CSI processing for fine CSI granularity

Certain aspects of the present disclosure provide techniques for channel state information (CSI) processing for fine granularity CSI. A method for wireless communications by a user equipment (UE) includes receiving a CSI reporting configuration. The CSI reporting configuration includes a number of frequency domain (FD) units and a FD unit size for CSI reporting. The UE determines a number of CSI processing units at the UE to use for processing the CSI report based on the number of FD units or the FD unit size for the CSI report. The UE processes the CSI report based on the determined number CSI processing units. In another method, the UE determines at least one threshold to use for determining whether to update a CSI report based on the number of FD units or the FD unit size for CSI reporting.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a national stage application under 35 U.S.C. 371 of PCT/CN2020/073709, filed Jan. 22, 2020, which claims benefit of and priority to International Application No. PCT/CN2019/072625, filed Jan. 22, 2019, which are both assigned to the assignee hereof and hereby expressly incorporated by reference herein in their entireties as if fully set forth below and for all applicable purposes.

BACKGROUND

Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for channel state information (CSI) processing.

Description of Related Art

SUMMARY

Certain aspects provide a method for wireless communication by a user equipment (UE). The method generally includes receiving a channel state information (CSI) reporting configuration. The CSI reporting configuration includes a number of frequency domain (FD) units and a FD unit size for CSI reporting. The method generally includes determining a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both, to use for processing the CSI report based on the number of FD units or the FD unit size. The method generally includes processing the CSI report based on the determination.

Certain aspects provide another method for wireless communication by a base station (BS). The method generally includes configuring a UE with a CSI reporting configuration. The CSI reporting configuration includes a number of FD units and a FD unit size for CSI reporting based on a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both. The method generally includes receiving the CSI report from the UE based on the configuration.

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes a memory and at least one processor coupled with the memory. The at least one processor is generally configured to receive a CSI reporting configuration. The CSI reporting configuration includes a number of FD units and a FD unit size for CSI reporting. The at least one processor is generally configured to determine a number of CSI processing units at the apparatus, at least one time threshold for CSI processing, or both, to use for processing the CSI report based on the number of FD units or the FD unit size. The at least one processor is generally configured to process the CSI report based on the determination.

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes a memory and at least one processor coupled with the memory. The at least one processor is generally configured to configure a UE with a CSI reporting configuration. The CSI reporting configuration includes a number of FD units and a FD unit size for CSI reporting based on a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both. The at least one processor is generally configured to receive the CSI report from the UE based on the configuration.

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes means for receiving a CSI reporting configuration. The CSI reporting configuration includes a number of FD units and a FD unit size for CSI reporting. The apparatus generally includes determining a number of CSI processing units at the apparatus, at least one time threshold for CSI processing, or both, to use for processing the CSI report based on the number of FD units or the FD unit size. The apparatus generally includes means for processing the CSI report based on the determination.

Certain aspects provide an apparatus for wireless communication. The apparatus generally includes means for configuring a UE with a CSI reporting configuration. The CSI reporting configuration includes a number of FD units and a FD unit size for CSI reporting based on a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both. The apparatus generally includes means for receive the CSI report from the UE based on the configuration.

Certain aspects provide a computer readable medium storing computer executable code thereon for wireless communication. The computer executable code generally includes code for receiving a CSI reporting configuration. The CSI reporting configuration includes a number of FD units and a FD unit size for CSI reporting. The computer executable code generally includes code for determining a number of CSI processing units at a UE, at least one time threshold for CSI processing, or both, to use for processing the CSI report based on the number of FD units or the FD unit size. The computer executable code generally includes code for processing the CSI report based on the determination.

Certain aspects provide a computer readable medium storing computer executable code thereon for wireless communication. The computer executable code generally includes code for configuring a UE with a CSI reporting configuration. The CSI reporting configuration includes a number of FD units and a FD unit size for CSI reporting based on a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both. The computer readable medium generally includes code for receive the CSI report from the UE based on the configuration.

Aspects of the present disclosure provide means for, apparatus, processors, and computer-readable mediums for performing the methods described herein.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for channel state information (CSI) processing, for example for processing fine granularity CSI, such as subband precoder matrix indicator (PMI) feedback.

In certain systems (e.g., such Release-16 5G NR systems), a fine granularity is used for PMI feedback (e.g., a small one resource block (RB)) to enhance performance of the CSI report. The fine granularity may lead to large CSI overhead due to a larger number of frequency units (e.g., subbands) to report and, therefore, lead to larger CSI computation complexity. Therefore, techniques are desirable for more efficient CSI reporting which may save battery life.

