If a UE has multiple antennas, how should we transmit PRACH on multiple antennas?

Specs & Protocol Testing
1

Hello Experts.

For PUSCH and PUCCH typically we apply a precoder.

What should we do for PRACH?
If a UE has multiple antennas, how should we transmit PRACH on multiple antennas?

Does spec tell anything about the precoder to be used on PRACH?
Does it say which antenna to use?

2

But PRACH is in Uplink.

Why are you concerned on which UE antenna should be transmitted?

There are very few UEs that have 2 TX antenna, only those with MIMO 2x2 UL in 5G SA.

3

I am confused: how should I relate PRACH transmission on multiple antenna case?

4

Probably there are UEs with beamforming in uplink especially in mmWave.

Which specs from 3GPP are you referring to?

5

I think it’s just left for UE implementation.
If I am the designer, I would pick the antenna on which lowest path loss is seen to send the RACH.