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Complete 3GPP IE Catalogue
NTN Information Elements & Parameters
Every Information Element a 5G NTN engineer touches — with its ASN.1 definition, type, value range, unit/granularity, semantics and the exact 3GPP clause. Organised from the SIB19 broadcast down through timing advance, ephemeris, MAC control elements, NAS timers, NGAP/F1AP and the NTN RF bands. Values are traced to TS 38.331 v18/v19, TS 38.213, TS 38.321, TS 24.501 and TS 38.101-5.
SIB19 / NTN-ConfigEphemerisInfota-Common + driftK_offset / K_macMAC CENAS 5GMMNGAP · F1APn255 · n256 · Ka
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1SIB19 — the NTN system-information block TS 38.331 §6.3.1
SIB19 is the container the network broadcasts (or delivers on-demand) so a UE can perform NTN-aware access: it carries the serving-satellite ephemeris, the common timing/frequency parameters, service validity, a reference location for location-based reselection and per-neighbour NTN configuration.
SIB19-r17 ::= SEQUENCE { ntn-Config-r17 NTN-Config-r17 OPTIONAL, -- serving-cell NTN params (§2) t-Service-r17 INTEGER (0..549755813887) OPTIONAL, -- when the cell stops serving referenceLocation-r17 ReferenceLocation-r17 OPTIONAL, -- anchor for distance-based reselection distanceThresh-r17 INTEGER (0..65525) OPTIONAL, -- reselection distance threshold ntn-NeighCellConfigList-r17 NTN-NeighCellConfigList-r17 OPTIONAL, -- up to 4 neighbour configs ... }
SIB19 top-level fields
| Field | Type | Range / values | Unit / granularity | Semantics | Spec |
|---|---|---|---|---|---|
| ntn-Config-r17 | NTN-Config-r17 | SEQUENCE | — | Serving-cell NTN parameters: epoch, K-offsets, common TA, polarization, ephemeris (see §2–§4). | §6.3.1 |
| t-Service-r17 | INTEGER | 0 … 549 755 813 887 | 10 ms units (ref 1900-01-01) | Absolute time at which the serving cell/satellite stops providing service — lets the UE plan reselection before loss of coverage. | §6.3.1 |
| referenceLocation-r17 | ReferenceLocation | ellipsoid point | lat/long coded | Geographic anchor used with distanceThresh for location-based measurement / reselection. | §6.3.1 |
| distanceThresh-r17 | INTEGER | 0 … 65 525 | 50 m → max ≈ 3 276 km | Distance from referenceLocation beyond which the UE performs measurements/reselection. | §6.3.1 |
| ntn-NeighCellConfigList-r17 | SEQUENCE (SIZE(1..4)) | ≤ 4 entries | — | Per-neighbour NTN-Config + carrierFreq + physCellId so the UE can pre-compute TA/Doppler for the next satellite. | §6.3.1 |
Why it matters — SIB19 is what makes open-loop NTN access possible: without the ephemeris and common-timing IEs the UE could not pre-compensate the hundreds-of-milliseconds delay and tens-of-kHz Doppler before its first transmission.
2NTN-Config — timing & frequency IEs TS 38.331 §6.3.1 · TS 38.213 §4.2
The heart of the NTN radio configuration. These fields let the UE align its uplink across a footprint hundreds of km wide (ta-Common + drift, cellSpecificKoffset), place MAC-CE actions correctly across the feeder delay (kmac), bound how long its sync stays valid, and set the expected polarization.
