Study on Narrow-Band Internet of Things (NB-IoT) / enhanced Machine Type Communication (eMTC) support for Non-Terrestrial Networks (NTN)
At the RAN#86 meeting, a new Study Item was approved for Internet of Things Non Terrestrial Network (IoT NTN) and revised in RAN#91 [4]. There was an email discussion on [91E][42][NTN_IoT_Roadmap] In RAN#91 with moderator summary and final proposal for GTW input in [5].
In RAN#91-e GTW session, the Chairman endorsed a Way Forward Proposal in [6] on email discussion on [50][New_proposals_approval]. This included guidance from RAN Chairman for NTN NR and NTN IoT as follows
- RAN#92E (June) to finalize the scope and project plan to deliver the essential minimum functionality of both NTN NR and NTN IoT (both NB-IoT and eMTC) within the existing TU allocations
- Detailed scoping exercise (NTN NR WID revision, NTN IoT WID approval) to be undertaken at RAN#92E (June)
The objectives for this document are, based on the outcomes of the Release-17 NR NTN WI [7] and Release-16 TR 38.821 [8], to study a set of necessary features/adaptations enabling the operation of the IoT NTN for 3GPP Release 17 with a priority on satellite access.
The first objective of this Study is to identify scenarios applicable to NB-IoT/eMTC [RAN1, RAN2], including:
- Bands of interest in sub 6 GHz
- Device type with PC3 or PC5 (LEO and GEO)
- Satellite constellation orbit LEO and GEO
- Transparent payload.
- Link budget
NOTE 1: This first objective will be based on the scenarios documented in TR 38.821.
NOTE 2: UE mobility assumptions follow terrestrial NB-IoT/eMTC assumptions.
The second objective is, for the above identified scenarios, to study and recommend necessary changes to support NB-IoT and eMTC over satellite, reusing as much as possible the conclusions of the studies performed for NR NTN in TR38.821. This objective will address the following items:
- Aspects related to random access procedure/signals [RAN1, RAN2]
- Mechanisms for time/frequency adjustment including Timing Advance, and UL frequency compensation indication [RAN1, RAN2]
- Timing offset related to scheduling and HARQ-ACK feedback [RAN1, RAN2]
- Aspects related to HARQ operation [RAN2, RAN1]
- General aspects related to timers (e.g. SR, DRX, etc.) [RAN2]
- RAN2 aspects related to idle mode and connected mode mobility [RAN2]
- RLF-based for NB-IoT
- Handover-based for eMTC
- System information enhancements [RAN2]
- Tracking area enhancements [RAN2]
NOTE 3: GNSS capability in the UE is taken as a working assumption in this study for both NB-IoT and eMTC devices. With this assumption, UE can estimate and pre-compensate timing and frequency offset with sufficient accuracy for UL transmission. Simultaneous GNSS and NTN NB-IoT/eMTC operation is not assumed.
Recommendations for NB-IoT and recommendations for eMTC will be documented in the conclusions.