How UE calculate the path loss to initiate the PRACH in 5G NSA?

Question for 5G NSA:
How UE calculate the path loss to initiate the PRACH?
It has to be the difference between SSB RS power and received SSB RSRP.
My question is how UE comes to know about SSB RS power? Where we can find this IE?

I found that info. :slight_smile:
IE is inside the RRC Connection reconfiguration message and it is named ss-PBCH-BlockPower.

But continuing: I’m getting weird RACH failures that I suspect uplink interference.
For example ss-PBCH-BlockPower is 18 dBm, SSB RSRP is like -85 dBm so path loss around 103 dB yet the rach are failing with 10 preamble sent and UE gets at max tx power 20 dBm from the 3rd preamble.
All the rest PRACH sent (7 of them) are at max tx power 20 dBm and all fail.

Try reducing PreambleInitrecvd target power by 3 dB (say from -110dBm to -113dBm).
Second option, boost SSB power by 3 dB.

I have this in the network: PreambleInitrecvd target power = -100 dBm.
Maybe this is the reason of failure. No idea why it is so high.

Yes please change to -105 dBm, as first step.
So UE can transmit more power at first place.
Hopefully this will reduce your RACH failures.

But if RACH fails 3 consecutive times, at received power -100 dBm, -97 dBm and -94 dBm, why do you think it will be a success at -110 dBm?

During this situation if your UE TX power is not enough, then you will get RACH Failures.
So by changing received power, you ask UE to start will little high power.
As a result the chances of RACH success is higher.

I think UE has little chance to pass the rach at -110 dBm if it fails at -100 dBm.Anyway I have to check with other engineers why they keep preamble received target power at -100dBm.
To me also it seems strange because it reduces a lot the footprint of the cell in uplink
Is like shrinking uplink 5G coverage by parameters not by link budget.
This Preamblereceivedtargetpower should be pretty much aligned with noise floor (that is dependant on temperature, Boltzmann constant and bandwidth).
Higher is the frequency higher should be this parameter.