NTN-Config-r17 ::= SEQUENCE { epochTime-r17 EpochTime-r17 OPTIONAL, ntn-UlSyncValidityDuration-r17 ENUMERATED {s5,s10,s15,s20,s25,s30,s35,s40, s45,s50,s55,s60,s120,s180,s240,s900} OPTIONAL, cellSpecificKoffset-r17 INTEGER (1..1023) OPTIONAL, -- slots @ ref SCS kmac-r17 INTEGER (1..512) OPTIONAL, ta-Info-r17 TA-Info-r17 OPTIONAL, ntn-PolarizationDL-r17 ENUMERATED {rhcp, lhcp, linear} OPTIONAL, ntn-PolarizationUL-r17 ENUMERATED {rhcp, lhcp, linear} OPTIONAL, ephemerisInfo-r17 EphemerisInfo-r17 OPTIONAL, ta-Report-r17 ENUMERATED {enabled} OPTIONAL, ... } TA-Info-r17 ::= SEQUENCE { ta-Common-r17 INTEGER (0..66485757), -- 4.072 ns units ta-CommonDrift-r17 INTEGER (-257303..257303) OPTIONAL, -- 0.2 ns/s ta-CommonDriftVariant-r17 INTEGER (0..28949) OPTIONAL -- 0.02 ns/s² }
NTN-Config timing / frequency fields
| Field | Type | Range / values | Unit / granularity | Semantics | Spec |
|---|---|---|---|---|---|
| cellSpecificKoffset-r17 | INTEGER | 1 … 1023 | slots @ 15 kHz ref SCS | K_offset — shifts all UL scheduling relationships (RAR→Msg3, grant→PUSCH) so the UL arrives when the gNB expects it despite the RTT. Sized from worst-case cell RTD. | 38.213 §4.2 |
| kmac-r17 | INTEGER | 1 … 512 | slots | K_mac — DL MAC-CE timing offset compensating the feeder-link delay between the network's and UE's DL reference (≈0 on a regenerative on-board gNB). | 38.213 §4.2 |
| ta-Common-r17 | INTEGER | 0 … 66 485 757 | 4.072 ns → max ≈ 270.75 ms | Network-controlled common timing advance (feeder + common path). GEO worst case ≈ 66 485 384 ≈ 270.73 ms — the field maximum. | 38.331 §6.3.1 |
| ta-CommonDrift-r17 | INTEGER | −257 303 … 257 303 | 0.2 ns/s (first-order) | Rate of change of ta-Common — lets the UE extrapolate the common TA between broadcasts as the satellite moves. | 38.331 §6.3.1 |
| ta-CommonDriftVariant-r17 | INTEGER | 0 … 28 949 | 0.02 ns/s² (2nd-order) | Second-order drift (acceleration) of the common TA for higher-accuracy extrapolation over the validity window. | 38.331 §6.3.1 |
| ntn-UlSyncValidityDuration-r17 | ENUMERATED | s5 … s900 | seconds (5…900 s) | How long the UE may keep applying its computed TA/Doppler before it must refresh ephemeris/sync parameters. | 38.331 §6.3.1 |
| ntn-PolarizationDL-r17 / UL-r17 | ENUMERATED | rhcp / lhcp / linear | — | Expected DL/UL polarization so the UE aligns its receiver and beams can reuse frequency across orthogonal polarizations. | 38.331 §6.3.1 |
| ta-Report-r17 | ENUMERATED {enabled} | enabled / absent | — | Enables the TA Report MAC CE so the UE reports its computed TA when drift crosses the configured threshold (see §7). | 38.331 §6.3.1 |
Total UE timing advance —
N_TA,total = N_TA,UE-specific + N_TA,common + N_TA,offset: the UE self-computes the service-link term from GNSS + ephemeris, adds the network's ta-Common (extrapolated by the drift terms), plus the fixed offset. Closed-loop TA MAC-CE then trims the residual.3EphemerisInfo — satellite position/velocity TS 38.331 §6.3.1
A CHOICE of two representations. The state-vector form (ECEF position + velocity) is simple to apply short-term; the orbital-element (Keplerian) form is compact and stays valid longer. Every field is carved to physically meaningful NTN orbits so no bits are wasted on impossible states.
