I have a question related to CSI-RS channel estimation. Let us assume that the base station has 64 antennas and we decide to use 32 antenna ports for CSI-RS transmission. Also, UE has 4 antennas.
My understanding is that UE can estimate 32 x 4 channel, not 64 x 4 channel, and reports a PMI that maps the number of layers to 32 antenna ports for PDSCH transmission.
The question is how to map 32 antenna ports to 64 physical antennas after the PMI precoding.
Does the standard define this mapping?