CSI reporting and codebook structure for Doppler codebook-based precoding in a wireless communications system

A communication device for providing channel state information, CSI, feedback in a wireless communication system is described. The communication device is to receive from a transmitter a radio signal via a time-variant, frequency-selective channel, the radio signal including reference signals according to a reference signal configuration comprising one or more ports, and signals comprising the reference signal configuration. The communication device is to estimate the channel using measurements on the reference signals on the radio channel, the reference signals provided over a configured number of frequency and time domain resources. The communication device is to select a precoder matrix (W), calculate either one or more of a channel quality indicator, CQI, and/or a precoder matrix indicator, PMI, and/or a rank indicator, RI, using the explicit CSI and the precoder matrix (W), and report to the transmitter the CSI feedback including either one or more of the CQI, and/or the PMI and/or the RI, wherein the PMI and RI are used to indicate the precoder matrix for the configured frequency resources, time domain resources and one or more ports. The precoder matrix includes a single codebook comprising one or more Doppler-frequency components of the precoder, or two codebooks, a first codebook and a second codebook, wherein the first codebook comprises one or more Doppler-frequency components of the precoder, and wherein the second codebook comprises one or more delay components of the precoder or one or more spatial beam components of the precoder, or three codebooks, a first codebook, a second codebook and a third codebook, wherein the first codebook comprises one or more Doppler-frequency components of the precoder, wherein the second codebook comprises one or more delay components of the precoder, and wherein the third codebook comprises one or more spatial beam components of the precoder.