R1-2601818
discussion
Discussion on HARQ related aspects
From Spreadtrum
Spreadtrum's prior position on
10.5.4.3
at
RAN1#124
· AI-synthesized, paraphrased
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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). Proposes 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. Proposes 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. Proposes 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. Proposes 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.
Summary
This Spreadtrum contribution discusses 6G HARQ-related aspects, presenting 22 observations and 15 proposals across feedback timing, codebook design, processing timelines, ARQ integration, and HARQ process management. The document advocates for simplifying NR's complex HARQ framework by reducing codebook types, adopting a single reference time for feedback, and introducing cross-carrier retransmission for Gothia cells.
Position
Spreadtrum proposes simplifying 6G HARQ timing by introducing a single reference time and one point for HARQ-ACK on PUCCH and UCI mapping on PUSCH, arguing against NR's complex symbol-level overlap checking with variable PUCCH resource sets and PRI-based resource determination that changes within the same slot. They recommend retaining DCI-indicated slot offset K1 for DL HARQ feedback timing while advocating for a single basic PDSCH/PUSCH processing time per device type, with additional relaxation for energy efficiency and large bandwidth configurations (e.g., 200 MHz or 400 MHz). For codebook design, they propose continuing Type-2 HARQ-ACK codebook with enhancements to address the last DCI issue and inter-cell DAI coordination dependency, while reducing the total number of codebook types from five. They additionally propose studying cross-carrier HARQ retransmission for the Gothia cell multi-carrier architecture and DCI-based UL faster ARQ retransmission indications triggered by HARQ process failure status.
Key proposals
- Proposal 1 (Sec HARQ-ACK feedback timeline): Study a single reference time and one point for HARQ-ACK on PUCCH and UCI mapping on PUSCH.
- Proposal 2 (Sec DL HARQ feedback timing): For feedback timing between control/dynamic data reception and DL HARQ-ACK timing, it can be slot offset K1 indicated by DCI.
- Proposal 3 (Sec PDSCH processing time): Study PDSCH processing time in 6GR from the following three principles:
- Proposal 4 (Sec PDSCH processing time): One basic PDSCH processing time for a device type
- Proposal 5 (Sec PDSCH processing time): Differentiated PDSCH processing time for diverse device Types
- Proposal 6 (Sec PDSCH processing time): Further study additional relaxation considering energy efficiency and large bandwidth
- Proposal 7 (Sec PUSCH preparation time): For PUSCH preparation time in 6GR, it has:
- Proposal 8 (Sec PUSCH preparation time): One basic PUSCH processing time for a device type
- Proposal 9 (Sec PUSCH preparation time): Differentiated PUSCH processing time for diverse device Types
- Proposal 10 (Sec PUSCH preparation time): Further study additional relaxation considering large bandwidth
- Proposal 11 (Sec HARQ-ACK feedback granularity): In 6GR, support CBG level granularity for HARQ-ACK feedback, and further study PDSCH level and TBG level feedback.
- Proposal 12 (Sec HARQ-ACK codebook/payload details): Type-2 HARQ-ACK codebook should continue to be supported in 6GR with enhancement, while addressing the above pain points and reducing the number of HARQ-ACK codebook types, targeting to support enhanced spectrum utilization/aggregation, multiple antenna schemes.
- Proposal 13 (Sec HARQ-ACK disabling/enabling): Study HARQ disable in 6GR for NTN and TN according to new requirements e.g. error tolerant HARQ and dynamic QoS scheduling.
- Proposal 14 (Sec Cross-layer HARQ and ARQ integration/interaction): Study DCI indication of UL faster ARQ retransmission based on HARQ process status. And study UE assistant information for DL faster ARQ retransmission.
- Proposal 15 (Sec HARQ process management): Study Cross carrier HARQ retransmission for Gothia cell.