WO2020220374A1

WO2020220374A1 - Coefficient determination for type-ii compressed csi reporting with reduced overhead

Info

Publication number: WO2020220374A1
Application number: PCT/CN2019/085414
Authority: WO
Inventors: Liangming WU; Chenxi HAO; Qiaoyu Li; Yu Zhang; Chao Wei
Original assignee: Qualcomm Incorporated
Priority date: 2019-05-02
Filing date: 2019-05-02
Publication date: 2020-11-05
Also published as: WO2020221371A1

Abstract

Certain aspects of the present disclosure provide techniques for channel state information (CSI) reporting with reduced overhead that avoids CSI omission. A method that may be performed by a user equipment (UE) includes receiving a CSI report configuration. The CSI report configuration configures the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank. The UE determines an actual number of linear combination coefficients to report per rank based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank. The UE sends a CSI report based on the actual number of linear combination coefficients to report per rank.

Description

COEFFICIENT DETERMINATION FOR TYPE-II COMPRESSED CSI REPORTING WITH REDUCED OVERHEAD

BACKGROUND

Field of the Disclosure

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

Description of Related Art

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc. ) . Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few.

In some examples, a wireless multiple-access communication system may include a number of base stations (BSs) , which are each capable of simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs) . 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, next generation NodeB (gNB or gNodeB) , 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 a BS or DU) .

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. New radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) . To these ends, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR and LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include reduced overhead for channel state information (CSI) reporting.

Certain aspects provide a method for wireless communication by a user equipment (UE) . The method generally includes receiving a CSI report configuration. The CSI report configuration configures the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank. The method generally includes determining an actual number of linear combination coefficients to report per rank based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank. The method generally includes sending a CSI report based on the actual number of linear combination coefficients to report per rank.

In some examples, sending the CSI report based on the actual number of linear combination coefficients to report per rank includes computing the CSI report based on the determined actual number of linear combination coefficients to report per rank and sending the CSI report with all of the actual number of linear combination coefficients to report per rank.

In some examples, determining the actual number of linear combination coefficients per rank is based on a comparison of the configured number of linear combination coefficients and the computed number of supported linear combination coefficients per rank.

In some examples, determining the actual number of linear combination coefficients per rank includes for rank 1, determining the actual number of linear combination coefficients to report, per layer, as a smaller of the configured number of linear combination coefficients and a first computed number of supported linear combination coefficients per rank. In some examples, determining the actual number of linear combination coefficients per rank includes for rank 2, determining the actual number of linear combination coefficients to report, per layer, as a smaller of the configured number of linear combination coefficients and one-half a second number of supported linear combination coefficients per rank. In some examples, determining the actual number of linear combination coefficients per rank includes for rank 3, determining the actual number of linear combination coefficients to report across all layers as a smaller of twice the configured number of linear combination coefficients and a computed third number of supported linear combination coefficients per rank. In some examples, determining the actual number of linear combination coefficients per rank includes for rank 4, determining the actual number of linear combination coefficients to report across all layers as a smaller of twice the configured number of linear combination coefficients and a computed number of supported linear combination coefficients per rank.

In some examples, the CSI report is sent in a two-part uplink control information (UCI) . In some examples, determining the computed number of supported linear combination coefficients per rank is based on a supported payload size for the second part of the UCI and a number of bits for reporting other parameters in the second part UCI.

In some examples, the other parameters in the second part of the UCI comprise at least one of: a number of beams selected for the CSI report; a number of frequency domain basis selected for the frequency domain compression; a number of coefficients selected for the CSI report; a number of strongest coefficient indicators; and a quantization of the linear combination coefficients.

In some examples, the method includes determining the number of strongest coefficient indicators based on the rank and the configured number of linear combination coefficients per rank.

In some examples, the number of supported linear combination coefficients per rank is computed as a quotient of a difference of the supported payload size for the second part of the UCI and the number of bits for reporting the other parameters in the second part UCI and a quantization of the linear combination coefficients.

In some examples, the number of supported linear combination coefficients per rank is computed iteratively.

In some examples, the UE is configured to report a plurality of CSI reports. In some examples, the method includes determining a priority order of the plurality of CSI reports. In some examples, the method includes determining available payload of the second part of the UCI for lower priority CSI reports as a difference of the supported payload size and a payload size of higher priority CSI reports.

In some examples, the method includes sending an indication to the BS of whether the reported number of linear combination coefficients is smaller than the computed number of linear combination coefficients.

In some examples, the indication is sent via a 1-bit indication in a first part of the UCI or via a CSI report parameter value that is not supported.

In some examples, sending the CSI report includes sending a channel quality indicator (CQI) report that is not associated with the precoding matrix information when the configured number of linear combination coefficients to report per rank is greater than the maximum supported payload size.

Certain aspects provide a method for wireless communication by a base station (BS) . The method generally includes sending a UE a CSI report configuration. The CSI report configuration configures the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank. The method generally includes determining an actual number of linear combination coefficients per rank the UE reports based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of linear combination coefficients per rank the UE supports for CSI reporting. The method generally includes processing a CSI report from the UE based on the determined actual number of linear combination coefficients per rank the UE reports.

In some examples, processing a CSI report based on the actual number of linear combination coefficients to report per rank includes treating the CSI report as an invalid report when the CSI report comprises a greater number of linear combination coefficients than the determined actual number of linear combination coefficients the UE supports for reporting per rank.

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

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example telecommunications system, in accordance with certain aspects of the present disclosure.

FIG. 2 illustrates example oversampled beam for Type 1 channel state information (CSI) feedback, in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates example oversampled beam for Type I1 CSI feedback, in accordance with certain aspects of the present disclosure.

FIG. 4 is a block diagram showing example precoder matrix feedback without frequency domain compression and with frequency domain compression, in accordance with certain aspects of the present disclosure.

FIG. 5 is a block diagram showing example precoder matrix feedback with frequency domain compression for multiple layers, in accordance with certain aspects of the present disclosure.

FIG. 6 illustrates example uplink control information (UCI) part one for a CSI report, in accordance with certain aspects of the present disclosure.

