School of Specs CT1 — the group that writes what your…Overview

What it produces · chapter 3 of 7 · 6 minutes

3 What the group owns, and what it actually works on

The shape of CT1's 229 active documents, and the handful of them that soak up most of the group's work.

3.1 Two hundred and twenty-nine documents

A specification here is one numbered document 3GPP publishes. There are two kinds. A technical specification, a TS, tells you what to build. A technical report, a TR, studies a question and does not oblige anyone to do anything.

The shape of the shelf fits in one grid.

What is counted How many
Specifications listed against CT1 237 [2]
— of those, still active 229 [3]
— of those, no longer active 8 [4]
Active technical specifications 199 [5]
Active technical reports 30 [6]
Active ones in the 24 series 175 [7]
Active ones in the 23 series 16 [8]

The split between the two kinds is lopsided, which is what you would expect of a group whose job is protocol rather than study. 3GPP document numbers begin with a series number, and CT1's are concentrated in one place: 175 of the 229 active documents sit in the 24 series.

The remainder is spread over other series, and the oldest entries still carry two-digit numbers: TS 04.08 and TS 03.68 are both still in the group's list.

3.2 Which edition each one is in

A Release is a numbered edition of the whole 3GPP system. A specification gets a new version for each Release it is carried into, so counting how many documents have a version in a given Release shows where the group's attention has moved.

Release Active CT1 specifications with a version in it
Rel-18 149 [9]
Rel-19 154 [10]
Rel-20 31 [11]

Rel-20 has by far the fewest. The count is of documents that already have a version in a Release; the register carries no publication date, no version date and no version number, so it says nothing at all about what is planned.

3.3 The few that carry the work

A change request, usually written CR, is a proposed edit to a published specification: one document, one problem, one set of replacement paragraphs. Counting change documents per specification is therefore a fair measure of where the effort goes.

Over the whole record, one document stands far above the rest:

Specification Change documents
24.501 15623 [1]
24.301 5422 [12]
24.229 3413 [13]
23.122 2447 [14]
24.379 2364 [15]
24.554 2064 [16]

Read by their titles, the first three are the NAS protocol for the 5G System TS 24.501, the NAS protocol for the Evolved Packet System TS 24.301, and call control built on SIP TS 24.229.

The other three are NAS functions for a device in idle mode TS 23.122, mission critical push-to-talk call control TS 24.379, and proximity services in the 5G System TS 24.554.

3.4 What this year looks like instead

The twelve months to August 2026 tell a different story, and the difference is the interesting part:

Specification Change documents in the year
24.301 499 [17]
24.501 498 [18]
24.369 430 [19]
24.860 165 [20]
24.554 162 [21]
23.122 144 [22]
24.543 143 [23]
24.548 125 [24]

Two of those names do not appear on the all-time list at all. 24.369 is "Ambient IoT Non-Access-Stratum (AIoT NAS) protocol for 5G System (5GS); Stage 3" TS 24.369, and 24.860 is "Study on NAS protocol for 6G System" TR 24.860.

Both are young documents near the top of a one-year list. Reading only the all-time table would have hidden both of them completely.

3.5 Work items: the other way to slice it

Every document says which piece of work it belongs to. A work item is a named piece of work with a scope, an owner and a deadline, and the name travels on every paper filed under it.

219 named work items received a CT1 document in the last twelve months [25]. The six busiest:

Work item Documents in the year
AmbientIoT-CT 420 [26]
TEI19 200 [27]
5GSAT_Ph3_ARCH 192 [28]
MINT_Ph2 172 [29]
FS_6G_NAS_CT 170 [30]
5G_ProSe_Ph3 142 [31]

Those are the names exactly as the documents spell them. What any of them stands for is not in the register, and this course will not guess: a work-item name is a label, not a sentence.

3.6 Looking one of them up

Every one of the 229 active specifications is in this course's register as its own entry, with the title the catalogue gives it.

That is worth knowing, because a 3GPP title is not a thing to reconstruct from memory. It is long, it carries its own brackets and abbreviations, and it is the only reliable way to be sure two people mean the same document.

Reading the clauses inside one is a narrower business. 157 of the 229 have parsed text available here [32], so a clause can be quoted from those and only those. TS 24.501 is one of them, which is why this course is built around it.

What the register does not carry for any specification is a date. There is no publication date, no version date and no version number — only the number, the title, the type, and which Releases it has a version in. A sentence like "this document was last updated in March" cannot be written from here at all.

The document at the top of both tables is worth opening, and Inside TS 24.501, the document at the centre does that. How a change against it turns into published text is How a change request becomes published text.