In some cases, CSI configurations (and therefore also the CSI reports) with the finer PMI granularity may be limited. According to certain aspects of the present disclosure, the number of CSI processing units used at the user equipment (UE) for CSI processing can be based on the number of frequency units the UE is configured to report CSI. Additionally or alternatively, the CSI processing timeline can be based on the number of configured frequency units. For example, a larger timing threshold may be used for updating CSI report when fine frequency unit size is configured for the CSI reporting.

The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

New radio (NR) access (e.g., 5G technology) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., 25 GHz or beyond), massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same subframe. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells.

FIG.1illustrates an example wireless communication network100in which aspects of the present disclosure may be performed for channel state information (CSI) processing for fine granularity precoding matrix information (PMI). For example, the wireless communication network100may be an NR system (e.g., a 5G NR network). As shown inFIG.1, the wireless communication network100may be in communication with a core network132. The core network132may in communication with one or more base station (BSs)110and/or user equipment (UE)120in the wireless communication network100via one or more interfaces.

The BSs110communicate with UEs120a-y(each also individually referred to herein as UE120or collectively as UEs120) in the wireless communication network100. The UEs120may be stationary or mobile. Wireless communication network100may also include relay stations (e.g., relay station110r), also referred to as relays or the link, that receive a transmission of data and/or other information from an upstream station (e.g., a BS110aor a UE120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE120or a BS110), or that relays transmissions between UEs120, to facilitate communication between devices.

According to certain aspects, the BSs110and UEs120may be configured for CSI reporting. As shown inFIG.1, the UE120ain the wireless communication network100includes a CSI manager122. The CSI manager122may be configured to receive a CSI reporting configuration, for example from the BS110ain the wireless communication network100. The CSI reporting configuration may include a number of frequency domain (FD) units and a FD unit size for CSI reporting. The CSI manager122may be configured to determine a number of CSI processing units at the UE120aand/or a CSI processing time threshold to use for processing the CSI report based on the configured number of FD units or the FD unit size for the CSI report. The UE120processes the CSI report based on the determined number CSI processing units and/or CSI processing time threshold. As shown inFIG.1, the BS110aincludes a CSI manager112. The CSI manager112may be configured for CSI processing in accordance with aspects of the present disclosure.

FIG.2illustrates example components of BS110aand UE120a(as depicted inFIG.1), which may be used to implement aspects of the present disclosure.

At the BS110a, a transmit processor220may receive data from a data source212and control information from a controller/processor240. The control information may be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), etc. The data may be for the physical downlink shared channel (PDSCH), etc. The processor220may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor220may also generate reference symbols, e.g., for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and CSI reference signal (CSI-RS). A transmit (TX) multiple-input multiple-output (MIMO) processor230may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs)232athrough232t. Each modulator232may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators232athrough232tmay be transmitted via the antennas234athrough234t, respectively.

Antennas252, processors266,258,264, and/or controller/processor280of the UE120aand/or antennas234, processors220,230,238, and/or controller/processor240of the BS110amay be used to perform the various techniques and methods described herein for CSI processing for fine granularity PMI. For example, as shown inFIG.2, the controller/processor240of the BS110ahas a CSI manager241that may be configured for CSI processing for fine granularity, according to aspects described herein. As shown inFIG.2, the controller/processor280of the UE120ahas CSI manager281that may be configured for CSI processing for fine granularity, according to aspects described herein. The memories242and282may store data and program codes for BS110aand UE120a, respectively. A scheduler244may schedule UEs for data transmission on the downlink and/or uplink.

NR may utilize orthogonal frequency division multiplexing (OFDM) and/or uplink and single-carrier frequency division multiplexing (SC-FDM). NR may support half-duplex operations using time division duplexing (TDD). OFDM and SC-FDM partition the system bandwidth into multiple orthogonal subcarriers, also referred to as tones, bins, etc. Each subcarrier may be modulated with data. Modulation symbols may be sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers may be dependent on the system bandwidth. NR may support a base subcarrier spacing (SCS) of 15 kHz and other SCS may be defined with respect to the base SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.).

In NR, a subframe is still 1 ms, but the basic TTI is referred to as a slot.FIG.3is a diagram showing an example of a frame format300for NR. The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be partitioned into 10 subframes, each of 1 ms, with indices of 0 through 9. Each subframe may include a variable number of slots (e.g., 1, 2, 4, 8, 16, . . . slots) depending on the SCS. Each slot may include a variable number of symbol periods (e.g., 7 or 14 symbols) depending on the SCS. The symbol periods in each slot may be assigned indices. A mini-slot, which may be referred to as a sub-slot structure, refers to a transmit time interval having a duration less than a slot (e.g., 2, 3, or 4 symbols). Each symbol in a slot may indicate a link direction (e.g., DL, UL, or flexible) for data transmission and the link direction for each subframe may be dynamically switched. The link directions may be based on the slot format. Each slot may include DL/UL data as well as DL/UL control information.