FIG. 7 illustrates example UCI part two for a CSI report, in accordance with certain aspects of the present disclosure.

FIG. 8 is an example matrix illustrating basis selection reporting for CSI reporting, in accordance with certain aspects of the present disclosure.

FIG. 9 is an example matrix illustrating a coefficient subset for CSI reporting, in accordance with certain aspects of the present disclosure.

FIG. 10 is a flow diagram illustrating example operations for wireless communication by a user equipment (UE) , in accordance with certain aspects of the present disclosure.

FIG. 11 is a flow diagram illustrating example operations for wireless communication by base station (BS) , in accordance with certain aspects of the present disclosure.

FIG. 12 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

FIG. 13 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

FIG. 14 is a block diagram conceptually illustrating a design of an example BS and UE, in accordance with certain aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for channel state information (CSI) reporting.

In certain systems, a user equipment (UE) is configured for CSI reporting. As discussed in more detail below with respect to FIGs. 3-9, In some new radio systems (e.g., 5G NR) , the UE is configured for Type-II reporting of frequency domain compressed CSI feedback. The UE can be configured with a number of linear combination coefficients to report per rank, K ₀. The UE is also configured with resources for CSI reporting. In some cases, the resources configured for the CSI reporting are insufficient to report configured with a number of linear combination coefficients to report per rank, K ₀. In this case, the UE may omit some of the linear combination coefficients to be reported (e.g., even though the UE may have computed CSI for the configured with a number of linear combination coefficients to report per rank, K ₀) . In an illustrative example, Release-15 5G NR defines rules for CSI omission on certain even/odd subbands. Omitting CSI may lead performance degradation.

Aspects of the present disclose provide for CSI reporting with overhead reduction and that can avoid CSI omission. According to certain aspects, the UE can determine a supported payload size for the UCI. The UE can determine the supported number of coefficients per rank for CSI reporting, K _r, and then determine whether it can report the configured number of linear combination coefficients to report per rank, K ₀, or a smaller computed number of supported coefficients. In this case, the UE computed the CSI report and reports the coefficients based on the actual number of supported coefficients. Thus, the overhead can be reduced and CSI omission avoided.

The following description provides examples of CSI reporting, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

FIG. 1 illustrates an example wireless communication network 100 in which aspects of the present disclosure may be performed. For example, the wireless communication network 100 may be an NR system (e.g., a 5G NR network) .

As illustrated in FIG. 1, the wireless communication network 100 may include a number of base stations (BSs) 110 and other network entities. Each BS 110 may provide communication coverage for a particular geographic area, sometimes referred to as a “cell” , which may be stationary or may move according to the location of a mobile BS 110. In some examples, the BSs 110 may be interconnected to one another and/or to one or more other network nodes (not shown) in wireless communication network 100 through various types of backhaul interfaces (e.g., a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. In the example shown in FIG. 1, the

BSs

110a, 110b and 110c may be macro BSs for the

macro cells

102a, 102b and 102c, respectively. The BS 110x may be a pico BS for a pico cell 102x. The BSs 110y and 110z may be femto BSs for the

femto cells

102y and 102z, respectively. A BS may support one or multiple cells.

The BSs 110 communicate with user equipment (UEs) 120 in the wireless communication network 100. The UEs 120 (e.g., 120x, 120y, etc. ) may be dispersed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile. As shown in FIG. 1, the UE 120a includes a CSI reporting manager 122. The CSI reporting manager 122 may be configured to determine an actual number of linear combination coefficients to report per rank based, at least in part, on a configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank, in accordance with certain aspects of the present disclosure. The CSI reporting manager 122 may be configured to compute the CSI report and the send the CSI report based on the determined actual number of linear combination coefficients to report per rank. Thus, the UE 120a may be compute and report the CSI to the BS 110a without omitting any of the coefficients, and with reduced overhead. As shown in FIG. 1, the BS 110a includes a CSI Report manager 112. The CSI report manager 112 may be configured to configure the UE 120a with a CSI reporting configuration, configuring the number of linear combination coefficients to report per rank. The CSI report manager 112 may be configured to determine the actual number of linear combination coefficients for the UE 120a report per rank based, at least in part, on a configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank supported by the UE 120a, in accordance with certain aspects of the present disclosure. The BS 110a may process a CSI report received from the UE 120a based on the determined actual number of linear combination coefficients per rank for the UE 120a to report.

Wireless communication network 100 may also include relay stations (e.g., relay station 110r) , also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110a or a UE 120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE 120 or a BS 110) , or that relays transmissions between UEs 120, to facilitate communication between devices.

A network controller 130 may couple to a set of BSs 110 and provide coordination and control for these BSs 110. The network controller 130 may communicate with the BSs 110 via a backhaul. The BSs 110 may also communicate with one another (e.g., directly or indirectly) via wireless or wireline backhaul.

As mentioned above, aspects of the present disclosure relate to CSI reporting. 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 feedback 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 (e.g., the UE 120a) , quantized, and fed back to the transmitter (e.g., the BS 110a) .

FIG. 2 and FIG. 3 illustrate example Type-I and Type-II CSI feedback, respectively. The BS 210 may configure the UE 220 with a CSI report configuration or with multiple CSI report configurations. The BS 210 may provide the CSI report configuration to the UE 220 via higher layer signaling, such as radio resource control (RRC) signaling (e.g., via a CSI-ReportConfig information element (IE) ) .

The CSI report configuration may configure the time and frequency resources used by the UE 220 to report CSI. For example, 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., via a CSI-ResourceConfig IE) . The CSI-RS resources provide the UE 220 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 may configure the UE 120a 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 110 may signal the UE a CSI report trigger indicating for the UE 220 to send a CSI report for one or more CSI-RS resources, or configuring the CSI-RS report trigger state (e.g., CSI-AperiodicTriggerStateList and CSI-SemiPersistentOnPUSCH-TriggerStateList) . 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 220 may report the CSI feedback based on the CSI report configuration and the CSI report trigger. For example, the UE 220 may measure the channel associated with CSI for the triggered CSI-RS resources. Based on the measurements, the UE 220 may select a preferred CSI-RS resource. The UE 220 reports the CSI feedback for the selected CSI-RS resource.

