2 Why anyone wanted it

2.1 Why this chapter is short on reasons

3GPP does not write down why a room agreed to something. What it does write down is why a piece of work was proposed, in a section of the work item description called the justification.

That section is the only stated reason this course is allowed to repeat, and it exists for a minority of the work.

The subject carries 155 short names ^[6]. The register quotes an objective or a justification only for the 41 that carry at least 200 documents, and says so plainly in its own list of what it does not hold.

So for most of the work below, a chapter may say what the work plan calls it and not what it promised.

2.2 Coverage where there is none

The Release 17 work item that put the older internet-of-things radio onto satellites states its case in one sentence.

Not faster and not cheaper. Somewhere there is nothing at all, and a tracker on a ship or a freight wagon has to work there anyway.

2.3 What Release 17 assumed, and what Release 18 wanted to loosen

The Release 18 radio work item opens its justification by restating what the release before it had done, and that restatement is a short summary of Release 17 in the proposers' own words.

Four assumptions sit in that one sentence, and each is a limit somebody later wanted to move:

• Transparent payload. The satellite mirrors, the ground thinks — the split What a non-terrestrial network is sets out.

• GSO and NGSO, geosynchronous and non-geosynchronous orbits.

• Power class 3 devices carrying a satellite navigation receiver. The device is an ordinary handset, and it knows where it is.

• Earth-fixed or moving cells. Either the beam is steered to hold a patch of ground, or it sweeps.

2.4 A band somebody else had already set aside

Not every reason is about coverage. The Release 19 Ku band item argues from spectrum allocation, and names no use case at all.

ITU is the International Telecommunication Union, and regions 1, 2 and 3 are how it splits the map for spectrum purposes. The whole argument is that the band is already satellite spectrum in all three, so 3GPP should write it into its own documents to match.

2.5 Power, and a band with no matching pair

The Release 19 item that defines a time-division mode for the narrowband internet-of-things radio gives two reasons at once.

The first is battery life. It proposes using the radio resources in a periodic subset of the uplink and downlink subframes, and says in the same breath that this limits power consumption ^[7].

The second reason is spectrum shape. The same sentence says the feature lets the radio work with an additional non-geosynchronous satellite system — one whose allocation is a single unpaired block rather than a matched pair.

2.6 A voice call through a satellite that stands still

The newest reasons in the record are about speech. The Release 20 study on an ultra low bit rate speech codec points straight back at the requirements side.

A geostationary satellite is 35,786 km up ^[8], and a voice call has to survive the trip there and back.

The study's own objective says it is developing recommendations for a codec whose primary application is voice over that orbit ^[9].

The architecture study of the same phase argues from what has already been studied rather than from a use case.

Its justification says satellite integration has been studied in Release 16, Release 17, Release 18 and Release 19, and that the requirements group was writing new use cases while it was going on ^[10].

2.7 The one place the record says the thing is in service

Justifications are proposals, and a proposal is free to claim. One of them claims something a reader will want to note.

That is the only statement in this subject's quoted text that says anything is deployed. It is the proposers' sentence, written to argue for more work, and nothing else on this machine confirms or contradicts it.

Read the shape of it, though. It opens with history — what was specified, what was optimised, what is claimed to be running — and only its last sentence asks for anything. A justification argues from where the work already stands.

2.8 Where this leads

The reasons above are attached to particular pieces of work, and the next two chapters are about how those pieces are named, split and carried: How the work is cut up, and who carries it for the paperwork, and The radio half, release by release for the radio line release by release.