Is ra-rnti sent with msg1 or msg2?

Hi All,
Is ra-rnti sent with msg1 or msg2?
In my understanding with msg2.
It’s use to find location of preamble.
Is my understanding correct?

The gNB scrambles PDCCH’s CRC with RA-RNTI for transmission of PDSCH that carries RAR (msg2). RA-RNTI can be addressed to multiple UEs.

Yes I read somewhere that UE also transmit ra-rnti in uplink, i.e. msg1 random access request.
Is it correct?

No, I think it’s not correct.
In msg1 only prach prramble is transmitted.

Yes, assume so, but someone even asked in one of interview.

Interviewers many times ask wrong question intentionally. :smiley:

He he… correct. But let me find also source from where I read it.
Interviews has no limit in our telecom, industry it’s like ocean limitless. :slight_smile:

I assume the interviewer merely wanted to check whether the candidate knows that RA-RNTI is sent or not.
Because RA-RNTI is always calculated by both UE n gNB.

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I thought RA-RNTI was derived from gNB after MSG1.
BTW: these technical interviews are funny. the ammount of details in 5GNR is so vast, that’s possible to pass or fail whoever the interviewer wants to.
Of course, unless field of expertise requires a very detailed understanding of specific mechanisms.

Yes, here is the formula from 38.321.

Yup… Location of msg1 to be precise.

True. I observed many interviewer ask objective type questions, which do not like because it is difficult to recall every thing from the theory.
My manager once told me, we should judge the person on how he think about the particular situation, how he uses the fundamentals in solving problems.