5G • RAN
RA-RNTI
Random Access RNTI
RNTI calculated from the time-frequency occasion of a transmitted PRACH preamble, used to decode Msg2 RAR.
Technical Explanation
The RA-RNTI is calculated deterministically by both the UE and gNodeB: RA-RNTI = 1 + s_id + 14 * t_id + 14 * 80 * f_id + 14 * 80 * 8 * ul_carrier_id. The UE monitors Type1-PDCCH CSS using its calculated RA-RNTI to receive the DCI scheduling Msg2 Random Access Response.
Key Functions
- Calculated deterministically from PRACH symbol, slot, and frequency index
- Scrambles PDCCH DCI scheduling Msg2 Random Access Response (RAR)
- Distinguishes responses to preambles sent on different PRACH occasions
Specifications
3GPP TS 38.321, TS 38.213
Interfaces
Uu
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