Coefficient determination for measurement report feedback in multi-layer beamformed communications

A method for wireless communication at a base station, comprising:

• establishing a connection with a user equipment (UE) via a plurality of transmission layers, wherein each transmission layer uses two or more discrete Fourier transform (DFT) beams for communications between the UE and the base station;
• transmitting one or more reference signal transmissions to the UE on the plurality of transmission layers;
• and
• receiving a measurement report from the UE based at least in part on the one or more reference signal transmissions, the measurement report including complex coefficients for linear combinations of the plurality of DFT beams, wherein a first set of the DFT beams each have a complex coefficient of zero and a second set of the DFT beams each have a non-zero complex coefficient, and the measurement report indicates a total number of transmission beams in the second set of DFT beams.

An apparatus for wireless communication at a user equipment (UE), comprising:

• means for performing channel state information (CSI) measurements on one or more reference signal transmissions from a base station;
• means for determining, based at least in part on the CSI measurements, a plurality of complex coefficients for weighting and co-phasing for a linear combination of a plurality of discrete Fourier transform (DFT) beams of a plurality of transmission layers of the base station, wherein a first set of the plurality of DFT beams each have a complex coefficient of zero and a second set of the plurality of DFT beams each have a non-zero complex coefficient;
• means for determining a total number of leading beams jointly across the plurality of transmission layers and corresponding non-zero complex coefficients of the second set of the plurality of DFT beams, wherein the total number of leading beams is equal to a minimum value between the determined total number of DFT beams having non-zero complex coefficient across all the transmission layers and a configured maximum number of leading beams across all the transmission layers;
• means for quantizing the plurality of complex coefficients of the second set of the plurality of DFT beams based at least in part on the total number of leading beams;
• and
• means for transmitting a measurement report to the base station, wherein the measurement report includes at least an indication of the total number of the non-zero complex coefficients and the quantized non-zero complex coefficients for linear combinations of the plurality of DFT beams.

An apparatus for wireless communication at a base station, comprising:

• means for establishing a connection with a user equipment (UE) via a plurality of transmission layers, wherein each transmission layer uses two or more discrete Fourier transform (DFT) beams for communications between the UE and the base station;
• means for transmitting one or more reference signal transmissions to the UE on the plurality of transmission layers;
• and
• means for receiving a measurement report from the UE based at least in part on the one or more reference signal transmissions, the measurement report including complex coefficients for linear combinations of the plurality of DFT beams, wherein a first set of the DFT beams each have a complex coefficient of zero and a second set of the DFT beams each have a non-zero complex coefficient, and the measurement report indicates a total number of transmission beams in the second set of DFT beams.