Channel state information (CSI) may refer to channel properties of a communication link. The CSI may represent the combined effects of, for example, scattering, fading, and power decay with distance between a transmitter and receiver. Channel estimation using pilots, such as CSI reference signals (CSI-RS), may be performed to determine these effects on the channel. CSI may be used to adapt transmissions based on the current channel conditions, which is useful for achieving reliable communication, in particular, with high data rates in multi-antenna systems. CSI is typically estimated at the receiver, quantized, and fed back to the transmitter.

The time and frequency resources that can be used by the UE to report CSI are controlled by the BS (e.g., a gNB). CSI may include of Channel Quality Indicator (CQI), precoding matrix indicator (PMI), CSI-RS resource indicator (CRI), SS/PBCH Block Resource indicator (SSBRI), layer indicator (LI), rank indicator (RI) and/or L1-RSRP.

The network (e.g., the BS110a), may configure UEs (e.g., the UE120a) for CSI reporting. For example, the BS may configure the UE with a CSI report configuration or with multiple CSI report configurations. The CSI report configuration may be provided to the UE via higher layer signaling, such as radio resource control (RRC) signaling (e.g., a higher layer CSI-ReportConfig parameter). The CSI report configuration may be associated with CSI-RS resources for channel measurement (CM), interference measurement (IM), or both. The CSI report configuration configures CSI-RS resources for measurement (e.g., a higher layer CSI-ResourceConfig parameter). The CSI-RS resources provide the UE with the configuration of CSI-RS ports, or CSI-RS port groups, mapped to time and frequency resources (e.g., resource elements (REs)). CSI-RS resources can be zero power (ZP) or non-zero power (NZP) resources. At least one NZP CSI-RS resource may be configured for CM.

The CSI report configuration also configures the CSI parameters (sometimes referred to as quantities) to be reported. Three codebooks include Type I single panel, Type I multi-panel, and Type II single panel. Regardless which codebook is used, the CSI report may include the CQI, PMI, CRI, and/or RI. The structure of the PMI may vary based on the codebook. The CRI, RI, and CQI may be in a first part (Part I) and the PMI may be in a second part (Part II) of the CSI report. For the Type I single panel codebook, the PMI may consist of a W1 matrix (e.g., subest of beams) and a W2 matrix (e.g., phase for cross polarization combination and beam selection). For the Type I multi-panel codebook, compared to type I single panel codebook, the PMI further comprises a phase for cross panel combination. For the Type II single panel codebook, the PMI is a linear combination of beams; it has a subset of orthogonal beams to be used for linear combination and has per layer, per polarization, amplitude and phase for each beam. For the PMI of any type, there can be wideband (WB) PMI and/or subband (SB) PMI as configured.

The CSI report configuration may configure the UE for aperiodic, periodic, or semi-persistent CSI reporting. For periodic CSI, the UE may be configured with periodic CSI-RS resources. Periodic CSI and semi-persistent CSI report on physical uplink control channel (PUCCH) may be triggered via RRC or a medium access control (MAC) control element (CE). For aperiodic and semi-persistent CSI on the physical uplink shared channel (PUSCH), the BS may signal the UE a CSI report trigger indicating for the UE to send a CSI report for one or more CSI-RS resources, or configuring the CSI-RS report trigger state (e.g., higher layer CSI-Aperiodic TriggerStateList and CSI-SemiPersistentOnPUSCH-TriggerStateList parameters). The CSI report trigger for aperiodic CSI and semi-persistent CSI on PUSCH may be provided via downlink control information (DCI). The CSI-RS trigger may be signaling indicating to the UE that CSI-RS will be transmitted for the CSI-RS resource.

The UE may report the CSI feedback based on the CSI report configuration and the CSI report trigger. For example, the UE may measure the channel associated with CSI for the triggered CSI-RS resources. Based on the measurements, the UE may select a preferred CSI-RS resource. The UE reports the CSI feedback for the selected CSI-RS resource. LI may be calculated conditioned on the reported CQI, PMI, RI and CRI; CQI may be calculated conditioned on the reported PMI, RI and CRI; PMI may be calculated conditioned on the reported RI and CRI; and RI may be calculated conditioned on the reported CRI.

In certain systems (e.g., Release 15 5G NR), the UE may be configured for spatial domain compressed CSI reporting. For example, the UE may be configured to report at least a Type II precoder across configured frequency units:

wr=∑i=02⁢L-1⁢⁢bi·ci,where⁢⁢ci=[ci,0⁢⁢⋯⁢⁢ci,N3-1︸N3],
where biis the selected beam, ciis the set of linear combination coefficients, L is the number of selected spatial beams, and N3corresponds to the number of frequency units (e.g., subbands, resource blocks (RBs), etc.).