Where the numbers in this chapter come from

  1. 15623 CT1 documents change 24.501 (Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3), over the whole record rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.501'; rank 1 of the whole group, read 2026-08-04
  2. 237 specifications listed against CT1 rows in the pygppe specification catalogue, table spec where wg='C1', read 2026-08-04
  3. 229 active CT1 specifications rows in the pygppe specification catalogue, table spec where wg='C1' and active='yes', read 2026-08-04
  4. 8 CT1 specifications no longer active rows in the pygppe specification catalogue, table spec where wg='C1' and active<>'yes', read 2026-08-04
  5. 199 active CT1 technical specifications (TS) rows in the pygppe specification catalogue, table spec where wg='C1' and active='yes' and type='TS', read 2026-08-04
  6. 30 active CT1 technical reports (TR) rows in the pygppe specification catalogue, table spec where wg='C1' and active='yes' and type='TR', read 2026-08-04
  7. 175 active CT1 specifications in the 24 series rows in the pygppe specification catalogue, table spec where wg='C1' and active='yes' and specnum starts with '24', read 2026-08-04
  8. 16 active CT1 specifications in the 23 series rows in the pygppe specification catalogue, table spec where wg='C1' and active='yes' and specnum starts with '23', read 2026-08-04
  9. 149 active CT1 specifications have a Rel-18 version distinct specnum in the catalogue table spec_version joined to spec where wg='C1', active='yes' and release='Rel-18', read 2026-08-04
  10. 154 active CT1 specifications have a Rel-19 version distinct specnum in the catalogue table spec_version joined to spec where wg='C1', active='yes' and release='Rel-19', read 2026-08-04
  11. 31 active CT1 specifications have a Rel-20 version distinct specnum in the catalogue table spec_version joined to spec where wg='C1', active='yes' and release='Rel-20', read 2026-08-04
  12. 5422 CT1 documents change 24.301 (Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3), over the whole record rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.301'; rank 2 of the whole group, read 2026-08-04
  13. 3413 CT1 documents change 24.229 (IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3), over the whole record rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.229'; rank 3 of the whole group, read 2026-08-04
  14. 2447 CT1 documents change 23.122 (Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode), over the whole record rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='23.122'; rank 4 of the whole group, read 2026-08-04
  15. 2364 CT1 documents change 24.379 (Mission Critical Push To Talk (MCPTT) call control; Protocol specification), over the whole record rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.379'; rank 5 of the whole group, read 2026-08-04
  16. 2064 CT1 documents change 24.554 (Proximity-services (ProSe) in 5G System (5GS) protocol aspects; Stage 3), over the whole record rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.554'; rank 6 of the whole group, read 2026-08-04
  17. 499 CT1 documents change 24.301 (Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3), in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.301' and uploaded >= '2025-08-04'; rank 1 of the whole group, read 2026-08-04
  18. 498 CT1 documents change 24.501 (Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3), in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.501' and uploaded >= '2025-08-04'; rank 2 of the whole group, read 2026-08-04
  19. 430 CT1 documents change 24.369 (Ambient IoT Non-Access-Stratum (AIoT NAS) protocol for 5G System (5GS); Stage 3), in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.369' and uploaded >= '2025-08-04'; rank 3 of the whole group, read 2026-08-04
  20. 165 CT1 documents change 24.860 (Study on NAS protocol for 6G System), in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.860' and uploaded >= '2025-08-04'; rank 4 of the whole group, read 2026-08-04
  21. 162 CT1 documents change 24.554 (Proximity-services (ProSe) in 5G System (5GS) protocol aspects; Stage 3), in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.554' and uploaded >= '2025-08-04'; rank 5 of the whole group, read 2026-08-04
  22. 144 CT1 documents change 23.122 (Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode), in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='23.122' and uploaded >= '2025-08-04'; rank 6 of the whole group, read 2026-08-04
  23. 143 CT1 documents change 24.543 (Data delivery management - Service Enabler Architecture Layer for Verticals (SEAL); Protocol Specification;), in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.543' and uploaded >= '2025-08-04'; rank 7 of the whole group, read 2026-08-04
  24. 125 CT1 documents change 24.548 (Network Resource Management - Service Enabler Architecture Layer for Verticals (SEAL); Protocol specification), in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-' and crspec='24.548' and uploaded >= '2025-08-04'; rank 8 of the whole group, read 2026-08-04
  25. 219 named work items received CT1 documents in the twelve months to 2026-08-04 distinct winame in the pygppe document database, table tdoc where meeting starts with 'C1-' and uploaded >= '2025-08-04', read 2026-08-04
  26. 420 CT1 documents for the work item AmbientIoT-CT in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-', uploaded >= '2025-08-04' and winame='AmbientIoT-CT'; rank 1 of 6, read 2026-08-04
  27. 200 CT1 documents for the work item TEI19 in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-', uploaded >= '2025-08-04' and winame='TEI19'; rank 2 of 6, read 2026-08-04
  28. 192 CT1 documents for the work item 5GSAT_Ph3_ARCH in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-', uploaded >= '2025-08-04' and winame='5GSAT_Ph3_ARCH'; rank 3 of 6, read 2026-08-04
  29. 172 CT1 documents for the work item MINT_Ph2 in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-', uploaded >= '2025-08-04' and winame='MINT_Ph2'; rank 4 of 6, read 2026-08-04
  30. 170 CT1 documents for the work item FS_6G_NAS_CT in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-', uploaded >= '2025-08-04' and winame='FS_6G_NAS_CT'; rank 5 of 6, read 2026-08-04
  31. 142 CT1 documents for the work item 5G_ProSe_Ph3 in the twelve months to 2026-08-04 rows in the pygppe document database, table tdoc where meeting starts with 'C1-', uploaded >= '2025-08-04' and winame='5G_ProSe_Ph3'; rank 6 of 6, read 2026-08-04
  32. 157 of 229 active CT1 specifications have parsed text on this machine folders under /var/www/whatthespec.net/data/friendlyspec/json/<specnum without dots> that match an active CT1 specification, counted 2026-08-04

Every source this course is built on

Check yourself

Answers appear when you pick one, with where they come from.

Q3.1 How many CT1 specifications are active?

Q3.2 Of the active documents, how many are technical reports rather than technical specifications?

Q3.3 Which document has the most change documents against it in the twelve months to August 2026?

Q3.4 How many named work items received a CT1 document in the last twelve months?

Q3.5 What does the register say the work-item name MINT_Ph2 stands for?

This chapter was written against TS 24.501 version 20.0.0, and built from a source register generated 2026-08-04. A newer version of the document may say something else.