5G SA
Understanding 5G SA
For the first several years of commercial 5G, operators deployed NSA (Non-Standalone) architecture, option 3x. The phone maintained a primary LTE connection for control signaling while adding an NR secondary cell group for user-plane throughput. This approach reused existing EPC infrastructure, accelerating time-to-market. However, NSA fundamentally limited the network: the LTE anchor consumed battery through dual connectivity, the EPC could not support network slicing, and subscriber identity (IMSI) was still transmitted in cleartext.
5G SA removes the entire LTE dependency. The gNB connects to the 5G Core via the NG interface (N2 for control, N3 for user plane). The 5GC itself is built on a Service-Based Architecture where network functions (AMF, SMF, UPF, NSSF, AUSF, UDM) communicate over HTTP/2 APIs. This microservices design enables elastic scaling, edge computing via distributed UPFs, and complete logical isolation through network slicing.
R = Nlayers × Qm × f × Rmax × (NRB × 12 / Ts) × (1 − OH)
Where:
Nlayers = max MIMO layers (up to 8 DL, 4 UL)
Qm = modulation order (8 for 256QAM)
f = scaling factor (1.0 for SA)
Rmax = 948/1024
NRB = resource blocks (273 for 100 MHz at 30 kHz SCS)
OH = overhead (0.14 DL, 0.08 UL)
SA peak DL: ~4.5 Gbps per 100 MHz carrier (single component carrier, 4x4 MIMO, 256QAM)
5G SA vs NSA Architecture Comparison
| Parameter | 5G NSA (Option 3x) | 5G SA | Impact |
|---|---|---|---|
| Core Network | 4G EPC | 5GC (SBA) | Enables slicing, edge compute |
| Control Plane | LTE eNB (anchor) | gNB via N2 to AMF | Eliminates LTE dependency |
| User Plane Latency | 10-30 ms | <1 ms (local UPF) | Enables URLLC applications |
| Network Slicing | Not supported | Full (NSSF, S-NSSAI) | Isolated QoS per service |
| Identity Privacy | IMSI in cleartext | SUPI/SUCI (ECIES) | Prevents IMSI-catcher attacks |
| UE Battery | Dual connectivity drain | Single NR connection | Significant battery savings |
Frequently Asked Questions
What is the difference between 5G SA and 5G NSA?
5G NSA anchors the control plane on a legacy 4G EPC using option 3x dual connectivity, requiring the phone to maintain simultaneous LTE and NR connections. 5G SA connects the gNB directly to a cloud-native 5G Core via the NG interface, eliminating the EPC entirely. This enables network slicing through the NSSF, URLLC with sub-1 ms user-plane latency via local UPF breakout, and SUPI encryption that prevents IMSI-catcher surveillance.
Does 5G SA require a new SIM card?
Yes. 5G SA uses SUPI encryption via the ECIES algorithm. The USIM must store the home network public key to encrypt the SUPI into a SUCI before transmission over the air interface. Legacy 4G SIMs lack this cryptographic capability, so operators issue 5G-compatible USIMs or updated eSIM profiles to subscribers migrating to SA networks.
What is network slicing in 5G SA?
Network slicing creates multiple isolated logical networks on a single physical SA infrastructure. The UE includes an S-NSSAI in its registration request. The NSSF maps this to a dedicated AMF, SMF, and UPF chain. Standard slice types include eMBB (SST=1, up to 20 Gbps), URLLC (SST=2, below 1 ms latency), and mMTC (SST=3, 1 million devices per km squared). Each slice is completely isolated at both transport and core layers.