Satellites — a base station in orbit · In depth
Every question of this course
All 66 questions on one page, in the order the chapters come. Pick an answer and it tells you at once whether you were right and where the answer lives.
1 What a non-terrestrial network is, in 3GPP's own words
Q1.1 What does TS 38.108 say a Satellite Access Node is?
The definition says it provides user plane and control plane protocol terminations towards the device and is connected by the NG interface to the 5GC, and that it encompasses a payload on board the platform together with satellite-gateway and gNB functions. "Satellite Access Node" as 38.108 defines it
Q1.2 Which hop does 3GPP call the service link?
TR 38.863 defines the service link as the radio link between satellite and UE. The satellite-to-ground-station hop is the feeder link, defined in TS 38.108. "Service link" as 38.863 defines it
Q1.3 What does a transparent payload do to the signal?
That is TR 38.863's definition word for word. Demodulating and decoding is the regenerative payload, defined in TR 38.742. "Transparent payload" as 38.863 defines it
Q1.4 At what height does TS 38.108 put a geostationary orbit?
The definition gives the circular orbit at 35,786 km above the Earth's equator, following the direction of the Earth's rotation, where an object appears motionless to ground observers. "Geostationary Earth Orbit" as 38.108 defines it
Q1.5 In UE-satellite-UE communication, where does the user traffic go?
TR 23.700-19 defines it as communication between devices under the coverage of one or more serving satellites, using satellite access without the user traffic transiting through the ground segment. "UE-Satellite-UE Communication" as 23.700-19 defines it
2 Why anyone wanted it, and who said so
Q2.1 Which industry does the Release 17 internet-of-things justification name first?
The justification says internet-of-things operation is critical in remote areas with low or no cellular connectivity for many different industries, and the first one it lists is transportation and logistics. why LTE_NBIOT_eMTC_NTN was proposed
Q2.2 What reason does the Ku band work item give for bringing that band into 3GPP?
The justification says the Ku band is allocated for primary satellite use for ITU regions 1, 2 and 3, and that the work item therefore introduces it into 3GPP specifications according to the ITU definitions. why NR_NTN_Ku_bands-Core was proposed
Q2.3 What kind of payload does the Release 18 justification say Release 17 had assumed?
It says Release 17 addressed transparent payload based GSO and NGSO network scenarios, with at least power class 3 devices carrying a satellite navigation receiver, in earth-fixed or moving cell configurations. why NR_NTN_enh-Core was proposed
Q2.4 For how many of the 155 short names does the register hold a quoted objective or justification?
The register quotes only the 41 short names that carry at least 200 documents. For the other 114 it holds the work plan row and the counts, and nothing about what the work promised. 155 Satellites work item acronyms
3 How the work is cut up, and who carries it
Q3.1 Why do 155 short names sit on 183 work plan rows?
Radio work is split into parts, and each part is its own row with its own short name ending -Core, -Perf or -UEConTest. So a chapter counting work items has to say whether it means rows or short names. 155 Satellites work item acronyms
Q3.2 Which group carries more documents of this subject than any other?
RAN4 carries 7490 of these documents over 34 of its meetings. RAN2 is next with 6714 and RAN1 after it with 6492. RAN4
Q3.3 Which group has had these documents on the table at more separate meetings than any other?
SA2 is the largest group outside RAN with 3588 documents, and it spreads them over 50 meetings — more separate meetings than any other group here. SA2
Q3.4 Which single meeting handled more of these documents than any other?
RAN4#116 sat in Bengaluru from 25 to 29 August 2025 with 633 people registered, and 555 of these documents were on its table. R4-116 handled 555 Satellites documents, more than any other meeting
Q3.5 Why is satellite navigation work not part of this subject?
The rule that picks the rows removes three families afterwards, and satellite navigation is the largest of them, because positioning work is about reading a satellite rather than connecting through one. 183 Satellites rows in the work plan
4 NR over satellite, release by release
Q4.1 Which short name carries more documents than any other in this whole subject?
The core part of the Release 17 NR work item is the single largest short name in the register at 4346 documents, spread over 140 meetings. 4346 documents carrying the work item NR_NTN_solutions-Core
Q4.2 Which group does the Release 16 solutions study name as its leading group?
