R1-2600063
discussion
Discussion on 6G NTN
From FUTUREWEI
Summary
This Futurewei Tdoc for the 6G NR study item (FS_6G_Radio) presents one observation and four proposals focused on 6G Non-Terrestrial Networks (NTN). It recommends studying VLEO NTN scenarios at 300 km, and proposes several power-saving and error-correction mechanisms for GNSS-based operations, including PRACH format redesign and closed-loop timing/frequency control.
Position
Futurewei proposes studying Very Low Earth Orbit (VLEO) NTN scenarios at an orbital height of 300 km for 6GR, while defaulting to Rel-17 NR-NTN LEO and GEO parameters for other cases. To mitigate the increased UE power consumption from GNSS-based NTN operation, they propose considering GNSS position fix time intervals and satellite elevation angles in the 6GR PRACH format design. They recommend studying network-controlled timing advance adjustments in both positive and negative directions during random access to correct GNSS position errors. Finally, they propose studying closed-loop frequency control to allow the network to adjust UE carrier frequency for correcting UE-specific frequency compensation errors during random access and in RRC connected mode.
Key proposals
- Proposal 1 (Sec 2.1): For the study of 6GR GNSS-based and GNSS-less operations, RAN1 considers VLEO NTNs with an orbital height of [300 km], additionally for other scenarios, RAN1 adopts the Rel-17 NR-NTN LEO and GEO along with their parameters (with changes if needed reflecting 6G radio interface).
- Observation 1 (Sec 2.2): GNSS-based NTN operation increases UE’s power consumption.
- Proposal 2 (Sec 2.2): To conserve UE’s battery energy in 6GR GNSS-based operations, RAN1 considers time intervals between GNSS position fixes and satellite elevation angles in the 6GR PRACH format design.
- Proposal 3 (Sec 2.2): For 6GR GNSS-based operations, RAN1 studies timing advance (during random-access), enabling the network to adjust timing advance values in both positive and negative directions.
- Proposal 4 (Sec 2.2): To conserve UE’s battery energy in 6GR GNSS-based operations, RAN1 studies the options below to deal with NTN UE-specific frequency compensation errors: Option 1: closed-loop frequency control, allowing the network to adjust UE carrier frequency during the random-access phase and in RRC connected mode; Option 2: other approaches (e.g., implementation).