R1-2601842
discussion
On downlink control channel, scheduling for downlink and uplink transmission
From Nokia
Nokia's prior position on
10.5.4.1
at
RAN1#124
· AI-synthesized, paraphrased
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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 baseline non-fallback DCI formats 0_1/1_1 more configurable through flexible DCI field sizes such as FDRA granularity. Proposes studying RRC-configured DCI sizes for USS to prevent DCI size ambiguities during BWP switching, and advocates replacing NR's hard-coded DCI size alignment procedure with configurable alignment to reduce blind decoding requirements. Proposes studying mechanisms for reliable DL control during bandwidth switching operation including common PDCCH candidates across different bandwidth assumptions and aligned DCI sizes. Proposes studying PDCCH detection feedback techniques within the PDSCH HARQ feedback framework to address missed DL assignments impacting adaptive DL HARQ operation, and requires support for PDCCH repetitions for increased reliability.
Summary
Nokia's contribution addresses downlink control channel design for 6G, presenting 14 proposals and 13 observations across areas including single-stage vs. two-stage DCI, DCI format types, PDCCH monitoring adaptation, and downlink control reliability. The document strongly favors evolving NR's single-stage DCI baseline and simplifying DCI formats, while proposing studies on RRC-configured DCI sizes and PDCCH detection feedback.
Position
Nokia requires single-stage DCI for common signaling search spaces and proposes RAN1 clarify the problem statement and evaluate drawbacks of two-stage DCI before design discussions. They require fallback DCI formats and only a single configurable non-fallback DCI format for single-cell PUSCH/PDSCH scheduling, opposing the need for ‘compact’ DCI formats 0_2/1_2. They propose studying RRC-configured DCI sizes to prevent BWP-related size ambiguities and configured DCI size alignment instead of hard-coded NR rules. They propose prioritizing SSSG switching over PDCCH skipping as the baseline PDCCH monitoring adaptation for UE power saving. They propose studying PDCCH detection feedback techniques as part of the PDSCH HARQ feedback framework to improve DL control reliability.
Key proposals
- Proposal 1 (Sec 2): 6GR to apply single-stage DCI at least for search spaces used for common signaling.
- Proposal 2 (Sec 2): RAN1 to clarify the problem (i.e. the related single-stage DCI shortcoming(s)) addressed by the two-stage DCI design and then discuss the potential design aspects.
- Proposal 3 (Sec 2): Study also the potential drawbacks of the two-stage DCI support, including impacts on e.g. scheduling complexity, latency, and reliability.
- Proposal 4 (Sec 3): 6GR to support at least the following DCI format types (with details being FFS): DCI format(s) for scheduling PUSCH, DCI format(s) for scheduling PDSCH, DCI format(s) for other purposes (i.e. GC-DCI).
- Proposal 5 (Sec 4): 6GR to adopt fallback DCI formats for scheduling PUSCH/PDSCH (i.e. the 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 6 (Sec 4): 6GR to support only a single (configurable / non-fallback) DCI format for scheduling PUSCH/PDSCH on a single serving cell (i.e. the NR equivalent of DCI formats 0_1/1_1, but no support for ‘compact’ DCI formats 0_2/1_2).
- Proposal 7 (Sec 4): 6GR to apply separate multi-cell PUSCH/PDSCH DCI formats (i.e. 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 allowing for better PDCCH load balancing.
- Proposal 8 (Sec 5): 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 aNB and UE for ‘BWP’ changes.
- Proposal 9 (Sec 5): 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 10 (Sec 6): For the baseline non-fallback DCI formats scheduling PUSCH/PDSCH (i.e. the NR equivalent of DCI formats 0_1/1_1) support a more flexible configuration of the DCI field sizes (such as e.g. 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 11 (Sec 7): 6GR to support methods to reduce unnecessary PDCCH monitoring to enable UE power saving.
- Proposal 12 (Sec 7): RAN1 to prioritize SSSG switching as baseline PDCCH monitoring adaptation for UE power saving.
- Proposal 13 (Sec 8): RAN1 to study the needed mechanisms to improve the reliability of DL control operation during bandwidth (part) switching operation.
- Proposal 14 (Sec 8): Study feedback techniques on PDCCH detection as part of the 6GR PDSCH HARQ feedback framework in AI 10.5.4.3 ‘HARQ related Aspects’.