The CSI report configuration also configures the CSI parameters (sometimes referred to as quantities) to be reported. Three codebooks may include Type I single panel, Type I multi-panel, and Type II single panel. Regardless which codebook is used, the CSI report may include at least the Channel Quality Indicator (CQI) , precoding matrix indicator (PMI) , CSI-RS resource indicator (CRI) , and rank indicator (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 include 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. FIG. 2 illustrates example oversampled beam for Type 1 CSI feedback, in accordance with certain aspects of the present disclosure. As shown in FIG. 2, the BS 210 may have a plurality of transmit (TX) beams (e.g., TX beams 211, 212, ..., 217) . The UE 220 can feed back to the BS 210 an index of a preferred beam b ₁ (e.g., TX beam 214) or beams of the candidate beams. For example, the UE 220 may feed back the precoding vector w for the l-th layer:

, where b represents the oversampled beam (e.g., discrete Fourier transform (DFT) beam) , for both polarizations, and

is the co-phasing.

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.

As shown in FIG. 3, the preferred beam can by a combination of beams b ₁ and b ₂ and associated quantized coefficients c ₁ and c ₂ (e.g., c ₁b ₁ + c ₂b ₂) , and the UE 220 can feedback the selected beams and the coefficients to the BS 210. The UE 220 may be configured to report at least a Type II precoder across configured frequency domain (FD) units. The UE 220 may report wideband (WB) PMI and/or subband (SB) PMI as configured. For example, the UE 220 may rcport thc prccoding vector w for the l-th layer as:

, where

is the wideband amplitude per polarization,

is the subband amplitude per polarization, c _l, i is subband phase per polarization, and b _i is the selected beam per polarization. The precoder matrix w with the linear combination coefficients for the selected subset of beams (e.g., using spatial compression) for the cross-polarization (e.g., +45/-45) across the configured FD units can also be represented as:

where N ₃ corresponds to the number of frequency units (e.g., subbands, resource blocks (RBs) , etc. ) .

As shown in FIG. 4, the precoder matrix W for certain systems (e.g., Release-15 5G NR systems) is based on the spatial domain compression matrix W ₁ matrix and the W ₂ matrix for reporting (for cross-polarization) the linear combination coefficients for the selected beams (2L) across the configured FD units.

The number of FD units (e.g., subbands) for CSI reporting may be relatively large, leading to large overhead for Type-II CSI feedback. To reduce the CSI overhead, certain systems (e.g., Release 16 5G NR systems) may also use frequency domain compression by transferring the subband coefficients into another domain (e.g., DFT basis domain) . The CSI reporting overhead may be further reduced by selecting only the dominant coefficients associated with each beam in the transformed domain to feedback Therefore the overall number of coefficients, and thereby the overhead, can be reduced.

As shown in FIG. 4, a FD compression matrix

may be used to compress the W ₂ matrix size to 2L X M, where M ＜ N ₃ as

where the precoder matrix W may have Ntx= 2N ₁N ₂ rows (spatial domain, number of ports) and N ₃ columns (FD compression unit, consisting of RBs or reporting subbands) . The

matrix consists of the linear combination coefficients (amplitude and co-phasing) . The

matrix is composed of the basis vectors (each row is a basis vector) used to perform the compression in the frequency domain. In some examples, the basis vectors in W _f are derived from a certain number of columns in a DFT matrix. In

one row corresponds to one spatial beam in W ₁, and one entry therein represents the coefficient of one tap for this spatial beam. An entry in

may correspond to a row of

i.e. a column of W _f. Thus, the precoder matrix may be given by:

where the DFT compression basis is given by:

of size M _i × N ₃,

and where M _i is dimension of the compressed domain. The coefficients may be given by:

and the dimension of the compressed domain is M _i ＜ N ₃. As discussed in more detail below, the number of non-zero coefficients for each may be smaller than M.

As shown in FIG. 5, the precoder matrix feedback with frequency domain compression may be done for multiple layers.

The UE (e.g., UE 220) may report the CSI in uplink control information (UCI) . In some examples, the CSI is reported in a two-part UCI. FIG. 6 illustrates example UCI part one 600 for a CSI report, in accordance with certain aspects of the present disclosure. The UCI part one may be of fixed length. As shown in FIG. 6, in the UCI part one 600 the UE (e.g., UE 220) may transmit RI, CQI, number of non-zero coefficients (NNZC) , a number of FD basis, a size of an intermediate FD set, a bitmap size of a bitmap used to indicate coefficient selection, and/or a beam sufficiency indicator (BSI) . The CQI may be calculated based on the RI. In some examples, the NNZC may be indicated per layer (e.g., NNZC #1, NNZC #2, ..., etc. ) . In some examples, the NNZC may indicate the total NNZCs across all layers. In some examples, the number of FD basis M’ may less than the M configured FD basis. The indication of size of an intermediate FD set may determine a bitwidth of the FD basis selection. The BSI could also be indicated via a value (e.g., 0) of the NNZC. The BSI may indicate whether a configured p or β is sufficient.

FIG. 7 illustrates example UCI part two 700 for a CSI report, in accordance with certain aspects of the present disclosure. The UCI part one may be dynamic. As shown in FIG. 7, in the UCI part two 700 the UE (e.g., UE 220) may transmit for the supported layers (e.g., layers 0 to RI-1) the SD beam selection, FD basis selection, coefficient selection, strongest coefficient indication (SCI) , and/or coefficient quantization. The SD beam selection may indicate the selected beams (e.g., the subset of 2L beams) . As shown in FIG. 8, the UE may report a subset of selected basis of the

matrix. The FD basis selection may indicate the selected frequency domain basis (e.g., used for each beam, tap) . In some examples, the FD basis selection may be reported individually for each layer (e.g., via a bitmap or combination number) . In some examples, the FD basis selection is reported via a two-stage report. The first stage may report/configure an intermediate (e.g. union) set for all layers and the second stage may report each layer individually from the set reported in the first stage. In some examples, the coefficient selection may be reported via a bitmap (e.g., a 2LM size bitmap) . In some examples, the coefficient selection may be reported via two-steps, with the bitwidth depending on the N _b. The SCI may depend on the NNZC and configured K ₀. For example, the SCI may be based on the NNZC for a layer i (e.g., log ₂

