5G SA

5G SA (5G Standalone) is a 5G deployment in which devices connect to 5G NR radio cells controlled by a 5G Core (5GC), with no dependency on LTE. It is the architecture that unlocks the full 5G feature set — network slicing, Voice over NR (VoNR) and the service-based core — as opposed to 5G NSA, which uses LTE as an anchor.

How 5G SA works

In 3GPP terms, 5G SA is deployment Option 2: NR base stations (gNBs) connect directly to the 5GC. The device registers through the AMF (access and mobility management function) using 5G NAS signaling defined in 3GPP TS 24.501, and data sessions are set up as PDU sessions toward a data network named by a DNN — the 5G counterpart of the APN.

Other key 5GC functions include the SMF (session management), the UPF (user plane) and the UDM (subscriber data). The subscriber’s permanent identity is concealed before it is sent over the air, so the IMSI is not exposed in clear text.

What 5G SA enables

• Network slicing: logical networks with different performance and policies, selected per device or per session.
• VoNR: voice carried over 5G NR through IMS, without moving to LTE. Where VoNR is not offered, SA networks use EPS fallback to hand calls over to VoLTE.
• Newer features: later 3GPP releases build on the 5GC, for example RedCap devices for mid-range IoT.

5G SA vs. 5G NSA

	5G SA	5G NSA
Core network	5G Core	LTE core (EPC)
LTE required	No	Yes, as anchor
Network slicing	Yes	No
Voice	VoNR or EPS fallback	VoLTE on the LTE anchor
Registration signaling	5G NAS	LTE NAS

Roaming on SA needs its own interconnect and testing; the GSMA’s NG.143 covers 5G SA roaming test cases.

Why it matters for testing

A 5G icon does not prove SA: the device may be on NSA, which rules out slicing and VoNR. Testing must confirm the device actually registered on the 5GC and, when it does not, read the 5GMM reject cause — for example #27 “N1 mode not allowed” or #62 “No network slices available” (see attach reject cause). SimCheck.ai can force 5G SA on a test and decode the signaling — see 5G SA testing.