5G SBA - Service-Based Architecture

F_J · July 28, 2025, 10:39am

Some say 5G SBA is too complicated.

But isn’t clinging to old systems even riskier?

Yes, I know 5G SBA sounds complex.
But stagnation will cost you more.

Operators are done with rigid setups.
They want APIs, not middlemen.
They want modules, not monoliths.
They want change, not delay.

That’s where 5G Service-Based Architecture steps in.
It replaces the all-or-nothing model.
With small, nimble pieces that talk to each other.

Each function stands alone.
They speak through APIs.
They work independently.
They update without drama.

It’s not just a fancy structure.
It’s a response to what networks actually face.

Why it’s important:

Services launch faster.
Scaling becomes simple.
Hardware costs shrink.

And here’s the kicker—
5G SBA is cloud-native.

That means speed.
That means automation.
That means fewer breakdowns.

It’s not just about being modern.
It’s about not getting left behind.

5G SBA doesn’t slow you down with complexity.

It frees you from the cost of standing still.

Thanks for reading.

PDF:

5G SBA - Service-Based Architecture (By Furqan Jameel).pdf (4.8 MB)

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Nitin_Gupta1 · March 13, 2026, 11:13am

5G Core Network - Service-Based Architecture (SBA)

Most 5G engineers understand the RAN.

Very few can explain what happens
AFTER the signal reaches the core.

The 5G Core is where the real
intelligence lives.

Here’s the complete breakdown

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FIRST — WHY 5G CORE IS DIFFERENT:

4G Core (EPC):
→ Monolithic architecture
→ Hardware-based NFs
→ Difficult to scale
→ Vendor lock-in

5G Core (5GC):
→ Service-Based Architecture
→ Cloud-native microservices
→ Scale any NF independently
→ RESTful APIs everywhere

One architectural decision
changed everything.

━━━━━━━━━━━━━━━━━━━━━━

THE GOLDEN PRINCIPLE:

Every Network Function (NF)
exposes its services via
ONE common bus:

SBI — Service Based Interface
(RESTful APIs / HTTP/2 / JSON)

Think of it as:
“AWS API Gateway
but for your mobile network”

Any NF can talk to any NF.
No hardcoded connections.
Pure microservices.

━━━━━━━━━━━━━━━━━━━━━━

THE 10 NETWORK FUNCTIONS:

━━━━━━━━━━━━━━━━━━━━━━

AMF — Namf
Access & Mobility Management

The “front door” of 5GC.
Every UE connects through AMF.

Responsibilities:
→ UE registration & authentication
→ Mobility management
→ Connection management
→ NAS signaling termination
→ Slice selection coordination

Interfaces: N1 (UE), N2 (gNodeB)

━━━━━━━━━━━━━━━━━━━━━━

SMF — Nsmf
Session Management Function

The “traffic controller” of 5GC.

Responsibilities:
→ PDU session establishment
→ IP address allocation
→ UPF selection & control
→ QoS policy enforcement
→ Charging triggers

Key interface: N4 to UPF (PFCP)

━━━━━━━━━━━━━━━━━━━━━━

PCF — Npcf
Policy Control Function

The “rule maker” of 5GC.

Responsibilities:
→ QoS policy decisions
→ Charging rules
→ Network slicing policies
→ Service data flow rules

━━━━━━━━━━━━━━━━━━━━━━

UDM — Nudm
Unified Data Management

The “subscriber database” of 5GC.

Responsibilities:
→ Subscriber profile storage
→ Authentication credentials
→ Access authorization
→ Registration management

Works with: UDR (data storage)

━━━━━━━━━━━━━━━━━━━━━━

AUSF — Nausf
Authentication Server Function

The “security guard” of 5GC.

Responsibilities:
→ UE authentication (5G-AKA)
→ EAP-AKA’ procedures
→ Security key generation
→ Authentication confirmation

━━━━━━━━━━━━━━━━━━━━━━

NRF — Nnrf
Network Repository Function

The “yellow pages” of 5GC.

Responsibilities:
→ NF registration & discovery
→ NF profile management
→ Service authorization
→ NF status monitoring

Every NF registers HERE first.

━━━━━━━━━━━━━━━━━━━━━━

NSSF — Nnssf
Network Slice Selection Function

The “slice router” of 5GC.

Responsibilities:
→ Network slice selection
→ S-NSSAI management
→ AMF set selection
→ Slice availability info

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