In a LTE MIMO 4x4 cell how does the 2x2 MIMO UEs are distribuited across the 4 antennas?

Hi Experts I have a question:

In a LTE MIMO 4x4 cell how does the 2x2 MIMO UEs are distribuited across the 4 antennas?

UE selects the 2 antennas to use or in RECONFIGURATION MESSAGE networks tells the UE what antennas to use?

Think in 2x2 scenario, 4x4 cell sends 1st stream through 2 antennas and 2nd stream through other 2 antennas.