Debug real 5G captures,
logs, and configurations.
21 long-form troubleshooting scenarios — dissect PCAPs in an in-browser mini Wireshark, investigate Splunk-style logs, plan configs graded live against 3GPP, and drive a simulated 5G Core from a terminal. Real problems, real tools.Different from the shorter hands-on labs inside course lessons — these are full multi-step engineering cases.
All scenarios
21 scenariosYour First 5G UE Registration
Boot a 5G core from scratch, start a gNB, and register your first UE. Watch the 5G-AKA authentication flow unfold across NRF, AMF, AUSF and UDM.
5G Registration Failure — Metropolitan Region
A UE in a metropolitan deployment region keeps failing 5G registration. Analyze the NGAP/NAS-5GS trace, find the 5GMM reject cause and decide whether the fix lives on the UE or the network.
RACH Failure — Debugging Preamble / Msg1–Msg4
A UE cannot access an airport macro cell. Walk through the 4-step contention-based RACH procedure, find where Msg1/Msg2/Msg3/Msg4 breaks down and decide the correct PRACH preamble format for the cell radius.
VoNR Call Setup — Successful End-to-End
A VoNR call is working perfectly — now understand what is happening under the hood. Trace the SIP/SDP offer-answer, the P-CSCF to PCF policy authorization, the NGAP PDUSessionResourceModify that creates a dedicated 5QI=1 QoS flow, and the RTP media that finally flows on it.
5G PDU Session Establishment — Find the QoS Flow Setup Failure
An industrial-automation UE authenticates fine but cannot open a data session. Trace the SBI + N4/PFCP signalling between AMF, SMF, UDM and UPF to find whether the fault is a policy misconfiguration or a UPF capability mismatch.
SUCI / SUPI Privacy — Tracing Subscriber Privacy in 5G
A researcher claims 5G finally closes the IMSI-catcher loophole. Walk through a successful registration and verify it for yourself: the UE sends SUCI (not IMSI) on the air, UDM/SIDF decrypts it inside the core, and SUPI only ever appears on SBI traffic.
IMS VoNR Registration Failure — Debugging a SIP 401 Loop
A specific device model cannot place VoNR calls. The 5G attach and IMS PDU session come up cleanly, but IMS registration bounces forever with 401 Unauthorized. Walk through the SIP trace between the UE, P-CSCF, I-CSCF, S-CSCF and HSS, and find the IMS AKA algorithm mismatch (RFC 3310 vs RFC 4169).
NR Dropped Calls — gNB Log Investigation
Cell gNB-MET-042-N1 saw an 18% spike in dropped calls over 2 hours (7% vs 0.4% baseline). Find the pattern in 2h of gNB logs and pin down the root cause.
PCI Planning — Metropolitan Tech Corridor
Plan Physical Cell Identities for a 4-site, 12-cell 5G NR cluster without PSS / DMRS collisions on any neighbour pair.
NSSAI Design — BMW Munich Private 5G
Architect the S-NSSAI allocation for a private 5G network inside a BMW plant. Cover all use cases with correct SST and well-formed SDs.
Establishing a PDU Session
A UE is already registered. Establish a PDU session to DNN=internet, observe UPF selection and the PFCP session created on the UPF, then ping 8.8.8.8 through the data plane.
Trigger an Xn Handover
A UE is on gNB-01 with an active internet session. Simulate the UE drifting into gNB-02 coverage, trigger the Xn handover, and verify the session survives the move.
Network Slicing End-to-End — Trace a Slice Selection
An enterprise UE requests two simultaneous slices (eMBB + URLLC). Trace how NSSF negotiates Allowed NSSAI and how each slice is served by a different SMF and UPF, confirming control- and user-plane isolation.
5G Xn-based Handover — Why Did It Fail?
A premium UE on a highway connecting Munich Airport to the city drops every time it crosses between two neighbouring gNBs. Both gNBs are connected to the same AMF and SMF, and Xn is up. Read the Xn-C (SCTP/XnAP) and NGAP trace to find exactly where the handover breaks and why — a slice-aware mobility bug hiding in plain sight.
N2 (Inter-AMF) Handover Failure — What Went Wrong?
A UE crossing a TA boundary between two AMF sets gets stuck mid-handover. Source and target AMFs exchange Namf_Communication on N14, UDM is queried, and something comes back empty. Find the root-cause packet and decide what the NOC has to change.
5G Roaming (Home-Routed) — Tracing SEPP and N32
A roaming subscriber gets intermittent data service. Trace the N32-c and N32-f signalling between V-SEPP and H-SEPP, find the PRINS policy violation and decide on the architectural fix.
Core Overload — AMF During Super Bowl Surge
Super Bowl LX kickoff triggered a mass-reconnect herd at MetLife Stadium. The AMF started rejecting registrations. Find what ACTUALLY overloaded — and why scaling the AMF alone didn't help.
Intermittent Handover Failures — Statistical Analysis
DOWNTOWN-WEST cluster HO success rate slid from 97.5% to 94.1% over a week with no obvious single cause. Dig into 3 days (~800 events) of HO logs and find the hidden pattern.
PRACH Configuration — Rural Macro Cell
Configure PRACH for a 22 km rural macro cell on n78. Pick the right preamble format, config index, NCS, root sequence, and msg1-FDM.
Break the Core: What Happens When the UPF Dies
A UE is live with an active PDU session. Kill the UPF, watch the cascade of failures propagate from N4 heartbeat loss all the way back to the UE, then recover.
Debug a Failed UE Registration
A newly provisioned UE keeps failing to attach while others work fine. Use AUSF and UDM tooling to find the misconfiguration, fix it, and verify registration succeeds.
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