EphemerisInfo-r17 ::= CHOICE { positionVelocity-r17 PositionVelocity-r17, orbital-r17 Orbital-r17 } PositionVelocity-r17 ::= SEQUENCE { -- ECEF state vector positionX-r17 INTEGER (-33554432..33554431), -- 1.3 m → ±43 621 km positionY-r17 INTEGER (-33554432..33554431), positionZ-r17 INTEGER (-33554432..33554431), velocityVX-r17 INTEGER (-131072..131071), -- 0.06 m/s → ±7 864 m/s velocityVY-r17 INTEGER (-131072..131071), velocityVZ-r17 INTEGER (-131072..131071) } Orbital-r17 ::= SEQUENCE { -- Keplerian elements semiMajorAxis-r17 INTEGER (0..8589934591), -- ≈6 500..43 000 km eccentricity-r17 INTEGER (0..1048575), -- near-circular ≤ ~0.015 periapsis-r17 INTEGER (0..268435455), -- arg. of periapsis, 0..360° longitude-r17 INTEGER (0..268435455), -- RAAN, 0..360° inclination-r17 INTEGER (-67108864..67108863), -- ±90° meanAnomaly-r17 INTEGER (0..268435455) -- 0..360° }
State-vector form · PositionVelocity-r17
| Field | Type | Range | Granularity → span | Semantics | Spec |
|---|---|---|---|---|---|
| positionX/Y/Z-r17 | INTEGER | ±33 554 432 (2²⁵) | 1.3 m → ±43 621 km | ECEF satellite position components at epochTime. Span covers LEO through GEO. | §6.3.1 |
| velocityVX/VY/VZ-r17 | INTEGER | ±131 072 (2¹⁷) | 0.06 m/s → ±7 864 m/s | ECEF velocity components. ±7.86 km/s spans LEO orbital speed (~7.5 km/s). | §6.3.1 |
Orbital (Keplerian) form · Orbital-r17
| Field | Type | Range | Effective span | Semantics | Spec |
|---|---|---|---|---|---|
| semiMajorAxis-r17 | INTEGER | 0 … 8 589 934 591 | ≈ 6 500 – 43 000 km (0.5 m step) | Orbit size a; sets the period via T=2π√(a³/µ). Covers LEO→GEO. | §6.3.1 |
| eccentricity-r17 | INTEGER | 0 … 1 048 575 | near-circular, ≤ ~0.015 | Orbit eccentricity e; NTN orbits are near-circular. | §6.3.1 |
| inclination-r17 | INTEGER | ±67 108 863 (2²⁶) | −90° … +90° | Orbital plane inclination i. | §6.3.1 |
| longitude-r17 (Ω) | INTEGER | 0 … 268 435 455 | 0° … 360° | Right ascension of the ascending node (RAAN). | §6.3.1 |
| periapsis-r17 (ω) | INTEGER | 0 … 268 435 455 | 0° … 360° | Argument of periapsis. | §6.3.1 |
| meanAnomaly-r17 (M) | INTEGER | 0 … 268 435 455 | 0° … 360° | Mean anomaly at epochTime — the satellite's phase in its orbit. | §6.3.1 |
4EpochTime & validity timers TS 38.331 §6.3.1
The epoch anchors the ephemeris and common-TA values in time; the UE extrapolates forward from it using the drift terms until the UL-sync validity duration expires and it must refresh.
EpochTime-r17 ::= SEQUENCE { sfn-r17 INTEGER (0..1023), -- system frame number subFrameNR-r17 INTEGER (0..9) -- sub-frame within the SFN }
Epoch & validity fields
| Field | Type | Range | Unit | Semantics | Spec |
|---|---|---|---|---|---|
| sfn-r17 | INTEGER | 0 … 1023 | frame (10 ms) | System-frame number marking the reference instant for ephemeris/ta-Common. | §6.3.1 |
| subFrameNR-r17 | INTEGER | 0 … 9 | sub-frame (1 ms) | Sub-frame within the epoch SFN, giving 1 ms resolution on the reference instant. | §6.3.1 |
| ntn-UlSyncValidityDuration | ENUMERATED | s5 … s900 | 5 … 900 s | Validity window of the applied TA/Doppler; refresh required on expiry (see §2). | §6.3.1 |
Extrapolation — a UE that acquires SIB19 after
epochTime propagates the satellite position with the ephemeris and adjusts ta-Common by ta-CommonDrift·Δt + ½·ta-CommonDriftVariant·Δt², valid up to ntn-UlSyncValidityDuration.5Neighbour config, reference location & reselection TS 38.331 §6.3.1 · TS 38.304
NTN neighbour entries carry per-satellite ephemeris/timing so a handover target can be pre-computed. Location-based reselection uses referenceLocation + distanceThresh so a stationary UE reselects on geography, not on a sweeping beam.
