R1-2508908
discussion
Views on overall design and techniques for 6GR air interface
From LG Electronics
Summary
LG Electronics presents comprehensive views on 6G physical layer design across 11 major topic areas, including synchronization, bandwidth, BWP, spectrum utilization, control/data channels, MIMO, MRSS, NTN, and ISAC. The document contains 31 numbered proposals and numerous observations addressing lessons learned from 5G NR and proposed study directions for 6G standardization.
Position
LG Electronics proposes studying an increased default periodicity for synchronization signals beyond 20 ms, compensated by allocating more OFDM symbols to PSS/SSS/PBCH to enhance per-attempt detection performance. They oppose removing center frequency alignment requirements for DL/UL BWP in unpaired spectrum from lessons learned, and oppose the sub-bullet claiming DCI-based BWP switching has reliability issues, arguing gNB confirmation via scheduled PUCCH/PUSCH detection prevents misalignment. They require further verification of three spectrum aggregation lessons (Pcell-only functionalities, per-carrier HARQ, late UL TX switching) before accepting them as baseline. They prefer DFT-s-OFDM as an additional DL waveform for NTN to reduce PAPR and improve power efficiency, and propose adaptive RRC configuration based on satellite position for NGSO scenarios. For MRSS, they propose that UL/DL link direction alignment in same time/frequency resources between NR and 6GR is required, but identical frame format configurations are not necessary.
Key proposals
- Proposal 1 (Sec Synchronization): Study the impact of increasing the default periodicity assumed by the UE for synchronization signal detection, and study allocating more OFDM symbols to PSS, SSS, and PBCH to compensate for increased periodicity.
- Proposal 1 (Sec Initial Access): Study initial access procedure, random access, paging, and measurement with physical layer aspects including bandwidth configuration for initial access, 4-step/2-step RACH, UL Tx beam selection via Msg1/Msg3, time/frequency tracking RS for IDLE/Inactive UEs, integration of L1/L3 measurements, PRACH-based SIB request, and PEI mechanisms via DCI or LP-WUS.
- Proposal 1 (Sec Bandwidth - Minimum CBW): Design common channels/signals such as SS/PBCH using 15 kHz SCS targeting 5 MHz operation, and verify operability at 3 MHz for narrowband operation.
- Proposal 4 (Sec BWP framework): Remove the sub-bullet about DCI-based BWP switching reliability issues from proposed observation 8.1c, arguing that missed DCI can be confirmed by detecting scheduled PUCCH/PUSCH on the new BWP.
- Proposal 7 (Sec Spectrum utilization): Question and require further verification of three lessons-learned topics: some functionalities supported only on Pcell, features defined per carrier leading to sub-optimal performance, and late introduction of UL TX switching.
- Proposal 9 (Sec Spectrum utilization): Study unified framework for cell/carrier adaptation/switching, fast SCell activation/deactivation, flexible DL-UL carrier coupling, carrier ON/OFF including SSB adaptation, efficient aggregation of fractional carriers, and multi-carrier common channel design for all RRC states.
- Proposal 10 (Sec PHY DL Control): Study dynamic adaptation of DL control resources/parameters, adaptive reduction of UE blind decoding and DL control overhead, and unified DL control resource structure accommodating multiple UE types.
- Proposal 12 (Sec PHY Data Channel): Study scheduling enhancements considering enhanced multi-carrier operation, including TB mapping across multiple carriers.
- Proposal 13 (Sec PHY Data Channel): Study mechanisms to support PDSCH/PUSCH transmissions crossing slot boundaries from Day 1.
- Proposal 17 (Sec MIMO): 6G MIMO should harmonize with AI/ML and NES/UES features, extend massive MIMO scale, and reduce signaling/RS overhead compared to 5G NR MIMO.
- Proposal 24 (Sec MRSS): Study radio resource utilization aspects including rate matching of 6GR signals/channels around NR signals/channels, semi-static TDM/FDM between NR and 6GR, and NR signal/channel sharing with 6GR.
- Proposal 27 (Sec NTN): Technical aspects affected by NTN characteristics further include power efficiency for DL/UL transmission, TN-NTN and NTN-NTN mobility, 6G NTN coexistence with IoT-NTN or NR-NTN in same beam, satellite moving and switching, and multi-carrier operation with same or different satellites.
- Proposal 28 (Sec ISAC): Prioritize object detection and tracking use cases for ISAC study in Rel-20.
- Proposal 31 (Sec ISAC): 6G waveform and frame structure needs to be designed so that any necessary modification for sensing should be easily applied in a later stage.