TS 23.501 · version 20.2.0 · 1180 clauses · Overview · 40 minutes
The 5G system architecture
TS 23.501 says which functions a 5G network is made of, what each one is responsible for, and how they talk to each other. This course is the short reading of it: seven chapters, a morning's work, enough to follow a conversation about the 5G core and know which clause to open afterwards. It takes the mechanisms that come up in every such conversation — registration, sessions, quality of service, slices, roaming — and treats each one whole rather than treating all of them briefly. Every claim links to the clause it came from, so the document itself is always one click away.
This course was written against TS 23.501 version 20.2.0, verified 2026-08-04.
Same subject, different depth: quick start · in depth
The document, all of it
One block per clause of TS 23.501, in the order they appear, sized by how much text the clause holds. Lit blocks are taught in this course.
The chapters
Part 1 The shape of the system
- 1 What this document actually describes Which of the three stages TS 23.501 is, what a 5G system is made of, and the design decisions everything else follows from. 6 min
- 2 Who does what in the core The dozen network functions that come up in every conversation, what each is responsible for, and which ones are not functions at all. 6 min
- 3 How one function calls another What a service-based interface names, why the N-numbers are two different animals, and how a function finds somebody to call. 5 min
Part 2 Serving one device
- 4 Knowing who you are and where you are The names a device is known by, the two state machines that track it, and how a sleeping device is found again. 6 min
- 5 The connection, and what is promised on it What a PDU session is and what it fixes for life, how the packets are forwarded, and how quality is split into flows. 6 min
Part 3 Running it in the real world
- 6 One network behaving like several How a network is cut into named slices, where the rules and the bills come from, and what this document settles about security. 6 min
- 7 Roaming, other accesses, the edge and the outside What changes when the subscriber is abroad, the access is not a 3GPP radio, the old 4G core is still there, or somebody outside wants in. 6 min
What this course is built on
- Chapters
- 7
- Words written for you
- 7,705
- Clauses covered
- 420 of 1180
- Figures from the document
- 164
- Abbreviations
- 221
- Published versions
- 50