NTN-NeighCellConfig-r17 ::= SEQUENCE { ntn-Config-r17 NTN-Config-r17 OPTIONAL, -- neighbour's ephemeris/timing carrierFreq-r17 ARFCN-ValueNR OPTIONAL, -- neighbour DL frequency physCellId-r17 PhysCellId OPTIONAL -- 0..1007 }
Neighbour & location IEs
| Field | Type | Range / values | Unit | Semantics | Spec |
|---|---|---|---|---|---|
| ntn-Config-r17 (neigh) | NTN-Config-r17 | SEQUENCE | — | Full ephemeris/timing of a neighbour satellite so the UE can pre-compute target TA/Doppler for handover. | §6.3.1 |
| carrierFreq-r17 | ARFCN-ValueNR | 0 … 3 279 165 | NR-ARFCN | Neighbour cell downlink frequency. | 38.331 |
| physCellId-r17 | PhysCellId | 0 … 1007 | PCI | Neighbour physical cell identity. | 38.211 §7.4.2 |
| referenceLocation-r17 | ReferenceLocation | ellipsoid point | WGS-84 lat/long | Anchor point for distance-based measurement/reselection. | §6.3.1 |
| distanceThresh-r17 | INTEGER | 0 … 65 525 | 50 m → ≤ 3 276 km | Distance from the anchor triggering measurement/reselection. | §6.3.1 |
6ServingCellConfigCommon — NTN additions TS 38.331 §6.3.2
The cell-common configuration gains NTN-specific offsets and the reference SCS against which cellSpecificKoffset is interpreted, plus a UE-specific K-offset delta and a browse of extended timing relationships.
Serving-cell NTN parameters
| Field | Type | Range / values | Unit | Semantics | Spec |
|---|---|---|---|---|---|
| ntn-Config-r17 | NTN-Config-r17 | SEQUENCE | — | Cell-common NTN parameters (may also be delivered via SIB19). | §6.3.2 |
| kOffset (reference SCS) | INTEGER | per §2 | slots | The reference sub-carrier spacing that defines the slot unit of cellSpecificKoffset. | 38.213 §4.2 |
| ue-SpecificKoffset (BWP) | INTEGER | 0 … (scaling) | slots | Optional per-BWP K-offset delta refining the cell-common value for a UE's active numerology. | 38.331 §6.3.2 |
| ta-Report (per-cell) | ENUMERATED | enabled / absent | — | Enables UE TA reporting on this serving cell. | §6.3.1/.2 |
Numerology note — because K-offset is counted in slots, its wall-clock value depends on the reference SCS; the cell signals that reference so a UE on a wider-SCS BWP converts the offset correctly.
7MAC Control Elements — timing TS 38.321 §6.1.3
Closed-loop timing correction and NTN TA reporting are carried as MAC CEs. The Timing Advance Command trims the residual after open-loop pre-compensation; the TA Report (NTN) lets the UE tell the gNB its computed TA when drift crosses a threshold.
Timing MAC control elements
| MAC CE / field | Size | Range / values | Semantics | Spec |
|---|---|---|---|---|
| Timing Advance Command MAC CE | 1 octet | TAG ID (2b) + TA Command (6b, 0…63) | Closed-loop adjustment: T_A = (T_A_old − 31 … +31)·16·64/2^µ·T_c — refines residual TA after open-loop. | §6.1.3.4 |
| Absolute Timing Advance Command MAC CE | 2 octets | TA (12 bits, 0…3846) | Sets an absolute TA (e.g. at initial access / MsgB) rather than a delta. | §6.1.3.34 |
| TA Report MAC CE (NTN) | 2 octets | Timing Advance value (14 bits) | UE reports its computed TA; triggered when accumulated drift crosses offsetThresholdTA so the gNB can realign. | §6.1.3.x (Rel-17) |
| offsetThresholdTA (config) | RRC | enumerated thresholds | Drift magnitude that triggers a TA Report — balances reporting overhead vs UL-timing accuracy. | 38.331 |
8PHY / RACH / HARQ parameters TS 38.211/213/214/321
The physical-layer knobs NTN tunes: extended response windows and K-offset for RACH, extended HARQ process counts and feedback-disabling, and the RA-RNTI / MSGB-RNTI derivations.
