RACH RA-RNTI calculation

5G NR
,
1

Hi experts

In this picture specifically in the yellow part you will see the equation that the gnb uses to calculate the ra-rnti

RA-RNTI= 1 + s_id + 14 × t_id + 14 × 80 × f_id + 14 × 80 × 8 × ul_carrier_id (I copied it because it’s not clear in yellow)

Screenshot_20211124-111641_Chrome
Screenshot_20211124-111641_Chrome1080×1021 126 KB

My question is how does the gnb now the ul-carrier-id, fid, sid, tid Does ue need to explicitly send it to gnb so that gnb can calculate the ra-rnti?
And one more question, why do we need different RA-RNTI for different ul carriers? It’s the same UE so I’m confused why we would need to differentiate it for different carriers?
Thanks.

1 Like
2

Hello Experts.

How to calculate RNTI?

Is there any specific formula with respect to PRB allocation for DCI?

With respct to symbolID, slotID etc?

3

RA-RNTI only is calculated I think as per 3gpp.

Rest would be assigned network specific, I think.

4

It depends on time domain and freq domain.

As mentioned in spec.