In certain systems (e.g., Rel-16 5G NR), the UE may be configured to report spatially and frequency domain compressed precoder feedback:
wr=Σi=02L-1bi·{tilde over (c)}i·FiH,
where the discrete Fourier transform (DFT) compression basis is given by:

FiH=[fi,0Hfi,1H⋮fi,N3-1]⁢⁢of⁢⁢size⁢⁢Mi×N3,
and where Miis dimension of the compressed domain. The coefficients are given by:

c~i=[ci,0⁢⁢⋯⁢⁢ci,Mi-1︸Mi],
and the dimension of the compressed domain is Mi<N3.

Each CSI report configuration may be associated with a single downlink bandwidth part (BWP). The CSI report setting configuration may define a CSI reporting band as a subset of subbands of the BWP. The associated DL BWP may indicated by a higher layer parameter (e.g., a higher layer bwp-Id parameter) in the CSI report configuration for channel measurement and contains parameter(s) for one CSI reporting band, such as codebook configuration, time-domain behavior, frequency granularity for CSI, measurement restriction configurations, and the CSI-related quantities to be reported by the UE. Each CSI resource setting may be located in the DL BWP identified by the higher layer parameter, and all CSI resource settings may be linked to a CSI report setting have the same DL BWP.

In certain systems (e.g., Rel-15 5G NR) for CSI reporting, the UE can be configured via higher layer signaling (e.g., in the CSI report configuration) with one out of two possible subband sizes (e.g., the higher layer reportFreqConfiguration parameter contained in a CSI-ReportConfig) which indicates a frequency granularity of the CSI report, where a subband may be defined as NPRBSBcontiguous physical resource blocks (PRBs) and depends on the total number of PRBs in the bandwidth part. For example, the Table400illustrated inFIG.4shows subbands sizes associated with BWPs.

In certain systems, a finer granularity is used for CSI. For example, a subband size for PMI may smaller than the subband sizes shown inFIG.4. The finer CSI granularity may lead to larger CSI computation complexity than for the larger CSI granularities. For example, the UE may compute CSI for an increased number of FD units. Therefore, techniques to improve UE computation efficiency and save battery life, for CSI configurations with fine PMI granularity, are desirable.

Example CSI Processing For Fine Granularity CSI

According to certain aspects, a number of channel state information (CSI) processing units at a user equipment (UE) that are used for the CSI reporting is based on the number of frequency domain (FD) units and/or FD unit size configured for the CSI reporting. In some examples, more CSI processing units at the UE may be used when the finer granularity CSI is configured. According to certain aspects, the CSI processing timeline (e.g., one or more CIS processing time thresholds) is based on the number of FD units and/or FD unit size for CSI reporting. In some examples, a longer CSI processing timeline may be used when fine granularity CSI is configured.

According to certain aspects, the UE may be configured to report subband precoder information, such as precoding matrix indicator (PMI). As discussed above, the CSI configuration may be associated with a bandwidth part (BWP) and the BWP may be associated with a bandwidth size and subband size. The UE may further receive an indication of the subbands for which the CSI feedback is requested.FIG.5shows example subbands configured (e.g., requested) for CSI reporting, in accordance with certain aspects of the present disclosure. In the example inFIG.5, thirteen of the nineteen total subbands (subbands 3, 4, . . . , 15) are requested for CSI reporting. In some examples, a subband mask is used to indicate the requested subbands for CSI reporting. The UE computes precoders for each requested subband and finds the PMI that matches the computed precoder on each of the subbands.

According to certain aspects, the CSI granularity (e.g., the PMI) spans a number of RBs (e.g., x RBs). As discussed above, the FD unit size may be a fine granularity. The granularity of the FD units may refer to the number of one or more RBs for which the UE is configured to report a single PMI. In some examples, the FD unit size may be smaller than the sizes shown inFIG.4for the associated BWPs. In some examples, granularity may be as small as 1 RB. In some examples, the PMI granularity may be smaller than a channel quality indicator (CQI) granularity. For example, the PMI granularity may be:
x=(CQI subband size)/R,
where R>1 is a predefined integer. Thus, the number of FD units (e.g., the number of subbands) may be up to the total number of configured subbands*R (e.g., 19R).

According to certain aspects, the number of CSI processing units may be based on the number of FD units or FD unit size for the CSI reporting. For example, the number of CSI processing units at the UE used for the CSI computing may be increased when the granularity if fine and the total number of FD units is high, whereas a fewer number of CSI processing units may be used at the UE when the FD unit size is larger and the total number of FD units to report is lower. Additionally or alternatively, one or more CSI processing time thresholds may be based on the PMI granularity.

