Three-component codebook based CSI reporting

The present invention relates to method performed by a user equipment (UE) for providing channel state information (CSI) feedback in the form of one or more CSI reports in a wireless communication system (A), comprising receiving, from a network node, (gNB), higher layer configuration(s) of one or more downlink reference signals, and one or more CSI report configuration(s) associated with the downlink reference signal configuration(s), and a radio signal via a MIMO channel, the radio signal including the downlink reference signal(s) according to the one or more downlink reference signal configuration(s), estimating, the downlink MIMO channel based on measurements on the received one or more downlink reference signals, the downlink reference signals provided over a configured number of frequency domain resources, time domain resources and one or more ports, determining, for each CSI report configuration, a precoding matrix based on an estimated channel matrix and two codebooks, the two codebooks including a spatial codebook comprising one or more spatial domain (SD) basis components of the precoder, and a delay codebook comprising one or more delay domain (DD) basis components of the precoder, and one or more non-zero combining coefficients for complex combining of the one or more SD and DD basis vectors, and reporting, to the network node, the one or more CSI reports for the one or more CSI report configurations, wherein each CSI report contains the selected precoding matrix in the form of a precoding matrix identifier, PMI, and a rank identifier, RI, indicating the transmission rank for the RI layers of the precoding matrix, and wherein each CSI report comprises two parts: CSI part 1 and CSI part 2, wherein part 1 has a fixed payload size and comprises information indicating the size of the payload of part 2, wherein part 2 comprises at least the amplitude and phase information of the selected non-zero combining coefficients of the CSI report, and wherein a portion, or the entirety, of part 2 is considered for omission from the CSI report.