R1-2508727
discussion
Discussion on waveform and multiple access for 6G Radio
From OPPO
Summary
OPPO presents 12 proposals and 1 observation on 6G Radio (6GR) waveform and multiple access design, advocating a modular and scalable air interface based on 5G NR waveforms with minimized additions. Key positions include rejecting DFT-s-OFDM for downlink baseline, prioritizing implementation-based low-PAPR schemes for uplink, and establishing OMA as the baseline for multiple access.
Position
OPPO proposes a modular 6GR air interface design with a mandatory baseline functionality set scalable from 6G IoT to eMBB, and opposes DFT-s-OFDM as an additional DL baseline waveform due to limited coverage gain (up to 1.5dB PAPR reduction), multiuser scheduling restrictions (TDM-only between CP-OFDM and DFT-s-OFDM UEs), and increased UE complexity from additional IDFT modules. They require only one DL waveform for initial access to avoid blind detection or doubling synchronization sequences. For UL low-PAPR schemes, OPPO prioritizes implementation-based approaches without specification impact and proposes evaluating schemes using PAPR reduction and SINR degradation @10% BLER rather than Net Gain in RAN1, deferring MPR evaluation to RAN4. On multiple access, OPPO proposes OMA as the baseline for 6GR, with a single MA scheme per waveform to serve all usage scenarios.
Key proposals
- Proposal 1 (Sec 2): A unified 6GR baseline waveform is studied to fulfil the requirements of eMBB and 6G IoT. The baseline waveform is used for 6G HRLLC.
- Proposal 2 (Sec 2): Study waveforms to fulfil the requirement of 6G Sensing and 6G NTN. Strive for reusing the 6GR baseline waveform; an additional waveform can be considered only if significant gain is justified for a specific vertical and only supported by that vertical's BS/UE.
- Proposal 3 (Sec 3.1): For studying additional waveforms, evaluate proposals using agreed 6GR waveform (CP-OFDM DL, CP-OFDM/DFT-s-OFDM UL) as benchmark, considering spectrum efficiency, coverage, complexity, compatibility/neutrality for other proposals, flexible resource allocation, and 5G/6G spectrum sharing.
- Proposal 4 (Sec 3.1): Support up to 2 waveforms in DL and up to 2 in UL for 6GR baseline, with at least 1 mandatory waveform per direction for all device types (e.g., CP-OFDM in DL, DFT-s-OFDM in UL).
- Proposal 5 (Sec 3.2): Only one DL waveform is supported for 6GR initial access procedure.
- Proposal 7 (Sec 3.2): DFT-s-OFDM is not supported as additional DL baseline waveform for 6GR, due to limited performance gain, restriction on multiuser scheduling, and extra UE complexity. DL DFT-s-OFDM for NTN can be further studied in NTN agenda.
- Proposal 8 (Sec 3.3): For uplink low-PAPR waveform proposals, the evaluation criterion is PAPR reduction and SINR degradation @10% BLER. Net gain including MPR can be evaluated by RAN4.
- Proposal 9 (Sec 3.3): Prioritize implementation-based schemes without specification impacts; study additional gain from schemes with specification impacts.
- Proposal 10 (Sec 3.4): For DFT-s-OFDM for UL with multiple layers, the evaluation criterion is PAPR reduction and SINR degradation @10% BLER.
- Observation 1 (Sec 3.4): Based on preliminary results, DFT-s-OFDM for UL with 2 layers suffers 1dB~6dB SINR loss @10% BLER at different MCS, although it brings about 1.6dB PAPR reduction at 10% probability over 2-layer CP-OFDM.
- Proposal 11 (Sec 4): Study multiple access (MA), targeting a single MA scheme for each waveform, to fulfil the requirement of all 6G usage scenarios using this waveform.
- Proposal 12 (Sec 4): Orthogonal multiple access (OMA) is the baseline for 6GR. Evaluate OMA proposals using 5G NR as benchmark, considering spectrum efficiency, coverage, complexity, compatibility/neutrality, flexible resource allocation, and 5G/6G spectrum sharing.