6G Core Network Architecture

What is 6G Core? (The Simple Version)

The core network is the brain of every mobile network. When you make a call, send a message, or watch a video, the core network is the invisible system that authenticates you, finds the right path for your data, applies your subscription rules, and connects you to the internet or another user. In 5G, this brain was rebuilt from scratch as the 5G Core (5GC), defined in TS 23.501. Now, 3GPP is designing the next brain: the 6G Core (6G CN), studied in TR 23.801.

But here’s what makes this article different: we’re not guessing about 6G. We’re reading the actual 3GPP study — TR 23.801-01 V0.4.0, published February 2026 — the official document where 3GPP SA2 (the system architecture working group) is designing the 6G Core. This document has 24 key issues, 8 work tasks, and dozens of proposed solutions. We’ll decode all of them.

5G Core vs 6G Core: The Big Picture

Before diving into the 24 key issues, let’s understand the fundamental architectural shift. The good news: 6G Core does not throw away 5G Core. TR 23.801 explicitly states:

So 6G Core evolves from 5G Core. But the evolution is profound. Here’s the side-by-side:

Architectural Assumptions (TR 23.801 Section 4.1)

The document establishes 5 foundational assumptions that frame everything:

Architectural Requirements (Section 4.2)

Two mandatory (“shall”) requirements: roaming support and multi-vendor interoperable interfaces. Plus design principles: cloud-native, energy efficient, resilient, and minimal NF interdependencies.

TR 23.801: The Blueprint for 6G Core

TR 23.801 is organized into 8 Work Tasks (WTs), each containing one or more Key Issues (KIs). Think of Work Tasks as departments and Key Issues as the specific problems each department is solving. Here’s the complete map:

The 24 Key Issues at a Glance

Here is every Key Issue from TR 23.801, mapped to its 5G equivalent (where applicable), with what’s new in 6G highlighted. This is the most complete summary available anywhere.

SBA Evolution, Signalling & User Plane

KI#1: Modular Control Signalling

The biggest pain point in 5G: adding a new NAS feature (like a new mobility procedure) often requires changes to multiple NFs. KI#1 studies how to make NAS modular — introduce new functionalities with minimal or no impact to existing ones. Two sub-issues:

• KI#1.1: Can we isolate mobility management, session management, and NAS transport so changing one doesn’t ripple through the rest?
• KI#1.2: Can UEs interact with the core via generic mechanisms (service discovery, authorization) that work for any operator service?

KI#2: SBA Framework Optimization

5G’s SBA works, but at scale it shows strain. KI#2 targets two improvements:

1. Efficient NF discovery & selection — reduce message overhead for finding the right NF
2. Better resiliency & load balancing — handle NF failures more gracefully than 5G

KI#4: User Plane Architecture

The UPF (User Plane Function) carries all your actual data. KI#4 enhances it in three ways:

AI in 6G Core: Agents, Intents & AIaaS

This is the most transformative part of TR 23.801. Two Key Issues define how AI enters the 6G Core:

KI#18: AI for 6G Architecture (The Core Gets Smart)

KI#18 is about putting AI inside the core network to make it self-managing. It introduces the concept of AI agents — autonomous entities that perform tasks on behalf of operators. Nine specific aspects are being studied:

KI#19: 6G Network for AI (The Network Serves AI)

This is the reverse: instead of AI helping the network, the network helps AI applications. Five aspects:

Sensing (ISAC) & Computing Support

KI#20: Integrated Sensing and Communication

This is entirely new — nothing like it exists in 5G. The 6G network will use its radio signals not just for data, but as radar to sense the physical environment. TR 23.801 studies the core network architecture needed to support this:

• Sensing Service authorization & revocation — who is allowed to request sensing data?
• Sensing Entity discovery — which RAN nodes and UEs can perform sensing? In which modes?
• Sensing data collection & transport — how does raw sensing data flow from RAN to core?
• Sensing result exposure — how do applications (AFs, UEs, core NFs) consume sensing results?
• Mobility handling — what happens to sensing when a UE (acting as sensor) moves?
• Non-3GPP sensing data — can camera, lidar, sonar data be fused with radio sensing?

KI#22: 6G Computing Support

In 5G, MEC (Multi-access Edge Computing) is a separate platform bolted onto the core. In 6G, computing is integrated into the architecture. KI#22 studies:

KI#21: Data Framework

With AI, sensing, and computing all generating massive amounts of data, 6G needs a unified data framework. KI#21 covers: data discovery & registration, collection & transfer, labelling, processing (anonymization, analysis), storage, and exposure. All with privacy, consent, and governance baked in.

Network Slicing 2.0 & QoS Framework

KI#3: Enhanced Slicing

Network slicing was 5G’s killer feature. In 6G, KI#3 focuses on simplification and improvement:

• Identify areas where 5G slicing is overcomplicated and simplify
• Improve how application traffic maps to slices and user plane connections
• Incorporate real-world deployment feedback from 5G slicing
• Study interworking impacts of 6G slicing

KI#5: QoS Framework for 6G

The QoS framework gets the most extensive study with 8 solution variants already proposed. Key enhancements:

Migration & Interworking (5G ↔ 6G)

KI#17: The Bridge Between Generations

No operator will switch to 6G overnight. KI#17 ensures a smooth transition:

Voice, Emergency & Essential Services

These “boring” services are actually critical — voice and emergency calls must work perfectly from day one of 6G launch.

KI#12: Vo6G (Voice over 6G)

Voice will use IMS (IP Multimedia Subsystem), just like VoNR in 5G. But there are real challenges:

• How does a 6G UE natively make IMS calls over the new 6G access?
• Voice continuity when you move from 6G coverage to 5G NR coverage (and vice versa)
• Compatibility with existing deployed IMS including legacy Diameter interfaces (Rx, Cx, Sh)
• Migration path: how to transition from VoNR to Vo6G without breaking existing calls

KI#13 & KI#14: Emergency & Location

Emergency calls over 6G must work even if the UE is in limited-service state. Location services are being redesigned — one of the most interesting architectural changes is decoupling the location function from the AMF (KI#14, Solution #14.2), allowing a dedicated 6G-LMF with direct RAN connection. This enables more accurate and faster positioning.

KI#7: Network Exposure & Intents

6G introduces intent-based exposure on the northbound interface. Instead of an application asking for specific QoS parameters, it expresses an intent: “I need low-latency, high-reliability communication for this surgical robot.” The 6G CN interprets and fulfills it. This bridges KI#7 with KI#18 (AI).

Preparing for the 6G Core Era

For Core Network Engineers

6G Core isn’t a distant dream — it’s being designed right now in TR 23.801. The 24 key issues and 8 work tasks we’ve decoded here will become the normative specifications of 3GPP Release 21. Understanding them today puts you years ahead of the curve.