R1-2600115
discussion
Discussion on downlink transmission scheme(s) for downlink control channels for 6GR
From Spreadtrum
Summary
This document contains 78 proposals and 18 observations discussing 6GR PDCCH design, where Spreadtrum identifies NR limitations including insufficient CORESET duration (max 3 symbols), overlapping monitoring adaptation mechanisms, and three monitoring capability types increasing complexity, while proposing NR-based baseline with enhancements for coverage, simplified monitoring, and unified frameworks.
Position
Spreadtrum proposes inheriting NR PDCCH physical structure (CCE/REG/REG bundle framework, ALs 1/2/4/8/16, time-first REG mapping, hash-based search space) as baseline for 6GR. They prefer one port precoder-cycling between REG bundles for transmit diversity over SFBC, arguing comparable performance with simpler implementation. They propose studying longer CORESET duration (4/6/12 symbols) to address capacity in hotspot areas and coverage for narrow-bandwidth UEs. They require a unified framework for sub-slot/slot/slot group-level PDCCH monitoring to replace three separate monitoring capability types from NR, reducing UE and gNB implementation complexity. They propose studying a harmonized PDCCH monitoring adaptation mechanism, criticizing NR's overlapping functionalities (PDCCH skipping, SSSG switching, DCI format 2_6, PEI, LP-WUS) and suggesting alternatives like two-stage DCI or dynamic candidate indication by LP-WUS.
Key proposals
- Proposal 1 (Sec 2.1): High transmission robustness
- Proposal 2 (Sec 2.1): Enhancements for the PDCCH capacity and coverage
- Proposal 3 (Sec 2.1): Harmonized and simplified PDCCH blind complexity detection scheme
- Proposal 7 (Sec 2.2.1): For 6GR PDCCH transmit diversity scheme, consider one port precoder-cycling between REG bundles as starting point
- Proposal 9 (Sec 2.2.2): For 6GR PDCCH DMRS design, following aspects can be considered as starting point: Length-31 Gold sequence, DMRS density 1/4 at RE#1/5/9, precoder granularity same as REG-bundle or contiguous RBs
- Proposal 14 (Sec 2.3.1): NR PDCCH physical structure can be used as a starting point for 6GR
- Proposal 23 (Sec 2.3.2): Study CORESET spanning multiple carriers in SCMC scenario
- Proposal 24 (Sec 2.3.2): Study longer CORESET duration in 6GR, e.g., 4/6/12 symbols
- Proposal 25 (Sec 2.4.1): The definition and configuration of search space set in NR can be considered as starting point for 6GR
- Proposal 32 (Sec 2.4.2.1): A unified framework for sub-slot/ slot/ slot group-level UE PDCCH monitoring can be studied
- Proposal 36 (Sec 2.4.3): Study harmonized and simplified mechanism to reduce unnecessary PDCCH monitoring in 6G, based on or extended from NR time domain PDCCH monitoring adaptation techniques
- Proposal 37 (Sec 2.4.4): Study reasonable feedback mechanism for PDCCH detection
- Proposal 38 (Sec 2.5): Multi-DCI/ single-DCI based scheme can be a starting point for M-TRP transmission
- Proposal 39 (Sec 2.6): Study CORESET sharing between 5G/6GR to reduce overhead and improve spectrum efficiency