) , based on the maximum NNZC for a laver i (e.g., log ₂ K ₀) , or based on a total NNZC for a layer i (e.g., log ₂ min

As discussed above, the CSI report configuration configures the UE to report a maximum number of coefficients per rank, K ₀. As shown in FIG. 9, UE can select the subsetK ₀ ＜ 2LM of the linear combination coefficients of the

matrix for reporting. In some cases; however, the UE may not have sufficient resources for reporting the configured K ₀ number of coefficients per rank. For example, the UE may be allocated physical uplink shared channel (PUSCH) for the CSI reporting. Based on the amount of PUSCH resources allocated and the resources used for reporting the UCI part one, the remaining resources for reporting the configured K ₀ number of coefficients per rank dynamic UCI part two. Thus, the UE may omit reporting of some of the CSI. For example, the UE may omit some even/odd subbands for reporting (e.g., according to configured CSI priority/omission rules) . The CSI omissions may lead to performance degradation. In some cases, the UE computes the CSI report using the configured K ₀ number of coefficients per rank, but then omits (e.g., drops/does not report) some the coefficients from the CSI report, which may be an inefficient use of resources.

Therefore, techniques for CSI reporting are desirable, which may reduce overhead and avoid CSI omission.

Example Coefficient Determination For Type-II Compressed CSI Reporting With Reduced Overhead

Accordingly, aspects of the present disclose provide for CSI reporting with overhead reduction and that can avoid CSI omission. According to certain aspects, the UE can determines an actual number coefficients to report per layer (or per rank) based on a supported payload size for the UCI, a supported number of coefficients per rank for CSI reporting, K _r, and the configured number of linear combination coefficients to report per rank, K ₀. Thus, the UE can compute and report the CSI based on the determined actual number of coefficients, which avoid CSI omissions and reduced CSI overhead.

FIG. 10 is a flow diagram illustrating example operations 1000 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 1000 may be performed, for example, by UE (e.g., such as a UE 120a in the wireless communication network 100) . Operations 1000 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 1480 of FIG. 14) . Further, the transmission and reception of signals by the UE in operations 1000 may be enabled, for example, by one or more antennas (e.g., antennas 1452 of FIG. 14) . 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., controller/processor 1480) obtaining and/or outputting signals.

The operations 1000 may begin, at 1005, by receiving a CSI report configuration, configuring the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank (K ₀) . The K ₀ may be a predefined value. In some examples, the K ₀ may be configured via radio resource control (RRC) signaling or dynamically via downlink control information (DCI) .

As discussed above, the CSI report configuration may also configure the UE with the CSI resources for reporting, with one or more CSI report triggers, with the CSI report quantities, etc. In some examples, the CSI report configuration configures the UE for reporting Type-II frequency domain precoding matrix feedback per layer, per selected beam, for example as described above with respect to FIGs. 3-5. In some examples, the CSI report configuration configures the UE for reporting one or more of the quantities described above for the two-part UCI in FIG. 6 and FIG. 7.

At 1010, the UE determines an actual number of linear combination coefficients to report per rank based, at least in part, on the configured number of linear combination coefficients to report per rank (K ₀) and a computed number of supported linear combination coefficients per rank (K _r) .

According to certain aspects, the determining, at 1010, the actual number of linear combination coefficients to report per rank includes computing a supported payload size (P _max) for the part 2 of the UCI (e.g., a maximum payload size) ; computing the supported number (e.g., a maximum number) of coefficients per rank the UE can report (K _r) based on the P _max; and determining the actual number of linear combination coefficients to report per rank based on a comparison of the computed K _r and the configured K ₀.

In some examples, the UE is configured to report the CSI via a two-part UCI. In some examples, the UE computes the supported payload size (P _max) for the part 2 of the UCI based on a resource allocation for the part 2 of the CSI and a configured coding rate. In some examples, the resource allocation allocates physical uplink shared channel (PUSCH) resources for the CSI reporting. In some examples, the resource allocation is indicated dynamically via DCI. In some examples, the configured coding rate is a coding rate configured or the PUSCH. In some examples, the coding rate is configured by upper layer signaling, such as RRC signaling.

In some examples, the UE determines the computed the supported number of coefficients per rank the UE can report (K _r) based on the P _max. In some examples, the UE determines the computed number of supported linear combination coefficients per rank (K _r) based on a supported payload size for the second part of the UCI and a number of bits for reporting other parameters in the second part UCI. In some examples, the number of supported linear combination coefficients per rank is computed as a quotient of a difference of the supported payload size for the second part of the UCI and the number of bits for reporting the other parameters in the second part UCI and a quantization of the linear combination coefficients. In some examples, the other parameters in the second part of the UCI comprise a number of beams selected for the CSI report; a number of frequency domain basis selected for the frequency domain compression; a number of coefficients selected for the CSI report; a number of strongest coefficient indicators; and/or a quantization of the linear combination coefficients. For example, with respect to the example CSI parameters in the part 1 UCI 600 shown in FIG. 6, for rank 1, the K ₁= [ (P _max -N _SD -N _FD -N _CS -N _SI) /Q] , where N _SD, N _FD, N _CS, N _SI, stand for the number of payload bits for spatial domain basis, frequency domain basis, coefficient selection, strongest coefficient indication, respectively, and Q stands for the number of quantization bits per coefficient (e.g., amplitude, phase) .

In some examples, the N _SI may be associated with the K _r, for example, N _SI= log ₂K ₁. In some examples, the number of strongest coefficient indicators may be determined based on the rank and the configured number of linear combination coefficients per rank. In some examples, the N _SI may be enforced to a value for computation and payload assignment. For example, the N _SI may be enforced N _SI= rank × [log ₂K ₀] for

ranks

1 and 2 and enforced as N _SI= rank × [log ₂2K ₀] for ranks 3 and 4 In some examples, the K _r may be determined progressively (e.g., iteratively) . For example, for rank 1, for the equation [log ₂K ₁] + QK ₁= [P _max -N _SD -N _FD -N _CS -N _SI] , the left side of the equation may be monotonically increased to obtain the actual K ₁ value in a limited number of iterations.