FIG.6is a flow diagram illustrating example operations600for wireless communication. The operations600may be performed, for example, by UE (e.g., such as a UE120ain the wireless communication network100) for CSI processing, in accordance with certain aspects of the present disclosure. Operations600may be implemented as software components that are executed and run on one or more processors (e.g., processor280ofFIG.2). Further, the transmission and reception of signals by the UE in operations600may be enabled, for example, by one or more antennas (e.g., antennas252ofFIG.2). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., processor280) obtaining and/or outputting signals.

The operations600may begin, at605, by receiving a CSI reporting configuration. The CSI reporting configuration includes a number of FD units and a FD unit size for CSI reporting. In some examples, the CSI reporting configuration configures the UE for reporting subband PMI. In some examples, the number of FD units and the FD unit size is based on the BWP associated with the CSI reporting configuration. In some examples, the FD unit is a subband. In some examples, the FD unit size corresponds a number of RBs contained in one FD unit.

At610, the UE determines a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both, to use for processing the CSI report. The number of CSI processing units and/or the at least one time threshold for CSI processing are based on the number of FD units or the FD unit size for the CSI report.

At615, the UE processes the CSI report based on the determination.

According to certain aspects, the UE may receive a request for CSI reporting for at least a portion of the number of FD units. In some examples, the request may be an FD mask. For example, the FD mask may be a bitmap with length equal to the total number of configured FD units (e.g., associated with the BWP size). The bitmap may have “1's” indicating requested FD units. The number of “1”s in the bitmap corresponds to the number of FD units for a CSI report. In some examples, the request may include a CQI subband mask and an indication of the R FD units per subband. The CQI subband mask may be a bitmap with a length equal to the number of subbands, with “1's” in the bitmap corresponding to the number of subbands required for the CQI report, and the number of FD units is equal to R multiplied by the number of CQI subbands required for a CQI report.

Processing the CSI mau include computing the CSI using the determined number of CSI processing units. The CSI report configuration occupies a number of CSI processing units (OCPU). The UE may support a number of simultaneous CSI calculations NCPU. If the UE supports NCPUsimultaneous CSI calculations, the UE is said to have NCPUCSI processing units for processing CSI reports across all configured cells. If there are more CSI report configurations requiring more than NCPUCPUs, the UE may decide to drop some of the CSI reports so as to satisfy the capability of supporting max NCPUCSI calculations.

In certain systems (e.g., Rel-15 5G NR), OCPUis based on the configured report quantity. For example, OCPU=0 for report quantity “none” and CSI-RS-ResourceSet with higher layer parameter trs-Info configured; OCPU=1 for a CSI report quantity “cri-RSRP”, “ssb-Index-RSRP” or none; and OCPU=NCPU(NCPUas UE capability of total number of CPUs) for wideband CSI with up to 4 ports without CRI report; otherwise, OCPU=Ks, where Ksdenotes the number of CSI-RS resources configured for channel measurement.

According to certain aspects of the present disclosure, the UE determines the number CSI processing units (OCPU) to use based on the determined number of FD units for the CSI report.

In some examples, the UE can determine a first number of CSI processing units to use when the number of FD units for reporting CSI is equal to or below a first threshold or when the FD unit size for reporting CSI is equal to or larger than a second threshold (e.g., the FD unit size may correspond to the number of FD units for reporting). The UE may determine a second number of CSI processing units to use when the number of FD units for reporting precoder information feedback is above the first threshold (e.g., greater than the total number of CQI subbands contained in the BWP) or when the FD unit size for reporting CSI is below the second threshold (e.g., smaller than the CQI subband size).

In some examples, for a CSI report with a number of PMI subbands equal or below a threshold (e.g., 19 subbands), then OCPU=Ksand for a CSI report with the number of PMI subbands greater than the threshold, then a larger number of CSI processing units may be used, for example, equal to the first number of CSI processing units multiplied by an integer greater than one (OCPU=O*Ks, where O>1). The integer O can be determined based on the number of FD unit for CSI report and/or or the FD unit size. In some examples, the integer O is determined based on at the ratio of the number of FD units for CSI report to the first threshold and/or the ratio of the second threshold to the FD unit size. In some examples, the CSI report configuration configures one or more CSI-RS resources for channel measurement. The first and second number of CSI processing units may scale with the number of CSI-RS resources configured for channel measurement.

