Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may transmit a first part of a channel state information (CSI) report, wherein the first part includes an indication of whether a value of a second part of the CSI report matches a value of a previous CSI report; and selectively transmit the second part of the CSI report based at least in part on whether the indication indicates that the value of the second part of the CSI report matches the value of the previous CSI report. In some aspects, a UE may determine a modified subband size of the UE, wherein the modified subband size is different than a configured subband size of the UE; and transmit, in a CSI report, an indication regarding the modified subband size to a base station. Numerous other aspects are provided.

Apparatus and methods are provided to for a user equipment (UE) to report channel state information (CSI) to a base station. The UE sends UE capability signaling to a base station to indicate support of a codebook for high speed scenarios. The UE processes configuration information from the base station for CSI reporting using the codebook. The configuration information indicates measurement resources for one or more downlink (DL) channel. The UE measures a channel response and interference using the measurement resources, generates CSI feedback using the codebook for at least one ray from the base station to the UE, and reports the CSI feedback to the base station.

Embodiments of this application disclose methods and apparatuses for obtaining channel parameters. In an implementation, a method includes, sending, by a network device, a precoded reference signal and indication information indicating K selected frequency domain bases, wherein the precoded reference signal is generated on P ports by mapping K virtual ports associated with the K selected frequency domain bases to each of the P ports through beamforming, wherein K is an integer greater than 1, and wherein the P ports are precoded channel state information reference signal (CSI-RS) ports of the network device and user equipment, and receiving, by the network device, a linear superposition coefficient sent by the user equipment, wherein the linear superposition coefficient corresponds to M frequency domain bases in the K selected frequency domain bases and T ports in the P ports, wherein 1≤T≤P, and 1≤M≤K.

The disclosure provides a method of providing implicit channel state information (CSI) feedback from a user equipment (UE). The method includes determining a precoding matrix indicator (PMI) selection decision metric, selecting one of a sub-band (SB) linear combination coefficient (LCC) selection method, a wideband (WB) LCC selection method, or a sub-band group (SBG) LCC selection method, based on the determined PMI selection decision metric, determining, using the selected LCC selection method, PMI indices based on sub-bands configured by a base station, and transmitting the determined PMI indices to the base station.

Apparatuses and methods for channel state information (CSI) codebook. A method for operating a user equipment (UE) includes receiving a configuration about a CSI report. The configuration includes information about N>1 groups of CSI reference signal (CSI-RS) ports and a codebook. The codebook includes a spatial-domain (SD) basis component, a frequency-domain (FD) basis component, and a coefficient component. The SD basis component includes L.sub.r basis vectors for each group r=1, . . . , N. The FD basis component includes M.sub.v basis vectors. The coefficient component includes coefficients associated with (SD, FD) basis vector pairs. The method further includes, based on the configuration, measuring the N groups of CSI-RS ports and determining the SD basis component, the FD basis component, and the coefficient component such that K.sub.1 coefficients are non-zero and remaining coefficients are zero, where K.sub.1≤Σ.sub.r=1.sup.N(2L.sub.rM.sub.v). The method further includes transmitting the CSI report including an indicator indicating locations of non-zero coefficients.

A method of channel state information (CSI) report can include receiving a CSI report configuration at a user equipment (UE) from a base station, the CSI report configuration being associated with a set of CSI reference signal (CSI-RS) resources corresponding to multiple transmission reception points (TRPs), performing a channel measurement based on the CSI-RSs resources corresponding to the multiple TRPs, determining a precoder matrix indicator (PMI) based on measurement results of the channel measurement, the PMI corresponding to a precoder matrix, denoted W, of a Type II CSI codebook, the precoder matrix having a spatial domain (SD) basis vector matrix, denoted W.sub.1, SD basis selection of the SD basis vector matrix being TRP-specific, and transmitting a CSI report to the base station, the CSI report including the PMI.

Apparatuses and methods for CSI codebook for multi-TRP. a method for operating a user equipment (UE) is provided. The method includes receiving a configuration about a channel state information (CSI) report. The configuration includes information about (i) N>1 groups of CSI reference signal (CSI-RS) ports and (ii) a codebook. The codebook includes a spatial-domain (SD) basis component. The SD basis component includes L.sub.r basis vectors for each group r=1, . . . , N. The method further includes, based on the configuration, measuring the N groups of CSI-RS ports and identifying, based on the measurement, the SD basis component. The method further includes transmitting the CSI report. The L.sub.r values for r=1, . . . , N are indicated by a joint indicator. The joint indicator is a function of the L.sub.r values.

Certain aspects of the present disclosure provide techniques for using subband precoding for uplink transmissions. In some cases, a UE may transmit sounding reference signals (SRS) to a network entity, receive information indicating at least one of a set of one or more frequency domain (FD) bases and linear combination coefficients, determined based on the SRS transmission, determine subband precoding based at least in part on linear combinations of the FD bases based on the linear combination coefficients, and transmit a physical uplink shared channel (PUSCH) with the subband precoding.

Apparatuses and methods for channel state information (CSI) codebook parameters. A method performed by a user equipment (UE) includes receiving information about a channel state information (CSI) report, the information indicating N>1 CSI reference signal (CSI-RS) resources and a codebook. The codebook includes a spatial-domain (SD) basis component, a frequency-domain (FD) basis component, and a coefficient component. The SD basis component includes L.sub.r basis vectors for each CSI-RS resource r=1, . . . , N. The FD basis component includes M.sub.v basis vectors. The coefficient component includes coefficients associated with (SD, FD) basis vector pairs. The information includes codebook parameters. The method further includes, based on the information, measuring the N CSI-RS resources; determining, based on the codebook parameters, the SD basis component, the FD basis component, and the coefficient component; and transmitting the CSI report.

A method of channel state information (CSI) report can include receiving a CSI report configuration at a user equipment (UE) from a base station, the CSI report configuration being associated with a set of CSI reference signal (CSI-RS) resources corresponding to multiple transmission reception points (TRPs), performing a channel measurement based on the CSI-RSs resources corresponding to the multiple TRPs, determining a precoder matrix indicator (PMI) based on measurement results of the channel measurement, the PMI corresponding to a precoder matrix, denoted W, of a Type II CSI codebook, the precoder matrix having a spatial domain (SD) basis vector matrix, denoted W.sub.1, SD basis selection of the SD basis vector matrix being TRP-specific, and transmitting a CSI report to the base station, the CSI report including the PMI.