Inter gNB mobility for NSA failure happening (5G SgNB change failure ratio on source gNB because of procedure failure in LTE eNB)

Hi Experts,
Inter gNB mobility for NSA failure happening, counter pegging “5G SgNB change failure ratio on source gNB because of procedure failure in LTE eNB”.
Any suggestions here?

May be reconf failures bin LTE.

Some useful steps for this. Might be helpful to you.

  • Check Secondary RAT data report endcDataUsageReportEnabled is set to true in eNB/gNB.
  • Check endcAtionA3EvalFail its set to release or ignore or something else. Set to default or baseline value as per vendor specific.
  • Check Cell relations exits towards target gNB from source. Just to cross verify is there any first tier NR NBRs are missing with source sgNB.
  • Check TermpointToeNB & TermpointTogNB are set in MeNB and Enabled. example like MO configured in MeNB for source gNB, target gNB at MeNB for source gNB. This is very crucial if anything missed here. You will get inter PS CC HO failures in SgNB hence failure counter will peg and degradation in HO SR %.
  • Check in any case MeNB is refusing for SGNB CHANGE over x2AP. DT log analysis & RRC connection RECONFIGURATION mesaage for details about target sgNB addition. Whether eNB is acknowledging this or not. Because MeNB is the one which evaluate the target NR cell suggested by source gNB. If any mismatch during this evaluation, than failures may happen so verify the above point and its parameters as well.
  • gNB detected RLF during ongoing SgNB, coverage gaps, High ISD, etc.
  • Check packet forwarding from both source gNB and target gNB and its parameter settings. All OK or not.
  • Finally TDCOverall timer expiry. It should not be set to too low or to high.
    Also Check any outages on nearby NR/LTE sites.
  • Check LTE KPIs and also HW related logs for any intermittent alarms/failures.

Others valuable inputs for this so that anything else can be checked…