In some examples, the determining, at 1010, the actual number of linear combination coefficients per rank is based on a comparison of the configured number of linear combination coefficients (K ₀) and the computed number of supported linear combination coefficients per rank (K _r) . For example, the determining, at 1010, the actual number of linear combination coefficients per rank may include, for rank 1, determining the actual number of linear combination coefficients to report, per layer, as a smaller of the configured number of linear combination coefficients and a first computed number of supported linear combination coefficients per rank (e.g., min (K ₁, K ₀) ) . The determining, at 1010, the actual number of linear combination coefficients per rank may include, for rank 2, determining the actual number of linear combination coefficients to report, per layer, as a smaller of the configured number of linear combination coefficients and one-half a second number of supported linear combination coefficients per rank (e.g., min ( (K ₂/2) , K ₀) ) . The determining, at 1010, the actual number of linear combination coefficients per rank may include, for rank 3, determining the actual number of linear combination coefficients to report across all layers as a smaller of twice the configured number of linear combination coefficients and a computed third number of supported linear combination coefficients per rank (e.g., min (K ₃, 2K ₀) . The determining, at 1010, the actual number of linear combination coefficients per rank may include, for rank 4, determining the actual number of linear combination coefficients to report across all layers as a smaller of twice the configured number of linear combination coefficients and a computed number of supported linear combination coefficients per rank (e.g., min (K ₄, 2K ₀) .

At 1015, the UE sends a CSI report based on the actual number of linear combination coefficients to report per rank. For example, sending the CSI report based on the actual number of linear combination coefficients to report per rank may include computing the CSI report based on the determined actual number of linear combination coefficients to report per rank and sending the CSI report with all of the actual number of linear combination coefficients to report per rank (e.g., without any CSI omission) . In some examples, the CSI report is sent as a two-part UCI.

In some examples, the UE may be configured to report a plurality of CSI reports. For multiple CSI reports, the CSI may be computed in serial. In some examples, the UE determines a priority order of the plurality of CSI reports and determines available payload of the second part of the UCI for lower priority CSI reports as a difference of the supported payload size and a payload size of higher priority CSI reports. For example, the payload for a first CSI report (e.g., a higher priority CSI report) may be computed as P ₁, and then the remaining UCI payload for a second CSI report (e.g., a lower priority CSI report) may computed as P ₂ = P _max -P ₁. The UE can use the P ₂ to determine the number of coefficients for the second CSI report (and calculate and report the second CSI report accordingly) .

In some examples, the UE determines whether the allocated resources (e.g., the allocated PUSCH resources) are sufficient or insufficient to report the configured number of coefficients per rank (K ₀) . For example, the UE may determine whether the reported number of linear combination coefficients is smaller than the computed number of linear combination coefficients (K _r) . Based on the determination, the UE may send an indication to the BS of whether the reported number of linear combination coefficients is smaller than the computed number of linear combination coefficients. In some examples, the indication is sent via a 1-bit indication. In some examples, the indication is sent in a first part of the UCI (e.g., an explicit indication) . In some examples, the indication is provided (e.g., implicitly) via a CSI report parameter value that is not supported (e.g., a forbidden or non-supported CSI feedback report quantity) . In an illustrative example, the UE could report a RI=2 and 4 non-zero NNZC, which may be contradictory and forbidden in the CSI report, thereby indicating the insufficient CSI payload.

In some examples, when (e.g., if) the payload is insufficient, the UE may report a CQI report that is not associated with the precoding matrix information (e.g., the BS is not assumed to transmit a modulation coding scheme (MSC) with targeting block error rate (BLER) requirement with the UE reported CQI and PMI) . In some examples, when (e.g., if) the payload is insufficient, the UE may report a CQI report that is associated with the precoding matrix information

FIG. 11 is a flow diagram illustrating example operations 1100 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 1100 may be performed, for example, by a BS (e.g., such as a BS 110a in the wireless communication network 100) . The operations 1000 may be complimentary operations by the BS l l0a to the operations 1000 performed by the UE 120a. Operations 1100 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 1440 of FIG. 14) . Further, the transmission and reception of signals by the BS in operations 1100 may be enabled, for example, by one or more antennas (e.g., antennas 1434 of FIG. 14) . In certain aspects, the transmission and/or reception of signals by the BS may be implemented via a bus interface of one or more processors (e.g., controller/processor 1440) obtaining and/or outputting signals.

The operations 1100 may begin, at 1105, by sending a UE (e.g., UE 120a) a CSI report configuration. The CSI report configuration may configure the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank.

At 1110, the BS determines an actual number of linear combination coefficients per rank the UE reports based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of linear combination coefficients per rank the UE supports for CSI reporting. The BS may determine the actual number of linear combination coefficients per rank the UE reports as described above for the UE operations. For example, the BS may determine the actual number of linear combination coefficients per rank based on a comparison of the configured number of linear combination coefficients (K ₀) and the computed number of linear combination coefficients per rank (K _r) supported by the UE for CSI reporting. The BS may determine the computed number of linear combination coefficients per rank (K _r) supported by the UE for CSI reporting based on a resource allocation sent to the UE and report quantities configured in the CSI report configuration sent to the UE.

At 1115, the BS processes a CSI report from the UE based on the determined actual number of linear combination coefficients per rank the UE reports. For example, the BS is not expected to receive a CSI report with K _total or per layer K larger than the calculated K _r or K _r, l. The processing the CSI report, at 1115, based on the determined actual number of linear combination coefficients to report per rank may include treating the CSI report as an invalid report when the CSI report has a greater number of linear combination coefficients than the determined actual number of linear combination coefficients per rank the UE supports for CSI reporting.

