9 CT1, CT3, CT4 and CT6 — one work item description, four groups

9.1 What stage 3 is, and why it comes last

Stage 2 draws the boxes. Stage 3 writes the messages: the fields, the encodings, the error cases, the exact interface each network function offers. It is the part a product is actually built from.

The CT groups do stage 3, and they cannot start until the architecture has settled. Their own work item description says so in one sentence:

The rest of that same objective adds the ordering rule: stage 3 work shall be started only after the applicable normative stage 2 work is available ^[1].

The objective also names two shapes the interface may take — direct between the AIOTF and the radio network, or indirect through the AMF. AIOTF is the Ambient IoT function, which the title of its own service specification spells out TS 29.569.

9.2 One description, four work items

All the CT work runs under a single work item description, CP-252196, approved at plenary CP-109 and sourced from CT1 CP-252196.

Under it sit four rows in the work plan, all carrying the short name AmbientIoT-CT: an umbrella row AmbientIoT-CT, and one part each for CT1 AmbientIoT-CT, CT3 AmbientIoT-CT and CT4 AmbientIoT-CT. All four stand complete as of 2025-09-09.

9.3 What each CT group owns

CT1 — mobility, call control, session management. 508 documents across 8 meetings, 24 letters sent, first document 2025-04-24 CT1. It owns:

• TS 24.369 TS 24.369 — the signalling a device exchanges with the network. New for this work.
• TS 24.007 TS 24.007 — general rules for signalling messages. 10 change requests.
• TS 24.501 TS 24.501 — the ordinary 5G signalling protocol, with a single Ambient IoT change request so far.

CT3 — interworking with external networks. 172 documents, 8 meetings, no letters sent CT3. It owns:

• TS 29.569 TS 29.569 — the services the Ambient IoT function offers. New. 102 documents, 47 change requests.
• TS 29.522 TS 29.522 — the interfaces the core network exposes outwards. 70 change requests.

CT4 — core network protocols. 387 documents, 12 meetings, 25 letters, and nine affected specifications — more than any other group in the area CT4:

Spec	What it is for	Ambient IoT CRs
TS 29.369 TS 29.369	the Ambient IoT data management service. New	94
TS 29.518 TS 29.518	access and mobility management services	55
TS 23.003 TS 23.003	numbering, addressing and identification	46
TS 29.510 TS 29.510	the register of network functions	40
TS 29.504 TS 29.504	the shared data store's own services	26
TS 29.506 TS 29.506	using that store for Ambient IoT data. New	25
TS 29.571 TS 29.571	the data types every core service shares	24
TS 29.505 TS 29.505	using that store for subscription data	3
TS 29.503 TS 29.503	unified data management services	0

CT6 — smart card application aspects. Leads the CT6 part of the phase 2 protocol work and has filed nothing at all: no documents, no meetings, no owned specification in this area CT6 AmbientIoT_Ph2-CT.

TSG CT, the plenary above all three, filed 31 documents across 5 meetings CT.

9.4 The specification that appeared out of nothing

TS 24.369 is the clearest illustration in the area of how fast stage 3 moves once it is allowed to start.

CT1 filed its first Ambient IoT document on 2025-04-24 CT1. The specification now carries 439 documents and 144 change requests TS 24.369. Its catalogue title spells out what it is: the Ambient IoT Non-Access-Stratum protocol for the 5G system, stage 3.

Two more specifications in the area were created new by the CT groups: TS 29.569 for the Ambient IoT function's own services TS 29.569 and TS 29.369 for the data management services TS 29.369, with TS 29.506 covering how that data is held in the shared store TS 29.506.

9.5 Why the change lands in so many core documents

Nine specifications for CT4 alone looks like a lot for one feature. It is what happens when a new kind of thing has to be named, stored, found and reported in a system where every one of those jobs already has its own document.

Follow one device through the core and the list explains itself:

• W1. It needs an identity, so TS 23.003, numbering and addressing, moves TS 23.003.

• W2. Its data has to be stored, so the shared data store's own services move — TS 29.504, and TS 29.506 for Ambient IoT data specifically TS 29.504 TS 29.506.

• W3. The function serving it has to be findable, so the register of network functions moves: TS 29.510 TS 29.510.

• W4. The types carrying all of it have to exist, so the shared data types move: TS 29.571 TS 29.571.

• W5. And it has to be reachable, so access and mobility management services move: TS 29.518 TS 29.518.

None of those is a large change on its own. Together they are why stage 3 work cannot start until stage 2 has settled: every one of them depends on a decision made in TS 23.369 ^[1] TS 23.369.

9.6 Phase two

The CT phase 2 work opened as CP-261030 at plenary CP-112, sourced from CT1 CP-261030.

It repeats the shape of phase 1 — an umbrella AmbientIoT_Ph2, a second umbrella row AmbientIoT_Ph2-CT, and parts for CT1 AmbientIoT_Ph2-CT, CT3 AmbientIoT_Ph2-CT, CT4 AmbientIoT_Ph2-CT and CT6 AmbientIoT_Ph2-CT.

Separately, CT3 leads AmbientIoT_Ph2_APP-CT, unique id 1120029, the protocol side of the application enablement work, opened as CP-261295 at plenary CP-112 AmbientIoT_Ph2_APP-CT CP-261295.

That item declares TS 29.568 impacted. The specification catalogue on this machine holds no title, no owning group and no status for that number, so this course says nothing about what it is for 29.568.

All of the phase 2 CT rows are running rather than finished. What their recorded percentages mean is Where the work stands, and what a percentage is worth.

9.7 Where to read on

The three documents that carry the protocol, and this school holds the text of none of them:

• TS 24.369 TS 24.369 — what a device and the network say to each other. The one to read if you are building either end.

• TS 29.569 TS 29.569 — what the Ambient IoT function offers to the rest of the core.

• TS 29.369 TS 29.369 — how device data is stored and served.

The stage 2 they implement is SA2 and the specification that did not exist. The management and charging that sit beside them are SA5 and SA6 — running it, billing it, and building on top of it.