According to certain aspects, the CSI reporting timeline (e.g., the at least one time threshold for CSI processing) may be based on the number of FD units or FD unit size for CSI reporting.FIG.7is an example CSI reporting timeline700, in accordance with certain aspects of the present disclosure. As shown inFIG.7, after receiving the CSI report configuration, the UE may receive a downlink control information (DCI) triggering the CSI reporting. For example, the DCI may be received in a slot n. The DCI trigger may activate a CSI-RS resource the UE monitors for CSI-RS (e.g., aperiodic CSI-RS). After a duration of t slots, the UE receives the associated CSI-RS in slot n+t. The UE computes the CSI based on the received CSI-RS and determines whether to sends the CSI report (e.g., an aperiodic CSI report) or whether to not update the CSI report, based on the delay, y, between when the DCI trigger is received (in slot n) and computing and preparing the CSI report for sending (in the slot n+y) and/or a delay between when the CSI is received and the CSI report (y−t).

In some examples, the UE is configured with one or more time thresholds for CSI reporting. If the delay y is equal to or greater than a first time threshold Z and the the delay y−t is equal or greater than a second threshold Z′ then the UE transmits the CSI report; otherwise, the UE does not update the CSI reports (e.g., transmits a non-updated CSI report or “garbage” CSI report). The Tables800and900inFIG.8andFIG.9illustrate example thresholds. The first threshold, Z, may define a minimum number of symbols between the DCI triggering the CSI report and the transmission of the CSI report. The second thresholds, Z′, may define a minimum number of symbols between the associated CSI-RS transmission and transmission of the CSI report.

According to certain aspects, the thresholds used may be based on the number of FD units or the FD unit size for the CSI report. In some examples, a larger threshold is introduced (e.g., a Z4threshold), such as larger than the thresholds shown in the Tables800and900(Z1, Z2, and Z3). The additional larger threshold Z4may be used for fine granularity CSI reporting.

According to certain aspects, the UE determines a first set of thresholds to use when the number of FD units for reporting CSI is equal to or below a threshold and a second set of thresholds to use when the number of FD units for reporting CSI is above the threshold. In some examples, the first and second sets of thresholds each includes one or more thresholds Z for a minimum number of symbols between reception of DCI triggering CSI reporting and transmission of the CSI report and one or more thresholds Z′ for a minimum number of symbols between reception of CSI-RS and transmission of the CSI report. For example, if y≥Z and y−t≥Z, then the UE updates the CSI report. If y≤Z or y−t≤Z′, then the UE does not update the CSI report.

According to certain aspects, each of the second set of thresholds is greater than each of the first set of thresholds. For example, the first set of thresholds may include the Z and Z′ thresholds shown in Tables800and900. The second set of thresholds may include larger Z4and Z4′ thresholds. According to certain aspects, the threshold may be equal to the number of CQI subbands.

A BS (e.g., such as a BS110in the wireless communication network100) may perform complimentary operations by the BS the operations600performed by the UE.FIG.10is a flow diagram illustrating example operations1000for wireless communication. The operations1000may be performed, for example, by UE (e.g., such as a UE120in the wireless communication network100) for CSI processing, in accordance with certain aspects of the present disclosure. Operations1000may be implemented as software components that are executed and run on one or more processors (e.g., processor280ofFIG.2). Further, the transmission and reception of signals by the UE in operations1000may be enabled, for example, by one or more antennas (e.g., antennas252ofFIG.2). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., processor280) obtaining and/or outputting signals.

The operations1000may begin, at1005, by configuring a UE with a CSI reporting configuration. The CSI reporting configuration including a number of FD units and a FD unit size for CSI reporting based on a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both. For example, the BS may be restricted to configuring the UE with the number of FD units and FD units such that the computation can be supported by the number of CSI processing units at the UE and/or the time threshold for CSI processing. At1010, the BS receives the CSI report from the UE based on the configuration.

FIG.11illustrates a communications device1100that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated inFIG.6. The communications device1100includes a processing system1102coupled to a transceiver1108. The transceiver1108is configured to transmit and receive signals for the communications device1100via an antenna1110, such as the various signals as described herein. The processing system1102may be configured to perform processing functions for the communications device1100, including processing signals received and/or to be transmitted by the communications device1100.

The processing system1102includes a processor1104coupled to a computer-readable medium/memory1112via a bus1106. In certain aspects, the computer-readable medium/memory1112is configured to store instructions (e.g., computer-executable code) that when executed by the processor1104, cause the processor1104to perform the operations illustrated inFIG.6, or other operations for performing the various techniques discussed herein for CSI processing for CSI with fine granularity. In certain aspects, computer-readable medium/memory1112stores code1114for receiving a CSI report configuration; code1116for determining a number of CSI processing units (CPUs) to use for the CSI report based on the number of FD units or FD unit size for the CSI report; code1118for determining the CSI processing time thresholds based on the number of FD units or FD unit size for the CSI report; and/or code1120for processing the CSI report based on the determination(s). In certain aspects, the processor1104has circuitry configured to implement the code stored in the computer-readable medium/memory1112. The processor1104includes circuitry1122for receiving a CSI report configuration; circuitry1124for determining a number of CPUs to use for the CSI report based on the number of FD units or FD unit size for the CSI report; circuitry1126for determining CSI processing time thresholds based on the number of FD units or FD unit size for the CSI report; and/or circuitry1428for processing the CSI report based on the determination(s).