In some examples, the BS receives an indication from the UE of whether the reported number of linear combination coefficients is smaller than the computed number of linear combination coefficients. In some examples, the indication is received via a 1-bit indication in a first part of the UCI or via a CSI report parameter value that is not supported. The BS may process the CSI report further based on the indication.

The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

FIG. 12 illustrates a communications device 1200 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein type-II frequency domain compressed CSI reporting with reduced overhead, such as the operations illustrated in FIG. 10. The communications device 1200 includes a processing system 1202 coupled to a transceiver 1208. The transceiver 1208 is configured to transmit and receive signals for the communications device 1200 via an antenna 1210, such as the various signals as described herein. The processing system 1202 may be configured to perform processing functions for the communications device 1200, including processing signals received and/or to be transmitted by the communications device 1200.

The processing system 1202 includes a processor 1204 coupled to a computer-readable medium/memory 1212 via a bus 1206. In certain aspects, the computer-readable medium/memory 1212 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 1204, cause the processor 1204 to perform the operations illustrated in FIG. 10, or other operations for performing the various techniques discussed herein for type-II frequency domain compressed CSI reporting with reduced overhead. In certain aspects, computer-readable medium/memory 1212 stores code 1214 for receiving a CSI report configuration, for example, configuring the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank, in accordance with certain aspects of the present disclosure; code 1216 for determining an actual number of linear combination coefficients to report per rank, for example, based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank, in accordance with certain aspects of the present disclosure; and code 1218 for sending a CSI report based on the actual number of linear combination coefficients to report per rank. In certain aspects, the processor 1204 has circuitry configured to implement the code stored in the computer-readable medium/memory 1212. The processor 1204 includes circuitry 1220 for receiving a CSI report configuration; circuitry 1222 for determining an actual number of linear combination coefficients to report per rank; and circuitry 1224 for sending a CSI report based on the actual number of linear combination coefficients to report per rank.

FIG. 13 illustrates a communications device 1300 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein type-II frequency domain compressed CSI reporting with reduced overhead, such as the operations illustrated in FIG. 11. The communications device 1300 includes a processing system 1302 coupled to a transceiver 1308. The transceiver 1308 is configured to transmit and receive signals for the communications device 1300 via an antenna 1310, such as the various signals as described herein. The processing system 1302 may be configured to perform processing functions for the communications device 1300, including processing signals received and/or to be transmitted by the communications device 1300.

The processing system 1302 includes a processor 1304 coupled to a computer-readable medium/memory 1312 via a bus 1306. In certain aspects, the computer-readable medium/memory 1312 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 1304, cause the processor 1304 to perform the operations illustrated in FIG. 11, or other operations for performing the various techniques discussed herein for type-II frequency domain compressed CSI reporting with reduced overhead. In certain aspects, computer-readable medium/memory 1312 stores code 1314 for receiving a CSI report configuration, for example, configuring the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank, in accordance with certain aspects of the present disclosure; code 1316 for determining an actual number of linear combination coefficients per rank the UE reports, for example, based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of linear combination coefficients per rank supported by the UE for CSI reporting, in accordance with certain aspects of the present disclosure; and code 1318 for processing a CSI report from the UE based on the determined actual number of linear combination coefficients the UE reports per rank. In certain aspects, the processor 1304 has circuitry configured to implement the code stored in the computer-readable medium/memory 1312. The processor 1304 includes circuitry 1320 for sending a CSI report configuration to a UE; circuitry 1322 for determining an actual number of linear combination coefficients the UE reports per rank; and circuitry 1324 for processing a CSI report from the UE based on the determined actual number of linear combination coefficients per rank the UE reports.

The techniques described herein may be used for various wireless communication technologies, such as NR (e.g., 5G NR) , 3GPP Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , single-carrier frequency division multiple access (SC-FDMA) , time division synchronous code division multiple access (TD-SCDMA) , and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA) , cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA network may implement a radio technology such as NR (e.g. 5G RA) , Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS) . LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP) . cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . NR is an emerging wireless communications technology under development.

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, 4G, and/or 5G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a subcarrier, a frequency channel, a tone, a subband, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

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 BS, next generation NodeB (gNB or gNodeB) , access point (AP) , distributed unit (DU) , carrier, or transmission reception point (TRP) may be used interchangeably. 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. ) . A BS 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.

A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE) , a cellular phone, a smart phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc. ) , an entertainment device (e.g., a music device, a video device, a satellite radio, etc. ) , a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are 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 (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a “resource block” (RB) ) may be 12 subcarriers (or 180 kHz) . Consequently, the nominal Fast Fourier Transfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz) , respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (e.g., 6 RBs) , and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively. In LTE, the basic transmission time interval (TTI) or packet duration is the 1 ms subframe.

NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. In some examples, 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. In some examples, 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. In NR, a subframe is still 1 ms, but the basic TTI is referred to as a slot. A subframe contains a variable number of slots (e.g., 1, 2, 4, 8, 16,... slots) depending on the subcarrier spacing. The NR RB is 12 consecutive frequency subcarriers. NR may support a base subcarrier spacing of 15 KHz and other subcarrier spacing may be defined with respect to the base subcarrier spacing, for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with the subcarrier spacing. The CP length also depends on the subcarrier spacing.

In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. Base stations are not the only entities that may function as a scheduling entity. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs) , and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may communicate directly with one another in addition to communicating with a scheduling entity.

In some examples, two or more subordinate entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE1) to another subordinate entity (e.g., UE2) without relaying that communication through the scheduling entity (e.g., UE or BS) , even though the scheduling entity may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using a licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum) .

FIG. 14 illustrates example components of BS 110a and UE 120 (e.g., in the wireless communication network 100 of FIG. 1) , which may be used to implement aspects of the present disclosure. For example, antennas 1452,

processors

1466, 1458, 1464, and/or controller/processor 1480 of the UE 120a and/or antennas 1434,

processors

1420, 1430, 1438, and/or controller/processor 1440 of the BS 110a may be used to perform the various techniques and methods described herein.

