1. NSA (Non-Standalone) Concept
- 5G NSA means 5G is deployed on top of 4G LTE.
- LTE (4G) acts as the anchor for control signaling
.
5G NR (New Radio) is used mainly to boost user data throughput 
.
Advantage: Faster rollout of 5G by reusing existing 4G EPC (Evolved Packet Core).
2. EN-DC (E-UTRA–NR Dual Connectivity) Option 3x
Dual connectivity: A 5G device connects to two base stations simultaneously.
- eNB (LTE base station) = Master Node (MN)
→ Handles control signaling. - gNB (NR base station) = Secondary Node (SN) → Adds extra data capacity.
Option 3x: Both user plane data and control signaling can flow flexibly through the EPC:
User Plane traffic can go directly from gNB → EPC.
This reduces delay and increases efficiency.
3. CUPS (Control and User Plane Separation)
Enhancement to EPC for scalability & flexibility.
Splits Control Plane (C-Plane) from User Plane (U-Plane) 
:
- Control: MME (Mobility Management Entity) manages sessions & mobility.
- User: SGW-U & PGW-U handle data packets.
Benefit: Allows operators to scale user-plane capacity without touching control-plane nodes.
4. Core Network Functions in NSA
- MME → Mobility management & signaling brain
. - SGW → Routes user data (like a highway junction).
- PGW → Connects to external Internet / PDN
. - HSS → Authentication & subscriber info
.
Interfaces:
- S11 (MME ↔ SGW)
- S5/S8 (SGW ↔ PGW)
- SGi (PGW ↔ Internet).
5. Key Benefits
Reuses existing LTE infrastructure → faster rollout.- Higher user throughput by combining LTE + NR.
- Scalable EPC with CUPS.
- Smooth migration path from 4G to 5G standalone (SA).
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