Its leadership line reads "Leading working group RAN3; Secondary working group RAN1 and RAN2". The Release 15 study before it was led by RAN1, and the Release 17 work item after it by RAN2. FS_NR_NTN_solutions
Q4.3 What does the Release 17 objective assume about duplexing for the core work?
The objective ends "FDD is assumed for core specification work for NR-NTN" — frequency division, sending and receiving on two frequencies at once. the objective of NR_NTN_solutions-Core
Q4.4 Which orbits does the Release 19 phase 3 objective assume?
The objective names GSO and NGSO, and says NGSO includes Low Earth Orbit and Medium Earth Orbit. Medium earth orbit is not in TS 38.108's own definition of a satellite. the objective of NR_NTN_Ph3-Core
Q4.5 Which two specifications does the work plan list as created by the Release 17 NR work item?
TS 38.108 is the satellite access node's radio requirements and TS 38.181 is its conformance tests. The two TRs are the study reports that came before, and the other two are documents the work item changed rather than created. NR_NTN_solutions
5 The same idea on the older radio, for things that are not phones
Q5.1 What is the whole objective of the Release 17 internet-of-things work item?
The objective is one sentence and a note about when work starts. It specifies support for two existing radios over non-terrestrial networks rather than inventing anything new. the objective of LTE_NBIOT_eMTC_NTN
Q5.2 What does the Release 19 phase 3 objective name as its first aim?
The objective opens with that aim, which means the satellite holds the message and carries it rather than relaying it live, with the base station itself in orbit. the objective of IoT_NTN_Ph3-Core
Q5.3 Why did Release 19 add a time-division mode to this radio?
The justification says using the radio resources in a periodic subset of the subframes limits power consumption, and that the feature extends operation to an additional non-geosynchronous satellite system. why IoT_NTN_TDD-Core was proposed
Q5.4 Why does one piece of this radio work sit in CT and SA rather than in RAN?
IoT_SAT_ARCH_EPS is the architecture support for this radio in the evolved packet system, led by SA2 and worked on by CT1, CT3, CT4 and CT6. Without it the radio would have had nothing to connect to. IoT_SAT_ARCH_EPS
6 Bands, and why RAN4 carries more of this than anybody
Q6.1 Which group carries more documents of this subject than any other?
RAN4 carries 7490 documents over 34 of its meetings. RAN2 is next with 6714 and SA2 leads the groups outside RAN with 3588. RAN4
Q6.2 What does the name of the combined L-band performance row begin with?
The row's own title in the work plan begins with the word STOPPED. It is part of a title somebody typed, not a status field, and the same row still carries a completion value of 1. NR_NTN_combinedLband-Perf
Q6.3 Which core part carries the most documents of any band item here?
411 documents against `NR_NTN_Ku_bands-Core`, well ahead of the L and S band core part at 164. 411 documents carrying the work item NR_NTN_Ku_bands-Core
Q6.4 Why do TS 38.101-5, TS 38.108, TS 38.133, TS 38.181 and TR 38.863 carry such large counts?
Each band item names the same short list of documents in its own change table, so the counts are that repetition rather than one huge argument. TS 38.133
Q6.5 Which band items in this register carry a conformance row of their own?
The three internet-of-things band items each carry a row whose short name ends UEConTest, led by RAN5. The NR band items in this register carry none. IoT_NTN_FDD_LS_band-UEConTest
7 Proving it works — the conformance shelf
Q7.1 Which group owns the rows whose short names end `-UEConTest`?
Every short name ending `-UEConTest` names RAN5, which carries 2455 documents of this subject over 20 of its meetings. RAN5
Q7.2 Which single conformance row carries the most documents?
1008 documents against `NR_NTN_solutions_plus_CT-UEConTest`, over 33 meetings. The Release 18 requirements row for the older radio is next at 553. 1008 documents carrying the work item NR_NTN_solutions_plus_CT-UEConTest
Q7.3 What does TS 38.181 test, and what does TS 38.521-5 test?
