R1-2600042
discussion
On downlink control channel, scheduling for downlink and uplink transmission
From Nokia
Summary
Nokia presents 10 proposals and 8 observations on 6G downlink control channel design, covering DCI formats, DCI size alignment, DCI content flexibility, and downlink control reliability. The document argues for simplification of DCI format types compared to NR, configurable DCI sizes to resolve BWP ambiguity issues, and enhanced reliability mechanisms including PDCCH repetitions and detection feedback.
Position
Nokia proposes reducing the number of DCI format types for 6G compared to NR by eliminating compact DCI formats 0_2/1_2 and instead making the baseline non-fallback DCI formats 0_1/1_1 more configurable through flexible DCI field sizes such as FDRA granularity. They propose studying RRC-configured DCI sizes for USS to prevent DCI size ambiguities during BWP switching, and advocate replacing NR's hard-coded DCI size alignment procedure with configurable alignment to reduce blind decoding requirements. Nokia supports studying mechanisms for reliable DL control during bandwidth switching operation, including common PDCCH candidates across different bandwidth assumptions and aligned DCI sizes. They propose studying PDCCH detection feedback techniques within the PDSCH HARQ feedback framework to address missed DL assignments impacting adaptive DL HARQ operation, and require support for PDCCH repetitions for increased reliability.
Key proposals
- Proposal 1 (Sec 2): 6GR to support at least the following DCI format types: DCI format(s) for scheduling PUSCH, DCI format(s) for scheduling PDSCH, DCI format(s) for other purposes (i.e. GC-DCI), with details being FFS.
- Proposal 2 (Sec 3): 6GR to adopt fallback DCI formats for scheduling PUSCH/PDSCH (NR equivalent of DCI formats 0_0/1_0) and non-fallback DCI formats for scheduling PUSCH/PDSCH to enable efficient control information delivery.
- Proposal 3 (Sec 3): 6GR to support only a single configurable/non-fallback DCI format for scheduling PUSCH/PDSCH on a single serving cell (NR equivalent of DCI formats 0_1/1_1, but no support for compact DCI formats 0_2/1_2).
- Proposal 4 (Sec 3): 6GR to apply separate multi-cell PUSCH/PDSCH DCI formats (NR equivalent of DCI formats 0_3/1_3) if multi-cell PUSCH/PDSCH scheduling is to be supported. Consider/study the combination of multi-cell PUSCH/PDSCH scheduling and single-cell PUSCH/PDSCH self-scheduling for better PDCCH load balancing.
- Proposal 5 (Sec 4): Study 6GR support for RRC configured DCI sizes (before potential DCI size alignment) of DCI formats scheduling PUSCH/PDSCH from USS to prevent DCI sizes ambiguities between gNB and UE for BWP changes.
- Proposal 6 (Sec 4): RAN1 to study changes to the DCI size alignment procedure of NR including configured DCI size alignment instead of hard-coded rules reducing the number of DCI sizes and the required number of BDs.
- Proposal 7 (Sec 5): For the baseline non-fallback DCI formats scheduling PUSCH/PDSCH (NR equivalent of DCI formats 0_1/1_1), support a more flexible configuration of the DCI field sizes (such as FDRA granularity) reducing the need for a large number of DCI formats, improving reliability for same AL or reducing the DL control load/block using a smaller AL.
- Proposal 8 (Sec 6): RAN1 to study the needed mechanisms to improve the reliability of DL control operation during bandwidth (part) switching operation.
- Proposal 9 (Sec 6): 6GR to support PDCCH repetitions for increased reliability. Details are FFS.
- Proposal 10 (Sec 6): Study feedback techniques on PDCCH detection as part of the 6GR PDSCH HARQ feedback framework in AI 10.5.4.3 HARQ related Aspects.