Questions stringlengths 63 167 | Refference Answers stringlengths 206 451 |
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why PDU session resource setup fails on target gNB during handover? | Check target gNB resources and capabilities. Verify QoS requirements can be met at target. Ensure proper N2 signaling for PDU session resource setup. Examine logs for specific N2 cause value in setup failure. Validate radio resource availability at target cell. |
why VoLTE call setup delay increasing after UE moves from 5G SA coverage to 4G with IMS registration taking >3 seconds? | Check IMS registration procedure optimization for mobility scenarios. Verify P-CSCF discovery procedure during 4G attachment. Analyze DNS resolution performance for IMS services in 4G. Review Diameter signaling load between MME and HSS. Check for IMS restoration procedures triggering unnecessarily. Optimize SIP compres... |
why Users at cell handover boundaries experiencing 2-3x normal latency in 5G SA deployment? | Optimize handover parameters including A3 offset and time-to-trigger; implement make-before-break handover for critical users; adjust measurement reporting configuration; ensure proper neighbor cell configuration and synchronization |
why UE fails IMS registration with SIP 403 Forbidden response after successful 5G SA registration with error logs showing authentication vector mismatch? | Verify HSS/UDM authentication configuration. Check IMS authentication vectors in UDM. Confirm proper synchronization between UDM and IMS. Inspect UE security capabilities reported in registration request. Verify IMS APN settings in UE. Check encryption algorithm compatibility between UE and network. Examine logs for se... |
why UE shows 5G SA connectivity but fails to establish VoNR with SIP 404 Not Found error during IMS registration. Device logs show IMS APN resolution failure? | Check DNS server configuration for IMS APN. Verify DNN/APN configuration in SMF. Examine PDU session parameters for IMS traffic. Verify IMS service status in UDM subscription data. Check UE IMS configuration parameters. Validate SMF session policy for IMS traffic. Verify FQDN resolution path through core network. Inspe... |
why VoNR to VoLTE fallback fails during UE mobility from 5G to 4G coverage area. Call drops instead of continuing as VoLTE. UE supports both VoNR and VoLTE? | Check SRVCC configuration in MME and AMF. Verify inter RAT handover policies. Examine E UTRAN target cell preparation messages. Check IMS continuity support status. Validate UE SRVCC capability. Examine SMF to PGW C signaling during handover. Check for session continuity support in HSS. Review core network timers for h... |
why VoNR emergency calls fail to establish with SIP 503 Service Unavailable. Regular VoNR calls work fine. UE location information is properly included in SIP headers? | Verify emergency call routing configuration in IMS. Check PSAP connectivity status. Examine emergency bearer QoS policy configuration. Verify emergency call prioritization in RAN. Check for capacity issues in emergency call servers. Validate location service functionality. Review emergency APN configuration. Check emer... |
why VoNR calls drop during handover between gNBs with SIP BYE message containing reason header RTP Timeout. Radio measurements show good coverage from both cells? | Check X2/Xn interface configuration between gNBs. Verify QoS flow handover procedures. Examine data forwarding setup during handover. Check handover command timing and execution. Verify UPF path switch timing. Examine handover interruption time measurements. Check gNB release coordination. Verify RTP timeout timer sett... |
why UE fails VoNR but succeeds with VoLTE despite good 5G coverage. UE capability shows support for both services. IMS registration fails only in 5G mode? | Check UE voice domain preference settings. Verify UE radio capability for VoNR. Examine IMS configuration specific to 5G. Check UE firmware/software version compatibility. Verify UE voice client implementation for 5G SA. Examine PDU session parameters for IMS in 5G. Check for mismatches in security algorithms between 4... |
why Unnecessary RRC state transitions between RRC_CONNECTED and RRC_INACTIVE increasing latency for bursty traffic? | Optimize inactivityTimer in RRC; implement RRC state prediction based on traffic patterns; consider keeping critical devices in RRC_CONNECTED state; adjust CDRX instead of state transitions for power saving |
why QoS modification in PDU session fails due to insufficient resources? | Verify available resources in the UPF and gNB. Consider downgrading QoS parameters if maximum resources are reached. Check for congestion in the transport network. Optimize resource allocation policies. Monitor radio resource utilization at serving cells. |
why PDU session modification for handover between access types fails? | Examine N2 interface logs for handover signaling issues. Verify target access network availability and configuration. Check policy rules for access type switching. Ensure UE supports requested access type mobility. Validate session continuity support for the service. |
why GTP-U user plane path failure detected between gNB and UPF? | Verify GTP-U Echo Request/Response configuration. Check physical connectivity and transport network quality. Examine load balancing configuration if multiple paths exist. Verify MTU settings across the path. Implement redundant paths if critical. Ensure ECMP is correctly configured if applicable. |
why UPF receives GTP-U Error Indication from 5G-AN for active PDU session? | Examine Error Indication Report details sent from UPF to SMF. Verify the SMF modifies the PFCP session to buffer downlink packets. Ensure SMF initiates session resource release at the 5G-AN followed by service request procedure to re-establish user plane connection. Check tunnel endpoint identifiers. |
why 5G-AN receives GTP-U Error Indication from UPF for active PDU session? | Verify the 5G-AN initiates PDU Session Resource Notify procedure and releases resources for affected PDU session. Check UE connectivity status to determine if re-establishment is needed. Examine logs for cause of GTP-U context loss at UPF. Validate GTP-U tunnel configuration at both endpoints. |
5G Faults shortlisted and modified questions referred from greenwich157/5G-Faults-Full-v2
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