5G NSA (EN-DC) Issue Solver

A troubleshooting guide for 5G NSA where LTE is the anchor.

By TheCalcTools Updated October 17, 2026 Formula checked and tested

Your numbers

Symptom

Likely causes

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What to check

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KPIs to review

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Pick the symptom you see on the drive test, counters or customer complaint.

The guide lists the most common causes for that symptom in EN-DC networks.

Use the checks and KPIs to confirm the cause, then fix it in the eNB, gNB, core or transport.

EN-DC: the UE connects to an LTE master node (anchor) and adds an NR secondary node (SgNB) in 3GPP TS 37.340 Option 3.

Using the default values shown in the calculator:

Symptom	No 5G icon: the UE stays on LTE and never gets an NR leg (no EN-DC)

Symptom: no 5G icon on a capable device.
Likely causes: UE band combination, EN-DC signalling on the anchor, X2 link, B1 threshold, core restrictions.
Check the UE capability, SIB2 indication, B1 reports and subscription flags.

Result:

Likely causes	UE or SIM not EN-DC capable for this band combination; anchor cell not signalling EN-DC support (upperLayerIndication in SIB2) or EN-DC feature/licence off on the eNB; no X2 link or IP route between eNB and gNB; NR RSRP below the B1/event threshold; core network or HSS not allowing NR as secondary RAT (DCNR/NR restriction); anchor and NR frequency/band not configured as a valid pair.

Is this a vendor-specific manual?

No. It is a general guide based on 3GPP behaviour. Parameter and counter names differ per vendor, so confirm in your vendor documentation.

Why does the LTE anchor matter?

In NSA all signalling and the initial connection go through LTE. If the anchor is weak, the 5G leg cannot be added or kept.

This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.