Hierarchical channel state information (CSI) feedback with partial reciprocity with user equipment (UE)

A tangible computer readable storage device storing executable instructions that, in response to execution, cause one or more processors of a user equipment (UE) to perform operations, the operations comprising:

• receiving a channel state information reference signal (CSI-RS) within one or more orthogonal frequency division multiplexing (OFDM) symbols;
• sub-dividing a frequency band of a hierarchical precoding level into frequency parts at one or more lower hierarchical levels;
• sub-dividing the frequency parts at the one or more lower hierarchical levels into sub-bands to form sub-trees of a precoding hierarchy, wherein the frequency parts comprise equally divided frequency parts of the frequency band, and the sub-bands comprise a highest-indexed hierarchical precoding level for a hierarchical precoding scheme;
• and
• generating a channel state information (CSI) feedback based on the hierarchical precoding scheme that selectively reduces a feedback overhead associated with the CSI feedback.

A baseband processor, comprising:

• a memory;
• a processor configured to:
• receive a channel state information reference signal (CSI-RS) within one or more orthogonal frequency division multiplexing (OFDM) symbols;
• determine frequency parts of a frequency band and sub-bands from the frequency parts to be configured at different hierarchical levels in a hierarchical precoding scheme that selectively reduces a feedback overhead associated with channel state information (CSI) feedback;
• prune sub-trees of a precoding hierarchy formed from the sub-bands based on a difference in precoders between the frequency parts or the sub-bands;
• generate a precoder codebook with precoders for the CSI feedback comprising progressively coarser resolutions for rotation angles at lower-indexed hierarchical precoding levels than higher-indexed hierarchical precoding levels that comprise frequency parts, or sub-bands of a frequency band for the hierarchical precoding scheme;
• and
• generate the CSI feedback based on the precoding hierarchy of the hierarchical precoding scheme.