5GC Textbook — The World's Highest-Quality Free 5G Core Learning Resource¶

The goal of this site is NOT to summarize the specifications. It is a textbook whose top priority is helping you truly understand the 5G Core Network (5GC), explain it in your own words, and apply it in real-world work.

Why we built this site (Why)¶

The 3GPP specifications (TS 23.501 / TS 23.502 / TS 24.501, etc.) are accurate, but extremely difficult for first-time readers. Terminology appears with no assumed background, and the "why it works this way" is rarely explained.

On the other hand, most introductory articles are easy to read but weakly grounded in the specifications, and using them as-is in practice can lead to misunderstandings.

This site aims to take the best of both.

Clarity … Diagrams, tables, analogies, and short paragraphs. Readable even for beginners.
Accuracy … Based on public specifications from 3GPP/RFC/ETSI/GSMA and more, with references cited down to the TS number + section number. Anything not in the spec is explicitly marked as "implementation-dependent."

Every explanation is structured in the order Why → What → How.

What you'll be able to do after reading (What)¶

What you'll be able to do	Concrete example
Explain the 5GC	Explain the roles of AMF/SMF/UPF/AUSF/UDM and more to others
Read 3GPP specs	Know "where to find what" in TS 23.501/23.502/24.501
Analyze with Wireshark	Read and interpret NGAP/NAS/PFCP/HTTP2 packets
Understand call flows	Follow procedures like Registration and PDU Session Establishment
Troubleshoot failures	Isolate which NF and which message failed
Design systems	Grasp the key points of designing SBA/Slice/QoS from requirements
Understand vendor differences	Distinguish "the spec" from "implementation-dependent" behavior

Who this site is for¶

This site is written for a broad range of readers:

Students … Those about to start learning telecom networks
New hires … Those who just entered the telecom industry
Telecom / network engineers … Those with general networking experience but new to the core
4G EPC veterans … Those who want to bridge EPC knowledge into the 5GC
5GC developers … Those implementing and integrating NFs
Operations/verification staff … Those doing troubleshooting and testing

To keep it readable for beginners, technical terms are always explained on the spot.

How to get started (How)¶

Choose an entry point that matches your level.

For beginners (start from the big picture of 5GC)

We recommend proceeding in order from Level 1 (5GC Overview). Start with Mobile Network Overview (up to LTE), then continue to 5GC Overview and SBA to grasp the whole picture.

For experienced readers (4G EPC veterans / network engineers)

First check where you stand with the Curriculum. If you prefer learning by doing, pick a procedure that interests you from the "Chapter List" below, such as Registration or Handover.

If you just want to look up a specific term

To quickly look up an NF name, Interface name, or Protocol name, see the Dictionary. Individual NF pages like AMF and Interface pages like N2 are also extensive.

Chapter list¶

All chapters from Level 1 (5GC Overview) to Level 5 (Advanced/Latest). Beginners should start from Level 1 in order; experienced readers can start from whichever procedure interests them.

Level 1 — 5GC Overview

Level 2 — Basic Procedures

Level 3 — Mobility & QoS

Level 4 — Service/Device Types

Level 5 — Advanced/Latest

Reference lookup

Full learning roadmap → Curriculum
Quick term lookup → Dictionary (NF/Interface/Protocol and 15 types in total)
Individual NF/Interface pages → AMF / N2, etc.

Now, grasp the big picture with the Curriculum, or start reading from the chapters above.