TS 38.181 gives the test methods for three kinds of satellite access node. TS 38.521-5 gives the measurement procedures for a device using satellite access. the scope of 38.181
Q7.4 Release 19's NR phase 3 core and performance rows both stand at a completion value of 1. What does that say about its tests?
Each row of the work plan carries its own completion value and its own planned days. The core row says nothing about the conformance row. NR_NTN_Ph3-UEConTest
8 What the system was asked to do
Q8.1 Where do the requirements from every SA1 item in this subject end up?
Five work items name TS 22.261 in their own change table — 5GSAT, 5GSAT_Ph3, 5GSAT_Ph4-REQ, INS_SAT and SCVS — and the document carries 122 documents of this subject, 120 of them change requests. TS 22.261
Q8.2 What does TR 22.865's scope name first?
Its scope opens on enhancements of the 5G system over satellite and names store and forward operation for delay-tolerant communication first. the scope of 22.865
Q8.3 What does TR 22.887's scope name first?
The two reports open with the same sentence and then name different first items — phase 3 store and forward, phase 4 multi-orbit access. the scope of 22.887
Q8.4 Which of these is not an SA1 item?
PWS_NTN names CT1 as its lead and changes TS 23.041. The other two are SA1 items against TS 22.261. PWS_NTN
Q8.5 Does the register hold an SA1 requirements item for phase 2?
SA1's line runs phase 1, phase 3, phase 4. The phase 2 study is SA2's, about coverage that comes and goes. SA1
9 The architecture, phase by phase — and backhaul, which runs the other way
Q9.1 Which group has been on more separate meetings of this subject than any other?
SA2 carries 3588 documents over 50 meetings — the largest group outside RAN, and on more separate meetings than any other group here. SA2
Q9.2 What does TR 23.700-29 name as the first thing it studies?
Its scope opens on aspects of integrating a satellite component in Release 19 and names the regenerative payload generic architecture first. the scope of 23.700-29
Q9.3 What is satellite backhaul?
The satellite carries the link behind the mast. Its study is TR 23.700-27 and its work item is 5GSATB, and both are SA2's. 5GSATB
Q9.4 What is phase 4's first work task, in the words of its own study item?
WT-1 of FS_5GSAT_Ph4_ARC is an IMS voice call over GEO via NB-IoT NTN connecting to EPC, and TR 23.700-19's scope opens on the same thing. the objective of FS_5GSAT_Ph4_ARC
Q9.5 What does TR 23.700-19 mean by a serving satellite?
The definition builds the limit into itself, and that limit is where most of the hard problems in this half of the subject come from. "Serving satellite" as 23.700-19 defines it
10 What the phone says to the network
Q10.1 What was CT1's own study phase of phase 1 about?
The objective says the study phase, CT1 only, was to study issues and propose solutions for PLMN selection for satellite access as mandated by SA1's requirements. Its report is TR 24.821. the objective of 5GSAT_ARCH-CT
Q10.2 How many documents does the phase 3 CT work item list as ones it will change?
The phase 3 CT item names 19 documents in its own change table, from the device's own protocol down to the interfaces between core network functions. 5GSAT_Ph3_ARCH
Q10.3 Which two documents carry what a device says to the network, and how big are they here?
TS 24.301 is the older core's version and TS 24.501 the 5G one. Nearly every document against either is a change request. TS 24.301
Q10.4 What state is the phase 4 CT work in?
The phase 4 CT item was created on 2026-06-03 and its describing document, CP-261281, was uploaded on 2026-06-10 for meeting CP-112. 5GSAT_Ph4-CT
11 Security, the bills, the management, the layer above and the voice
Q11.1 What does TR 33.700-30's scope say it studies?
Its scope is unusually specific — signalling with multiple satellites without a fresh authentication or key negotiation, in a split architecture, for store-and-forward operation. the scope of 33.700-30
Q11.2 Which specification did the Release 19 security work item name as the one it changes?
The work item's own table names TS 33.401, the security architecture of the older packet core, and nothing else. TR 33.700-29 is the study report that came before it. 5GSAT_Ph3_SEC
Q11.3 SA5 does two of these five jobs. Which two?