At the BS 110s, a transmit processor 1420 may receive data from a data source 1412 and control information from a controller/processor 1440. 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 processor 1420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor 1420 may also generate reference symbols, such as for the primary synchronization signal (PSS) , secondary synchronization signal (SSS) , and cell-specific reference signal (CRS) . A transmit (TX) multiple-input multiple-output (MIMO) processor 1430 may 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) 1432a-1432t. Each modulator 1432 may 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 modulators 1432a-1432t may be transmitted via the antennas 1434a-1434t, respectively.

At the UE 120a, the antennas 1452a-1452r may receive the downlink signals from the BS 110a and may provide received signals to the demodulators (DEMODs) in transceivers 1454a-1454r, respectively. Each demodulator 1454 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 1456 may obtain received symbols from all the demodulators 1454a-1454r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 1458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120a to a data sink 1460, and provide decoded control information to a controller/processor 1480.

On the uplink, at UE 120a, a transmit processor 1464 may receive and process data (e.g., for the physical uplink shared channel (PUSCH) ) from a data source 1462 and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor 1480. The transmit processor 1464 may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS) ) . The symbols from the transmit processor 1464 may be precoded by a TX MIMO processor 1466 if applicable, further processed by the demodulators in transceivers 1454a-1454r (e.g., for SC-FDM, etc. ) , and transmitted to the BS 110a. At the BS 110a, the uplink signals from the UE 120a may be received by the antennas 1434, processed by the modulators 1432, detected by a MIMO detector 1436 if applicable, and further processed by a receive processor 1438 to obtain decoded data and control information sent by the UE 120a. The receive processor 1438 may provide the decoded data to a data sink 1439 and the decoded control information to the controller/processor 1440.

The controllers/

processors

1440 and 1480 may direct the operation at the BS 110a and the UE 120a, respectively. The

memories

1442 and 1482 may store data and program codes for BS 110a and UE 120a, respectively. A scheduler 1444 may schedule UEs for data transmission on the downlink and/or uplink.

The controller/processor 1480 and/or other processors and modules at the UE 120a may perform or direct the execution of processes for the techniques described herein. As shown in FIG. 14, the controller/processor 1480 of the UE 120a has a CSI reporting manager 1481 that may be configured for receiving a CSI report configuration, determining an actual number of linear combination coefficients per rank to report, and/or sending a CSI report based on the determined actual number of linear combination coefficients per rank, according to aspects described herein.

The controller/processor 1440 and/or other processors and modules at the BS 110a may perform or direct the execution of processes for the techniques described herein. For example, as shown in FIG. 14, the controller/processor 1440 of the BS 110a has a CSI reporting manager 1441 that may be configured for configuring the UE 120a with a CSI report configuration, determining an actual number of linear combination coefficients per rank the UE 120a report, and/or processing a CSI report from the UE 120a based on the determined actual number of linear combination coefficients per rank the UE 120a reports, according to aspects described herein.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure) , ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information) , accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U. S. C. §112 (f) unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for. ”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component (s) and/or module (s) , including, but not limited to a circuit, an application specific integrated circuit (ASIC) , or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device (PLD) , discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal 120 (see FIG. 1) , a user interface (e.g., keypad, display, mouse, joystick, etc. ) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory) , flash memory, ROM (Read Only Memory) , PROM (Programmable Read-Only Memory) , EPROM (Erasable Programmable Read-Only Memory) , EEPROM (Electrically Erasable Programmable Read-Only Memory) , registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared (IR) , radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk, and

disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media) . In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal) . Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein, for example, instructions for performing the operations described herein and illustrated in FIG. 10 and/or FIG. 11.

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc. ) , such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

A method for wireless communication by a user equipment (UE) , comprising:

receiving a channel state information (CSI) report configuration, configuring the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank;

determining an actual number of linear combination coefficients to report per rank based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank; and

sending a CSI report based on the actual number of linear combination coefficients to report per rank.
The method of claim 1, wherein sending the C SI report based on the actual number of linear combination coefficients to report per rank comprises computing the CSI report based on the determined actual number of linear combination coefficients to report per rank and sending the CSI report with all of the actual number of linear combination coefficients to report per rank.
The method of any of claims 1 or 2, wherein determining the actual number of linear combination coefficients per rank is based on a comparison of the configured number of linear combination coefficients and the computed number of supported linear combination coefficients per rank.
The method of claim 3, wherein determining the actual number of linear combination coefficients per rank comprises at least one of:

for rank 1, determining the actual number of linear combination coefficients to report, per layer, as a smaller of the configured number of linear combination coefficients and a first computed number of supported linear combination coefficients per rank;

for rank 2, determining the actual number of linear combination coefficients to report, per layer, as a smaller of the configured number of linear combination coefficients and one-half a second number of supported linear combination coefficients per rank;

for rank 3, determining the actual number of linear combination coefficients to report across all layers as a smaller of twice the configured number of linear combination coefficients and a computed third number of supported linear combination coefficients per rank; or

for rank 4, determining the actual number of linear combination coefficients to report across all layers as a smaller of twice the configured number of linear combination coefficients and a computed number of supported linear combination coefficients per rank.
The method of any of claims 1 or 2, wherein:

the CSI report is sent in a two-part uplink control information (UCI) ; and

determining the computed number of supported linear combination coefficients per rank is based on a supported payload size for the second part of the UCI and a number of bits for reporting other parameters in the second part UCI.
The method of claim 5, wherein the other parameters in the second part of the UCI comprise at least one of: a number of beams selected for the CSI report; a number of frequency domain basis selected for the frequency domain compression; a number of coefficients selected for the CSI report; a number of strongest coefficient indicators; and a quantization of the linear combination coefficients.
The method of claim 6, further comprising determining the number of strongest coefficient indicators based on the rank and the configured number of linear combination coefficients per rank.
The method of claim 5, wherein the number of supported linear combination coefficients per rank is computed as a quotient of a difference of the supported payload size for the second part of the UCI and the number of bits for reporting the other parameters in the second part UCI and a quantization of the linear combination coefficients.
The method of claim 5, wherein the number of supported linear combination coefficients per rank is computed iteratively.
The method of any of claim 5, wherein:

