What are the reasons to Random Access Failures in 5G?

Hello Experts.
What are the reasons to Random Access Failures?

UE didn’t get msg2.

Looks like UE did not receive msg2 .
But this is what UE thinks .
But there can also be other issues:

  • gNB might not have received RACH at all from UE - need to check gNB logs for RACH.
  • PDCCH blocking at gNB if Cell is Loaded.
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RACH attempt initiate in low RSRP , MSG1 is not received by gNB, then in the UE MSG2 timer expire. After 10 attempts, RACH procedure is aborted.

check 5G coverage or increase reambleTransMax to 20

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1- gnb may already send Msg2-RAR but UE can not receive it. Pls check coverage.
2- gnv may not send Msg2-RAR to UE. Maybe, lack of sxheduling resource such as CCE, Pdsch. Pls check coreset RB number, CCE ul/dl ratio,…