R1-2600188
discussion
On waveform enhancements/additions for 6G Radio
From OPPO
Summary
OPPO presents 10 proposals and 1 observation on 6G waveform enhancements, advocating for a modular, scalable air interface design that prioritizes reusing 5G NR waveforms (CP-OFDM/DFT-s-OFDM) for terrestrial network communication and opposes DFT-s-OFDM for downlink due to limited gain and scheduling restrictions.
Position
OPPO proposes a modular 6GR air interface design with a Mandatory baseline functionality set serving as common basis across device types from 6G IoT to eMBB. They require waveform enhancement studies to focus primarily on 6G TN communication requirements, striving to reuse TN waveforms for NTN and Sensing, with NTN-specific and Sensing-specific enhancements allowed only when substantial performance gain is justified and prohibited for use in TN communication. They present technical case against DFT-s-OFDM as an additional DL waveform for TN communication, citing only up to 1.5dB coverage gain insufficient to justify multiuser scheduling restrictions limited to TDM-only multiplexing and increased UE complexity from additional IDFT module. They oppose using DCI-based explicit indication for dynamic UL waveform switching, proposing instead implicit mechanisms triggered by transmission rank, resource allocation, or frequency band to avoid unnecessary overhead. They prioritize implementation-based UL low-PAPR schemes without specification impacts over those requiring standardization efforts, and evaluate 2-layer DFT-s-OFDM for UL as suffering 1-6dB SINR loss at 10% BLER with different MCS levels despite 1.6dB PAPR reduction.
Key proposals
- Proposal 1 (Sec How to treat waveform enhancements for 6GR NTN, Sensing): The study on 6GR waveform enhancements focuses on the requirements of 6G TN communication (i.e., eMBB and 6G IoT). Strive for reusing the 6G TN communication waveform for NTN. Consider an NTN-specific waveform enhancement when a substantial performance gain is justified. The NTN-specific waveform enhancement, if accepted, is not used for 6G TN communication.
- Proposal 2 (Sec How to treat waveform enhancements for 6GR NTN, Sensing): Study on waveform enhancements or additional waveform for 6G Sensing in the Sensing agenda. Strive for reusing the 6G TN communication waveform for 6G Sensing. The Sensing-specific waveform enhancement or additional waveform can be considered if substantial gain over the TN communication waveform can be justified. The Sensing-specific waveform enhancement or additional waveform, if accepted, is not used for 6G communication.
- Proposal 3 (Sec On waveform enhancements for TN communication): For studying the waveform enhancements for 6GR, besides the evaluation of spectrum efficiency and coverage, the following should also be considered: NW and UE side complexity, compatibility and neutrality for proposals in other areas, support flexible frequency-domain and time-domain resource allocation, support of efficient 5G/6G spectrum sharing.
- Proposal 4 (Sec On waveform enhancements for TN communication): For 6GR TN communication, support up to 2 waveforms in DL and up to 2 waveforms in UL, e.g., one optimized for spectrum efficiency, one optimized for coverage. At least 1 waveform in DL and 1 waveform in UL are mandatorily supported for all device types, e.g., CP-OFDM in DL and DFT-s-OFDM in UL.
- Proposal 5 (Sec DFT-s-OFDM for DL): Only one DL waveform is supported for 6GR initial access procedure.
- Proposal 6 (Sec DFT-s-OFDM for DL): For downlink low-PAPR proposals the evaluation criterion is the PAPR reduction and SINR degradation @10% BLER.
- Proposal 7 (Sec DFT-s-OFDM for DL): DFT-s-OFDM is not supported as additional DL waveform for 6GR TN communication, due to limited performance gain, restriction on multiuser scheduling and extra complexity on UE side. DL DFT-s-OFDM for NTN can be further studied.
- Proposal 8 (Sec Low-PAPR waveform for UL): For Net Gain evaluation for uplink low-PAPR proposals, check and compare the results from different proponents, and identify whether more aligned parameter combinations need to be identified to draw the conclusion.
- Proposal 9 (Sec Low-PAPR waveform for UL): Prioritize the implementation-based schemes without specification impacts. Study additional gain from schemes with specification impacts.
- Observation 1 (Sec DFT-s-OFDM for UL with multiple layers): Based on the link-level evaluation results, DFT-s-OFDM for UL with 2 layers suffers 1dB ~ 6dB SINR loss @10% BLER with different MCS levels, although it brings about 1.6dB PAPR reduction at 10% probability over 2-layer CP-OFDM.
- Proposal 10 (Sec Dynamic UL waveform switching): Postpone the discussion on waveform switching/selection until the waveform decisions have stabilized. When the study starts, consider all potential solutions, including explicit indication as well as implicit mechanisms without DCI overhead. Study on dynamic UL waveform switching during initial access is deprioritized.