the UE is configured to report a plurality of CSI reports; and

the method further comprises:

determining a priority order of the plurality of CSI reports; and

determining available payload of the second part of the UCI for lower priority CSI reports as a difference of the supported payload size and a payload size of higher priority CSI reports.
The method of any of claims 1 or 2, further comprising sending an indication to the BS of whether the reported number of linear combination coefficients is smaller than the computed number of linear combination coefficients.
The method of claim 11, wherein the indication is sent via a 1-bit indication in a first part of the UCI or via a CSI report parameter value that is not supported.
The method of claim 11, wherein sending the C SI report comprises sending a channel quality indicator (CQI) report that is not associated with the precoding matrix information when the configured number of linear combination coefficients to report per rank is greater than the maximum supported payload size.
A method for wireless communication by a base station (BS) , comprising:

sending a user equipment (UE) a channel state information (CSI) report configuration, configuring the UE for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank;

determining an actual number of linear combination coefficients per rank the UE reports based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of linear combination coefficients per rank the UE supports for CSI reporting; and

processing a CSI report from the UE based on the determined actual number of linear combination coefficients per rank the UE reports.
The method of claim 14, wherein processing a CSI report based on the actual number of linear combination coefficients to report per rank comprises treating the CSI report as an invalid report when the CSI report comprises a greater number of linear combination coefficients than the determined actual number of linear combination coefficients the UE supports for reporting per rank.
The method of claims 14 or 15, wherein determining the actual number of linear combination coefficients per rank is based on a comparison of the configured number of linear combination coefficients and the computed number of supported linear combination coefficients per rank.
The method of claim 16, wherein determining the actual number of linear combination coefficients per rank comprises at least one of:

for rank 1, determining the actual number of linear combination coefficients to report, per layer, as a smaller of the configured number of linear combination coefficients and a first computed number of supported linear combination coefficients per rank;

for rank 2, determining the actual number of linear combination coefficients to report, per layer, as a smaller of the configured number of linear combination coefficients and one-half a second number of supported linear combination coefficients per rank;

for rank 3, determining the actual number of linear combination coefficients to report across all layers as a smaller of twice the configured number of linear combination coefficients and a computed third number of supported linear combination coefficients per rank; or

for rank 4, determining the actual number of linear combination coefficients to report across all layers as a smaller of twice the configured number of linear combination coefficients and a computed number of supported linear combination coefficients per rank.
The method of any of claims 14 or 15, wherein:

the CSI report is received in a two-part uplink control information (UCI) ; and

determining the computed number of supported linear combination coefficients per rank is based on a supported payload size configured for the second part of the UCI and a number of bits for reporting other configured parameters in the second part UCI.
The method of claim 18, wherein the other parameters in the second part of the UCI comprise at least one of: a number of beams selected for the CSI report; a number of frequency domain basis selected for the frequency domain compression; a number of coefficients selected for the CSI report; a number of strongest coefficient indicators; and a quantization of the linear combination coefficients.
The method of claim 19, further comprising determining the number of strongest coefficient indicators based on the rank and the configured number of linear combination coefficients per rank.
The method of claim 18, wherein the number of supported linear combination coefficients per rank is computed as a quotient of a difference of the supported payload size for the second part of the UCI and the number of bits for reporting the other parameters in the second part UCI and a quantization of the linear combination coefficients.
The method of claim 18, wherein the number of supported linear combination coefficients per rank is computed iteratively.
The method of any of claims 14 or 15, further comprising receiving an indication from the UE of whether the reported number of linear combination coefficients is smaller than the computed number of linear combination coefficients.
The method of claim 23, wherein the indication is received via a 1-bit indication in a first part of the UCI or via a CSI report parameter value that is not supported.
An apparatus for wireless communication, comprising:

means for receiving a channel state information (CSI) report configuration, configuring the apparatus for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank;

means for determining an actual number of linear combination coefficients to report per rank based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank; and

means for sending a CSI report based on the actual number of linear combination coefficients to report per rank.
An apparatus for wireless communication, comprising:

means for sending another apparatus a channel state information (CSI) report configuration, configuring the another apparatus for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank;

means for determining an actual number of linear combination coefficients per rank the another apparatus reports based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of linear combination coefficients per rank the another apparatus supports for CSI reporting; and

means for processing a CSI report from the another apparatus based on the determined actual number of linear combination coefficients per rank the another apparatus reports.
An apparatus for wireless communication, comprising:

a memory;

at least one processor coupled with the memory and configured to:

receive a channel state information (CSI) report configuration, configuring the apparatus for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank;

determine an actual number of linear combination coefficients to report per rank based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank; and

send a CSI report based on the actual number of linear combination coefficients to report per rank.
An apparatus for wireless communication, comprising:

a memory;

at least one processor coupled with the memory and configured to:

send another apparatus a channel state information (CSI) report configuration, configuring the another apparatus for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank;

determine an actual number of linear combination coefficients per rank the another apparatus reports based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of linear combination coefficients per rank the another apparatus supports for CSI reporting; and

process a CSI report from the another apparatus based on the determined actual number of linear combination coefficients per rank the another apparatus reports.
A computer readable medium storing computer executable code thereon, comprising:

code for receiving a channel state information (CSI) report configuration, configuring a user equipment (UE) for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank;

code for determining an actual number of linear combination coefficients to report per rank based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of supported linear combination coefficients per rank; and

code for sending a CSI report based on the actual number of linear combination coefficients to report per rank.
A computer readable medium storing computer executable code thereon, comprising:

code for sending another apparatus a channel state information (CSI) report configuration, configuring a user equipment (UE) for reporting frequency domain compressed precoding matrix information including, for each layer, and for one or more selected beams, a configured number of linear combination coefficients to report per rank;

code for determining an actual number of linear combination coefficients per rank the UE reports based, at least in part, on the configured number of linear combination coefficients to report per rank and a computed number of linear combination coefficients per rank the UE supports for CSI reporting; and

code for processing a CSI report from the UE based on the determined actual number of linear combination coefficients per rank the UE reports.