RLF Initiated UE RACH Fail

5G NR
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1

Hi Experts,
I have few cells which have RLF initiated UE RACH Fail in 5G is very high, can someone help to suggest the reasons and possible solutions to reduce that high count.
Thank you
Note: Nokia System

2

Hi @Anuj_Gupta.

Need to check cause for RACH failure.
Is it contention resolution failure or msg3 getting failed due to crc NOK?

Few remedy from network end:

  1. Check for radio conditions, i.e. pathloss should not be high.
  2. Check for PRACH format used.
  3. Distance from ue accessing the cell.
  4. RSI planning to be proper to avoid conflict.
  5. Parameter preamble power rampup, retry for RACH should be inline with golden values.
1 Like
3

Hi @Anuj_Gupta, what’s your B1 threshold?
Check your downtilt for those cells…

4

Hi,
B1 threshold is -108 and RLF is happening with in 500-600- mtrs of NR serving cells, tilts between 2-4* max.

5

Hi Anuj,
if it is in Nokia-Tune below parameter and try, if not then try to find related parameter according to system. It may help you.
*rlcProf4.maxRetxThreshold (Maximum retransmission threshold):
0:t1;
1:t2;
2:t3;
3:t4;
4:t6;
5:t8;
6:t16;
7:t32
*tWaitingRlRecover(Waiting RL Recovery timer)
0:0ms;
1:300ms;
2:400ms;
3:500ms;
4:600ms;
5:700ms;
6:800ms;
7:1000ms;
8:1500ms;
9:2000ms;
10:2500ms;
11:3000ms;
12:4000ms;
13:5000ms;
14:10000ms;
15:20000ms;
16:30000ms;
17:60000ms