NTN

IoT-NTN: NB-IoT and LTE-M over satellite

Satellite assistance information in LTE system information for NB-IoT and eMTC, and how the UE uses it in idle mode.

IoTNTN4G

Overview

TS 36.331 defines NTN-specific system information: SystemInformationBlockType31 carries satellite assistance information for the serving cell and is only signalled for an NTN cell; SIB32 carries satellite assistance information for prediction of discontinuous coverage; SIB33 (Rel-18) carries satellite assistance information for neighbour cells.

TS 36.304 defines Earth-fixed, quasi-Earth-fixed and Earth-moving cells. A UE with satellite assistance information from SIB32 can determine that it is out of coverage. Location-based measurement initiation uses distanceThresh and referenceLocation broadcast in SIB31.

Call flow

1
Satellite celltoUE
SIB31
Serving cell satellite assistance information.
2
Satellite celltoUE
SIB32
Information to predict discontinuous coverage.
3
Satellite celltoUE
SIB33 (Rel-18)
Satellite assistance information for neighbour cells.

Specifications

Spec	What it covers
TS 36.331	SIB31, SIB32 and SIB33.
TS 36.304	NTN idle-mode behaviour, out-of-coverage determination and location-based measurement initiation.

Changes by release

Release	Change
Rel-17	SystemInformationBlockType31-r17 and SystemInformationBlockType32-r17.
Rel-18	SystemInformationBlockType33-r18 for neighbour cells.

IoT power saving

NB-IoT and LTE-M power saving: PSM and eDRX

Power Saving Mode and extended idle-mode DRX, and what they mean for reachability.

IoT4G

NTN

NR-NTN mobility and satellite switch

Satellite assistance in SIB19 and how NR uses it for synchronisation, measurement initiation, conditional handover and satellite switch.

5GNTN

Idle mode

Cell selection and reselection

How an idle or inactive UE selects a cell by the S-criterion and keeps the best one by priority and ranking.

4G5GNTNIoT