4 The radio half, release by release

4.1 Two studies before anybody wrote a rule

The radio half is the part of this subject that carries NTN in its short names and sits in the RAN groups. It runs on two radios — the new one, and the older one built for sensors and trackers — and the new one goes first.

It opens in Release 15 with a study, FS_NR_nonterr_nw, on whether the new radio could support non-terrestrial networks at all. RAN1 led it and it produced TR 38.811 FS_NR_nonterr_nw TR 38.811.

It is a small piece of paper by the standards of what followed: 124 documents ^[4]. Its revised study document was approved at RAN#76 in June 2017 RP-171450 RP-76.

Release 16 asked the harder question — not whether, but how.

FS_NR_NTN_solutions was led by RAN3 with RAN1 and RAN2 behind it, produced TR 38.821, and carries 794 documents FS_NR_NTN_solutions TR 38.821 ^[5]. Its study document was approved at RAN#83 RP-190710 RP-83.

4.2 Release 17, where the rules start

NR_NTN_solutions is the work item that turned the studies into specifications, and RAN2 led it, with RAN1, RAN3 and RAN4 behind.

The work plan names two documents it creates: TS 38.108 TS 38.108 for what a satellite base station transmits and receives, and TS 38.181 TS 38.181 for the tests that prove it.

Its own description lists 25 documents it creates or changes, from the physical channels up to the network interfaces, and that list is in its register entry NR_NTN_solutions. Its objective says what it was aiming at:

Low and geostationary orbit are named; high altitude platforms and air-to-ground get compatibility rather than attention; and the core work assumes paired spectrum, one block up and one block down.

The core part of that work item carries 4346 documents ^[6], more than any other short name in this register. Nothing else in the subject comes close.

The other parts of the same work item show the shape How the work is cut up, and who carries it describes. The performance part carries 778 documents ^[7] and the feature row above them both carries 781 ^[8].

The conformance part is a name of its own, NR_NTN_solutions_plus_CT-UEConTest, it sits in RAN5, and it carries 1008 documents ^[9] — more than the feature row above it carries.

4.3 Release 18 and Release 19, two more phases

NR_NTN_enh is the Release 18 item, RAN2 leading again NR_NTN_enh. Its justification restates what Release 17 had assumed, and Why anyone wanted it quotes it in full. Its core part carries 3249 documents ^[10].

NR_NTN_Ph3 is the Release 19 item, RAN2 again NR_NTN_Ph3. Its core part carries 2807 documents ^[11].

Its objective aims at further enhancements for the radio access network side of NTN, assuming geosynchronous and non-geosynchronous orbits, with low and medium earth orbit inside the second ^[12].

Three phases, three descending numbers. What that says about the shape of the work is not something this data settles, and the register records no status word for any work item — only planned days and a completion value.

4.4 Release 20 breaks it into narrow items

There is no single Release 20 successor. The radio work arrives as several items, each with one job.

• Resilience when the satellite navigation receiver goes quiet, NR_NTN_GNSS_resilient NR_NTN_GNSS_resilient. The study before it produced TR 38.742 TR 38.742.

• An extended guard band for both radios NR_NTN_IoT_NTN_ext_guard.

• Higher power classes and a 3 MHz channel for the bands that already exist NTN_bands_Features_R20.

• A second phase of requirements and test methods NR_IoT_NTN_req_Ph2.

The first of those is the one worth reading, because the assumption it removes is one Release 17 had built on: a device with a working satellite navigation receiver, which therefore knows where it is ^[13].

The work item that followed the study was opened at RAN#112 in June 2026 RP-261568 RP-112, and its work plan row stands at a completion value of 0 NR_NTN_GNSS_resilient.

Two further items move a device between the ground network and the satellite one: handover from the older ground radio to the new satellite radio, in Release 20 LTE_TN_NR_NTN_HO, after the Release 19 item that did the idle-mode half of the same problem LTE_TN_NR_NTN_mob.

4.5 The same idea on the older radio

Sensors and trackers do not use the new radio. They use NB-IoT and eMTC — the narrowband and machine-type variants of the older LTE radio — and the satellite work for them is a second line running beside the first.

Release 17 studied it and then specified it. The study was led by RAN1 with RAN2 second, produced TR 36.763, and carries 545 documents FS_LTE_NBIOT_eMTC_NTN TR 36.763 ^[14].

The work item after it carries 689 LTE_NBIOT_eMTC_NTN ^[15], and its objective is one sentence long:

Then a phase per release, the way the new radio has one:

• IoT_NTN_enh in Release 18 IoT_NTN_enh, whose core part carries 1386 documents ^[16].

• IoT_NTN_Ph3 in Release 19 IoT_NTN_Ph3, core part 1427 ^[17].

• IoT_NTN_Ph4 in Release 20 IoT_NTN_Ph4.

Release 19 also added a mode of its own. IoT_NTN_TDD defines a time-division mode of the narrowband radio for an unpaired band — a satellite system with no matched pair of blocks IoT_NTN_TDD.

Its core part carries 354 documents ^[18], and the reason given for it is power, which Why anyone wanted it quotes.

4.6 The one piece that had to leave RAN

A radio on its own reaches nobody. The internet-of-things satellite work needed the older packet core changed to match, and that could not be done in RAN.

IoT_SAT_ARCH_EPS is architecture support for NB-IoT and eMTC non-terrestrial networks in the evolved packet system. Its leadership line names SA2, its documents sit at CT and SA meetings, and it carries 518 of them IoT_SAT_ARCH_EPS ^[19].

It is the seam between the two halves of this subject, and the reason a reader following the radio line will suddenly find themselves reading CT1 papers. How the work is cut up, and who carries it has the group codes and what each one carries.

4.7 What the two lines have in common

Both lines run the same course. A study first, then a work item that writes the rules, then a phase per release, then band items and test items hanging off them. The short names say which radio a piece belongs to — NR_NTN_ for the new one, IoT_NTN_ and LTE_NBIOT_ for the older one.

Both also end at the same shape of shelf: a specification for what the node in orbit transmits, and one for what the device transmits. On the new radio that is TS 38.108 TS 38.108 and TS 38.101-5 TS 38.101-5; on the older one, TS 36.108 TS 36.108 and TS 36.102 TS 36.102.

4.8 Where to read this yourself

Two study reports carry the thinking the whole radio half rests on: TR 38.811 for the first look and TR 38.821 for the solutions TR 38.811 TR 38.821. TR 36.763 does the same job for the internet-of-things radio TR 36.763.

This school holds the text of none of the three. The register names them, counts what was written about them, and stops there — the reports themselves are on 3gpp.org.