R1-2601835
discussion
On downlink transmission schemes for downlink control channels in 6GR
From Nokia
Nokia's prior position on
10.5.2.1
at
RAN1#124
· AI-synthesized, paraphrased
verify sources →
Proposes retaining the baseline 5G NR PDCCH structure—including CORESET, CCE, REG, blind decoding, search spaces, aggregation levels, and QPSK modulation with transparent DM-RS-based precoding—for 6GR, arguing this flexibility is sufficient for 6G services and essential for smooth Multi‑Radio Spectrum Sharing (MRSS) operation. Proposes studying extensions such as non-interleaved CCE-to-REG mapping for CORESET0 above 5MHz and DM-RS design changes to maximize coexistence between CORESET#0 and dedicated CORESETs. Proposes increasing the maximum number of configured search spaces and allowing separation of paired DCI formats for PDSCH/PUSCH scheduling across different search spaces to reduce monitoring burden. Proposes that 6G Day-1 mandatory UE capabilities include flexible CORESET placement within a slot and support for more than one CORESET, while also proposing simplifications to the PDCCH monitoring capabilities framework by reviewing the need for limits on the maximum number of DCI sizes and CCEs. For power saving, proposes baselining C-DRX and prioritizing SSSG switching over PDCCH skipping due to its wider adaptation variety.
Summary
Nokia presents 23 proposals and 5 observations on the 6GR downlink control channel (PDCCH) design, advocating for reusing and evolving the NR PDCCH framework—including CORESET, CCE, REG, search spaces, blind decoding, and DMRS—as the baseline for 6G, with targeted enhancements for MRSS, UE monitoring flexibility, and reduced complexity.
Position
Nokia proposes reusing NR's PDCCH structure (CORESET, CCE, REG, search spaces) as the baseline for 6GR, arguing this provides sufficient flexibility and enables smooth MRSS with 5G through aligned PDSCH rate matching and per-CCE CORESET/SS sharing. They require QPSK modulation and transparent DM-RS based precoding with configurable scrambling ID for MU-MIMO, and propose studying DM-RS design changes to maximize coexistence between CORESET#0 and dedicated CORESETs. Nokia proposes enhanced UE monitoring as mandatory Day-1 features, including flexible CORESET placement beyond the first 3 symbols and support for more than one CORESET in addition to CORESET#0. They also propose simplifications to the 5G monitoring capabilities framework by reviewing whether limits on maximum DCI sizes and CCEs are still needed, and suggest that baseline blind decoding limits from 5G could be increased given evolved UE processing capabilities.
Key proposals
- Proposal 1 (Sec 3.1): Apply the generic principle of PDCCH blind decoding for 6G at least for single-stage DCI and for the 1st stage of two-stage DCI.
- Proposal 3 (Sec 4.1): 6G to retain the flexible NR PDCCH operation in terms of DL control time-frequency structure enabled by flexible search space and CORESET configurations.
- Proposal 6 (Sec 4.1): RAN1 to assume that CORESET can have a duration of 1, 2, or, 3 OFDM symbols and discuss further the motivation for a longer CORESET durations.
- Proposal 10 (Sec 4.2): Apply QPSK modulation at least for single-stage DCI, and if two-stage DCI would be considered, also for the 1st stage DCI.
- Proposal 11 (Sec 4.2): Apply transparent DM-RS based PDCCH precoding for 6G.
- Proposal 12 (Sec 4.2): 6G to apply possibility for configurable DM-RS scrambling ID to enable inherent MU-MIMO operation.
- Proposal 13 (Sec 4.2): 6G should consider studying DM-RS design to maximize the opportunities for coexistence between CORESET#0 and dedicated CORESETs.
- Proposal 14 (Sec 4.3): 6GR to support PDCCH repetitions for increased reliability. Details are FFS.
- Proposal 15 (Sec 5.1): Apply the framework of using search spaces associated with the CORESET to enable time-domain flexibility in adapting the control resources and blind decoding of PDCCH candidates.
- Proposal 18 (Sec 5.1): 6G should consider increasing the maximum number of configured search spaces with associated CORESETs to provide enough flexibility and for MRSS support.
- Proposal 19 (Sec 5.1): 6G should consider more flexibility in the configuration of DCIs in a search space, e.g., allowing separation of a pair of DCI formats for PDSCH/PUSCH scheduling to different search spaces.
- Proposal 20 (Sec 5.2): 6GR to apply the concept of aggregation levels (ALs) for PDCCH link adaptation.
- Proposal 21 (Sec 5.3): 6G should consider enhanced UE monitoring capabilities, such as flexible CORESET placement in a slot and support of more than one CORESET in addition to CORESET#0, as mandatory UE baseline features for 6G Day-1.
- Proposal 22 (Sec 5.3): 6GR to consider simplifications to the 5G UE PDCCH monitoring capabilities framework, including reviewing the need for limiting the maximum number of DCI sizes and CCEs.
- Proposal 23 (Sec 5.3): 6GR to take 5G blind decoding limits as a starting point and discuss whether the baseline limits could be increased.