R1-2600055
discussion
Uplink transmission scheme(s) for uplink channels
From FUTUREWEI
Summary
This Futurewei contribution to 3GPP RAN1#124 presents 10 proposals and 2 observations on 6G UL transmission schemes, covering the MIMO/RS/CSI framework, AI/ML integration, frequency-selective precoding, QCL/TCI enhancements, UL power control, timing advance, and carrier switching. The document advocates adopting the 5G NR MIMO framework as a baseline while introducing several specific enhancements including per-subcarrier matched-filter precoding and AI/ML-based DMRS optimization.
Position
Futurewei proposes adopting the 5G NR MIMO/RS/CSI framework as a starting point for 6G development without fundamental paradigm shifts, while studying targeted enhancements for upper midband (UMB) support including larger Tx/Rx antenna elements with hybrid architectures. They propose studying AI/ML as an integral part of the MIMO framework from day-1, identifying specific use cases to facilitate AI/ML-ready framework design evaluation. For UL transmissions, they propose studying fine-granularity frequency-selective precoding (per-subcarrier matched-filter) that achieves both finest precoding granularity and wideband channel estimation simultaneously, presenting a technical case that 5G NR schemes cannot improve both at the same time. They propose extending the unified TCI framework to support UL signals (SRS) as QCL source RS for DL TCI states, and consolidate UL power control and timing advance mechanisms through flexible component associations via only the unified TCI framework. They propose studying UL carrier switching that maintains transmission continuity by moving all transmissions to the switching-to carrier and eliminating switching-back operations.
Key proposals
- Proposal 1 (Sec 2.2): Adopt 5G NR MIMO/RS/CSI framework as a starting point for 6G, studying enhancements for UMB support, general SE/UPT performance, and fast beam acquisition for FR2.
- Observation 1 (Sec 2.3): AI/ML should be considered as part of the MIMO framework from day-1 since AI/ML-assisted operation may impact fundamental air-interface tradeoffs (overhead vs. performance and robustness).
- Proposal 3 (Sec 2.3): Identify a few AI/ML use cases to facilitate the study and assessment of AI/ML-ready MIMO framework design.
- Proposal 4 (Sec 3.1): Consider including AI/ML-based DMRS configuration optimization as a candidate approach for UL DMRS enhancement in 6G study.
- Proposal 5 (Sec 3.2): Study fine-granularity frequency-selective precoding in UL transmissions without the need of separate/multiple receive-side channel estimations, with per-subcarrier matched filter precoding as one example.
- Proposal 6 (Sec 3.3): Consider the unified TCI framework developed in 5G NR as a starting point for 6GR QCL/TCI framework.
- Proposal 7 (Sec 3.3): Support QCL/TCI enhancements to enable the use of UL signal (e.g., SRS) as QCL source RS of DL TCI states.
- Proposal 8 (Sec 3.4): Study to reuse and simplify 5G NR UL power control framework through providing flexible associations among four components (UL transmission, reference transmission, open-loop PC parameters, closed-loop TPC parameters) via a unified TCI framework.
- Proposal 9 (Sec 3.5): Study to support UL timing advance indication via a unified TCI framework, associating a target UL RS/channel to a TAG via a TAG state indication for TA determination.
- Proposal 10 (Sec 3.6): Study efficient UL carrier switching incorporating SRS carrier-based switching and PUCCH/PUSCH carrier-based switching, reducing/eliminating required switching-back and maintaining one set of signals/channels over n carriers.