R1-2600035
discussion
On downlink transmission schemes for downlink control channels in 6GR
From Nokia
Summary
This document contains 7 observations and 16 proposals on downlink control channel design for 6G Radio (6GR). Nokia's overall position is that the 5G NR PDCCH structure (CORESET, CCE, REG, blind decoding, search spaces, aggregation levels, QPSK with DM-RS) is sufficiently flexible and should be retained as the baseline for 6GR, with targeted enhancements for Multi‑Radio Spectrum Sharing (MRSS), complexity reduction, and UE power saving.
Position
Nokia 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 MRSS operation. They propose 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. Nokia 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. They propose 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, Nokia proposes baselining C-DRX and prioritizing SSSG switching over PDCCH skipping due to its wider adaptation variety.
Key proposals
- Proposal 1 (Sec 3.2): Using generic principle of PDCCH blind decoding from 5G is necessary to offer flexibility required for 6G.
- Proposal 2 (Sec 4.1): Retain the concepts of CORESET, CCE and REG as baseline building blocks for 6GR TX schemes for DL control.
- Proposal 6 (Sec 4.2): Reuse basic principles of applying QPSK modulation and transparent DM-RS based precoding for 6G.
- Proposal 8 (Sec 4.2): 6G should consider studying DM-RS design to maximize the opportunities for coexistence between CORESET#0 and dedicated CORESETs.
- Proposal 9 (Sec 4.3.1): Reuse the framework of using search spaces associated with the CORESET to enable flexibility in adapting the control resources and blind decoding of PDCCH candidates.
- Proposal 12 (Sec 4.3.1): 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 13 (Sec 4.3.2): 6GR to retain the concept of aggregation levels (ALs) for PDCCH link adaptation.
- Proposal 14 (Sec 4.3.3): 6G should consider enhanced UE monitoring capabilities, such as flexible CORESET placement in a slot and support of more than one CORESET, as mandatory UE baseline features for 6G Day-1.
- Proposal 15 (Sec 4.3.3): 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 16 (Sec 4.3.4): 6GR to support methods to reduce unnecessary PDCCH monitoring to enable UE power saving.
- Proposal 3 (Sec 4.1): 6G to retain the flexible NR PDCCH operation in terms of DL control time-frequency structure (defined by flexible search space and CORESET configuration) as well as the definition and size of CCEs and REGs to enable efficient DL control operation and MRSS.
- Proposal 5 (Sec 4.1): 6GR Day-1 design should consider alignment between CORESET0 and other CORESETs with the RB offset specified in Rel16.
- Proposal 7 (Sec 4.2): 6G to retain possibility for configurable DM-RS scrambling ID to enable inherent MU-MIMO operation.
- Proposal 10 (Sec 4.3.1): Reuse framework of defining common and user-specific search spaces.
- Proposal 11 (Sec 4.3.1): 6G should consider increasing the maximum number of configured search spaces with associated CORESETs to provide enough flexibility and for MRSS support.