RACH & HARQ parameters
| Parameter | Type / size | Range / values | Semantics | Spec |
|---|---|---|---|---|
| RA-RNTI | derived | 1 … 17 920 | 1 + s_id + 14·t_id + 14·80·f_id + 14·80·8·ul — identifies the RAR PDCCH. | 38.321 §5.1.3 |
| MSGB-RNTI (2-step) | derived | 17 921 … 35 840 | = RA-RNTI + 14·80·8·2 (offset 17 920) for 2-step RA. | 38.321 §5.1.3a |
| ra-ResponseWindow | ENUMERATED | up to sl1280 / extended | RAR monitoring window — widened for NTN so the UE looks after the RTT. | 38.331; 38.321 §5.1.4 |
| preambleTransMax | ENUMERATED | n3 … n200 | Max preamble transmissions; counter = value+1 → RA-problem to RRC. | 38.321 §5.1.4/.5 |
| nrofHARQ-ProcessesForPDSCH (NTN) | ENUMERATED | up to 32 | DL HARQ processes extended from 16→32 to keep the pipe full over the RTT. | 38.214; Rel-17 |
| harq-FeedbackEnablerDCI / disabled | config/per-process | enabled / disabled | Per-process HARQ-feedback disabling; reliability moves to RLC-AM when disabled. | 38.321; 38.331 |
| HARQ fill count | derived | N ≈ ⌈RTD/T_slot⌉+1 | Processes needed to avoid stop-and-wait stalling; exceeds 32 at GEO → feedback disabled. | TR 38.821 §7.1 |
| msg1-SubcarrierSpacing | ENUMERATED | 15/30/60/120 kHz | PRACH SCS; larger SCS improves Doppler tolerance at the cost of tighter timing. | 38.211 §6.3.3 |
9NAS / 5GMM timers & NTN parameters TS 24.501 §10.2
NTN largely reuses NAS with generous, second-scale timers; the real NTN work is discontinuous-coverage handling (unavailability periods, coverage-availability information) so a UE out of satellite view is not treated as failed.
Key 5GMM timers & NTN NAS parameters
| Timer / IE | Default | On expiry / meaning | NTN relevance | Spec |
|---|---|---|---|---|
| T3510 | 15 s | Registration request retransmission | >> even GEO registration (~2.5 s) — reused unchanged. | 24.501 §10.2 |
| T3512 | configurable (e.g. 54 min) | Periodic registration update | Interacts with discontinuous coverage so the UE isn't deregistered while out of view. | 24.501 §10.2 |
| T3502 | 12 min | Registration-attempt back-off | Avoids aggressive re-attempts across coverage gaps. | 24.501 §10.2 |
| T3346 | network-configured | Mobility-management back-off | Congestion/coverage back-off (value signalled by the network). | 24.501 §10.2 |
| Discontinuous-coverage / unavailability info | Rel-17/18 | UE announces expected out-of-coverage period | Lets UE sleep between passes; network holds context/paging for in-coverage windows. | 24.501; 23.501 |
| Coverage-availability information | Rel-18 | Predicted satellite-visibility windows | AMF aligns paging/reachability with coverage windows. | 23.501; Rel-18 |
10NGAP / F1AP & location IEs TS 38.413 · TS 38.473 · TS 23.273
A regenerative gNB uses standard NG/F1 signalling; NTN adds RAT/mode indications and, for regulation, network-verified UE location via LMF/NRPPa measurement procedures.
