R1-2508735
discussion
Waveform for 6GR air interface
From Huawei
Summary
This Huawei contribution presents 11 proposals and 18 observations across 6G waveform design areas including low PAPR I/Q-offset DFT-s-OFDM, Pruning QAM modulation, DL DFT-s-OFDM for energy saving, and UL multi-layer DFT-s-OFDM. The document provides evaluation assumptions, simulation results, and net gain comparisons for these waveform enhancements, proposing specific study items for the 6GR air interface.
Position
Huawei proposes I/Q-offset DFT-s-OFDM as a low PAPR waveform enhancement that exploits conjugate symmetric frequency-domain redundancy, and proposes studying multi-user frequency overlap scheduling to mitigate spectral efficiency loss from spectrum extension. They present technical case that I/Q-offset DFT-s-OFDM generalizes other offset QAM proposals (e.g., pi/2 BPSK, O-QAM) and achieves better net gain than DFT-s-OFDM FDSS-SE and FDSS-CE with QPSK rotation, especially at larger spectrum extension factors (3/8, 7/16). For modulation, Huawei proposes studying 8-Pruning QAM under DFT-s-OFDM for coverage enhancement in 1.6-2.0 bit/s/Hz range and under CP-OFDM for ISAC with constant modulus sensing performance superior to 16QAM. They propose DL DFT-s-OFDM for on-demand synch. signal/LP-WUS transmission on a Low Power Radio (LPR) to compensate 6dB coverage loss from reduced TRX, yielding approximately 3 dB net gain over CP-OFDM. For UL MIMO, they propose supporting at least 2-layer DFT-s-OFDM with diagonal precoding to maintain low PAPR, showing that SNR degradation versus CP-OFDM disappears with 64 or more Rx antennas at the base station.
Key proposals
- Proposal 1 (Sec 2.1): Take Tables 1~4 as the start point for low PAPR waveform enhancement evaluations.
- Proposal 2 (Sec 2.2): Study how to utilize the signal property of frequency redundancy in spectrum extension based schemes to enhance multi-user experience. For example, scheduled PRBs for multiple UEs are overlapped partially.
- Proposal 3 (Sec 2.3.1): Study lower PAPR waveform enhancement providing net gain vs NR DFT-s-OFDM waveform. FFS the exact supported lower PAPR waveform enhancement.
- Proposal 4 (Sec 2.3.2): Study spectrum extension/truncation plus FDSS lower PAPR waveform enhancement, e.g., I/Q-offset DFT-s-OFDM, DFT-s-OFDM FDSS-SE.
- Proposal 5 (Sec 3.2.1): Study pruning QAM under DFT-s-OFDM type waveform(s) for coverage enhancement.
- Proposal 6 (Sec 3.2.2): Study pruning QAM under CP-OFDM waveform for ISAC.
- Proposal 7 (Sec 4.1): For DL DFT-s-OFDM on-demand synch. signal/LP-WUS, the performance evaluation criterion from waveform perspective is net gain = Tx power gain relative to the reference – Required SNR degradation relative to the reference, with detection rate below 1% and false alarm rate below 1%.
- Proposal 8 (Sec 4.1): Take Table 9 as a start point for DL DFT-s-OFDM waveform evaluation for on-demand synch. signal/LP-WUS.
- Proposal 9 (Sec 4.2): Study DL DFT-s-OFDM for on-demand synch. signal/DL-WUS for coverage enhancement, network energy saving and UE energy saving under related agendas.
- Proposal 10 (Sec 5.1.1): Take Table 11 as the start point for UL multi-layer DFT-s-OFDM link level net gain evaluations.
- Proposal 11 (Sec 5.2): At least 2-layers uplink DFT-s-OFDM (including enhancement) waveform with observed coverage net gains should be supported in 6GR. The maximum number of layers should be further studied in 6GR MIMO agenda.