FIG.12illustrates a communications device1200that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated inFIG.10. The communications device1200includes a processing system1202coupled to a transceiver1208. The transceiver1208is configured to transmit and receive signals for the communications device1200via an antenna1210, such as the various signals as described herein. The processing system1202may be configured to perform processing functions for the communications device1200, including processing signals received and/or to be transmitted by the communications device1200.

The processing system1202includes a processor1204coupled to a computer-readable medium/memory1212via a bus1206. In certain aspects, the computer-readable medium/memory1212is configured to store instructions (e.g., computer-executable code) that when executed by the processor1204, cause the processor1204to perform the operations illustrated inFIG.10, or other operations for performing the various techniques discussed herein for CSI processing for CSI with fine granularity. In certain aspects, computer-readable medium/memory1212stores code1214for configuring a UE with a CSI report configuration; and/or code1216for receiving the CSI report. In certain aspects, the processor1204has circuitry configured to implement the code stored in the computer-readable medium/memory1212. The processor1204includes circuitry1218for configuring a UE with a CSI report configuration; and/or circuitry1220for receiving the CSI report based on the determination(s).

Example Aspects

In a first aspect, a method for wireless communications by a user equipment (UE) includes receiving a channel state information (CSI) reporting configuration. The CSI reporting configuration includes a number of frequency domain (FD) units and a FD unit size for CSI reporting. The UE determines a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both, to use for processing the CSI report based on the number of FD units or the FD unit size. The UE processes the CSI report based on the determination.

In a second aspect, in combination with the first aspect, the CSI includes compressed subband precoding matrix indicator (PMI) feedback.

In a third aspect, in combination with one or more of the first and second aspects, an FD unit includes a subband.

In a fourth aspect, in combination with one or more of the first through third aspects, the CSI includes at least precoder information feedback and channel quality indicator (CQI) feedback; the FD unit size for the precoder information feedback is determined based on a subband size for the CQI divided by a predefined integer; and the UE determines a total number of FD units as a total number of subbands for the CQI multiplied by the predefined integer.

In a fifth aspect, in combination with one or more of the first through fourth aspects, processing the CSI report based on the determination includes computing the CSI using the determined number of CSI processing units.

In a sixth aspect, in combination with one or more of the first through fifth aspects, determining the number of CSI processing units to use includes determining a first number of CSI processing units to use when the number of FD units for reporting CSI is equal to or below a first threshold, or when the FD unit size for reporting CSI is equal to or larger than a second threshold; and determining a second number of CSI processing units to use when the number of FD units for reporting precoder information feedback is above the first threshold, or when the FD unit size for reporting CSI is below the second threshold.

In a seventh aspect, in combination with one or more of the first through sixth aspects, the second number of CSI processing units is equal to the first number of CSI processing units multiplied by an integer.

In an eighth aspect, in combination with one or more of the first through seventh aspects, the UE determines the integer based on at least one of: the number of FD units for CSI reporting or the FD unit size.

In a ninth aspect, in combination with one or more of the first through third eighth aspects, the UE determines the integer based on at least one of: a ratio of the number of FD units for CSI reporting to the first threshold or a ratio of the second threshold to the FD unit size.

In a tenth aspect, in combination with one or more of the first through ninth aspects, the first threshold includes the total number of CQI subband contained in a bandwidth part (BWP) and/or the second threshold is equal to the CQI subband size.

In an eleventh aspect, in combination with one or more of the first through tenth aspects, the CSI report configuration configures one or more CSI reference signal (CSI-RS) resources for channel measurement and the first and second number of CSI processing units scales with the number of CSI-RS resources configured for channel measurement.

In a twelfth aspect, in combination with one or more of the first through eleventh aspects, determining the at least one time threshold to use includes determining a first set of time thresholds to use when the number of FD units for reporting CSI is equal to or below a threshold; and determining a second set of time thresholds to use when the number of FD units for reporting CSI is above the threshold.

In a thirteenth aspect, in combination with one or more of the first through twelfth aspects, each of the second set of time thresholds is greater than each of the first set of time thresholds.