The same group runs the charging line — TR 28.844, TR 28.846, TR 28.894 — and the management line — TR 28.808, TR 28.841, TR 28.874. SA5
Q11.4 Why does SA4 appear in this subject at all, and only in Release 20?
The study FS_ULBC carries 325 documents and is aimed at TR 26.940. Its justification points at SA1's phase 4 use case and the requirements about to be written into TS 22.261. FS_ULBC
Q11.5 What does a completion value of 1 on a work plan row tell you?
The work plan carries planned days and a completion value and no status field at all. Whether the work is running, stopped or finished is not recorded here. 116 of the acronyms carry a completion value of 1
12 The specifications this work created, and the ones it changes
Q12.1 How many specifications does this register hold, and out of how many active 3GPP specifications?
102 specifications are in the register, against 3599 active 3GPP specifications altogether. A further 149 are named by too few documents to keep. 102 specifications this work touches
Q12.2 Which document has more satellite documents against it than any other in this register?
1426 documents, 1306 of them change requests. It is a document that existed long before satellites and took the heaviest editing of any of them. TS 38.133
Q12.3 What is TS 38.108 for?
Its scope sets the minimum radio characteristics and minimum performance requirements of NR and NB-IoT operation in an NTN NR in-band satellite access node. The tests are TS 38.181; the device side is TS 38.101-5. the scope of 38.108
Q12.4 Why can this course never quote TR 38.811 or TR 38.821?
Fourteen of the specifications in this register have no parsed text here, and those two studies — the ones the whole radio line rests on — are among them. TR 38.811
Q12.5 What do the LTE twins of the satellite specifications cover?
TS 36.108 and TS 36.181 for the node and its tests, TS 36.102 and TS 36.521-4 for the device and its tests — the same shape as the NR four, on the radio the sensors and trackers use. TS 36.108
13 What the shape of the paperwork says, and where the work stands
Q13.1 What is the most common kind of document in this record?
12603 discussion papers against 10374 change requests. Most of the paper is argument, not text going into a specification. 12603 Satellites documents of type discussion
Q13.2 A document's outcome word is "agreed". What does that tell you about the work item it belongs to?
4298 documents are marked agreed and 7768 noted. Those words are each document's own fate at one meeting. No store here carries a status word for a work item. 4298 Satellites documents whose outcome word is agreed
Q13.3 Why is the earliest upload stamp not the start of this work?
Old papers were put on the server again in one go, so the upload column is a floor for the store rather than a start date for the subject. The meeting code is what dates the older work. the earliest of these documents went up on 2017-05-27
Q13.4 What does the work plan carry instead of a status word?
There is no field that says running, stopped or finished. 116 of the 155 short names carry a completion value of 1, which says the plan for that row is complete and nothing more. 116 of the acronyms carry a completion value of 1
Q13.5 Where does Release 19's radio phase 3 stand, in the work plan's own numbers?
The rules were written and the tests were not. That split between a feature and its conformance part is the commonest shape in this whole work plan. NR_NTN_Ph3-UEConTest
14 Reading the record yourself, and what it cannot tell you
Q14.1 Why is every document count in this course a floor rather than a total?
Everything here was selected by short name, never by searching for the word. Every document filed before a short name existed is outside every number in this course. 6568 documents name satellites or NTN in their title and carry no work item
Q14.2 What does this record say about why a group chose one approach over another?
No store behind this course records why a room settled on anything, so no sentence in it may say a group chose one thing because of another. 7768 Satellites documents whose outcome word is noted
Q14.3 A group entry lists a work item under `named_in_leadership`. What does that mean?
The leadership line is free text and names leading and secondary groups together. Which group leads is in the words of that line and nowhere else. NR_NTN_Ph3-Core
Q14.4 Why can this course never quote TR 38.811 or TR 38.821?
Fourteen of the specifications in this register have no parsed text here. Those two studies are among them, so they can be named and counted and never quoted. TR 38.821
Q14.5 What is the difference between 155 and 183 in this course?
A feature, its core part, its performance part and its conformance part are separate rows carrying the same or related names. Any count of "work items" has to say which of the two it means. 183 Satellites rows in the work plan