A method includes receiving (402) a plurality of reference signals (301-303) at an antenna port of a communication device (101). Each reference signal (301-303) is sent using a corresponding precoder. The precoder is selected from a first set of precoders. The method further includes determining (403) a channel estimate based on the received plurality of reference signals (301-303), and selecting (404) a precoder from a second set of precoders based on the determined channel estimate. The second set of precoders comprises at least one precoder in addition to the precoders of the first set of precoders. The method includes sending (405) an indication (304) relating to the selected precoder.

A communication device for providing a channel state information, CSI, feedback in a wireless communication system includes a transceiver to receive, from a transmitter a radio signal via a time-variant, frequency-selective MIMO channel, the radio signal including downlink reference signals according to a reference signal configuration including a number of antenna ports, and downlink signals including the reference signal configuration; and a processor. The processor estimates an explicit CSI in the frequency domain using measurements on the downlink reference signals on the radio channel, selects a Doppler-delay precoder matrix (W) for a composite Doppler-delay-beam three-stage precoder, calculates either one or more of a channel quality indicator, CQI, and/or a precoder matrix indicator, PMI, and/or a rank indicator, RI, and reports to the transmitter the CSI feedback including either one or more of the CQI, and/or the PMI and/or the RI.

A method by a terminal, a method by a base station, a terminal, and a base station are provided. The method by the terminal includes receiving a first channel state information reference signal (CSI-RS) and a second CSI-RS from a base station; generating channel state information (CSI) based on both the first CSI-RS and the second CSI-RS; and reporting the CSI to the base station, wherein the CSI includes a rank indicator (RI) and a channel quality indicator (CQI).

Techniques for wireless communications are described. A communication device may support processing digital post distortion using additional references symbols. For example, the communication device may precode a signal including at least two reference symbols for a single-layer transmission using at least two antenna ports. At least one reference symbol of the at least two reference symbols is associated with at least one data symbol of a data stream. The communication device may estimate, based on the at least two reference symbols, a nonlinearity model of at least two power amplifiers associated with the single-layer transmission, and determine an estimate of a nonlinearity factor of the precoded signal based on the estimated nonlinearity model. As a result, the communication device may eliminate or reduce the nonlinear factor of the precoded signal based on the estimated nonlinearity model of the at least two power amplifiers and the estimated channel impulse response.

A method for a user equipment (UE) to report channel state information in a wireless communication system is disclosed. The method comprises if a plurality of bandwidth parts (BWPs) is configured for a reporting of the channel state information, constructing the channel state information based on at least one representative channel state information element per each bandwidth part, and reporting the channel state information to a base station, wherein the channel state information includes first channel state information including enhanced wideband per BWP (eWB) commonly related to channel state information of the plurality of bandwidth parts, and second channel state information related to channel state information of each bandwidth part included in the plurality of bandwidth parts.

Apparatuses, methods, and systems are disclosed for precoding wireless communications. An apparatus includes a processor that determines a transform precoder. The processor (805) precodes a plurality of source information symbols over a set of available physical transmission resources using the determined transform precoder. The processor combines the precoded source information symbols using a redundant representation.

Methods, systems, and devices for wireless communications are described. Aspects of the present disclosure describe spatial precoding for inter symbol interference reduction in single carrier. Generally, the described techniques provide for one or more wireless devices (e.g., a user equipment (UE) and a network entity) to determine a weighted sum of several beams, each with a different delay, to form a spatial precoder that increases signal to interference noise ratios while improving signaling quality by diversifying the number of beams carrying subsequent messaging. The one or more wireless devices may determine complex gain values and delay parameters based on reference signals. The one or more wireless devices may utilize the complex gain values and delay parameters such that subsequent transmissions may be received coherently over multiple beams.

A network node signals to a wireless communication device which precoders in a codebook are restricted from being used. The network node in this regard generates codebook subset restriction signaling that, for each of one or more groups of precoders, jointly restricts the precoders in the group by restricting a certain component (e.g., a certain beam precoder) that the precoders in the group have in common. This signaling may be for instance rank-agnostic signaling that jointly restricts the precoders in a group without regard to the precoders transmission rank. Regardless, the network node sends the generated signaling to the wireless communication device.

A base station may transmit to a device an indication of codebook subset restriction (CBSR), which includes at least a restriction on a frequency basis. The device may receive the indication of CBSR, and may transmit to the base station channel state information (CSI) according to the received indication of CBSR. The indication of CBSR may also include a restriction on a spatial basis and restrict the device from reporting the CSI based on a subset of the frequency basis in addition to the spatial basis per configuration of the base station. The indication of CBSR may include a separately configured maximum allowed amplitude of a weighting coefficient for the spatial basis and the frequency basis, where the weighting coefficient is associated with a column vector of a precoding matrix used by the base station and the device. The number of frequency bases and the frequency compression units may be determined based on a number of different criteria, for example the number of antennas, the number of subbands, etc.

An approach is described that includes receiving a CSI report, where the CSI report includes a channel quality indicator (CQI), a rank indicator (RI), and a precoding matrix indicator (PMI). The approach further includes constructing a precoding matrix based on a linear combination of a plurality of mutually orthogonal digital Fourier transformation (DFT) spatial beams, and determining a number of bits for the PMI of the precoding matrix. The approach also includes determining a space frequency matrix based, at least in part, on the number of bits for the PMI and the precoding matrix, and compressing the space frequency matrix. Finally, the approach includes determining a compressed PMI based, at least in part, on the space frequency matrix.