Csi reporting and codebook structure for doppler-delay codebook-based precoding in a wireless communications system

A transmitter in a wireless communication system comprising a communication device, the transmitter comprising:

• an antenna array comprising a plurality of antennas for a wireless communication with one or more communication devices for providing a channel state information, CSI, feedback to the transmitter;
• and
• a precoder connected to the antenna array, the precoder to apply a set of beamforming weights to one or more antennas of the antenna array to form, by the antenna array, one or more transmit beams or one or more receive beams,
• a transceiver configured to
• transmit, to the communication device, downlink reference signals according to a CSI-RS configuration comprising a number of CSI-RS antenna ports and indicating a time-domain-repetition of the downlink reference signals, e.g., in terms of a number of consecutive slots the downlink reference signals are repeated in, and downlink signals comprising the CSI-RS configuration;
• and
• receive uplink signals comprising a plurality of CSI reports from the communication device;
• and
• a processor configured to:
• extract at least the precoder matrix identifier and the rank indicator from the plurality of CSI reports;
• and
• construct a precoder matrix applied on the antenna ports using a first component and a second component of the PMI, and determine the beamforming weights responsive to the constructed precoder matrix.

A method for providing a channel state information, CSI, feedback in a wireless communication system, the method comprising:

• receiving, from a transmitter, a radio signal via a MIMO channel, the radio signal comprising downlink reference signals according to a reference signal configuration comprising a number of antenna ports, and downlink signals comprising the reference signal configuration;
• estimating, at the communication device, a CSI using measurements on the downlink reference signals on the radio channel, the downlink reference signals provided over a certain observation time,
• selecting, at the communication device, a Doppler-delay precoder matrix for a composite Doppler-delay-beam three-stage precoder, the Doppler-delay-beam three-stage precoder being based on one or more codebooks, the one or more codebooks comprising
• one or more transmit-side spatial beam components of the composite Doppler-delay-beam three-stage precoder,
• one or more delay components of the composite Doppler-delay-beam three-stage precoder, and
• one or more Doppler-frequency components of the composite Doppler-delay-beam three-stage precoder,
• calculating, at the communication device, one or more of a channel quality indicator, CQI, a precoder matrix indicator, PMI, and a rank indicator, RI, using the explicit CSI and the composite Doppler-delay-beam three-stage precoder with the selected Doppler-delay-beam precoder matrix, and
• reporting from the communication device to the transmitter the CSI feedback comprising one or more of the CQI, the PMI and the RI, wherein the PMI and RI are used to indicate the Doppler-delay-beam three-stage composite precoder matrix for the configured antenna ports,
• wherein the communication device is configured by a base station or another network entity with one or more parameters, the parameter indicating a number of delay components, like delay DFT vectors), and/or a number of Doppler-frequency components, like Doppler DFT vectors), to be used by the communication device when calculating the Doppler-delay precoder matrix, and
• wherein the method further comprises:
• selecting from the one or more codebooks a subset of D delay components and/or a subset of F Doppler-frequency components, and
• using 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.

A method

• performed by a transmitter, or by a base station or by a network node for transmitting and receiving in a wireless communication system, the method comprising:
• transmitting, to a communication device, downlink reference signals according to a CSI-RS configuration comprising a number of CSI-RS antenna ports and indicating a time-domain-repetition of the downlink reference signals and downlink signals comprising the CSI-RS configuration;
• receiving, at the transmitter, uplink signals comprising one or more CSI reports from the communication device, each CSI report indicating D delay components and/or F Doppler-frequency components selected by the communication device from one or more codebooks and used by the communication device when calculating the precoder matrix;
• extracting, at the transmitter, at least the two component precoder matrix identifier and the rank indicator from the plurality of CSI reports;
• constructing, at the transmitter, a precoder matrix applied on the antenna ports using a first component and a second component of the PMI, and
• determining, responsive to the constructed precoder matrix, beamforming weights for a precoder connected to an antenna array of the transmitter.

A non-transitory digital storage medium having a computer program stored thereon to perform the method for providing a channel state information, CSI, feedback in a wireless communication system, the method comprising:

• receiving, from a transmitter, a radio signal via a MIMO channel, the radio signal comprising downlink reference signals according to a reference signal configuration comprising a number of antenna ports, and downlink signals comprising the reference signal configuration;
• estimating, at the communication device, a CSI using measurements on the downlink reference signals on the radio channel, the downlink reference signals provided over a certain observation time,
• selecting, at the communication device, a Doppler-delay precoder matrix for a composite Doppler-delay-beam three-stage precoder, the Doppler-delay-beam three-stage precoder being based on one or more codebooks, the one or more codebooks comprising
• one or more transmit-side spatial beam components of the composite Doppler-delay-beam three-stage precoder,
• one or more delay components of the composite Doppler-delay-beam three-stage precoder, and
• one or more Doppler-frequency components of the composite Doppler-delay-beam three-stage precoder,
• calculating, at the communication device, one or more of a channel quality indicator, CQI, a precoder matrix indicator, PMI, and a rank indicator, RI, using the explicit CSI and the composite Doppler-delay-beam three-stage precoder with the selected Doppler-delay-beam precoder matrix, and
• reporting from the communication device to the transmitter the CSI feedback comprising one or more of the CQI, the PMI and the RI, wherein the PMI and RI are used to indicate the Doppler-delay-beam three-stage composite precoder matrix for the configured antenna ports,
• wherein the communication device is configured by a base station or another network entity with one or more parameters, the parameter indicating a number of delay components, like delay DFT vectors), and/or a number of Doppler-frequency components, like Doppler DFT vectors), to be used by the communication device when calculating the Doppler-delay precoder matrix, and
• wherein the method further comprises:
• selecting from the one or more codebooks a subset of D delay components and/or a subset of F Doppler-frequency components, and
• using 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,
• when said computer program is run by a computer.

A non-transitory digital storage medium having a computer program stored thereon to perform the method performed by a transmitter, or by a base station or by a network node for transmitting and receiving in a wireless communication system, the method comprising:

• transmitting, to a communication device, downlink reference signals according to a CSI-RS configuration comprising a number of CSI-RS antenna ports and indicating a time-domain-repetition of the downlink reference signals and downlink signals comprising the CSI-RS configuration;
• receiving, at the transmitter, uplink signals comprising one or more CSI reports from the communication device, each CSI report indicating D delay components and/or F Doppler-frequency components selected by the communication device from one or more codebooks and used by the communication device when calculating the precoder matrix;
• extracting, at the transmitter, at least the two component precoder matrix identifier and the rank indicator from the plurality of CSI reports;
• constructing, at the transmitter, a precoder matrix applied on the antenna ports using a first component and a second component of the PMI, and
• determining, responsive to the constructed precoder matrix, beamforming weights for a precoder connected to an antenna array of the transmitter,
• when said computer program is run by a computer.