5G NR PMI码本设计方案。NR defines two types of CSI that differ in the structure and size of the precoder codebooks, Type I CSI and Type II CSI.
• Type I CSI primarily targets scenarios where a single user is scheduled within
a given time/frequency resource (no MU-MIMO), potentially with
transmission of a relatively large number of layers in parallel (high-order
spatial multiplexing);
• Type II CSI primarily targets MU-MIMO scenarios with multiple devices
being scheduled simultaneously within the same time/frequency resource but
with only a limited number of spatial layers (maximum of two layers) per
scheduled device
