R1-2600123
discussion
Discussion on 6GR HARQ related aspects
From Spreadtrum
Summary
This Spreadtrum/UNISOC contribution proposes a comprehensive framework for 6G HARQ, covering scheduling, timing, codebook simplification, processing time differentiation, and new features like faster ARQ retransmission and MCSC cross-carrier HARQ. It contains 24 Observations and 14 Proposals across general, downlink, and uplink HARQ aspects.
Position
Spreadtrum/UNISOC proposes studying a unified and integrated scheduling framework that natively supports all combinations of dynamic scheduling schemes (single-slot, repetition, multi-PDSCH/PUSCH, multi-cell, and multi-cell multi-PDSCH/PUSCH). They propose reducing the number of HARQ-ACK codebook types from the current five in NR, specifically addressing pain points such as Type-1's large feedback bits and complex generation, Type-2's last DCI issue and inter-cell coordination dependency, and the complexity of enhanced Type-2 for two PDSCH groups. They propose adopting a single basic PDSCH/PUSCH processing time per device type as the starting point, eliminating the dual-capability structure of NR, while also proposing differentiated processing times for diverse device types and further study on relaxation for energy efficiency and large bandwidth configurations. They propose studying L1-based dynamic indication for faster ARQ retransmission triggered by HARQ process status, requiring definition of the previous TB associated with a HARQ process ID. They propose cross-carrier HARQ retransmission within the Multi-Carrier Single Cell (MCSC) architecture, where an initial transmission on one carrier can be retransmitted on another carrier within the same cell.
Key proposals
- Proposal 1 (Sec 2.2): Study a unified and integrated scheduling framework for device types in 6GR, streamlining the design and supporting diverse time domain behaviors.
- Proposal 2 (Sec 2.2): Support both of dynamic PDSCH/PUSCH and configured grant PDSCH/PUSCH.
- Proposal 1 (Sec 2.3): Support TB level HARQ in 6GR.
- Proposal 2 (Sec 2.3): Further study other granularity HARQ mechanism, such as CBG, sub-TB with different QoS requirement.
- Proposal 1 (Sec 2.4): Study HARQ disable in 6GR for NTN and TN according to new requirements e.g. error tolerant HARQ and dynamic QoS scheduling.
- Proposal 1 (Sec 3.1.1): NR DL scheduling timing and HARQ-ACK timing indication can be baseline for 6GR.
- Proposal 1 (Sec 3.1.2): Study PDSCH processing time in 6GR from three principles: one basic PDSCH processing time for a device type, differentiated PDSCH processing time for diverse device types, and further study additional relaxation considering energy efficiency and large bandwidth.
- Proposal 1 (Sec 3.2): HARQ-ACK codebook should continue to be supported in 6GR, while addressing pain points and reducing the number of HARQ-ACK codebook types, targeting to support enhanced spectrum utilization/aggregation, multiple antenna schemes.
- Proposal 1 (Sec 3.3.1): Same as NR, L1 signal based HARQ-ACK report of PDSCH can still be supported in 6GR.
- Proposal 1 (Sec 3.3.2): DL HARQ-ACK report in 6GR use NR as a baseline, with further study on PUCCH resource determination procedure, PUSCH resource especially in multi-carrier scenarios, and simplify the timeline of UCI multiplexing.
- Proposal 1 (Sec 4.1): NR UL scheduling timing indication can be baseline for 6GR.
- Proposal 1 (Sec 4.2): For PUSCH preparation time in 6GR: one basic PUSCH processing time for a device type, differentiated PUSCH processing time for diverse device types, and further study additional relaxation considering large bandwidth.
- Proposal 1 (Sec 4.3): For UL HARQ, legacy scheduling is reused, i.e. NDI field indicates it is a new transmission or a retransmission, without HARQ-ACK.
- Proposal 1 (Sec 4.4): Study CB-PUSCH transmission for BSR/DSR, from RAN1 perspective.
- Proposal 1 (Sec 4.5): Study dynamic (e.g. DCI/MAC-CE) indication of UL/DL faster ARQ retransmission based on HARQ process status.
- Proposal 1 (Sec 4.6): Study scheduling aspects related within MCSC, including framework of UL transmission and DL reception across carriers within a cell and cross carrier HARQ retransmission.