Interface & location IEs relevant to NTN
| IE / procedure | Interface | Purpose in NTN | Spec |
|---|---|---|---|
| NG Setup / RAN Node Name / TAC | NGAP (N2) | Regenerative gNB registers to the AMF like any NG-RAN node; earth-fixed TAC mapping avoids TAU storms. | 38.413 |
| User Location Information (NR CGI, TAI) | NGAP | Cell/TA reported to core; ambiguous across wide beams → complemented by verified location. | 38.413 §9 |
| Location Reporting / NRPPa measurement | NGAP ↔ LMF | Network-verified UE location: multi-RTT/timing to corroborate the UE GNSS report (anti-spoof). | 23.273; 38.305 |
| F1 Setup / gNB-DU Config | F1AP | For a DU-on-board regenerative split, F1 runs across the feeder link between ground CU and on-board DU. | 38.473 |
| PDU Session Resource Setup (N3 tunnel) | NGAP | Sets up the GTP-U tunnel to the UPF, tunnelled over the feeder link for a regenerative payload. | 38.413; 29.281 |
11NTN operating bands (RF) TS 38.101-5
NR-NTN FR1 uses MSS L/S-band for direct-to-handset service links; FR2-NTN adds Ka-band for high-G/T VSAT terminals and feeder links. Bands are FDD.
NR-NTN bands
| Band | Range | Uplink (UE→sat) | Downlink (sat→UE) | Duplex | Use |
|---|---|---|---|---|---|
| n255 | L-band | 1 626.5 – 1 660.5 MHz | 1 525 – 1 559 MHz | FDD | MSS direct-to-handset |
| n256 | S-band | 1 980 – 2 010 MHz | 2 170 – 2 200 MHz | FDD | MSS direct-to-handset |
| n510 / n511 / n512 | Ka (FR2-NTN) | ~27.5 – 30 GHz | ~17.3 – 20.2 GHz | FDD | VSAT / feeder (high G/T) |
Band ↔ terminal — match the band to the terminal G/T: S/L-band (n255/n256) for near-omni handsets; Ka (n510-512) only for high-gain dishes, since Ka adds ~23.5 dB more path loss than S-band for the same distance.
§Primary specifications (3GPP / ETSI)
Every field, type, range and unit on this page is traced to one of the specifications below. 3GPP Technical Specifications are published verbatim by ETSI under a parallel number (3GPP TS 38.331 = ETSI TS 138 331), so either citation is authoritative.
Sources used
| 3GPP | ETSI equivalent | Title / what it defines here |
|---|---|---|
| TS 38.331 | ETSI TS 138 331 | NR RRC — SIB19, NTN-Config, EphemerisInfo, TA-Info, ServingCellConfigCommon (§1–§6). |
| TS 38.213 | ETSI TS 138 213 | NR physical-layer procedures (control) — timing advance, K_offset, K_mac (§2, §6). |
| TS 38.321 | ETSI TS 138 321 | NR MAC — RA-RNTI/MSGB-RNTI, RA procedure, Timing-Advance & TA-Report MAC CEs (§7, §8). |
| TS 38.211 / 38.214 | ETSI TS 138 211 / 214 | NR PHY — numerology, PRACH, HARQ process counts (§8). |
| TS 24.501 | ETSI TS 124 501 | 5GS NAS (5GMM/5GSM) — T3510/T3512/T3502/T3346, discontinuous-coverage handling (§9). |
| TS 23.501 / 23.502 | ETSI TS 123 501 / 502 | 5GS architecture & procedures — reachability, coverage-availability info (§9). |
| TS 38.413 / 38.473 | ETSI TS 138 413 / 473 | NGAP (N2) and F1AP — NG/F1 setup, user-location, PDU-session resource (§10). |
| TS 23.273 / 38.305 | ETSI TS 123 273 / 138 305 | 5GS location services — network-verified UE location (§10). |
| TS 38.101-5 | ETSI TS 138 101-5 | UE RF for satellite access — NTN operating bands n255/n256, Ka FR2-NTN (§11). |
| TR 38.811 / 38.821 | ETSI TR 138 811 / 138 821 | NTN study — channel models, reference scenarios, delay/Doppler tables, link budgets (cross-page). |
All field names, types and ranges above are traced to the cited 3GPP clause (ASN.1 verbatim per the Rel-17 -r17 IEs; later releases extend some IEs — additional bands, coverage-availability info). Numeric ranges and granularities (e.g. ta-Common 0..66485757 × 4.072 ns, ta-CommonDrift ±257303, distanceThresh 0..65525 × 50 m) are the verbatim TS 38.331 values. No values are illustrative or fabricated.