In a fourteenth aspect, in combination with one or more of the first through thirteenth aspects, the first and second sets of time thresholds each includes one or more first time thresholds for a minimum timing between reception of downlink control information (DCI) triggering CSI reporting and transmission of the CSI report; and one or more second time thresholds for a minimum timing between reception of CSI reference signals (CSI-RS) and transmission of the CSI report.

In a fifteenth aspect, in combination with one or more of the first through fourteenth aspects, determining whether to update the CSI report includes updating the CSI report when the both of the determined first and second time thresholds are satisfied; and sending a non-updated CSI report when at least one of first and second time thresholds are not satisfied.

In a sixteenth aspect, a method for wireless communications by a base station (BS) includes configuring a user equipment (UE) with a channel state information (CSI) reporting configuration. The CSI reporting configuration including a number of frequency domain (FD) units and a FD unit size for CSI reporting based on a number of CSI processing units at the UE, at least one time threshold for CSI processing, or both. The BS receives the CSI report from the UE based on the configuration.

In a seventeenth aspect, in combination with the sixteenth aspect, the CSI includes compressed subband precoding matrix indicator (PMI) feedback.

In an eighteenth aspect, in combination with one or more of the sixteenth and seventeenth aspects, the CSI includes at least precoder information feedback and channel quality indicator (CQI) feedback; the FD unit size for the precoder information feedback is determined based on a subband size for the CQI divided by a predefined integer; and the BS determines a total number of FD units as a total number of subbands for the CQI multiplied by the predefined integer.

In a nineteenth aspect, in combination with one or more of the sixteenth through eighteenth aspects, determining the number of CSI processing units includes determining a first number of CSI processing units when the number of FD units for reporting CSI is equal to or below a first threshold, or when the FD unit size for reporting CSI is equal to or larger than a second threshold; and determining a second number of CSI processing units when the number of FD units for reporting precoder information feedback is above the first threshold, or when the FD unit size for reporting CSI is below the second threshold.

In a twentieth aspect, in combination with one or more of the sixteenth through nineteenth aspects, the second number of CSI processing units is equal to the first number of CSI processing units multiplied by an integer.

In a twenty-firth aspect, in combination with one or more of the sixteenth through twentieth aspects, the BS determines the integer based on at least one of: the number of FD units for CSI reporting or the FD unit size.

In a twenty-second aspect, in combination with one or more of the sixteenth through twenty-first aspects, the BS determines the integer based on at least one of: a ratio of the number of FD units for CSI reporting to the first threshold or a ratio of the second threshold to the FD unit size.

In a twenty-third aspect, in combination with one or more of the sixteenth through twenty-second aspects, the first threshold includes the total number of CQI subband contained in a bandwidth part (BWP) and/or the second threshold is equal to the CQI subband size.

In a twenty-fourth aspect, in combination with one or more of the sixteenth through twenty-third aspects, the CSI report configuration configures one or more CSI reference signal (CSI-RS) resources for channel measurement; and the first and second number of CSI processing units scales with the number of CSI-RS resources configured for channel measurement.

In a twenty-fifth aspect, in combination with one or more of the sixteenth through twenty-fourth aspects, determining the at least one time threshold includes determining a first set of time thresholds when the number of FD units for reporting CSI is equal to or below a threshold; and determining a second set of time thresholds when the number of FD units for reporting CSI is above the threshold.

In a twenty-sixth aspect, in combination with one or more of the sixteenth through twenty-fifth aspects, each of the second set of time thresholds is greater than each of the first set of time thresholds.

In a twenty-seventh aspect, in combination with one or more of the sixteenth through twenty-sixth aspects, the first and second sets of time thresholds each includes one or more first time thresholds for a minimum timing between reception of downlink control information (DCI) triggering CSI reporting and transmission of the CSI report; and one or more second time thresholds for a minimum timing between reception of CSI reference signals (CSI-RS) and transmission of the CSI report.

In a twenty-eighth aspect, in combination with one or more of the sixteenth through twenty-seventh aspects, the BS determines the CSI report is an updated CSI report when the both of the determined first and second time thresholds are satisfied; and determines the CSI report is a non-updated CSI report when at least one of first and second time thresholds are not satisfied.

In an LTE or LTE-A network, a set of one or more base stations may define an eNodeB (eNB). In other examples (e.g., in a next generation, a new radio (NR), or 5G network), a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more DUs, in communication with a CU, may define an access node (e.g., which may be referred to as a BS, 5G NB, next generation NodeB (gNB or gNodeB), transmission reception point (TRP), etc.). A BS or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a BS or DU to a UE) and uplink channels (e.g., for transmissions from a UE to BS or DU). In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB) and/or a NB subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and next generation NodeB (gNB or gNodeB), NR BS, 5G NB, access point (AP), or transmission reception point (TRP) may be interchangeable.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in the home, etc.). ABS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS.