be the initial or the first channel sounding phase. Accordingly, channel sounding at time t+T (a subsequent channel sounding phase), referring to the real-time CSI feedback portion340and the delayed CFI feedback portion (not shown), the AP can request, from the one or more STAs304, channel information (e.g., real-time CSI, and CFI) when needed. This is because the AP302at time t+T may have knowledge of the pattern of the one or more relevant wireless channels, based on channel sounding at time t (e.g., the real-time CSI feedback portion330and the delayed CFI feedback portion335). Accordingly, the AP302can send an NDPA frame316to provide instruction to the one or more STAs304on what channel information (e.g., one or both of: real-time CSI and delayed CFI), and the type of information in each type of feedback (e.g., what type of information to be included in the real-time CSI feedback, and/or the delayed CFI feedback) to feedback to the AP. For example, the NDPA frame316can comprise one or more subfields in the STA info field, as further described in reference toFIG.10, to indicate what channel information (e.g., real-time CSI and/or CFI) and the type of information in each type of feedback to be provided by the one or more STAs.

In some embodiments, the channel sounding at time t may be not be the first or initial channel sounding phase. Thus, the AP302may already have knowledge of the of the pattern of the one or more relevant wireless channels based on a previous one or more channel sounding phase. Thus, at the channel sounding at time t (referring to the real-time CSI feedback portion330and the delayed CFI feedback portion335) the AP can send an NDPA frame306to provide instruction to the one or more STAs304on what channel information (e.g., one or both of: real-time CSI and delayed CFI), and the type of information in each type of feedback (e.g., what type of information to be included in the real-time CSI feedback, and/or the delayed CFI feedback) to provide the AP. For example, the NDPA frame306can comprise one or more subfields in the STA info field, as further described in reference toFIG.10, to indicate what channel information (e.g., real-time CSI and/or delayed CFI) and the type of information in each type of feedback to be provided by the one or more STAs to the AP.

Accordingly, in an embodiment, the AP302can request from the one or more STAs304to send channel information (e.g., real-time CSI and delayed CFI) when needed. In some embodiments, the AP302can indicate a format for the channel information feedback to be sent by the one or more STAs304. In some embodiments, the requested format of the Channel information feedback can be CIR or CFR or other formats as described herein.

Accordingly, embodiments described herein may provide for obtaining channel information when needed. Embodiments may further provide for obtaining channel information feedback in a preferred format. Thus, embodiments described herein may provide for reduced feedback overhead (e.g., CSI feedback overhead) while maintaining a accurate and timely channel information.

Embodiments described herein may provide for sending, by an AP, one or more instructions to one or more STAs on how to feedback channel information. In some embodiments, instructions on how to feedback channel information can be indicated in the STA info field of the NDPA frame (e.g., NDPA306or316). In some embodiments, the EHT variant NDPA frame (e.g., NDPA frame in 802.11be D1.3) can be modified or enhanced to include in its STA info field one or more instructions on how to feedback channel information.

FIG.9Aillustrates an HE/EHT variant NDPA frame format. The frame format900may refer to the frame format of the HE/EHT variant NDPA frame formant in sec. 9.3.1.19, 802.11ax-2020. The frame format900can comprise one or more fields indicating one or more of: frame control902, duration904, receiver address (RA)906, transmitter address (TA)908, MAC header920, a sounding dialog token910, a STA info912, and FCS914. As illustrated, the MAC header920can comprise one or more of: frame control field902, duration field904, RA field906and TA field908.

FIG.9Billustrates a STA info field format in EHT variant NDPA frame. The field format950may be the STA info field format of EHT variant NDPA frame in Sec. 9.3.1.19, 802.11be D1.0. The field format950can comprise one or more subfields indicating one or more of: AID11952, partial bandwidth (BW) info954, a reserved subfield956, Nc Index (Nc is the number of columns in the compressed beamforming feedback matrix)958, feedback type and Ng (Ng is the number of grouping subcarriers)960, disambiguation962, codebook size964, and a reserved field966.

In some embodiments, the STA info field (e.g., STA info field format95) in EHT variant NDPA frame may be modified or enhanced by adding one or more subfields for indicating one or more of: real-time CSI feedback and delayed CFI feedback.

FIG.10illustrates an enhanced STA info field format, according to an embodiment of the present disclosure. The enhanced STA info field format1000can be a modification or enhancement to the STA Info field of the EHT variant NDPA frame.

In an embodiment, the enhanced STA info field format1000can comprise one or more subfields indicating one or more of: AID111002, partial bandwidth (BW) info1004, a reserved subfield1006, Nc Index (Nc is the number of columns in the compressed beamforming feedback matrix)1008, feedback type and Ng (Ng is the number of grouping subcarriers)1010, disambiguation1012, codebook size1014, a reserved subfield1016, CSI feedback indication1018, real-time CSI indication1020, and delayed CFI indication1022.

Each subfield in the enhanced STA info field format1000can be allocated an appropriate size as illustrated. In some embodiments, the CSI feedback indication subfield1018can be 2 bits.

In some embodiments, the AP302can set the CSI feedback indication subfield1018to indicate real-time CSI feedback only. For example, the AP302can set the CSI feedback indication subfield1018to ‘00’ to request, from the one or more STAs304, real-time CSI feedback only. Accordingly, in response to receiving the NDPA frame having a CSI feedback indication subfield1018set to indicate real-time CSI feedback only, the one or more STAs304can respond with real-time CSI in the BR frames (e.g., BR frames312or322).

In some embodiments, the AP302can set the CSI feedback indication subfield1018to indicate delayed CFI feedback only. For example, the AP302can set the CSI feedback indication subfield1018to ‘01’ to request, from the one or more STAs304, the delayed CFI feedback only. Accordingly, in response to receiving the NDPA frame having a CSI feedback indication subfield1018indicating delayed CFI feedback only, the one or more STAs304can respond with delayed CFI only by piggybacking the delayed CFI with a PPDU as described herein.

In some embodiments, the indication for delayed CFI feedback only (e.g., setting the CSI feedback indication subfield1018to ‘01’) can indicate that the one or more STAs304need not feedback real-time CSI. Thus, in response to receiving such indication, the one or more STAs may not feedback real-time CSI. In such embodiments, while the one or more STAs304may not feedback real-time CSI, the one or more STAs304can still perform channel information measurement (e.g., CSI, CFI measurement) and decide whether or not to feedback CFI to the AP.

In some embodiments, the AP302can set the CSI feedback indication subfield1018to indicate both real-time CSI and delayed CFI feedback. For example, the AP302can set the CSI feedback indication subfield1018to ‘10’ to request, from the one or more STAs304, both real-time CSI and delayed CFI feedback. Accordingly, in response to receiving the NDPA frame having a CSI feedback indication subfield1018to indicate both real-time CSI and delayed CFI feedback, the one or more STAs304receiving can respond with real-time CSI in the BR frames (e.g., BR frames312, or322), and further respond with delayed CFI by piggybacking the delayed CFI with a PPDU as described herein.

In some embodiments, the setting ‘11’ for the CSI feedback indication subfield1018can be reserved.

In some embodiments, the real-time CSI indication subfield1020can be allocated an appropriate bit size, e.g., n1 bits. In some embodiments, the real-time CSI indication subfield1020can indicate the type of information the one or more STAs should feedback in real-time CSI feedback. In some embodiments, the real-time CSI indication subfield1020can indicate that the real-time CSI feedback should include one or more of compressed CSI, CFR and CIR.

In some embodiments, the delayed CFI indication subfield1022can be allocated an appropriate bit size, e.g., n2 bits. In some embodiments, the real-time CSI indication subfield1020can indicate the type of information the one or more STAs should feedback in delayed CFI feedback. In some embodiments, the delayed CFI indication subfield1022can indicate that the delayed CFI feedback should include one or more of compressed CSI, CFR, CIR and channel feature parameters. As discussed herein, channel feature parameters include information indicative of one or more of: the level of channel variations, level of frequency-domain correlation, and temporary sparsity level of channel impulse response.

Embodiments described herein may provide for improved CSI feedback using enhanced STA info field formats which include indications for CSI feedback, real-time CSI and delayed CFI.

Embodiments described herein may provide for an opportunistic channel sounding based on the latency tolerance of CFI. In some embodiments, the opportunistic channel sounding may provide for real-time CSI feedback. In some embodiments, the opportunistic channel sounding may further provide for delayed CFI feedback. In some embodiments, the delayed CFI feedback is performed by piggybacking the delayed CFI with traffic data in a data frame.

Embodiment described herein may further provide for an enhanced user info field format in the BFRP trigger frame, the enhanced user info field format comprising a subfield for delayed CFI feedback threshold. Embodiments described herein may further provide for an enhanced STA info field format in the NDPA frame for efficient CFI feedback.

FIG.11is a schematic diagram of an electronic device1100that may perform any or all of operations of the above methods and features explicitly or implicitly described herein, according to different embodiments of the present invention. For example, a computer equipped with network function may be configured as electronic device1100. In some embodiments, the electronic device may be a device that connects to the network infrastructure over a radio interface, such as a mobile phone, smart phone or other such device that may be classified as a user equipment (UE). In some embodiments, the electronic device1100may be a Machine Type Communications (MTC) device (also referred to as a machine-to-machine (m2m) device), or another such device that may be categorized as a UE despite not providing a direct service to a user. In some references, an ED may also be referred to as a mobile device, a term intended to reflect devices that connect to mobile network, regardless of whether the device itself is designed for, or capable of, mobility. In some embodiments, electronic device1100may be used to implement one or more embodiments described herein. For example, the electronic device1100may be configured to perform operations performed by an AP or a beamformer, a STA or beamformee, or the like as appreciated by a person skilled in the art.

As shown, the electronic device1100may include a processor1110, such as a Central Processing Unit (CPU) or specialized processors such as a Graphics Processing Unit (GPU) or other such processor unit, memory1120, non-transitory mass storage1130, input-output interface1140, network interface1150, and a transceiver1160, all of which are communicatively coupled via bi-directional bus1170. According to certain embodiments, any or all of the depicted elements may be utilized, or only a subset of the elements. Further, electronic device1100may contain multiple instances of certain elements, such as multiple processors, memories, or transceivers. Also, elements of the hardware device may be directly coupled to other elements without the bi-directional bus. Additionally, or alternatively to a processor and memory, other electronics, such as integrated circuits, may be employed for performing the required logical operations.

The memory1120may include any type of non-transitory memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), any combination of such, or the like. The mass storage element1130may include any type of non-transitory storage device, such as a solid state drive, hard disk drive, a magnetic disk drive, an optical disk drive, USB drive, or any computer program product configured to store data and machine executable program code. According to certain embodiments, the memory1120or mass storage1130may have recorded thereon statements and instructions executable by the processor1110for performing any of the aforementioned method operations described above.

Embodiments of the present invention can be implemented using electronics hardware, software, or a combination thereof. In some embodiments, the invention is implemented by one or multiple computer processors executing program instructions stored in memory. In some embodiments, the invention is implemented partially or fully in hardware, for example using one or more field programmable gate arrays (FPGAs) or application specific integrated circuits (ASICs) to rapidly perform processing operations.

It will be appreciated that, although specific embodiments of the technology have been described herein for purposes of illustration, various modifications may be made without departing from the scope of the technology. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention. In particular, it is within the scope of the technology to provide a computer program product or program element, or a program storage or memory device such as a magnetic or optical wire, tape or disc, or the like, for storing signals readable by a machine, for controlling the operation of a computer according to the method of the technology and/or to structure some or all of its components in accordance with the system of the technology.

Acts associated with the method described herein can be implemented as coded instructions in a computer program product. In other words, the computer program product is a computer-readable medium upon which software code is recorded to execute the method when the computer program product is loaded into memory and executed on the microprocessor of the wireless communication device.

Further, each operation of the method may be executed on any computing device, such as a personal computer, server, PDA, or the like and pursuant to one or more, or a part of one or more, program elements, modules or objects generated from any programming language, such as C++, Java, or the like. In addition, each operation, or a file or object or the like implementing each said operation, may be executed by special purpose hardware or a circuit module designed for that purpose.

Through the descriptions of the preceding embodiments, the present invention may be implemented by using hardware only or by using software and a necessary universal hardware platform. Based on such understandings, the technical solution of the present invention may be embodied in the form of a software product. The software product may be stored in a non-volatile or non-transitory storage medium, which can be a compact disc read-only memory (CD-ROM), USB flash disk, or a removable hard disk. The software product includes a number of instructions that enable a computer device (personal computer, server, or network device) to execute the methods provided in the embodiments of the present invention. For example, such an execution may correspond to a simulation of the logical operations as described herein. The software product may additionally or alternatively include a number of instructions that enable a computer device to execute operations for configuring or programming a digital logic apparatus in accordance with embodiments of the present invention.

Although the present invention has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.