Abstract: A communication device for providing a channel state information, CSI, feedback in a wireless communication system includes a transceiver to receive a radio signal including downlink reference signals. The processor estimates an explicit CSI, selects a Doppler-delay precoder matrix for a composite Doppler-delay-beam three-stage precoder, calculates and reports to the transmitter a CSI feedback. The communication device selects from one or more codebooks a subset of D delay components and/or a subset of F Doppler-frequency components and uses the selected subset of delay components for each polarization and each spatial beam and/or the selected subset of Doppler-frequency components for each polarization, each spatial beam and each delay, when calculating the Doppler-delay precoder matrix.

Abstract: A communication device for providing a channel state information, CSI, feedback in a wireless communication system includes a transceiver to receive a radio signal including downlink reference signals. The processor estimates an explicit CSI, selects a Doppler-delay precoder matrix for a composite Doppler-delay-beam three-stage precoder, calculates and reports to the transmitter a CSI feedback. The communication device selects from one or more codebooks a subset of D delay components and/or a subset of F Doppler-frequency components and uses the selected subset of delay components for each polarization and each spatial beam and/or the selected subset of Doppler-frequency components for each polarization, each spatial beam and each delay, when calculating the Doppler-delay precoder matrix.

Abstract: A transmitter includes an antenna array having a plurality of antennas for a wireless communication with one or more receivers, and a precoder connected to the antenna array. The precoder applies a set of beamforming weights to the antenna array. The set of beamforming weights is selected from a codebook to transmit/receive beams or nulls pointing in selected directions. The codebook includes sets of beamforming weights for a plurality of directions. The beamforming weights are based on a first antenna array response matrix defined by a second antenna array response matrix and one or more transformation matrices. The first antenna array response matrix contains first array response vectors of the antenna array, the second antenna array response matrix contains second array response vectors determined using a model of the antenna array. The transformation matrices describe one or more characteristics of the antenna array.